Iovance Biotherapeutics (IOVA) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 26, 2021
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
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	999 Skyway Road, Suite 150
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, par value $0.000041666 per value
Trading Symbol	IOVA
Security Exchange Name	NASDAQ
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		152,849,282
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001425205
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Current Assets
Cash and cash equivalents	$ 131,954	$ 67,329
Short-term investments	472,203	562,108
Short-term investments	461,976	562,108
Prepaid expenses and other assets	11,288	6,663
Total Current Assets	605,218	636,100
Property and equipment, net	72,750	59,159
Operating lease right-of-use assets	55,131	54,756
Long-term investments	10,227
Restricted cash	6,084	5,525
Long-term assets	1,163	12,918
Total Assets	750,573	768,458
Current Liabilities
Accounts payable	13,369	13,513
Accrued expenses	35,774	35,074
Operating lease liabilities - current	5,916	6,284
Total Current Liabilities	55,059	54,871
Non-Current Liabilities
Operating lease liabilities - noncurrent	47,083	45,375
Long-term note payable	1,000
Other liabilities		11,714
Total Non-Current Liabilities	48,083	57,089
Total Liabilities	103,142	111,960
Commitments and contingencies
Stockholders' Equity
Common stock, $0.000041666 par value; 300,000,000 shares authorized, 149,315,299 and 146,874,917 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	6	6
Accumulated other comprehensive income	96	19
Additional paid-in capital	1,552,968	1,486,662
Accumulated deficit	(905,642)	(830,193)
Total Stockholders' Equity	647,431	656,498
Total Liabilities and Stockholders' Equity	750,573	768,458
Series B Convertible Preferred Stock
Stockholders' Equity
Preferred stock, Value	3	4
Total Stockholders' Equity	$ 3	$ 4

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 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	149,315,299	146,874,917
Common Stock, Shares, Outstanding	149,315,299	146,874,917
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

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Costs and expenses
Research and development expenses	$ 55,949	$ 56,952
General and administrative expenses	19,621	13,858
Total costs and expenses	75,570	70,810
Loss from operations	(75,570)	(70,810)
Other income
Interest income, net	121	1,215
Net Loss	$ (75,449)	$ (69,595)
Net Loss Per Share of Common Stock, Basic and Diluted	$ (0.51)	$ (0.55)
Weighted Average Shares of Common Stock Outstanding, Basic and Diluted	147,370	126,568

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Consolidated Statements of Comprehensive Loss
Net Loss	$ (75,449)	$ (69,595)
Other comprehensive loss:
Unrealized gain on short-term investments	77	692
Comprehensive Loss	$ (75,372)	$ (68,903)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated other Comprehensive Income	Accumulated Deficit	Total
Beginning Balance at Dec. 31, 2019		$ 4	$ 5	$ 869,354	$ 220	$ (570,612)	$ 298,971
Beginning Balance (in Shares) at Dec. 31, 2019	194	3,581,119	126,411,808
Stock-based compensation expense				9,412			9,412
Vesting of restricted shares issued for services (in shares)			7,273
Tax payments related to shares withheld for vested restricted stock units				(118)			(118)
Common stock issued upon exercise of stock options				3,951			3,951
Common stock issued upon exercise of stock options (in shares)			404,075
Unrealized gain on short-term investments					692		692
Net loss						(69,595)	(69,595)
Ending Balance at Mar. 31, 2020		$ 4	$ 5	882,599	912	(640,207)	243,313
Ending Balance (in Shares) at Mar. 31, 2020	194	3,581,119	126,823,156
Beginning Balance at Dec. 31, 2020		$ 4	$ 6	1,486,662	19	(830,193)	656,498
Beginning Balance (in Shares) at Dec. 31, 2020	194	3,581,119	146,874,917
Stock-based compensation expense				16,941			16,941
Common stock issued upon exercise of stock options				6,479			$ 6,479
Common stock issued upon exercise of stock options (in shares)			423,178				423,178
Common stock sold in public offering, net of offering costs				42,885			$ 42,885
Common stock sold in public offering, net of offering costs (in shares)			1,278,243
Common stock issued from preferred stock conversion		$ (1)		1
Common stock issued from preferred stock conversion (in Shares)		(738,961)	738,961
Unrealized gain on short-term investments					77		77
Net loss						(75,449)	(75,449)
Ending Balance at Mar. 31, 2021		$ 3	$ 6	$ 1,552,968	$ 96	$ (905,642)	$ 647,431
Ending Balance (in Shares) at Mar. 31, 2021	194	2,842,158	149,315,299

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities
Net loss	$ (75,449)	$ (69,595)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	16,941	9,412
Noncash lease expense	2,285	1,870
Accretion (amortization) of discounts and premiums on investments	2,066	(50)
Depreciation and amortization	372	252
Changes in assets and liabilities:
Prepaid expenses, other assets, and long-term assets	7,130	(1,316)
Right-of-use assets	(2,660)
Operating lease liabilities	1,340	(2,461)
Accounts payable	(15)	(7,768)
Accrued expenses and other liabilities	(14,401)	4,364
Net cash used in operating activities	(62,391)	(65,292)
Cash Flows from Investing Activities
Maturities of investments	158,286	113,665
Purchase of investments	(70,370)	(12,923)
Purchase of property and equipment	(10,705)	(637)
Net cash provided by investing activities	77,211	100,105
Cash Flows from Financing Activities
Tax payments related to shares withheld for vested restricted stock units		(118)
Proceeds from the issuance of common stock upon exercise of options	6,479	3,951
Proceeds from the issuance of common stock, net	42,885
Proceeds from the issuance of debt	1,000
Net cash provided by financing activities	50,364	3,833
Net increase (decrease) in cash, cash equivalents, and restricted cash	65,184	38,646
Cash, Cash Equivalents, and Restricted Cash, Beginning of Period	72,854	19,419
Cash, Cash Equivalents, and Restricted Cash, End of Period	138,038	58,065
Supplemental disclosure of non-cash investing and financing activities:
Net unrealized (loss) gain on short-term investments	77	692
Acquisitions of property and equipment included in accounts payable and accrued expense	(3,258)	$ (4,686)
Conversion of convertible preferred stock to common stock	$ (1)

