0000950170-23-006839 | 10-K | XBRL Viewer

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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2022	Mar. 01, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	CULLINAN ONCOLOGY, INC.
Current Fiscal Year End Date	--12-31
Document Annual Report	true
Document Transition Report	false
Entity Central Index Key	0001789972
Entity File Number	001-39856
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3879991
Entity Address, Address Line One	One Main Street
Entity Address, Address Line Two	Suite 1350
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	410-4650
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	CGEM
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 375.6
Entity Common Stock, Shares Outstanding		39,327,298
Auditor Name	KPMG LLP
Auditor Location	Boston, Massachusetts
Auditor Firm ID	185

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 156,152	$ 59,774
Short-term investments	311,140	230,692
Prepaid expenses and other current assets	7,180	6,098
Total current assets	474,472	296,564
Property and equipment, net	1,174	77
Operating lease right-of-use assets	4,130	0
Other assets	459	147
Long-term investments	80,882	140,397
Total assets	561,117	437,185
Current liabilities:
Accounts payable	2,660	3,169
Accrued expenses and other current liabilities	14,135	8,577
Income tax payable	4,282
Operating lease liabilities, current	1,421
Total current liabilities	22,498	11,746
Long-term liabilities:
Lease liabilities, non-current	3,590
Deferred rent	0	65
Total liabilities	26,088	11,811
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2022 and 2021; no shares issued and outstanding as of December 31, 2022 and 2021, respectively.
Common stock, $0.0001 par value, 150,000,000 shares authorized as of December 31, 2022 and 2021; 45,796,449 and 44,292,102 shares issued and outstanding as of December 31, 2022 and 2021, respectively.	5	4
Additional paid-in capital	585,320	584,714
Accumulated other comprehensive loss	(2,601)	(838)
Accumulated deficit	(47,695)	(158,909)
Total Cullinan stockholders' equity	535,029	424,971
Noncontrolling interests	0	403
Total stockholders' equity	535,029	425,374
Total liabilities and stockholders' equity	$ 561,117	$ 437,185

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	45,796,449	44,292,102
Common stock, shares outstanding	45,796,449	44,292,102

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue	$ 0	$ 18,943
Type of revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 91,948	$ 57,751
General and administrative	40,189	29,146
Total operating expenses	132,137	86,897
Gain on sale of Cullinan Pearl	276,785	0
Income (loss) from operations	144,648	(67,954)
Other income (expense):
Interest income	6,611	477
Other income (expense), net	57	(8)
Net income (loss) before income taxes	151,316	(67,485)
Income tax expense	42,121	0
Net income (loss)	109,195	(67,485)
Net loss attributable to noncontrolling interest	(2,019)	(1,915)
Net income (loss) attributable to common stockholders of Cullinan	111,214	(65,570)
Comprehensive income (loss):
Net income (loss)	109,195	(67,485)
Unrealized loss on investments	(1,763)	(836)
Comprehensive income (loss)	107,432	(68,321)
Comprehensive loss attributable to noncontrolling interest	(2,019)	(1,915)
Comprehensive income (loss) attributable to Cullinan	$ 109,451	$ (66,406)
Earnings (net loss) per share:
Earnings Per Share, Basic	$ 2.46	$ (1.52)
Earnings Per Share, Diluted	$ 2.38	$ (1.52)
Weighted-average shares used in computing earnings (net loss) per share:
Weighted Average Number of Shares Outstanding, Basic	45,164	43,077
Weighted Average Number of Shares Outstanding, Diluted	46,640	43,077

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Noncontrolling Interests in Subsidiaries	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balances at Dec. 31, 2020	$ 200,315	$ 3	$ 1,305	$ 292,348	$ (2)	$ (93,339)
Balances, shares at Dec. 31, 2020		29,831,125
Initial public offering net of issuance costs of $22,870	264,516	$ 1		264,515
Initial public offering net of issuance costs of $22,870, shares		13,685,000
Net issuance of common stock under equity-based compensation plans	3,281			3,281
Net issuance of common stock under equity-based compensation plans, (In Shares)		763,000
Contributions from noncontrolling interests	990		990
Issuance of common stock under employee stock purchase plan	218			218
Issuance of common stock under employee stock purchase plan (In Share)		12,977
Acquisition of noncontrolling interests	0
Equity-based compensation	$ 24,375		23	24,352
Stock option exercises ,shares	763,000
Unrealized gain (loss) on investments	$ (836)				(836)
Net loss	(67,485)		(1,915)			(65,570)
Balances at Dec. 31, 2021	425,374	$ 4	403	584,714	(838)	(158,909)
Balances, shares at Dec. 31, 2021		44,292,102
Net issuance of common stock under equity-based compensation plans	6,020	$ 1		6,019
Net issuance of common stock under equity-based compensation plans, (In Shares)		1,504,347
Contributions from noncontrolling interests	1,527		1,527
Acquisition of noncontrolling interests	(33,281)		(575)	(32,706)
Equity-based compensation	$ 27,957		664	27,293
Stock option exercises ,shares	1,523,000
Unrealized gain (loss) on investments	$ (1,763)				(1,763)
Net loss	109,195		(2,019)			111,214
Balances at Dec. 31, 2022	$ 535,029	$ 5		$ 585,320	$ (2,601)	$ (47,695)
Balances, shares at Dec. 31, 2022		45,796,449

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Statement of Stockholders' Equity [Abstract]
Initial public offering, net of issuance costs	$ 22,870

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net loss	$ 109,195	$ (67,485)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain on sale of Cullinan Pearl	(276,785)	0
Equity-based compensation expense	27,957	24,375
Amortization/Accretion on Marketable Securities	1,294	3,098
Non cash contributions from noncontrolling interests	374	67
Realized loss on marketable securities	109	0
Depreciation and amortization	93	53
Gain on disposal of fixed assets	(77)	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,130)	(3,269)
Accounts payable	(509)	(4,835)
Accrued expenses and other liabilities	8,533	4,563
Income tax payable	4,282	0
Net cash used in operating activities	(126,664)	(43,433)
Investing activities:
Purchase of Marketable securities	(377,916)	(525,813)
Sales and maturities of marketable securities	352,933	192,038
Sale of Cullinan Pearl, net of cash transferred	275,000	0
Purchases of property and equipment	(1,133)	0
Proceeds from sale of property and equipment	91	0
Net cash used in investing activities	248,975	(333,775)
Financing activities:
Acquisition of noncontrolling interests	(33,281)	0
Net issuance of common stock under equity-based compensation plans	6,020	3,281
Issuance of convertible notes	2,375	0
Repayment of convertible note	(2,200)	0
Contributions from noncontrolling interests	1,153	923
Proceeds from initial public offering	0	267,268
Payment of deferred offering costs	0	(2,688)
Net cash provided by financing activities	(25,933)	268,784
Net decrease in cash and cash equivalents	96,378	(108,424)
Cash and cash equivalents at beginning of year	59,774	168,198
Cash and cash equivalents at end of year	156,152	59,774
Noncash financing activities
Deferred offering costs paid in the prior year	0	65
Purchases of property and equipment	71	0
Cash paid for income taxes	37,801	0
Cash paid for interest	$ 32	$ 0

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Statement of Cash Flows [Abstract]
Cash Transferred with Sale	$ 2,898

Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of Business and Basis of Presentation

(1)

Nature of Business and Basis of Presentation

Organization

Cullinan Oncology, Inc., together with its consolidated subsidiaries ("Cullinan" or "the Company"), is a clinical-stage biopharmaceutical company focused on modality-agnostic targeted oncology. Cullinan’s predecessor company, Cullinan Pharmaceuticals, LLC was formed in September 2016 and was subsequently renamed Cullinan Oncology, LLC ("LLC") in November 2017. The LLC’s wholly-owned subsidiary, Cullinan Management, Inc. ("Management"), was formed in September 2016 and became the surviving entity in a reverse merger with the LLC in January 2021. In February 2021, Management changed its name to Cullinan Oncology, Inc.

The Company completed the sale of its entire equity interest in its partially-owned subsidiary, Cullinan Pearl Corp. ("Cullinan Pearl"), to Taiho Pharmaceutical Co., Ltd (“Taiho”) in June 2022. Refer to Note 3 for additional details relating to the transaction. The sale of the Company's equity interest in Cullinan Pearl did not meet the criteria to be reported as a discontinued operation under the accounting principles generally accepted in the United States ("U.S. GAAP"). Therefore, prior period consolidated financial statements and disclosures have not been retroactively restated to reflect the impact of the sale of the Company’s equity interest in Cullinan Pearl.

Reorganization, Reverse Stock Split and Initial Public Offering

In January 2021, the Company completed its initial public offering ("IPO") in which it issued and sold 13,685,000 shares of its common stock, including 1,785,000 shares sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price to the public of $21.00 per share. The shares began trading on the Nasdaq Global Select Market on January 8, 2021 under the symbol “CGEM”. The net proceeds received by the Company from the offering were $264.5 million, after deducting underwriting discounts, commissions and other offering expenses.

Immediately prior to the effectiveness of the Company’s registration statement, the Company completed its reorganization, whereby the LLC merged with and into Management and Management was the surviving entity (the "Reorganization"). Management was the registrant in the IPO.

Liquidity

The Company has incurred operating losses, with the exception of the one-time gain on the sale of Cullinan Pearl in 2022, and negative cash flows from operations since its inception and expects to continue to generate operating losses for the foreseeable future. The Company’s ultimate success depends on the outcome of its research and development activities as well as the ability to commercialize the Company’s product candidates. The Company is subject to a number of risks including, but not limited to, the need to obtain adequate additional funding for the ongoing and planned clinical development of its product candidates. Due to the numerous risks and uncertainties associated with pharmaceutical products and development, the Company is unable to accurately predict the timing or amount of funds required to complete development of its product candidates, and costs could exceed the Company’s expectations for a number of reasons, including reasons beyond the Company’s control.

In June 2022, the Company completed the sale of the Company’s equity interest in its partially-owned subsidiary, Cullinan Pearl, to Taiho for an upfront payment of $275.0 million. Refer to Note 3 for additional details relating to the transaction.

Since inception, the Company has funded its operations primarily through the sale of equity securities and from licensing or selling the rights to its product candidates. The Company expects that its cash, cash equivalents and short-term investments of $467.3 million and long-term investments and interest receivable of $82.8 million as of December 31, 2022, will be sufficient to fund its operating expenses and capital expenditure requirements through the next twelve months from the date of issuance of these consolidated financial statements.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

(2)

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements of the Company have been prepared in conformity with U.S. GAAP and in accordance with applicable rules and regulations of the Securities and Exchange Commission ("SEC") for financial reporting and include accounts of the Company and its consolidated subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.

Principles of Consolidation

The Company consolidates entities in which it has a controlling financial interest. The Company evaluates each of its subsidiaries to determine whether the entity represents a variable interest entity ("VIE") for which consolidation should be evaluated under the VIE model, or alternatively, if the entity is a voting interest entity, for which consolidation should be evaluated using the voting interest model ("VOE"). The Company concluded that none of its subsidiaries is a VIE and has consolidated each subsidiary under the VOE. Under the VOE, the Company consolidates the entity if it determines 1) that it directly, or indirectly, has greater than 50% of the voting shares or other equity holders do not have substantive voting, participation, or liquidation rights, or 2) when the company has a controlling financial interest through its control of the board of directors, and the significant decisions of the entity are made at the board level.

The Company had investments in the following partially-owned subsidiaries during 2022 and 2021:


Consolidated Entities	Relationship as of December 31, 2022	Date Control First Acquired
Cullinan Pearl Corp.	Divested	November 2018
Cullinan Amber Corp.	Partially-owned Subsidiary	December 2019
Cullinan Florentine Corp.	Partially-owned Subsidiary	December 2019
Cullinan Mica Corp.	Partially-owned Subsidiary	May 2020

Use of Estimates

The preparation of the Company’s consolidated financial statements and accompanying notes in conformity with U.S. GAAP requires the Company’s management to make estimates and judgments that affect the amounts reported in the financial statements. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to prepaid and accrued research and development expenses and the fair value of royalty transfer agreements. Management's estimates could change period to period based on changes in facts and circumstances. The Company’s management bases its estimates on historical experience and on other relevant assumptions that are believed to be reasonable. Actual results may differ materially from these estimates.

Segments

The Company has determined that its Chief Executive Officer is the Chief Operating Decision Maker ("CODM"). The Company operates and manages the business as one reporting and one operating segment, which is the business of developing early-stage cancer therapeutics. The Company’s CODM reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s assets are located in the U.S.

Concentration of Risk

The Company had no significant concentration of credit risk as of December 31, 2022. Cash and cash equivalents are primarily maintained with two financial institutions in the U.S. as of December 31, 2022. Deposits at banks may exceed the insurance provided on such deposits. These deposits may be redeemed upon demand, and therefore, bear minimal risk. Under our investment policy, the Company limits amounts invested in such securities by investment type, credit rating, maturity, industry group and issuer. The goals of our investment policy are (i) safety and preservation of principal and diversification of risk and (ii) liquidity of investments sufficient to meet cash flow requirements.

