Iovance Biotherapeutics (IOVA) 10-K 24 Feb 22 2021 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Feb. 17, 2022	Jun. 30, 2021
Document And Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
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
Title of 12(b) Security	Common Stock, $ 0.000041666 Par Value per Share
Trading Symbol	IOVA
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float				$ 3.8
Entity Common Stock, Shares Outstanding			157,168,321
Auditor Name	Ernst & Young LLP	Marcum LLP
Auditor Firm ID	42	688
Auditor Location	Redwood City, California	New York, NY
Entity Central Index Key	0001425205
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents	$ 78,229	$ 67,329
Short-term investments	426,181	562,108
Prepaid expenses and other assets	3,546	6,663
Total Current Assets	507,956	636,100
Property and equipment, net	100,938	59,159
Operating lease right-of-use assets	68,983	54,756
Long-term investments	91,588
Restricted cash	6,084	5,525
Long-term assets	1,784	12,918
Total Assets	777,333	768,458
Current Liabilities
Accounts payable	27,377	13,513
Accrued expenses	56,766	35,074
Operating lease liabilities - current	5,057	6,284
Total Current Liabilities	89,200	54,871
Non-Current Liabilities
Operating lease liabilities - noncurrent	65,474	45,375
Long-term note payable	1,000
Other liabilities		11,714
Total Non-Current Liabilities	66,474	57,089
Total Liabilities	155,674	111,960
Commitments and contingencies
Stockholders' Equity
Accumulated other comprehensive (loss) income	(601)	19
Additional paid-in capital	1,794,695	1,486,662
Accumulated deficit	(1,172,445)	(830,193)
Total Stockholders' Equity	621,659	656,498
Total Liabilities and Stockholders' Equity	777,333	768,458
Series B Convertible Preferred Stock
Stockholders' Equity
Preferred stock, Value	$ 3	$ 4

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Common stock, par or stated value per share	$ 0.000041666	$ 0.000041666
Common stock, shares authorized	300,000,000	300,000,000
Common Stock, Shares, Issued	157,004,742	146,874,917
Common Stock, Shares, Outstanding	157,004,742	147,874,917
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	3,581,119
Preferred stock, shares outstanding	2,842,158	3,581,119

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Costs and expenses
Research and development expenses	$ 259,039	$ 201,727	$ 166,023
General and administrative expenses	83,664	60,210	40,849
Total costs and expenses	342,703	261,937	206,872
Loss from operations	(342,703)	(261,937)	(206,872)
Other income
Interest income, net	451	2,356	9,316
Net Loss	$ (342,252)	$ (259,581)	$ (197,556)
Net Loss Per Share of Common Stock, Basic	$ (2.23)	$ (1.88)	$ (1.59)
Net Loss Per Share of Common Stock, Diluted	$ (2.23)	$ (1.88)	$ (1.59)
Weighted Average Shares of Common Stock Outstanding, Basic	153,406	138,301	124,336
Weighted Average Shares of Common Stock Outstanding, Diluted	153,406	138,301	124,336

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Comprehensive Loss
Net Loss	$ (342,252)	$ (259,581)	$ (197,556)
Other comprehensive loss / (gain):
Unrealized loss / (gain) on short-term investments	(620)	(201)	262
Comprehensive Loss	$ (342,872)	$ (259,782)	$ (197,294)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Series A Convertible Preferred StockPreferred Stock	Series B Convertible Preferred StockPreferred Stock	Cumulative Effect, Period of Adoption, Adjustment [Member]Additional Paid-In Capital	Cumulative Effect, Period of Adoption, Adjustment [Member]Accumulated Deficit	Common Stock	Additional Paid-In Capital	Accumulated Comprehensive Income (Loss)	Accumulated Deficit	Total
Beginning Balance at Dec. 31, 2018		$ 6			$ 5	$ 838,984	$ (42)	$ (372,760)	$ 466,193
Beginning Balance (in Shares) at Dec. 31, 2018	194	5,854,845			123,415,576
Stock-based compensation expense						24,277			24,277
Vesting of restricted shares issued for services					$ 1	(1)
Vesting of restricted shares issued for services (in shares)					27,514
Tax payments related to shares withheld for vested restricted stock units						(312)			(312)
Common stock issued upon exercise of stock options						6,443			6,443
Common stock issued upon exercise of stock options (in shares)					727,492
Unrealized loss / (gain) on short-term investments							262		262
Conversion of convertible preferred stock into common stock		$ (2)				2
Conversion of convertible preferred stock into common stock (in Shares)		(2,273,726)			2,273,726
Cancellation of common shares from settlement of dispute					$ (1)	(335)			(336)
Cancellation of common shares from settlement of dispute (In Shares)					(32,500)
Net loss								(197,556)	(197,556)
Ending Balance at Dec. 31, 2019		$ 4			$ 5	869,354	220	(570,612)	298,971
Ending Balance (in Shares) at Dec. 31, 2019	194	3,581,119			126,411,808
Adoption of ASU 2018-07			$ 296	$ (296)
Stock-based compensation expense						40,775			40,775
Vesting of restricted shares issued for services						112			112
Vesting of restricted shares issued for services (in shares)					13,449
Tax payments related to shares withheld for vested restricted stock units						(284)			(284)
Common stock issued upon exercise of stock options						9,663			9,663
Common stock issued upon exercise of stock options (in shares)					973,854
Common stock sold in public offering, net of offering costs					$ 1	567,042			567,043
Common stock sold in public offering, net of offering costs (in shares)					19,475,806
Unrealized loss / (gain) on short-term investments							(201)		(201)
Net loss								(259,581)	(259,581)
Ending Balance at Dec. 31, 2020		$ 4			$ 6	1,486,662	19	(830,193)	656,498
Ending 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 sold in public offering, net of offering costs					$ 1	203,155			203,156
Common stock sold in public offering, net of offering costs (in shares)					6,474,099
Common stock issued from preferred stock conversion		$ (1)				1
Common stock issued from preferred stock conversion (in Shares)		(738,961)			738,961
Unrealized loss / (gain) on short-term 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

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows from Operating Activities
Net loss	$ (342,252)	$ (259,581)	$ (197,556)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	69,765	40,887	24,277
Amortization of right of use asset	10,869	7,572	6,954
Depreciation and amortization	3,111	1,140	1,169
Gain on settlement of dispute			(336)
Accretion (amortization) of discounts and premiums on investments	6,013	1,865	(3,421)
Loss on disposal of assets			16
Changes in assets and liabilities:
Prepaid expenses, other assets, and long-term assets	2,775	(6,688)	(3,278)
Operating lease liabilities	(5,882)	(11,474)	(6,148)
Accounts payable	6,976	(2,964)	12,706
Accrued expenses and other liabilities	20,684	24,109	6,728
Net cash used in operating activities	(227,941)	(205,134)	(158,889)
Cash Flows from Investing Activities
Maturities of investments	762,914	676,601	514,601
Purchase of investments	(725,208)	(947,663)	(417,659)
Purchase of property and equipment	(37,574)	(46,791)	(6,917)
Net cash (used in) provided by investing activities	132	(317,853)	90,025
Cash Flows from Financing Activities
Tax payments related to shares withheld for vested restricted stock units		(284)	(312)
Proceeds from the issuance of common stock upon purchase of employee stock purchase plan	1,586
Proceeds from the issuance of common stock upon exercise of options	33,526	9,663	6,443
Proceeds from the issuance of common stock, net	203,156	567,043
Proceeds from the issuance of debt	1,000
Net cash provided in financing activities	239,268	576,422	6,131
Net increase (decrease) in cash, cash equivalents, and restricted cash	11,459	53,435	(62,733)
Cash, Cash Equivalents, and Restricted Cash, Beginning of Period	72,854	19,419	82,152
Cash, Cash Equivalents, and Restricted Cash, End of Period	84,313	72,854	19,419
Supplemental disclosure of non-cash investing and financing activities:
Net unrealized loss on short-term investments	(620)	(201)	262
Acquisitions of property and equipment included in accounts payable and accrued expense	(7,316)	(5,094)	122
Conversion of convertible preferred stock to common stock	(1)		(2)
Vesting of restricted stock units			1
Lease liabilities arising from obtaining right-of-use asset from new leases	17,275	45,968	14,827
Lease liabilities arising from obtaining right-of-use asset from lease modifications	$ 7,800	$ 826	$ 4,811