GENERAL ORGANIZATION AND BUSINE

GENERAL ORGANIZATION AND BUSINESS	3 Months Ended
	Mar. 31, 2021
GENERAL ORGANIZATION AND BUSINESS
GENERAL ORGANIZATION AND BUSINESS	NOTE 1. GENERAL ORGANIZATION AND BUSINESS Iovance Biotherapeutics, Inc. (the “Company”, “we”, “us” or “our”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of cell therapies as novel cancer immunotherapy products designed to harness the power of a patient’s own immune system to eradicate cancer cells. 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. The Company has developed a new, shorter manufacturing process for TIL therapy known as Generation 2 (“Gen 2”), which yields a cryopreserved TIL product. This proprietary and scalable manufacturing method is being further investigated in multiple indications. The Company’s lead product candidates include lifileucel for metastatic melanoma and metastatic cervical cancer. Lifileucel for metastatic cervical cancer was formerly known as LN-145. In addition to metastatic melanoma and metastatic cervical cancer, the Company is investigating the effectiveness and safety of TIL therapy and peripheral blood lymphocyte therapy for the treatment of squamous cell carcinoma of the head and neck, non-small cell lung cancer, and chronic lymphocytic leukemia through its sponsored trials, as well as in other oncology indications through collaborations. On June 1, 2017, the Company reincorporated from a Nevada corporation to a Delaware corporation. Basis of Presentation of Unaudited Condensed Consolidated Financial Information The unaudited condensed consolidated financial statements of the Company for the three months ended March 31, 2021 and 2020 have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for audited financial statements. However, such information reflects all adjustments (consisting solely of normal recurring adjustments), which are, in the opinion of management, necessary for the fair presentation of the Company's financial position and results of operations. Results shown for interim periods are not necessarily indicative of the results to be obtained for a full fiscal year. The balance sheet information as of December 31, 2020, was derived from the audited financial statements included in the Company's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 25, 2021. These interim financial statements should be read in conjunction with that report. 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. The Company currently does not 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 $75.4 million for the three months ended March 31, 2021 and used $62.4 million of cash in its operating activities during the three months ended March 31, 2021. For the three months ended March 31, 2021, the Company received net proceeds of approximately $42.9 million from the “at the market” offering program the Company has in place with Jefferies LLC, acting as sales agent. As of March 31, 2021, the Company had $610.2 million in cash, cash equivalents, investments, and restricted cash ($131.9 million of cash and cash equivalents, $462.0 million in short-term investments, $10.2 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 continue the construction of the tenant improvements for its new manufacturing facility, which will increase the amount of cash used during 2021 and beyond. Specifically, the Company expects continued spending on its current and planned clinical trials, continued expansion of manufacturing activities, including construction of a manufacturing facility, 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. Impact of COVID-19 In December 2019, a novel coronavirus known as SARS-CoV-2 was first detected in Wuhan, Hubei Province, People’s Republic of China, causing outbreaks of the coronavirus disease, known as COVID-19, that has now spread globally. On January 30, 2020, the World Health Organization (“WHO”) declared COVID-19 a pandemic (the “COVID-19 Pandemic”). The Secretary of Health and Human Services declared a public health emergency on January 31, 2020, under section 319 of the Public Health Service Act (42 U.S.C. 247d), in response to the COVID-19 Pandemic. The full impact of the COVID-19 Pandemic is unknown and rapidly evolving. While the potential economic impact brought by and over the duration of the COVID-19 Pandemic may be difficult to assess or predict, the COVID-19 Pandemic has resulted in significant disruption of global financial markets, which could in the future negatively affect the Company's liquidity. In addition, a recession or market volatility resulting from the COVID-19 Pandemic could affect the Company’s business. Given the nature and type of the Company’s short-term investments in U.S. government securities, the Company does not believe the COVID-19 Pandemic has had or will have a material impact on the Company's current investment liquidity. Concentrations of Risk The Company is subject to credit risk from its portfolio of 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 goals of its investment policy, in order of priority, are as follows: safety and preservation of principal, liquidity of investments sufficient to meet cash flow requirements of its business, and maximization of total return while maintaining safety and liquidity.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES 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” and are presented at fair value as either a current or non-current asset based on the length of maturity from the reporting date. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive income. Any impairment losses related to credit losses (if any) are included in an allowance for credit losses with an offsetting entry to net loss. No impairment losses related to credit losses were recognized for the three months ended March 31, 2021 or March 31, 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 net interest income in the Condensed Consolidated Statements of Operations. Gains and losses on securities sold are recorded based on the specific identification method and are included in net interest income in the Condensed Consolidated Statements of Operations. The Company has not incurred any realized gains or losses from sales of securities to date. The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, obligations issued by the U.S. government and U.S. government agencies as well as corporate debt securities and commercial papers, 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 $5,450,000 million for the benefit of the landlord for its commercial manufacturing facility used as a security deposit for the lease (See Note 10 - Leases), the second one for $74,685 for the benefit of a utilities service provider, and the third one for $559,082 for the benefit of the landlord for its new headquarters lease. The total amount is classified as Restricted Cash on the Condensed Consolidated Balance Sheet. The first letter of credit originally expired on May 28, 2020, however, it automatically extends for additional one-year periods, without written agreement, to May 28 in each succeeding calendar year, through at least 60 days after the lease expiration date. Further, on the expiration of the seventh year of the lease, and each anniversary date thereafter, the letter of credit may be decreased by $1,000,000, with a minimum security deposit of $1,450,000 maintained through the end of the lease term. The second letter of credit of $74,685 expired on March 9, 2021, however, it automatically extends, without written agreement, to the expiration date of December 1, 2022. The third letter of credit of $559,082 expires on February 1, 2032, however, it will be automatically extended, without written agreement, for one year periods to February in each succeeding calendar year. As of March 31, 2021 and December 31, 2020, restricted cash consisted of $6.1 million and $5.5 million, respectively. This amount has been classified as a non-current asset on the Company’s Condensed Consolidated Balance Sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash, reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 131,954 ​ $ 52,540 Restricted cash (included in non-current assets on the condensed consolidated balance sheets) ​ 6,084 ​ 5,525 Total cash, cash equivalents and restricted cash ​ $ 138,038 ​ $ 58,065 ​ Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock 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 shares of common stock issuable upon (i) the exercise of outstanding stock options and warrants, (ii) purchases though the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), (iii) vesting of restricted stock units and restricted stock awards, and (iv) conversion of preferred stock, are only included in the calculation of diluted net loss per share when their effect is dilutive. As of March 31, 2021 and 2020, the following outstanding common stock equivalents have been excluded from the calculation of net loss per share because their impact would be anti-dilutive. ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ 2021 2020 Stock options ​ 15,419,226 12,136,899 Series A Convertible Preferred Stock* ​ 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 2020 ESPP ​ 55,963 ​ — Restricted stock units ​ — 11,458 ​ ​ 18,414,347 15,826,476 ​ * on an as-converted basis The effect of potentially dilutive securities would be reflected in diluted earnings per share of common stock 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 ASC 820, Fair Value Measurements and Disclosures, fair value is defined as the price at which an asset could be exchanged, or a liability transferred in a transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or parameters are not available, valuation models are applied. Assets and liabilities recorded at fair value in the Company’s financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities, are as follows: Level 1–These are investments where values are based on unadjusted quoted prices for identical assets in an active market that the Company has the ability to access. Level 2–These are investments where values are based on quoted market prices in markets that are not active or model derived valuations in which all significant inputs are observable in active markets. Level 3–These are financial instruments where values are derived from techniques in which one or more significant inputs are unobservable. The Company does not have fair valued assets classified under Level 3 as of March 31, 2021 or December 31, 2020. 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 on its Condensed 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. As of March 31, 2021 and December 31, 2020, financial assets measured at fair value on a recurring basis are categorized in the table below based upon the lowest level of significant input to the valuations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of March 31, 2021 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 380,219 ​ $ — ​ $ — ​ $ 380,219 U.S. government agency securities ​ — ​ 62,035 ​ — ​ 62,035 Commercial paper ​ ​ — ​ ​ 29,949 ​ ​ — ​ ​ 29,949 Total ​ $ 380,219 ​ $ 91,984 ​ $ — ​ $ 472,203 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2020 ​ Level 1 Level 2 Level 3 Total US treasury securities ​ $ 470,109 ​ $ — ​ $ — ​ $ 470,109 US government agency securities ​ 91,999 ​ — ​ — ​ 91,999 Total ​ $ 562,108 ​ $ — ​ $ — ​ $ 562,108 ​ 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 revenue and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates include the assumptions made in valuing stock instruments issued for services and used in measuring operating right-of-use assets and operating lease liabilities, accounting for potential liabilities, capitalization of internal-use software development costs, and the valuation allowance associated with 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 of the Company's consolidated operations. 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 portion or all of the deferred tax assets will 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 740-10-30 clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements and prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. ASC Topic 740-10-40 provides guidance on de-recognition, classification, 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. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted and signed into law, and GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date. The CARES Act, among other things, includes changes to the tax provisions that benefits business entities and makes certain technical corrections to the 2017 Tax Cuts and Jobs Act. The tax relief measures for business entities include a five-year net operating loss (“NOL”) carrybacks, suspension of annual deduction limitation of 80% taxable income from net operating losses generated in a tax year beginning after December 31, 2017, changes in the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief, and technical correction to allow accelerated deductions for qualified improvement property. The CARES Act also provides other non-tax benefits to assist those impacted by the pandemic. The Company evaluated the impact of the CARES Act and determined the impact is immaterial for the three months ended March 31, 2021. Leases The Company determines if an arrangement includes a lease at inception. Operating leases are included in its Condensed Consolidated Balance Sheet as Operating lease right-of-use assets and Operating lease liabilities as of March 31, 2021 and December 31, 2020. 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 Standard Update (ASU) No. 2016-02 and ASU No. 2018-10, Leases (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 in non-capital raising transactions as compensation for services rendered. The Company accounts for all stock-based payment awards made to employee, including the employee stock purchase plans based on the authoritative guidance provided by the FASB where the value of the award is measured on the date of grant and recognized over the vesting period. Upon the adoption of ASU No. 2018-07, Compensation-Stock Compensation (“Topic 718”), the Company accounts for stock option grants to non-employees in a similar manner as stock option grants to employees except for the term used in the grant date fair value, therefore no longer requiring a re-measurement at the then-current fair values at each reporting date until the shares underlying the options have vested. The non-employee awards that contain a performance condition that affects the quantity or other terms of the award are measured based on the outcome that is probable. The fair value of the Company's common stock option grants is estimated using a Black-Scholes option pricing model, which uses certain assumptions related to risk-free interest rates, expected volatility, expected 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 materially affect compensation expense recorded in future periods. The Company has in the past issued restricted stock units (“RSUs”) and restricted stock awards (“RSAs”) as part of its share-based compensation programs. 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 that perform various clinical trial activities on its behalf. Service agreements with contract research organizations (“CROs”) and contract manufacturing organizations (“CMOs”) are recognized as the services are incurred. The Company accrues for expenses resulting from obligations under agreements with its third-parties for which the timing of payments does not match the periods over which the materials or services are provided to the Company. Accruals are recorded based on estimates of services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. These estimates are typically based on contracted amounts applied to the proportion of work performed and determined through analysis with internal personnel and external service providers as to the progress or stage of completion of the services. 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 and subsequently recognized as research and development expense when the associated services have been performed. As actual costs become known, the Company adjusts its liabilities and assets. Inputs, such as the extent of services received and the duration of services to be performed, may vary from the Company’s estimates, 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 the Company’s results of operations. The Company’s historical estimates have not been materially different from actual amounts recorded. Preferred Stock The Company applies the accounting standards for distinguishing liabilities from equity when determining the classification and measurement of its preferred stock. Preferred stock subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred stock (including preferred stock that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred stock is classified as stockholders’ equity. Convertible Instruments The Company applies the accounting standards for derivatives and hedging and for distinguishing liabilities from equity when accounting for hybrid contracts that feature conversion options. The accounting standards require companies to bifurcate conversion options from their host instruments and account for them as free-standing derivative financial instruments according to certain criteria. The criteria include circumstances in which (i) the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract, (ii) the hybrid instrument that embodies both the embedded derivative instrument and the host contract is not re-measured at fair value under otherwise applicable generally accepted accounting principles with changes in fair value reported in earnings as they occur and (iii) a separate instrument with the same terms as the embedded derivative instrument would be considered a derivative instrument. The derivative is subsequently marked to market at each reporting date based on current fair value, with the changes in fair value reported in results of operations. Conversion options that contain variable settlement features such as provisions to adjust the conversion price upon subsequent issuances of equity or equity linked securities at exercise prices more favorable than that featured in the hybrid contract generally result in their bifurcation from the host instrument. The Company also records, when necessary, deemed dividends for the intrinsic value of the conversion options embedded in preferred stock based upon the difference between the fair value of the underlying common stock at the commitment date of the transaction and the effective conversion price embedded in the preferred stock. Recent Accounting Standards Adopted In December 2019, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes,

CASH EQUIVALENTS AND INVESTMENT

CASH EQUIVALENTS AND INVESTMENTS	3 Months Ended
	Mar. 31, 2021
CASH EQUIVALENTS AND INVESTMENTS
CASH EQUIVALENTS AND INVESTMENTS	NOTE 3. CASH EQUIVALENTS AND INVESTMENTS Cash equivalents consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Cash equivalents - Money market funds ​ $ 74,424 ​ $ 49,720 ​ ​ ​ ​ ​ ​ ​ Cash equivalents total ​ $ 74,424 ​ $ 49,720 ​ Cash equivalents in the tables above exclude cash demand deposits of $57.5 million and $17.6 million as of March 31, 2021 and December 31, 2020, respectively (in thousands). ​ The following table summarizes the Company’s available-for-sale debt securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ $ 461,976 ​ $ 562,108 Long-term investments ​ ​ 10,227 ​ ​ — Investments total ​ $ 472,203 ​ $ 562,108 ​ The following table summarizes the classification of the Company’s available-for-sale debt securities in its Condensed Consolidated Balance Sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, Investments ​ 2021 2020 U.S. treasury securities ​ $ 380,219 ​ $ 470,109 U.S. government agency securities ​ 62,034 ​ 91,999 Commercial paper ​ 29,950 ​ — Investments total ​ $ 472,203 ​ $ 562,108 ​ The cost and fair value of investments as of March 31, 2021 and December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of March 31, 2021 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 380,135 ​ $ 85 ​ $ (1) ​ $ 380,219 U.S. government agency securities ​ 62,018 ​ 16 ​ — ​ 62,034 Commercial papers ​ ​ 29,954 ​ ​ — ​ ​ (4) ​ ​ 29,950 Total ​ $ 472,107 ​ $ 101 ​ $ (5) ​ $ 472,203 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 Total ​ $ 562,089 ​ $ 50 ​ $ (31) ​ $ 562,108 ​ The following table summarizes the Company’s available-for-sale debt securities by contractual maturity (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Amortized Cost Fair Value ​ ​ ​ ​ ​ ​ ​ Within one year ​ $ 461,878 ​ $ 461,976 One year to two years ​ ​ 10,228 ​ ​ 10,227 Investments total ​ $ 472,106 ​ $ 472,203 ​ All available-for-sale securities held as of March 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. As of March 31, 2021, unrealized losses on available-for-sale investments are not attributed to credit risk. 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.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2021
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	NOTE 4. PROPERTY AND EQUIPMENT Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Lab equipment ​ $ 4,911 ​ $ 4,656 Leasehold improvements ​ 2,573 ​ 2,573 Computer equipment ​ 619 ​ 270 Office furniture and equipment ​ 480 ​ 480 Construction in progress ​ 70,117 ​ 56,758 Total Property and equipment, cost ​ 78,700 ​ 64,737 Less: Accumulated depreciation and amortization ​ (5,950) ​ (5,578) Property and Equipment, net ​ $ 72,750 ​ $ 59,159 ​ Depreciation expense for the three months ended March 31, 2021 and 2020, was approximately $0.4 million and $0.3 million, respectively.

