Inovio Pharmaceuticals (INO) 10-K 6 Mar 24 2023 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Mar. 01, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-14888
Entity Registrant Name	INOVIO PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0969592
Entity Address, Address Line One	660 W. Germantown Pike
Entity Address, Address Line Two	Suite 110
Entity Address, City or Town	Plymouth Meeting
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19462
City Area Code	267
Local Phone Number	440-4200
Title of 12(b) Security	COMMON STOCK, $0.001 PAR VALUE
Trading Symbol	INO
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 119.7
Entity Common Stock, Shares Outstanding		23,370,365
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive proxy statement to be filed with the Commission pursuant to Regulation 14A in connection with the registrant’s 2024 Annual Meeting of Stockholders (the “Proxy Statement’) are incorporated by reference into Part III of this Report. Such Proxy Statement will be filed with the Commission not later than 120 days after the conclusion of the registrant’s fiscal year ended December 31, 2023.
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001055726

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Location	San Diego, California
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)		Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents		$ 14,310,862	$ 46,329,359
Short-term investments		130,982,913	206,669,397
Prepaid expenses and other current assets		5,393,665	50,130,481
Prepaid expenses and other current assets from affiliated entities		20,432	375,227
Total current assets		153,113,100	315,242,680
Fixed assets, net		4,960,986	7,727,997
Investments in affiliated entity		2,780,287	2,007,142
Intangible assets, net		0	2,129,861
Goodwill		0	10,513,371
Operating lease right-of-use assets		9,491,735	10,228,207
Other assets		605,315	684,044
Total assets		170,951,423	348,533,302
Current liabilities:
Accrued clinical trial expenses		2,365,382	10,594,073
Operating lease liability		2,406,522	2,803,973
Grant funding liability		87,489	2,475,031
Grant funding liability from affiliated entities		21,918	87,673
Convertible senior notes		16,770,654	0
Total current liabilities		42,570,228	96,868,074
Convertible senior notes		0	16,614,840
Operating lease liability, net of current portion		11,032,066	12,655,586
Deferred tax liabilities		0	32,046
Total liabilities		53,602,294	126,170,546
Commitments and contingencies
Inovio Pharmaceuticals, Inc. stockholders’ equity:
Preferred stock—par value $0.001; Authorized shares: 10,000,000, issued and outstanding shares: 9 at December 31, 2023 and 2022		0	0
Common stock—par value $0.001; Authorized shares: 600,000,000 at December 31, 2023 and 2022, issued and outstanding: 22,793,075 at December 31, 2023 and 21,090,938 at December 31, 2022	[1]	22,792	21,090
Additional paid-in capital		1,740,954,074	1,710,888,191
Accumulated deficit		(1,622,965,136)	(1,487,847,784)
Accumulated other comprehensive loss		(662,601)	(698,741)
Total Inovio Pharmaceuticals, Inc. stockholders’ equity		117,349,129	222,362,756
Total liabilities and stockholders’ equity		170,951,423	348,533,302
Nonrelated Party
Current assets:
Accounts receivable		0	1,701,726
Current liabilities:
Accounts payable and accrued expenses		19,847,744	79,686,885
Related Party
Current assets:
Accounts receivable		2,405,228	10,036,490
Current liabilities:
Accounts payable and accrued expenses		$ 1,070,519	$ 1,220,439
[1] (1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical)		Dec. 31, 2023 $ / shares shares	Dec. 31, 2022 $ / shares shares
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)		10,000,000	10,000,000
Preferred stock, shares issued (in shares)		9	9
Preferred stock, shares outstanding (in shares)		9	9
Common stock, par value (in USD per share) | $ / shares	[1]	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	[1]	600,000,000	600,000,000
Common stock, shares issued (in shares)	[1]	22,793,075	21,090,938
Common stock, shares outstanding (in shares)	[1]	22,793,075	21,090,938
[1] (1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($)		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues [Abstract]
Revenue from collaborative arrangements and other contracts, including affiliated entity		$ 832,010	$ 10,262,268	$ 1,774,758
Operating expenses:
Research and development		86,676,563	187,650,503	249,240,324
General and administrative		47,582,104	90,185,285	53,752,353
Impairment of goodwill		10,513,371	0	0
Total operating expenses		144,772,038	277,835,788	302,992,677
Loss from operations		(143,940,028)	(267,573,520)	(301,217,919)
Other income (expense):
Interest income		8,133,290	4,782,030	3,363,080
Interest expense		(1,222,789)	(1,253,952)	(1,936,447)
Gain (loss) on investment in affiliated entity		773,145	(1,899,654)	(553,570)
Net unrealized gain (loss) on available-for-sale equity securities		5,850,626	(7,846,172)	(3,222,838)
Other (expense) income, net		(4,711,596)	(3,861,584)	343,371
Net loss before share in net loss of Geneos		(135,117,352)	(277,652,852)	(303,224,323)
Share in net loss of Geneos		0	(2,165,213)	(434,387)
Net loss		$ (135,117,352)	$ (279,818,065)	$ (303,658,710)
Net loss per share
Basic (in dollars per share)	[1]	$ (6.09)	$ (14.07)	$ (17.45)
Diluted (in dollars per share)	[1]	$ (6.09)	$ (14.07)	$ (17.45)
Weighted average number of common shares outstanding
Basic (in shares)	[1]	22,173,662	19,885,182	17,402,483
Diluted (in shares)	[1]	22,173,662	19,885,182	17,402,483
[1] (1) Share and per share amounts have been restated to reflect the 1-for-12 reverse stock split effected in January 2024 on a retroactive basis for all periods presented.

