Iovance Biotherapeutics (IOVA) 10-K 28 Feb 24 2023 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Feb. 22, 2024	Jun. 30, 2023
Document And Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-36860
Entity Registrant Name	IOVANCE BIOTHERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	75-3254381
Entity Address, Address Line One	825 Industrial Road, Suite 400
Entity Address, City or Town	San Carlos
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94070
City Area Code	650
Local Phone Number	260-7120
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $ 0.000041666 Par Value per Share
Trading Symbol	IOVA
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		279,307,043
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
ICFR Auditor Attestation Flag	true
Entity Public Float			$ 1.4
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	San Mateo, California
Entity Central Index Key	0001425205
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current Assets
Cash and cash equivalents	$ 114,888	$ 231,731
Trade accounts receivable	151
Short-term investments	164,979	240,114
Inventory	10,372
Prepaid expenses and other assets	17,458	7,271
Total Current Assets	307,848	479,116
Property and equipment, net	114,030	105,232
Intangible assets, net	229,258
Operating lease right-of-use assets	62,515	73,015
Restricted cash	66,430	6,430
Long-term assets	270	189
Total Assets	780,351	663,982
Current Liabilities
Accounts payable	33,123	26,603
Accrued expenses	69,406	52,295
Operating lease liabilities	7,777	12,587
Total Current Liabilities	110,306	91,485
Non-Current Liabilities
Operating lease liabilities - non-current	67,085	71,859
Deferred tax liabilities	17,347
Long-term note payable	1,000	1,000
Total Non-Current Liabilities	85,432	72,859
Total Liabilities	195,738	164,344
Commitments and contingencies
Stockholders' Equity
Common stock, $0.000041666 par value; 500,000,000, and 300,000,000 shares authorized, 256,135,715 and 187,812,072 shares issued and outstanding as of December 31, 2023 and December 31, 2022, respectively	11	8
Accumulated other comprehensive income (loss)	2,526	(902)
Additional paid-in capital	2,594,448	2,068,867
Accumulated deficit	(2,012,375)	(1,568,338)
Total Stockholders' Equity	584,613	499,638
Total Liabilities and Stockholders' Equity	780,351	663,982
Series A Convertible Preferred Stock
Stockholders' Equity
Preferred stock, Value	0	0
Series B Convertible Preferred Stock
Stockholders' Equity
Preferred stock, Value	$ 3	$ 3

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Common stock, par or stated value per share	$ 0.000041666	$ 0.000041666
Common stock, shares authorized	500,000,000	300,000,000
Common Stock, Shares, Issued	256,135,715	187,812,072
Common Stock, Shares, Outstanding	256,135,715	187,812,072
Series A Convertible Preferred Stock
Preferred stock, par or stated value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	17,000	17,000
Preferred Stock, Shares Issued	194	194
Preferred stock, shares outstanding	194	194
Series B Convertible Preferred Stock
Preferred stock, par or stated value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	11,500,000	11,500,000
Preferred Stock, Shares Issued	2,842,158	2,842,158
Preferred stock, shares outstanding	2,842,158	2,842,158

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Consolidated Statements of Operations
Total revenue	$ 1,189
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:ProductMember
Costs and expenses
Cost of sales	$ 10,755
Research and development	344,077	$ 294,781	$ 259,039
Selling, general and administrative	106,916	104,097	83,664
Total costs and expenses	461,748	398,878	342,703
Loss from operations	(460,559)	(398,878)	(342,703)
Other income
Interest income, net	13,043	2,985	451
Net Loss before income taxes	(447,516)	(395,893)	(342,252)
Income tax benefit	3,479	0	0
Net Loss	$ (444,037)	$ (395,893)	$ (342,252)
Net Loss Per Share of Common Stock, Basic	$ (1.89)	$ (2.49)	$ (2.23)
Net Loss Per Share of Common Stock, Diluted	$ (1.89)	$ (2.49)	$ (2.23)
Weighted Average Shares of Common Stock Outstanding, Basic	235,131	159,259	153,406
Weighted Average Shares of Common Stock Outstanding, Diluted	235,131	159,259	153,406

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Consolidated Statements of Comprehensive Loss
Net Loss	$ (444,037)	$ (395,893)	$ (342,252)
Other comprehensive loss:
Unrealized gain/(loss) on investments	940	(301)	(620)
Foreign currency translation adjustment	2,488
Comprehensive Loss	$ (440,609)	$ (396,194)	$ (342,872)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Series A Convertible Preferred Stock Preferred Stock	Series B Convertible Preferred Stock Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Beginning Balance at Dec. 31, 2020		$ 4	$ 6	$ 1,486,662	$ 19	$ (830,193)	$ 656,498
Beginning Balance (in Shares) at Dec. 31, 2020	194	3,581,119	146,874,917
Stock-based compensation expense				69,765			69,765
Common stock issued upon purchase of employee stock purchase plan				1,586			1,586
Common stock issued upon purchase of employee stock purchase plan (in shares)			94,148
Common stock issued upon exercise of stock options				33,526			33,526
Common stock issued upon exercise of stock options (in shares)			2,822,617
Common stock issued from preferred stock conversion		$ (1)	$ 1	1			1
Common stock issued from preferred stock conversion (in Shares)		(738,961)	738,961
Common stock sold in public and/or at the market offerings, net of offering costs				203,155			203,155
Common stock sold in public and/or at the market offerings, net of offering costs (in shares)			6,474,099
Unrealized gain/(loss) on investments					(620)		(620)
Net Loss						(342,252)	(342,252)
Ending Balance at Dec. 31, 2021		$ 3	$ 7	1,794,695	(601)	(1,172,445)	621,659
Ending Balance (in Shares) at Dec. 31, 2021	194	2,842,158	157,004,742
Stock-based compensation expense				84,022			84,022
Common stock issued upon purchase of employee stock purchase plan				1,655			1,655
Common stock issued upon purchase of employee stock purchase plan (in shares)			262,701
Vesting of restricted shares issued for services (in shares)			894,760
Tax payments related to shares retired for vested restricted stock units				(2,649)			(2,649)
Tax payments related to shares retired for vested restricted stock units (in shares)			(342,703)
Common stock issued upon exercise of stock options				1,642			1,642
Common stock issued upon exercise of stock options (in shares)			203,579
Common stock sold in public and/or at the market offerings, net of offering costs			$ 1	189,501			189,502
Common stock sold in public and/or at the market offerings, net of offering costs (in shares)			29,788,993
Unrealized gain/(loss) on investments					(301)		(301)
Net Loss						(395,893)	(395,893)
Ending Balance at Dec. 31, 2022		$ 3	$ 8	2,068,867	(902)	(1,568,338)	499,638
Ending Balance (in Shares) at Dec. 31, 2022	194	2,842,158	187,812,072
Stock-based compensation expense				62,625			62,625
Common stock issued upon purchase of employee stock purchase plan				2,410			2,410
Common stock issued upon purchase of employee stock purchase plan (in shares)			435,459
Vesting of restricted shares issued for services (in shares)			1,253,465
Tax payments related to shares retired for vested restricted stock units				(2,795)			(2,795)
Tax payments related to shares retired for vested restricted stock units (in shares)			(454,367)
Common stock issued upon exercise of stock options				63			63
Common stock issued upon exercise of stock options (in shares)			8,860
Stock issued during period, value, new issues			$ 3	463,278			463,281
Common stock sold in public and/or at the market offerings, net of offering costs (in shares)			67,080,226
Unrealized gain/(loss) on investments					940		940
Foreign currency cumulative translation adjustment					2,488		2,488
Net Loss						(444,037)	(444,037)
Ending Balance at Dec. 31, 2023		$ 3	$ 11	$ 2,594,448	$ 2,526	$ (2,012,375)	$ 584,613
Ending Balance (in Shares) at Dec. 31, 2023	194	2,842,158	256,135,715

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows from Operating Activities
Net Income (Loss)	$ (444,037)	$ (395,893)	$ (342,252)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	62,625	84,022	69,765
Unrealized exchange gains	70
Amortization of intangible assets	9,849	0
Amortization of right of use asset	11,710	11,825	10,869
Depreciation and amortization of property and equipment	11,568	9,310	3,111
Deferred tax benefit	(3,479)
Accretion of discounts and premiums on investments	(3,605)	474	6,013
Loss on write-off of fixed assets		397
Changes in assets and liabilities:
Prepaid expenses, other assets and long-term assets	(10,062)	(2,130)	2,775
Trade accounts receivable	(149)
Inventory	(10,118)
Operating lease liabilities	(10,794)	(1,942)	(5,882)
Accounts payable	4,828	5,883	6,976
Accrued expenses and other liabilities	19,774	(4,703)	20,684
Net cash used in operating activities	(361,820)	(292,757)	(227,941)
Cash Flows from Investing Activities
Maturities of investments	285,583	522,696	762,914
Purchase of investments	(205,902)	(245,816)	(725,208)
Cash paid for acquisition, net of cash acquired	(212,633)
Purchase of property and equipment	(22,290)	(20,425)	(37,574)
Net cash provided by / (used in) investing activities	(155,242)	256,455	132
Cash Flows from Financing Activities
Tax payments related to shares withheld for vested restricted stock units	(2,795)	(2,649)
Proceeds from the issuance of common stock under employee stock purchase plan	2,410	1,655	1,586
Proceeds from the issuance of common stock upon exercise of options	63	1,642	33,526
Proceeds from the issuance of common stock, net	463,281	189,502	203,156
Proceeds from the issuance of debt			1,000
Net cash provided by financing activities	462,959	190,150	239,268
Effect of exchange rate changes	(2,740)
Net increase in cash, cash equivalents and restricted cash	(56,843)	153,848	11,459
Cash, Cash Equivalents and Restricted Cash Beginning of Period	238,161	84,313	72,854
Cash, Cash Equivalents and Restricted Cash End of Period	181,318	238,161	84,313
Supplemental disclosure of non-cash investing and financing activities:
Fair value of net assets acquired	222,637
Net unrealized gain (loss) on investments	940	(301)	(620)
Acquisition of property and equipment included in accounts payable and accrued expenses	4,062	5,985	12,410
Conversion of convertible preferred stock to common stock			1
Lease liabilities arising from obtaining right-of-use asset from new leases	177	553	17,275
Lease liabilities arising from obtaining right-of-use asset from lease modifications	$ 1,033	$ 15,304	$ 7,800

GENERAL ORGANIZATION, BUSINESS

GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY	12 Months Ended
	Dec. 31, 2023
GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY
GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY	NOTE 1. GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY General Organization and Business Iovance Biotherapeutics, Inc. (the “Company”) is a commercial-stage biopharmaceutical company pioneering a transformational approach to treating cancer by harnessing the human immune system’s ability to recognize and destroy diverse cancer cells using therapies personalized for each patient. The Company’s mission is to be the global leader in innovating, developing and delivering tumor infiltrating lymphocyte (“TIL”) cell therapies for patients with solid tumor cancers. With the recent approval of the biologics license application (the “BLA”), the Company is executing the U.S. launch of Amtagvi™ (lifileucel), the first product within its autologous TIL cell therapy platform, and Proleukin ® ® The Company was founded to build upon the promise of TIL cell therapy that was previously demonstrated in single-center clinical trials at academic centers, including the National Cancer Institute (“NCI”). The Company’s multi-center trials, novel TIL products, manufacturing processes, facilities, and bioanalytical platforms have transformed TIL cell therapy into a commercially viable treatment which many more patients with cancer can access. The Company manufactures Amtagvi™ and its investigational TIL cell therapies using a centralized, scalable and proprietary 22-day manufacturing process which rejuvenates and multiplies polyclonal T cells unique to each patient into the billions and yields a cryopreserved, individualized therapy. The Company’s development pipeline includes multicenter trials of TIL cell therapies in additional treatment settings for solid tumor cancers. The Company is investigating TIL monotherapies for patients with later stage disease who were previously treated with standard of care therapies and TIL combinations with standard of care therapies to potentially improve outcomes in patients who are earlier in their disease. These trials two ongoing registrational trials to support a supplementary BLA (“sBLA”), of its TIL cell therapies in frontline advanced melanoma and in advanced non-small cell lung cancer following standard of care chemo-immunotherapy. The Company is also developing next generation therapies using TIL, such as genetically modified TIL cell therapy. Liquidity The Company is currently engaged in the development of therapeutics to fight cancer, specifically solid tumors. With the recent approval of the BLA, the Company expects to generate revenue from the sale of its product Amtagvi™. Furthermore, following the acquisition of the worldwide rights to Proleukin ® ® ® ® $444.0 The Company expects to continue to incur significant expenses to support its execution of the commercial launch of Amtagvi™, fund ongoing clinical programs, including its NSCLC registration study, IOV-LUN-202, and its frontline advanced melanoma Phase 3 confirmatory trial, TILVANCE-301, continue the development of its pipeline candidates, and for other general corporate purposes. Based on the funds the Company has available as of the date these consolidated financial statements are issued, which include estimated net proceeds (after deducting underwriting and other offering expenses) of approximately $197.1 million from the public offering of its common stock completed on February 22, 2024, the Company believes that it has sufficient capital to fund its anticipated operating expenses and capital expenditures as planned for at least the next twelve months from the date these consolidated financial statements are issued. Concentrations of Risk The Company is subject to credit risk from its portfolio of cash, cash equivalents, trade accounts receivable and investments. Under its investment policy, the Company limits amounts invested in securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. The Company does not believe it is exposed to any significant concentrations of credit risk from these financial instruments. The goals of its investment policy are safety and preservation of principal, diversification of risk, and liquidity of investments sufficient to meet cash flow requirements. ​