ACCRUED EXPENSES

ACCRUED EXPENSES	3 Months Ended
	Mar. 31, 2021
ACCRUED EXPENSES
ACCRUED EXPENSES	NOTE 5. ACCRUED EXPENSES Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Clinical related ​ $ 12,869 ​ $ 15,661 Accrued payroll and employee related expenses ​ ​ 7,902 ​ ​ 9,032 Commercial manufacturing facility related ​ ​ 8,153 ​ ​ 4,342 R&D Manufacturing related ​ 4,169 ​ 3,266 Legal and related services ​ 963 ​ 1,061 Accrued other ​ 1,718 ​ 1,712 ​ ​ $ 35,774 ​ $ 35,074 ​

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2021
STOCKHOLDERS' EQUITY
STOCKHOLDERS' EQUITY	NOTE 6. STOCKHOLDERS’ EQUITY Authorized Shares of Common Stock On June 10, 2019, the certificate of incorporation of the Company was amended to increase the number of authorized shares of the Company's common stock, par value $0.000041666, from 150,000,000 shares to 300,000,000 shares (the "Certificate of Amendment"). The Certificate of Amendment was approved by the Company's stockholders at the Company's 2019 Annual Meeting of Stockholders held on June 10, 2019. 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. In October 2018, the Company completed an underwritten public offering of 25,300,000 shares of the Company’s common stock at a public offering price of $9.97 per share, before underwriting discounts, which included 3,300,000 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 gross proceeds from the offering, before deducting the underwriting discounts and commissions and other estimated offering expenses payable by the Company, were $252.2 million, with net proceeds to the Company of $236.7 million. In January 2018, the Company closed an underwritten public offering of 15,000,000 shares of the Company's common stock at a public offering price of $11.50 per share, before underwriting discounts, which included 1,956,521 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 gross proceeds from the offering, before deducting the underwriting discounts and commissions and other offering expenses payable by the Company, were $172.5 million, with net proceeds to the Company of $162.0 million. 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 March 31, 2021, 17,000 shares were designated as Series A Convertible Preferred Stock (“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 during the three months ended March 31, 2021 or 2020. As of March 31, 2021 and December 31, 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 shares 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 three months ended March 31, 2021, a total of 738,961 of Series B Convertible Preferred Stock were converted into 738,961 shares of common stock. No shares of Series B Convertible Preferred Stock were converted during the three months ended March 31, 2020. As of March 31, 2021 and December 31, 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. 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, par value $0.000041666 per share (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, originally filed with the Securities and Exchange Commission on May 27, 2020, which became effective immediately upon filing. 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 (the “Securities Act”). 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 three months ended March 31, 2021, the Company received approximately $42.9 million in net proceeds, net of offering costs, through the sale of 1,278,243 shares of its common stock through the Sales Agreement at a weighted average price per share of $34.67.

STOCK BASED COMPENSATION

STOCK BASED COMPENSATION	3 Months Ended
	Mar. 31, 2021
STOCK BASED COMPENSATION
STOCK BASED COMPENSATION	NOTE 7. STOCK BASED COMPENSATION Restricted Stock Units On June 1, 2016, the Company entered into an RSU agreement with the Company’s Chief Executive Officer, Maria Fardis, Ph.D., M.B.A., pursuant to which the Company granted Dr. Fardis 550,000 non-transferrable RSUs at a fair market value price of $5.87 per share as an inducement to her employment pursuant to the exception to The Nasdaq Global Market rules that generally require stockholder approval of equity incentive plans. The 550,000 RSUs vested in installments as follows: (i) 137,500 restricted stock units vested upon the first anniversary of the effective date of Dr. Fardis’ employment agreement; (ii) 275,000 restricted stock units vested upon the satisfaction of certain clinical trial milestones; and (iii) 137,500 restricted stock units vested in equal monthly installments over the 36 -month period following the first anniversary of the effective date of Dr. Fardis’ employment, such that the RSUs were fully vested as of June 1, 2020. As of March 31, 2021, the Company had no RSUs outstanding. Stock-based compensation expense for RSUs are measured based on the closing fair market value of the Company’s common stock on the date of grant. No stock-based compensation expenses relating to RSUs were recorded for the three months ended March 31, 2021, and $0.1 million of stock-based compensation expenses were recorded for the same period ended in 2020 as part of general and administrative expenses. Equity Incentive Plans On October 14, 2011, the Company’s Board of Directors (the “Board”) adopted the 2011 Equity Incentive Plan (the “2011 Plan”). Employees, directors, consultants and advisors of the Company are eligible to participate in the 2011 Plan. The 2011 Plan initially had 180,000 shares of common stock reserved for issuance in the form of incentive stock options, non-qualified options, common stock, and grant appreciation rights. The 2011 Plan was not approved by the Company’s stockholders within the required one-year period following its adoption and, accordingly, no incentive stock options can be granted under that plan. In August 2013, the Board and a majority of the Company’s stockholders approved an amendment to increase the number of shares available under the 2011 Plan from 180,000 shares to 1,700,000 shares, and an amendment to increase the number options or other awards that can be granted to any one person during a twelve (12) month period from 50,000 shares to 300,000 shares. The foregoing amendment to the 2011 Plan became effective in September 2013. On August 20, 2014, the Board amended the 2011 Plan to increase the number of shares available for issuance upon the exercise of stock options under the 2011 Plan from 1,700,000 to 1,900,000 shares, effective immediately. As of March 31, 2021, 11,240 shares were available for future grant under the 2011 Plan. On September 19, 2014, the Board adopted the Iovance Biotherapeutics, Inc. 2014 Equity Incentive Plan (the “2014 Plan”). The 2014 Plan was approved by the Company’s stockholders at the Company’s 2014 Annual Meeting of Stockholders held in November 2014. The 2014 Plan, as approved by the stockholders, authorized the issuance up to an aggregate of 2,350,000 shares of the Company’s common stock. On April 10, 2015, the Board amended the 2014 Plan to increase the total number of shares that can be issued under the 2014 Plan to 4,000,000 shares of the Company’s common stock. The increase in shares available for issuance under the 2014 Plan was approved by the Company’s stockholders at the Company’s 2015 Annual Meeting of Stockholders in June 2015. On August 16, 2016, the Company’s stockholders approved an increase in the total number of shares that can be issued under the 2014 Plan to 9,000,000 shares of the Company’s common stock. As of March 31, 2021, 9,220 shares were available for grant under the Company’s 2014 Plan. On April 22, 2018, the Board adopted the Iovance Biotherapeutics, Inc. 2018 Equity Incentive Plan (the “2018 Plan”). The 2018 Plan was approved by the Company’s stockholders at the annual meeting of stockholders held in June 2018. The 2018 Plan as approved by the stockholders authorized the issuance up to an aggregate of 6,000,000 shares of common stock reserved for issuance 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 March 31, 2021, 4,281,126 shares of common stock were available for grant under the Company’s 2018 Plan. Stock Options A summary of the status of stock options as of March 31, 2021, and the changes during the three months 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 as of December 31, 2020 ​ 12,615,638 $ 18.08 ​ ​ ​ ​ ​ Granted 3,704,589 ​ 45.40 ​ ​ ​ Exercised (423,178) ​ 15.31 ​ ​ ​ Expired/Forfeited (477,823) ​ 29.79 ​ ​ ​ Outstanding as of March 31, 2021 15,419,226 ​ $ 24.35 7.98 ​ $ 169,189 ​ ​ ​ ​ ​ ​ ​ Options exercisable as of March 31, 2021 7,388,773 ​ $ 13.49 6.60 ​ $ 134,955 ​ 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 quarter ended March 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 March 31, 2021. The intrinsic value of the Company’s stock options changes based on the closing price of the Company’s common stock. 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 its 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 three months ended March 31, 2021 was $0.3 million. As of March 31, 2021, no shares were issued under the 2020 ESPP and there was $0.2 million of unrecognized compensation cost associated with the 2020 ESPP, which will be recognized over the remaining 2.3 months. Stock-Based Compensation Total stock-based compensation expense related to all of the Company’s stock-based awards was recorded on the statements of operations as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ Research and development ​ $ 9,202 ​ $ 4,318 ​ General and administrative ​ 7,739 ​ 5,094 ​ Total stock-based compensation expenses ​ $ 16,941 ​ $ 9,412 ​ ​ Total stock-based compensation expenses broken down based on each individual instrument were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ Stock option expenses ​ $ 16,660 ​ $ 9,345 ​ Restricted stock unit expenses ​ — ​ 67 ​ ESPP expenses ​ 281 ​ — ​ Total stock-based compensation expenses ​ $ 16,941 ​ $ 9,412 ​ ​ The Company recorded stock-based compensation expenses related to stock options of $16.7 million and $9.3 million for the three months ended March 31, 2021 and 2020 respectively. As of March 31, 2021, there was $148.4 million of total unrecognized compensation expense related to the options to be recognized over a weighted average period of 2.17 years. The weighted average grant date fair value for employee options granted under the Company’s stock option plans during the three months ended March 31, 2021 and 2020 was $26.42 and $15.67 per option, respectively. The following table summarizes the assumptions relating to options granted pursuant to the Company’s equity incentive plans for the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ ​ ​ ​ ​ Assumptions: 2021 2020 Expected term (years) 5.21 6.19 Expected volatility 70.35% ​ 69.99% Risk-free interest rate ​ 0.36% ​ 1.83% Expected dividend yield ​ 0% ​ 0% ​ Expected Dividend Yield —The Company has never paid dividends and does not expect to pay dividends in the foreseeable future. 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 Term —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. Forfeiture Rate —The Company recognizes forfeitures as they occur. Each of the inputs discussed above is subjective and generally requires significant management judgment.

LICENSES AND AGREEMENTS

LICENSES AND AGREEMENTS	3 Months Ended
	Mar. 31, 2021
LICENSES AND AGREEMENTS
LICENSES AND AGREEMENTS	NOTE 8. LICENSES AND AGREEMENTS National Institutes of Health (NIH) and the National Cancer Institute (NCI) Cooperative Research and Development Agreement (CRADA) In August 2011, the Company signed a five-year CRADA with the NCI to work with Dr. Steven Rosenberg on developing adoptive cell immunotherapies that are designed to destroy metastatic melanoma cells using a patient’s tumor infiltrating lymphocytes. In January 2015, the Company executed an amendment to the CRADA to include four new indications. As amended, in addition to metastatic melanoma, the CRADA included the development of TIL therapy for the treatment of patients with bladder, lung, triple-negative breast, and Human Papilloma Virus (“HPV”)-associated cancers. In August 2016, the NCI and the Company entered a second amendment to the CRADA. The principal changes effected by the second amendment included (i) extending the term of the CRADA by another five years to August 2021, and (ii) modifying the focus on the development of unmodified TIL as a stand-alone therapy or in combination with U.S. Food and Drug Administration (“FDA”) - licensed products and commercially available reagents routinely used for adoptive cell therapy. The parties will continue 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. 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, where the Company holds the investigational new drug application for such clinical trial. The extended CRADA has a five-year term expiring in August 2021. 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 $0.5 million for the three months ended March 31, 2021 and 2020 as research and development expenses. Patent License Agreement Related to the Development and Manufacture of TIL Effective October 5, 2011, 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 (NIH), which was subsequently amended on February 9, 2015 and October 2, 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. The Patent License Agreement requires the Company to pay royalties based on a percentage of net sales (which percentage is in the mid-single digits), a percentage of revenues from sublicensing arrangements, and lump sum benchmark royalty payments on the achievement of certain clinical and regulatory milestones for each of the various indications and other direct costs incurred by the NIH pursuant to the agreement. The Company anticipates making a milestone payment in conjunction with the submission of a Biologics License Application for any of its product candidates covered by the Patent License Agreement. 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. At the same time, 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. The Company recorded research and development costs of $0.2 million and $0.2 million for the three months ended March 31, 2021 and 2020, 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 three months ended March 31, 2021 and 2020. The Company entered into a 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 $0.02 million for the three months ended March 31, 2021 and 2020 as research and development expenses in connection with the Second Moffit License. M.D. Anderson Cancer Center Strategic Alliance Agreement On April 17, 2017, the Company entered into a Strategic Alliance Agreement (the “SAA”) with 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 $0.02 million and $0.2 million associated with the MDACC SAA for the three months ended March 31, 2021 and 2020, respectively, as research and development expenses. WuXi Apptec, Inc. In November 2016, the Company entered into a three-year manufacturing and services agreement (“MSA”) with WuXi AppTec, Inc. (“WuXi”) pursuant to which WuXi agreed to provide manufacturing and other services, which has since been amended and assigned to its subsidiary Iovance Biotherapeutics Manufacturing LLC. Under the 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 statements of work for the first suite were amended in 2019, September 2020 and February 2021, and the second suite was amended in 2019. The statements of work for facility include a fixed component to reserve a dedicated suite and a trained work force, and a variable component, mainly materials and testing used during the manufacturing processes. Both statements of work provide for adjustments to the targeted production capacity levels and the corresponding fixed quarterly fees upon written notice from the Company of 30 days and 90 days for the first and second dedicated suites, respectively. The terms of the related statements of work for the first and second dedicated manufacturing suites currently extend to February 2022 and June 2021, respectively . Cellectis On January 12, 2020, 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, in order 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 agreements with Cellectis of $0.1 million and $0.1 million for the three months ended March 31, 2021 and 2020 respectively, as research and development expenses. Novartis On January 12, 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 has 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. No expenses were recorded for the three months ended March 31, 2021. The Company recorded costs associated with the license agreement from Novartis of $10.0 million as research and development expenses for the three months ended March 31, 2020.