GENERAL ORGANIZATION AND BUSINE

GENERAL ORGANIZATION AND BUSINESS	12 Months Ended
	Dec. 31, 2021
GENERAL ORGANIZATION AND BUSINESS
GENERAL ORGANIZATION AND BUSINESS	NOTE 1. GENERAL ORGANIZATION, BUSINESS AND LIQUIDITY General Organization and Business Iovance Biotherapeutics, Inc. (the “Company”) is a clinical-stage biopharmaceutical company pioneering a transformational approach to cure cancer by harnessing the human immune system’s ability to recognize and destroy diverse cancer cells in each patient. Tumor infiltrating lymphocyte (“TIL”) therapy is an autologous cell therapy platform technology that was originally developed by the National Cancer Institute (“NCI”), which conducted initial clinical trials in diseases such as metastatic melanoma and cervical cancer, as well as non-small cell lung cancer. The Company’s mission is to be the global leader in innovating, developing and delivering TIL therapy for patients with cancer. The Company has developed a new, shorter proprietary TIL manufacturing process known as Generation 2 (“Gen 2”), which yields a cryopreserved TIL product. This centralized, proprietary, and scalable manufacturing method is being investigated in multiple indications. The Company’s lead product candidates include lifileucel for metastatic melanoma and metastatic cervical cancer, as well as LN-145 for metastatic non-small cell lung cancer (“NSCLC”). In addition, the Company is investigating the effectiveness and safety of combinations of TIL therapy with immune checkpoint inhibitors (“ICI”), in metastatic melanoma, cervical cancer, NSCLC, and head and neck squamous cell carcinoma (“HNSCC”). The Company is investigating peripheral blood lymphocyte (“PBL”) therapy for patients with relapsed or refractory chronic lymphocytic leukemia (“CLL”) and small lymphocytic lymphoma (“SLL”) through its sponsored trials. The Company is also investigating the potential for TIL therapy in other oncology indications through academic collaborations with leading cancer research centers. On June 1, 2017, the Company reincorporated from a Nevada corporation to a Delaware corporation. Liquidity The Company is currently engaged in the development of therapeutics to fight cancer, specifically solid tumors. The Company currently does not have any commercial products and has not yet generated any revenues from its business, nor does the Company currently anticipate that it will generate any significant revenues from the sale or licensing of any of its product candidates during the 12 months from the date these financial statements are issued. The Company has incurred a net loss of $342.3 million for the year ended December 31, 2021 and used $227.9 million of cash in its operating activities during the year ended December 31, 2021. As of December 31, 2021, the Company had $602.1 million in cash, cash equivalents, investments, and restricted cash ($78.2 million of cash and cash equivalents, $426.2 million in short-term investments, $91.6 million in long-term investments and $6.1 million in restricted cash). The Company expects to continue its research and development activities, increase pre-commercial activities and complete the construction of the tenant improvements for the Iovance Cell Therapy Center (the “ i CTC”) as well as its new corporate headquarters’ office in San Carlos, California, all of which are expected to increase the amount of cash used during 2022 and beyond. Specifically, the Company expects continued spending on its current and planned clinical trials, continued expansion of manufacturing activities, higher payroll expenses as the Company increases its professional and scientific staff and continuation of pre-commercial activities. Based on the funds the Company has available as of the date these financial statements are issued, 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 financial statements are issued. Concentrations of Risk 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 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 PRACTICES	12 Months Ended
	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES	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 and carries them at fair value. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive loss or income. Impairment losses related to credit losses (if any) are recorded as an allowance for credit losses with an offsetting entry to net loss. No impairment losses related to credit losses were recognized for the years ended December 31, 2021 and 2020. 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 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, currently $6.1 million in a segregated bank account in connection with three letters of credit, one for $5.45 million for the benefit of the landlord for 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, December 31, December 31, ​ ​ 2021 ​ 2020 ​ 2019 Cash and cash equivalents ​ $ 78,229 ​ $ 67,329 ​ $ 13,969 Restricted cash ​ 6,084 ​ 5,525 ​ 5,450 Total cash, cash equivalents and restricted cash ​ $ 84,313 ​ $ 72,854 ​ $ 19,419 ​ 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 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, 2021, 2020, and 2019, the Company did not recognize any impairments for its property and equipment. ​ 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 shares 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, 2021, 2020, and 2019, 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, ​ 2021 2020 2019 Stock options ​ 12,520,865 12,615,638 9,494,712 Employee Stock Purchase Plan ​ 85,227 37,259 — Restricted stock units ​ 1,110,010 — 22,916 Series A Convertible Preferred Stock* ​ 97,000 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 3,581,119 ​ ​ 16,655,260 16,331,016 13,195,747 ​ *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. ​ Fair Value Measurements Under Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures 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 and long-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. The Company’s financial instruments consist of Level 1 and Level 2 assets. 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 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. ​ Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“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 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. All intercompany accounts and transactions have been eliminated. The U.S. dollar is the functional currency for all the Company's consolidated operations. Leases The Company determines if an arrangement includes a lease at inception. Operating leases are included in its Consolidated Balance Sheets as Operating lease right-of-use assets and Operating lease liabilities as of December 31, 2021. 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 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 date or the date of adoption of Accounting Standards Update (“ASU”) No. 2016-02 and No. 2018-10 (together “Topic 842”). 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. The Company has elected not to apply the recognition requirements of Topic 842 for short-term leases. For lease agreements entered into after the adoption of Topic 842 that include lease and non-lease components, such components are generally accounted for separately. Stock-Based Compensation The Company periodically grants stock options to employees as compensation for services rendered. The Company accounts for all stock-based payment awards made to employees, including the employee stock purchase plans, 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. In accordance with ASU No. 2018-07, Compensation-Stock Compensation 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 life 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”) and restricted stock awards (“RSAs”) from time to time as part of its equity incentive plans. The Company measures the compensation cost with respect to RSUs and RSAs 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 and RSAs is based on the closing price of the Company’s common stock on the grant date. 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 estimates of 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 estimates of services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. The Company determines its estimates 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 study protocol. The Company’s estimates for clinical investigator costs and 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 study 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 study, 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 treatments 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 study treatment. The Company accrues for 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. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its results of operations. The Company’s historical estimates have not been materially different from actual amounts recorded. ​ General and Administrative Expenses General and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in executive, finance, accounting, legal, investor relations, facilities, business development, marketing, commercial and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses, sublicense royalty expenses, legal fees relating to corporate matters, insurance, public company expenses relating to maintaining compliance with Nasdaq listing rules and Securities and Exchange Commission (“SEC”) requirements, investor relations costs, and fees for accounting and consulting services. General and administrative costs are expensed as incurred. 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 interest and penalties, accounting in interim periods, disclosure, and transition. The Company will classify as income tax expense any interest and penalties. The Company has no material uncertain tax positions for any of the reporting periods presented. 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, 2021, and 2020, respectively, the Company’s cash balances were in excess of insured limits maintained at the financial institutions. 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 Recently Issued and Adopted Accounting Standards Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

CASH EQUIVALENTS AND INVESTMENT

CASH EQUIVALENTS AND INVESTMENTS	12 Months Ended
	Dec. 31, 2021
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, 2021 and December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2021 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 247,287 ​ $ — ​ $ (520) ​ $ 246,767 U.S. government agency securities ​ 5,104 ​ — ​ (7) ​ 5,097 Corporate securities ​ ​ 35,627 ​ ​ — ​ ​ (39) ​ ​ 35,588 Commercial paper ​ ​ 235,352 ​ ​ 10 ​ ​ (46) ​ ​ 235,316 Money market funds ​ ​ 56,250 ​ ​ — ​ ​ — ​ ​ 56,250 Total investments ​ $ 579,620 ​ $ 10 ​ $ (612) ​ $ 579,018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2020 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 470,108 ​ $ 30 ​ $ (29) ​ $ 470,109 U.S. government agency securities ​ 91,981 ​ 20 ​ (2) ​ 91,999 Money market funds ​ ​ 49,720 ​ ​ — ​ ​ — ​ ​ 49,720 Total ​ $ 611,809 ​ $ 50 ​ $ (31) ​ $ 611,828 ​ The fair value of cash equivalents and investments as of December 31, 2021 and December 31, 2020 are classified as follows in the Company’s Consolidated Balance Sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, Classified as: ​ 2021 2020 Cash equivalents ​ $ 61,249 ​ $ 49,720 Short-term investments ​ ​ 426,181 ​ ​ 562,108 Long-term investments ​ ​ 91,588 ​ ​ — Total investments ​ $ 579,018 ​ $ 611,828 ​ Cash equivalents in the tables above exclude cash demand deposits of $17.0 million and $17.6 million as of December 31, 2021 and 2020, respectively. Unrealized gains and losses are included in accumulated other comprehensive (loss) income, and as of December 31, 2021 and 2020 no unrealized losses on available-for-sale securities have resulted from credit risk. All available-for-sale securities held as of December 31, 2021 and December 31, 2020 had contractual maturities of less than two years. 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. The Company determined that it has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. To date, the Company has not recorded any impairment charges on its marketable securities. ​ Recurring Fair Value Measurements ​ The following table summarizes the Company’s available-for-sale investments by contractual maturity (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ Amortized Cost Fair Value Within one year ​ $ 487,718 ​ $ 487,430 One year to two years ​ ​ 91,902 ​ ​ 91,588 Total investments ​ $ 579,620 ​ $ 579,018 ​ ​ As of December 31, 2021 and 2020, the fair value of the Company’s financial assets, which consist of cash equivalents and short-term and long-term investments classified as available-for-sale securities, were measured on a recurring basis were 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, 2021 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 246,767 ​ $ — ​ $ — ​ $ 246,767 U.S. government agency securities ​ — ​ 5,097 ​ — ​ 5,097 Corporate securities ​ ​ — ​ ​ 35,588 ​ ​ — ​ ​ 35,588 Commercial paper ​ ​ — ​ ​ 235,316 ​ ​ — ​ ​ 235,316 Money market funds ​ ​ 56,250 ​ ​ — ​ ​ — ​ ​ 56,250 Total ​ $ 303,017 ​ $ 276,001 ​ $ — ​ $ 579,018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2020 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 470,109 ​ $ — ​ $ — ​ $ 470,109 U.S. government agency securities ​ 91,999 ​ — ​ — ​ 91,999 Money market funds ​ ​ 49,720 ​ ​ — ​ ​ — ​ ​ 49,720 Total ​ $ 611,828 ​ $ — ​ $ — ​ $ 611,828 ​ 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.

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2021
PROPERTY AND EQUIPMENT, NET
PROPERTY AND EQUIPMENT, NET	NOTE 4. PROPERTY AND EQUIPMENT, NET Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2021 2020 Leasehold improvements ​ $ 57,817 ​ $ 2,573 Lab, process, and validation equipment ​ ​ 8,686 ​ ​ 4,656 Utility equipment ​ 4,179 ​ — Office furniture and equipment ​ 1,244 ​ 480 Computer software ​ ​ 1,163 ​ ​ — Computer equipment ​ 674 ​ 270 Machinery and equipment ​ ​ 82 ​ ​ — Construction in progress ​ 35,782 ​ 56,758 Total Property and equipment, cost ​ 109,627 ​ 64,737 Less: Accumulated depreciation and amortization ​ (8,689) ​ (5,578) Property and equipment, net ​ $ 100,938 ​ $ 59,159 ​ Depreciation expense for the years ended December 31, 2021, 2020, and 2019 was approximately $3.1 million, $1.1 million and $1.2 million, respectively. During the year ended December 31, 2021, the Company placed $62.4 million of assets related to the i million.