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES Cash, Cash Equivalents, and Investments The Company’s cash and cash equivalents include short-term investments with original maturities of three months or less when purchased. The Company's investments are classified as “available-for-sale.” The Company includes these investments in current assets or non-current assets in the Consolidated Balance Sheets based on the length of maturity from the reporting date and carries them at fair value. Unrealized gains and losses on available-for-sale securities are recorded in accumulated other comprehensive loss. Impairment losses related to credit losses (if any) are recorded as an allowance for credit losses with an offsetting entry to Interest income, net. No impairment losses related to credit losses were recognized for the years ended December 31, 2023, 2022 and 2021. The cost of debt securities is adjusted for the amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in Interest income, net in the consolidated statements of operations. Gains and losses on securities sold are recorded based on the specific identification method and are included in Interest income, net in the consolidated statements of operations. The Company has not incurred any realized gains or losses from sales of securities to date. The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, obligations issued by the U.S. government and U.S. government agencies as well as corporate debt securities and commercial paper, and places restrictions on maturities and concentration by type and issuer, except for securities issued by the U.S. government. Restricted Cash The Company maintains a required minimum balance in a segregated bank account in connection with its letters of credit for which amounts are restricted as to their use by the Company. Currently, the Company’s letters of credit are primarily comprised of one for the benefit of the landlord for the Iovance Cell Therapy Center (the “ i ® ® The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 ​ 2022 ​ 2021 Cash and cash equivalents ​ $ 114,888 ​ $ 231,731 ​ $ 78,229 Restricted cash ​ 66,430 ​ 6,430 ​ 6,084 Total cash, cash equivalents and restricted cash ​ $ 181,318 ​ $ 238,161 ​ $ 84,313 ​ Asset Acquisitions ​ The Company evaluates acquisitions of assets using the guidance in Accounting Standard Codification (“ASC”) Topic 805, Business Combinations (“ASC 805”), to determine whether the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to assess if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of assets. If the screen test is met, the transaction is accounted for as an asset acquisition. If the screen test is not met, further assessment is required to determine whether the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If the assets acquired do not constitute a business, the Company accounts for asset acquisitions using the cost accumulation and allocation method. Under this method, the cost of the acquisition, including direct acquisition-related costs, is allocated to the assets acquired on a relative fair value basis. Goodwill is not recognized in an asset acquisition and any difference between consideration transferred and the fair value of the net assets acquired is allocated to the identifiable assets acquired based on their relative fair values. Deferred tax liabilities arising from basis differences in assets acquired are calculated using the simultaneous equations method under ASC Topic 740, Income Taxes (“ASC 740”), and based on the effective tax rate. The resulting deferred tax liability is recorded in the consolidated balance sheet as of December 31, 2023. Contingent consideration in the scope of ASC Topic 815, Derivatives and Hedging (“ASC 815”), is included in the cost of the asset acquisition at its acquisition date fair value. Contingent consideration in the scope of ASC Topic 450, Contingencies (“ASC 450”), is recognized when it is both probable and reasonably estimable. Inventory and Cost of Sales ​ Inventory is stated at the lower of cost or net realizable value on a first-in, first-out basis. Cost includes amounts related to materials, labor and overhead. Net realizable value is the estimated selling price in the ordinary course of business less reasonably predictable costs of completion, disposal and transportation. Inventories presented in the consolidated balance sheet as of December 31, 2023 pertain solely to Proleukin ® ® Cost of sales includes the cost of Proleukin ® ® ® Trade Accounts Receivable ​ Trade accounts receivable are recorded net of allowances for product returns and estimated credit losses. The estimate of allowance for credit losses considers factors, including existing contractual payment and the aging of receivable from its customers. To date, the Company has determined that an allowance for doubtful accounts is not required. Intangible Assets ​ The Company’s intangible assets are initially measured based on an allocation of the cost of the acquisition to the assets acquired on a relative fair value basis and are recorded net of accumulated amortization. The Company amortizes the intangible assets on a straight-line basis over their estimated useful lives. When contingent consideration is a component of the cost of an asset acquisition, the Company capitalizes the amount of incremental cost from the contingent consideration related to the intangible asset acquired in the period the underlying contingency is resolved. When this occurs, the Company will recognize amortization expense on the incremental cost prospectively from the date the incremental costs are capitalized. The Company reviews intangible assets for impairment at least annually and whenever events or changes in circumstances have occurred which could indicate that the carrying value of the assets are not recoverable. If such indicators are present, the Company assesses the recoverability of affected assets by determining if the carrying value of the assets is less than the sum of the undiscounted future cash flows of the assets. If the assets are found to not be recoverable, the Company measures the amount of impairment by comparing the carrying value of the assets to their fair values. The Company determined that no indicators of impairment existed as of December 31, 2023. Leases The Company determines if an arrangement includes a lease at inception and thereafter, if modified. Operating leases are included in its consolidated balance sheets as Operating lease right-of-use assets and Operating lease liabilities as of December 31, 2023 and 2022. Operating lease right-of-use assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date or modification date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses an estimated incremental borrowing rate that is applicable to the Company based on the information available at the later of the lease commencement or modification date. The operating lease right-of-use assets also include any lease payments made less lease incentives. The Company’s leases may include options to extend or terminate the lease, which is considered in the lease term when it is reasonably certain that the Company will exercise any such options. Lease expense is recognized on a straight-line basis over the expected lease term and recorded in costs and expenses in the consolidated statements of operations. The Company has elected not to apply the recognition requirements of Accounting Standards Update (“ASU”) No. 2016-02 and No. 2018-10 (together “Topic 842”) for short-term leases. For lease agreements entered into by the Company that include lease and non-lease components, such components are generally accounted for separately. Property and Equipment, net ​ Property and equipment are stated at cost, net of accumulated depreciation and amortization. The cost of property and equipment is depreciated or amortized on the straight-line method over the following estimated useful lives. The depreciation or amortization of capitalized construction in progress costs, a component of property and equipment, net, begins once the underlying asset is placed into service and is recognized over the estimated useful lives: ​ Computer equipment 2 years Computer software ​ 5 years Office furniture and equipment ​ 5 years Lab, process, and validation equipment ​ 5 years Machinery and equipment ​ 5 – 7 years Utility equipment ​ Lesser of the remaining economic life of the asset or the lease-term Leasehold improvements ​ Lesser of the remaining economic life of the asset or the lease-term ​ Expenditures for maintenance and repairs are charged to operations as incurred while renewals and betterments are capitalized. Gains and losses on disposals are included within operating expenses in the consolidated statements of operations. Management assesses the carrying value of property and equipment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. If there is an indication of impairment, management prepares an estimate of future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If these cash flows are less than the carrying amount of the asset, an impairment loss is recognized to write down the asset to its estimated fair value. For the years ended December 31, 2023, 2022, and 2021, the Company did not recognize any impairments for its property and equipment. ​ Fair Value Measurements Under ASC Topic 820, Fair Value Measurements and Disclosures (“ASC 820”), fair value is defined as the price at which an asset could be exchanged, or a liability transferred in a transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or parameters are not available, valuation models are applied. Assets and liabilities recorded at fair value in the Company’s financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities, are as follows: - Level 1—These are investments where values are based on unadjusted quoted prices for identical assets in an active market that the Company has the ability to access. - Level 2—These are investments where values are based on quoted market prices in markets that are not active or model derived valuations in which all significant inputs are observable in active markets. - Level 3—These are financial instruments where values are derived from techniques in which one or more significant inputs are unobservable. The Company’s financial instruments consist of cash, cash equivalents, short-term investments, and long-term notes payable, all of which are reported at their respective fair value or approximate fair value on its consolidated balance sheets. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Where quoted prices are available in an active market, securities are classified as Level 1. ​ When quoted market prices are not available for a specific security, the Company estimates the fair value by using quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes, and market reference data. Level 2 assets consist of commercial paper, corporate securities and government agency securities. Level 2 inputs for the valuations are limited to quoted prices for similar assets or liabilities in active markets and inputs other than quoted prices that are observable for the asset. ​ Revenue Recognition The Company recognizes revenue from product sales in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price using the most likely method based on historical experience as well as applicable information currently available. Indirect taxes collected from customers and remitted to government authorities that are related to sales of the Company’s products, primarily in Europe, are excluded from revenues. Subsequent to the closing of the acquisition of Proleukin ® ® ® Stock-Based Compensation The Company periodically grants stock options to employees and non-employees as compensation for services rendered. The Company accounts for all stock-based payment awards made to employees, including the employee stock purchase plans, and non-employees in accordance with the authoritative guidance provided by the Financial Accounting Standards Board (“FASB”) where the value of the award is measured on the date of grant and recognized over the vesting period. Forfeitures are recognized in the period in which they occur. The Company accounts for stock option grants to non-employees in a similar manner as stock option grants to employees except for the term used in the grant date fair value, therefore no longer requiring a re-measurement at the then-current fair values at each reporting date until the shares underlying the options have vested. The non-employee awards that contain a performance condition that affects the quantity or other terms of the award are measured based on the outcome that is probable. The fair value of the Company's common stock option grants is estimated using a Black-Scholes option pricing model, which uses certain assumptions related to risk-free interest rates, expected volatility, expected term of the common stock options, and future dividends. The stock-based compensation expense is recorded based upon the value derived from the Black-Scholes option pricing model. The assumptions used in the Black-Scholes option pricing model could affect compensation expense recorded in future periods. The Company issues restricted stock units (“RSUs”) from time to time as part of its equity incentive plans. The Company measures the compensation cost with respect to RSUs issued to employees based upon the estimated fair value of the equity instruments at the date of the grant, which is recognized as an expense over the period during which an employee is required to provide services in exchange for the awards. The fair value of RSUs is based on the closing price of the Company’s common stock on the grant date. In addition to RSUs that have time-based vesting requirements, from time to time the Company may issue RSUs that include certain performance vesting criteria based upon the satisfaction of stated objectives (“PRSUs”). The Company measures the compensation cost with respect to PRSUs issued to employees based upon the estimated fair value of the equity instruments at the date of grant, which is recognized as an expense over the period that achievement is determined to be probable through the stated service period associated with the award. Accrued Research and Development Costs Research and development costs are expensed as incurred. Clinical development costs compose a significant component of research and development costs. The Company has a history of contracting with third parties, including contract research organizations (“CROs”), independent clinical investigators, and contract manufacturing organizations (“CMOs”) that perform various clinical trial activities on the Company’s behalf in connection with the ongoing development of the Company’s product candidates. The financial terms of these contracts are subject to negotiations and may vary from contract to contract and may result in uneven payment flow. The Company accrues and expenses costs for clinical trial activities performed by third parties based upon the work completed to date for each clinical trial in accordance with agreements established with CROs, hospitals, and clinical investigators. Accruals for CROs and CMOs are recorded based on services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. The Company determines its costs through discussions with internal clinical stakeholders and outside service providers as to the progress or stage of completion of clinical trials or services and the contracted fee to be paid for such services. ​ Included in the Company’s clinical development costs are investigator costs, which are costs associated with treatments administered at clinical sites as required under each clinical trial protocol. The Company’s determination of clinical investigator costs and related timing of expense recognition will depend on a number of factors that include, but are not limited to, (i) the overall number of patients that enroll in the trial at each individual site, (ii) the length of clinical trial enrollment period, (iii) discontinuation and completion rates of patients, (iv) duration of patient safety follow-ups, (v) the number of sites included in the clinical trial, and (vi) the contracted fee of each participating site for patient treatment while on clinical trial, which can vary greatly for several reasons including, but not limited to, geographic region, medical center or physician costs, and overhead costs. In addition, the Company’s estimates for per patient trial costs will vary based on a number of factors that include, but are not limited to, the extent of additional procedures that may be administered by investigators as a result of patient health status, recoverability of patient costs through insurance carriers of patients, and unanticipated cost of injuries incurred as a result of the clinical trial treatment. The Company accrues estimated expenses resulting from obligations under investigator site agreements as the timing of payments does not always timely align with the periods over which the treatments are administered by the clinical investigators. These estimates are typically based on contracted amounts, patient visit data, discussions with internal clinical stakeholders and outside service providers, and historical look-back analysis of actual payments made to date. ​ The Company makes judgements and estimates in determining the accrual balance in each reporting period. ​ In the event advance payments are made to a CRO, CMO or other outside service provider, the payments are recorded within prepaid expenses and other current assets in the Consolidated Balance Sheets and subsequently recognized as research and development expense in the consolidated statements of operations when the associated services have been performed. As actual costs become known, the Company adjusts its estimates, liabilities and assets. Inputs used in the determination of estimates discussed above may vary from actual, which will result in adjustments to research and development expense in future periods. ​ Selling, general and administrative expense Selling, general and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in executive, finance, procurement, legal, investor relations, facilities, business development, marketing, commercial, information technology and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses. Selling, general and administrative costs are expensed as incurred, and the Company accrues for services provided by third parties related to such expenses by monitoring the status of services provided and receiving estimates from its service providers and adjusting its accruals as actual costs become known. Income Taxes The Company accounts for income taxes using the asset and liability method whereby deferred tax assets are recognized for deductible temporary differences, and deferred tax liabilities are recognized for taxable temporary differences. Temporary differences are the differences between the reported amounts of assets and liabilities and their tax bases. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some or all of the deferred tax assets will not be realized. Deferred tax assets and liabilities are adjusted for the effects of changes in tax laws and rates on the date of enactment. ASC Topic 740, Income Taxes Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of shares of common stock outstanding and the dilutive common stock equivalent outstanding during the period. The Company’s potentially dilutive common stock equivalent shares, which include incremental common shares issuable upon (i) the exercise of outstanding stock options, (ii) purchases though the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), (iii) vesting of restricted stock units, and (vi) conversion of preferred stock, are only included in the calculation of diluted net loss per share when their effect is dilutive. As of December 31, 2023, 2022, and 2021, the following outstanding common stock equivalents have been excluded from the calculation of net loss per share because their impact would be anti-dilutive. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2023 2022 2021 Stock options ​ 18,899,849 15,240,197 12,520,865 Employee Stock Purchase Plan ​ 296,751 ​ 260,859 ​ 85,227 Restricted stock units ​ 3,453,901 ​ 2,436,764 ​ 1,110,010 Series A Convertible Preferred Stock* ​ 97,000 ​ 97,000 ​ 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 2,842,158 2,842,158 ​ ​ 25,589,659 20,876,978 16,655,260 *on an as-converted basis The dilutive effect of potentially dilutive securities would be reflected in diluted earnings per common share by application of the treasury stock method. Under the treasury stock method, an increase in the fair market value of the Company's common stock could result in a greater dilutive effect from potentially dilutive securities. ​ Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include assumptions made in the fair value of intangible assets, inventories acquired as part of the acquisition of Proleukin ® , equity awards and related stock-based compensation, assumptions used in measuring operating right-of-use assets and operating lease liabilities, accounting for potential liabilities, including estimates inherent in accruals related to clinical trials, and the realizability of the Company’s deferred tax assets . Principles of Consolidation The accompanying consolidated financial statements include the accounts of Iovance Biotherapeutics, Inc. and its wholly-owned subsidiaries, Iovance Biotherapeutics Manufacturing LLC, Iovance Biotherapeutics GmbH, and Iovance Biotherapeutics B.V., Iovance Biotherapeutics UK Ltd and Iovance Biotherapeutics UK SP Ltd (together, the “UK subsidiaries”), and Iovance Biotherapeutics Canada, Inc. All intercompany accounts and transactions have been eliminated. Certain prior year amounts in the notes to these consolidated financial statements have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the previously reported consolidated balance sheets, consolidated statements of operations, consolidated statements of other comprehensive loss, consolidated statements of stockholder’s equity or consolidated statements of cash flows. ​ Foreign Currency Translation The assets and liabilities of the Company’s subsidiaries whose functional currencies are not in U.S. dollars are translated into U.S. dollars at the related period-end exchange rate. The U.S. dollar effects that arise from translation of net assets of these subsidiaries at changing rates are recognized in Accumulated Other Comprehensive Income (Loss) in the consolidated balance sheets. The subsidiaries’ net loss is translated into U.S. dollars by using the average exchange rate for the applicable period. The consolidated financial statements are presented in U.S. dollars, which is the Company’s reporting currency. Segment Reporting The Company operates in one segment, focused on developing and commercializing therapies using autologous TIL for the treatment of metastatic melanoma and other solid tumor cancers. Concentrations The Company is subject to credit risk from its portfolio of cash, cash equivalents and investments. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. The Company does not believe it is exposed to any significant concentrations of credit risk from these financial instruments. The Company maintains cash, cash equivalents and investment balances at four financial institutions. Management believes that the financial institutions which hold its cash are financially sound and, accordingly, minimal credit risk exists. As of December 31, 2023 and 2022, respectively, the Company’s cash balances were in excess of insured limits maintained at the financial institutions. Recent Accounting Standards Issued But Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures of income taxes. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of ASU 2023-09 on its consolidated financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which enhances the disclosures required for operating segments in annual and interim consolidated financial statements. ASC 2023-07 is effective for the Company in its annual reporting for fiscal year 2024 and for interim period reporting beginning in fiscal year 2025 on a retrospective basis. Early adoption is permitted. The Company is currently evaluating the impact of ASC 2023-07 on its consolidated financial statements.

CASH EQUIVALENTS AND INVESTMENT

CASH EQUIVALENTS AND INVESTMENTS	12 Months Ended
	Dec. 31, 2023
CASH EQUIVALENTS AND INVESTMENTS
CASH EQUIVALENTS AND INVESTMENTS	NOTE 3. CASH EQUIVALENTS AND INVESTMENTS The amortized cost and fair value of cash equivalents and investments as of December 31, 2023 and December 31, 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2023 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 164,940 ​ $ 39 ​ $ — ​ $ 164,979 Money market funds ​ ​ 34,053 ​ ​ — ​ ​ — ​ ​ 34,053 Total investments ​ $ 198,993 ​ $ 39 ​ $ — ​ $ 199,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2022 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 118,570 ​ $ — ​ $ (850) ​ $ 117,720 U.S. government agency securities ​ 11,272 ​ — ​ (7) ​ 11,265 Corporate securities ​ ​ 7,230 ​ ​ — ​ ​ — ​ ​ 7,230 Commercial paper ​ ​ 148,299 ​ ​ 8 ​ ​ (53) ​ ​ 148,254 Money market funds ​ ​ 88,001 ​ ​ — ​ ​ — ​ ​ 88,001 Total investments ​ $ 373,372 ​ $ 8 ​ $ (910) ​ $ 372,470 ​ The fair value of cash equivalents and investments as of December 31, 2023 and December 31, 2022 are classified as follows in the Company’s consolidated balance sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, Classified as: ​ 2023 2022 Cash equivalents ​ $ 34,053 ​ $ 132,356 Short-term investments ​ ​ 164,979 ​ ​ 240,114 Total investments ​ $ 199,032 ​ $ 372,470 ​ Cash equivalents in the tables above exclude cash demand deposits of $80.8 million and $99.4 million as of December 31, 2023 and 2022, respectively. Unrealized gains and losses are included in accumulated other comprehensive (loss) income, and as of December 31, 2023 and 2022 no unrealized losses on available-for-sale securities have resulted from credit risk. All available-for-sale securities held as of December 31, 2023 and December 31, 2022 had contractual maturities of less than one year. No significant available-for-sale securities held as of the periods presented have been in a continuous unrealized loss position for more than 12 months. To date, the Company has not recorded any impairment charges on its investments. ​ Recurring Fair Value Measurements ​ As of December 31, 2023 and 2022, the fair value of the Company’s financial assets that are measured at fair value on a recurring basis, which consist of cash equivalents and short-term and long-term investments classified as available-for-sale securities, are categorized in the table below based upon the lowest level of significant input to the valuations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2023 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 164,979 ​ $ — ​ $ — ​ $ 164,979 Money market funds ​ ​ 34,053 ​ ​ — ​ ​ — ​ ​ 34,053 Total ​ $ 199,032 ​ $ — ​ $ — ​ $ 199,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2022 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 117,720 ​ $ — ​ $ — ​ $ 117,720 U.S. government agency securities ​ — ​ 11,265 ​ — ​ 11,265 Corporate securities ​ ​ — ​ ​ 7,230 ​ ​ — ​ ​ 7,230 Commercial paper ​ ​ — ​ ​ 148,254 ​ ​ — ​ ​ 148,254 Money market funds ​ ​ 88,001 ​ ​ — ​ ​ — ​ ​ 88,001 Total ​ $ 205,721 ​ $ 166,749 ​ $ — ​ $ 372,470 ​ Level 2 assets consist of commercial paper and government agency securities. Level 2 inputs for the valuations are limited to quoted prices for similar assets or liabilities in active markets and inputs other than quoted prices that are observable for the asset.

PROLEUKIN ACQUISITION

PROLEUKIN ACQUISITION	12 Months Ended
	Dec. 31, 2023
PROLEUKIN ACQUISITION
PROLEUKIN ACQUISITION	NOTE 4. PROLEUKIN ® ACQUISITION On January 23, 2023, the Company and its newly formed, wholly owned subsidiary, Iovance Biotherapeutics UK Ltd (the “Purchaser”) entered into an Option Agreement (the “Option Agreement”) with Clinigen Holdings Limited, Clinigen Healthcare Limited, and Clinigen, Inc. (collectively “Clinigen”), a global pharmaceutical services company, pursuant to which the Purchaser would acquire the worldwide rights for the manufacturing, supply, commercialization and sale of Proleukin ® ​ On May 18, 2023, the Company completed the Acquisition and specifically acquired (i) all issued and outstanding shares of Clinigen SP Limited (the “Target”), (ii) the business of the Target and Clinigen (the “Proleukin ® ​ The Acquisition was accounted for as an asset acquisition because substantially all of the fair value of the acquired assets was concentrated in the acquired developed technology related to the intellectual property rights of Proleukin ® ® ​ The following table summarizes the total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ Amounts Cash ​ $ 35 Inventory ​ ​ 9,688 Developed technology ​ ​ 232,665 Assembled workforce ​ ​ 636 Deferred tax liability ​ ​ (20,352) Total cost of acquisition ​ $ 222,672 ​ The $222.7 million of total cost of the Acquisition consisted of (i) a $210.2 million of cash payment to Clinigen and (ii) $12.5 million of direct transaction costs incurred by the Company. The Option Agreement additionally provides for contingent cash payments consisting of (i) a milestone payment of £41.7 million, or approximately $50.0 million, upon first approval of lifileucel in advanced melanoma, (ii) deferred consideration based on double digit rates on global net sales (as defined in the Option Agreement) payable from the Company to the sellers following the completion of the Acquisition over a deferred consideration term of twelve years, and (iii) after the deferred consideration term, earnout payments payable from the Company to sellers following the completion of the transaction if deferred consideration payments are equal or greater than the deferred consideration amount provided for in the Option Agreement. These contingent payments were determined to be within the scope of ASC 450 and will be recognized when they are both probable and estimable. The recognition criteria have not been met as of the acquisition date or as of December 31, 2023. ​ The net assets acquired in the Acquisition were recorded by allocating the total cost of the Acquisition to the assets acquired on a relative fair value basis based on their estimated fair values as of May 18, 2023, which is the date that the Acquisition was completed. ​ The fair value of the developed technology was estimated using a multi-period excess earnings income approach that discounts expected cash flows to present value by applying a discount rate that represents the estimated rate that market participants would use to value the intangible assets. The fair value of the developed technology is being amortized over an expected useful life of 15 years and is recorded as Cost of Sales in the Company’s consolidated statement of operations. ​ The fair value of the assembled workforce was estimated using a replacement cost less depreciation method. The fair value of the assembled workforce is being amortized over an expected useful life of 3 years and is recorded as Selling, General and Administrative expense in the Company’s consolidated statement of operations. ​ The fair value of the acquired inventory was determined using the comparative sales method of the market approach, which uses historical and expected average selling prices of inventory as the base amount to which adjustment for costs to complete for work-in-process, cost of disposal and reasonable profit allowance are applied. The inventory fair value adjustment is being amortized as cost of sales as the acquired inventories are sold. ​ A deferred tax liability was recognized on the temporary differences related to the book and tax basis of the acquired intangible assets. The deferred tax liability and resulting adjustment to the carrying amount of the acquired intangibles was calculated using the simultaneous equations method under ASC 740. The tax rate used is based on the estimated statutory rates in the United Kingdom as this is where the intangible assets are domiciled.