LEGAL PROCEEDINGS

LEGAL PROCEEDINGS	3 Months Ended
	Mar. 31, 2021
LEGAL PROCEEDINGS
LEGAL PROCEEDINGS	NOTE 9. 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. First Solomon Suit for want of prosecution. On August 11, 2020, the Company filed an opposition brief against the Solomon Plaintiffs’ motion for reconsideration. On August 17, 2020, the Solomon Plaintiffs filed a reply brief in support of their motion for reconsideration. On September 2, 2020, the Solomon Plaintiffs filed a notice of appeal of the dismissal for want of prosecution. On January 4, 2021, the court granted the Solomon Plaintiffs motion for reconsideration, and reinstituted the case. On January 15, 2021, the Company filed a notice of appeal of the court’s grant of the Solomon Plaintiffs motion for reconsideration. On February 10, 2021, the Company filed its opening brief in support of its appeal of the court’s grant of the Solomon Plaintiff’s motion for reconsideration. On March 24, 2021, the Solomon Plaintiffs filed their brief in opposition to the Company’s appeal of the court’s grant of the Solomon Plaintiff’s motion for reconsideration. On April 2, 2021, the Company filed its reply brief in support of the Company’s appeal of the court’s grant of the Solomon Plaintiff’s motion for reconsideration. 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. Litigation Involving Dr. Steven Fischkoff Steven Fischkoff v. Lion Biotechnologies, Inc. and Maria Fardis Other Matters. required post-effective amendment, options to purchase 200,000 shares were exercised under the 2011 Equity Incentive Plan. The effect of the delayed post-effective amendment filing on the 200,000 option shares is uncertain, but the issuance and sale of the shares may not have been in compliance with the Form S-8 registration statement. The existence of any liability to the Company, and the amount of any such liability to the Company, as a result of the issuance of the 200,000 shares is uncertain. Accordingly, no accrual for a potential claim has been made by the Company in its consolidated financial statements. 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.

LEASES

LEASES	3 Months Ended
	Mar. 31, 2021
LEASES
LEASES	NOTE 10. LEASES Facilities Leases The Company has evaluated the following existing facility leases and determined that, effective upon the adoption of Topic 842, they were all operating leases. Operating lease right-of-use assets and liabilities were recognized as of January 1, 2019 based on the present value of the remaining lease payments over the lease term. As the Company’s leases do not provide an implicit rate, the Company utilized a third party in determining an incremental borrowing rate based on the information available as of the adoption date of Topic 842 to obtain the present value of lease payments. The Company’s lease terms may include options to extend or terminate the lease which are included in the lease term when it is reasonably certain that it will exercise any such options. Lease expense is recognized on a straight-line basis over the expected lease term. The Company elected not to apply the recognition requirements of Topic 842 for short-term leases that have a lease term of 12 months or less. New Headquarters Lease On February 3, 2021, the Company entered into a lease agreement with ARE-San Francisco No. 63, LLC (the “New Headquarters Lease”) for laboratories and offices to be constructed in Suite 400 of an existing building located at 825 Industrial Road, San Carlos, California (the “Building”), commonly known as The District. Under the New Headquarters Lease, the Company will lease approximately 49,918 rentable square feet of space in the Building (the “Premises”). The New Headquarters Lease is for a term of 120 months , commencing upon the first day of the first full month (the “Rent Commencement Date”) after the earlier to occur of (i) the date that is 12 months and one day after the execution date (the “Commencement Date”), which is January 30, 2022, or (ii) the date that the Tenant Improvements are substantially completed; provided, however, that the Rent Commencement Date shall be delayed 1 day for each day after the Commencement Date that (a) to the extent that, after the Commencement Date, any governmental authority having jurisdiction, as a result of the COVID-19 outbreak in the U.S., declares or implements any order or mandate that restricts construction activities in San Mateo County, California (any such order or mandate, a “Government Mandate”), to the extent that such Government Mandate precludes the construction of tenant improvements, or (b) a landlord delay occurs. Construction of the Company’s offices is expected to extend through 2021. The New Headquarters Lease includes an option to extend the term of the lease for 60 months , exercisable under certain conditions and at a market rate as described in the New Headquarters Lease. Commencing 210 days after the Rent Commencement Date as the result of a rent abatement, the Company’s monthly base rent under the New Headquarters Lease will be approximately $280,000 , subject to an annual increase of 3% . Beginning in 2022, the Company will also be responsible for paying operating expenses. San Carlos Existing Headquarters Leases On August 4, 2016, the Company entered into an agreement to lease 8,733 square feet in San Carlos, California. The term of the lease is 54 months subsequent to the commencement date and will expire in April 2021. Monthly lease payments are approximately $38,000. On April 28, 2017, the Company entered into a sublease agreement with Teradata US, Inc., pursuant to which the Company agreed to sublease certain office space located adjacent to the Company’s headquarters for approximately $26,000 per month. The space consists of approximately 11,449 rentable square feet in the building located in San Carlos, California. The sublease for this space expired on October 31, 2018. Monthly lease payments were approximately $26,000. On October 19, 2018, the Company entered into an agreement to lease 12,322 square feet of office space located adjacent to the Company’s headquarters in San Carlos, California. This lease replaces the sublease of 11,449 square feet of office space in the same facility that expired on October 31, 2018. The term of the lease is 30 months subsequent to the commencement date, November 1, 2018, and will expire in April 2021. Monthly lease payments are approximately $59,000, subject to an annual increase of 3%. On June 19, 2019, the Company entered into a first amendment (the “Amended Lease”) to its previously disclosed lease agreement with Hudson Skyway Landing, LLC (the “Lease”) for additional space at its corporate headquarters in San Carlos, California. Under the Amended Lease, the Company will lease an additional 8,110 square feet (the “Expansion Space”), for a total of approximately 20,432 square feet of space on the first floor of the building located at 999 Skyway Road, San Carlos, California, commonly known as Skyway Landing II. The term of the Amended Lease remains the same as that of the Lease and expires on April 30, 2021, unless earlier terminated in accordance with the Amended Lease. The Company’s monthly base rent for the Expansion Space under the Amended Lease will be approximately $39,000 for the first year, and $40,000 for the second year. On February 3, 2021, the Company entered into two amendments (the “Suite 150 Second Amendment” and the “Suite 100 and Suite 125 First Amendment”) to its previously disclosed lease agreements with Hudson Skyway Landing, LLC, for space located on the first floor of the building located at 999 Skyway Road, San Carlos, California, commonly known as Skyway Landing II. Under the Suite 100 and Suite 125 Second Amendment, the Company will extend its previously disclosed amended lease of approximately 20,432 rentable square feet of space, which would have expired on April 30, 2021, to December 31, 2021. The Company’s monthly base rent under the Suite 100 and Suite 125 Second Amendment will be approximately $103,000. The Company is also responsible for paying its portion of operating expenses and real estate taxes. The Company has an option to extend the expiration of the Suite 100 and Suite 125 Second Amendment for one month or six months , at its discretion, by providing notice as specified in the Suite 100 and Suite 125 Second Amendment. Under the Suite 150 First Amendment, the Company will extend its previously disclosed lease of approximately 8,733 rentable square feet of space, which also would have expired on April 30, 2021, to December 31, 2021. The Company’s monthly base rent under the Suite 150 First Amendment will be approximately $44,000. The Company is also responsible for paying its portion of operating expenses and real estate taxes. The Company has an option to extend the expiration of the Suite 150 First Amendment for one month or six months , at its discretion, by providing notice as specified in the Suite 150 First Amendment. Tampa Lease In December 2014, the Company commenced a five-year non-cancellable operating lease with the University of South Florida Research Foundation for a 5,115 square foot facility located in Tampa, Florida. The facility is part of the University of South Florida research park and is used as the Company’s research and development facilities. The Company had the option to extend the lease term of this facility for an additional five-year period on the same terms and conditions, except that the base rent for the renewal term will be increased in accordance with the applicable consumer price index. In April 2015, the Company amended the original lease agreement to increase the rentable space to 6,043 square feet. In September 2016, the Company further increased the rentable space to 8,673 square feet. The per square foot cost and term of the lease were unchanged, and rent payments are approximately $20,000 per month. In December 2019, the Company entered into an agreement to extend the lease term to December 18, 2024 for approximately $20,500 a month. In June 2020, the Company amended the lease agreement to further increase the rentable space to 13,139 square feet and extend the lease term to June 30, 2025 for approximately $34,500 a month. New York Lease The Company leased office space in New York for a monthly rental of approximately $18,000 a month from January 2017 through July 2017. On June 5, 2017, the Company entered into an agreement whereby the Company will lease office space from August 1, 2017 to July 31, 2018, for approximately $9,000 a month. On April 20, 2018, the Company entered into an agreement to extend the lease term to January 31, 2019 for approximately $7,000 a month. On November 2, 2018, the Company entered into an agreement to extend the lease term to July 31, 2019 for approximately $4,000 a month. On May 1, 2019, the Company entered into an agreement to extend the lease term to January 31, 2020 for approximately $4,000 a month. On October 24, 2019, the Company entered into an agreement to extend the lease term to April 30, 2020 for approximately $4,000 a month. On January 23, 2020, the Company entered into an agreement to extend the lease term to July 31, 2020 for approximately $4,000 a month. On May 24, 2020, the Company entered into an agreement to extend the lease term to October 31, 2020 for approximately $4,000 a month. On September 1, 2020, the Company entered into an agreement to extend the lease term to January 31, 2021, for approximately $4,000 a month. On January 31, 2021, the lease terminated, and the Company closed its New York office. Philadelphia Office Lease On May 2, 2019, the Company entered into an agreement to lease approximately 1,500 square feet of office space in Philadelphia, Pennsylvania until July 1, 2019 for a rate of $2,000 a month, and then approximately 4,500 square feet of office space for the remainder of a three-year term at an initial rate of $11,063 per month, subject to annual increases of 2.5%. On August 1, 2020, the Company entered into an agreement to lease approximately 2,965 square feet of a training facility space in Philadelphia, Pennsylvania for a twelve-month term at a rate of approximately $6,500 per month. Commercial Manufacturing Facility Agreement On May 28, 2019, the Company entered into a lease agreement with 300 Rouse Boulevard, LLC (the “Commercial Manufacturing Facility Lease”) for a build-to-suit commercial manufacturing facility, laboratories, and offices located in Philadelphia, Pennsylvania. Under the Commercial Manufacturing Facility Lease, the Company leases approximately 136,000 rentable square feet of space in a building located at 300 Rouse Boulevard, Philadelphia, Pennsylvania (the “Premises”). The construction of the commercial manufacturing facility began in July 2019 and has been substantially completed. The Company determined the commencement date of the Commercial Manufacturing Lease to be October 7, 2020 in accordance with Topic 842 when its landlord made the Premise available for the Company’s use and the Company obtained control over the use of the Premises. The Commercial Manufacturing Facility Lease includes an option to extend the term of the lease, exercisable under certain conditions as described in the Commercial Manufacturing Facility Lease, such that the overall term, when added to the initial term, shall be 359 months, by giving the landlord prior written notice thereof at least 18 months in advance of the expiration date. In determining the lease term, the Company did not include the periods covered by the option to extend the lease as it determined that it is not reasonably certain that the Company will exercise such option. Upon the commencement date, the Company recognized operating lease liabilities and right-of-use assets of $41.3 million and $45.7 million, respectively. The Company’s monthly base rent under the Lease will be approximately $320,000, subject to an annual increase of 2% for the first ten years, and an annual increase of the greater of 2% or 75% of the average ten-year consumer price index. The Company is also responsible for paying operating expenses, which are expected to be approximately $72,000 per month in 2021. 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. In conjunction with the adoption of Topic 842 on January 1, 2019, the Company reevaluated all of its material contracts it has, to determine whether they contain a lease under Topic 840. An arrangement is considered a lease or contains a lease if an underlying asset is explicitly or implicitly identified and use of the asset is controlled by the customer. Based on this evaluation, the Company concluded that all of its contracts with CMOs contained embedded operating leases because the suites used for its production are implicitly identified, is only used by the Company exclusively 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. The guidance 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 used 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 Company leases certain furniture and equipment that has a lease term of 12 months or less. Since the commencement date does 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. The balance sheet classification of the Company’s right-of-use asset and lease liabilities was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Operating lease right-of-use assets ​ $ 55,131 ​ $ 54,756 Operating lease liabilities ​ ​ ​ ​ ​ Current portion included in current liabilities ​ ​ 5,916 ​ 6,284 long-term portion included in non-current liabilities ​ ​ 47,083 ​ 45,375 Total Operating lease liabilities ​ $ 52,999 ​ $ 51,659 ​ The following table summarizes components of lease expenses, which were included in Total expenses in the Company’s Condensed Consolidated Statement of Operations, and other information related to its operating leases as follows (in thousands except weighted-average remaining lease terms and discount rates): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 3,398 ​ $ 1,636 Variable lease cost ​ ​ 710 ​ ​ 1,371 Short-term lease cost ​ ​ 36 ​ ​ 17 Total lease cost ​ $ 4,144 ​ $ 3,024 ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in Operating cashflows ​ $ 2,322 ​ $ 2,197 Right-of-use assets obtained from entering new leases ​ $ 618 ​ $ — Increase in right-of-use assets from lease modifications ​ $ 2,159 ​ $ 479 Weighted-average remaining lease terms (years) ​ ​ 17.55 ​ ​ 1.73 Weighted-average discount rates ​ ​ 7.4% ​ ​ 7.5% ​ Variable lease cost is determined based on performance or usage in accordance with the contractual agreements, and not based on an index or rate. As of March 31, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ ​ ​ leases leases Total 2021 ​ $ 4,226 ​ $ 3,879 ​ $ 8,105 2022 ​ 4,414 ​ 361 ​ 4,775 2023 ​ 4,423 ​ — ​ 4,423 2024 ​ 4,516 ​ — ​ 4,516 2025 ​ 4,372 ​ — ​ 4,372 Thereafter ​ 74,899 ​ — ​ 74,899 Total lease payments ​ $ 96,850 ​ $ 4,240 ​ $ 101,090 Less: Present value adjustment ​ (48,024) ​ (67) ​ (48,091) Operating lease liabilities ​ $ 48,826 ​ $ 4,173 ​ $ 52,999 ​ Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, the Company used its incremental borrowing rate based on the information available at the date of adoption of Topic 842 or the date of lease modifications.