ACCRUED EXPENSES

ACCRUED EXPENSES	12 Months Ended
	Dec. 31, 2021
ACCRUED EXPENSES
ACCRUED EXPENSES	NOTE 5. ACCRUED EXPENSES Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2021 2020 Accrued payroll and employee related expenses ​ $ 21,513 ​ $ 9,032 Clinical related ​ ​ 18,167 ​ ​ 15,661 Manufacturing related ​ 6,566 ​ 3,266 Facilities related ​ ​ 4,857 ​ ​ 4,342 Legal and related services ​ 1,907 ​ 1,061 Other accrued expenses ​ 3,756 ​ 1,712 Total accrued expenses ​ $ 56,766 ​ $ 35,074 ​

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2021
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 6. STOCKHOLDERS’ EQUITY Common Stock The Company’s certificate of incorporation, as amended, authorizes the issuance of up to 300,000,000 shares of the Company’s common stock, par value $0.000041666 . As of December 31, 2021, 157,004,742 shares of the Company’s common stock were issued and outstanding . Public Offerings In June 2020, the Company closed an underwritten public offering of 16,935,484 shares of the Company’s common stock at a public offering price of $31.00 per share, before underwriting discounts, which included 2,540,322 shares issued upon the exercise in full by the underwriter of its option to purchase additional shares at the public offering price less the underwriting discount (the "June 2020 Public Offering"). The gross proceeds from the offering, before deducting the underwriting discounts and commissions and other offering expenses payable by the Company, were $603.7 million, with net proceeds to the Company of $567.0 million. At the Market Offering Program On February 8, 2021, the Company entered into an Open Market Sale Agreement (the “Sales Agreement”) with Jefferies LLC (“Jefferies”) with respect to an “at the market” offering program, under which the Company may, from time to time, in its sole discretion, issue and sell through Jefferies, acting as sales agent, up to $350.0 million of shares of the Company’s common stock (the “Common Shares”). The issuance and sale, if any, of the Common Shares by the Company under the Sales Agreement will be made pursuant to a prospectus supplement, dated February 8, 2021, to the Company’s Registration Statement on Form S-3ASR, which became effective immediately upon filing with the Securities and Exchange Commission on May 27, 2020. Pursuant to the Sales 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 Sales Agreement. The Company is not obligated to make any sales of Common Shares under the Sales Agreement. The offering of Common Shares pursuant to the Sales Agreement will terminate upon the earlier to occur of (i) the issuance and sale, through Jefferies, of all Common Shares subject to the Sales Agreement and (ii) termination of the Sales Agreement in accordance with its terms. For the year ended December 31, 2021, the Company received $203.2 million in net proceeds, net of offering costs, through the sale of 6,474,099 shares of its common stock through the Sales Agreement at a weighted average price per share of $32.12, 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, 2021, 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 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, 2021 and 2020. As of December 31, 2021 and 2020, 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. During the year ended December 31, 2021, 738,961 shares of Series B Convertible Preferred Stock were converted to common stock. No shares of Series B Convertible Preferred Stock were converted to common stock during the year ended December 31, 2020. At December 31, 2021 and 2020, 2,842,158 and 3,581,119 shares of Series B Preferred Stock (that are convertible into 2,842,158 and 3,581,119 shares of common stock) remained outstanding, respectively. Equity Incentive Plans The Company has multiple equity incentive plans under which it grants awards. As of December 31, 2021, there are 60,785 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. As of December 31, 2021, 3,866,948 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 will be 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. 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, 2021, Stock Options A summary of the status of stock options as of December 31, 2021, 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 January 1, 2019 ​ 6,889,287 $ 10.25 ​ ​ ​ ​ ​ Issued ​ 4,166,600 ​ ​ 14.73 ​ ​ ​ ​ ​ Exercised ​ (727,492) ​ ​ 8.85 ​ ​ ​ ​ ​ Expired/Cancelled ​ (833,683) ​ ​ 13.87 ​ ​ ​ ​ ​ Outstanding at December 31, 2019 ​ 9,494,712 $ 12.00 ​ ​ ​ ​ ​ Issued ​ 4,981,001 ​ ​ 28.17 ​ ​ ​ ​ ​ Exercised ​ (973,854) ​ ​ 9.92 ​ ​ ​ ​ ​ Expired/Cancelled ​ (886,221) ​ ​ 18.67 ​ ​ ​ ​ ​ Outstanding at December 31, 2020 ​ 12,615,638 $ 18.08 ​ ​ ​ ​ ​ Issued ​ 5,528,724 ​ 38.05 ​ ​ ​ ​ ​ Exercised ​ (2,822,617) ​ 11.88 ​ ​ ​ ​ ​ Expired/Cancelled ​ (2,800,880) ​ 32.58 ​ ​ ​ ​ ​ Outstanding at December 31, 2021 ​ 12,520,865 $ 25.05 7.64 ​ $ 35,047 Ending vested and expected to vest at December 31, 2021 ​ 12,520,865 ​ $ 25.05 ​ 7.64 ​ $ 35,047 Options exercisable at December 31, 2021 6,466,673 ​ $ 16.67 6.40 ​ $ 34,112 ​ 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. ​ 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, 2021 and 2020 were $1.2 million and $61,000, respectively. During the year ended December 31, 2021, the Company received proceeds of $1.6 million for the issuance of 94,148 shares under the 2020 ESPP and there was $0.4 million of unrecognized compensation cost associated with the 2020 ESPP, which will be recognized over 5.33 months. As of December 31, 2020, no shares were issued under the 2020 ESPP and there was $0.5 million of unrecognized compensation cost associated with the 2020 ESPP, to be recognized over 6 months . ​ Restricted Stock Units ​ On June 1, 2016, the Company entered into an RSU agreement with the Company’s former Chief Executive Officer, pursuant to which the Company granted the former Chief Executive Officer 550,000 RSUs as an inducement of employment pursuant to the exception to The Nasdaq Global Market rules that generally require stockholder approval of equity incentive plans. These RSUs, which included certain performance vesting criteria based upon the satisfaction of certain clinical trial milestones were fully vested as of June 1, 2020. No RSUs related to this grant were outstanding at either December 31, 2021 or 2020. ​ In June 2021, under the terms of the 2018 Plan, the Company granted 1,253,540 RSUs to its executives and employees. The awards are time-based, and each award has one of two vesting conditions. For certain RSU awards, 100% of the RSUs will vest on the first anniversary of the grant date, and for others, 50% of the RSUs will vest on the first anniversary of the grant date with the remaining 50% vesting on December 31, 2022, assuming all time-based conditions are achieved. A summary of the RSU activity during the years ended December 31, 2021 and 2020 is presented in the following table: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Number ​ Average ​ ​ of ​ Grant Date ​ RSUs Fair Value Outstanding, non-vested as of December 31, 2020 ​ — ​ $ — Granted ​ 1,253,540 ​ ​ 23.87 Vested ​ — ​ ​ — Canceled/Forfeited ​ (143,530) ​ ​ 23.87 Outstanding, non-vested as of December 31, 2021 ​ 1,110,010 ​ $ 23.87 ​ As of December 31, 2021, there was $14.2 million of unrecognized stock-based compensation expense associated with unvested RSUs, which the Company expects to recognize over a remaining weighted-average period of 0.62 years. The aggregate intrinsic value of the unvested RSUs outstanding as of December 31, 2021 was $21.2 million. ​ Stock-Based Compensation Total stock-based compensation expense related to all of the Company’s stock-based awards was recorded on the Consolidated Statements of Operations as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2021 2020 2019 Research and development ​ $ 40,833 ​ $ 19,727 ​ $ 11,396 General and administrative ​ 28,932 ​ 21,160 ​ 12,881 Total stock-based compensation expense ​ $ 69,765 ​ $ 40,887 ​ $ 24,277 ​ Total stock-based compensation expense by type of award was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2021 2020 2019 Stock option expense ​ $ 56,305 ​ $ 40,714 ​ $ 23,964 Restricted stock unit expense ​ 12,247 ​ 112 ​ 313 ESPP expense ​ 1,213 ​ 61 ​ — Total stock-based compensation expense ​ $ 69,765 ​ $ 40,887 ​ $ 24,277 ​ As of December 31, 2021, there was $93.6 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, 2021, 2020, and 2019 was $22.28, $17.32, and $9.48 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, 2021 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, 2021. 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, 2021, 2020, and 2019 were $21.3 million, $21.4 million, and $5.3 million, respectively. The following table summarizes the assumptions relating to options granted pursuant to the Company’s equity incentive plans for the years ended December 31, 2021, 2020, and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock Option ​ ESPP ​ ​ Years Ended December 31, ​ Years Ended December 31, Assumptions: 2021 2020 2019 2021 2020 Expected term (years) ​ 4.94 - 5.28 5.18 - 6.19 6.14 - 6.06 ​ 0.50 0.50 Expected volatility ​ 70.35% - 69.99% - 71.62% - ​ 52.04% - 94.56% 54.90% Risk-free interest rate ​ 0.36% - 0.97% ​ 0.28% - 1.83% ​ 2.59% - 1.62% ​ 0.06% - 0.13% 0.09% Expected dividend yield ​ 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, 2021
EMPLOYEE BENEFIT PLAN
EMPLOYEE BENEFIT PLAN	NOTE 7. 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 $2.2 million, $1.2 million, and $0.9 million for the years ended December 31, 2021, 2020, and 2019, respectively.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2021
INCOME TAXES
INCOME TAXES	NOTE 8. INCOME TAXES The Company did not record a provision or benefit for income taxes for the years ended December 31, 2021, 2020 or 2019. The significant components of the Company’s net deferred tax assets and liabilities are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 2020 Deferred income tax assets: ​ ​ Net operating loss carryforwards ​ $ 203,298 ​ $ 144,087 Stock-based compensation ​ 18,319 ​ 11,364 Tax credit carryforwards ​ 40,851 ​ 32,508 Lease liabilities ​ ​ 14,970 ​ ​ 11,051 Depreciation and amortization ​ ​ 228 ​ ​ 250 Reserves and accruals ​ 4,445 ​ 1,866 Deferred tax assets before valuation allowance ​ 282,111 ​ 201,126 Less: valuation allowance ​ (267,469) ​ (189,412) Net deferred income tax assets ​ 14,642 ​ 11,714 Deferred tax liabilities: ​ ​ ​ ​ Depreciation and amortization ​ (14,642) ​ (11,714) Net deferred tax assets (liabilities) ​ $ — ​ $ — ​ The reconciliation of the effective income tax rate to the U.S. statutory rate is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended December 31, ​ 2021 2020 2019 Federal statutory tax rate 21 % 21 % 21 % Orphan drug and research credits 2 3 4 ​ Permanent and other differences — (1) (1) ​ State tax, net of federal benefit — — 2 ​ ​ 23 % 23 % 26 % Valuation allowance (23) % (23) % (26) % Effective tax rate — % — % — % ​ The Company had net operating loss carryforwards (“NOLs”) for federal and state income tax purposes of approximately $945.3 million and $149.6 million, respectively, as of December 31, 2021. $142.4 million of federal NOLs will expire beginning in 2027, while $803.0 million 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 2041. 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 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 believes that significant uncertainty exists with respect to future realization of the deferred tax assets and has therefore established a full valuation allowance. For the years ended December 31, 2021 and 2020, the change in the valuation allowance was approximately $78.1 million, $60.7 million, and $50.6 million, respectively. 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, 2021, 2020, and 2019 is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2021 2020 2019 Unrecognized benefit - beginning of period ​ $ 14,432 ​ $ 10,038 ​ $ 6,344 Gross decreases - prior period tax positions ​ (159) ​ — ​ — Gross increase current period tax positions ​ 3,898 ​ 4,394 ​ 3,694 Unrecognized benefit - end of period ​ $ 18,171 ​ $ 14,432 ​ $ 10,038 ​ No interest or penalties on unpaid tax were recorded during the years ended December 31, 2021, 2020, or 2019. 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.