INTANGIBLE ASSETS, NET

INTANGIBLE ASSETS, NET	12 Months Ended
	Dec. 31, 2023
INTANGIBLE ASSETS, NET
INTANGIBLE ASSETS, NET	NOTE 5. INTANGIBLE ASSETS, NET The gross carrying amounts and net book value of intangible assets as of December 31, 2023 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ Gross carrying amounts Accumulated amortization Intangible assets, net Intangible assets: ​ ​ ​ ​ ​ ​ ​ Developed technology ​ $ 238,612 $ (9,871) $ 228,741 Assembled workforce ​ ​ 652 ​ (135) ​ 517 Total Intangible Assets ​ $ 239,264 $ (10,006) $ 229,258 * Amounts are translated using the foreign exchange rate as of 12/31/2023. ​ ​ ​ ​ ​ ​ ​ ​ The Company recognized amortization expense of $9.9 million during the year ended December 31, 2023. Amortization expense for the developed technology and assembled workforce is recorded in Cost of sales and Selling, general and administrative expense, respectively, in the consolidated statement of operations for the year ended December 31, 2023. There was no such expense recorded in the year ended December 31, 2022. ​ The total estimated amortization of the Company’s intangible assets the years ending December 31, 2024, 2025, 2026, 2027 and 2028 are $16.1 million, $16.1 million, $16.0 million, $15.9 million, and $15.9 million, respectively.

INVENTORY

INVENTORY	12 Months Ended
	Dec. 31, 2023
INVENTORY
INVENTORY	NOTE 6. INVENTORY Inventory presented in the consolidated balance sheet as of December 31, 2023 pertains solely to Proleukin ® ® As of December 31, 2023 and December 31, 2022, inventory consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, ​ ​ ​ 2023 ​ ​ 2022 Work in process ​ $ 5,749 ​ $ — Finished goods ​ ​ 4,623 ​ ​ — Total inventory ​ $ 10,372 ​ $ — ​

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2023
REVENUE
REVENUE	​ NOTE 7. REVENUE Product sales for the year ended December 31, 2023 was $1.2 million and represented sales of Proleukin ® product sales ®

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2023
PROPERTY AND EQUIPMENT, NET
PROPERTY AND EQUIPMENT, NET	NOTE 8. PROPERTY AND EQUIPMENT, NET Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Leasehold improvements ​ $ 76,804 ​ $ 74,305 Lab, process, and validation equipment ​ ​ 23,131 ​ ​ 22,136 Utility equipment ​ 5,990 ​ 5,951 Office furniture and equipment ​ 3,297 ​ 2,927 Computer software ​ ​ 7,772 ​ ​ 6,736 Computer equipment ​ 542 ​ 695 Machinery and equipment ​ ​ 306 ​ ​ 82 Construction in progress ​ 24,101 ​ 9,118 Total property and equipment, cost ​ 141,943 ​ 121,950 Less: Accumulated depreciation and amortization ​ (27,913) ​ (16,718) Property and equipment, net ​ $ 114,030 ​ $ 105,232 ​ Depreciation expense for the years ended December 31, 2023, 2022, and 2021 was approximately $11.6 million, $9.3 million and $3.1 million, respectively. During the years ended December 31, 2023 and 2022, the Company placed $2.6 million and $27.2 million of assets related to the i

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2023
ACCRUED EXPENSES
ACCRUED EXPENSES	NOTE 9. ACCRUED EXPENSES Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2023 2022 Employee and consultant related expenses ​ $ 34,814 ​ $ 20,188 Clinical related ​ ​ 10,911 ​ ​ 14,812 Manufacturing related ​ 10,893 ​ 4,467 Facilities related ​ ​ 2,437 ​ ​ 6,510 Legal and related services ​ 1,610 ​ 3,015 Inventory related ​ ​ 2,148 ​ ​ — Other accrued expenses ​ 6,593 ​ 3,303 Total accrued expenses ​ $ 69,406 ​ $ 52,295 ​

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2023
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 10. STOCKHOLDERS’ EQUITY Common Stock The Company’s certificate of incorporation, as amended, authorizes the issuance of up to 500,000,000 shares of the Company’s common stock, par value $0.000041666 . As of December 31, 2023, 256,135,715 shares of the Company’s common stock were issued and outstanding . Public Offerings On July 13, 2023, the Company closed an underwritten public offering of 23,000,000 shares of the Company’s common stock, which included 3,000,000 shares of common stock issued pursuant to the exercise of the option granted to the underwriters, at a public offering price of $7.50 per share, before underwriting discounts and commissions. The total net proceeds to the Company from the offering, including the exercise of the option by the underwriters, were $161.5 million after deducting underwriting discounts and commissions and offering expenses payable by the Company. At the Market Offering Program On November 18, 2022, the Company entered into an Open Market Sale Agreement (the “2022 Sale Agreement”) with Jefferies LLC (“Jefferies”). Under the terms of the 2022 Sale Agreement, the Company was able to, from time to time, at its sole discretion, issue and sell through Jefferies, acting as a sales agent, up to $500.0 million of shares of the Company’s common stock. On June 16, 2023, the Company entered into a new Open Market Sale Agreement (the “2023 Sale Agreement”), which superseded and replaced in its entirety the 2022 Sale Agreement, which was terminated by the Company. Under the terms of the 2023 Sale Agreement, the Company may, from time to time, in its sole discretion, issue and sell through Jefferies, acting as a sales agent, up to $450.0 million of shares of the Company’s common stock. The issuance and sale, if any, of the shares of common stock by the Company under the 2023 Sale Agreement was or will be made pursuant to a prospectus supplement dated June 16, 2023 to the Company’s Registration Statement on Form S-3ASR, which became effective immediately upon filing with the SEC on June 16, 2023. Pursuant to the 2023 Sale Agreement, Jefferies may sell the Common Shares by any method permitted by law deemed to be an “at the market” offering as defined in Rule 415 of the Securities Act of 1933, as amended. Jefferies will use commercially reasonable efforts consistent with its normal trading and sales practices to sell the Common Shares from time to time, based upon instructions from the Company (including any price or size limits or other customary parameters or conditions the Company may impose). The Company will pay Jefferies a commission of up to 3.0% of the gross sales proceeds of any Common Shares sold through Jefferies under the 2023 Sale Agreement. The Company is not obligated to make any sales of Common Shares under the 2023 Sale Agreement. The offering of Common Shares pursuant to the 2023 Sale Agreement will terminate upon the earlier to occur of (i) the issuance and sale, through Jefferies, of all Common Shares subject to the 2023 Sale Agreement and (ii) termination of the 2023 Sale Agreement in accordance with its terms. For the years ended December 31, 2023 and 2022, the Company received $301.7 million and $189.5 million in net proceeds, net of offering costs, through the sale of 44,080,226 shares and 29,788,993 shares of its common stock through the 2023 Sale Agreement and/or the 2022 Sale Agreement at a weighted average price per share of $6.99 and $6.52, respectively. Preferred Stock The Company’s certificate of incorporation authorizes the issuance of up to 50,000,000 shares of “blank check” preferred stock. As of December 31, 2023, 17,000 shares were designated as Series A Convertible Preferred Stock and 11,500,000 shares were designated as Series B Convertible Preferred Stock. Series A Convertible Preferred Stock A total of 17,000 shares of Series A Convertible Preferred Stock have been authorized for issuance under the Company’s Certificate of Designation of Preferences and Rights of Series A Convertible Preferred Stock. The shares of Series A Convertible Preferred Stock have a stated value of $1,000 per share and are initially convertible into shares of common stock at a price of $2.00 per share, subject to adjustment. Each share of Series A Preferred Stock is initially convertible into 500 shares of common stock. The Series A Convertible Preferred Stock may, at the option of each investor, be converted into fully paid and non-assessable shares of common stock. The holders of shares of Series A Convertible Preferred Stock do not have the right to vote on matters that come before the Company’s stockholders. In the event of any dissolution or winding up of the Company, proceeds shall be paid pari passu among the holders of common stock and preferred stock, pro rata based on the number of shares held by each holder. The Company may not declare, pay or set aside any dividends on shares of capital stock of the Company (other than dividends on shares of common stock payable in shares of common stock) unless the holders of the Series A Convertible Preferred Stock shall first receive an equal dividend on each outstanding share of Series A Convertible Preferred Stock. No shares of Series A Convertible Preferred Stock were converted to common stock during the year ended December 31, 2023 and 2022. As of December 31, 2023, and 2022, 194 shares of Series A Convertible Preferred Stock (that are convertible into 97,000 shares of common stock) remained outstanding. Series B Convertible Preferred Stock ​ A total of 11,500,000 shares of Series B Convertible Preferred Stock are authorized for issuance under the Company’s Series B Certificate of Designation of Rights, Preferences and Privileges of Series B Convertible Preferred Stock. The shares of Series B Convertible Preferred Stock have a stated value of $4.75 per share and are convertible into shares of the Company’s common stock at an initial conversion price of $4.75 per share. Each share of Series B Preferred Stock is initially convertible into 1 share of common stock. The Series B Convertible Preferred Stock may, at the option of each investor, be converted into fully paid and non-assessable shares of common stock. The holders of Series B Convertible Preferred Stock do not have the right to vote on matters that come before the Company's stockholders. In the event of any dissolution or winding up of the Company, proceeds shall be paid pari passu among the holders of common stock and preferred stock, pro rata based on the number of shares held by each holder. Holders of Series B Convertible Preferred Stock are entitled to dividends on an as-if-converted basis in the same form as any dividends actually paid on shares of the Series A Convertible Preferred Stock or the Company’s common stock. So long as any Series B Convertible Preferred Stock remains outstanding, the Company may not redeem, purchase or otherwise acquire any material amount of the Series A Convertible Preferred Stock or any securities junior to the Series B Convertible Preferred Stock. No shares of Series B Convertible Preferred Stock were converted to common stock during the year ended December 31, 2023 and 2022. At December 31, 2023 and 2022, 2,842,158 shares of Series B Preferred Stock (that are convertible into 2,842,158 shares of common stock) remained outstanding. Equity Incentive Plans The Company has multiple equity incentive plans under which it grants awards. As of December 31, 2023, there are 275,625 shares available to grant under the 2014 Equity Incentive Plan (the “2014 Plan”). On April 22, 2018, the Company’s Board of Directors (the “Board”) adopted the Iovance Biotherapeutics, Inc. 2018 Equity Incentive Plan (the “2018 Plan”), which was approved by the Company’s stockholders in June 2018. The 2018 Plan as approved initially authorized the issuance up to an aggregate of 6,000,000 shares of common stock in the form of incentive (qualified) stock options, non-qualified options, common stock, stock appreciation rights, restricted stock awards, restricted stock units, other stock-based awards, other cash-based awards or any combination of the foregoing. On June 8, 2020, the Company's stockholders approved an amendment to the 2018 Plan to increase the number of shares available for issuance upon the exercise of stock options under the 2018 Plan from 6,000,000 to 14,000,000 shares, which became effective immediately. Additionally, on June 10, 2022, the Company’s stockholders approved an amendment to the 2018 Plan to increase the number of shares available for issuance upon the exercise of stock options under the 2018 Plan from 14,000,000 to 20,700,000 shares, which became effective immediately. On June 6, 2023, the Company’s stockholders approved an amendment to the 2018 Plan to increase the number of shares available for issuance under the 2018 Plan from 20,700,000 to 29,700,000, which became effective immediately. As of December 31, 2023, 9,906,666 shares of common stock were available for grant under the Company’s 2018 Plan. On September 22, 2021, the Board adopted the Iovance Biotherapeutics, Inc. 2021 Inducement Plan (the “2021 Inducement Plan”). The 2021 Inducement Plan provides for the grant of non-qualified options, common stock, stock appreciation rights, restricted stock awards, restricted stock units, other stock-based awards, other cash-based awards, or any combination of the foregoing. The 2021 Inducement Plan was recommended for approval by the Compensation Committee of the Board (the “Compensation Committee”), and subsequently approved and adopted by the Board without stockholder approval pursuant to Rule 5635(c)(4) of the rules and regulations of The Nasdaq Stock Market LLC (the “Nasdaq Listing Rules”). The Board initially reserved 1,000,000 shares of the Company’s common stock for issuance pursuant to equity awards granted under the 2021 Inducement Plan, and the 2021 Inducement Plan is administered by the Compensation Committee. On January 12, 2022, the Compensation Committee approved an amendment to the 2021 Inducement Plan solely to increase the number of shares reserved for issuance under the 2021 Inducement Plan from 1,000,000 shares of the Company’s common stock to 1,750,000 shares of the Company’s common stock without stockholder approval pursuant to Rule 5635(c)(4) of the Nasdaq Listing Rules. On March 13, 2023, the Compensation Committee approved an additional amendment to the 2021 Inducement Plan solely to increase the number of shares reserved for issuance under the 2021 Inducement Plan from 1,750,000 shares of the Company’s common stock to 2,250,000 shares of the Company’s common stock without stockholder approval pursuant to Rule 5635(c)(4) of the Nasdaq Listing Rules. In accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules, equity awards under the 2021 Inducement Plan may only be made to an employee if such employee is granted such equity awards in connection with his or her commencement of employment with the Company or a subsidiary and such grant is an inducement material to his or her entering into employment with the Company or such subsidiary. In addition, awards under the 2021 Inducement Plan may only be made to employees who have not previously been an employee or member of the Board (or any parent or subsidiary of the Company) or following a bona fide period of non-employment of the employee by the Company (or a parent or subsidiary of the Company). As of December 31, 2023, 349,428 shares of common stock were available for grant under the Inducement Plan. Stock Options A summary of the status of stock options as of December 31, 2023, and the changes during the three years then ended, is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ Aggregate ​ ​ Number ​ Average ​ Remaining ​ Intrinsic ​ ​ of ​ Exercise ​ Contract ​ Value ​ Options Price Life (in thousands) Outstanding at December 31, 2022 ​ 15,240,197 $ 22.45 ​ ​ ​ ​ ​ Issued ​ 5,379,670 ​ 7.04 ​ ​ ​ ​ ​ Exercised ​ (8,860) ​ 7.10 ​ ​ ​ ​ ​ Expired/Cancelled ​ (1,711,158) ​ 17.01 ​ ​ ​ ​ ​ Outstanding at December 31, 2023 ​ 18,899,849 $ 18.57 6.75 ​ $ 7,065 Ending vested and expected to vest at December 31, 2023 ​ 18,899,849 ​ $ 18.57 ​ 6.75 ​ $ 7,065 Options exercisable at December 31, 2023 12,160,135 ​ $ 23.40 5.54 ​ $ 1,337 ​ As of December 31, 2023, there was $31.7 million of total unrecognized compensation expense related to unvested employee stock options, which the Company expects to recognize over a remaining weighted average period of 1.84 years. The weighted average grant date fair value for employee options granted under the Company's stock option plans during the years ended December 31, 2023, 2022, and 2021 was $4.91, $8.29, and $22.28 per option, respectively. The aggregate intrinsic value in the table above reflects the total pre-tax intrinsic value (the difference between the Company’s closing stock price on the last trading day of the year ended December 31, 2023 and the exercise price of the options, multiplied by the number of in-the-money stock options) that would have been received by the option holders had all option holders exercised their options on December 31, 2023. The intrinsic value of the Company’s stock options changes based on the closing price of the Company’s common stock. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2023, 2022, and 2021 were $0.01 million, $0.04 million, and $21.3 million, respectively. Employee Stock Purchase Plan In June 2020, the Company adopted the 2020 ESPP upon its approval by the Company’s shareholders at its Annual Stockholders Meeting on June 8, 2020. The Company reserved 500,000 shares of its common stock for issuance under the 2020 ESPP. On June 6, 2023, the Company's stockholders approved an amendment to the 2020 ESPP to increase the number of shares reserved for issuance under the 2020 ESPP from 500,000 shares of the Company’s common stock to 1,400,000 shares of the Company’s common stock, which became effective immediately. ​ Under the 2020 ESPP, employees of the Company can purchase shares of our common stock based on a percentage of their compensation subject to certain limits. The purchase price per share is equal to the lower of 85% of the fair market value of its common stock on the offering date or the purchase date with a six-month look-back feature. The 2020 ESPP purchases are settled with common stock from the 2020 ESPP’s previously authorized and available pool of shares. The compensation expense related to the 2020 ESPP for the years ended December 31, 2023, 2022 and 2021 was $1.2 million, $1.3 million and $1.2 million, respectively. Under the 2020 ESPP, for the years ended December 31, 2023 and 2022, the Company received proceeds of $2.4 million for the issuance of 435,459 shares and $1.7 million for the issuance of 262,701 shares, respectively. As of December 31, 2023, there was $0.6 million of unrecognized compensation cost associated with the 2020 ESPP, which is expected to be recognized over 5.4 months. ​ Restricted Stock Units and Performance Restricted Stock Units ​ In addition to RSUs that have time-based vesting requirements, from time to time the Company may issue RSUs that include certain performance vesting criteria based upon the satisfaction of stated objectives (“PRSUs”). Compensation expense related to PRSUs is based on the grant date fair value of the award and recorded from the period that achievement is determined to be probable through the stated service period associated with the award. Activity for RSUs and PRSUs during the years ended December 31, 2023 and 2022 is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ Number ​ Average ​ ​ ​ of ​ Grant Date ​ ​ RSUs and PRSUs Fair Value ​ Outstanding, non-vested as of December 31, 2022 ​ 2,436,764 ​ $ 14.74 ​ Granted ​ 2,729,348 ​ ​ 7.19 ​ Vested/Released ​ (1,253,465) ​ ​ 16.17 ​ Canceled/Forfeited ​ (458,746) ​ ​ 9.35 ​ Outstanding as of December 31, 2023 ​ 3,453,901 ​ $ 8.97 ​ Ending vested and expected to vest at December 31, 2023 ​ 3,453,901 ​ $ 8.97 ​ ​ As of December 31, 2023 and 2022, there was $19.9 million and $20.6 million of unrecognized stock-based compensation expense associated with unvested RSUs, which the Company expects to recognize over a remaining weighted-average period of 1.65 and 1.72 years, respectively. The aggregate intrinsic value of the unvested RSUs and PRSUs outstanding as of December 31, 2023 and 2022, was $28.1 million and $14.5 million, respectively. ​ Stock-Based Compensation Total stock-based compensation expense related to the Company’s stock-based awards was recorded on the consolidated statements of operations as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 2022 2021 Research and development ​ $ 34,926 ​ $ 50,242 ​ $ 40,833 Selling, general and administrative ​ 27,699 ​ 33,780 ​ 28,932 Total stock-based compensation expense ​ $ 62,625 ​ $ 84,022 ​ $ 69,765 ​ Total stock-based compensation expense by type of award was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 2022 2021 Stock option expense ​ $ 45,340 ​ $ 58,308 ​ $ 56,305 Restricted stock expense ​ 16,062 ​ 24,436 ​ 12,247 ESPP expense ​ 1,223 ​ 1,278 ​ 1,213 Total stock-based compensation expense ​ $ 62,625 ​ $ 84,022 ​ $ 69,765 ​ The following table summarizes the assumptions relating to options granted pursuant to the Company’s equity incentive plans for the years ended December 31, 2023, 2022, and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock Option ​ ESPP ​ ​ Years Ended December 31, ​ Years Ended December 31, Assumptions: 2023 2022 2021 2023 2022 2021 Expected term (years) ​ 5.18 - 5.37 4.94 - 5.12 4.94 - 5.28 ​ 0.5 ​ 0.50 ​ 0.50 Expected volatility ​ 83.63% - 84.21% 73.73% - 83.90% 70.35% - 73.88% ​ 72.96% - 83.36% ​ 73.02% - 137.42% ​ 52.04% - 94.56% Risk-free interest rate ​ 3.59% - 4.60% ​ 1.25% - 4.05% ​ 0.36% - 0.97% ​ 5.38% - 5.40% ​ 1.98% - 4.78% ​ 0.06% - 0.13% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ 0% ​ 0% ​ 0% ​ - Expected Term (Years) —The expected term of the stock option grants was calculated based on historical exercises, cancellations, and forfeitures of stock options and outstanding option shares. - Expected Volatility —The expected volatility is based on the historical volatility for the Company's stock over a period equal to the expected terms of the options. - Risk-Free Interest Rate —The risk-free interest rate was based on the market yield currently available on United States Treasury securities with maturities approximately equal to the option’s expected term. - Expected Dividend Yield —The Company has never paid dividends and does not expect to pay dividends in the foreseeable future. - Forfeiture Rate —The Company recognizes forfeitures as they occur. Each of the inputs discussed above is subjective and generally requires significant management judgment.