LONG-TERM NOTE

LONG-TERM NOTE	3 Months Ended
	Mar. 31, 2021
LONG-TERM NOTE
LONG-TERM NOTE	NOTE 11. LONG-TERM NOTE 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 The Company concludes that it is not reasonably assured that all or a portion of the loan will be forgiven as of March 31, 2021, and therefore accounted for the Job Creation Loan as debt in accordance with ASC Topic 470 – Debt, as opposed to as an in-substance government grant, and classified as a long-term debt in its Condensed Consolidated Balance Sheet as of March 31, 2021.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2021
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS	NOTE 12. RELATED PARTY TRANSACTIONS On September 14, 2017, the Company entered into a three-year consulting agreement with Iain Dukes, D. Phil, the Chairman of the Board. As compensation for his consulting services, the Company granted Dr. Dukes a stock option to purchase up to 150,000 shares of the Company’s common stock, at an exercise price of $7.30 per share. Under the consulting agreement, Dr. Dukes agreed to provide the Company with services regarding business development opportunities, licensing transactions and technology acquisitions by the Company, and any such strategic initiatives appropriate for the Company that Dr. Dukes may identify. The granted stock options vest in 12 million in stock-based compensation expense related to this consulting agreement during the three months ended March 31, 2021 and 2020, respectively.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2021
INCOME TAXES
INCOME TAXES	NOTE 13. INCOME TAXES The Company did not record income tax expenses for the three months ended March 31, 2021 and 2020, respectively as the Company expected to be in a taxable loss position in 2021 and 2020, and the net deferred tax assets are fully offset by a valuation allowance as it is not more likely than not that the benefit will be realized. Therefore, the Company’s effective tax rate was 0.0% , for the three months ended March 31, 2021 and 2020, respectively. As of March 31, 2021, the Company remains in a cumulative book loss position and does not have sufficient positive evidence to realize its net deferred tax assets. As such, the Company continues to maintain a full valuation allowance against its net deferred tax assets.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Cash, Cash Equivalents, and Short-term 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” and are presented at fair value as either a current or non-current asset based on the length of maturity from the reporting date. Unrealized gains and losses on available-for-sale securities are included in accumulated other comprehensive income. Any impairment losses related to credit losses (if any) are included in an allowance for credit losses with an offsetting entry to net loss. No impairment losses related to credit losses were recognized for the three months ended March 31, 2021 or March 31, 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 net interest income in the Condensed Consolidated Statements of Operations. Gains and losses on securities sold are recorded based on the specific identification method and are included in net interest income in the Condensed Consolidated Statements of Operations. The Company has not incurred any realized gains or losses from sales of securities to date. The Company’s investment policy limits investments to certain types of instruments such as certificates of deposit, money market instruments, obligations issued by the U.S. government and U.S. government agencies as well as corporate debt securities and commercial papers, 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 $5,450,000 million for the benefit of the landlord for its commercial manufacturing facility used as a security deposit for the lease (See Note 10 - Leases), the second one for $74,685 for the benefit of a utilities service provider, and the third one for $559,082 for the benefit of the landlord for its new headquarters lease. The total amount is classified as Restricted Cash on the Condensed Consolidated Balance Sheet. The first letter of credit originally expired on May 28, 2020, however, it automatically extends for additional one-year periods, without written agreement, to May 28 in each succeeding calendar year, through at least 60 days after the lease expiration date. Further, on the expiration of the seventh year of the lease, and each anniversary date thereafter, the letter of credit may be decreased by $1,000,000, with a minimum security deposit of $1,450,000 maintained through the end of the lease term. The second letter of credit of $74,685 expired on March 9, 2021, however, it automatically extends, without written agreement, to the expiration date of December 1, 2022. The third letter of credit of $559,082 expires on February 1, 2032, however, it will be automatically extended, without written agreement, for one year periods to February in each succeeding calendar year. As of March 31, 2021 and December 31, 2020, restricted cash consisted of $6.1 million and $5.5 million, respectively. This amount has been classified as a non-current asset on the Company’s Condensed Consolidated Balance Sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash, reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 131,954 ​ $ 52,540 Restricted cash (included in non-current assets on the condensed consolidated balance sheets) ​ 6,084 ​ 5,525 Total cash, cash equivalents and restricted cash ​ $ 138,038 ​ $ 58,065 ​
Loss per Share	Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock 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 shares of common stock issuable upon (i) the exercise of outstanding stock options and warrants, (ii) purchases though the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), (iii) vesting of restricted stock units and restricted stock awards, and (iv) conversion of preferred stock, are only included in the calculation of diluted net loss per share when their effect is dilutive. As of March 31, 2021 and 2020, the following outstanding common stock equivalents have been excluded from the calculation of net loss per share because their impact would be anti-dilutive. ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ 2021 2020 Stock options ​ 15,419,226 12,136,899 Series A Convertible Preferred Stock* ​ 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 2020 ESPP ​ 55,963 ​ — Restricted stock units ​ — 11,458 ​ ​ 18,414,347 15,826,476 ​ * on an as-converted basis The effect of potentially dilutive securities would be reflected in diluted earnings per share of common stock 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 ASC 820, Fair Value Measurements and Disclosures, fair value is defined as the price at which an asset could be exchanged, or a liability transferred in a transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or parameters are not available, valuation models are applied. Assets and liabilities recorded at fair value in the Company’s financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities, are as follows: Level 1–These are investments where values are based on unadjusted quoted prices for identical assets in an active market that the Company has the ability to access. Level 2–These are investments where values are based on quoted market prices in markets that are not active or model derived valuations in which all significant inputs are observable in active markets. Level 3–These are financial instruments where values are derived from techniques in which one or more significant inputs are unobservable. The Company does not have fair valued assets classified under Level 3 as of March 31, 2021 or December 31, 2020. 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 on its Condensed 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. As of March 31, 2021 and December 31, 2020, financial assets measured at fair value on a recurring basis are categorized in the table below based upon the lowest level of significant input to the valuations (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of March 31, 2021 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 380,219 ​ $ — ​ $ — ​ $ 380,219 U.S. government agency securities ​ — ​ 62,035 ​ — ​ 62,035 Commercial paper ​ ​ — ​ ​ 29,949 ​ ​ — ​ ​ 29,949 Total ​ $ 380,219 ​ $ 91,984 ​ $ — ​ $ 472,203 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2020 ​ Level 1 Level 2 Level 3 Total US treasury securities ​ $ 470,109 ​ $ — ​ $ — ​ $ 470,109 US government agency securities ​ 91,999 ​ — ​ — ​ 91,999 Total ​ $ 562,108 ​ $ — ​ $ — ​ $ 562,108
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 revenue and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates include the assumptions made in valuing stock instruments issued for services and used in measuring operating right-of-use assets and operating lease liabilities, accounting for potential liabilities, capitalization of internal-use software development costs, and the valuation allowance associated with 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 of the Company's consolidated operations.
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 portion or all of the deferred tax assets will 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 740-10-30 clarifies the accounting for uncertainty in income taxes recognized in an enterprise’s financial statements and prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. ASC Topic 740-10-40 provides guidance on de-recognition, classification, 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. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted and signed into law, and GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date. The CARES Act, among other things, includes changes to the tax provisions that benefits business entities and makes certain technical corrections to the 2017 Tax Cuts and Jobs Act. The tax relief measures for business entities include a five-year net operating loss (“NOL”) carrybacks, suspension of annual deduction limitation of 80% taxable income from net operating losses generated in a tax year beginning after December 31, 2017, changes in the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief, and technical correction to allow accelerated deductions for qualified improvement property. The CARES Act also provides other non-tax benefits to assist those impacted by the pandemic. The Company evaluated the impact of the CARES Act and determined the impact is immaterial for the three months ended March 31, 2021.
Leases	Leases The Company determines if an arrangement includes a lease at inception. Operating leases are included in its Condensed Consolidated Balance Sheet as Operating lease right-of-use assets and Operating lease liabilities as of March 31, 2021 and December 31, 2020. 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 Standard Update (ASU) No. 2016-02 and ASU No. 2018-10, Leases (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 in non-capital raising transactions as compensation for services rendered. The Company accounts for all stock-based payment awards made to employee, including the employee stock purchase plans based on the authoritative guidance provided by the FASB where the value of the award is measured on the date of grant and recognized over the vesting period. Upon the adoption of ASU No. 2018-07, Compensation-Stock Compensation (“Topic 718”), the Company accounts for stock option grants to non-employees in a similar manner as stock option grants to employees except for the term used in the grant date fair value, therefore no longer requiring a re-measurement at the then-current fair values at each reporting date until the shares underlying the options have vested. The non-employee awards that contain a performance condition that affects the quantity or other terms of the award are measured based on the outcome that is probable. The fair value of the Company's common stock option grants is estimated using a Black-Scholes option pricing model, which uses certain assumptions related to risk-free interest rates, expected volatility, expected 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 materially affect compensation expense recorded in future periods. The Company has in the past issued restricted stock units (“RSUs”) and restricted stock awards (“RSAs”) as part of its share-based compensation programs. 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 that perform various clinical trial activities on its behalf. Service agreements with contract research organizations (“CROs”) and contract manufacturing organizations (“CMOs”) are recognized as the services are incurred. The Company accrues for expenses resulting from obligations under agreements with its third-parties for which the timing of payments does not match the periods over which the materials or services are provided to the Company. Accruals are recorded based on estimates of services received and efforts expended pursuant to agreements established with CROs, CMOs and other outside service providers. These estimates are typically based on contracted amounts applied to the proportion of work performed and determined through analysis with internal personnel and external service providers as to the progress or stage of completion of the services. 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 and subsequently recognized as research and development expense when the associated services have been performed. As actual costs become known, the Company adjusts its liabilities and assets. Inputs, such as the extent of services received and the duration of services to be performed, may vary from the Company’s estimates, 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 the Company’s results of operations. The Company’s historical estimates have not been materially different from actual amounts recorded.
Preferred Stock	Preferred Stock The Company applies the accounting standards for distinguishing liabilities from equity when determining the classification and measurement of its preferred stock. Preferred stock subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred stock (including preferred stock that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred stock is classified as stockholders’ equity.
Convertible Instruments	Convertible Instruments The Company applies the accounting standards for derivatives and hedging and for distinguishing liabilities from equity when accounting for hybrid contracts that feature conversion options. The accounting standards require companies to bifurcate conversion options from their host instruments and account for them as free-standing derivative financial instruments according to certain criteria. The criteria include circumstances in which (i) the economic characteristics and risks of the embedded derivative instrument are not clearly and closely related to the economic characteristics and risks of the host contract, (ii) the hybrid instrument that embodies both the embedded derivative instrument and the host contract is not re-measured at fair value under otherwise applicable generally accepted accounting principles with changes in fair value reported in earnings as they occur and (iii) a separate instrument with the same terms as the embedded derivative instrument would be considered a derivative instrument. The derivative is subsequently marked to market at each reporting date based on current fair value, with the changes in fair value reported in results of operations. Conversion options that contain variable settlement features such as provisions to adjust the conversion price upon subsequent issuances of equity or equity linked securities at exercise prices more favorable than that featured in the hybrid contract generally result in their bifurcation from the host instrument. The Company also records, when necessary, deemed dividends for the intrinsic value of the conversion options embedded in preferred stock based upon the difference between the fair value of the underlying common stock at the commitment date of the transaction and the effective conversion price embedded in the preferred stock.
Recent Accounting Standards	Recent Accounting Standards Adopted In December 2019, the Financial Accounting Standards Board (“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 POLICIES (Tables)	3 Months Ended
	Mar. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of cash and cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash, reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 131,954 ​ $ 52,540 Restricted cash (included in non-current assets on the condensed consolidated balance sheets) ​ 6,084 ​ 5,525 Total cash, cash equivalents and restricted cash ​ $ 138,038 ​ $ 58,065
Schedule of Antidilutive securities excluded from computation of earnings per share	​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ 2021 2020 Stock options ​ 15,419,226 12,136,899 Series A Convertible Preferred Stock* ​ 97,000 97,000 Series B Convertible Preferred Stock* ​ 2,842,158 3,581,119 2020 ESPP ​ 55,963 ​ — Restricted stock units ​ — 11,458 ​ ​ 18,414,347 15,826,476 ​ * on an as-converted basis
Schedule of assets measured at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of March 31, 2021 ​ Level 1 Level 2 Level 3 Total U.S. treasury securities ​ $ 380,219 ​ $ — ​ $ — ​ $ 380,219 U.S. government agency securities ​ — ​ 62,035 ​ — ​ 62,035 Commercial paper ​ ​ — ​ ​ 29,949 ​ ​ — ​ ​ 29,949 Total ​ $ 380,219 ​ $ 91,984 ​ $ — ​ $ 472,203 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Assets at Fair Value as of December 31, 2020 ​ Level 1 Level 2 Level 3 Total US treasury securities ​ $ 470,109 ​ $ — ​ $ — ​ $ 470,109 US government agency securities ​ 91,999 ​ — ​ — ​ 91,999 Total ​ $ 562,108 ​ $ — ​ $ — ​ $ 562,108