The Company is subject to certain risks and uncertainties and believes that changes in any of the following areas could have a material adverse effect on future financial position or results of operations: ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, product candidates; performance of third-party clinical research organizations and manufacturers upon which the Company relies; protection of the Company’s intellectual property; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; and the Company’s ability to attract and retain employees necessary to support its growth.

The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for drug substance and drug products related to these programs. These programs could be adversely affected by a significant interruption in the supply.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the time of purchase to be cash equivalents. As of December 31, 2022 and 2021, cash equivalents consist of government-backed money market funds.

Investments

The Company generally holds investments in marketable securities. Investments not classified as cash equivalents with maturities of less than twelve months are classified as short-term investments in the consolidated balance sheets. Investments with maturities greater than twelve months for which the Company has the intent and ability to hold the investment for greater than twelve months are classified as long-term investments in the consolidated balance sheets.

The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in interest income. Interest and dividends are also included in interest income. Interest receivable is included in prepaid expenses and other current assets on the consolidated balance sheets and represents accrued and unpaid interest on the Company's marketable securities. The Company periodically reviews its marketable securities for impairment and adjusts these investments to their fair value when a decline in market value is deemed to be other than temporary. Declines in fair value judged to be other-than-temporary on marketable securities, if any, are included in other income (expense), net.

Fair Value of Financial Instruments

The Company has certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements. The three levels of the fair value hierarchy are described below:

Level 1—Unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access;

Level 2—Quoted prices for similar assets and liabilities in active markets or other market-observable inputs such as interest rates, yield curves and foreign currency spot rates; and

Level 3—Pricing or valuations that require inputs that are both significant to the fair value measurement and unobservable.

There were no transfers of financial assets or liabilities measured at fair value between Level 1 and Level 2, and there were no Level 3 investments during 2022 or 2021.

The Company's financial assets recorded at fair value consist of short-term investments and long-term investments. The fair value of the Company’s short-term and long-term investments is primarily determined using market quotations or prices obtained from independent pricing sources.

As of December 31, 2022 and 2021, the fair values of cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities approximated their carrying values due to the short-term nature of these instruments.

Property and Equipment, net

Property and equipment is stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


Asset Class		Estimated Useful Life
Office furniture and equipment		5 years
Leasehold improvements		Shorter of the useful life of the asset or the lease term

Maintenance and repairs that do not improve or extend the life of the assets are expensed when incurred. Upon disposal or retirement of assets, the cost and accumulated depreciation and amortization are removed from the consolidated balance sheets and any resulting gain or loss is reflected in the consolidated statements of operations and comprehensive income (loss).

Leases

The Company determines if an arrangement is a lease at inception. A contract is or contains a lease if the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The Company classifies leases at the lease commencement date as operating or finance leases and records a right-of-use asset ("ROU") and a lease liability on the consolidated balance sheets for all leases with an initial lease term of greater than 12 months. Leases with an initial term of 12 months or less are not recorded in the balance sheet, and payments are recognized as expense on a straight-line basis over the lease term.

The Company enters into contracts that contain both lease and non-lease components. Non-lease components may include maintenance, utilities and other operating costs. The Company combines the lease and non-lease components of fixed costs in its lease arrangements as a single lease component. Variable costs, such as utilities or maintenance costs, are not included in the measurement of ROU assets and lease liabilities but rather are expensed when the event determining the amount of variable consideration to be paid occurs.

Operating lease assets and liabilities are recognized at the lease commencement date based on the present value of the lease payments over the lease term using the discount rate implicit in the lease. If the discount rate is not readily determinable, the Company utilizes an estimate of its incremental borrowing rate based upon the available information at the lease commencement date. Operating lease assets are further adjusted for prepaid or accrued lease payments. Operating lease payments are expensed using the straight-line method as an operating expense over the lease term. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option.

Impairment of Long-Lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount or the fair value less costs to sell.

Deferred Offering Costs

The Company capitalizes costs that are directly associated with in-process equity financings until such financings are consummated at which time such costs are recorded against the gross proceeds of the offering. Should the in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive income (loss). The Company incurred $2.7 million of deferred offering costs in 2020 and recorded such amounts against the gross proceeds of the Company’s IPO within the statements of stockholders’ equity for 2021.

Noncontrolling Interests

Noncontrolling interests represent third-party interests in the Company’s partially-owned subsidiaries. The Company determines the amount of the noncontrolling interests in the net assets of the Company’s partially-owned subsidiaries at each balance sheet date using the hypothetical liquidation at book value ("HLBV") method. Under the HLBV method, the amounts reported as noncontrolling interests in the consolidated balance sheets represent the amounts the third parties would hypothetically receive at each balance sheet date under the liquidation provisions of the partially-owned subsidiaries, assuming the net assets of the partially-owned subsidiaries were liquidated at their recorded amounts determined in accordance with U.S. GAAP and distributed to the owners of the partially-owned subsidiaries. Net income (loss) attributable to noncontrolling interests on the consolidated statements of operations and comprehensive income (loss) is determined as the difference in the noncontrolling interest in the consolidated balance sheets between the start and end of each reporting period, after taking into account any capital transactions between the partially-owned subsidiaries and the third parties.

Revenue Recognition

Revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps: 1) identify the customer contract; 2) identify the contract’s performance obligations; 3) determine the transaction price; 4) allocate the transaction price to the performance obligations; and 5) recognize revenue when or as a performance obligation is satisfied.

Licensing arrangements are analyzed to determine whether the promised goods or services, which could include licenses and research and development materials and services, are distinct or whether they must be accounted for as part of a combined performance obligation.

The transaction price is determined based on the consideration to which the Company will be entitled. The transaction price may include fixed amounts, variable amounts, or both. The Company reevaluates the probability of realizing such variable consideration and any related constraints at each reporting period. The Company includes variable consideration in the transaction price to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur.

The Company allocates the transaction price based on the estimated standalone selling price of the underlying performance obligations. The Company must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the standalone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs to complete the respective performance obligation. The Company also utilizes judgement in assessing whether or not variable consideration is constrained or if it can be allocated specifically to one or more performance obligations in the arrangement.

When a performance obligation is satisfied, revenue is recognized for the amount of the transaction price allocated to that performance obligation on a relative standalone selling price basis, which excludes estimates of variable consideration that are constrained. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement.

For performance obligations consisting of licenses and other promises, the Company utilizes judgment to assess whether the combined performance obligation is satisfied over time or at a point in time and the recognition pattern for the portion of the transaction price allocated to the performance obligation.

Research and Development Expenses

Research and development costs are expensed as incurred. Research and development expenses consist primarily of employee compensation costs and amounts incurred with third parties for the provision of services for product candidate development, clinical and preclinical development and related supply and manufacturing costs, and regulatory compliance costs. At the end of the reporting period, the Company compares payments made to third-party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs.

Costs incurred to obtain licenses are recognized as research and development expense as incurred if the technology licensed has no alternative future use. Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are received or services are performed.

The Company has entered into various research and development related contracts with parties both inside and outside of the U.S. The payments related to these agreements are recorded as research and development expenses as incurred. The Company records accrued liabilities for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses in the consolidated statements of operations and comprehensive income (loss).

Equity-Based Compensation

Equity-based compensation is measured at the grant date for all equity-based awards made to employees and non-employees using the fair value of the awards and is recognized as expense over the requisite service period, which is generally the vesting period. Forfeitures are recognized as they occur.

The Company grants service-based RSUs, market-based RSUs and stock options to employees and non-employees. The fair value of service-based restricted stock units ("RSUs") is the closing market price of the Company's common stock on the grant date. The fair value of market-based RSUs is measured on the grant date using a Monte Carlo simulation model. The Company estimated the fair value of the stock options using the Black-Scholes option pricing model, which requires the input of objective and subjective assumptions. Certain assumptions used, including the fair value of the Company’s common stock prior to the IPO and stock price volatility, represent management’s estimates and involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and management uses different assumptions, equity-based compensation expense could be materially different for future awards.

The Company classifies equity-based compensation in its consolidated statements of operations and comprehensive income (loss) in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Income Taxes

The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained. Recognized income tax positions are measured at the largest amount of benefit that is greater than fifty percent likely to be realized upon settlement. Changes in measurement are reflect in the period in which the change in judgment occurs.

Comprehensive Income (Loss)

Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from nonowner sources. The Company’s only element of other comprehensive loss is unrealized gains and losses on investments.

Earnings (Net Loss) per Share

Basic earnings (net loss) per share is determined by dividing earnings (net loss) attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. Diluted earnings (net loss) per share is determined by dividing earnings (net loss) attributable to common stockholders by the weighted-average number of common shares outstanding during the period, adjusted for the dilutive effect of shares of common stock equivalents as determined using the treasury stock method.

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.

The JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies. The Company expects to use the extended transition period for any other new or revised accounting standards during the period in which it remains an emerging growth company.

Recently Adopted Accounting Pronouncements

On January 1, 2022, the Company adopted a new standard on leases (as amended, "ASC 842"), which requires lessees to recognize a lease liability and a ROU asset on the balance sheet for all leases, except certain short-term leases. In connection with its implementation of ASC 842, the Company adopted a package of three practical expedients, allowing it to carry forward its previous lease classification and embedded lease evaluations and not to reassess initial direct costs as of the date of adoption. The Company also adopted a practical expedient that allows it to combine lease and non-lease components for its real estate leases.

The Company’s existing lease obligations relating to a single corporate location is subject to the new standard and resulted in operating lease liabilities and ROU assets being recorded on the Company’s consolidated balance sheets on the implementation date. The existing lease obligation is classified as an operating lease.

The below table details the balance sheet adjustments recorded on January 1, 2022 in connection with the Company’s adoption of ASC 842 (in thousands):


	December 31, 2021					January 1, 2022
	As Reported under ASC 840		ASC 842 Adjustments			As Reported Under ASC 842
Assets
Operating lease right-of-use asset	$	—	$	1,311		$	1,311
Liabilities
Current portion of operating lease liabilities	$	—	$	505		$	505
Deferred rent	$	65	$	(65	)	$	—
Noncurrent portion of operating lease liabilities	$	—	$	871		$	871

In December 2019, the Financial Accounting Standards Board issued ASU No. 2019-12, which is intended to simplify the accounting for income taxes. The Company adopted this standard on January 1, 2022. The adoption of this standard did not have a material impact on the Company's consolidated financial position and consolidated results of operations.

Sale of Cullinan Pearl and Co-Development Agreement with Taiho

12 Months Ended

Dec. 31, 2022

Debt Securities, Available-for-Sale [Abstract]

Sale of Cullinan Pearl and Co-Development Agreement with Taiho

(3)

Sale of Cullinan Pearl and Co-Development Agreement with Taiho

In June 2022, the Company sold its equity interest in its partially-owned subsidiary, Cullinan Pearl, which had worldwide rights to zipalertinib (CLN-081/TAS6417), excluding Japan and mainland China, Hong Kong, Macau and Taiwan ("Greater China”), to Taiho for an upfront payment of $275.0 million, with an increase to the purchase price in the amount of $2.9 million for cash held by Cullinan Pearl that was transferred with the sale. Pursuant to the share purchase agreement with Taiho, the Company is also eligible to receive up to an additional $130.0 million tied to epidermal growth factor receptor exon 20 non-small-cell lung cancer regulatory milestones.

The Company concluded the transaction was a sale of non-financial assets, which comprised mainly of intellectual property rights and related intangible assets, and that it transferred control of the non-financial assets at the closing of the sale. The Company recognized a gain on sale of Cullinan Pearl of $276.8 million within income from operations in its consolidated statements of operations and other comprehensive income (loss) for 2022. The table below sets forth the book value of the Cullinan Pearl assets and liabilities sold along with the calculation of the gain on sale based on the cash consideration received.


	(in thousands)
Book value of assets sold
Cash	$	2,898
Prepaid expenses and other current assets		619
Amounts attributable to assets sold		3,517
Book value of liabilities sold
Accrued expenses and other current liabilities		2,404
Amounts attributable to liabilities sold		2,404
Total identifiable net assets sold		1,113
Upfront consideration, inclusive of cash transferred of $2,898		277,898
Gain on sale of Cullinan Pearl	$	276,785

During 2022, Cullinan Pearl issued $2.2 million of convertible notes to an affiliate of Taiho. The Company repaid these convertible notes along with the accrued interests at the closing of the Cullinan Pearl sale.

Co-Development Agreement with Taiho

In June 2022, concurrently with the closing of the sale of the Company’s equity interest in Cullinan Pearl, the Company entered into a co-development agreement with an affiliate of Taiho, pursuant to which the Company will collaborate to develop zipalertinib and will retain the option to co-commercialize zipalertinib in the U.S. Development costs for zipalertinib incurred after the sale of the Company’s equity interest in Cullinan Pearl shall be shared equally between Taiho and the Company with each party receiving 50% of any future pre-tax profits from potential U.S. sales of zipalertinib.