LICENSES AND AGREEMENTS

LICENSES AND AGREEMENTS	12 Months Ended
	Dec. 31, 2021
LICENSES AND AGREEMENTS
LICENSES AND AGREEMENTS	NOTE 9. 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 that are designed to destroy metastatic melanoma cells. The CRADA was amended in January 2015, to include four new indications, including the development of TIL therapy for the treatment of patients with bladder, lung, triple-negative breast, and Human Papilloma Virus (“HPV”)-associated cancers. The CRADA was further amended in August 2016 to, among other things, (i) extend the term of the CRADA by another five years to August 2021, and (ii) 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. The CRADA was further amended in August 2021 to, among other things, extend the term of the CRADA by another 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 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, $2.0 million, and $2.2 million for the years ended December 31, 2021, 2020 and 2019, respectively, as research and development expenses. Patent License Agreement Related to the Development and Manufacture of TIL 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 (the “Amended and Restated Patent License Agreement”), which includes the grant of additional exclusive, worldwide patent rights in the Indications to cytokine-tethered TIL technology, and expands the non-exclusive, worldwide field of use to all cancers. The 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 Amended and Restated Patent License Agreement. The Company anticipates making milestone payments, including a payment in the low-single-digit millions of dollars in conjunction with the approval of a Biologics License Application for any of its product candidates covered by the Amended and Restated Patent License Agreement. The term of the 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. 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 license to the NIH’s rights to patent-pending technologies related to methods for improving adoptive cell therapy through more potent and efficient production of TIL from melanoma tumors by selecting for T cell populations that express various inhibitory receptors. Unless terminated sooner, the license shall remain in effect until the last licensed patent right expires. Under the Exclusive Patent License Agreement, the Company agreed to pay customary royalties based on a percentage of net sales of a licensed product (which percentage is in the mid-single digits), a percentage of revenues from sublicensing arrangements, and lump sum benchmark payments upon the successful completion of clinical studies involving licensed technologies, the receipt of the first FDA approval or foreign equivalent for a licensed product or process resulting from the licensed technologies, the first commercial sale of a licensed product or process in the U.S., and the first commercial sale of a licensed product or process in any foreign country. H. Lee Moffitt Cancer Center Research Collaboration and Clinical Grant Agreements with Moffitt In December 2016, the Company entered into a new three-year Sponsored Research Agreement with H. Lee Moffitt Cancer Center (“Moffitt”) which expired in December 2019. In June 2020, the Company entered into a new Sponsored Research Agreement with Moffitt, with a term that ends either upon completion of the research thereunder or on July 1, 2022, whichever is sooner, and under which immaterial payments will be made to Moffitt in connection with the research services thereunder. In December 2016, the Company entered into a clinical grant agreement with Moffitt to support an ongoing clinical trial at Moffitt that combines TIL 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 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. In the years ended December 31, 2021, 2020 and 2019, the Company recorded research and development costs of $0.4 million, $0.6 million, and $0.7 million, respectively, 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 world-wide license to Moffitt’s rights to patent-pending 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. 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 year ended December 31, 2021, 2020, and 2019. 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. In addition, 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 for the years ended December 31, 2021, 2020 and 2019 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. 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 antagonists 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. 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 $0.5 million, $1.1 million and $3.4 million associated with the SAA for the year ended December 31, 2021, 2020, and 2019 as research and development expenses, respectively. WuXi Advanced Therapies, Inc. In November 2016, the Company entered into a three-year manufacturing and services agreement (“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 our subsidiary Iovance Biotherapeutics Manufacturing LLC. Under the agreement, the Company entered into two statements of work for two cGMP manufacturing suites to be established and operated by WuXi for the Company, both of the suites are expected to be capable of being used for the commercial manufacture of its products. The terms of the related statements of work currently extend to February 2022 for the first statement of work and were extended to December 2022 for the second statement of work. The Company recorded costs associated with agreements with WuXi of $17.5 million, $20.6 million, and $28.4 million for the years ended December 31, 2021, 2020, and 2019 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 therapies that have been genetically edited. Financial terms of the license include 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 from Cellectis of $0.4 million the years ended December 31, 2021, and 2020 respectively. 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.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2021
LEASES
LEASES	NOTE 10. LEASES Operating Leases The Company leases corporate office space in California, including 49,918 square feet for its new corporate headquarters’ office space in San Carlos, California, manufacturing, research and development lab facilities and office space in Pennsylvania, including 136,000 square feet of commercial manufacturing and lab space in Philadelphia, Pennsylvania, and research and development lab facilities in Florida. The determination if an arrangement is a lease occurs at inception, and for leases with terms greater than 12 months , the Company records a related right-of-use asset and lease liability at the present value of lease payments over the term. Many leases include fixed rental escalation clauses, renewal options and/or termination options that are factored into the determination of lease payments when appropriate. The Company’s leases do not provide an implicit rate, and thus the Company estimated the incremental borrowing rate in calculating the present value of the lease payments. The Company’s leases have remaining lease terms of 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 an 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, 2021 December 31, 2020 Operating lease right-of-use assets $ 68,983 $ 54,756 Operating lease liabilities ​ ​ Current portion included in current liabilities ​ 5,057 ​ 6,284 Long-term portion included in non-current liabilities ​ 65,474 ​ 45,375 Total operating lease liabilities ​ $ 70,531 ​ $ 51,659 ​ 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, 2021 December 31, 2020 Operating lease cost ​ $ 15,341 ​ $ 8,728 ​ Variable lease cost ​ ​ 4,649 ​ 5,585 ​ Short-term lease cost ​ ​ 119 ​ 91 ​ Total lease cost ​ $ 20,109 ​ $ 14,404 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in Operating cashflows ​ $ 12,316 ​ $ 8,372 ​ Right-of-use assets obtained from entering new leases ​ $ 17,617 ​ $ 50,327 ​ Increase in right-of-use assets from lease modifications ​ $ 7,796 ​ $ 1,306 ​ Weighted-average remaining lease terms (years) ​ ​ 15.38 ​ ​ 16.76 ​ Weighted-average discount rates ​ ​ 7.3 % ​ 8.3 % ​ As of December 31, 2021, future payments associated with the Company's operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ Year Ending December 31, ​ leases leases Total 2022 ​ $ 5,401 ​ $ 4,093 ​ $ 9,494 2023 ​ 8,006 ​ — ​ 8,006 2024 ​ 8,206 ​ — ​ 8,206 2025 ​ 8,107 ​ — ​ 8,107 2026 ​ 7,979 ​ — ​ 7,979 Thereafter ​ 91,952 ​ — ​ 91,952 Total lease payments ​ $ 129,651 ​ $ 4,093 ​ $ 133,744 Less: Present value adjustment ​ (56,483) ​ (119) ​ (56,602) Future tenant improvement reimbursement ​ ​ (6,611) ​ ​ — ​ ​ (6,611) Operating lease liabilities ​ $ 66,557 ​ $ 3,974 ​ $ 70,531 ​ ​ For its new corporate headquarters’ office, the Company was provided a tenant improvement allowance of $8.2 million. As of December 31, 2021, the Company has received reimbursement associated with this tenant improvement allowance of $1.6 million.