CASH EQUIVALENTS AND INVESTME_2

CASH EQUIVALENTS AND INVESTMENTS (Tables)	3 Months Ended
	Mar. 31, 2021
CASH EQUIVALENTS AND INVESTMENTS
Schedule of cash, money market funds and short-term investments	Cash equivalents consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Cash equivalents - Money market funds ​ $ 74,424 ​ $ 49,720 ​ ​ ​ ​ ​ ​ ​ Cash equivalents total ​ $ 74,424 ​ $ 49,720
Schedule of available-for-sale debt securities	The following table summarizes the Company’s available-for-sale debt securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Short-term investments ​ $ 461,976 ​ $ 562,108 Long-term investments ​ ​ 10,227 ​ ​ — Investments total ​ $ 472,203 ​ $ 562,108
Schedule of cost and fair value of cash equivalents and short-term investments	The following table summarizes the classification of the Company’s available-for-sale debt securities in its Condensed Consolidated Balance Sheets (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, Investments ​ 2021 2020 U.S. treasury securities ​ $ 380,219 ​ $ 470,109 U.S. government agency securities ​ 62,034 ​ 91,999 Commercial paper ​ 29,950 ​ — Investments total ​ $ 472,203 ​ $ 562,108 ​ The cost and fair value of investments as of March 31, 2021 and December 31, 2020 were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ ​ ​ As of March 31, 2021 Cost Gains Losses Fair Value U.S. treasury securities ​ $ 380,135 ​ $ 85 ​ $ (1) ​ $ 380,219 U.S. government agency securities ​ 62,018 ​ 16 ​ — ​ 62,034 Commercial papers ​ ​ 29,954 ​ ​ — ​ ​ (4) ​ ​ 29,950 Total ​ $ 472,107 ​ $ 101 ​ $ (5) ​ $ 472,203 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 Total ​ $ 562,089 ​ $ 50 ​ $ (31) ​ $ 562,108
Schedule of available-for-sale debt securities by contractual maturity	The following table summarizes the Company’s available-for-sale debt securities by contractual maturity (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Amortized Cost Fair Value ​ ​ ​ ​ ​ ​ ​ Within one year ​ $ 461,878 ​ $ 461,976 One year to two years ​ ​ 10,228 ​ ​ 10,227 Investments total ​ $ 472,106 ​ $ 472,203

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2021
PROPERTY AND EQUIPMENT
Schedule of Property and equipment	Property and equipment, net consists of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ 2021 2020 Lab equipment ​ $ 4,911 ​ $ 4,656 Leasehold improvements ​ 2,573 ​ 2,573 Computer equipment ​ 619 ​ 270 Office furniture and equipment ​ 480 ​ 480 Construction in progress ​ 70,117 ​ 56,758 Total Property and equipment, cost ​ 78,700 ​ 64,737 Less: Accumulated depreciation and amortization ​ (5,950) ​ (5,578) Property and Equipment, net ​ $ 72,750 ​ $ 59,159

ACCRUED EXPENSES (Tables)

ACCRUED EXPENSES (Tables)	3 Months Ended
	Mar. 31, 2021
ACCRUED EXPENSES
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ Clinical related ​ $ 12,869 ​ $ 15,661 Accrued payroll and employee related expenses ​ ​ 7,902 ​ ​ 9,032 Commercial manufacturing facility related ​ ​ 8,153 ​ ​ 4,342 R&D Manufacturing related ​ 4,169 ​ 3,266 Legal and related services ​ 963 ​ 1,061 Accrued other ​ 1,718 ​ 1,712 ​ ​ $ 35,774 ​ $ 35,074

STOCK BASED COMPENSATION (Table

STOCK BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2021
STOCK BASED COMPENSATION
Schedule of status of stock options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ Aggregate ​ ​ Number ​ Average ​ Remaining ​ Intrinsic ​ ​ of ​ Exercise ​ Contract ​ Value ​ Options Price Life (in thousands) Outstanding as of December 31, 2020 ​ 12,615,638 $ 18.08 ​ ​ ​ ​ ​ Granted 3,704,589 ​ 45.40 ​ ​ ​ Exercised (423,178) ​ 15.31 ​ ​ ​ Expired/Forfeited (477,823) ​ 29.79 ​ ​ ​ Outstanding as of March 31, 2021 15,419,226 ​ $ 24.35 7.98 ​ $ 169,189 ​ ​ ​ ​ ​ ​ ​ Options exercisable as of March 31, 2021 7,388,773 ​ $ 13.49 6.60 ​ $ 134,955
Schedule of stock-based compensation	Total stock-based compensation expense related to all of the Company’s stock-based awards was recorded on the statements of operations as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ Research and development ​ $ 9,202 ​ $ 4,318 ​ General and administrative ​ 7,739 ​ 5,094 ​ Total stock-based compensation expenses ​ $ 16,941 ​ $ 9,412 ​ ​ Total stock-based compensation expenses broken down based on each individual instrument were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ Stock option expenses ​ $ 16,660 ​ $ 9,345 ​ Restricted stock unit expenses ​ — ​ 67 ​ ESPP expenses ​ 281 ​ — ​ Total stock-based compensation expenses ​ $ 16,941 ​ $ 9,412 ​
Schedule of share-based payment award, stock options, valuation assumptions	​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, ​ ​ ​ ​ ​ Assumptions: 2021 2020 Expected term (years) 5.21 6.19 Expected volatility 70.35% ​ 69.99% Risk-free interest rate ​ 0.36% ​ 1.83% Expected dividend yield ​ 0% ​ 0%

LEASES (Tables)