The Company concluded that the co-development agreement with Taiho is a collaborative arrangement because the Company is an active participant in the development of zipalertinib. Payments made to or received from Taiho for zipalertinib development activities after the sale are recorded within research and development expenses. For 2022, costs reimbursable by Taiho and reflected as a reduction to research and development expenses were $3.5 million, which had not been reimbursed by Taiho as of December 31, 2022. The Company also recorded research and development expense of $2.5 million related to its share of costs incurred by Taiho, which the Company had not yet reimbursed as of December 31, 2022. The net amount of $1.0 million due from Taiho was recorded within prepaid expenses and other current assets as of December 31, 2022.

Financial Instruments

12 Months Ended

Dec. 31, 2022

Financial Instruments Pledged as Collateral [Abstract]

Financial Instruments

(4)

Financial Instruments

Investments

The Company recognized its short-term and long-term investments by security type at December 31, 2022 as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Short-term investments
Corporate notes	$	244,498	$	11	$	(1,743	)	$	242,766
Asset-backed securities		16,625		—		(15	)		16,610
Commercial paper		18,035		3		(13	)		18,025
U.S. government notes		34,029		—		(290	)		33,739
Total short-term investments		313,187		14		(2,061	)		311,140
Long-term investments
Corporate notes		81,436		18		(572	)		80,882
Total long-term investments		81,436		18		(572	)		80,882
Total investments	$	394,623	$	32	$	(2,633	)	$	392,022

The Company recognized its short-term and long-term investments by security type at December 31, 2021 as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Short-term investments
Corporate notes	$	98,642	$	—	$	(95	)	$	98,547
Commercial paper		114,174		—		(27	)		114,147
U.S. government notes		18,033		—		(35	)		17,998
Total short-term investments		230,849		—		(157	)		230,692
Long-term investments
Corporate notes		117,868		—		(596	)		117,272
Asset-backed securities		3,044		—		(8	)		3,036
U.S. government notes		20,166		—		(77	)		20,089
Total long-term investments		141,078		—		(681	)		140,397
Total investments	$	371,927	$	—	$	(838	)	$	371,089

Fair Value of Financial Instruments

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2022:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Short-term investments
Corporate notes	$	—	$	242,766	$	—	$	242,766
Asset-backed securities		—		16,610		—		16,610
Commercial paper		—		18,025				18,025
U.S. government notes		—		33,739				33,739
Total short-term investments		—		311,140		—		311,140
Long-term investments
Corporate notes		—		80,882		—		80,882
Total long-term investments		—		80,882		—		80,882
Total investments	$	—	$	392,022	$	—	$	392,022

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2021:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Short-term investments
Corporate notes	$	—	$	98,547	$	—	$	98,547
Commercial paper		—		114,147		—		114,147
U.S. government notes		—		17,998		—		17,998
Total short-term investments		—		230,692		—		230,692
Long-term investments
Corporate notes		—		117,272		—		117,272
Asset-backed securities		—		3,036		—		3,036
U.S. government notes		—		20,089		—		20,089
Total long-term investments		—		140,397		—		140,397
Total investments	$	—	$	371,089	$	—	$	371,089

Property and Equipment

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment, net

(5)

Property and Equipment, net

Property and equipment, net consisted of the following as of December 31, 2022 and 2021:


	December 31,
	2022			2021
	(in thousands)
Computers	$	—		$	70
Office furniture and equipment		681			134
Leasehold improvements		628			105
Total property and equipment, gross		1,309			309
Less: accumulated depreciation		(135	)		(232	)
Total property and equipment, net	$	1,174		$	77

Depreciation expense was $0.1 million and less than $0.1 million for 2022 and 2021, respectively.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2022

Accrued Expenses And Other Current Liabilities [Abstract]

Accrued Expenses and Other Current Liabilities

(6)

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following as of December 31, 2022 and 2021:


	December 31,
	2022		2021
	(in thousands)
Accrued research and development costs	$	7,486	$	5,028
Accrued bonus		4,516		2,576
Other current liabilities		1,955		973
Convertible note and accrued interest		178		—
	$	14,135	$	8,577

License and Collaboration Agreements

12 Months Ended

Dec. 31, 2022

License And Collaboration Agreements [Abstract]

License and Collaboration Agreements

(7)

License and Collaboration Agreements

Adimab

The Company has a collaboration agreement with Adimab, LLC ("Adimab") (the "Adimab Collaboration Agreement"). Pursuant to the Adimab Collaboration Agreement, the Company selected a number of biological targets against which Adimab used its proprietary platform technology to discover and/or optimize antibodies based upon mutually agreed-upon research plans. Under the Adimab Collaboration Agreement, the Company has the ability to select a specified number of additional biological targets against which Adimab will provide additional antibody discovery and optimization services.

During the research term and evaluation term for a given research program with Adimab, the Company has a non-exclusive worldwide license under Adimab’s technology to perform certain research activities and to evaluate the program antibodies to determine whether the Company wants to exercise its option to obtain a royalty-free, fully paid, non-exclusive license to exploit such antibodies and sublicense through multiple tiers (the "Adimab Option").

Under the Adimab Collaboration Agreement, the Company paid a one-time, non-creditable, non-refundable technology access fee. The Company is also required to pay an annual access fee and research funding fees in connection with Adimab’s full-time employees’ compensation for performance of Adimab’s obligations under the Adimab Collaboration Agreement. The Company is also obligated to make certain research delivery, clinical and sales milestone payments to Adimab on a program-by-program basis, subject to certain reductions and discounts.

The Company is obligated to pay certain royalty payments on a product-by-product basis at a low single-digit percentage of annual aggregate worldwide net sales. Such royalty obligations will expire on a country-by-country and product-by-product basis upon the later of (a) a certain low double-digit number of years after the first commercial sale of such product in such country and (b) the expiration of the last issued and not expired, permanently revoked, or invalid claim within a program patent covering such product.

The Company may terminate the Adimab Collaboration Agreement at any time, for any reason, upon a specified period advance written notice. The term of the Adimab Collaboration Agreement expires upon the last research program’s evaluation term in the event no Adimab Option is exercised or in the event an Adimab Option is exercised, after the royalty term expires at the later of a specified period or invalid patent coverage of the relevant product.

During 2022 and 2021, the Company recorded $0.5 million and less than $0.1 million, respectively, relating to the Adimab Collaboration Agreement within research and development expenses.

Cullinan Amber—Massachusetts Institute of Technology

Cullinan Amber Corp. ("Cullinan Amber") has an exclusive patent license agreement with Massachusetts Institute of Technology ("MIT") to develop a cancer immunotherapy product worldwide (the "MIT License Agreement"). Cullinan Amber is also responsible for paying non-refundable, creditable annual license maintenance fees in an increasing amount over a certain number of years and a fixed amount subsequent to this period of time. In addition, MIT granted to Cullinan Amber an exclusive option to amend the initially determined field to include expansion fields, and such amendment would trigger the payment to MIT of an amendment fee.

Additionally, Cullinan Amber is obligated to pay certain non-refundable, non-creditable milestone payments up to $7.0 million and up to $5.5 million to MIT upon the occurrence of certain clinical and regulatory events associated with its first and second indications, respectively, by product, and up to an additional $12.5 million upon the occurrence of cumulative net sales targets. Each milestone payment is paid one time only up to a certain payment amount. No milestones have been achieved to date under the MIT License Agreement.

Under certain conditions upon a change in control of Cullinan Amber, Cullinan Amber is required to pay a specified change in control fee and Cullinan Amber’s clinical and regulatory milestone payments shall be increased by 100%.

Furthermore, Cullinan Amber is required to pay running low single-digit royalty percentage on net sales of all licensed products for each reporting period, subject to certain offsets or reductions. The royalties due to MIT for net sales of the licensed product shall not be reduced by more than a mid double-digit percentage. Cullinan Amber is also required to share any income from sublicensing the licensed products, with the percentage to be determined by the clinical phase of the licensed product, no greater than low to mid double-digit percentages. Such royalty obligations will expire on a country-by-country and product-by-product basis upon the expiration or abandonment of all issued patents and filed patent applications within the patent rights.

During 2022 and 2021, the Company recorded $0.4 million and $0.1 million, respectively, relating to the MIT License Agreement within research and development expenses.

Cullinan Florentine—Tübingen License Agreement

Cullinan Florentine Corp. (“Cullinan Florentine”) has an exclusive license agreement (the Tübingen License Agreement) with Deutsches Krebsforschungszentrum (“DKFZ”), Eberhard Karls University of Tübingen, Faculty of Medicine (“University of Tübingen”) and Universitätsmedizin Gesellschaft für Forschung und Entwicklung mbH, Tübingen (“UFE”). Pursuant to the Tübingen License Agreement, DKFZ and University of Tübingen, collectively referred to as the Licensor, granted to Florentine an exclusive worldwide, milestone- and royalty-bearing license under certain licensed patent rights, applications, technical information and know-how, with the right to grant sublicenses through multiple tiers to research, develop, commercialize or otherwise exploit licensed products within the field.

Florentine shall pay certain non-refundable, non-creditable milestone payments to the Licensor upon the occurrence of certain clinical and regulatory events related to a licensed product. Each milestone payment is paid one time only up to a certain payment amount.

Furthermore, Cullinan Florentine is required to pay running low to mid-single digit royalty percentage on net sales of each licensed product on a country-by-country and product-by-product basis during the royalty term, subject to certain offsets or reductions. The aggregate, worldwide royalties due to Licensor for net sales of any licensed product in a calendar year shall not be reduced to an amount less than low to mid-single digit percentages. Such royalty obligations will expire on a country-by-country and product-by-product basis upon the later of (a) the expiration of the last valid claim of a patent which covers a product in such country and (b) a low double digit anniversary following the first commercial sale of a product in such country. Under certain conditions upon a first change in control, Cullinan Florentine shall pay a non-refundable, non-creditable mid-single digit percent of sale proceeds, provided, however, that such payment shall not be required following consummation of an initial public offering of Cullinan Florentine.

Either party may terminate the agreement upon a material breach by the other party or insolvency of the other party. Cullinan Florentine may terminate the DKFZ/Tübingen License Agreement for any or no reason after the first filing of an investigational new drug application or clinical trial agreement, or CTA, by providing prior written notice. Licensor may terminate the agreement by providing prior written notice, if Cullinan Florentine or any of its affiliates challenges the validity of certain patent rights. Unless earlier terminated, the Tübingen License Agreement continues perpetually. No milestones have been achieved to date under the Tübingen License Agreement. The Company did not incur license fee expense relating to this agreement during 2022 and 2021.

Cullinan MICA—Steinle Agreement

Cullinan MICA has an agreement with Dr. Alexander Steinle (the "Steinle Agreement"), who provided Cullinan MICA with services for the discovery, design and development of monoclonal antibodies that prevent the proteolytic cleavage of MICA from the surface of a cancer cell and augments killing of these cancer cells by immune cells expressing NKG2D receptors (“MICA antibodies”).

Under this agreement, Cullinan MICA shall pay certain non-refundable, non-creditable milestone payments to Dr. Steinle upon the occurrence of certain clinical and regulatory events related to a MICA antibody. Each milestone payment is paid one time only up to a certain payment amount. Cullinan MICA is also required to pay Dr. Steinle a low single digit royalty percentage on net sales of each MICA antibody on a country-by-country and product-by-product basis during the royalty term, subject to certain offsets or reductions. During 2022, the Company recorded $0.1 million related to milestone payments under the Steinle Agreement within research and development expenses.

Cullinan Pearl—Taiho & Zai Lab License Agreements

In 2020, Cullinan Pearl entered into a license agreement (the “Zai License Agreement”) with Zai Lab Shanghai Company, Ltd. (“Zai Lab”) to grant Zai Lab an exclusive royalty-bearing license to research, develop, commercialize and manufacture CLN-081 and products which contain CLN-081 in Greater China. As partial consideration of the license and rights granted to Zai Lab, Zai Lab paid Cullinan Pearl a one-time, irrevocable, nonrefundable license fee of $20.0 million.

The upfront payment received by Cullinan Pearl was subject to foreign tax withholdings. When the licensed intellectual property and technology know-how was transferred to Zai Lab in 2021, the Company recognized revenue of $18.9 million, which represented the upfront fee less the foreign tax withholdings that it did not expect to recover.

Under a revenue sharing agreement with Taiho, the Company also recorded $3.0 million within research and development expenses in 2021 upon receipt of the upfront payment for licensing the Greater China rights for zipalertinib to Zai Lab.

The Company completed the sale of its entire equity interest in Cullinan Pearl to Taiho in June 2022. Refer to Note 3 for additional details relating to the transaction.

Common Stock and Noncontrolling Interest in Subsidiaries

12 Months Ended

Dec. 31, 2022

Common Stock And Noncontrolling Interest In Subsidiaries [Abstract]

Common Stock and Noncontrolling Interest in Subsidiaries

(8)

Common Stock and Noncontrolling Interests in Subsidiaries

Common Stock

Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company. No dividends have been declared through December 31, 2022.

Noncontrolling Interests in Subsidiaries

Certain subsidiaries issue common stock in connection with licensing agreements and to employees, directors and consultants pursuant to subsidiary equity incentive plans. The holders of subsidiary common stock are entitled to one vote per share. The holders of subsidiary common stock are entitled to receive dividends when and if declared by the subsidiaries’ board of directors and distributions in either case only after the payment of all preferential amounts required to be paid to the holders of shares of preferred stock of the respective subsidiary.