EMPLOYEE BENEFIT PLAN

EMPLOYEE BENEFIT PLAN	12 Months Ended
	Dec. 31, 2023
EMPLOYEE BENEFIT PLAN
EMPLOYEE BENEFIT PLAN	NOTE 11. EMPLOYEE BENEFIT PLAN The Company maintains a defined contribution plan covering substantially all U.S. employees under Section 401(k) of the Internal Revenue Code of 1986, as amended (the “IRC”). The Company's matching contribution to the defined contribution plan was $4.1 million, $3.0 million, and $2.2 million for the years ended December 31, 2023, 2022 and 2021, respectively. ​

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
INCOME TAXES	NOTE 12. INCOME TAXES The Company recorded an income tax benefit of $3.5 million for the year ended December 31, 2023, but did not record a provision or benefit for income taxes for the years ended December 31, 2022 or 2021. Upon the completion of the Acquisition on May 18, 2023, a deferred tax liability of $20.4 million was recognized on the temporary differences related to the book and tax basis of the acquired intangible assets. The deferred tax liability and resulting adjustment to the carrying amount of the acquired intangibles was calculated using the simultaneous equations method under ASC 740. The tax rate used is based on the estimated statutory rates in the United Kingdom as this is where the intangible assets are domiciled. The Company recorded a tax benefit of $3.5 million for the year ended December 21, 2023, which resulted in an effective tax rate of 0.78%. The effective tax rate is different from U.S. statutory rate of 21% due to the full valuation allowance against tax losses in the U.S. The income tax benefit for the periods presented primarily relates to operations in the United Kingdom and the movement of deferred tax assets and liabilities. The significant components of the Company’s net deferred tax assets and liabilities are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2023 2022 Deferred income tax assets: ​ ​ Net operating loss carryforwards ​ $ 255,639 ​ $ 225,904 Stock-based compensation ​ 28,609 ​ 24,920 Tax credit carryforwards ​ 58,565 ​ 46,957 Lease liabilities ​ ​ 16,024 ​ ​ 18,017 Capitalized R&D ​ ​ 99,107 ​ ​ 47,755 Reserves and accruals ​ 6,540 ​ 3,997 Deferred tax assets before valuation allowance ​ 464,484 ​ 367,550 Less: valuation allowance ​ (446,853) ​ (350,418) Net deferred income tax assets ​ 17,631 ​ 17,132 Deferred tax liabilities: ​ ​ ​ ​ Right-of-use assets ​ (13,381) ​ (15,578) Depreciation and amortization ​ (21,597) ​ (1,554) Net deferred tax assets (liabilities) ​ $ (17,347) ​ $ — ​ The reconciliation of the effective income tax rate to the U.S. statutory rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended December 31, ​ 2023 2022 2021 ​ Federal statutory tax rate 21% ​ 21% ​ 21% ​ Orphan drug and research credits 2% 1% 2% ​ Permanent and other differences (1)% (1)% 0% ​ Stock Based Compensation (1)% (1)% 0% ​ State tax, net of federal benefit 1% 1% 0% ​ ​ 22% ​ 21% ​ 23% ​ Valuation allowance (21)% ​ (21)% ​ (23)% ​ Effective tax rate 1% ​ 0% ​ 0% ​ ​ The Company had net operating loss carryforwards (“NOLs”) for federal and state income tax purposes of approximately $1.2 billion and $180 million, respectively, as of December 31, 2023. $142.4 million of federal NOLs will expire beginning in 2027, while $1.0 billion generated after the recently enacted tax reform will have an indefinite life under the Tax Cuts and Jobs Act of 2017 (the “Tax Act”). The state NOLs will expire if unused in years 2030 through 2043. The Company’s utilization of NOLs is subject to an annual limitation due to ownership changes that have occurred previously or that could occur in the future as provided in Section 382 of the Internal Revenue Code (“Section 382”), as well as similar state provisions. Section 382 limits the utilization of NOLs when there is a greater than 50% change of ownership as determined under the regulations. Since its formation, the Company has raised capital through the issuance of capital stock and various convertible instruments which, combined with the purchasing shareholders’ subsequent disposition of these shares, has resulted in multiple ownership changes as defined by Section 382, and could result in ownership change in the future upon subsequent disposition. The Company’s utilization of NOLs may also be adversely affected by future changes in federal and state tax laws and regulations. In assessing the realization of U.S. deferred tax assets, management considers whether it is more likely than not that some portion or all the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon future generation for taxable income during the periods in which temporary differences representing net future deductible amounts become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. After consideration of all the information available, management continues to maintain a full valuation allowance against U.S. federal and state net deferred tax assets as it expected to be in a cumulative loss position and does not have sufficient positive evidence to support the realizability of its U.S. net deferred tax assets For the years ended December 31, 2023, 2022 and 2021, the change in the valuation allowance was approximately $96.4 million, $82.9 million, and $78.1 million, respectively. For the year ended December 31, 2023, the Company recorded approximately $17.3 million of net deferred tax liability from its operation in the United Kingdom. The basis difference resulted from acquisition of Proleukin business. The Company evaluated the provisions of ASC 740 related to the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements. ASC 740 prescribes a comprehensive model for how a company should recognize, present, and disclose uncertain positions that the Company has taken or expects to take in its tax return. For those benefits to be recognized, a tax position must be more-likely-than-not to be sustained upon examination by taxing authorities. Differences between tax positions taken or expected to be taken in a tax return and the net benefit recognized and measured pursuant to the interpretation are referred to as “unrecognized benefits.” A liability is recognized (or amount of net operating loss carry forward or amount of tax refundable is reduced) for unrecognized tax benefit because it represents an enterprise’s potential future obligation to the taxing authority for a tax position that was not recognized as a result of applying the provisions of ASC 740. If applicable, interest costs related to the unrecognized tax benefits are required to be calculated and would be classified as income tax expenses in the consolidated statements of operations. Penalties would be recognized as a component of “General and Administrative Expenses” in the consolidated statements of operations. A reconciliation of the beginning and ending balances of the unrecognized tax benefits during the years ended December 31, 2023, 2022 and 2021 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2023 2022 2021 Unrecognized benefit - beginning of period ​ $ 21,645 ​ $ 18,171 ​ $ 14,432 Gross decreases - prior period tax positions ​ — ​ — ​ (159) Gross increase current period tax positions ​ 4,462 ​ 3,474 ​ 3,898 Unrecognized benefit - end of period ​ $ 26,107 ​ $ 21,645 ​ $ 18,171 ​ No interest or penalties on unpaid tax were recorded during the years ended December 31, 2023, 2022, or 2021. The Company does not anticipate any significant changes within 12 months of this reporting date of its uncertain tax positions. The Company files tax returns in the U.S. federal and state jurisdictions. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The Company is not currently under examination by income tax authorities in federal, state or other foreign jurisdictions. ​ The Inflation Reduction Act of 2022 (the “Act”), which includes certain new tax measures, was signed into law in August 2022. The Act contains two main tax provisions, a new corporate alternative minimum tax imposed on certain corporations meeting average annual financial statement income of more than $1 billion during a three-year tax period, and an excise tax imposed upon share repurchases by certain publicly traded corporations. The Act is effective for tax years beginning after December 31, 2022; however, the provisions of the Act will not have a material impact on the Company’s consolidated financial statements. The Company will continue to monitor the effect of the Act and its impact on the Company.

LICENSES AND AGREEMENTS

LICENSES AND AGREEMENTS	12 Months Ended
	Dec. 31, 2023
LICENSES AND AGREEMENTS
LICENSES AND AGREEMENTS	NOTE 13. LICENSES AND AGREEMENTS National Institutes of Health (the “NIH”) and the National Cancer Institute (the “NCI”) Cooperative Research and Development Agreement (the “CRADA”) In August 2011, the Company signed a five-year CRADA with the NCI to work on the development of adoptive cell immunotherapies in multiple solid tumor types, including unmodified TIL as a stand-alone therapy or in combination, improved methods for the generation and selection of TIL cell therapy with anti-tumor reactivity, and strategies for more potent TILs that are designed to destroy metastatic melanoma cells. The CRADA was amended in 2015 and 2016 to, among other things, extend the term of the CRADA through August 2021, include new indications such as the development of TIL cell therapy for the treatment of patients with bladder, lung, triple-negative breast, and Human Papilloma Virus (“HPV”)-associated cancers, and modify the focus on the development of unmodified TIL as a stand-alone therapy or in combination. The parties have continued the development of improved methods for the generation and selection of TIL with anti-tumor reactivity in metastatic melanoma, bladder, lung, breast, and HPV-associated cancers. ​ In August 2021, the NCI and the Company entered into a third amendment to the CRADA. The third amendment, among other things, extended the term of the CRADA by three years to August 2024. The research plan in this amendment includes the evaluation in clinical trials of strategies for development of more potent TILs, such as selection of CD39/69 double negative cells and the use of certain inhibitors or other reagents in TIL expansion cultures. Pursuant to the terms of the CRADA, as amended, the Company is required to make quarterly payments of $0.5 million to the NCI for support of research activities. To the extent the Company licenses patent rights relating to a TIL-based product candidate, the Company will be responsible for all patent-related expenses and fees, past and future, relating to the TIL-based product candidate. In addition, the Company may be required to supply certain test articles, including TIL, grown and processed under Current Good Manufacturing Practice (“cGMP”) conditions, suitable for use in clinical trials. The extended CRADA has a three-year term expiring in August 2024. The Company or the NCI may unilaterally terminate the CRADA for any reason or for no reason at any time by providing written notice at least 60 days before the desired termination date. The Company recorded costs associated with the CRADA of $2.0 million for each of the years ended December 31, 2023, 2022 and 2021, respectively, as research and development expenses. Patent License Agreement Related to the Development and Manufacture of TIL Cell Therapies The Company entered into an Exclusive Patent License Agreement (the “Patent License Agreement”) with the NIH, an agency of the U.S. Public Health Service within the Department of Health and Human Services, in 2011, as amended in 2015. Pursuant to the Patent License Agreement, as amended, the NIH granted the Company licenses, including exclusive, co-exclusive, and non-exclusive licenses, to certain technologies relating to autologous tumor infiltrating lymphocyte adoptive cell therapy products for the treatment of metastatic melanoma, lung, breast, bladder and HPV-positive cancers. Effective May 6, 2021, the Company entered into an Amended and Restated Patent License Agreement with NIH, which included the grant of additional exclusive, worldwide patent rights in the indications to interleukin-15 and interleukin-21 cytokine-tethered TIL technology, and expanded the non-exclusive, worldwide field of use to all cancers. Effective August 1, 2022, the Company entered into a Second Amended and Restated Patent License Agreement with NIH to include additional exclusive, worldwide patent rights to TIL products expressing interleukin-12, expanded rights to TIL selection technologies previously licensed under the Exclusive Patent License Agreement below, and additional non-exclusive, worldwide patent rights to certain technologies related to enhancing TIL potency. The Second Amended and Restated Patent License Agreement requires the Company to pay royalties based on a percentage of net sales in jurisdictions where patent rights exist, which percentage can fall into a tier that may be less than one percent to mid-single digits depending upon certain events, including the exclusivity of the rights, and the Company expects lower overall royalty payments as a result. The Company also agreed to potential milestone payments on the achievement of certain clinical, regulatory, and commercial sales milestones for each of the indications and other direct costs incurred by the NIH pursuant to the Second Amended and Restated Patent License Agreement. The Company anticipates making additional payments that could range from several hundred thousand dollars to the mid-single-digit millions of dollars in conjunction with certain development milestones, the approval of a BLA or its foreign equivalent, or the first U.S. and foreign commercial sales of any of our product candidates covered by the Second Amended and Restated Patent License Agreement. The term of the Second Amended and Restated Patent License Agreement continues until the expiry of the last-to-expire patent rights licensed thereunder, and the agreement contains standard termination provisions. The Company recorded milestone costs associated with the Second Amended and Restated Patent License Agreement, specifically for the completion of the first licensee-sponsored Phase 2 trial of $0.6 million for the year ended December 31, 2023. In addition, with the approval of Amtagvi™, we will be required to remit $1.5 million within 60 days of the approval date in accordance with the requirements of the Second Amended and Restated Patent License Agreement. No expenses were recorded for the years ended December 31, 2022 and 2021, respectively. Exclusive Patent License Agreement Related to TIL Selection On February 10, 2015, the Company entered into an exclusive patent license agreement (the “Exclusive Patent License Agreement”) with the NIH under which the Company received an exclusive, worldwide license under the selected TIL patents. This license was superseded and replaced by the Second Amended and Restated Patent License Agreement. H. Lee Moffitt Cancer Center Research Collaboration and Clinical Grant Agreements with Moffitt In June 2020, the Company entered into a Sponsored Research Agreement (the “Research Agreement”) with the H. Lee Moffitt Cancer Center (“Moffitt”), with a term that ends either upon completion of the research thereunder or on July 1, 2022, whichever is sooner. In June 2022, this agreement was extended until the later of December 19, 2022 or a mutually acceptable completion of the Research Agreement, which was expected in mid-2023. In August 2023, this agreement was extended until September 2023, at which point it expired. In December 2023, this agreement was extended until the later of November 30, 2024 or a mutually agreed determination of the completion of the Research Agreement. The Company recorded research and development costs of $0.2 million, $0.6 million and $0.3 million for each of the years ended December 31, 2023, 2022 and 2021, respectively. In December 2016, the Company entered into a clinical grant agreement with Moffitt to support an ongoing clinical trial at Moffitt that combines TIL cell therapy with nivolumab for the treatment of patients with metastatic melanoma. In June 2017, the Company entered into a second clinical grant agreement with Moffitt to support a new clinical trial at Moffitt that combines TIL cell therapy with nivolumab for the treatment of patients with non-small cell lung cancer, under which the Company obtained a non-exclusive, royalty-free license to any new Moffitt inventions made in the performance of the agreement. Under both clinical grant agreements with Moffit, the Company has non-exclusive rights to clinical data arising from the respective clinical trials, which are now closed. No expense was recorded for the years ended December 31, 2023, and for the year ended December 31, 2022 and 2021 the Company recorded $0.1 million of research and development costs, in connection with the research collaboration and clinical grant agreements with Moffitt. Exclusive License Agreements with Moffitt The Company entered into a license agreement with Moffitt (the “First Moffitt License”), effective as of June 28, 2014, under which the Company received a worldwide license to Moffitt’s rights to patent-pending and patented technologies related to methods for improving TIL for adoptive cell therapy using toll-like receptor agonists. Unless earlier terminated, the term of the license extends until the earlier of the expiration of the last issued patent related to the licensed technology or 20 years after the effective date of the license agreement. Pursuant to the First Moffitt License, the Company paid an upfront licensing fee in the amount of $0.1 million, which was recorded as research and development expense. A patent issuance fee will also be payable under the First Moffitt License, upon the issuance of the first U.S. patent covering the subject technology. In addition, the Company agreed to pay milestone license fees upon completion of specified milestones, customary royalties based on a specified percentage of net sales (which percentage is in the low single digits) and sublicensing payments, as applicable, and annual minimum royalties beginning with the first sale of products based on the licensed technologies, which minimum royalties will be credited against the percentage royalty payments otherwise payable in that year. The Company will also be responsible for all costs associated with the preparation, filing, maintenance and prosecution of the patent applications and patents covered by the First Moffitt License related to the treatment of any cancers in the U.S., Europe and Japan and in other countries designated by the Company in agreement with Moffitt. No expenses were recorded for the First Moffitt License for the years ended December 31, 2023, 2022, and 2021. The Company entered into a second license agreement with Moffitt effective as of May 7, 2018 (the “Second Moffitt License”), under which the Company received a license to Moffitt’s rights to patent-pending technologies related to the use of 4-1BB agonists in conjunction with TIL manufacturing processes and therapies. Pursuant to the Second Moffitt License, the Company paid an upfront licensing fee in the amount of $0.1 million in 2018. An annual license maintenance fee is also payable commencing on the first anniversary of the effective date. The Company agreed to pay an annual commercial use payment for each indication for which a first sale has occurred, which in the aggregate amounts to up to $0.4 million a year. The Company recorded $0.1 million, $0.2 million and $0.1 million for the years ended December 31, 2023, 2022 and 2021, respectively, as research and development expenses in connection with this agreement. The Company subsequently exercised an option to exclusively license Moffitt’s rights to patent pending technologies related to the use of tumor digests in conjunction with TIL manufacturing processes and therapies and entered into an amended and restated Second Moffitt License in October 2021 (the “Amended & Restated Second Moffit License”), to include these rights. Pursuant to the Amended & Restated Second Moffitt License, the Company paid an upfront licensing fee in the amount of $0.2 million in 2021, which was recorded as research and development expense. In addition, the Company agreed to pay an annual commercial use payment for each indication for which a first sale has occurred for products relating to the use of 4-1BB agonists and for products relating to the use of tumor digests covered by the license. The University of Texas M.D. Anderson Cancer Center Strategic Alliance Agreement On April 17, 2017, the Company entered into a Strategic Alliance Agreement (the “SAA”) with The University of Texas M.D. Anderson Cancer Center (“MDACC”) under which the Company and MDACC agreed to conduct clinical and preclinical research studies. The Company agreed in the SAA to provide total funding not to exceed approximately $14.2 million for the performance of the multi-year studies under the SAA, of which approximately $5.3 million has been funded cumulatively through December 31, 2023 and has been recorded as research and development expense. In return, the Company acquired all rights to inventions resulting from the studies and has been granted a non-exclusive, sub-licensable, royalty-free, and perpetual license to specified background intellectual property of MDACC reasonably necessary to exploit, including the commercialization thereof. The Company has also been granted certain rights in clinical data generated by MDACC outside of the clinical trials to be performed under the SAA. The SAA’s term shall continue in effect until the later of the fourth anniversary of the SAA or the completion or termination of the research and receipt by the Company of all deliverables due from MDACC thereunder. The Company recorded zero, $0.2 million and $0.5 million associated with the SAA for the years ended December 31, 2023, 2022 and 2021 as research and development expenses, respectively. WuXi Advanced Therapies, Inc. First WuXi Manufacturing and Services Agreement In November 2016, the Company entered into a three-year manufacturing and services agreement (the “First Wuxi MSA”) with WuXi Advanced Therapies, Inc. (“WuXi”) pursuant to which WuXi agreed to provide manufacturing and other services, which has since been amended and assigned to its subsidiary Iovance Biotherapeutics Manufacturing LLC. Under the First WuXi MSA, the Company entered into two statements of work for two cGMP manufacturing suites to be operated by WuXi for the Company. The terms of one of these statements of work expired in December 2022. Second WuXi Manufacturing and Services Agreement In October 2022, the Company’s subsidiary Iovance Biotherapeutics Manufacturing LLC entered into an additional three-year manufacturing and services agreement (the “Second WuXi MSA”) with WuXi and its parent company WuXi Apptec, Co. Ltd pursuant to which WuXi agreed to provide commercial and clinical manufacturing services and related testing services. Under the Second WuXi MSA, the Company entered into a statement of work for the two cGMP manufacturing suites to be operated by WuXi for the Company. Both suites are expected to be capable of being used for the commercial and clinical manufacture of the Company’s products. The Second WuXi MSA and its related statement of work will supersede the statements of work under the First WuXi MSA with respect to commercial and clinical manufacturing and the two manufacturing suites. Certain other statements of work for related services will also be covered by the Second WuXi MSA. The First WuXi MSA addressed development services provided by WuXi to the Company. Prior to regulatory approval, or if the Company experiences a material adverse event, the Company may unilaterally terminate the statement of work for commercial and clinical manufacturing under the Second WuXi MSA at any time by providing written notice of at least 120 days. Post regulatory approval, the Company may unilaterally terminate the statement of work for commercial and clinical manufacturing with written notice of 15 month in year 1 of the term, written notice of 9 months in year 2 of the term, and written notice of 6 months in year 3 of the term. If WuXi fails a pre-licensing inspection and does not address any related issues within 90 days of receipt of the FDA response letter, the Company may either terminate the statement of work for commercial and clinical manufacturing under the Second WuXi MSA immediately or shorten the term of this statement of work to June 30, 2024. The Company recorded costs associated with agreements with WuXi of $17.3 million, $14.2 million, and $17.5 million for the years ended December 31, 2023, 2022, and 2021 respectively, as research and development expenses. Cellectis S.A On December 31, 2019, the Company entered into a research collaboration and exclusive worldwide license agreement whereby the Company will license gene-editing technology from Cellectis S.A. (“Cellectis”), a clinical-stage biopharmaceutical company, to develop TIL cell therapies that have been genetically edited, including a PD-1 inactivated product that the Company refers to as IOV-4001. Financial terms of the license include annual license payments and development, regulatory and sales milestone payments from the Company to Cellectis, as well as royalty payments based on net sales of TALEN®-modified TIL products. The Company recorded costs associated with the license agreement with Cellectis of $0.4 million for each of the years ended December 31, 2023, 2022, and 2021 respectively as research and development expense. Novartis Pharma AG ​ On January 9, 2020, the Company obtained a license from Novartis Pharma AG (“Novartis”) to develop and commercialize an antibody cytokine engrafted protein, which the Company refers to as IOV-3001. Under the agreement, the Company paid an upfront payment to Novartis and may pay future milestones related to initiation of patient dosing in various phases of clinical development for IOV-3001 and approval of the product in the U.S., EU and Japan. Novartis is also entitled to low-to-mid single digit percentage royalties from commercial sales of the product. The Company recorded costs associated with the license agreement from Novartis of $10.0 million as research and development expenses for the year ended December 31, 2020. No expenses were recorded for the years ended December 31, 2023 and 2022. ​ On May 18, 2023, as part of the completion of the Acquisition, the Company inherited two historical asset purchase agreements, one historical master cell bank license and working cell bank transfer agreement and one historical license agreement from Clinigen with Novartis AG, Novartis Pharma AG and Novartis Vaccines and Diagnostics, Inc. pursuant to which, among other things, the Company may be required to make future milestone payments based on net sales (as defined in the relevant underlying agreements) in the United States and the rest of world, which includes any and all sales outside of the United States. The maximum amount of these milestone payments payable under these agreements is $30.0 million upon reaching several certain net sales amounts in the United States and $15.0 million upon reaching several certain net sales amounts in the rest of the world, of which 25% of each milestone payment will be reimbursed by Clinigen by deduction from the deferred consideration due under the Option Agreement in the period such milestone payment is made. To date, the net sales milestones have not been achieved, and, therefore, no payments were made under these agreements for the year ended December 31, 2023. ​ Boehringer Ingelheim Biopharmaceuticals GmbH On May 18, 2023 as part of the completion of the Acquisition, the Company inherited a manufacturing and supply agreement from Clinigen with Boehringer Ingelheim Biopharmaceuticals GmbH (“BI”) pursuant to which BI will carry out the processing, manufacturing and supply of Proleukin ®