LEASES (Tables)	3 Months Ended
	Mar. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 Operating lease right-of-use assets ​ $ 55,131 ​ $ 54,756 Operating lease liabilities ​ ​ ​ ​ ​ Current portion included in current liabilities ​ ​ 5,916 ​ 6,284 long-term portion included in non-current liabilities ​ ​ 47,083 ​ 45,375 Total Operating lease liabilities ​ $ 52,999 ​ $ 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 Condensed Consolidated Statement of Operations, and other information related to its operating leases as follows (in thousands except weighted-average remaining lease terms and discount rates): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ ​ ​ Operating lease cost ​ $ 3,398 ​ $ 1,636 Variable lease cost ​ ​ 710 ​ ​ 1,371 Short-term lease cost ​ ​ 36 ​ ​ 17 Total lease cost ​ $ 4,144 ​ $ 3,024 ​ ​ ​ ​ ​ ​ ​ Other information ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash paid for amounts included in the measurement of lease liabilities included in Operating cashflows ​ $ 2,322 ​ $ 2,197 Right-of-use assets obtained from entering new leases ​ $ 618 ​ $ — Increase in right-of-use assets from lease modifications ​ $ 2,159 ​ $ 479 Weighted-average remaining lease terms (years) ​ ​ 17.55 ​ ​ 1.73 Weighted-average discount rates ​ ​ 7.4% ​ ​ 7.5%
Schedule of minimum lease commitments	As of March 31, 2021, the maturities of the Company’s operating lease liabilities were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ CMO ​ ​ ​ ​ Facility ​ embedded ​ ​ ​ ​ ​ leases leases Total 2021 ​ $ 4,226 ​ $ 3,879 ​ $ 8,105 2022 ​ 4,414 ​ 361 ​ 4,775 2023 ​ 4,423 ​ — ​ 4,423 2024 ​ 4,516 ​ — ​ 4,516 2025 ​ 4,372 ​ — ​ 4,372 Thereafter ​ 74,899 ​ — ​ 74,899 Total lease payments ​ $ 96,850 ​ $ 4,240 ​ $ 101,090 Less: Present value adjustment ​ (48,024) ​ (67) ​ (48,091) Operating lease liabilities ​ $ 48,826 ​ $ 4,173 ​ $ 52,999

GENERAL ORGANIZATION AND BUSI_2

GENERAL ORGANIZATION AND BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
GENERAL ORGANIZATION AND BUSINESS
Net Loss	$ 75,449	$ 69,595
Net cash used in operating activities	62,391	65,292
Proceeds from the issuance of common stock, net	42,885
Cash, cash equivalents and short-term investments	610,200
Cash equivalents, short-term investments, and restricted cash	131,900
Cash and cash equivalents	131,954	52,540	$ 67,329
Short-term investments	472,203		562,108
Short-term investments	461,976		562,108
Long-term investments	10,227
Restricted cash	$ 6,084	$ 5,525	$ 5,525

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash equivalents and Restricted Cash (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Security deposit	$ 1,450,000
Security deposit for the benefit of the landlord for its commercial manufacturing facility	5,450,000
Security deposit for the benefit of utilities service provider	74,685
Benefit of landlord	559,082
Letter of credit	1,000,000
Cash and cash equivalents	131,954,000	$ 67,329,000	$ 52,540,000
Restricted cash (included in non-current assets on the condensed consolidated balance sheets)	6,084,000	5,525,000	5,525,000
Total cash, cash equivalents and restricted cash	$ 138,038,000	$ 72,854,000	$ 58,065,000	$ 19,419,000

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Loss per share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive securities excluded from calculation of net loss per share	18,414,347	15,826,476
Stock option
Antidilutive securities excluded from calculation of net loss per share	15,419,226	12,136,899
Employee Stock Purchase Plan
Antidilutive securities excluded from calculation of net loss per share	55,963
Restricted stock units
Antidilutive securities excluded from calculation of net loss per share		11,458
Series A Convertible Preferred Stock
Antidilutive securities excluded from calculation of net loss per share	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

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Fair value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Total	$ 472,203	$ 562,108
U.S. treasury securities
Total	380,219	470,109
U.S. government agency securities
Total	62,035	91,999
Commercial Paper
Total	29,949
Level 1
Total	380,219	562,108
Level 1 | U.S. treasury securities
Total	380,219	470,109
Level 1 | U.S. government agency securities
Total		$ 91,999
Level 2
Total	91,984
Level 2 | U.S. government agency securities
Total	62,035
Level 2 | Commercial Paper
Total	$ 29,949

CASH EQUIVALENTS AND INVESTME_3

CASH EQUIVALENTS AND INVESTMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash equivalents total	$ 74,424	$ 49,720
Money Market Funds
Cash equivalents total	74,424	49,720
Demand Deposits
Cash equivalents total	$ 57,500	$ 17,600

CASH EQUIVALENTS AND INVESTME_4

CASH EQUIVALENTS AND INVESTMENTS - Available for sale debt securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
CASH EQUIVALENTS AND INVESTMENTS
Short-term investments	$ 461,976	$ 562,108
Long-term investments	10,227
Investments total	$ 472,203	$ 562,108

CASH EQUIVALENTS AND INVESTME_5

CASH EQUIVALENTS AND INVESTMENTS - Short-term investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Short-term investments	$ 472,203	$ 562,108
U.S. treasury securities
Short-term investments	380,219	470,109
U.S. government agency securities
Short-term investments	62,034	$ 91,999
Commercial Paper
Short-term investments	$ 29,950

CASH EQUIVALENTS AND INVESTME_6

CASH EQUIVALENTS AND INVESTMENTS - Cost and fair value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost	$ 472,107	$ 562,089
Gross Unrealized Gains	101	50
Gross Unrealized Losses	(5)	(31)
Fair Value	472,203	562,108
U.S. treasury securities
Amortized Cost	380,135	470,108
Gross Unrealized Gains	85	30
Gross Unrealized Losses	(1)	(29)
Fair Value	380,219	470,109
U.S. government agency securities
Amortized Cost	62,018	91,981
Gross Unrealized Gains	16	20
Gross Unrealized Losses		(2)
Fair Value	62,034	$ 91,999
Commercial Paper
Amortized Cost	29,954
Gross Unrealized Losses	(4)
Fair Value	$ 29,950

CASH EQUIVALENTS AND INVESTME_7

CASH EQUIVALENTS AND INVESTMENTS - Contractual maturity (Details) $ in Thousands	Mar. 31, 2021USD ($)
Amortized Cost
Within one year	$ 461,878
One year to two years	10,228
Amortized cost investments total	472,106
Fair Value
Within one year	461,976
One year to two years	10,227
Fair value investments total	$ 472,203

PROPERTY AND EQUIPMENT - (Detai

PROPERTY AND EQUIPMENT - (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	$ 78,700	$ 64,737
Less: Accumulated depreciation and amortization	(5,950)	(5,578)
Property and equipment, net	72,750	59,159
Lab equipment
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	4,911	4,656
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	2,573	2,573
Computer equipment
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	619	270
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	480	480
Construction in progress
Property, Plant and Equipment [Line Items]
Total Property and equipment, cost	$ 70,117	$ 56,758

PROPERTY AND EQUIPMENT - Other

PROPERTY AND EQUIPMENT - Other information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
PROPERTY AND EQUIPMENT
Depreciation	$ 0.4	$ 0.3

ACCRUED EXPENSES (Details)

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
ACCRUED EXPENSES
Clinical related	$ 12,869	$ 15,661
Accrued payroll and employee related expenses	7,902	9,032
Commercial manufacturing facility related	8,153	4,342
Manufacturing related	4,169	3,266
Legal and related services	963	1,061
Accrued other	1,718	1,712
Accrued expenses	$ 35,774	$ 35,074

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 08, 2021	Jun. 30, 2020	Oct. 31, 2018	Jan. 31, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jun. 10, 2019	Jun. 09, 2019
Common Stock
Proceeds from the issuance of common stock, net					$ 42,885
Common stock, par or stated value per share					$ 0.000041666		$ 0.000041666	$ 0.000041666
Common stock, shares authorized					300,000,000		300,000,000	300,000,000	150,000,000
Common Stock
Common Stock
Common stock issued, net of offering costs (in shares)					1,278,243
Common Stock | Issuance Of Common Stock Upon Conversion Of Preferred Stock
Common Stock
Conversion of stock, shares issued					738,961
IPO
Common Stock
Common stock issued, net of offering costs (in shares)		16,935,484	25,300,000	15,000,000
Share price (in dollars per share)		$ 31	$ 9.97	$ 11.50
Proceeds from the issuance of common stock, net		$ 567,000	$ 236,700	$ 162,000
IPO | Underwriter
Common Stock
Common stock issued, net of offering costs (in shares)		2,540,322	3,300,000	1,956,521
Proceeds from the issuance of common stock		$ 603,700	$ 252,200	$ 172,500
At the Market Offering Program [Member]
Common Stock
Common stock issued, net of offering costs (in shares)					1,278,243
Proceeds from the issuance of common stock, net					$ 42,900
Common stock, par or stated value per share	$ 0.000041666
Maximum amount of shares to be issued	$ 350,000
Maximum percentage of commission	3.00%
Series A Convertible Preferred Stock
Common Stock
Preferred stock, shares authorized					17,000
Sale of stock, price per share					$ 2
Preferred stock, par or stated value per share					$ 1,000
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
Conversion of stock, shares issued					97,000		97,000
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
Conversion of stock, shares issued					1
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, par or stated value per share					$ 4.75
Blank check
Common Stock
Preferred stock, shares authorized					50,000,000
Weighted average | At the Market Offering Program [Member]
Common Stock
Share price (in dollars per share)					$ 34.67

STOCK BASED COMPENSATION (Detai

STOCK BASED COMPENSATION (Details) - USD ($) $ / shares in Units, $ in Millions

Jun. 01, 2016

Jul. 31, 2013

Aug. 31, 2013

Mar. 31, 2021

Mar. 31, 2020

Dec. 31, 2020

Jun. 08, 2020

Jun. 07, 2020

Apr. 22, 2018

Aug. 16, 2016

Apr. 10, 2015

Nov. 30, 2014

Aug. 20, 2014

Aug. 19, 2014

Oct. 14, 2011

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

Weighted average grant date fair value, options granted

$ 26.42

$ 15.67

2011 Equity Incentive Plan

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

Maximum award per person per year (in shares)

50,000

300,000

Number of shares available

11,240

500,000

Shares authorized

180,000

1,700,000

1,900,000

1,700,000

180,000

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

85.00%

The 2018 Plan

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

Number of shares available

4,281,126

Shares authorized

14,000,000

6,000,000

6,000,000

2020 ESPP

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

Common Stock, Capital Shares Reserved for Future Issuance

0

Stock-based compensation expense

$ 0.3

Unrecognized compensation cost

$ 0.2

Unrecognized compensation cost recognition period

2 months 9 days

2014 Equity Incentive Plan

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

Number of shares available

9,220

Shares authorized

4,000,000

2,350,000

2014 Equity Incentive Plan | Maximum

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

Shares authorized

9,000,000

Stock option

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

Stock-based compensation expense

$ 16.7

$ 9.3

Total unrecognized compensation expense

$ 148.4

Unrecognized compensation cost recognition period

2 years 2 months 1 day

Restricted stock units

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

Stock-based compensation expense

$ 0

$ 0.1

Vested

137,500

First Anniversary | Restricted stock units

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

Vested

137,500

Vesting period

36 months

Satisfaction Of Clinical Trial Milestones | Restricted stock units

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

Vested

275,000

Chief Executive Officer | Restricted stock units

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

Granted

550,000

Granted, Fair value

$ 5.87

STOCKHOLDERS' EQUITY - Stock Op

STOCKHOLDERS' EQUITY - Stock Options (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)$ / sharesshares
Number of Options
Outstanding, beginning balance | shares	12,615,638
Granted | shares	3,704,589
Exercised | shares	(423,178)
Expired/Forfeited | shares	(477,823)
Outstanding, ending balance | shares	15,419,226
Options exercisable, number | shares	7,388,773
Weighted Average Exercise Price
Outstanding, beginning balance | $ / shares	$ 18.08
Granted | $ / shares	45.40
Exercised | $ / shares	15.31
Expired/Forfeited | $ / shares	29.79
Outstanding, ending balance | $ / shares	24.35
Options exercisable, exercise price | $ / shares	$ 13.49
Weighted Average Remaining Contractual Life
Options outstanding, remaining term	7 years 11 months 23 days
Options exercisable, remaining term	6 years 7 months 6 days
Aggregate Intrinsic Value
Outstanding, end of period | $	$ 169,189
Exercisable | $	$ 134,955