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical)	Jan. 24, 2024
Subsequent Event
Stock split, conversion ratio	0.083333

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (135,117,352)	$ (279,818,065)	$ (303,658,710)
Other comprehensive loss:
Foreign currency translation	(3,920)	(25,556)	(30,134)
Unrealized (loss) gain on short-term investments, net of tax	40,060	(390,949)	4,048
Comprehensive loss attributable to Inovio Pharmaceuticals, Inc.	$ (135,081,212)	$ (280,234,570)	$ (303,684,796)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($)		Total	Adjustment	Preferred stock	Common stock		Additional paid-in capital	Additional paid-in capital Adjustment	Accumulated deficit	Accumulated deficit Adjustment	Accumulated other comprehensive loss
Beginning balance (in shares) at Dec. 31, 2020				9	15,570,957	[1]
Beginning balance at Dec. 31, 2020		$ 461,140,758		$ 0	$ 15,571	[1]	$ 1,367,578,149		$ (906,196,812)		$ (256,150)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for cash, net of financing costs (in shares)	[1]				2,275,861
Issuance of common stock for cash, net of financing costs		209,441,410			$ 2,276	[1]	209,439,134
Conversion of preferred stock/senior notes to common stock (in shares)	[1]				84,120
Conversion of preferred stock/senior notes to common stock		4,377,892			$ 84	[1]	4,377,808
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares)	[1]				184,299
Exercise of stock options for cash and vesting of RSUs, net of tax payments		2,057,393			$ 184	[1]	2,057,209
Stock-based compensation		26,336,764					26,336,764
Net loss		(303,658,710)							(303,658,710)
Unrealized gain (loss) on short-term investments, net of tax		4,048									4,048
Foreign currency translation		(30,134)									(30,134)
Ending balance at Dec. 31, 2021		399,669,421	$ (1,468,216)	$ 0	$ 18,115	[1]	1,609,789,064	$ (3,294,019)	(1,209,855,522)	$ 1,825,803	(282,236)
Ending balance (in shares) at Dec. 31, 2021				9	18,115,237	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for cash, net of financing costs (in shares)	[1]				2,870,478
Issuance of common stock for cash, net of financing costs		82,955,311			$ 2,870	[1]	82,952,441
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares)	[1]				105,223
Exercise of stock options for cash and vesting of RSUs, net of tax payments		(1,114,609)			$ 105	[1]	(1,114,714)
Stock-based compensation		22,555,419					22,555,419
Net loss		(279,818,065)							(279,818,065)
Unrealized gain (loss) on short-term investments, net of tax		(390,949)									(390,949)
Foreign currency translation		(25,556)									(25,556)
Ending balance at Dec. 31, 2022		222,362,756		$ 0	$ 21,090	[1]	1,710,888,191		(1,487,847,784)		(698,741)
Ending balance (in shares) at Dec. 31, 2022				9	21,090,938	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for legal settlement (in shares)	[1]				760,083
Issuance of common stock for legal settlement		14,000,000			$ 760	[1]	13,999,240
Issuance of common stock for cash, net of financing costs (in shares)	[1]				875,305
Issuance of common stock for cash, net of financing costs		5,461,745			$ 875	[1]	5,460,870
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares)	[1]				66,749
Exercise of stock options for cash and vesting of RSUs, net of tax payments		(466,646)			$ 67	[1]	(466,713)
Stock-based compensation		11,072,486					11,072,486
Net loss		(135,117,352)							(135,117,352)
Unrealized gain (loss) on short-term investments, net of tax		40,060									40,060
Foreign currency translation		(3,920)									(3,920)
Ending balance at Dec. 31, 2023		$ 117,349,129		$ 0	$ 22,792	[1]	$ 1,740,954,074		$ (1,622,965,136)		$ (662,601)
Ending balance (in shares) at Dec. 31, 2023				9	22,793,075	[1]
[1] (1) All share amounts in this column, including appropriate reclassifications between common stock and additional paid-in capital, have been restated to reflect the 1-for-12 reverse stock split effected in January 2024 on a retroactive basis for all periods presented.