LEGAL PROCEEDINGS

LEGAL PROCEEDINGS	12 Months Ended
	Dec. 31, 2021
LEGAL PROCEEDINGS
LEGAL PROCEEDINGS	NOTE 11. LEGAL PROCEEDINGS Derivative Lawsuit. its current directors, as defendants, in the Court of Chancery in the State of Delaware. The complaint alleges breach of fiduciary duty and a claim for unjust enrichment in connection with alleged excessive compensation of certain non-executive directors of the Company . The defendants intend to vigorously defend against the foregoing complaints. Based on the early stage of the litigation, it is not possible to estimate the amount or range of possible loss that might result from these matters. Solomon Capital, LLC. Solomon Capital, LLC, Solomon Capital 401(K) Trust, Solomon Sharbat and Shelhav Raff v. Lion Biotechnologies, Inc. 1-for-100 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 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 may 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, 2021
LONG-TERM NOTE PAYABLE
LONG-TERM NOTE PAYABLE	NOTE 12. 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, 2021, and therefore accounted for the Job Creation Loan as debt in accordance with ASC Topic 470, Debt ​

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES (Policies)	12 Months Ended
	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES
Cash, Cash Equivalents, Restricted Cash 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 and carries them at fair value. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive loss or income. Impairment losses related to credit losses (if any) are recorded as an allowance for credit losses with an offsetting entry to net loss. No impairment losses related to credit losses were recognized for the years ended December 31, 2021 and 2020. 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 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, currently $6.1 million in a segregated bank account in connection with three letters of credit, one for $5.45 million for the benefit of the landlord for 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, December 31, December 31, ​ ​ 2021 ​ 2020 ​ 2019 Cash and cash equivalents ​ $ 78,229 ​ $ 67,329 ​ $ 13,969 Restricted cash ​ 6,084 ​ 5,525 ​ 5,450 Total cash, cash equivalents and restricted cash ​ $ 84,313 ​ $ 72,854 ​ $ 19,419 ​
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 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, 2021, 2020, and 2019, the Company did not recognize any impairments for its property and equipment.
Loss per Share	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 shares 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, 2021, 2020, and 2019, 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, ​ 2021 2020 2019 Stock options ​ 12,520,865 12,615,638 9,494,712 Employee Stock Purchase Plan ​ 85,227 37,259 — Restricted stock units ​ 1,110,010 — 22,916 Series A Convertible Preferred Stock* ​ 97,000 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 3,581,119 ​ ​ 16,655,260 16,331,016 13,195,747 ​ *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.
Fair Value Measurements	Fair Value Measurements Under Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures 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 and long-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. The Company’s financial instruments consist of Level 1 and Level 2 assets. 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 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.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“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 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. All intercompany accounts and transactions have been eliminated. The U.S. dollar is the functional currency for all the Company's consolidated operations.
Leases	Leases The Company determines if an arrangement includes a lease at inception. Operating leases are included in its Consolidated Balance Sheets as Operating lease right-of-use assets and Operating lease liabilities as of December 31, 2021. 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 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 date or the date of adoption of Accounting Standards Update (“ASU”) No. 2016-02 and No. 2018-10 (together “Topic 842”). 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. The Company has elected not to apply the recognition requirements of Topic 842 for short-term leases. For lease agreements entered into after the adoption of Topic 842 that include lease and non-lease components, such components are generally accounted for separately.
Stock-Based Compensation	Stock-Based Compensation The Company periodically grants stock options to employees as compensation for services rendered. The Company accounts for all stock-based payment awards made to employees, including the employee stock purchase plans, 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. In accordance with ASU No. 2018-07, Compensation-Stock Compensation 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 life 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”) and restricted stock awards (“RSAs”) from time to time as part of its equity incentive plans. The Company measures the compensation cost with respect to RSUs and RSAs 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 and RSAs is based on the closing price of the Company’s common stock on the grant date.
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 estimates of 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 estimates of services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. The Company determines its estimates 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 study protocol. The Company’s estimates for clinical investigator costs and 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 study 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 study, 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 treatments 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 study treatment. The Company accrues for 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. Changes in these estimates that result in material changes to the Company’s accruals could materially affect its results of operations. The Company’s historical estimates have not been materially different from actual amounts recorded.
General and Administrative Expenses	General and Administrative Expenses General and administrative expenses consist primarily of salaries and other related costs, including stock-based compensation, for personnel in executive, finance, accounting, legal, investor relations, facilities, business development, marketing, commercial and human resources functions. Other significant costs include facility costs not otherwise included in research and development expenses, sublicense royalty expenses, legal fees relating to corporate matters, insurance, public company expenses relating to maintaining compliance with Nasdaq listing rules and Securities and Exchange Commission (“SEC”) requirements, investor relations costs, and fees for accounting and consulting services. General and administrative costs are expensed as incurred.
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 interest and penalties, accounting in interim periods, disclosure, and transition. The Company will classify as income tax expense any interest and penalties. The Company has no material uncertain tax positions for any of the reporting periods presented.
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, 2021, and 2020, respectively, the Company’s cash balances were in excess of insured limits maintained at the financial institutions.
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
Recently Issued and Adopted Accounting Standards	Recently Issued and Adopted Accounting Standards Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES (Tables)	12 Months Ended
	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES
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, December 31, December 31, ​ ​ 2021 ​ 2020 ​ 2019 Cash and cash equivalents ​ $ 78,229 ​ $ 67,329 ​ $ 13,969 Restricted cash ​ 6,084 ​ 5,525 ​ 5,450 Total cash, cash equivalents and restricted cash ​ $ 84,313 ​ $ 72,854 ​ $ 19,419
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, ​ 2021 2020 2019 Stock options ​ 12,520,865 12,615,638 9,494,712 Employee Stock Purchase Plan ​ 85,227 37,259 — Restricted stock units ​ 1,110,010 — 22,916 Series A Convertible Preferred Stock* ​ 97,000 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 3,581,119 ​ ​ 16,655,260 16,331,016 13,195,747 ​ *on an as-converted basis

CASH EQUIVALENTS AND INVESTME_2

CASH EQUIVALENTS AND INVESTMENTS (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 and December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2021 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 247,287 ​ $ — ​ $ (520) ​ $ 246,767 U.S. government agency securities ​ 5,104 ​ — ​ (7) ​ 5,097 Corporate securities ​ ​ 35,627 ​ ​ — ​ ​ (39) ​ ​ 35,588 Commercial paper ​ ​ 235,352 ​ ​ 10 ​ ​ (46) ​ ​ 235,316 Money market funds ​ ​ 56,250 ​ ​ — ​ ​ — ​ ​ 56,250 Total investments ​ $ 579,620 ​ $ 10 ​ $ (612) ​ $ 579,018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of December 31, 2020 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 470,108 ​ $ 30 ​ $ (29) ​ $ 470,109 U.S. government agency securities ​ 91,981 ​ 20 ​ (2) ​ 91,999 Money market funds ​ ​ 49,720 ​ ​ — ​ ​ — ​ ​ 49,720 Total ​ $ 611,809 ​ $ 50 ​ $ (31) ​ $ 611,828
Schedule of available-for-sale debt securities	The fair value of cash equivalents and investments as of December 31, 2021 and December 31, 2020 are classified as follows in the Company’s Consolidated Balance Sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, Classified as: ​ 2021 2020 Cash equivalents ​ $ 61,249 ​ $ 49,720 Short-term investments ​ ​ 426,181 ​ ​ 562,108 Long-term investments ​ ​ 91,588 ​ ​ — Total investments ​ $ 579,018 ​ $ 611,828
Schedule of available-for-sale debt securities by contractual maturity	The following table summarizes the Company’s available-for-sale investments by contractual maturity (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ Amortized Cost Fair Value Within one year ​ $ 487,718 ​ $ 487,430 One year to two years ​ ​ 91,902 ​ ​ 91,588 Total investments ​ $ 579,620 ​ $ 579,018
Schedule of fair value of the company's financial assets	As of December 31, 2021 and 2020, the fair value of the Company’s financial assets, which consist of cash equivalents and short-term and long-term investments classified as available-for-sale securities, were measured on a recurring basis were 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, 2021 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 246,767 ​ $ — ​ $ — ​ $ 246,767 U.S. government agency securities ​ — ​ 5,097 ​ — ​ 5,097 Corporate securities ​ ​ — ​ ​ 35,588 ​ ​ — ​ ​ 35,588 Commercial paper ​ ​ — ​ ​ 235,316 ​ ​ — ​ ​ 235,316 Money market funds ​ ​ 56,250 ​ ​ — ​ ​ — ​ ​ 56,250 Total ​ $ 303,017 ​ $ 276,001 ​ $ — ​ $ 579,018 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2020 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 470,109 ​ $ — ​ $ — ​ $ 470,109 U.S. government agency securities ​ 91,999 ​ — ​ — ​ 91,999 Money market funds ​ ​ 49,720 ​ ​ — ​ ​ — ​ ​ 49,720 Total ​ $ 611,828 ​ $ — ​ $ — ​ $ 611,828

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2021
PROPERTY AND EQUIPMENT, NET
Schedule of Property and equipment	Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ 2021 2020 Leasehold improvements ​ $ 57,817 ​ $ 2,573 Lab, process, and validation equipment ​ ​ 8,686 ​ ​ 4,656 Utility equipment ​ 4,179 ​ — Office furniture and equipment ​ 1,244 ​ 480 Computer software ​ ​ 1,163 ​ ​ — Computer equipment ​ 674 ​ 270 Machinery and equipment ​ ​ 82 ​ ​ — Construction in progress ​ 35,782 ​ 56,758 Total Property and equipment, cost ​ 109,627 ​ 64,737 Less: Accumulated depreciation and amortization ​ (8,689) ​ (5,578) Property and equipment, net ​ $ 100,938 ​ $ 59,159