Cullinan Amber

In June 2021, the Company purchased 3.0 million shares of Series A preferred stock from Cullinan Amber, and MIT received 0.2 million shares of common stock from Cullinan Amber pursuant to the MIT License Agreement.

In June 2022, the Company purchased 6.0 million shares of Series A preferred stock from Cullinan Amber, and MIT received 0.3 million shares of common stock from Cullinan Amber pursuant to the MIT License Agreement.

In November 2022, the Company purchased 10.0 million shares of Series A preferred stock from Cullinan Amber, MIT received 0.5 million shares of common stock from Cullinan Amber pursuant to the MIT License Agreement, and a scientific advisor received 0.2 million shares of common stock from Cullinan Amber pursuant to an equity-based compensation agreement.

As of December 31, 2022, the Company held common shares and Series A preferred stock that represented 94% of Cullinan Amber's outstanding equity. As of December 31, 2022, noncontrolling interests collectively held common shares that represented 6% of Cullinan Amber's outstanding equity.

In 2022 and 2021, $0.4 million and less than $0.1 million of losses, respectively, were attributed to the noncontrolling interests of Cullinan Amber.

Cullinan Florentine

In July 2021, the Company purchased 7.5 million shares of Series B preferred stock from Cullinan Florentine Corp.("Cullinan Florentine").

In July 2022, the Company purchased 3.75 million shares of Series B preferred stock from Cullinan Florentine.

As of December 31, 2022, the Company held common shares, Series A preferred stock and Series B preferred stock that represented 96% of Cullinan Florentine's outstanding equity. As of December 31, 2022, noncontrolling interests collectively held common shares that represented 4% of Cullinan Florentine's outstanding equity.

In each of 2022 and 2021, no losses were attributed to the noncontrolling interests of Cullinan Florentine.

Cullinan MICA

In June 2021, the Company purchased 5.4 million shares of Series A senior preferred stock from Cullinan MICA Corp. ("Cullinan MICA"), and certain other existing investors purchased 0.7 million shares of Series A senior preferred stock from Cullinan MICA for $0.9 million.

In March 2022, the Company purchased 6.7 million shares of Series A senior preferred stock from Cullinan MICA, and certain other existing investors purchased 0.9 million shares of Series A senior preferred stock from Cullinan MICA for $1.2 million.

In October 2022, the Company purchased 1.5 million shares of Cullinan MICA's Series A senior preferred stock, 2.0 million shares of Cullinan MICA's Series A junior preferred stock, and 11.5 million shares of Cullinan MICA's Series A-2 junior preferred stock from two of Cullinan MICA’s other stockholders for $30.7 million.

In November 2022, the Company purchased 0.4 million shares of Cullinan MICA's common stock and 0.9 million of options for Cullinan MICA's common stock from five of Cullinan MICA’s other stockholders for $2.6 million. The Company also exercised its options to purchase 0.9 million shares of common stock from Cullinan MICA.

As of December 31, 2022, the Company held 95% of the fully-diluted shares outstanding of Cullinan MICA, including 96% of its Series A preferred stock. As of December 31, 2022, noncontrolling interests collectively owned 5% of the fully-diluted shares outstanding of Cullinan MICA, including 4% of its Series A preferred stock.

In 2022 and 2021, $1.2 million and $1.1 million of losses, respectively, were attributed to the noncontrolling interests of Cullinan MICA.

Prior to being acquired by the Company, the Cullinan MICA board of directors authorized the grant of stock options to employees, directors of, consultants and other key persons to the entity. In October 2022, the Cullinan MICA board of directors authorized the acceleration of vesting for approximately 0.3 million stock options. The vesting acceleration was determined to be a cancellation of the prior award with a concurrent grant of a replacement award and was accounted for as a modification resulting in $0.6 million in incremental equity-based compensation expense. As of December 31, 2022, Cullinan MICA had approximately 0.2 million stock options held by noncontrolling interests that were outstanding and exercisable with a weighted-average exercise price of $0.22 per share.

Cullinan Pearl

In June 2022, the Company sold its equity interest in its partially-owned subsidiary, Cullinan Pearl, to Taiho. Refer to Note 3 for additional details relating to the transaction.

Prior to the sale, the Company accounted for the noncontrolling interest using the HLBV method. In 2022 and 2021, $0.3 and $0.7 million of losses, respectively, were attributed to the noncontrolling interests of Cullinan Pearl.

Equity-Based Compensation

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Equity-Based Compensation

(9)

Equity-Based Compensation

The Company recorded equity-based compensation in the following expense categories in the consolidated statements of operations and comprehensive income (loss) in 2022 and 2021:


	Year ended December 31,
	2022		2021
	(in thousands)
Research and development	$	11,018	$	8,914
General and administrative		16,939		15,461
Total equity-based compensation	$	27,957	$	24,375

2021 Stock Option and Incentive Plan

Cullinan grants equity awards in the form of stock options, restricted stock awards ("RSAs") and RSUs to its employees, directors, consultants and other key persons through the 2021 Stock Option and Incentive Plan (the "2021 Stock Plan"). The Company also grants equity awards outside of the 2021 Stock Plan in the form of stock options as an inducement material to an individual's entering into employment with the Company. As of December 31, 2022, there were approximately 2.2 million shares remaining for future grants under the 2021 Stock Plan.

The 2021 Stock Plan provides that the number of shares reserved and available for issuance under the 2021 Stock Plan will automatically increase each January 1 by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s board of directors or compensation committee. On January 1, 2023, the total number of shares available for issuance under the 2021 Stock Plan increased by approximately 2.3 million shares under this provision.

The options granted have a ten-year term and were issued with an exercise price equal to the closing market price of Cullinan’s common stock on the grant date. For equity awards with service-based vesting conditions, the Company recognizes compensation expense over the vesting period, which is generally over a four-year period. For equity awards with a market-based vesting condition, the Company recognizes compensation expense over the requisite service period. The number of shares awarded, if any, when a market-based award vests will depend on the degree of achievement of the corporate stock price metrics within the performance period of the award.

Determining fair value of options

The fair value of options is estimated using the Black-Scholes option pricing model, which takes into account inputs such as the exercise price, the value of the underlying common stock at the grant date, expected term, expected volatility, risk-free interest rate and dividend yield. The fair value of each grant of options during 2022 and 2021 were determined using the methods and assumptions discussed below:

•

The expected term of options is determined using the “simplified” method, as prescribed in the SEC Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option due to the Company’s lack of sufficient historical data.

•

The risk-free interest rate is based on implied yields available from U.S. Treasury securities with a remaining term equal to the expected term assumed at the grant date.

•

The expected volatility is based on historical volatilities of similar entities within the Company’s industry over a period of time commensurate with the expected term assumption.

•

The estimated annual dividend yield was based on the Company’s expectation of not paying dividends on its common stock in the foreseeable future.

•

The Company considered numerous objective and subjective factors in estimating the fair value of its common stock prior to the IPO, including the concluded equity value based on IPO and liquidation scenarios and their related timing and probabilities of occurrence.

For 2022 and 2021, the weighted-average grant date fair value of the options granted were $9.02 and $15.73 per share, respectively. The grant date fair value was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted-average assumptions in 2022 and 2021:


	Year Ended December 31, 2022	Year Ended December 31, 2021
Risk-free interest rate	2.65%	1.02%
Expected term (in years)	6.0	6.0
Expected volatility	79.81%	76.22%
Expected dividend yield	0.00%	0.00%

Determining fair value of market-based RSUs

The Company measures the fair value of market-based RSUs on the date of grant using a Monte Carlo simulation model. The Monte Carlo simulation requires the input of assumptions, including the Company's stock price, the volatility of its stock price, remaining term in years, expected dividend yield and risk-free rate. The Company used its own trading history to calculate the expected volatility of the market-based RSUs granted. The risk-free interest rate is determined by reference to implied yields available from U.S. Treasury securities with a remaining term equal to the expected term assumed at the grant date.

The following table details the assumptions used in the Monte Carlo simulation model used to estimate the fair value of the market-based RSUs granted during 2022:


	Year Ended December 31, 2022
Stock price	$	12.98
Volatility		82.5	%
Remaining term (years)		2.7
Risk-free rate		2.9	%
Expected dividend yield		0.0

Stock options

The following table summarizes 2022 and 2021 stock option activity (shares and aggregate intrinsic value in thousands):


	Number of Options			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2020		4,603		$	4.30
Granted		5,482		$	23.82
Exercised		(763	)	$	4.30
Forfeited		(63	)	$	17.23
Outstanding as of December 31, 2021		9,259		$	15.77
Granted		2,888		$	12.96
Exercised		(1,523	)	$	4.31
Forfeited		(1,290	)	$	13.80
Outstanding as of December 31, 2022		9,334		$	17.04		8.31	$	11,526
Exercisable as of December 31, 2022		3,706		$	15.31		7.32	$	10,060

As of December 31, 2022 and 2021, there were $66.0 million and $75.8 million in unrecognized compensation costs that are expected to be recognized over a remaining weighted-average period of 2.9 and 3.2 years, respectively.

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. The total intrinsic value of options exercised in 2022 and 2021 was $13.1 million and $10.7 million, respectively.

RSUs

In February 2022, the Company granted service-based RSUs to employees and non-employees. In June 2022, the Company entered into an agreement to grant market-based RSUs to its Chief Executive Officer. The following table summarizes the activity related to RSUs during 2022 (shares in thousands):


	Number of Shares			Weighted-Average Grant Date Fair Value
Outstanding unvested as of December 31, 2021		—		$	—
Granted(1)		502		$	13.28
Vested		(46	)	$	13.60
Forfeited		(87	)	$	13.60
Outstanding unvested as of December 31, 2022		369		$	13.16

(1)

The number granted represents the number of shares issuable upon vesting of service-based and market-based RSUs, assuming the Company achieves its corporate stock price metrics at the target achievement level.

As of December 31, 2022, there was $4.3 million in unrecognized compensation cost related to RSUs expected to be recognized over a remaining weighted-average period of 2.6 years. The total fair value of RSUs that vested during 2022 was $0.6 million.

RSAs

As part of the Reorganization in January 2021, the Company exchanged equity awards issued by the Company and its partially-owned subsidiaries prior to the Reorganization for RSAs of the Company's common stock. The following table summarizes the activity related to RSAs during 2022 and 2021 (shares in thousands) as if the prior equity awards were converted to RSAs at the earliest period presented:


	Number of Shares			Weighted-Average Grant Date Fair Value
Outstanding unvested as of December 31, 2020		364		$	2.04
Vested		(275	)	$	1.45
Outstanding unvested as of December 31, 2021		89		$	3.87
Vested		(46	)	$	3.87
Forfeited		(28	)	$	3.87
Outstanding unvested as of December 31, 2022		15		$	3.87

As of December 31, 2022 and 2021, there was $0.1 million and $0.3 million in unrecognized compensation cost related to RSAs expected to be recognized over a remaining weighted-average period of 1.0 and 1.5 years, respectively. The total fair value of RSAs that vested during 2022 and 2021 was $0.6 million and $8.5 million, respectively.

2021 Employee Stock Purchase Plan

The 2021 Employee Stock Purchase Plan (the "ESPP") authorizes the issuance of shares of common stock to participating eligible employees and provides for two six-month offering periods each year. As of December 31, 2022, there were approximately 0.8 million shares remaining for future purchases under the ESPP.

The ESPP provides that the number of shares reserved and available for issuance under the ESPP will automatically increase each January 1 by the lesser of 0.8 million shares of the Company's common stock, 1% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2023, the total number of shares available for issuance under the ESPP increased by approximately 0.5 million shares under this provision.

During each of 2022 and 2021, the Company issued less than 0.1 million shares of its common stock pursuant the ESPP.

Related Party Transactions

12 Months Ended

Dec. 31, 2022

Related Party Transactions

(10)

Related Party Transactions

Cullinan Amber, Cullinan Florentine and Cullinan MICA are each party to royalty transfer agreements with MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation (together, the "Foundations"). Under each of these respective agreements, each Foundation is entitled to receive a low single digit royalty percentage of all global net sales of any products developed by the applicable subsidiary, subject to limitations after patent expirations and on intellectual property developed after a change of control. The Company has deemed these royalty transfer agreements to be freestanding financial instruments that should be accounted for at fair value. The Company has concluded that these instruments had no value at the inception of the agreements.

Given the early-stage nature of the underlying technologies and inherent technical, regulatory and competitive risks associated with achieving approval and commercialization, the Company ascribed no value to the royalty transfer agreements as of December 31, 2022 and December 31, 2021. The Company currently does not have any applicable net sales from its products and as a result, has not paid or incurred any royalties under these agreements as of December 31, 2022. The Company will monitor these instruments for changes in fair value at each reporting date.

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Income Taxes

(11)

Income Taxes

During 2022, the Company recorded a current income tax expense of $42.1 million. The income tax expense recorded for 2022 was driven by the tax from the gain on sale of Cullinan Pearl, partially offset by the release of the valuation allowance for the utilization of current year and certain historical tax attributes against the gain from the sale. Refer to Note 3 for additional details on the sale of Cullinan Pearl. During 2021, the Company did not record a current or deferred income tax expense or benefit due to current and historical losses incurred by the Company. The Company’s net income (loss) before income taxes consists solely of domestic income and losses.