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical)	12 Months Ended
	Dec. 31, 2021
Statement of Stockholders' Equity [Abstract]
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2020-06

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (135,117,352)	$ (279,818,065)	$ (303,658,710)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,621,649	3,656,713	3,040,096
Amortization of intangible assets	145,417	496,494	520,415
Amortization of operating lease right-of-use assets	736,472	1,342,819	1,170,270
Impairment of goodwill	10,513,371	0	0
Impairment of intangible assets	1,984,444	0	0
Deferred taxes	(32,046)	0	0
Non-cash stock-based compensation	11,072,486	22,555,419	26,336,764
Non-cash interest on senior convertible notes	155,814	186,977	858,644
Amortization of (discounts) premiums on investments	(4,686,144)	(1,320,546)	1,633,286
Realized loss on sales of short-term investments	4,805,804	4,029,961	5,397
Gain on remeasurement of investment in Geneos	0	(165,215)	0
Net loss on disposal of fixed assets	317,997	1,074,830	0
(Gain) loss on equity investment in affiliated entity	(773,145)	1,899,654	553,570
Share of net loss in Geneos	0	2,165,213	434,387
Net unrealized (gain) loss on available-for-sale equity securities	(5,850,626)	7,846,172	3,222,838
Unrealized transaction (gain) loss on foreign-currency denominated debt	0	0	(176,927)
Changes in operating assets and liabilities:
Accounts receivable, including from affiliated entities	9,332,988	(3,706,172)	11,031,705
Prepaid expenses and other current assets, including from affiliated entities	39,020,611	(5,336,525)	(6,343,632)
Other assets	78,729	741,750	24,531,654
Accounts payable and accrued expenses, including due to affiliated entities	(45,989,061)	32,606,581	26,140,970
Accrued clinical trial expenses	(8,228,691)	267,807	375,921
Deferred revenue, including from affiliated entity	0	(85,989)	(39,853)
Operating lease right-of-use assets and liabilities, net	(2,020,971)	(2,603,956)	(2,329,394)
Grant funding liability, including from affiliated entity	(2,453,297)	(2,034,517)	(2,973,089)
Other liabilities	0	(14,826)	(42,837)
Net cash used in operating activities	(124,365,551)	(216,215,421)	(215,708,525)
Cash flows from investing activities:
Purchases of investments	(203,475,052)	(248,528,843)	(348,953,236)
Proceeds from sale or maturity of investments	284,932,562	361,083,850	174,839,758
Purchases of capital assets	(320,898)	(969,153)	(1,231,006)
Proceeds from sale of capital assets	6,219,263	0	0
Investment in Geneos	0	(1,999,998)	0
Net cash provided by (used in) investing activities	87,355,875	109,585,856	(175,344,484)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of issuance costs	5,461,745	82,955,311	209,441,410
Proceeds from stock option exercises	0	283,022	6,668,741
Taxes paid related to net share settlement of equity awards	(466,646)	(1,397,631)	(4,611,348)
Net cash provided by financing activities	4,995,099	81,840,702	211,498,803
Effect of exchange rate changes on cash and cash equivalents	(3,920)	(25,556)	(30,134)
Decrease in cash and cash equivalents	(32,018,497)	(24,814,419)	(179,584,340)
Cash and cash equivalents, beginning of period	46,329,359	71,143,778	250,728,118
Cash and cash equivalents, end of period	14,310,862	46,329,359	71,143,778
Supplemental disclosure:
Amounts accrued for purchases of fixed assets	0	108,181	204,815
Interest paid	1,066,975	1,066,975	1,077,803
Change in prepaid expenses and other current assets related to fixed assets	0	6,071,000	7,709,337
Issuance of common stock as part of litigation settlement	$ 14,000,000	$ 0	$ 0