LEASES

LEASES	12 Months Ended
	Dec. 31, 2023
LEASES
LEASES	NOTE 14. LEASES Operating Leases The Company leases corporate office space in California, including 49,918 square feet for its current corporate headquarters’ office space in San Carlos, California, manufacturing, research and development lab facilities and office space in Philadelphia, Pennsylvania, including 136,000 square feet of commercial manufacturing and lab space at the i The Company’s leases have remaining lease terms that range from less than one year to approximately 20 years. Some of our leases include one or more options to renew with renewal terms that can extend the lease for additional years, or options to terminate the leases, both at the Company’s discretion. The Company’s leases may include options to extend or terminate the lease, which is considered in the lease term when it is reasonably certain that the Company will exercise any such options. Lease expense for minimum lease payments is recognized on a straight-line basis based on the fixed components of a lease arrangement. Variable lease cost is determined based on performance or usage in accordance with the contractual agreements, and not based on an index or rate. Such costs that are not fixed in nature are recognized as incurred. The Company also leases certain furniture and equipment that has a lease term of 12 months or less. Since the lease agreement do not include an option to purchase the underlying asset, the Company elected not to apply the recognition requirements of Topic 842 for short-term leases, however, the lease costs that pertain to the short-term leases are disclosed in the components of lease costs table below. Manufacturing Contracts The Company uses contract manufacturing organizations (collectively the “CMOs” and each a “CMO”) to manufacture and supply TILs for clinical and commercial purposes. The CMO contractual obligations consist of the use of manufacturing facilities and minimum fixed commitment fees, such as personnel, general support fees, and minimum production or material fees. In addition to the minimum fixed commitment fees, the CMO contractual obligations include variable costs such as production and material costs in excess of the minimum quantity specified in each CMO agreement. During the term of each CMO agreement, the Company has access to and control of the use of a dedicated suite in each of the CMOs’ facilities for manufacturing activities. The contracts with CMOs generally contain embedded operating leases based on the fact that the suites are used for the Company’s production are implicitly identified, are used exclusively by the Company during the contractual term of the arrangements, and the CMOs have no substantive contractual rights to substitute the facilities used by the Company. Further, the Company controls the use of the facilities by obtaining all of the economic benefits from the use of the facilities and direct the use of the facilities throughout the period of use. The terms of the CMO contracts include options to terminate the lease with advance notice of five to six months. The termination clauses and extension clauses are included in the calculation of the lease term for each of the CMOs when it is reasonably certain that it will not exercise such options. For contracts with multiple deliverables, Topic 842 requires the Company to first identify a lease deliverable and non-lease deliverable included in the arrangements, and then allocate the fixed contractual consideration to the lease deliverable(s) and the non-lease deliverable(s) on a relative standalone selling price basis to determine the amount of operating lease right-of-use assets and liabilities. The Company identified the use of a dedicated suite as a single lease deliverable, and related labor services as a single non-lease deliverable in each of the CMO arrangements. Judgment is required to determine the relative standalone selling price of each deliverable as the observable standalone selling prices are not readily available. Therefore, management uses estimates and assumptions in determining relative standalone selling price of lease of a suite and labor service using information that includes market and other observable inputs to the extent possible. The balance sheet classification of the Company’s right-of-use asset and lease liabilities was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2023 ​ 2022 Operating lease right-of-use assets $ 62,515 $ 73,015 Operating lease liabilities ​ ​ ​ Current portion included in current liabilities ​ 7,777 ​ 12,587 Long-term portion included in non-current liabilities ​ 67,085 ​ 71,859 Total operating lease liabilities ​ $ 74,862 ​ $ 84,446 ​ The following table summarizes components of lease expenses, which were included in total expenses in the Company’s consolidated statements of operations, and other information related to our operating leases as follows (in thousands, except weighted-average remaining lease terms and discount rates): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year ​ For the Year ​ ​ Ended ​ Ended ​ December 31, 2023 December 31, 2022 Operating lease cost ​ $ 17,786 ​ $ 17,657 ​ Variable lease cost ​ ​ 7,629 ​ 5,447 ​ Short-term lease cost ​ ​ 335 ​ 154 ​ Total lease cost ​ $ 25,750 ​ $ 23,258 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in cash flows from operations ​ $ 16,871 ​ $ 14,209 ​ Tenant improvement allowance received for amounts included in the measurement of lease liabilities included in cash flows from operations ​ ​ — ​ ​ 6,432 ​ Right-of-use assets obtained from entering new leases ​ $ 177 ​ $ 553 ​ Increase in right-of-use assets from lease modifications ​ $ 1,033 ​ $ 15,304 ​ Weighted-average remaining lease terms (years) ​ ​ 13.09 ​ ​ 12.90 ​ Weighted-average discount rates ​ ​ 7.4 % ​ 7.5 % ​ As of December 31, 2023, maturities of the Company's operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ Year Ending December 31, ​ leases leases Total 2024 ​ $ 8,579 ​ $ 4,349 ​ $ 12,928 2025 ​ 8,324 ​ — ​ 8,324 2026 ​ 7,989 ​ — ​ 7,989 2027 ​ 8,186 ​ — ​ 8,186 2028 ​ 8,389 ​ — ​ 8,389 Thereafter ​ 75,438 ​ — ​ 75,438 Total lease payments ​ $ 116,905 ​ $ 4,349 ​ $ 121,254 Less: Present value adjustment ​ (46,254) ​ (138) ​ (46,392) Operating lease liabilities ​ $ 70,651 ​ $ 4,211 ​ $ 74,862 ​ For its corporate headquarters’ office, the lease agreement includes a tenant improvement allowance of $8.2 million. For the years ended December 31, 2023 and 2022, the Company has received reimbursements associated with this tenant improvement allowance of zero and $6.4 million, respectively. The Company does not expect to receive additional reimbursement associated with this tenant improvement allowance.

LEGAL PROCEEDINGS

LEGAL PROCEEDINGS	12 Months Ended
	Dec. 31, 2023
LEGAL PROCEEDINGS
LEGAL PROCEEDINGS	​ NOTE 15. LEGAL PROCEEDINGS Derivative Lawsuit. ​ Solomon Capital, LLC. Solomon Capital, LLC, Solomon Capital 401(K) Trust, Solomon Sharbat and Shelhav Raff v. Lion Biotechnologies, Inc. The complaint further alleges that the Company agreed to (i) provide them with promissory notes totaling $0.2 million, plus interest, (ii) issue a total of 1,110 shares to the Solomon Plaintiffs (after the 1-for-100 In its counterclaims, the Company is seeking damages in an amount exceeding $0.5 million and an order rescinding any and all agreements that the Solomon Plaintiffs contend entitled them to obtain shares of Company stock. On May 12, 2020, the court granted the Company’s motion for summary judgment limiting the Solomon Plaintiffs’ damages for the Equity Claim to $47,420. The Solomon Plaintiffs filed a notice of appeal of this summary judgment on June 9, 2020. On July 2, 2020, the court granted the Company’s motion to dismiss the First Solomon Suit for want of prosecution. On January 4, 2021, the court granted the Solomon Plaintiffs motion for reconsideration, and reinstituted the case. On January 15, 2021, the Company filed a notice of appeal of the court’s grant of the Solomon Plaintiffs motion for reconsideration. On May 11, 2021, the Appellate Division upheld the court’s grant of the Solomon Plaintiffs’ motion for reconsideration of the dismissal of the First Solomon Suit for want of prosecution. On September 27, 2019, the Solomon Plaintiffs filed a new lawsuit (through new legal counsel) (“the Second Solomon Suit”) titled Solomon Capital, LLC, Solomon Capital 401(K) Trust, Solomon Sharbat and Shelhav Raff v. Iovance Biotherapeutics, Inc., f/k/a/ Lion Biotechnologies Inc. f/k/a/ Genesis Biopharma Inc., and Manish Singh the U.S. Court of Appeals for the Second Circuit, appealing the District Court’s orders (a) granting the motions for judgment on the pleadings filed on behalf of Singh and the Company, (b) granting the Company’s Rule 11 motion, (c) denying the Solomon Plaintiffs’ motions to compel discovery and re-open discovery, and (d) granting the Company’s summary judgment motion. On December 22, 2023, the Company filed a motion for an order requiring the Solomon Plaintiffs to post an appeal bond, to ensure payment of the Company’s appellate fees and costs should the Company prevail on the appeal. The Company intends to vigorously defend these complaints and pursue its counterclaims, as applicable. At the current stage of the litigation, in both the First Solomon Suit and the Second Solomon Suit, it is not possible to estimate the amount or range of possible loss that might result from an adverse judgment or a settlement of these matters. The Company has been and may continue to be involved, from time to time, in legal proceedings and claims arising in the ordinary course of its business. Such matters are subject to many uncertainties and outcomes are not predictable with assurance. The Company accrues amounts, to the extent they can be reasonably estimated, that it believes are adequate to address any liabilities related to legal proceedings and other loss contingencies that it believes will result in a probable loss. While there can be no assurances as to the ultimate outcome of any legal proceeding or other loss contingency involving the Company, management does not believe any pending matter will be resolved in a manner that would have a material adverse effect on its financial position, results of operations or cash flows.