A reconciliation of the Company’s statutory income tax rate to the Company’s effective income tax rate in 2022 and 2021 is as follows:


	Year ended December 31,
	2022			2021
Federal statutory rate		21.00	%		21.00	%
State taxes, net of federal benefit		4.71	%		9.96	%
Valuation allowance		1.13	%		(32.12	)%
Other		0.97	%		1.16	%
		27.81	%		—	%

As of December 31, 2022 and 2021, the net deferred income tax asset balance related to the following:


	December 31,
	2022			2021
	(in thousands)
Deferred tax assets:
Net operating loss	$	10,531		$	31,414
Capitalized research and development		18,724			—
Capitalized organizational and start-up expenses		127			140
Licenses		461			1,875
Accrued expenses		1,977			968
Research and development credit		1,110			1,563
Equity-based compensation		12,087			8,584
Basis difference on gain on sale of Cullinan Pearl		1,805			—
Lease liability		1,345			—
Gross deferred tax assets		48,167			44,544
Valuation allowance		(46,766	)		(44,552	)
Net deferred tax asset		1,401			(8	)
Deferred tax liability
ROU asset		1,108			—
Depreciation and amortization		293			(8	)
Net deferred tax asset	$	—		$	—

The Company's net operating loss ("NOL") and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service ("IRS") and state tax authorities. Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, as well as similar state provisions, NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%. The rules generally operate by focusing on changes in ownership among stockholders considered by the rules as owning, directly or indirectly, 5% or more of the stock of a company and any change in ownership arising from new issuances of stock by the company.

As of December 31, 2022 and 2021, the Company had federal NOL carryforwards, of $42.6 million and $117.4 million, respectively, which may be available to offset future income tax liabilities. As of December 31, 2022, $36.8 million of the Company's federal NOL carryforwards can be carried forward indefinitely, and the remaining $5.8 million begins to expire in 2036. As of December 31, 2022 and 2021, the Company had state NOL carryforwards of $27.1 million and $119.0 million, respectively, which may be available to offset future income tax liabilities. As of December 31, 2022, the Company's state NOL carryforwards begin to expire in 2036.

As of December 31, 2022 and 2021, the Company had federal research and development tax credit carryforwards of $0.9 million and $1.3 million, respectively. As of December 31, 2022, the Company's federal research and development tax credit carryforwards begin to expire in 2036. As of each of December 31, 2022 and 2021, the Company had state research and development tax credit carryforwards of $0.3 million which can be carried forward indefinitely.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets, which primarily consist of capitalized research and development costs, temporary differences on equity-based compensation, and NOL carryforwards. The Company has considered its history of cumulative net losses, with the exception of the one-time gain on the sale of Cullinan Pearl in 2022, estimated future taxable income and prudent and feasible tax planning strategies and has concluded that it is more likely than not that the Company will not realize the benefits of its deferred tax assets. As a result, as of December 31, 2022, the Company has maintained a full valuation allowance against its remaining net deferred tax assets. The Company’s valuation allowance increased during 2022 and 2021 due primarily to the generation of NOLs as follows:


	Year ended December 31,
	2022		2021
	(in thousands)
Valuation allowance at beginning of year	$	44,552	$	22,642
Increases recorded to income tax provision		1,712		21,674
Increases recorded to equity		502		236
Valuation allowance at end of year	$	46,766	$	44,552

The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations for both federal taxes and the states in which the Company operates or does business in.

The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits. The Company records uncertain tax positions as liabilities and adjusts these liabilities when its judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company’s current estimate of the unrecognized tax benefit liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information is available. As of December 31, 2022 and 2021, the Company has not recorded a liability for any uncertain tax positions in its consolidated financial statements.

The Company recognizes interest and penalties related to unrecognized tax benefits on the income tax expense line in the accompanying consolidated statements of operations and comprehensive income (loss). As of December 31, 2022 and 2021, no accrued interest or penalties are included in the consolidated balance sheets.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions in the U.S. There are currently no pending tax examinations. The Company's federal and state income tax returns are generally subject to tax examinations for tax years 2016 and later. To the extent that the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the IRS and the state tax authorities to the extent utilized in a future period.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

(12)

Commitments and Contingencies

The Company enters into contracts in the normal course of business with contract research organizations, contract manufacturing organizations, and other third parties for preclinical research studies, clinical trials and testing and manufacturing services. These agreements generally include cancellation clauses.

Indemnification agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in certain cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any indemnification arrangements that could have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2022 and 2021.

Legal proceedings

The Company is not currently party to or aware of any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings.

Leases

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Leases

(13)

Leases

The Company has an operating lease for approximately 8,000 square feet of office space in a multi-tenant building in Cambridge, Massachusetts, which commenced in February 2018 and goes through June 2024 (the "Suite 520 Lease"). In August 2022, the Company entered into an additional operating lease (the "Suite 1350 Lease") for approximately 14,000 square feet of office space in a multi-tenant building in Cambridge, Massachusetts through July 2026. Lease expense consisted of operating lease costs of $1.1 million for 2022. Rent expense under the prior lease accounting standard was $0.6 million for 2021.

The following table summarizes supplemental cash flow information for 2022 (in thousands):


	Year Ended December 31, 2022
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases(1)	$	260
ROU asset obtained in exchange for an operating lease liability	$	4,931

(1)

Operating cash flows from operating leases includes cash inflow of $0.3 million reimbursed by the lessor for improvements made to the newly leased office space pursuant to the terms of the Suite 1350 lease.

The following table summarizes the weighted-average lease term and discount rate as of December 31, 2022:


	December 31, 2022
Weighted-average remaining lease term (in years)	3.2
Weighted-average discount rate		10.8	%

As the Company’s operating leases did not provide an implicit rate, the Company used its incremental borrowing rate based on the information available in determining the present value of lease payments. The Company’s incremental borrowing rate was based on the term of the lease, the economic environment and reflects the rate the Company would have had to pay to borrow on a secured basis.

The following table summarizes the Company’s future minimum lease payments under the new lease accounting standard as of December 31, 2022 (in thousands):


	December 31, 2022
2023	$	1,881
2024		1,738
2025		1,461
2026		872
Total future minimum lease payments		5,952
Less: imputed interest		(941	)
Total lease liabilities at present value	$	5,011

The following table summarizes the Company’s future minimum lease payments under the prior lease accounting standard as of December 31, 2021 (in thousands):


Years Ending December 31,	(in thousands)
2023	$	608
2024		618
2025		313
	$	1,539

Sublease Agreement

In September 2022, the Company entered into a sublease agreement through May 2024 for the Suite 520 Lease. For 2022, the Company recorded sublease income of $0.1 million within other income (expense), net. The Company expects to receive sublease payments of approximately $0.6 million in 2023 and $0.3 million in 2024. These expected sublease payments are equal to the fixed payments that the Company is required to make under its lease.

Net Loss per Share

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Net Loss per Share

(14)

Earnings (Net Loss) per Share

The following table sets forth the calculation of basic and diluted earnings (net loss) per share for 2022 and 2021:


	Year ended December 31,
	2022		2021
	(in thousands, except per share data)
Numerator:
Net income (loss) attributable to common stockholders of Cullinan	$	111,214	$	(65,570	)
Denominator:
Weighted-average common stock outstanding - basic		45,164		43,077
Dilutive effect of common stock issuable from assumed exercise of equity awards		1,476		—
Weighted-average common stock outstanding - diluted		46,640		43,077
Earnings (net loss) per share:
Basic	$	2.46	$	(1.52	)
Diluted	$	2.38	$	(1.52	)

The Company used the treasury stock method to determine the number of dilutive shares. The following table sets forth potential common shares that were excluded from the computation of the diluted earnings (net loss) per share for 2022 and 2021 because their effect would have been anti-dilutive:


	Year ended December 31,
	2022		2021
Stock options		6,842		9,259
RSAs		—		89
RSUs		25		—
ESPP		7		—
Total		6,874		9,348

Subsequent Events

12 Months Ended

Dec. 31, 2022

Subsequent Events [Abstract]

Subsequent Events

(15)

Subsequent Events

BVF common stock exchange

In January 2023, the Company entered into an exchange agreement with Biotechnology Value Fund, L.P., Biotechnology Value Fund II, L.P., Biotechnology Value Trading Fund OS LP and MSI BVF SPV, LLC (the “Stockholders”), pursuant to which the Stockholders exchanged 6.5 million shares of the Company’s common stock for 0.6 million shares of newly designated Series A convertible preferred stock, a “toothless” preferred stock, par value $0.0001 per share. Following the exchange, the Company had 39.3 million shares of common stock outstanding and 0.6 million shares of Series A preferred stock outstanding, which are convertible into 6.5 million shares of common stock.

Each share of the preferred stock will be convertible into 10 shares of Common Stock at the option of the holder at any time, subject to certain limitations, including that the holder will be prohibited from converting preferred stock into common stock if, as a result of such conversion, the holder, together with its affiliates, would beneficially own a number of shares of common stock more than 9.99% of the total common stock then issued and outstanding immediately following the conversion of such shares of preferred stock. Shares of preferred stock will generally have no voting rights, except as required by law and except that the consent of a majority of the holders of the outstanding preferred stock will be required to amend the terms of the preferred stock.

In-licensing of CLN-418

In February 2023, the Company and Harbour BioMed US Inc. (“Harbour”) entered into a license and collaboration agreement (the “Harbour License Agreement”), pursuant to which Harbour granted to the Company an exclusive license for the development, manufacturing and commercialization of HBM7008 (CLN-418) in the U.S.

Under the terms of the Harbour License Agreement, the Company paid Harbour an upfront license fee of $25 million at signing. Harbour will be eligible to receive up to $148 million in milestone payments based on the achievement of pre-specified development and regulatory milestones. Harbour is also eligible to receive up to an additional $415 million in sales-based milestones as well as tiered royalties up to the high teens on a licensed product-by-licensed product basis, as a percentage of U.S. commercial sales. In addition, under the Harbour License Agreement, Harbour will grant the Company certain intellectual property rights to enable the Company to perform its obligations and exercise its rights under the Harbour License Agreement.

Unless earlier terminated, the Harbour License Agreement will continue in effect until the expiration of the Company’s royalty obligations. The Harbour License Agreement may be terminated by either party for a material breach by the other party, subject to notice and cure provisions, or in the event of the other party’s insolvency. The Company may terminate the Harbour License Agreement for convenience by providing 90 days’ written notice to Harbour. In the Harbour License Agreement, each party made customary representations and warranties and agreed to customary covenants, including, without limitation, with respect to indemnification, for transactions of this type.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Principles of Consolidation

The Company had investments in the following partially-owned subsidiaries during 2022 and 2021:


Consolidated Entities	Relationship as of December 31, 2022	Date Control First Acquired
Cullinan Pearl Corp.	Divested	November 2018
Cullinan Amber Corp.	Partially-owned Subsidiary	December 2019
Cullinan Florentine Corp.	Partially-owned Subsidiary	December 2019
Cullinan Mica Corp.	Partially-owned Subsidiary	May 2020

Noncontrolling Interests

Comprehensive Loss

Comprehensive Income (Loss)

Segments

Concentration of Credit Risk and Other Risks and Uncertainties

Concentration of Risk

Cash and Cash Equivalents

Investments

Fair Value of Financial Instruments

Level 1—Unadjusted quoted prices for identical assets or liabilities in active markets that the Company has the ability to access;

Level 2—Quoted prices for similar assets and liabilities in active markets or other market-observable inputs such as interest rates, yield curves and foreign currency spot rates; and

Level 3—Pricing or valuations that require inputs that are both significant to the fair value measurement and unobservable.

There were no transfers of financial assets or liabilities measured at fair value between Level 1 and Level 2, and there were no Level 3 investments during 2022 or 2021.

Deferred Offering Costs

Property and Equipment

Property and Equipment, net

Property and equipment is stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


Asset Class		Estimated Useful Life
Office furniture and equipment		5 years
Leasehold improvements		Shorter of the useful life of the asset or the lease term

Leases

Impairment of Long-Lived Assets

Revenue Recognition

Research and Development Expenses

Patent Costs

Equity-Based Compensation

Income Taxes

Net Loss per Share

Earnings (Net Loss) per Share

Emerging Growth Company Status

Recently Adopted Accounting Pronouncements

The below table details the balance sheet adjustments recorded on January 1, 2022 in connection with the Company’s adoption of ASC 842 (in thousands):


	December 31, 2021					January 1, 2022
	As Reported under ASC 840		ASC 842 Adjustments			As Reported Under ASC 842
Assets
Operating lease right-of-use asset	$	—	$	1,311		$	1,311
Liabilities
Current portion of operating lease liabilities	$	—	$	505		$	505
Deferred rent	$	65	$	(65	)	$	—
Noncurrent portion of operating lease liabilities	$	—	$	871		$	871

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Summary of Estimated Useful Life of Property and Equipment

Property and equipment is stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


Asset Class		Estimated Useful Life
Office furniture and equipment		5 years
Leasehold improvements		Shorter of the useful life of the asset or the lease term

Summary of Balance sheet adjustments in connection with ASC 842

The below table details the balance sheet adjustments recorded on January 1, 2022 in connection with the Company’s adoption of ASC 842 (in thousands):


	December 31, 2021					January 1, 2022
	As Reported under ASC 840		ASC 842 Adjustments			As Reported Under ASC 842
Assets
Operating lease right-of-use asset	$	—	$	1,311		$	1,311
Liabilities
Current portion of operating lease liabilities	$	—	$	505		$	505
Deferred rent	$	65	$	(65	)	$	—
Noncurrent portion of operating lease liabilities	$	—	$	871		$	871

Sale of Cullinan Pearl and Co-Development Agreement with Taiho (Tables)

12 Months Ended

Dec. 31, 2022

Debt Securities, Available-for-Sale [Abstract]

Schedule of cash consideration received

The table below sets forth the book value of the Cullinan Pearl assets and liabilities sold along with the calculation of the gain on sale based on the cash consideration received.