STOCKHOLDERS' EQUITY - Stock-ba

STOCKHOLDERS' EQUITY - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Total stock-based compensation expenses	$ 16,941	$ 9,412
Research and development
Total stock-based compensation expenses	9,202	4,318
General and administrative
Total stock-based compensation expenses	$ 7,739	$ 5,094

STOCKHOLDERS' EQUITY - Stock-_2

STOCKHOLDERS' EQUITY - Stock-based compensation by instrument (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Total stock-based compensation expenses	$ 16,941	$ 9,412
Stock option
Total stock-based compensation expenses	16,660	9,345
Restricted stock units
Total stock-based compensation expenses		$ 67
2020 ESPP
Total stock-based compensation expenses	$ 281

STOCK BASED COMPENSATION - Expe

STOCK BASED COMPENSATION - Expense thru assumptions (Details)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term (years)	5 years 2 months 15 days	6 years 2 months 8 days
Expected volatility	70.35%	69.99%
Risk-free interest rate	0.36%	1.83%
Expected dividend yield	0.00%	0.00%

LICENSES AND AGREEMENTS (Detail

LICENSES AND AGREEMENTS (Details) $ in Thousands	Apr. 17, 2017USD ($)	Jun. 28, 2014USD ($)	Dec. 31, 2016	Nov. 30, 2016item	Aug. 31, 2016USD ($)	Jan. 31, 2015item	Aug. 31, 2011	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2018USD ($)
Research and development expenses								$ 55,949	$ 56,952
Strategic Alliance Agreement
Research and development expenses								20	200
Research Collaboration And Clinical Grant Agreement
Research and development expenses								200	200
Maximum | Strategic Alliance Agreement
Research and development arrangement, contract to perform for others, costs incurred, gross	$ 14,200
Novartis Pharma AG - License Agreement [Member]
Research and development expenses								0	10,000
Cooperative Research and Development Agreement
Agreement term					5 years		5 years
Research and development expenses					$ 500			500	500
Number Of Indications Under Agreement | item						4
Notification Period To Terminate Agreement					60 days
WuXi Apptech, Inc - Manufacturing and Services Agreement
Agreement term				3 years
Research and development expenses								3,400	6,700
Number Of Statements Of Work | item				2
Number Of Suites Under The Agreement | item				2
Moffitt License Agreement Two
Research and development expenses								20	20
Payments for upfront licensing fee										$ 100
Additional milestone payable								400
Moffitt License Agreement One
Agreement term		20 years
Research and development expenses								0	0
Payments for upfront licensing fee		$ 100
Research Collaboration And Clinical Grant Agreements With Moffitt
Agreement term			3 years
Cellectis S.A
Research and development expenses								$ 100	$ 100

LEGAL PROCEEDINGS (Details)

LEGAL PROCEEDINGS (Details)	May 12, 2020USD ($)	Jun. 03, 2017USD ($)shares	Apr. 08, 2016USD ($)	Nov. 30, 2012USD ($)	Jun. 30, 2012USD ($)	Mar. 31, 2021shares	Jul. 05, 2018item
Granted | shares						3,704,589
Common stock issued upon exercise of stock options (in shares) | shares						423,178
Solomon Capital LLC Litigation
Damages claimed			$ 500,000
Equity claim	$ 47,420
Proceeds from related party debt				$ 200,000	$ 100,000
Twenty Eleven Equity Incentive Plan
Common stock issued upon exercise of stock options (in shares) | shares						200,000
Steven Fischkoff
Loss contingency pending claims number | item							2
Granted | shares		150,000
Severance pay and retention bonus		$ 300,000
Minimum | Solomon Capital LLC Litigation
Estimate of possible loss			1,500,000
Commercial Paper | Solomon Capital LLC Litigation
Face amount			$ 200,000
Solomon Capital, LLC | Solomon Capital LLC Litigation
Debt instrument, convertible, number of equity instruments			1,110

LEASES - Additional information

LEASES - Additional information (Details)

Aug. 01, 2020USD ($)ft²

Jun. 19, 2019USD ($)ft²

May 28, 2019USD ($)ft²

Oct. 19, 2018USD ($)ft²

Jul. 31, 2017USD ($)

Sep. 30, 2016USD ($)ft²

Aug. 04, 2016USD ($)ft²

Dec. 31, 2014ft²

Mar. 31, 2021USD ($)

Mar. 31, 2020USD ($)

Jan. 31, 2021USD ($)

Oct. 31, 2020USD ($)

Jul. 31, 2020USD ($)

Apr. 30, 2020USD ($)

Jan. 31, 2020USD ($)

Jul. 31, 2019USD ($)

Jan. 31, 2019USD ($)

Feb. 03, 2021USD ($)ft²

Dec. 31, 2020USD ($)

Oct. 07, 2020

Jun. 30, 2020USD ($)ft²

Dec. 31, 2019USD ($)

May 02, 2019USD ($)ft²

Oct. 31, 2018ft²

Jul. 31, 2018USD ($)

Apr. 28, 2017USD ($)ft²

Apr. 30, 2015ft²

Term of contract in months

12 months

359 months

Monthly lease payments

$ 101,090,000

First year

4,775,000

Second year

4,423,000

Monthly lease payments

2,322,000

$ 2,197,000

Operating lease liabilities

52,999,000

$ 51,659,000

Operating lease right-of-use assets

55,131,000

$ 54,756,000

Philadelphia, Pennsylvania

Term of contract in months

12 months

Operating expenses

$ 6,500

Area of land | ft²

2,965

Facility leases

Monthly lease payments

96,850,000

First year

4,414,000

Second year

4,423,000

Operating lease liabilities

$ 48,826,000

Facility leases | Tampa, Florida

Term of contract in months

5 years

Option to extend

option to extend

Renewal term in months

5 years

Monthly lease payments

$ 34,500

$ 20,500

Rent expense

$ 20,000

Area of land | ft²

8,673

5,115

13,139

6,043

Facility leases | San Carlos, California

Additional space of lease | ft²

8,110

First year

$ 39,000

Second year

$ 40,000

Facility leases | New York

Operating expenses

$ 4,000

$ 4,000

$ 4,000

$ 4,000

$ 4,000

Rent expense

$ 4,000

Facility leases | Office Space | San Carlos, California

Monthly lease payments

$ 38,000

$ 26,000

Lease Expiration Term

30 months

54 months

Monthly lease payments

$ 59,000

Area of land | ft²

20,432

12,322

8,733

11,449

11,449

Basis spread on operating lease (as a percent)

3.00%

Facility leases | Office Space | New York

Monthly lease payments

$ 9,000

Operating Leases, Rent Expense, Minimum Rentals

$ 18,000

Rent expense

$ 7,000

Office lease for first year | Office Space | Philadelphia, Pennsylvania

Monthly lease payments

$ 2,000

Area of land | ft²

1,500

Office lease for next three years | Philadelphia, Pennsylvania

Basis spread on operating lease (as a percent)

2.50%

Office lease for next three years | Office Space | Philadelphia, Pennsylvania

Term of contract in months

3 years

Monthly lease payments

$ 11,063

Area of land | ft²

4,500

Commercial Manufacturing Facility Agreement

Term of contract in months

359 months

Option to extend

option to extend

Monthly lease payments

$ 320,000

Prior written notice period (in months)

18 months

Minimum annual increase in basis spread on variable rate (as a percent)

2.00%

Maximum annual increase in basis spread on variable rate (as a percent)

75.00%

Operating expenses

$ 72,000

Operating lease liabilities

41,300,000

Operating lease right-of-use assets

$ 45,700,000

Basis spread on operating lease (as a percent)

0.02%

Commercial Manufacturing Facility Agreement | Office Space

Area of land | ft²

136,000

Suite 100 and Suite 125 Amendment | Office Space | Minimum

Renewal term in months

1 month

Suite 100 and Suite 125 Amendment | Office Space | Maximum

Renewal term in months

6 months

Suite 100 and Suite 125 Amendment | Office Space | San Carlos, California

Monthly lease payments

$ 103,000

Area of land | ft²

20,432

Suite 150 Second Amendment | Office Space | San Carlos, California

Renewal term in months

6 months

Monthly lease payments

$ 44,000

Area of land | ft²

8,733

Suite 150 Second Amendment | Office Space | San Carlos, California | Minimum

Renewal term in months

1 month

New Headquarters Lease | Office Space | San Carlos, California

Term of contract in months

120 months

Renewal term in months

60 months

Monthly lease payments

$ 280,000

Area of land | ft²

49,918

Basis spread on operating lease (as a percent)

3.00%

LEASES - Company's right-of-use

LEASES - Company's right-of-use asset and lease liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
LEASES
Operating lease right-of-use assets	$ 55,131	$ 54,756
Operating lease liabilities
Current portion included in current liabilities	5,916	6,284
Long-term portion included in non-current liabilities	47,083	45,375
Total Operating lease liabilities	$ 52,999	$ 51,659

LEASES - components of lease ex

LEASES - components of lease expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
LEASES
Operating lease cost	$ 3,398	$ 1,636
Variable lease cost	710	1,371
Short-term lease cost	36	17
Total lease cost	4,144	3,024
Cash paid for amounts included in the measurement of lease liabilities included in Operating cashflows	2,322	2,197
Right-of-use assets obtained from entering new leases	618
Increase in right-of-use assets from lease modifications	$ 2,159	$ 479
Weighted-average remaining lease terms (years)	17 years 6 months 18 days	1 year 8 months 23 days
Weighted-average discount rates	7.40%	7.50%

LEASES - maturities of the Comp

LEASES - maturities of the Company's operating lease liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
2021	$ 8,105
2022	4,775
2023	4,423
2024	4,516
2025	4,372
Thereafter	74,899
Total lease payments	101,090
Less: Present value adjustment	(48,091)
Operating lease liabilities	52,999	$ 51,659
Facility leases
2021	4,226
2022	4,414
2023	4,423
2024	4,516
2025	4,372
Thereafter	74,899
Total lease payments	96,850
Less: Present value adjustment	(48,024)
Operating lease liabilities	48,826
CMO embedded leases
2021	3,879
2022	361
Total lease payments	4,240
Less: Present value adjustment	(67)
Operating lease liabilities	$ 4,173

LONG-TERM NOTE (Details)

LONG-TERM NOTE (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
Maturity date	6 months

RELATED PARTY TRANSACTIONS - Ad

RELATED PARTY TRANSACTIONS - Additional information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Sep. 14, 2017	Sep. 14, 2017	Mar. 31, 2021	Mar. 31, 2020
Granted			$ 45.40
Terms of award		The granted stock options vest in 12 quarterly installments (with 1/12th of the option shares having vested on the date of grant).
Stock-based compensation expense			$ 16,941	$ 9,412
Consulting Agreement
Stock-based compensation expense			$ 0	$ 100
Board of Directors Chairman
Term of consulting agreement (in years)	3 years
Shares authorized	150	150
Granted		$ 7.30
Vesting period	3 years

INCOME TAXES - (Details)

INCOME TAXES - (Details)	15 Months Ended
	Mar. 31, 2021
INCOME TAXES
Effective tax rate	0.00%