LONG-TERM NOTE PAYABLE

LONG-TERM NOTE PAYABLE	12 Months Ended
	Dec. 31, 2023
LONG-TERM NOTE PAYABLE
LONG-TERM NOTE PAYABLE	NOTE 16. LONG-TERM NOTE PAYABLE On January 26, 2021, the Company entered into a Loan Note and accompanying Economic Stimulus Program Loan Agreement with PIDC – Local Development Corporation, a Pennsylvania nonprofit corporation (the “Lender”), pursuant to which the Lender agreed to make a loan (the “Job Creation Loan”) to the Company in a principal amount of $1.0 million. The Job Creation Loan will be for a term of five years starting on February 18, 2021, the date of the issuance of a final certificate of occupancy for the Company’s leased premises in Philadelphia, Pennsylvania. The Job Creation Loan is unsecured, bears no interest, and will be forgiven by the Lender in the amount of $2,000 per full-time or “full time equivalent” (defined as two or more part time employees whose working hours total at least 35 hours a week) employee with an average salary of at least $80,000 (“FT Employees”), up to a maximum amount equal to the amount of the Job Creation Loan, as calculated based on the average number of FT Employees employed at the Company’s premises during the period of the 5-year term beginning on the date that is nine months prior to the maturity date and ending on the maturity date. If the Job Creation Loan is not forgiven in full by the maturity date, the remaining balance of the loan not forgiven will become payable on the maturity date. The Loan Note includes customary events of default. Upon the occurrence of an event of default, the Lender will have the right to exercise remedies against the Company, including the right to require immediate payment of all amounts due under the Loan Note. The Company concluded that it is not reasonably assured that all or a portion of the loan will be forgiven as of December 31, 2023, and therefore accounted for the Job Creation Loan as debt in accordance with ASC Topic 470, Debt, as opposed to an in-substance government grant, and classified as a long-term debt in its consolidated balance sheets as of December 31, 2023 and 2022.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2023
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	​ NOTE 17. SUBSEQUENT EVENTS FDA Approval of Amtagvi™ ( lifileucel) On February 16, 2024, the Company announced that the FDA approved Amtagvi™ ( Public Offering On February 22, 2024, the Company closed the sale of an aggregate of 23,014,000 shares of its common stock, pursuant to an underwriting agreement with Jefferies, Barclays Capital Inc., and Goldman Sachs & Co. LLC at a public offering price of $9.15 per share, before underwriting discounts and commissions. The total estimated net proceeds to the Company from the offering are expected to be approximately $197.1 million after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Cash, Cash Equivalents, and Investments	Cash, Cash Equivalents, and Investments The Company’s cash and cash equivalents include short-term investments with original maturities of three months or less when purchased. The Company's investments are classified as “available-for-sale.” The Company includes these investments in current assets or non-current assets in the Consolidated Balance Sheets based on the length of maturity from the reporting date and carries them at fair value. Unrealized gains and losses on available-for-sale securities are recorded in accumulated other comprehensive loss. Impairment losses related to credit losses (if any) are recorded as an allowance for credit losses with an offsetting entry to Interest income, net. No impairment losses related to credit losses were recognized for the years ended December 31, 2023, 2022 and 2021. The cost of debt securities is adjusted for the amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in Interest income, net in the consolidated statements of operations. Gains and losses on securities sold are recorded based on the specific identification method and are included in Interest income, net in the consolidated statements of operations. The Company has not incurred any realized gains or losses from sales of securities to date. The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, obligations issued by the U.S. government and U.S. government agencies as well as corporate debt securities and commercial paper, and places restrictions on maturities and concentration by type and issuer, except for securities issued by the U.S. government.
Restricted Cash	Restricted Cash The Company maintains a required minimum balance in a segregated bank account in connection with its letters of credit for which amounts are restricted as to their use by the Company. Currently, the Company’s letters of credit are primarily comprised of one for the benefit of the landlord for the Iovance Cell Therapy Center (the “ i ® ® The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 ​ 2022 ​ 2021 Cash and cash equivalents ​ $ 114,888 ​ $ 231,731 ​ $ 78,229 Restricted cash ​ 66,430 ​ 6,430 ​ 6,084 Total cash, cash equivalents and restricted cash ​ $ 181,318 ​ $ 238,161 ​ $ 84,313 ​
Asset Acquisitions	Asset Acquisitions ​ The Company evaluates acquisitions of assets using the guidance in Accounting Standard Codification (“ASC”) Topic 805, Business Combinations (“ASC 805”), to determine whether the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to assess if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of assets. If the screen test is met, the transaction is accounted for as an asset acquisition. If the screen test is not met, further assessment is required to determine whether the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If the assets acquired do not constitute a business, the Company accounts for asset acquisitions using the cost accumulation and allocation method. Under this method, the cost of the acquisition, including direct acquisition-related costs, is allocated to the assets acquired on a relative fair value basis. Goodwill is not recognized in an asset acquisition and any difference between consideration transferred and the fair value of the net assets acquired is allocated to the identifiable assets acquired based on their relative fair values. Deferred tax liabilities arising from basis differences in assets acquired are calculated using the simultaneous equations method under ASC Topic 740, Income Taxes (“ASC 740”), and based on the effective tax rate. The resulting deferred tax liability is recorded in the consolidated balance sheet as of December 31, 2023. Contingent consideration in the scope of ASC Topic 815, Derivatives and Hedging (“ASC 815”), is included in the cost of the asset acquisition at its acquisition date fair value. Contingent consideration in the scope of ASC Topic 450, Contingencies (“ASC 450”), is recognized when it is both probable and reasonably estimable.
Inventory and Cost of Sales	Inventory and Cost of Sales ​ Inventory is stated at the lower of cost or net realizable value on a first-in, first-out basis. Cost includes amounts related to materials, labor and overhead. Net realizable value is the estimated selling price in the ordinary course of business less reasonably predictable costs of completion, disposal and transportation. Inventories presented in the consolidated balance sheet as of December 31, 2023 pertain solely to Proleukin ® ® Cost of sales includes the cost of Proleukin ® ® ®
Trade Accounts Receivable	Trade Accounts Receivable ​ Trade accounts receivable are recorded net of allowances for product returns and estimated credit losses. The estimate of allowance for credit losses considers factors, including existing contractual payment and the aging of receivable from its customers. To date, the Company has determined that an allowance for doubtful accounts is not required.
Intangible Assets	Intangible Assets ​ The Company’s intangible assets are initially measured based on an allocation of the cost of the acquisition to the assets acquired on a relative fair value basis and are recorded net of accumulated amortization. The Company amortizes the intangible assets on a straight-line basis over their estimated useful lives. When contingent consideration is a component of the cost of an asset acquisition, the Company capitalizes the amount of incremental cost from the contingent consideration related to the intangible asset acquired in the period the underlying contingency is resolved. When this occurs, the Company will recognize amortization expense on the incremental cost prospectively from the date the incremental costs are capitalized. The Company reviews intangible assets for impairment at least annually and whenever events or changes in circumstances have occurred which could indicate that the carrying value of the assets are not recoverable. If such indicators are present, the Company assesses the recoverability of affected assets by determining if the carrying value of the assets is less than the sum of the undiscounted future cash flows of the assets. If the assets are found to not be recoverable, the Company measures the amount of impairment by comparing the carrying value of the assets to their fair values. The Company determined that no indicators of impairment existed as of December 31, 2023.
Leases	Leases The Company determines if an arrangement includes a lease at inception and thereafter, if modified. Operating leases are included in its consolidated balance sheets as Operating lease right-of-use assets and Operating lease liabilities as of December 31, 2023 and 2022. Operating lease right-of-use assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date or modification date based on the present value of lease payments over the lease term. In determining the net present value of lease payments, the Company uses an estimated incremental borrowing rate that is applicable to the Company based on the information available at the later of the lease commencement or modification date. The operating lease right-of-use assets also include any lease payments made less lease incentives. The Company’s leases may include options to extend or terminate the lease, which is considered in the lease term when it is reasonably certain that the Company will exercise any such options. Lease expense is recognized on a straight-line basis over the expected lease term and recorded in costs and expenses in the consolidated statements of operations. The Company has elected not to apply the recognition requirements of Accounting Standards Update (“ASU”) No. 2016-02 and No. 2018-10 (together “Topic 842”) for short-term leases. For lease agreements entered into by the Company that include lease and non-lease components, such components are generally accounted for separately.
Property and Equipment, net	Property and Equipment, net ​ Property and equipment are stated at cost, net of accumulated depreciation and amortization. The cost of property and equipment is depreciated or amortized on the straight-line method over the following estimated useful lives. The depreciation or amortization of capitalized construction in progress costs, a component of property and equipment, net, begins once the underlying asset is placed into service and is recognized over the estimated useful lives: ​ Computer equipment 2 years Computer software ​ 5 years Office furniture and equipment ​ 5 years Lab, process, and validation equipment ​ 5 years Machinery and equipment ​ 5 – 7 years Utility equipment ​ Lesser of the remaining economic life of the asset or the lease-term Leasehold improvements ​ Lesser of the remaining economic life of the asset or the lease-term ​ Expenditures for maintenance and repairs are charged to operations as incurred while renewals and betterments are capitalized. Gains and losses on disposals are included within operating expenses in the consolidated statements of operations. Management assesses the carrying value of property and equipment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. If there is an indication of impairment, management prepares an estimate of future undiscounted cash flows expected to result from the use of the asset and its eventual disposition. If these cash flows are less than the carrying amount of the asset, an impairment loss is recognized to write down the asset to its estimated fair value. For the years ended December 31, 2023, 2022, and 2021, the Company did not recognize any impairments for its property and equipment.
Fair Value Measurements	Fair Value Measurements Under ASC Topic 820, Fair Value Measurements and Disclosures (“ASC 820”), fair value is defined as the price at which an asset could be exchanged, or a liability transferred in a transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or parameters are not available, valuation models are applied. Assets and liabilities recorded at fair value in the Company’s financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities, are as follows: - Level 1—These are investments where values are based on unadjusted quoted prices for identical assets in an active market that the Company has the ability to access. - Level 2—These are investments where values are based on quoted market prices in markets that are not active or model derived valuations in which all significant inputs are observable in active markets. - Level 3—These are financial instruments where values are derived from techniques in which one or more significant inputs are unobservable. The Company’s financial instruments consist of cash, cash equivalents, short-term investments, and long-term notes payable, all of which are reported at their respective fair value or approximate fair value on its consolidated balance sheets. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Where quoted prices are available in an active market, securities are classified as Level 1. ​ When quoted market prices are not available for a specific security, the Company estimates the fair value by using quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes, and market reference data. Level 2 assets consist of commercial paper, corporate securities and government agency securities. Level 2 inputs for the valuations are limited to quoted prices for similar assets or liabilities in active markets and inputs other than quoted prices that are observable for the asset.
Revenue Recognition	Revenue Recognition The Company recognizes revenue from product sales in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, revenue is recognized when a customer obtains control of promised goods or services in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price using the most likely method based on historical experience as well as applicable information currently available. Indirect taxes collected from customers and remitted to government authorities that are related to sales of the Company’s products, primarily in Europe, are excluded from revenues. Subsequent to the closing of the acquisition of Proleukin ® ® ®
Stock-Based Compensation	Stock-Based Compensation The Company periodically grants stock options to employees and non-employees as compensation for services rendered. The Company accounts for all stock-based payment awards made to employees, including the employee stock purchase plans, and non-employees in accordance with the authoritative guidance provided by the Financial Accounting Standards Board (“FASB”) where the value of the award is measured on the date of grant and recognized over the vesting period. Forfeitures are recognized in the period in which they occur. The Company accounts for stock option grants to non-employees in a similar manner as stock option grants to employees except for the term used in the grant date fair value, therefore no longer requiring a re-measurement at the then-current fair values at each reporting date until the shares underlying the options have vested. The non-employee awards that contain a performance condition that affects the quantity or other terms of the award are measured based on the outcome that is probable. The fair value of the Company's common stock option grants is estimated using a Black-Scholes option pricing model, which uses certain assumptions related to risk-free interest rates, expected volatility, expected term of the common stock options, and future dividends. The stock-based compensation expense is recorded based upon the value derived from the Black-Scholes option pricing model. The assumptions used in the Black-Scholes option pricing model could affect compensation expense recorded in future periods. The Company issues restricted stock units (“RSUs”) from time to time as part of its equity incentive plans. The Company measures the compensation cost with respect to RSUs issued to employees based upon the estimated fair value of the equity instruments at the date of the grant, which is recognized as an expense over the period during which an employee is required to provide services in exchange for the awards. The fair value of RSUs is based on the closing price of the Company’s common stock on the grant date. In addition to RSUs that have time-based vesting requirements, from time to time the Company may issue RSUs that include certain performance vesting criteria based upon the satisfaction of stated objectives (“PRSUs”). The Company measures the compensation cost with respect to PRSUs issued to employees based upon the estimated fair value of the equity instruments at the date of grant, which is recognized as an expense over the period that achievement is determined to be probable through the stated service period associated with the award.
Accrued Research and Development Costs	Accrued Research and Development Costs Research and development costs are expensed as incurred. Clinical development costs compose a significant component of research and development costs. The Company has a history of contracting with third parties, including contract research organizations (“CROs”), independent clinical investigators, and contract manufacturing organizations (“CMOs”) that perform various clinical trial activities on the Company’s behalf in connection with the ongoing development of the Company’s product candidates. The financial terms of these contracts are subject to negotiations and may vary from contract to contract and may result in uneven payment flow. The Company accrues and expenses costs for clinical trial activities performed by third parties based upon the work completed to date for each clinical trial in accordance with agreements established with CROs, hospitals, and clinical investigators. Accruals for CROs and CMOs are recorded based on services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. The Company determines its costs through discussions with internal clinical stakeholders and outside service providers as to the progress or stage of completion of clinical trials or services and the contracted fee to be paid for such services. ​ Included in the Company’s clinical development costs are investigator costs, which are costs associated with treatments administered at clinical sites as required under each clinical trial protocol. The Company’s determination of clinical investigator costs and related timing of expense recognition will depend on a number of factors that include, but are not limited to, (i) the overall number of patients that enroll in the trial at each individual site, (ii) the length of clinical trial enrollment period, (iii) discontinuation and completion rates of patients, (iv) duration of patient safety follow-ups, (v) the number of sites included in the clinical trial, and (vi) the contracted fee of each participating site for patient treatment while on clinical trial, which can vary greatly for several reasons including, but not limited to, geographic region, medical center or physician costs, and overhead costs. In addition, the Company’s estimates for per patient trial costs will vary based on a number of factors that include, but are not limited to, the extent of additional procedures that may be administered by investigators as a result of patient health status, recoverability of patient costs through insurance carriers of patients, and unanticipated cost of injuries incurred as a result of the clinical trial treatment. The Company accrues estimated expenses resulting from obligations under investigator site agreements as the timing of payments does not always timely align with the periods over which the treatments are administered by the clinical investigators. These estimates are typically based on contracted amounts, patient visit data, discussions with internal clinical stakeholders and outside service providers, and historical look-back analysis of actual payments made to date. ​ The Company makes judgements and estimates in determining the accrual balance in each reporting period. ​ In the event advance payments are made to a CRO, CMO or other outside service provider, the payments are recorded within prepaid expenses and other current assets in the Consolidated Balance Sheets and subsequently recognized as research and development expense in the consolidated statements of operations when the associated services have been performed. As actual costs become known, the Company adjusts its estimates, liabilities and assets. Inputs used in the determination of estimates discussed above may vary from actual, which will result in adjustments to research and development expense in future periods.
Selling, general and administrative expense	Selling, general and administrative expense Selling, general and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in executive, finance, procurement, legal, investor relations, facilities, business development, marketing, commercial, information technology and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses. Selling, general and administrative costs are expensed as incurred, and the Company accrues for services provided by third parties related to such expenses by monitoring the status of services provided and receiving estimates from its service providers and adjusting its accruals as actual costs become known.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method whereby deferred tax assets are recognized for deductible temporary differences, and deferred tax liabilities are recognized for taxable temporary differences. Temporary differences are the differences between the reported amounts of assets and liabilities and their tax bases. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some or all of the deferred tax assets will not be realized. Deferred tax assets and liabilities are adjusted for the effects of changes in tax laws and rates on the date of enactment. ASC Topic 740, Income Taxes
Net Loss per Share	Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted average number of shares of common stock outstanding and the dilutive common stock equivalent outstanding during the period. The Company’s potentially dilutive common stock equivalent shares, which include incremental common shares issuable upon (i) the exercise of outstanding stock options, (ii) purchases though the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), (iii) vesting of restricted stock units, and (vi) conversion of preferred stock, are only included in the calculation of diluted net loss per share when their effect is dilutive. As of December 31, 2023, 2022, and 2021, the following outstanding common stock equivalents have been excluded from the calculation of net loss per share because their impact would be anti-dilutive. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2023 2022 2021 Stock options ​ 18,899,849 15,240,197 12,520,865 Employee Stock Purchase Plan ​ 296,751 ​ 260,859 ​ 85,227 Restricted stock units ​ 3,453,901 ​ 2,436,764 ​ 1,110,010 Series A Convertible Preferred Stock* ​ 97,000 ​ 97,000 ​ 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 2,842,158 2,842,158 ​ ​ 25,589,659 20,876,978 16,655,260 *on an as-converted basis The dilutive effect of potentially dilutive securities would be reflected in diluted earnings per common share by application of the treasury stock method. Under the treasury stock method, an increase in the fair market value of the Company's common stock could result in a greater dilutive effect from potentially dilutive securities.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include assumptions made in the fair value of intangible assets, inventories acquired as part of the acquisition of Proleukin ® , equity awards and related stock-based compensation, assumptions used in measuring operating right-of-use assets and operating lease liabilities, accounting for potential liabilities, including estimates inherent in accruals related to clinical trials, and the realizability of the Company’s deferred tax assets .
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of Iovance Biotherapeutics, Inc. and its wholly-owned subsidiaries, Iovance Biotherapeutics Manufacturing LLC, Iovance Biotherapeutics GmbH, and Iovance Biotherapeutics B.V., Iovance Biotherapeutics UK Ltd and Iovance Biotherapeutics UK SP Ltd (together, the “UK subsidiaries”), and Iovance Biotherapeutics Canada, Inc. All intercompany accounts and transactions have been eliminated. Certain prior year amounts in the notes to these consolidated financial statements have been reclassified for consistency with the current year presentation. These reclassifications had no effect on the previously reported consolidated balance sheets, consolidated statements of operations, consolidated statements of other comprehensive loss, consolidated statements of stockholder’s equity or consolidated statements of cash flows.
Foreign Currency Translation	Foreign Currency Translation The assets and liabilities of the Company’s subsidiaries whose functional currencies are not in U.S. dollars are translated into U.S. dollars at the related period-end exchange rate. The U.S. dollar effects that arise from translation of net assets of these subsidiaries at changing rates are recognized in Accumulated Other Comprehensive Income (Loss) in the consolidated balance sheets. The subsidiaries’ net loss is translated into U.S. dollars by using the average exchange rate for the applicable period. The consolidated financial statements are presented in U.S. dollars, which is the Company’s reporting currency.
Segment Reporting	Segment Reporting The Company operates in one segment, focused on developing and commercializing therapies using autologous TIL for the treatment of metastatic melanoma and other solid tumor cancers.
Concentrations	Concentrations The Company is subject to credit risk from its portfolio of cash, cash equivalents and investments. Under its investment policy, the Company limits amounts invested in such securities by credit rating, maturity, industry group, investment type and issuer, except for securities issued by the U.S. government. The Company does not believe it is exposed to any significant concentrations of credit risk from these financial instruments. The Company maintains cash, cash equivalents and investment balances at four financial institutions. Management believes that the financial institutions which hold its cash are financially sound and, accordingly, minimal credit risk exists. As of December 31, 2023 and 2022, respectively, the Company’s cash balances were in excess of insured limits maintained at the financial institutions.
Recent Accounting Standards Issued But Not Yet Adopted	Recent Accounting Standards Issued But Not Yet Adopted In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the disclosures of income taxes. ASU 2023-09 is effective for the Company in its annual reporting for fiscal 2025 on a prospective basis. Early adoption and retrospective reporting are permitted. The Company is currently evaluating the impact of ASU 2023-09 on its consolidated financial statements. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which enhances the disclosures required for operating segments in annual and interim consolidated financial statements. ASC 2023-07 is effective for the Company in its annual reporting for fiscal year 2024 and for interim period reporting beginning in fiscal year 2025 on a retrospective basis. Early adoption is permitted. The Company is currently evaluating the impact of ASC 2023-07 on its consolidated financial statements.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2023
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of cash and cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2023 ​ 2022 ​ 2021 Cash and cash equivalents ​ $ 114,888 ​ $ 231,731 ​ $ 78,229 Restricted cash ​ 66,430 ​ 6,430 ​ 6,084 Total cash, cash equivalents and restricted cash ​ $ 181,318 ​ $ 238,161 ​ $ 84,313
Schedule Of Useful Lives Of Property Plant And Equipment [Table Text Block]	​ Computer equipment 2 years Computer software ​ 5 years Office furniture and equipment ​ 5 years Lab, process, and validation equipment ​ 5 years Machinery and equipment ​ 5 – 7 years Utility equipment ​ Lesser of the remaining economic life of the asset or the lease-term Leasehold improvements ​ Lesser of the remaining economic life of the asset or the lease-term
Schedule of Antidilutive securities excluded from computation of earnings per share	As of December 31, 2023, 2022, and 2021, the following outstanding common stock equivalents have been excluded from the calculation of net loss per share because their impact would be anti-dilutive. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2023 2022 2021 Stock options ​ 18,899,849 15,240,197 12,520,865 Employee Stock Purchase Plan ​ 296,751 ​ 260,859 ​ 85,227 Restricted stock units ​ 3,453,901 ​ 2,436,764 ​ 1,110,010 Series A Convertible Preferred Stock* ​ 97,000 ​ 97,000 ​ 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 2,842,158 2,842,158 ​ ​ 25,589,659 20,876,978 16,655,260 *on an as-converted basis

CASH EQUIVALENTS AND INVESTME_2

CASH EQUIVALENTS AND INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2023
CASH EQUIVALENTS AND INVESTMENTS
Schedule of cost and fair value of cash equivalents and short-term investments	The amortized cost and fair value of cash equivalents and investments as of December 31, 2023 and December 31, 2022 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2023 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 164,940 ​ $ 39 ​ $ — ​ $ 164,979 Money market funds ​ ​ 34,053 ​ ​ — ​ ​ — ​ ​ 34,053 Total investments ​ $ 198,993 ​ $ 39 ​ $ — ​ $ 199,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2022 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 118,570 ​ $ — ​ $ (850) ​ $ 117,720 U.S. government agency securities ​ 11,272 ​ — ​ (7) ​ 11,265 Corporate securities ​ ​ 7,230 ​ ​ — ​ ​ — ​ ​ 7,230 Commercial paper ​ ​ 148,299 ​ ​ 8 ​ ​ (53) ​ ​ 148,254 Money market funds ​ ​ 88,001 ​ ​ — ​ ​ — ​ ​ 88,001 Total investments ​ $ 373,372 ​ $ 8 ​ $ (910) ​ $ 372,470
Schedule of available-for-sale debt securities	The fair value of cash equivalents and investments as of December 31, 2023 and December 31, 2022 are classified as follows in the Company’s consolidated balance sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, Classified as: ​ 2023 2022 Cash equivalents ​ $ 34,053 ​ $ 132,356 Short-term investments ​ ​ 164,979 ​ ​ 240,114 Total investments ​ $ 199,032 ​ $ 372,470
Schedule of fair value of the company's financial assets	As of December 31, 2023 and 2022, the fair value of the Company’s financial assets that are measured at fair value on a recurring basis, which consist of cash equivalents and short-term and long-term investments classified as available-for-sale securities, are categorized in the table below based upon the lowest level of significant input to the valuations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2023 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 164,979 ​ $ — ​ $ — ​ $ 164,979 Money market funds ​ ​ 34,053 ​ ​ — ​ ​ — ​ ​ 34,053 Total ​ $ 199,032 ​ $ — ​ $ — ​ $ 199,032 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2022 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 117,720 ​ $ — ​ $ — ​ $ 117,720 U.S. government agency securities ​ — ​ 11,265 ​ — ​ 11,265 Corporate securities ​ ​ — ​ ​ 7,230 ​ ​ — ​ ​ 7,230 Commercial paper ​ ​ — ​ ​ 148,254 ​ ​ — ​ ​ 148,254 Money market funds ​ ​ 88,001 ​ ​ — ​ ​ — ​ ​ 88,001 Total ​ $ 205,721 ​ $ 166,749 ​ $ — ​ $ 372,470

PROLEUKIN ACQUISITION (Tables)

PROLEUKIN ACQUISITION (Tables)	12 Months Ended
	Dec. 31, 2023
PROLEUKIN ACQUISITION
Summary of the total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed	The following table summarizes the total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ Amounts Cash ​ $ 35 Inventory ​ ​ 9,688 Developed technology ​ ​ 232,665 Assembled workforce ​ ​ 636 Deferred tax liability ​ ​ (20,352) Total cost of acquisition ​ $ 222,672 ​