	(in thousands)
Book value of assets sold
Cash	$	2,898
Prepaid expenses and other current assets		619
Amounts attributable to assets sold		3,517
Book value of liabilities sold
Accrued expenses and other current liabilities		2,404
Amounts attributable to liabilities sold		2,404
Total identifiable net assets sold		1,113
Upfront consideration, inclusive of cash transferred of $2,898		277,898
Gain on sale of Cullinan Pearl	$	276,785

Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2022

Financial Instruments Pledged as Collateral [Abstract]

Schedule of Short-term and Long-term Investment Marketable Securities by Security Type

The Company recognized its short-term and long-term investments by security type at December 31, 2022 as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Short-term investments
Corporate notes	$	244,498	$	11	$	(1,743	)	$	242,766
Asset-backed securities		16,625		—		(15	)		16,610
Commercial paper		18,035		3		(13	)		18,025
U.S. government notes		34,029		—		(290	)		33,739
Total short-term investments		313,187		14		(2,061	)		311,140
Long-term investments
Corporate notes		81,436		18		(572	)		80,882
Total long-term investments		81,436		18		(572	)		80,882
Total investments	$	394,623	$	32	$	(2,633	)	$	392,022

The Company recognized its short-term and long-term investments by security type at December 31, 2021 as follows:


	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Short-term investments
Corporate notes	$	98,642	$	—	$	(95	)	$	98,547
Commercial paper		114,174		—		(27	)		114,147
U.S. government notes		18,033		—		(35	)		17,998
Total short-term investments		230,849		—		(157	)		230,692
Long-term investments
Corporate notes		117,868		—		(596	)		117,272
Asset-backed securities		3,044		—		(8	)		3,036
U.S. government notes		20,166		—		(77	)		20,089
Total long-term investments		141,078		—		(681	)		140,397
Total investments	$	371,927	$	—	$	(838	)	$	371,089

Summary of Fair Value of Financial Assets Measured on Recurring Basis

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2022:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Short-term investments
Corporate notes	$	—	$	242,766	$	—	$	242,766
Asset-backed securities		—		16,610		—		16,610
Commercial paper		—		18,025				18,025
U.S. government notes		—		33,739				33,739
Total short-term investments		—		311,140		—		311,140
Long-term investments
Corporate notes		—		80,882		—		80,882
Total long-term investments		—		80,882		—		80,882
Total investments	$	—	$	392,022	$	—	$	392,022

The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2021:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Short-term investments
Corporate notes	$	—	$	98,547	$	—	$	98,547
Commercial paper		—		114,147		—		114,147
U.S. government notes		—		17,998		—		17,998
Total short-term investments		—		230,692		—		230,692
Long-term investments
Corporate notes		—		117,272		—		117,272
Asset-backed securities		—		3,036		—		3,036
U.S. government notes		—		20,089		—		20,089
Total long-term investments		—		140,397		—		140,397
Total investments	$	—	$	371,089	$	—	$	371,089

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment

Property and equipment, net consisted of the following as of December 31, 2022 and 2021:


	December 31,
	2022			2021
	(in thousands)
Computers	$	—		$	70
Office furniture and equipment		681			134
Leasehold improvements		628			105
Total property and equipment, gross		1,309			309
Less: accumulated depreciation		(135	)		(232	)
Total property and equipment, net	$	1,174		$	77

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Accrued Expenses And Other Current Liabilities [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following as of December 31, 2022 and 2021:


	December 31,
	2022		2021
	(in thousands)
Accrued research and development costs	$	7,486	$	5,028
Accrued bonus		4,516		2,576
Other current liabilities		1,955		973
Convertible note and accrued interest		178		—
	$	14,135	$	8,577

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Equity-based Compensation Expense Categories In Consolidated Statements of Operations and Comprehensive Loss

The Company recorded equity-based compensation in the following expense categories in the consolidated statements of operations and comprehensive income (loss) in 2022 and 2021:


	Year ended December 31,
	2022		2021
	(in thousands)
Research and development	$	11,018	$	8,914
General and administrative		16,939		15,461
Total equity-based compensation	$	27,957	$	24,375

Schedule of Assumptions Used to Estimate Fair value

The grant date fair value was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted-average assumptions in 2022 and 2021:


	Year Ended December 31, 2022	Year Ended December 31, 2021
Risk-free interest rate	2.65%	1.02%
Expected term (in years)	6.0	6.0
Expected volatility	79.81%	76.22%
Expected dividend yield	0.00%	0.00%

Summary of Stock Options Activity

The following table summarizes 2022 and 2021 stock option activity (shares and aggregate intrinsic value in thousands):


	Number of Options			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2020		4,603		$	4.30
Granted		5,482		$	23.82
Exercised		(763	)	$	4.30
Forfeited		(63	)	$	17.23
Outstanding as of December 31, 2021		9,259		$	15.77
Granted		2,888		$	12.96
Exercised		(1,523	)	$	4.31
Forfeited		(1,290	)	$	13.80
Outstanding as of December 31, 2022		9,334		$	17.04		8.31	$	11,526
Exercisable as of December 31, 2022		3,706		$	15.31		7.32	$	10,060

Summary of Activity Related to RSUs

The following table summarizes the activity related to RSUs during 2022 (shares in thousands):


	Number of Shares			Weighted-Average Grant Date Fair Value
Outstanding unvested as of December 31, 2021		—		$	—
Granted(1)		502		$	13.28
Vested		(46	)	$	13.60
Forfeited		(87	)	$	13.60
Outstanding unvested as of December 31, 2022		369		$	13.16

(1)

Summary of Activity Related to RSAs

The following table summarizes the activity related to RSAs during 2022 and 2021 (shares in thousands) as if the prior equity awards were converted to RSAs at the earliest period presented:


	Number of Shares			Weighted-Average Grant Date Fair Value
Outstanding unvested as of December 31, 2020		364		$	2.04
Vested		(275	)	$	1.45
Outstanding unvested as of December 31, 2021		89		$	3.87
Vested		(46	)	$	3.87
Forfeited		(28	)	$	3.87
Outstanding unvested as of December 31, 2022		15		$	3.87

Restricted Stock Units (RSUs) [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Schedule of Assumptions Used to Estimate Fair value

The following table details the assumptions used in the Monte Carlo simulation model used to estimate the fair value of the market-based RSUs granted during 2022:


	Year Ended December 31, 2022
Stock price	$	12.98
Volatility		82.5	%
Remaining term (years)		2.7
Risk-free rate		2.9	%
Expected dividend yield		0.0

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Summary of Reconciliation of Statutory Income Tax Rate To Effective Income Tax Rate

A reconciliation of the Company’s statutory income tax rate to the Company’s effective income tax rate in 2022 and 2021 is as follows:


	Year ended December 31,
	2022			2021
Federal statutory rate		21.00	%		21.00	%
State taxes, net of federal benefit		4.71	%		9.96	%
Valuation allowance		1.13	%		(32.12	)%
Other		0.97	%		1.16	%
		27.81	%		—	%

Summary of Net Deferred Income Tax Asset

As of December 31, 2022 and 2021, the net deferred income tax asset balance related to the following:


	December 31,
	2022			2021
	(in thousands)
Deferred tax assets:
Net operating loss	$	10,531		$	31,414
Capitalized research and development		18,724			—
Capitalized organizational and start-up expenses		127			140
Licenses		461			1,875
Accrued expenses		1,977			968
Research and development credit		1,110			1,563
Equity-based compensation		12,087			8,584
Basis difference on gain on sale of Cullinan Pearl		1,805			—
Lease liability		1,345			—
Gross deferred tax assets		48,167			44,544
Valuation allowance		(46,766	)		(44,552	)
Net deferred tax asset		1,401			(8	)
Deferred tax liability
ROU asset		1,108			—
Depreciation and amortization		293			(8	)
Net deferred tax asset	$	—		$	—

Summary of Valuation Allowance

The Company’s valuation allowance increased during 2022 and 2021 due primarily to the generation of NOLs as follows:


	Year ended December 31,
	2022		2021
	(in thousands)
Valuation allowance at beginning of year	$	44,552	$	22,642
Increases recorded to income tax provision		1,712		21,674
Increases recorded to equity		502		236
Valuation allowance at end of year	$	46,766	$	44,552

Leases (Tables)

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Supplemental Cash Flow Information Relating to Leases

The following table summarizes supplemental cash flow information for 2022 (in thousands):


	Year Ended December 31, 2022
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from operating leases(1)	$	260
ROU asset obtained in exchange for an operating lease liability	$	4,931

Summarizes Lease Term and Discount Rate

The following table summarizes the weighted-average lease term and discount rate as of December 31, 2022:


	December 31, 2022
Weighted-average remaining lease term (in years)	3.2
Weighted-average discount rate		10.8	%

Summarizes of future minimum lease payments

The following table summarizes the Company’s future minimum lease payments under the new lease accounting standard as of December 31, 2022 (in thousands):


	December 31, 2022
2023	$	1,881
2024		1,738
2025		1,461
2026		872
Total future minimum lease payments		5,952
Less: imputed interest		(941	)
Total lease liabilities at present value	$	5,011

The following table summarizes the Company’s future minimum lease payments under the prior lease accounting standard as of December 31, 2021 (in thousands):


Years Ending December 31,	(in thousands)
2023	$	608
2024		618
2025		313
	$	1,539

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Summary of Calculation of Basic and Diluted Net Loss Per Share


	Year ended December 31,
	2022		2021
	(in thousands, except per share data)
Numerator:
Net income (loss) attributable to common stockholders of Cullinan	$	111,214	$	(65,570	)
Denominator:
Weighted-average common stock outstanding - basic		45,164		43,077
Dilutive effect of common stock issuable from assumed exercise of equity awards		1,476		—
Weighted-average common stock outstanding - diluted		46,640		43,077
Earnings (net loss) per share:
Basic	$	2.46	$	(1.52	)
Diluted	$	2.38	$	(1.52	)

Summary of Equity Instruments Excluded from Computation of Diluted Net Loss Per Share


	Year ended December 31,
	2022		2021
Stock options		6,842		9,259
RSAs		—		89
RSUs		25		—
ESPP		7		—
Total		6,874		9,348

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2022	Jan. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Nature Of Business And Basis Of Presentation [Line Items]
Net proceeds received from offering		$ 264,500	$ 0	$ 267,268
Up-front payment	$ 275,000
Cash, cash equivalents, short-term investments and long-term investments			467,300
Long-term investments and interest receivables			82,800
Long-term investments			80,882	140,397
Accumulated deficit			$ (47,695)	$ (158,909)
IPO
Nature Of Business And Basis Of Presentation [Line Items]
Common stock shares issued and sold		13,685,000
Stock, price per Share		$ 21.00
Underwriters' Option
Nature Of Business And Basis Of Presentation [Line Items]
Common stock shares issued and sold		1,785,000

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounting Policies [Line Items]
Description of voting rights		Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company.
Unrealized gain (loss) on investments \| $	$ (1,763)	$ (836)
Number of reporting segments \| Segment	1
Number of operating segments \| Segment	1
Operating Lease Term	12 months
Deferred offering costs \| $			$ 2,700

Summary of Significant Accounting Policies - Summary of Estimated Useful Life of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2022
Office Furniture and Equipment
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated useful life of property and equipment	Shorter of the useful life of the asset or the lease term

Summary of Significant Accounting Policies - Summary of balance sheet adjustments in connection with ASC 842 (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Operating lease right-of-use assets	$ 4,130	$ 1,311	$ 0
Operating lease liabilities, current	1,421	505
Deferred rent	0	0	65
Lease liabilities, non-current	$ 3,590	871
As Reported
Operating lease right-of-use assets			0
Operating lease liabilities, current			0
Deferred rent			65
Lease liabilities, non-current			$ 0
Adjustment
Operating lease right-of-use assets		1,311
Operating lease liabilities, current		505
Deferred rent		(65)
Lease liabilities, non-current		$ 871