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	12 Months Ended
	Dec. 31, 2021
ACCRUED EXPENSES
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ December 31, ​ ​ 2021 2020 Accrued payroll and employee related expenses ​ $ 21,513 ​ $ 9,032 Clinical related ​ ​ 18,167 ​ ​ 15,661 Manufacturing related ​ 6,566 ​ 3,266 Facilities related ​ ​ 4,857 ​ ​ 4,342 Legal and related services ​ 1,907 ​ 1,061 Other accrued expenses ​ 3,756 ​ 1,712 Total accrued expenses ​ $ 56,766 ​ $ 35,074

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2021
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 January 1, 2019 ​ 6,889,287 $ 10.25 ​ ​ ​ ​ ​ Issued ​ 4,166,600 ​ ​ 14.73 ​ ​ ​ ​ ​ Exercised ​ (727,492) ​ ​ 8.85 ​ ​ ​ ​ ​ Expired/Cancelled ​ (833,683) ​ ​ 13.87 ​ ​ ​ ​ ​ Outstanding at December 31, 2019 ​ 9,494,712 $ 12.00 ​ ​ ​ ​ ​ Issued ​ 4,981,001 ​ ​ 28.17 ​ ​ ​ ​ ​ Exercised ​ (973,854) ​ ​ 9.92 ​ ​ ​ ​ ​ Expired/Cancelled ​ (886,221) ​ ​ 18.67 ​ ​ ​ ​ ​ Outstanding at December 31, 2020 ​ 12,615,638 $ 18.08 ​ ​ ​ ​ ​ Issued ​ 5,528,724 ​ 38.05 ​ ​ ​ ​ ​ Exercised ​ (2,822,617) ​ 11.88 ​ ​ ​ ​ ​ Expired/Cancelled ​ (2,800,880) ​ 32.58 ​ ​ ​ ​ ​ Outstanding at December 31, 2021 ​ 12,520,865 $ 25.05 7.64 ​ $ 35,047 Ending vested and expected to vest at December 31, 2021 ​ 12,520,865 ​ $ 25.05 ​ 7.64 ​ $ 35,047 Options exercisable at December 31, 2021 6,466,673 ​ $ 16.67 6.40 ​ $ 34,112
Schedule of summary of RSU activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ Number ​ Average ​ ​ of ​ Grant Date ​ RSUs Fair Value Outstanding, non-vested as of December 31, 2020 ​ — ​ $ — Granted ​ 1,253,540 ​ ​ 23.87 Vested ​ — ​ ​ — Canceled/Forfeited ​ (143,530) ​ ​ 23.87 Outstanding, non-vested as of December 31, 2021 ​ 1,110,010 ​ $ 23.87
Schedule of stock-based compensation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2021 2020 2019 Research and development ​ $ 40,833 ​ $ 19,727 ​ $ 11,396 General and administrative ​ 28,932 ​ 21,160 ​ 12,881 Total stock-based compensation expense ​ $ 69,765 ​ $ 40,887 ​ $ 24,277
Schedule of compensation cost for share-based payment arrangements, allocation of share-based compensation costs by plan	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ ​ 2021 2020 2019 Stock option expense ​ $ 56,305 ​ $ 40,714 ​ $ 23,964 Restricted stock unit expense ​ 12,247 ​ 112 ​ 313 ESPP expense ​ 1,213 ​ 61 ​ — Total stock-based compensation expense ​ $ 69,765 ​ $ 40,887 ​ $ 24,277
Schedule of share-based payment award, stock options, valuation assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Stock Option ​ ESPP ​ ​ Years Ended December 31, ​ Years Ended December 31, Assumptions: 2021 2020 2019 2021 2020 Expected term (years) ​ 4.94 - 5.28 5.18 - 6.19 6.14 - 6.06 ​ 0.50 0.50 Expected volatility ​ 70.35% - 69.99% - 71.62% - ​ 52.04% - 94.56% 54.90% Risk-free interest rate ​ 0.36% - 0.97% ​ 0.28% - 1.83% ​ 2.59% - 1.62% ​ 0.06% - 0.13% 0.09% Expected dividend yield ​ 0% ​ 0% ​ 0% ​ 0% 0%

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2021
INCOME TAXES
Schedule of Deferred Tax Assets and Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, ​ 2021 2020 Deferred income tax assets: ​ ​ Net operating loss carryforwards ​ $ 203,298 ​ $ 144,087 Stock-based compensation ​ 18,319 ​ 11,364 Tax credit carryforwards ​ 40,851 ​ 32,508 Lease liabilities ​ ​ 14,970 ​ ​ 11,051 Depreciation and amortization ​ ​ 228 ​ ​ 250 Reserves and accruals ​ 4,445 ​ 1,866 Deferred tax assets before valuation allowance ​ 282,111 ​ 201,126 Less: valuation allowance ​ (267,469) ​ (189,412) Net deferred income tax assets ​ 14,642 ​ 11,714 Deferred tax liabilities: ​ ​ ​ ​ Depreciation and amortization ​ (14,642) ​ (11,714) Net deferred tax assets (liabilities) ​ $ — ​ $ —
Schedule of Effective Income Tax Rate Reconciliation	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years ended December 31, ​ 2021 2020 2019 Federal statutory tax rate 21 % 21 % 21 % Orphan drug and research credits 2 3 4 ​ Permanent and other differences — (1) (1) ​ State tax, net of federal benefit — — 2 ​ ​ 23 % 23 % 26 % Valuation allowance (23) % (23) % (26) % Effective tax rate — % — % — %
Schedule of Unrecognized Tax Benefits	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Years Ended December 31, ​ 2021 2020 2019 Unrecognized benefit - beginning of period ​ $ 14,432 ​ $ 10,038 ​ $ 6,344 Gross decreases - prior period tax positions ​ (159) ​ — ​ — Gross increase current period tax positions ​ 3,898 ​ 4,394 ​ 3,694 Unrecognized benefit - end of period ​ $ 18,171 ​ $ 14,432 ​ $ 10,038

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2021
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, 2021 December 31, 2020 Operating lease right-of-use assets $ 68,983 $ 54,756 Operating lease liabilities ​ ​ Current portion included in current liabilities ​ 5,057 ​ 6,284 Long-term portion included in non-current liabilities ​ 65,474 ​ 45,375 Total operating lease liabilities ​ $ 70,531 ​ $ 51,659
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, 2021 December 31, 2020 Operating lease cost ​ $ 15,341 ​ $ 8,728 ​ Variable lease cost ​ ​ 4,649 ​ 5,585 ​ Short-term lease cost ​ ​ 119 ​ 91 ​ Total lease cost ​ $ 20,109 ​ $ 14,404 ​ ​ ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in Operating cashflows ​ $ 12,316 ​ $ 8,372 ​ Right-of-use assets obtained from entering new leases ​ $ 17,617 ​ $ 50,327 ​ Increase in right-of-use assets from lease modifications ​ $ 7,796 ​ $ 1,306 ​ Weighted-average remaining lease terms (years) ​ ​ 15.38 ​ ​ 16.76 ​ Weighted-average discount rates ​ ​ 7.3 % ​ 8.3 % ​
Schedule of minimum lease commitments	As of December 31, 2021, future payments associated with the Company's operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ Year Ending December 31, ​ leases leases Total 2022 ​ $ 5,401 ​ $ 4,093 ​ $ 9,494 2023 ​ 8,006 ​ — ​ 8,006 2024 ​ 8,206 ​ — ​ 8,206 2025 ​ 8,107 ​ — ​ 8,107 2026 ​ 7,979 ​ — ​ 7,979 Thereafter ​ 91,952 ​ — ​ 91,952 Total lease payments ​ $ 129,651 ​ $ 4,093 ​ $ 133,744 Less: Present value adjustment ​ (56,483) ​ (119) ​ (56,602) Future tenant improvement reimbursement ​ ​ (6,611) ​ ​ — ​ ​ (6,611) Operating lease liabilities ​ $ 66,557 ​ $ 3,974 ​ $ 70,531

GENERAL ORGANIZATION AND BUSI_2

GENERAL ORGANIZATION AND BUSINESS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
GENERAL ORGANIZATION AND BUSINESS
Net loss	$ (342,252)	$ (259,581)	$ (197,556)
Net cash used in operating activities	(227,941)	(205,134)	(158,889)
Proceeds from the issuance of common stock, net	203,156	567,043
Cash equivalents, short-term investments, and restricted cash	602,100
Cash and cash equivalents	78,229	67,329	13,969
Short-term investments	426,181	562,108
Long-term investments	91,588
Restricted cash	$ 6,084	$ 5,525	$ 5,450

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Cash, Cash equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit for the benefit of the landlord for its commercial manufacturing facility	$ 5,450
Security deposit for the benefit of utilities service provider	100
Benefit of landlord	600
Letter of credit	1,000
Cash and cash equivalents	78,229	$ 67,329	$ 13,969
Restricted cash	6,084	5,525	5,450
Total cash, cash equivalents and restricted cash	84,313	$ 72,854	$ 19,419	$ 82,152
Minimum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit	$ 1,500

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Useful lives, impairment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 0	$ 0
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, Estimated Useful Lives	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	Lesser of the remaining economic life of the asset or the lease-term
Leasehold improvements
Property, Plant and Equipment, Estimated Useful Lives	Lesser of the remaining economic life of the asset or the lease-term

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Loss per share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive securities excluded from calculation of net loss per share	16,655,260	16,331,016	13,195,747
Stock option
Antidilutive securities excluded from calculation of net loss per share	12,520,865	12,615,638	9,494,712
Employee Stock Purchase Plan
Antidilutive securities excluded from calculation of net loss per share	85,227	37,259
Restricted stock units
Antidilutive securities excluded from calculation of net loss per share	1,110,010		22,916
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
Antidilutive securities excluded from calculation of net loss per share	2,842,158	3,581,119	3,581,119