INTANGIBLE ASSETS, NET (Tables)

INTANGIBLE ASSETS, NET (Tables)	12 Months Ended
	Dec. 31, 2023
INTANGIBLE ASSETS, NET
Summary of gross carrying amounts and net book value of intangible assets	The gross carrying amounts and net book value of intangible assets as of December 31, 2023 are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ Gross carrying amounts Accumulated amortization Intangible assets, net Intangible assets: ​ ​ ​ ​ ​ ​ ​ Developed technology ​ $ 238,612 $ (9,871) $ 228,741 Assembled workforce ​ ​ 652 ​ (135) ​ 517 Total Intangible Assets ​ $ 239,264 $ (10,006) $ 229,258 * Amounts are translated using the foreign exchange rate as of 12/31/2023. ​ ​ ​ ​ ​ ​ ​

INVENTORY (Tables)

INVENTORY (Tables)	12 Months Ended
	Dec. 31, 2023
INVENTORY
Summary of inventories	As of December 31, 2023 and December 31, 2022, inventory consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ December 31, ​ ​ ​ 2023 ​ ​ 2022 Work in process ​ $ 5,749 ​ $ — Finished goods ​ ​ 4,623 ​ ​ — Total inventory ​ $ 10,372 ​ $ — ​

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2023
PROPERTY AND EQUIPMENT, NET
Schedule of Property and equipment	Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2023 2022 Leasehold improvements ​ $ 76,804 ​ $ 74,305 Lab, process, and validation equipment ​ ​ 23,131 ​ ​ 22,136 Utility equipment ​ 5,990 ​ 5,951 Office furniture and equipment ​ 3,297 ​ 2,927 Computer software ​ ​ 7,772 ​ ​ 6,736 Computer equipment ​ 542 ​ 695 Machinery and equipment ​ ​ 306 ​ ​ 82 Construction in progress ​ 24,101 ​ 9,118 Total property and equipment, cost ​ 141,943 ​ 121,950 Less: Accumulated depreciation and amortization ​ (27,913) ​ (16,718) Property and equipment, net ​ $ 114,030 ​ $ 105,232

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2023
ACCRUED EXPENSES
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2023 2022 Employee and consultant related expenses ​ $ 34,814 ​ $ 20,188 Clinical related ​ ​ 10,911 ​ ​ 14,812 Manufacturing related ​ 10,893 ​ 4,467 Facilities related ​ ​ 2,437 ​ ​ 6,510 Legal and related services ​ 1,610 ​ 3,015 Inventory related ​ ​ 2,148 ​ ​ — Other accrued expenses ​ 6,593 ​ 3,303 Total accrued expenses ​ $ 69,406 ​ $ 52,295 ​

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2023
STOCKHOLDERS' EQUITY
Schedule of status of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ Aggregate ​ ​ Number ​ Average ​ Remaining ​ Intrinsic ​ ​ of ​ Exercise ​ Contract ​ Value ​ Options Price Life (in thousands) Outstanding at December 31, 2022 ​ 15,240,197 $ 22.45 ​ ​ ​ ​ ​ Issued ​ 5,379,670 ​ 7.04 ​ ​ ​ ​ ​ Exercised ​ (8,860) ​ 7.10 ​ ​ ​ ​ ​ Expired/Cancelled ​ (1,711,158) ​ 17.01 ​ ​ ​ ​ ​ Outstanding at December 31, 2023 ​ 18,899,849 $ 18.57 6.75 ​ $ 7,065 Ending vested and expected to vest at December 31, 2023 ​ 18,899,849 ​ $ 18.57 ​ 6.75 ​ $ 7,065 Options exercisable at December 31, 2023 12,160,135 ​ $ 23.40 5.54 ​ $ 1,337
Schedule of summary of RSU activity including PRSUs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ Number ​ Average ​ ​ ​ of ​ Grant Date ​ ​ RSUs and PRSUs Fair Value ​ Outstanding, non-vested as of December 31, 2022 ​ 2,436,764 ​ $ 14.74 ​ Granted ​ 2,729,348 ​ ​ 7.19 ​ Vested/Released ​ (1,253,465) ​ ​ 16.17 ​ Canceled/Forfeited ​ (458,746) ​ ​ 9.35 ​ Outstanding as of December 31, 2023 ​ 3,453,901 ​ $ 8.97 ​ Ending vested and expected to vest at December 31, 2023 ​ 3,453,901 ​ $ 8.97 ​
Schedule of stock-based compensation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 2022 2021 Research and development ​ $ 34,926 ​ $ 50,242 ​ $ 40,833 Selling, general and administrative ​ 27,699 ​ 33,780 ​ 28,932 Total stock-based compensation expense ​ $ 62,625 ​ $ 84,022 ​ $ 69,765
Schedule of stock-based compensation by type of award	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2023 2022 2021 Stock option expense ​ $ 45,340 ​ $ 58,308 ​ $ 56,305 Restricted stock expense ​ 16,062 ​ 24,436 ​ 12,247 ESPP expense ​ 1,223 ​ 1,278 ​ 1,213 Total stock-based compensation expense ​ $ 62,625 ​ $ 84,022 ​ $ 69,765
Schedule of share-based payment award, stock options, valuation assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock Option ​ ESPP ​ ​ Years Ended December 31, ​ Years Ended December 31, Assumptions: 2023 2022 2021 2023 2022 2021 Expected term (years) ​ 5.18 - 5.37 4.94 - 5.12 4.94 - 5.28 ​ 0.5 ​ 0.50 ​ 0.50 Expected volatility ​ 83.63% - 84.21% 73.73% - 83.90% 70.35% - 73.88% ​ 72.96% - 83.36% ​ 73.02% - 137.42% ​ 52.04% - 94.56% Risk-free interest rate ​ 3.59% - 4.60% ​ 1.25% - 4.05% ​ 0.36% - 0.97% ​ 5.38% - 5.40% ​ 1.98% - 4.78% ​ 0.06% - 0.13% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ 0% ​ 0% ​ 0%

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2023
INCOME TAXES
Schedule of Deferred Tax Assets and Liabilities	The significant components of the Company’s net deferred tax assets and liabilities are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2023 2022 Deferred income tax assets: ​ ​ Net operating loss carryforwards ​ $ 255,639 ​ $ 225,904 Stock-based compensation ​ 28,609 ​ 24,920 Tax credit carryforwards ​ 58,565 ​ 46,957 Lease liabilities ​ ​ 16,024 ​ ​ 18,017 Capitalized R&D ​ ​ 99,107 ​ ​ 47,755 Reserves and accruals ​ 6,540 ​ 3,997 Deferred tax assets before valuation allowance ​ 464,484 ​ 367,550 Less: valuation allowance ​ (446,853) ​ (350,418) Net deferred income tax assets ​ 17,631 ​ 17,132 Deferred tax liabilities: ​ ​ ​ ​ Right-of-use assets ​ (13,381) ​ (15,578) Depreciation and amortization ​ (21,597) ​ (1,554) Net deferred tax assets (liabilities) ​ $ (17,347) ​ $ —
Schedule of Effective Income Tax Rate Reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended December 31, ​ 2023 2022 2021 ​ Federal statutory tax rate 21% ​ 21% ​ 21% ​ Orphan drug and research credits 2% 1% 2% ​ Permanent and other differences (1)% (1)% 0% ​ Stock Based Compensation (1)% (1)% 0% ​ State tax, net of federal benefit 1% 1% 0% ​ ​ 22% ​ 21% ​ 23% ​ Valuation allowance (21)% ​ (21)% ​ (23)% ​ Effective tax rate 1% ​ 0% ​ 0% ​
Schedule of Unrecognized Tax Benefits	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2023 2022 2021 Unrecognized benefit - beginning of period ​ $ 21,645 ​ $ 18,171 ​ $ 14,432 Gross decreases - prior period tax positions ​ — ​ — ​ (159) Gross increase current period tax positions ​ 4,462 ​ 3,474 ​ 3,898 Unrecognized benefit - end of period ​ $ 26,107 ​ $ 21,645 ​ $ 18,171

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2023
LEASES
Schedule of balance sheet classification of the Company's right-of-use asset and lease liabilities	The balance sheet classification of the Company’s right-of-use asset and lease liabilities was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ ​ 2023 ​ 2022 Operating lease right-of-use assets $ 62,515 $ 73,015 Operating lease liabilities ​ ​ ​ Current portion included in current liabilities ​ 7,777 ​ 12,587 Long-term portion included in non-current liabilities ​ 67,085 ​ 71,859 Total operating lease liabilities ​ $ 74,862 ​ $ 84,446
Schedule of components of lease expenses	The following table summarizes components of lease expenses, which were included in total expenses in the Company’s consolidated statements of operations, and other information related to our operating leases as follows (in thousands, except weighted-average remaining lease terms and discount rates): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the Year ​ For the Year ​ ​ Ended ​ Ended ​ December 31, 2023 December 31, 2022 Operating lease cost ​ $ 17,786 ​ $ 17,657 ​ Variable lease cost ​ ​ 7,629 ​ 5,447 ​ Short-term lease cost ​ ​ 335 ​ 154 ​ Total lease cost ​ $ 25,750 ​ $ 23,258 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in cash flows from operations ​ $ 16,871 ​ $ 14,209 ​ Tenant improvement allowance received for amounts included in the measurement of lease liabilities included in cash flows from operations ​ ​ — ​ ​ 6,432 ​ Right-of-use assets obtained from entering new leases ​ $ 177 ​ $ 553 ​ Increase in right-of-use assets from lease modifications ​ $ 1,033 ​ $ 15,304 ​ Weighted-average remaining lease terms (years) ​ ​ 13.09 ​ ​ 12.90 ​ Weighted-average discount rates ​ ​ 7.4 % ​ 7.5 % ​
Schedule of minimum lease commitments	As of December 31, 2023, maturities of the Company's operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ Year Ending December 31, ​ leases leases Total 2024 ​ $ 8,579 ​ $ 4,349 ​ $ 12,928 2025 ​ 8,324 ​ — ​ 8,324 2026 ​ 7,989 ​ — ​ 7,989 2027 ​ 8,186 ​ — ​ 8,186 2028 ​ 8,389 ​ — ​ 8,389 Thereafter ​ 75,438 ​ — ​ 75,438 Total lease payments ​ $ 116,905 ​ $ 4,349 ​ $ 121,254 Less: Present value adjustment ​ (46,254) ​ (138) ​ (46,392) Operating lease liabilities ​ $ 70,651 ​ $ 4,211 ​ $ 74,862

GENERAL ORGANIZATION, BUSINES_2

GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY (Details) - USD ($) $ in Thousands			12 Months Ended
	Feb. 22, 2024	Jul. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Income (Loss)			$ (444,037)	$ (395,893)	$ (342,252)
Net cash used in operating activities			(361,820)	(292,757)	(227,941)
Cash equivalents, short-term investments, and restricted cash			346,300
Cash and cash equivalents			114,888	231,731	78,229
Short-term investments			164,979	240,114
Restricted cash			66,430	6,430	6,084
Net proceeds from public offering		$ 161,500
Proceeds from the issuance of common stock, net			$ 463,281	$ 189,502	$ 203,156
Common Stock | Public Offering | Subsequent Event
Proceeds from the issuance of common stock, net	$ 197,100

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit	$ 600
Restricted security deposit	5,450
Cash and cash equivalents	114,888	$ 231,731	$ 78,229
Restricted cash	66,430	6,430	6,084
Total cash, cash equivalents and restricted cash	181,318	$ 238,161	$ 84,313	$ 72,854
Commercial manufacturing facility
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit	5,450
Decrease in letters of credit	1,000
Commercial manufacturing facility | Minimum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit	1,500
Headquarters lease
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Future milestone payment	$ 60,000

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Useful lives, impairment (Details)	Dec. 31, 2023
Computer equipment
Property, Plant and Equipment, Useful Life	2 years
Computer software
Property, Plant and Equipment, Useful Life	5 years
Office furniture and equipment
Property, Plant and Equipment, Useful Life	5 years
Lab, process, and validation equipment
Property, Plant and Equipment, Useful Life	5 years
Machinery and equipment | Minimum
Property, Plant and Equipment, Useful Life	5 years
Machinery and equipment | Maximum
Property, Plant and Equipment, Useful Life	7 years
Utility equipment
Property, Plant and Equipment, Estimated Useful Lives	us-gaap:UsefulLifeShorterOfTermOfLeaseOrAssetUtilityMember
Leasehold improvements
Property, Plant and Equipment, Estimated Useful Lives	us-gaap:UsefulLifeShorterOfTermOfLeaseOrAssetUtilityMember

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Segment Reporting (Details)	12 Months Ended
	Dec. 31, 2023 segment item
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Number of operating segments | segment	1
Number Of Financial Institutions | item	4

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive securities excluded from calculation of net loss per share	25,589,659	20,876,978	16,655,260
Employee Stock Option
Antidilutive securities excluded from calculation of net loss per share	18,899,849	15,240,197	12,520,865
Employee Stock Purchase Plan
Antidilutive securities excluded from calculation of net loss per share	296,751	260,859	85,227
Restricted stock units
Antidilutive securities excluded from calculation of net loss per share	3,453,901	2,436,764	1,110,010
Series A Convertible Preferred Stock
Antidilutive securities excluded from calculation of net loss per share	97,000	97,000	97,000
Series B Convertible Preferred Stock | Restricted stock units
Antidilutive securities excluded from calculation of net loss per share	2,842,158	2,842,158	2,842,158

CASH EQUIVALENTS AND INVESTME_3

CASH EQUIVALENTS AND INVESTMENTS - Cost and fair value (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amortized Cost	$ 198,993	$ 373,372
Gross Unrealized Gains	39	8
Gross Unrealized Losses		(910)
Fair Value	199,032	372,470
U.S. treasury securities
Amortized Cost	164,940	118,570
Gross Unrealized Gains	39
Gross Unrealized Losses		(850)
Fair Value	164,979	117,720
U.S. government agency securities
Amortized Cost		11,272
Gross Unrealized Losses		(7)
Fair Value		11,265
Corporate securities
Amortized Cost		7,230
Fair Value		7,230
Commercial paper
Amortized Cost		148,299
Gross Unrealized Gains		8
Gross Unrealized Losses		(53)
Fair Value		148,254
Money market funds
Amortized Cost	34,053	88,001
Fair Value	$ 34,053	$ 88,001

CASH EQUIVALENTS AND INVESTME_4

CASH EQUIVALENTS AND INVESTMENTS - Available for sale debt securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
CASH EQUIVALENTS AND INVESTMENTS
Cash equivalents	$ 34,053	$ 132,356
Short-term investments	164,979	240,114
Total investments	$ 199,032	$ 372,470

CASH EQUIVALENTS AND INVESTME_5

CASH EQUIVALENTS AND INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash equivalents total	$ 34,053	$ 132,356
Unrealized losses on available-for-sale	$ 0	$ 0
Number of investments in debt securities in continuous unrealized loss position for more than 12 months	0	0
Demand Deposits
Cash equivalents total	$ 80,800	$ 99,400

CASH EQUIVALENTS AND INVESTME_6

CASH EQUIVALENTS AND INVESTMENTS - Fair value of company's financial assets (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Total	$ 199,032	$ 372,470
U.S. treasury securities
Total	164,979	117,720
U.S. government agency securities
Total		11,265
Corporate securities
Total		7,230
Commercial paper
Total		148,254
Money market funds
Total	34,053	88,001
Level 1
Total	199,032	205,721
Level 1 | U.S. treasury securities
Total	164,979	117,720
Level 1 | Money market funds
Total	$ 34,053	88,001
Level 2
Total		166,749
Level 2 | U.S. government agency securities
Total		11,265
Level 2 | Corporate securities
Total		7,230
Level 2 | Commercial paper
Total		$ 148,254

PROLEUKIN ACQUISITION - Narrati

PROLEUKIN ACQUISITION - Narrative (Details) - PROLEUKIN £ in Millions, $ in Millions			12 Months Ended
	May 18, 2023 GBP (£)	May 18, 2023 USD ($)	Dec. 31, 2023 USD ($)
PROLEUKIN ACQUISITION
Upfront payment	£ 166.9	$ 207.2	$ 210.2
Payment for certain inventory	£ 2.4	$ 3

PROLEUKIN ACQUISITION - Cash co

PROLEUKIN ACQUISITION - Cash consideration and allocated fair value of assets acquired and liability assumed (Details) - PROLEUKIN - USD ($) $ in Thousands		12 Months Ended
	May 18, 2023	Dec. 31, 2023
Total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed
Cash	$ 35
Inventory	9,688
Deferred tax liability	(20,352)
Total cost of acquisition	222,672	$ 222,700
Developed technology
Total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed
Intangible assets	232,665
Assembled workforce
Total cash consideration and allocated acquisition date fair values of assets acquired and liabilities assumed
Intangible assets	$ 636

PROLEUKIN ACQUISITION - Additio

PROLEUKIN ACQUISITION - Additional information (Details) - PROLEUKIN $ in Thousands, £ in Millions			12 Months Ended
	May 18, 2023 GBP (£)	May 18, 2023 USD ($)	Dec. 31, 2023 USD ($)
PROLEUKIN ACQUISITION
Total Cost of Acquisition		$ 222,672	$ 222,700
Cash payment	£ 166.9	207,200	210,200
Direct transaction costs incurred			$ 12,500
Contingent cash payments, milestone payment	£ 41.7	$ 50,000
Deferred consideration term	12 years	12 years
Assembled workforce
PROLEUKIN ACQUISITION
Expected useful life of intangible assets	15 years	15 years
Assembled workforce | Selling, general and administrative
PROLEUKIN ACQUISITION
Expected useful life of intangible assets	3 years	3 years

INTANGIBLE ASSETS, NET (Details

INTANGIBLE ASSETS, NET (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Gross carrying amounts and net book value of intangible assets
Gross carrying amounts	$ 239,264
Accumulated amortization	(10,006)
Intangible assets, net	229,258
Amortization expense	9,849	$ 0
Total estimated amortization of the Company's intangible assets:
Years ending December 31, 2024	16,100
Years ending December 31, 2025	16,100
Years ending December 31, 2026	16,000
Years ending December 31, 2027	15,900
Years ending December 31, 2028	15,900
Developed technology
Gross carrying amounts and net book value of intangible assets
Gross carrying amounts	238,612
Accumulated amortization	(9,871)
Intangible assets, net	228,741
Assembled workforce
Gross carrying amounts and net book value of intangible assets
Gross carrying amounts	652
Accumulated amortization	(135)
Intangible assets, net	$ 517

INVENTORY (Details)

INVENTORY (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Inventories
Work in process	$ 5,749
Finished goods	4,623
Total inventory	$ 10,372

REVENUE (Details)

REVENUE (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
REVENUE
Total revenue	$ 1,189
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:ProductMember
Outside of U.S.
REVENUE
Total revenue	$ 1,200
In U.S.
REVENUE
Total revenue	$ 0
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	us-gaap:ProductMember

PROPERTY AND EQUIPMENT, NET - (

PROPERTY AND EQUIPMENT, NET - (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	$ 141,943	$ 121,950
Less: Accumulated depreciation and amortization	(27,913)	(16,718)
Property and equipment, net	114,030	105,232
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	76,804	74,305
Lab, process, and validation equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	23,131	22,136
Utility equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	5,990	5,951
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	3,297	2,927
Computer software
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	7,772	6,736
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	542	695
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	306	82
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	$ 24,101	$ 9,118