Sale of Cullinan Pearl and Co-Development Agreement with Taiho (Additional Information) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Cash transferred with sale		$ 2,898
Gain on sale of Cullinan Pearl		276,785	$ 0
Repayment of convertible note		2,200	0
Research and development costs		91,948	$ 57,751
Prepaid expenses and other current assets		619
Pearl - Taiho
Defined Benefit Plan Disclosure [Line Items]
Receive upfront payment from party	$ 275,000
Cash transferred with sale	2,900
Additional receive payments from the party	130,000
Gain on sale of Cullinan Pearl	$ 276,800
Repayment of convertible note		2,200
Percentage of profits from potential sales	50.00%
Research and development costs		3,500
Research and development expense related to share of costs		2,500
Prepaid expenses and other current assets		$ 1,000

Sale of Cullinan Pearl and Co-Development Agreement with Taiho - Schedule of cash consideration received (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Book Value of Asset Sold [Abstract]
Cash	$ 2,898
Prepaid expenses and other current assets	619
Amounts attributable to assets sold	3,517
Book Value Of Liability Sold [Abstract]
Accrued expenses and other current liabilities	2,404
Amounts attributable to liabilities sold	2,404
Total identifiable net assets sold	1,113
Upfront consideration, inclusive of cash transferred of $2,898	277,898
Gain on sale of Cullinan Pearl	$ 276,785

Sale of Cullinan Pearl and Co-Development Agreement with Taiho - Parenthetical (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-Sale [Abstract]
Upfront consideration, cash transferred	$ 2,898

Reorganization and Reverse Stock Split - Summary of LLC Units Previously Reported as Redeemable Preferred Units or Temporary Equity Converted Reclassified to Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stockholders' Equity (Members' Deficit)
Common Stock	$ 5	$ 4
Additional paid-in capital	585,320	584,714
Accumulated other comprehensive loss	(2,601)	(838)
Accumulated deficit	(47,695)	(158,909)
Total Cullinan Stockholders' Equity (Members' Deficit)	535,029	424,971
Non-controlling interests in subsidiaries	0	403
Total Stockholders' Equity (Members' Deficit)	$ 535,029	$ 425,374	$ 200,315

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

+ References

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+ Details

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

+ References

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+ Details

- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

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+ Details

Financial Instruments - Schedule of Short-term and Long-term Investment Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	$ 394,623	$ 371,927
Gross Unrealized Gains	32	0
Gross Unrealized Losses	(2,633)	(838)
Estimated Fair Value	392,022	371,089
Short Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	313,187	230,849
Gross Unrealized Gains	14	0
Gross Unrealized Losses	(2,061)	(157)
Estimated Fair Value	311,140	230,692
Long Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	81,436	141,078
Gross Unrealized Gains	18	0
Gross Unrealized Losses	(572)	(681)
Estimated Fair Value	80,882	140,397
Asset-backed Securities \| Short Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	16,625
Gross Unrealized Gains	0
Gross Unrealized Losses	(15)
Estimated Fair Value	16,610
Asset-backed Securities \| Long Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost		3,044
Gross Unrealized Gains		0
Gross Unrealized Losses		(8)
Estimated Fair Value		3,036
U.S. Government Notes \| Short Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	34,029	18,033
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(290)	(35)
Estimated Fair Value	33,739	17,998
U.S. Government Notes \| Long Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost		20,166
Gross Unrealized Gains		0
Gross Unrealized Losses		(77)
Estimated Fair Value		20,089
Corporate notes \| Short Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	244,498	98,642
Gross Unrealized Gains	11	0
Gross Unrealized Losses	(1,743)	(95)
Estimated Fair Value	242,766	98,547
Corporate notes \| Long Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	81,436	117,868
Gross Unrealized Gains	18	0
Gross Unrealized Losses	(572)	(596)
Estimated Fair Value	80,882	117,272
Commercial Paper \| Short Term Investments
Debt Securities, Held-to-Maturity, Allowance for Credit Loss [Line Items]
Amortized Cost	18,035	114,174
Gross Unrealized Gains	3	0
Gross Unrealized Losses	(13)	(27)
Estimated Fair Value	$ 18,025	$ 114,147

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 1,309	$ 309
Less: accumulated depreciation	(135)	(232)
Total property and equipment, net	1,174	77
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	0	70
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	681	134
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 628	$ 105

Property and Equipment, Net (Additional Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation Expense	$ 0.1	$ 0.1

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued Expenses And Other Current Liabilities [Abstract]
Research and development costs	$ 7,486	$ 5,028
Accrued bonus	4,516	2,576
Other current liabilities	1,955	973
Convertible note and accrued interest	178	0
Accrued Expenses And Other Current Liabilities	$ 14,135	$ 8,577

License and Collaboration Agreements - Summary of Research and Development Costs Related to Collaboration and License Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs	$ 91,948	$ 57,751
Pearl - Taiho
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs	3,500
Collaboration and License Agreements \| Adimab
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs	$ 500
Collaboration and License Agreements \| Pearl - Taiho
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development costs		$ 3,000

License and Collaboration Agreements - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2019	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
License And Collaboration Agreements [Line Items]
Common stock, shares issued	45,796,449		45,796,449	44,292,102
Research and Development Expense			$ 91,948	$ 57,751
Milestone payments received	$ 100
Cash balance	$ 2,898		2,898
Nonrefundable license fee					$ 20,000
Net issuance of common stock under equity-based compensation plans			6,020	3,281
Net upfront revenue			0	18,943
Pearl - Taiho
License And Collaboration Agreements [Line Items]
Research and Development Expense			3,500
Pearl - Taiho \| Collaboration and License Agreements
License And Collaboration Agreements [Line Items]
Research and Development Expense				3,000
Amber—Massachusetts Institute of Technology \| Collaboration and License Agreements \| Maximum
License And Collaboration Agreements [Line Items]
Milestone payments received		$ 12,500
Amber—Massachusetts Institute of Technology \| Clinical and Regulatory Events First Indication \| Maximum
License And Collaboration Agreements [Line Items]
Milestone payments received		7,000
Amber—Massachusetts Institute of Technology \| Clinical and Regulatory Events Second Indication
License And Collaboration Agreements [Line Items]
Milestone payments received		$ 5,500
Amber—Massachusetts Institute of Technology \| Clinical and Regulatory Events
License And Collaboration Agreements [Line Items]
Percentage of Milestone Payments		100.00%
Adimab \| Collaboration and License Agreements
License And Collaboration Agreements [Line Items]
Research and Development Expense			500
Adimab \| Collaboration and License Agreements \| Maximum
License And Collaboration Agreements [Line Items]
Research and Development Expense				100
Massachusetts Institute of Technology [Member] \| Collaboration and License Agreements
License And Collaboration Agreements [Line Items]
Research and Development Expense			$ 400	100
Pearl—Zai Lab License Agreement
License And Collaboration Agreements [Line Items]
Net upfront revenue				$ 18,900

Cullinan-MICA Asset Acquisition - Additional Information (Details) - shares	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Asset Acquisition [Line Items]
Common stock, shares authorized	150,000,000	150,000,000
Preferred stock shares authorized	10,000,000	10,000,000
Preferred stock shares outstanding	0	0
Common stock, shares outstanding	45,796,449	44,292,102

Common Stock and Noncontrolling Interest in Subsidiaries - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended						12 Months Ended
	Nov. 30, 2022	Oct. 31, 2022	Jul. 31, 2022	Mar. 31, 2022	Jul. 31, 2021	Jun. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2022
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Common stock, shares authorized							150,000,000	150,000,000
Common stock, voting rights								Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company.
Shares issued							0	0
Shares sold/issued							45,796,449	44,292,102
Losses attributed to noncontrolling interests							$ (2,019)	$ (1,915)
Net issuance of common stock under equity-based compensation plans							6,020	3,281
Purchase of shares				6,700,000		700,000
Equity-based compensation expense							$ 27,957	$ 24,375
Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued during period								13,685,000
Cullinan Mica \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets	900,000
Cullinan Mica \| HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock options held by noncontrolling interests							200,000
Cullinan Mica \| Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets	900,000
Stock Issued During Period, Value, Purchase of Assets	$ 2,600
Cullinan Mica \| Common Stock \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets	400,000
Maximum \| Noncontrolling Interests in Subsidiaries \| HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests							$ 400	$ 100
Series A Preferred Stock \| Cullinan Mica \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets		1,500,000
Series A-2 Junior Preferred Stock \| Cullinan Mica \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets		11,500,000
Series A Junior Preferred Stock \| Cullinan Mica \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Stock issued during period shares purchase of assets		2,000,000.0
Cullinan Amber Corp \| MIT License Agreement between Amber and MIT \| Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued	500,000								300,000
Shares sold/issued						200,000
Cullinan Amber Corp \| Dr. Wittrup \| Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued	200,000
Cullinan Amber Corp \| Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued	10,000,000.0					3,000,000.0			6,000,000.0
Ownership interest percentage							6.00%
Percentage of share purchased as part of asset acquisition							94.00%
Cullinan Florentine Corp \| HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests							$ 0
Cullinan Florentine Corp \| Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Ownership interest percentage							4.00%
Percentage of share purchased as part of asset acquisition							96.00%
Cullinan Florentine Corp \| Series B Preferred Units
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued during period			3,750,000		7,500,000
Cullinan Pearl Corp \| HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests							$ 300	700
MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests							$ 1,200	$ 1,100
Ownership interest percentage							5.00%
Percentage of share purchased as part of asset acquisition							95.00%
MICA \| HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares price per share							$ 0.22
Share-based payment award, accelerated vesting, number		300,000
Equity-based compensation expense		$ 600
MICA \| Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Ownership interest percentage							4.00%
Percentage of share purchased as part of asset acquisition							96.00%
MICA \| Series A Senior Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Purchase of shares						5,400,000
MICA \| Series A Senior Preferred Stock \| Investor
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds				$ 1,200		$ 900
Purchase of shares				900,000
MICA \| Series A-2 Junior Preferred Stock \| Cullinan Mica \| Stock Purchase And Transfer Agreements
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds		$ 30,700

Leases - Additional Information (Details) $ in Millions					12 Months Ended
Leases - Additional Information (Details) $ in Millions	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Aug. 31, 2022 ft²	Dec. 31, 2022 USD ($) ft²	Dec. 31, 2021 USD ($)
Lessee Lease Description [Line Items]
Operating lease commence date					Feb. 28, 2018
Operating lease expiration date					Jun. 30, 2024
Rent expense					$ 1.1	$ 0.6
Lease payments					$ 0.3
Sublease payment			$ 0.1
Scenario Adjustment [Member]
Lessee Lease Description [Line Items]
Sublease payment	$ 0.3	$ 0.6
M A
Lessee Lease Description [Line Items]
Operating lease rentable area \| ft²				14,000	8,000

Supplemental cash flow information - (Details)
$ in Thousands

12 Months Ended

Dec. 31, 2022

USD ($)

Leases [Abstract]

Operating cash flows from operating leases(1)

$ 260

^[1]

ROU asset obtained in exchange for an operating lease liability

$ 4,931

[1]	Operating cash flows from operating leases includes cash inflow of $0.3 million reimbursed by the lessor for improvements made to the newly leased office space pursuant to the terms of the Suite 1350 lease.

Summarizes lease term and discount rate - (Details)	Dec. 31, 2022
Leases [Abstract]
Weighted-average remaining lease term (in years)	3 years 2 months 12 days
Weighted-average discount rate	10.80%

Future minimum lease payments - (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
2023	$ 1,881	$ 608
2024	1,738	618
2025	1,461	313
2026	872
Total future minimum lease payments	5,952	$ 1,539
Less: imputed interest	(941)
Total lease liabilities at present value	$ 5,011

Equity-Based Compensation - Schedule of Equity-based Compensation Expense Categories In Consolidated Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total equity-based compensation	$ 27,957	$ 24,375
Research and Development
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total equity-based compensation	11,018	8,914
General and Administrative
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Total equity-based compensation	$ 16,939	$ 15,461

Equity-Based Compensation - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands

1 Months Ended

12 Months Ended

Mar. 31, 2022

Jun. 30, 2021

Dec. 31, 2022

Dec. 31, 2021

Jan. 01, 2023

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Options granted term

8 years 3 months 21 days

Options granted, weighted average grant date fair value

$ 9.02

$ 15.73

Unrecognized compensation costs

$ 66,000

$ 75,800

Unrecognized compensation costs, recognition period

2 years 10 months 24 days

3 years 2 months 12 days

Options exercised, intrinsic value

$ 13,100

$ 10,700

Common stock, par value

$ 0.0001

Common stock, shares issued

45,796,449

44,292,102

Equity-based compensation expense

$ 27,957

$ 24,375

Purchase of shares

6,700,000

700,000

Net issuance of common stock under equity-based compensation plans

$ 6,020

$ 3,281

Common stock issuable upon exercise of stock options, weighted average exercise price

$ 4.31

$ 4.30

Research and Development Expense

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Equity-based compensation expense

$ 11,018

$ 8,914

General and Administrative

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Equity-based compensation expense

$ 16,939

$ 15,461

RSUs

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Unrecognized compensation costs, recognition period

2 years 7 months 6 days

Non-options unrecognized compensation cost

$ 4,300

Fair value of non-options shares vested

$ 600

Shares price per share

$ 12.98

Weighted average fair value of options granted

^[1]

$ 13.28

Restricted Stock Awards

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Unrecognized compensation costs, recognition period

1 year

1 year 6 months

Non-options unrecognized compensation cost

$ 100

$ 300

Fair value of non-options shares vested

$ 600

$ 8,500

2021 Stock Option and Incentive Plan

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Options granted term

10 years

Award vesting period

4 years

Number of shares available for grant

2,200,000

Increase in number of shares reserved and available for issuance percentage

5.00%

2021 Stock Option and Incentive Plan | Subsequent Event

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Increase in number of shares reserved and available for issuance

2,300,000

ESPP

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock, shares reserved for future issuance

800,000

Increase in number of shares reserved and available for issuance percentage

1.00%

Increase in number of shares reserved and available for issuance

800,000

ESPP | Subsequent Event

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Increase in number of shares reserved and available for issuance

500,000

ESPP | Maximum

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Common stock, shares issued

100,000

[1]	The number granted represents the number of shares issuable upon vesting of service-based and market-based RSUs, assuming the Company achieves its corporate stock price metrics at the target achievement level.