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Concentrations, etc. (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)item	Dec. 31, 2020USD ($)
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES
Number Of Financial Institutions | item	4
Retained earnings | $	$ (1,172,445)	$ (830,193)

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES - Additional information (Details)	12 Months Ended
	Dec. 31, 2021segment
SUMMARY OF SIGNIFICANT ACCOUNTING PRACTICES
Number of operating segment	1

CASH EQUIVALENTS AND INVESTME_3

CASH EQUIVALENTS AND INVESTMENTS - Cost and fair value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost	$ 579,620	$ 611,809
Gross Unrealized Gains	10	50
Gross Unrealized Losses	(612)	(31)
Fair Value	579,018	611,828
U.S. treasury securities
Amortized Cost	247,287	470,108
Gross Unrealized Gains		30
Gross Unrealized Losses	(520)	(29)
Fair Value	246,767	470,109
U.S. government agency securities
Amortized Cost	5,104	91,981
Gross Unrealized Gains		20
Gross Unrealized Losses	(7)	(2)
Fair Value	5,097	91,999
Corporate securities
Amortized Cost	35,627
Gross Unrealized Losses	(39)
Fair Value	35,588
Commercial paper
Amortized Cost	235,352
Gross Unrealized Gains	10
Gross Unrealized Losses	(46)
Fair Value	235,316
Money market funds
Amortized Cost	56,250	49,720
Fair Value	$ 56,250	$ 49,720

CASH EQUIVALENTS AND INVESTME_4

CASH EQUIVALENTS AND INVESTMENTS - Available for sale debt securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CASH EQUIVALENTS AND INVESTMENTS
Cash equivalents	$ 61,249	$ 49,720
Short-term investments	426,181	562,108
Long-term investments	91,588
Investments total	$ 579,018	$ 611,828

CASH EQUIVALENTS AND INVESTME_5

CASH EQUIVALENTS AND INVESTMENTS - Narrative (Details) - USD ($) $ in Thousands	24 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Unrealized losses on available-for-sale	$ 0
Demand Deposits
Cash equivalents total	$ 17,000	$ 17,600

CASH EQUIVALENTS AND INVESTME_6

CASH EQUIVALENTS AND INVESTMENTS - Contractual maturity (Details) $ in Thousands	Dec. 31, 2021USD ($)
Amortized Cost
Within one year	$ 487,718
One year to two years	91,902
Amortized cost investments total	579,620
Fair Value
Within one year	487,430
One year to two years	91,588
Total investments	$ 579,018

CASH EQUIVALENTS AND INVESTME_7

CASH EQUIVALENTS AND INVESTMENTS - Fair value of company's financial assets (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Total	$ 579,018	$ 611,828
U.S. treasury securities
Total	246,767	470,109
U.S. government agency securities
Total	5,097	91,999
Corporate securities
Total	35,588
Commercial paper
Total	235,316
Money market funds
Total	56,250	49,720
Level 1
Total	303,017	611,828
Level 1 | U.S. treasury securities
Total	246,767	470,109
Level 1 | U.S. government agency securities
Total		91,999
Level 1 | Money market funds
Total	56,250	$ 49,720
Level 2
Total	276,001
Level 2 | U.S. government agency securities
Total	5,097
Level 2 | Corporate securities
Total	35,588
Level 2 | Commercial paper
Total	$ 235,316

PROPERTY AND EQUIPMENT, NET - (

PROPERTY AND EQUIPMENT, NET - (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	$ 109,627	$ 64,737
Less: Accumulated depreciation and amortization	(8,689)	(5,578)
Property and equipment, net	100,938	59,159
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	57,817	2,573
Lab, process, and validation equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	8,686	4,656
Utility equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	4,179
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	1,244	480
Computer software
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	1,163
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	674	270
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	82
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, cost	$ 35,782	$ 56,758

PROPERTY AND EQUIPMENT, NET - O

PROPERTY AND EQUIPMENT, NET - Other information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation	$ 3.1	$ 1.1	$ 1.2
Commercial Manufacturing Facility Agreement
Property, Plant and Equipment [Line Items]
Depreciation	1.6
Fixed asset additions	$ 62.4

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
ACCRUED EXPENSES
Accrued payroll and employee related expenses	$ 21,513	$ 9,032
Clinical related	18,167	15,661
Manufacturing related	6,566	3,266
Facilities related	4,857	4,342
Legal and related services	1,907	1,061
Accrued other	3,756	1,712
Total accrued expenses	$ 56,766	$ 35,074

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 08, 2021	Jun. 01, 2016	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 12, 2022	Jan. 11, 2022	Sep. 22, 2021	Jun. 08, 2020	Jun. 07, 2020	Apr. 22, 2018
Common Stock
Common stock, shares authorized					300,000,000	300,000,000
Common stock, par or stated value per share					$ 0.000041666	$ 0.000041666
Common stock, shares issued					157,004,742	146,874,917
Common stock, shares outstanding					157,004,742	147,874,917
Proceeds from the issuance of common stock, net					$ 203,156	$ 567,043
Intrinsic value of options exercised					21,300	21,400	$ 5,300
Share-based Compensation					$ 69,765	$ 40,887	$ 24,277
Common Stock
Common Stock
Common stock issued, net of offering costs (in shares)					6,474,099	19,475,806
IPO
Common Stock
Common stock issued, net of offering costs (in shares)				16,935,484
Share price (in dollars per share)				$ 31
Proceeds from the issuance of common stock, net				$ 567,000
IPO | Underwriter
Common Stock
Common stock issued, net of offering costs (in shares)				2,540,322
Proceeds from the issuance of common stock				$ 603,700
At the Market Offering Program
Common Stock
Common stock issued, net of offering costs (in shares)					6,474,099
Proceeds from the issuance of common stock, net					$ 203,200
Maximum amount of shares to be issued	$ 350,000
Maximum percentage of commission	3.00%
Weighted average price					$ 32.12
Series A Convertible Preferred Stock.
Common Stock
Preferred stock, shares authorized					17,000
Preferred stock, shares outstanding					194	194
Conversion of stock, shares issued					500
Conversion of Stock, shares converted					0	0
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 shares					$ 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
Convertible price per shares					$ 4.75
Preferred stock, shares outstanding					2,842,158	3,581,119
Series B Convertible Preferred Stock | Issuance Of Common Stock Upon Conversion Of Preferred Stock
Common Stock
Conversion of stock, shares issued					738,961	0
Series B Convertible Preferred Stock | Common Stock
Common Stock
Preferred stock, shares outstanding					2,842,158	3,581,119
Series B Convertible Preferred Stock | IPO
Common Stock
Preferred stock, shares authorized					11,500,000
Convertible price per shares					$ 4.75
Blank check
Common Stock
Preferred stock, shares authorized					50,000,000
Stock option
Common Stock
Total unrecognized compensation expense					$ 93,600
Unrecognized compensation cost recognition period					1 year 10 months 3 days
Weighted average grant date fair value, options granted					$ 22.28	$ 17.32	$ 9.48
Restricted stock units
Common Stock
Unrecognized compensation cost recognition period					7 months 13 days
Granted			1,253,540		1,253,540
Granted fair value (in per share)					$ 23.87
Unrecognized compensation cost					$ 14,200
Aggregate intrinsic value of outstanding nonvested RSUs					$ 21,200
Restricted stock units | Chief Executive Officer
Common Stock
Granted		550,000
2014 Equity Incentive Plan
Common Stock
Number of shares available					60,785
The 2018 Plan
Common Stock
Shares authorized											14,000,000	6,000,000	6,000,000
Number of shares available					3,866,948
2020 ESPP
Common Stock
Shares authorized					500,000
Percentage of purchase price					85.00%
Unrecognized compensation cost					$ 400	$ 500
Unrecognized compensation cost recognition period					5 months 10 days	6 months
Proceeds from Issuance or Sale of Equity					$ 1,600
Common Stock, Capital Shares Reserved for Future Issuance					94,148	0
Stock-based compensation expense					$ 1,200
2021 Inducement Plan
Common Stock
Shares authorized										1,000,000
Number of shares available					723,525
2021 Inducement Plan | Subsequent Event
Common Stock
Shares authorized								1,750,000	1,000,000

STOCKHOLDERS' EQUITY - Stock Op

STOCKHOLDERS' EQUITY - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Remaining Contractual Life
Ending vested and expected to vest, remaining term	7 years 7 months 20 days
Aggregate Intrinsic Value
Ending vested and expected to vest	$ 35,047
Stock option
Number of Options
Outstanding, beginning balance	12,615,638	9,494,712	6,889,287
Granted	5,528,724	4,981,001	4,166,600
Exercised	(2,822,617)	(973,854)	(727,492)
Expired/Forfeited	(2,800,880)	(886,221)	(833,683)
Outstanding, ending balance	12,520,865	12,615,638	9,494,712
Ending vested and expected to vest	12,520,865
Options exercisable	6,466,673
Weighted Average Exercise Price
Outstanding, beginning balance	$ 18.08	$ 12	$ 10.25
Granted	38.05	28.17	14.73
Exercised	11.88	9.92	8.85
Expired/Forfeited	32.58	18.67	13.87
Outstanding, ending balance	25.05	$ 18.08	$ 12
Ending vested and expected to vest	25.05
Options exercisable	$ 16.67
Weighted Average Remaining Contractual Life
Options outstanding, remaining term	7 years 7 months 20 days
Options exercisable, remaining term	6 years 4 months 24 days
Aggregate Intrinsic Value
Option at ending balance	$ 35,047
Option exercisable	$ 34,112