PROPERTY AND EQUIPMENT, NET - O

PROPERTY AND EQUIPMENT, NET - Other information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 11,568	$ 9,310	$ 3,111
Commercial Manufacturing Facility Agreement
Property, Plant and Equipment [Line Items]
Fixed asset additions	$ 2,600	$ 27,200

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
ACCRUED EXPENSES
Employee and consultant related expenses	$ 34,814	$ 20,188
Clinical related	10,911	14,812
Manufacturing related	10,893	4,467
Facilities related	2,437	6,510
Legal and related services	1,610	3,015
Inventory related	2,148
Other accrued expenses	6,593	3,303
Total accrued expenses	$ 69,406	$ 52,295

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Nov. 18, 2023	Jul. 13, 2023	Jun. 08, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 16, 2023	Jun. 06, 2023	Jun. 05, 2023	Mar. 13, 2023	Mar. 12, 2023	Jun. 10, 2022	Jan. 12, 2022	Jan. 11, 2022	Sep. 22, 2021	Apr. 22, 2018
Common Stock
Common stock, shares authorized				500,000,000	300,000,000
Common stock, par or stated value per share				$ 0.000041666	$ 0.000041666
Common stock, shares issued				256,135,715	187,812,072
Common stock, shares outstanding				256,135,715	187,812,072
Common stock issued, net of offering costs (in shares)		23,000,000
Proceeds from the issuance of common stock, net				$ 463,281	$ 189,502	$ 203,156
Weighted average grant date fair value, options granted				$ 4.91	$ 8.29	$ 22.28
Common stock issued upon exercise of stock options (in shares)		3,000,000
Share price (in dollars per share)		$ 7.50
Net proceeds from public offering		$ 161,500
Intrinsic value of options exercised				$ 10	$ 40	$ 21,300
Common Stock
Common Stock
Common stock issued upon exercise of stock options (in shares)				8,860	203,579	2,822,617
At the Market Offering Program
Common Stock
Maximum percentage of commission	3%
Common stock issued, net of offering costs (in shares)				44,080,226	29,788,993
Weighted average price				$ 6.99	$ 6.52
Proceeds from the issuance of common stock				$ 301,700	$ 189,500
Second Sales Agreement
Common Stock
Maximum amount of shares to be issued	$ 500,000
2023 Sales Agreement
Common Stock
Maximum amount of shares to be issued							$ 450,000
Series A Convertible Preferred Stock
Common Stock
Preferred stock, shares authorized				17,000	17,000
Preferred stock, par or stated value per share				$ 0.001	$ 0.001
Conversion of Stock, shares converted				0	0
Conversion of stock, shares issued				500
Preferred stock, shares outstanding				194	194
Series A Convertible Preferred Stock | Common Stock
Common Stock
Common stock available in conversion, shares				97,000	97,000
Series A Convertible Preferred Stock | Private Placement
Common Stock
Preferred stock, par or stated value per share				$ 1,000
Convertible price per share				$ 2
Series B Convertible Preferred Stock
Common Stock
Preferred stock, shares authorized				11,500,000	11,500,000
Preferred stock, par or stated value per share				$ 0.001	$ 0.001
Conversion of Stock, shares converted				1
Convertible price per share				$ 4.75
Preferred stock, shares outstanding				2,842,158	2,842,158
Series B Convertible Preferred Stock | Issuance Of Common Stock Upon Conversion Of Preferred Stock
Common Stock
Conversion of stock, shares issued				0	0
Series B Convertible Preferred Stock | Common Stock
Common Stock
Preferred stock, shares outstanding				2,842,158	2,842,158
Series B Convertible Preferred Stock | IPO
Common Stock
Preferred stock, shares authorized				11,500,000
Convertible price per share				$ 4.75
Blank check
Common Stock
Preferred stock, shares authorized				50,000,000
Employee Stock Option [Member]
Common Stock
Unrecognized compensation cost				$ 31,700
Unrecognized compensation cost recognition period				1 year 10 months 2 days
RSUs and PRSUs
Common Stock
Unrecognized compensation cost				$ 19,900	$ 20,600
Unrecognized compensation cost recognition period				1 year 7 months 24 days	1 year 8 months 19 days
Aggregate intrinsic value of outstanding non-vested RSUs & PRSUs				$ 28,100	$ 14,500
Vested				1,253,465
Granted				2,729,348
2014 Equity Incentive Plan
Common Stock
Number of shares available				275,625
The 2018 Plan
Common Stock
Number of shares available				9,906,666
Shares authorized			14,000,000					29,700,000				20,700,000				6,000,000
2020 ESPP
Common Stock
Common stock issued, net of offering costs (in shares)				435,459	262,701
Shares authorized			500,000					1,400,000	500,000
Percentage of purchase price			85%
Stock-based compensation expense				$ 1,200	$ 1,300	$ 1,200
Unrecognized compensation cost				$ 600
Unrecognized compensation cost recognition period				5 months 12 days
Proceeds from Issuance or Sale of Equity				$ 2,400	$ 1,700
2021 Inducement Plan
Common Stock
Number of shares available				349,428
Shares authorized										2,250,000	1,750,000		1,750,000	1,000,000	1,000,000

STOCKHOLDERS' EQUITY - Stock Op

STOCKHOLDERS' EQUITY - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 13, 2023	Dec. 31, 2023
Number of Options
Exercised	(3,000,000)
Employee Stock Option [Member]
Number of Options
Outstanding, beginning balance		15,240,197
Issued		5,379,670
Exercised		(8,860)
Expired/Cancelled		(1,711,158)
Outstanding, ending balance		18,899,849
Ending vested and expected to vest		18,899,849
Options exercisable		12,160,135
Weighted Average Exercise Price
Outstanding, beginning balance		$ 22.45
Issued		7.04
Exercised		7.10
Expired/Cancelled		17.01
Outstanding, ending balance		18.57
Ending vested and expected to vest		18.57
Options exercisable		$ 23.40
Weighted Average Remaining Contractual Life
Options outstanding, remaining term		6 years 9 months
Ending vested and expected to vest, remaining term		6 years 9 months
Options exercisable, remaining term		5 years 6 months 14 days
Aggregate Intrinsic Value
Option at ending balance		$ 7,065
Ending vested and expected to vest		7,065
Option exercisable		$ 1,337

STOCKHOLDERS' EQUITY - Restrict

STOCKHOLDERS' EQUITY - Restricted Stock Units and Performance Restricted Stock Units (Details) - RSUs and PRSUs	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Number of Shares
Outstanding, Beginning Balance | shares	2,436,764
Granted | shares	2,729,348
Vested/Released | shares	(1,253,465)
Canceled/forfeited | shares	(458,746)
Outstanding, Ending balance | shares	3,453,901
Ending vested and expected to vest | shares	3,453,901
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 14.74
Weighted Average Grant Date Fair Value, Granted | $ / shares	7.19
Weighted Average Grant Date Fair Value, Vested/Released | $ / shares	16.17
Weighted Average Grant Date Fair Value, Canceled/forfeited | $ / shares	9.35
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	8.97
Weighted Average Grant Date Fair Value, Ending vested and expected to vest | $ / shares	$ 8.97

STOCKHOLDERS' EQUITY - Stock ba

STOCKHOLDERS' EQUITY - Stock based expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Total stock-based compensation expenses	$ 62,625	$ 84,022	$ 69,765
Research and development
Total stock-based compensation expenses	34,926	50,242	40,833
General and administrative
Total stock-based compensation expenses	$ 27,699	$ 33,780	$ 28,932

STOCKHOLDERS' EQUITY - Stock-ba

STOCKHOLDERS' EQUITY - Stock-based compensation by instrument (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Total stock-based compensation expenses	$ 62,625	$ 84,022	$ 69,765
Employee Stock Option [Member]
Total stock-based compensation expenses	45,340	58,308	56,305
Restricted stock units
Total stock-based compensation expenses	16,062	24,436	12,247
2020 ESPP
Total stock-based compensation expenses	$ 1,223	$ 1,278	$ 1,213

STOCKHOLDERS' EQUITY - Assumpti

STOCKHOLDERS' EQUITY - Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Stock Option [Member]
Expected dividend yield	0%	0%	0%
Employee Stock Option [Member] | Minimum
Expected term (years)	5 years 2 months 4 days	4 years 11 months 8 days	4 years 11 months 8 days
Expected volatility	83.63%	73.73%	70.35%
Risk-free interest rate	3.59%	1.25%	0.36%
Employee Stock Option [Member] | Maximum
Expected term (years)	5 years 4 months 13 days	5 years 1 month 13 days	5 years 3 months 10 days
Expected volatility	84.21%	83.90%	73.88%
Risk-free interest rate	4.60%	4.05%	0.97%
2020 ESPP
Expected term (years)	6 months	6 months	6 months
Expected dividend yield	0%		0%
2020 ESPP | Minimum
Expected volatility	72.96%	73.02%	52.04%
Risk-free interest rate	5.38%	1.98%	0.06%
2020 ESPP | Maximum
Expected volatility	83.36%	137.42%	94.56%
Risk-free interest rate	5.40%	4.78%	0.13%

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
EMPLOYEE BENEFIT PLAN
Defined contribution plan	$ 4.1	$ 3	$ 2.2

INCOME TAXES - Net deferred tax

INCOME TAXES - Net deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred income tax asset:
Net operating loss carry forwards	$ 255,639	$ 225,904
Stock-based compensation	28,609	24,920
Tax credit carryforwards	58,565	46,957
Lease liabilities	16,024	18,017
Capitalized R&D	99,107	47,755
Reserves and accruals	6,540	3,997
Deferred tax assets before valuation allowance	464,484	367,550
Less: valuation allowance	(446,853)	(350,418)
Net deferred income tax assets	17,631	17,132
Deferred tax liabilities:
Right-of-use assets	(13,381)	(15,578)
Depreciation and amortization	(21,597)	(1,554)
Net deferred tax assets (liabilities)	$ (17,347)	$ 0

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of the effective income tax rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
INCOME TAXES
Federal statutory tax rate	21%	21%	21%
Orphan drug and research credits	2%	1%	2%
Permanent and other differences	(1.00%)	(1.00%)	0%
Stock Based Compensation	(1.00%)	(1.00%)	0%
State tax, net of federal benefit	1%	1%	0%
Effective Income Tax Rate Reconciliation Expected Rate Total	22%	21%	23%
Valuation allowance	(21.00%)	(21.00%)	(23.00%)
Effective tax rate	0.78%	0%	0%

INCOME TAXES - Other informatio

INCOME TAXES - Other information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Contingency [Line Items]
Operating loss carryovers definite to be expired	$ 142,400
Operating loss carryovers indefinite	1,000,000
Change in valuation allowance	96,400	$ 82,900	$ 78,100
Interest or penalties on unpaid tax	0	$ 0	$ 0
Federal income tax
Income Tax Contingency [Line Items]
Net operating loss carryforwards (NOLs)	1,200,000
State income tax
Income Tax Contingency [Line Items]
Net operating loss carryforwards (NOLs)	$ 180,000

INCOME TAXES - Unrecognized ben

INCOME TAXES - Unrecognized benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
INCOME TAXES
Unrecognized benefit - beginning of period	$ 21,645	$ 18,171	$ 14,432
Gross decreases - prior period tax positions	0	0	(159)
Gross increase current period tax positions	4,462	3,474	3,898
Unrecognized benefit - end of period	$ 26,107	$ 21,645	$ 18,171

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	May 18, 2023
INCOME TAXES
Tax benefit	$ (3,479)	$ 0	$ 0
Deferred tax liability	$ 17,300			$ 20,400
Effective tax rates	0.78%	0%	0%
Federal statutory tax rate	21%	21%	21%

LICENSES AND AGREEMENTS (Detail

LICENSES AND AGREEMENTS (Details) $ in Thousands

1 Months Ended

12 Months Ended

May 18, 2023 USD ($) item

May 07, 2018 USD ($)

Apr. 17, 2017 USD ($)

Jun. 28, 2014 USD ($)

Oct. 31, 2022 item

Aug. 31, 2021

Nov. 30, 2016 item

Aug. 31, 2016 USD ($)

Aug. 31, 2011

Dec. 31, 2023 USD ($)

Dec. 31, 2022 USD ($)

Dec. 31, 2021 USD ($)

Dec. 31, 2020 USD ($)

Research and development

$ 344,077

$ 294,781

$ 259,039

Research and development arrangement, contract to perform for others, costs incurred, gross

5,300

Strategic Alliance Agreement

Research and development

0

200

500

Research Collaboration And Clinical Grant Agreement

Research and development

0

Manufacturing and Supply Agreement With Boehringer Ingelheim Biopharmaceuticals GmbH

Renewal term of agreement

2 years

Maximum | Strategic Alliance Agreement

Research and development arrangement, contract to perform for others, costs incurred, gross

$ 14,200

Sponsored research agreement

Research and development

200

600

300

First WuXi Manufacturing and Services Agreement

Agreement term

3 years

Number Of Suites Under The Agreement | item

2

Number of statements of work under the agreement | item

2

Second WuXi Manufacturing and Services Agreement

Agreement term

3 years

Number Of Suites Under The Agreement | item

2

Termination notice period

120 days

Period to address issues within receipt of FDA response letter in collaboration arrangement

90 days

Patent license agreement related to the development and manufacture of TIL therapies

Research and development

600

0

Amount of collaborative arrangement required to be remitted

$ 1,500

Period of collaborative arrangement required to be remitted

60 days

Cooperative Research and Development Agreement

Agreement term

3 years

5 years

Research and development

$ 500

$ 2,000

2,000

2,000

Notification Period To Terminate Agreement

60 days

Research Collaboration And Clinical Grant Agreements With Moffitt

Research and development

100

100

Moffitt License Agreement One

Agreement term

20 years

Research and development

0

0

0

Payments for upfront licensing fee

$ 100

Moffitt License Agreement Two

Research and development

100

200

100

Payments for upfront licensing fee

$ 100

Additional milestone payable

400

Moffitt License Agreement Two, Amended and Restated

Payments for upfront licensing fee

200

WuXi Apptech, Inc - Manufacturing and Services Agreement

Research and development

17,300

14,200

17,500

Cellectis S.A

Research and development

400

400

$ 400

Novartis Pharma AG and Related Entities - License Agreement

Research and development

0

$ 0

$ 10,000

Number of historical master cell bank license and working cell bank transfer agreement | item

2

Number of historical license agreement | item

1

Amount of milestone payment made during the period under the license agreement

$ 0

Percent of milestone payments reimbursable

25%

Novartis Pharma AG and Related Entities - License Agreement | Non-US

Amount of milestone payments payable under the license agreement

$ 15,000

Novartis Pharma AG and Related Entities - License Agreement | Maximum | UNITED STATES

Amount of milestone payments payable under the license agreement

$ 30,000

LICENSES AND AGREEMENTS - Estim

LICENSES AND AGREEMENTS - Estimated purchase obligations (Details) - Manufacturing and Supply Agreement With Boehringer Ingelheim Biopharmaceuticals GmbH $ in Millions	Dec. 31, 2023 USD ($)
Years ending December 31, 2024	$ 8.2
Years ending December 31, 2025	11.4
Years ending December 31, 2026	7.3
Years ending December 31, 2027	$ 7.3

LEASES - Additional information

LEASES - Additional information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) ft²	Dec. 31, 2022 USD ($)
Option to extend	true
Tenant improvement allowance	$ 8,200,000
Tenant improvement allowance reimbursed		$ 6,432,000
Minimum
Term of contract in years	1 year
Maximum
Term of contract in years	20 years
Office Space | Minimum
Term of contract in years	12 months
Office Space | Philadelphia, Pennsylvania
Area of land | ft²	136,000
Furniture and equipment | Maximum
Term of contract in years	12 months
New Headquarters Lease | Office Space | San Carlos, California
Area of land | ft²	49,918
Tenant improvement allowance reimbursed	$ 0	$ 6,400,000

LEASES - Right-of-use asset and

LEASES - Right-of-use asset and lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
LEASES
Operating lease right-of-use assets	$ 62,515	$ 73,015
Operating lease liabilities
Current portion included in current liabilities	7,777	12,587
Long-term portion included in non-current liabilities	67,085	71,859
Total operating lease liabilities	$ 74,862	$ 84,446

LEASES - Components of lease ex

LEASES - Components of lease expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
LEASES
Operating lease cost	$ 17,786	$ 17,657
Variable lease cost	7,629	5,447
Short-term lease cost	335	154
Total lease cost	25,750	23,258
Cash paid for amounts included in the measurement of lease liabilities included in cash flows from operations	16,871	14,209
Tenant improvement allowance received for amounts included in the measurement of lease liabilities included in cash flows from operations		6,432
Right-of-use assets obtained from entering new leases	177	553
Increase in right-of-use assets from lease modifications	$ 1,033	$ 15,304
Weighted-average remaining lease terms (years)	13 years 1 month 2 days	12 years 10 months 24 days
Weighted-average discount rates	7.40%	7.50%

LEASES - Maturities of the Comp

LEASES - Maturities of the Company's operating lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
2024	$ 12,928
2025	8,324
2026	7,989
2027	8,186
2028	8,389
Thereafter	75,438
Total lease payments	121,254
Less: Present value adjustment	(46,392)
Operating lease liabilities	74,862	$ 84,446
Facility leases
2024	8,579
2025	8,324
2026	7,989
2027	8,186
2028	8,389
Thereafter	75,438
Total lease payments	116,905
Less: Present value adjustment	(46,254)
Operating lease liabilities	70,651
CMO embedded leases
2024	4,349
Total lease payments	4,349
Less: Present value adjustment	(138)
Operating lease liabilities	$ 4,211

LEGAL PROCEEDINGS (Details)

LEGAL PROCEEDINGS (Details)			1 Months Ended
	May 12, 2020 USD ($)	Apr. 08, 2016 USD ($) item	Nov. 30, 2012 USD ($)	Jun. 30, 2012 USD ($)
Equity claim	$ 47,420
Solomon Capital LLC Litigation
Proceeds from lawsuit filed			$ 200,000	$ 100,000
Face amount		$ 200,000
Debt instrument, convertible, number of equity instruments | item		1,110
Reverse split ratio		0.01
Estimate of possible loss		$ 1,500,000
Damages claimed		$ 500,000

LONG-TERM NOTE PAYABLE (Details

LONG-TERM NOTE PAYABLE (Details) - Job Creation Loan	Jan. 26, 2021 USD ($)
LONG-TERM NOTE PAYABLE
Principal amount	$ 1,000,000
Loan term	5 years
Interest rate (as percent)	0%
Lender amount	$ 2,000
Average salary	$ 80,000
Average number of term	5 years

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Feb. 22, 2024	Jul. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SUBSEQUENT EVENTS
Common stock issued, net of offering costs (in shares)		23,000,000
Public offering price		$ 7.50
Proceeds from the issuance of common stock, net			$ 463,281	$ 189,502	$ 203,156
Subsequent Event | Public Offering | Common Stock
SUBSEQUENT EVENTS
Common stock issued, net of offering costs (in shares)	23,014,000
Public offering price	$ 9.15
Proceeds from the issuance of common stock, net	$ 197,100

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (444,037)	$ (395,893)	$ (342,252)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false