Equity-Based Compensation - Schedule of Assumptions Used to Estimate Fair Value of Options (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	2.65%	1.02%
Expected term (in years)	6 years	6 years
Expected volatility	79.81%	76.22%
Expected dividend yield	0.00%	0.00%

Equity-Based Compensation - Schedule of Assumptions Used to Estimate Fair Value of RSUs (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Volatility	79.81%	76.22%
Remaining term (years)	6 years	6 years
Risk-free rate	2.65%	1.02%
Expected dividend yield	0.00%	0.00%
RSUs
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock price	$ 12.98
Volatility	82.50%
Remaining term (years)	2 years 8 months 12 days
Risk-free rate	2.90%
Expected dividend yield	0.00%

Equity-Based Compensation - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Number of Options, Beginning Balance	9,259,000	4,603,000
Number of Options, Granted	2,888,000	5,482,000
Number of Options, Exercised	(1,523,000)	(763,000)
Number of Options, Forfeited	(1,290,000)	(63,000)
Number of Options, Ending Balance	9,334,000	9,259,000
Number of Options, Exercisable	3,706,000
Weighted Average Exercise Price, Beginning Balance	$ 15.77	$ 4.30
Weighted Average Exercise Price, Granted	12.96	23.82
Weighted Average Exercise Price, Exercised	4.31	4.30
Weighted Average Exercise Price, Forfeited	13.80	17.23
Weighted Average Exercise Price, Ending Balance	17.04	$ 15.77
Weighted Average Exercise Price, Exercisable	$ 15.31
Weighted Average Remaining Contractual Term (Years), Outstanding	8 years 3 months 21 days
Weighted Average Remaining Contractual Term (Years), Exercisable	7 years 3 months 25 days
Aggregate Intrinsic Value, Outstanding	$ 11,526
Aggregate Intrinsic Value, Exercisable	$ 10,060

Equity-Based Compensation - Summary of Activity Related to RSUs (Details) - RSUs

12 Months Ended

Dec. 31, 2022

$ / shares

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Number of Shares, Outstanding Unvested, Beginning Balance | shares

Number of Shares, Granted | shares

502,000

^[1]

Number of Shares, Vested | shares

(46,000)

Number of Shares, Forfeited | shares

(87,000)

Number of Shares, Outstanding Unvested, Ending Balance | shares

369,000

Weighted-Average Grant Date Fair Value, Outstanding Unvested, Beginning Balance | $ / shares

$ 0

Weighted-Average Grant Date Fair Value, Granted | $ / shares

13.28

^[1]

Weighted-Average Grant Date Fair Value, Vested | $ / shares

13.60

Weighted-Average Grant Date Fair Value, Forfeited | $ / shares

13.60

Weighted-Average Grant Date Fair Value, Outstanding Unvested, Ending Balance | $ / shares

$ 13.16

[1]	The number granted represents the number of shares issuable upon vesting of service-based and market-based RSUs, assuming the Company achieves its corporate stock price metrics at the target achievement level.

Equity-Based Compensation - Summary of Activity Related to RSAs (Details) - Restricted Stock Awards - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Outstanding Unvested, Beginning Balance	89,000	364,000
Number of Shares, Vested	(46,000)	(275,000)
Number of Shares, Forfeited	(28,000)
Number of Shares, Outstanding Unvested, Ending Balance	15,000	89,000
Weighted-Average Grant Date Fair Value, Outstanding Unvested, Beginning Balance	$ 3.87	$ 2.04
Weighted-Average Grant Date Fair Value, Vested	3.87	1.45
Weighted-Average Grant Date Fair Value, Forfeited	3.87
Weighted-Average Grant Date Fair Value, Outstanding Unvested, Ending Balance	$ 3.87	$ 3.87

Equity-Based Compensation - Summary of Restricted Common Unit Activities (Details) - RSUs - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Vested	(46,000)
Number of Shares, Outstanding Unvested, Ending Balance	369,000	0

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Royalties under obligation	$ 0	$ 0

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Line Items]
Current income tax expense (benefit)	$ 42,100	$ 0
Deferred Income Tax Expense (Benefit)		0
Operating loss carryforwards	$ 42,600	117,400
Operating loss carryforwards, limitations on use	Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, as well as similar state provisions, NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50%. The rules generally operate by focusing on changes in ownership among stockholders considered by the rules as owning, directly or indirectly, 5% or more of the stock of a company and any change in ownership arising from new issuances of stock by the company.
Uncertain tax positions	$ 0	0
Accrued interest or penalties	$ 0	0
Federal
Income Tax Disclosure [Line Items]
Operating loss carryforwards expiration year	2036
Federal \| Research and Development
Income Tax Disclosure [Line Items]
Tax credit carryforward	$ 900	1,300
Tax credit carryforward expiration year	2036
Federal \| Prior to 2018 Tax Year
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 5,800
Federal \| NOL Current and Prior to 2018 Tax Year
Income Tax Disclosure [Line Items]
Operating loss carryforwards	36,800
Federal \| NOL Current and Prior to 2018 Tax Year \| Research and Development Tax Credit Carryforward Indefinitely
Income Tax Disclosure [Line Items]
Tax credit carryforward	300	300
State
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 27,100	$ 119,000
Operating loss carryforwards expiration year	2036

Income Taxes - Summary of Reconciliation of Statutory Income Tax Rate To Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory rate	21.00%	21.00%
State taxes, net of federal benefit	4.71%	9.96%
Valuation allowance	1.13%	(32.12%)
Other	0.97%	(1.16%)
Effective income tax rate reconciliation	27.81%	0.00%

Income Taxes - Summary of Net Deferred Income Tax Asset (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss	$ 10,531	$ 31,414
Capitalized research and development	18,724	0
Capitalized organizational and start-up expenses	127	140
Licenses	461	1,875
Accrued expenses	1,977	968
Research and development credit	1,110	1,563
Equity-based compensation	12,087	8,584
Basis difference on gain on sale of Cullinan Pearl	1,805	0
Lease liability	1,345	0
Gross deferred tax assets	48,167	44,544
Valuation allowance	(46,766)	(44,552)	$ (22,642)
Net deferred tax asset	1,401	8
Deferred tax liability
ROU asset	1,108	0
Depreciation and amortization	(293)	(8)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Summary of Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Valuation Allowance [Abstract]
Valuation allowance at beginning of year	$ 44,552	$ 22,642
Increases recorded to income tax provision	1,712	21,674
Increases recorded to OCI/Equity	502	236
Valuation allowance at end of year	$ 46,766	$ 44,552

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Lessee Lease Description [Line Items]
Rent expense	$ 1,100	$ 600
Indemnification agreements
Lessee Lease Description [Line Items]
Accrued liabilities	$ 0	$ 0

Net Loss per Share - Summary of Calculation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss attributable to common stockholders of Cullinan	$ 111,214	$ (65,570)
Denominator
Weighted Average Number of Shares Outstanding, Basic	45,164	43,077
Dilutive effect of common stock issuable from assumed exercise of equity awards	1,476	0
Weighted Average Number of Shares Outstanding, Diluted	46,640	43,077
Earnings Per Share, Basic	$ 2.46	$ (1.52)
Earnings Per Share, Diluted	$ 2.38	$ (1.52)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

Net Loss per Share - Summary of Equity Instruments Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	6,874	9,348
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	6,842	9,259
RSAs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	0	89
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	25	0
ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Equity instruments excluded from computation of diluted net loss per share (in shares)	7	0

Subsequent Events (Additional Information) (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Dec. 31, 2022	Feb. 28, 2023	Jan. 31, 2023	Dec. 31, 2021
Subsequent Event [Line Items]
Preferred stock, par value	$ 0.0001			$ 0.0001
Common stock, shares outstanding	45,796,449			44,292,102
Preferred stock shares outstanding	0			0
Milestone payments received	$ 0.1
Subsequent Event [Member] \| Exchange Agreement \| Stockholders
Subsequent Event [Line Items]
Conversion of stock, description			Each share of the preferred stock will be convertible into 10 shares of Common Stock at the option of the holder at any time
Subsequent Event [Member] \| Exchange Agreement \| Stockholders \| Minimum
Subsequent Event [Line Items]
Ownership percentage			9.99%
Subsequent Event [Member] \| Exchange Agreement \| Stockholders \| Common Stock
Subsequent Event [Line Items]
Stock exchanged			6,500,000
Common stock, shares outstanding			39,300,000
Conversion of stock, shares converted			6,500,000
Subsequent Event [Member] \| Exchange Agreement \| Stockholders \| Series A Convertible Preferred Stock [Member]
Subsequent Event [Line Items]
Shares issued during period			600,000
Preferred stock, par value			$ 0.0001
Subsequent Event [Member] \| Exchange Agreement \| Stockholders \| Series A Preferred Stock
Subsequent Event [Line Items]
Preferred stock shares outstanding			600,000
Subsequent Event [Member] \| Harbour License Agreement \| Harbour BioMed US Inc.
Subsequent Event [Line Items]
Upfront License fee		$ 25.0
Subsequent Event [Member] \| Harbour License Agreement \| Harbour BioMed US Inc. \| Maximum \| Achievement Based
Subsequent Event [Line Items]
Milestone payments received		148.0
Subsequent Event [Member] \| Harbour License Agreement \| Harbour BioMed US Inc. \| Maximum \| Sales Based
Subsequent Event [Line Items]
Milestone payments received		$ 415.0

Financial Instruments - Summary of Fair Value of Financial Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	$ 311,140
Long Term Investments Fair Value Disclosure	80,882
Total cash, cash equivalents and investments	392,022
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	33,739	$ 230,692
Long Term Investments Fair Value Disclosure		140,397
Total cash, cash equivalents and investments		371,089
Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	16,610
Asset-backed Securities \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Investments Fair Value Disclosure		3,036
U.S. Government Notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		17,998
Long Term Investments Fair Value Disclosure		20,089
Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	242,766
Long Term Investments Fair Value Disclosure	80,882
Corporate notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		98,547
Long Term Investments Fair Value Disclosure		117,272
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	18,025
Commercial Paper \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		114,147
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Long Term Investments Fair Value Disclosure	0
Total cash, cash equivalents and investments	0
Fair Value, Inputs, Level 1 [Member] \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0	0
Long Term Investments Fair Value Disclosure		0
Total cash, cash equivalents and investments		0
Fair Value, Inputs, Level 1 [Member] \| Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] \| Asset-backed Securities \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] \| U.S. Government Notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] \| Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Long Term Investments Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] \| Corporate notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] \| Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] \| Commercial Paper \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	311,140
Long Term Investments Fair Value Disclosure	80,882
Total cash, cash equivalents and investments	392,022
Fair Value, Inputs, Level 2 [Member] \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	33,739	230,692
Long Term Investments Fair Value Disclosure		140,397
Total cash, cash equivalents and investments		371,089
Fair Value, Inputs, Level 2 [Member] \| Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	16,610
Fair Value, Inputs, Level 2 [Member] \| Asset-backed Securities \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Investments Fair Value Disclosure		3,036
Fair Value, Inputs, Level 2 [Member] \| U.S. Government Notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		17,998
Long Term Investments Fair Value Disclosure		20,089
Fair Value, Inputs, Level 2 [Member] \| Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	242,766
Long Term Investments Fair Value Disclosure	80,882
Fair Value, Inputs, Level 2 [Member] \| Corporate notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		98,547
Long Term Investments Fair Value Disclosure		117,272
Fair Value, Inputs, Level 2 [Member] \| Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	18,025
Fair Value, Inputs, Level 2 [Member] \| Commercial Paper \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		114,147
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Long Term Investments Fair Value Disclosure	0
Total cash, cash equivalents and investments	0
Fair Value, Inputs, Level 3 [Member] \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Long Term Investments Fair Value Disclosure		0
Total cash, cash equivalents and investments		0
Fair Value, Inputs, Level 3 [Member] \| Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Fair Value, Inputs, Level 3 [Member] \| Asset-backed Securities \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] \| U.S. Government Notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] \| Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure	0
Long Term Investments Fair Value Disclosure	$ 0
Fair Value, Inputs, Level 3 [Member] \| Corporate notes \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		0
Long Term Investments Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] \| Commercial Paper \| Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short Term Investments Fair Value Disclosure		$ 0