STOCKHOLDERS' EQUITY - Restrict

STOCKHOLDERS' EQUITY - Restricted stock unit (Details) - Restricted stock units - $ / shares	1 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021
Number of Shares
Granted	1,253,540	1,253,540
Canceled/forfeited		(143,530)
Non-vested shares, Ending balance		1,110,010
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Granted		$ 23.87
Weighted Average Grant Date Fair Value, Canceled/forfeited		23.87
Weighted Average Grant Date Fair Value, Ending Balance		$ 23.87

STOCKHOLDERS' EQUITY - Stock ba

STOCKHOLDERS' EQUITY - Stock based expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total stock-based compensation expenses	$ 69,765	$ 40,887	$ 24,277
Research and development
Total stock-based compensation expenses	40,833	19,727	11,396
General and administrative
Total stock-based compensation expenses	$ 28,932	$ 21,160	$ 12,881

STOCKHOLDERS' EQUITY - Stock-ba

STOCKHOLDERS' EQUITY - Stock-based compensation by instrument (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total stock-based compensation expenses	$ 69,765	$ 40,887	$ 24,277
Stock option
Total stock-based compensation expenses	56,305	40,714	23,964
Restricted stock units
Total stock-based compensation expenses	12,247	112	$ 313
2020 ESPP
Total stock-based compensation expenses	$ 1,213	$ 61

STOCKHOLDERS' EQUITY - Assumpti

STOCKHOLDERS' EQUITY - Assumptions (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock option
Expected dividend yield	0.00%	0.00%	0.00%
Stock option | Minimum
Expected term (years)	4 years 11 months 8 days	5 years 2 months 4 days	6 years 1 month 20 days
Expected volatility	70.35%	69.99%	71.62%
Risk-free interest rate	0.36%	0.28%	2.59%
Stock option | Maximum
Expected term (years)	5 years 3 months 10 days	6 years 2 months 8 days	6 years 21 days
Expected volatility	73.88%	70.99%	70.63%
Risk-free interest rate	0.97%	1.83%	1.62%
2020 ESPP
Expected term (years)	6 months	6 months
Expected volatility		54.90%
Risk-free interest rate		0.09%
Expected dividend yield	0.00%
2020 ESPP | Minimum
Expected volatility	52.04%
Risk-free interest rate	0.06%
2020 ESPP | Maximum
Expected volatility	94.56%
Risk-free interest rate	0.13%

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
EMPLOYEE BENEFIT PLAN
Defined Contribution Plan, Cost	$ 2.2	$ 1.2	$ 0.9

INCOME TAXES - Net deferred tax

INCOME TAXES - Net deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred income tax asset:
Net operating loss carry forward	$ 203,298	$ 144,087
Stock-based compensation	18,319	11,364
Tax credit carryforwards	40,851	32,508
Lease liabilities	14,970	11,051
Depreciation and Amortization	228	250
Reserves and accruals	4,445	1,866
Deferred tax assets before valuation allowance	282,111	201,126
Less: valuation allowance	(267,469)	(189,412)
Net deferred income tax assets	14,642	11,714
Deferred tax liabilities:
Depreciation and amortization	(14,642)	(11,714)
Net deferred tax assets (liabilities)	$ 0	$ 0

INCOME TAXES - Reconciliation o

INCOME TAXES - Reconciliation of the effective income tax rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
INCOME TAXES
Federal statutory tax rate	21.00%	21.00%	21.00%
Orphan Drug & Research credits	2.00%	3.00%	4.00%
Permanent and other differences		(1.00%)	(1.00%)
State tax, net of federal benefit			2.00%
Effective Income Tax Rate Reconciliation Expected Rate Total	23.00%	23.00%	26.00%
Valuation allowance	(23.00%)	(23.00%)	(26.00%)

INCOME TAXES - Other informatio

INCOME TAXES - Other information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Operating loss carryovers definite to be expired	$ 142,400
Operating loss carryovers indefinite	803,000
Change in valuation allowance	78,100	$ 60,700	$ 50,600
Interest or penalties on unpaid tax	0	$ 0	$ 0
Federal income tax
Income Tax Contingency [Line Items]
Net operating loss carryovers (NOLs)	945,300
State income tax
Income Tax Contingency [Line Items]
Net operating loss carryovers (NOLs)	$ 149,600

INCOME TAXES - Unrecognized ben

INCOME TAXES - Unrecognized benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
INCOME TAXES
Unrecognized benefit-beginning of period	$ 14,432	$ 10,038	$ 6,344
Gross decreases-prior period tax positions	(159)	0	0
Gross increases-current period tax positions	3,898	4,394	3,694
Unrecognized benefit-end of period	$ 18,171	$ 14,432	$ 10,038

LICENSES AND AGREEMENTS (Detail

LICENSES AND AGREEMENTS (Details) $ in Thousands

May 07, 2018USD ($)

Jun. 28, 2014USD ($)

Apr. 30, 2017USD ($)

Dec. 31, 2016

Nov. 30, 2016item

Aug. 31, 2016USD ($)

Aug. 31, 2011item

Dec. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2021USD ($)

Dec. 31, 2021USD ($)

Research and development expenses

$ 259,039

$ 201,727

$ 166,023

Strategic Alliance Agreement

Research and development expenses

500

1,100

3,400

Research Collaboration And Clinical Grant Agreement

Research and development expenses

400

600

700

Maximum | Strategic Alliance Agreement

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

$ 14,200

Cooperative Research and Development Agreement

Agreement term

5 years

5 years

Research and development expenses

$ 500

2,000

2,000

2,200

Number Of Indications Under Agreement | item

4

Notification Period To Terminate Agreement

60 days

Research Collaboration And Clinical Grant Agreements With Moffitt

Agreement term

3 years

Moffitt License Agreement One

Agreement term

20 years

Research and development expenses

$ 0

Payments for upfront licensing fee

$ 100

Moffitt License Agreement Two

Research and development expenses

100

100

100

Payments for upfront licensing fee

$ 100

Additional milestone payable

400

$ 400

$ 400

Moffitt License Agreement Two, Amended and Restated

Payments for upfront licensing fee

200

WuXi Apptech, Inc - Manufacturing and Services Agreement

Agreement term

3 years

Research and development expenses

$ 17,500

20,600

$ 28,400

Number Of Statements Of Work | item

2

Number Of Suites Under The Agreement | item

2

Cellectis S.A

Research and development expenses

$ 400

Novartis Pharma AG - License Agreement

Research and development expenses

$ 10,000

LEASES - Additional information

LEASES - Additional information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)ft²	Dec. 31, 2020USD ($)
Option to extend	options to renew with renewal terms that can extend
Monthly lease payments	$ 133,744
First year	9,494
Second year	8,006
Monthly lease payments	12,316	$ 8,372
Operating lease liabilities	70,531	51,659
Operating lease right-of-use assets	68,983	$ 54,756
Tenant improvement allowance	$ 8,200
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
Facility leases
Monthly lease payments	$ 129,651
First year	5,401
Second year	8,006
Operating lease liabilities	$ 66,557
New Headquarters Lease | Office Space | San Carlos, California
Area of land | ft²	49,918
Tenant improvement allowance reimbursed	$ 1,600

LEASES - Company's right-of-use

LEASES - Company's right-of-use asset and lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
LEASES
Operating lease right-of-use assets	$ 68,983	$ 54,756
Operating lease liabilities
Current portion included in current liabilities	5,057	6,284
Long-term portion included in non-current liabilities	65,474	45,375
Total operating lease liabilities	$ 70,531	$ 51,659

LEASES - Components of lease ex

LEASES - Components of lease expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
LEASES
Operating lease cost	$ 15,341	$ 8,728
Variable lease cost	4,649	5,585
Short-term lease cost	119	91
Total lease cost	20,109	14,404
Cash paid for amounts included in the measurement of lease liabilities included in operating cashflows	12,316	8,372
Right-of-use assets obtained from entering new leases	17,617	50,327
Increase in right-of-use assets from lease modifications	$ 7,796	$ 1,306
Weighted-average remaining lease terms (years)	15 years 4 months 17 days	16 years 9 months 3 days
Weighted-average discount rates	7.30%	8.30%

LEASES - Maturities of the Comp

LEASES - Maturities of the Company's operating lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
2022	$ 9,494
2023	8,006
2024	8,206
2025	8,107
2025	7,979
Thereafter	91,952
Total lease payments	133,744
Less: Present value adjustment	(56,602)
Future tenant improvement reimbursement	(6,611)
Operating lease liabilities	70,531	$ 51,659
Facility leases
2022	5,401
2023	8,006
2024	8,206
2025	8,107
2025	7,979
Thereafter	91,952
Total lease payments	129,651
Less: Present value adjustment	(56,483)
Future tenant improvement reimbursement	(6,611)
Operating lease liabilities	66,557
CMO embedded leases
2022	4,093
Total lease payments	4,093
Less: Present value adjustment	(119)
Operating lease liabilities	$ 3,974

LEGAL PROCEEDINGS (Details)

LEGAL PROCEEDINGS (Details)	May 12, 2020USD ($)	Jun. 03, 2016USD ($)	Apr. 08, 2016USD ($)	Mar. 31, 2013	Nov. 30, 2011USD ($)	Jun. 30, 2011USD ($)
Damages claimed		$ 500,000
Equity claim	$ 47,420
Solomon Capital LLC Litigation
Proceeds from related party debt					$ 200,000	$ 100,000
Debt instrument, convertible, number of equity instruments			1,110
Reverse split ratio				0.01
Minimum
Estimate of possible loss			$ 1,500,000
Commercial paper | Solomon Capital LLC Litigation
Face amount			$ 200,000

LONG-TERM NOTE PAYABLE (Details

LONG-TERM NOTE PAYABLE (Details) - Job Creation Loan	Jan. 26, 2021USD ($)
Debt Instrument [Line Items]
Principal amount	$ 1,000,000
Loan term	5 years
Interest rate (as percent)	0.00%
Lender amount	$ 2,000
Average salary	$ 80,000
Average number of term	5 years