The Company

The Company	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	The Company Inovio Pharmaceuticals, Inc. (the “Company” or “INOVIO”) is a clinical-stage biotechnology company focused on developing and commercializing DNA medicines to help treat and protect people from diseases associated with human papillomavirus (HPV), cancer, and infectious diseases. INOVIO's platform harnesses the power of in vivo protein production, featuring optimized design and delivery of DNA medicines that teach the body to manufacture its own disease-fighting tools. INOVIO uses proprietary technology to design DNA plasmids, which are small circular DNA molecules that work like software the body’s cells can download to produce specific proteins to target and fight disease. The Company's proprietary investigational CELLECTRA® delivery devices help its DNA medicines enter the body’s cells for optimal effect. INOVIO's lead candidate is INO-3107 for the treatment of recurrent respiratory papillomatosis (RRP), a rare and debilitating disease of the respiratory tract caused by HPV infection. In its completed Phase 1/2 clinical trial of INO-3107 for the treatment of HPV-6 and HPV-11-associated RRP, 81.3% of patients experienced a reduction in the number of surgical interventions in the year following administration of INO-3107, when compared with the year prior to treatment. In addition to its development efforts with INO-3107, INOVIO is actively developing or planning to develop DNA medicines for other indications, including HPV-related anal dysplasia and oropharyngeal squamous cell carcinoma (OPSCC); glioblastoma multiforme (GBM), a deadly form of brain cancer; and a potential vaccine booster to protect against the Ebola virus. The Company was previously conducting clinical trials of a DNA medicine candidate for the treatment of HPV-related cervical high-grade squamous intraepithelial lesions (HSIL) but announced in August 2023 that it was ceasing development for this indication in the United States. However, its collaborator ApolloBio Corporation continues to conduct a Phase 3 clinical trial of this candidate in China and plans to seek regulatory approval for and potentially commercialize the candidate in that jurisdiction. The Company's partners and collaborators include Advaccine Biopharmaceuticals Suzhou Co, ApolloBio Corporation, AstraZeneca, The Bill & Melinda Gates Foundation (Gates), Coalition for Epidemic Preparedness Innovations (CEPI), Coherus Biosciences, Defense Advanced Research Projects Agency (DARPA), The U.S. Department of Defense (DoD), HIV Vaccines Trial Network, International Vaccine Institute (IVI), Kaneka Eurogentec, National Cancer Institute (NCI), National Institutes of Health (NIH), National Institute of Allergy and Infectious Diseases (NIAID), Plumbline Life Sciences, Regeneron Pharmaceuticals, Richter-Helm BioLogics, Thermo Fisher Scientific, the University of Pennsylvania, the Walter Reed Army Institute of Research, and The Wistar Institute. INOVIO was incorporated in Delaware in 2001 and has its principal executive offices in Plymouth Meeting, Pennsylvania.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Liquidity The Company incurred a net loss of $135.1 million for the year ended December 31, 2023. The Company had working capital of $110.5 million and an accumulated deficit of $1.6 billion as of December 31, 2023. The Company has incurred losses in each year since its inception and expects to continue to incur significant expenses and operating losses for the foreseeable future in connection with the research and preclinical and clinical development of its product candidates. The Company’s cash, cash equivalents and short-term investments of $145.3 million as of December 31, 2023 are sufficient to support the Company's operations for a period of at least 12 months from the date it is issuing these financial statements. In order to continue to fund future research and development activities, the Company will need to seek additional capital. This may occur through strategic alliance and licensing arrangements, grant agreements and/or future public or private debt or equity financings, including under At-the-Market Equity Offering Sales Agreements (“Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $5.5 million, $83.0 million and $47.7 million from equity offerings under Sales Agreements during the years ending December 31, 2023, 2022 and 2021, respectively, and $162.1 million from a January 2021 underwritten public offering of common stock. However, sufficient funding may not be available in the future, or if available, may be on terms that significantly dilute or otherwise adversely affect the rights of existing stockholders. If adequate funds are not available, the Company may need to delay, reduce the scope of or put on hold one or more of its clinical and/or preclinical programs. The Company is and, from time to time, may in the future be subject to various legal proceedings and claims arising in the ordinary course of business. The Company assesses contingencies to determine the degree of probability and range of possible loss for potential accrual in its consolidated financial statements. An estimated loss contingency is accrued in the consolidated financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Legal proceedings, including litigation, government investigations and enforcement actions, could result in material costs, occupy significant management resources and entail civil and criminal penalties, even if the Company ultimately prevails. Any of the foregoing consequences could result in serious harm to the Company’s business, results of operations and financial condition. Reverse Stock Split On January 24, 2024, the Company filed with the Secretary of State of the State of Delaware a certificate of amendment to its certificate of incorporation, as previously amended, to effect a 1-for-12 reverse stock split of our common stock (the “Reverse Stock Split”). As a result of the Reverse Stock Split, every 12 issued and outstanding shares of the Company's common stock were automatically combined into one issued and outstanding share of common stock. The reverse stock split was reflected on the Nasdaq Capital Market beginning with the opening of trading on January 25, 2024. Accordingly, an amount equal to the par value of the decreased shares resulting from the reverse stock split was reclassified from "Additional paid-in capital" to "Common stock" on the balance sheet and statement of changes in stockholders’ equity. Any fractional post-split shares as a result of the reverse stock split were eliminated by the payment of cash for the value of such fractional share. As a result of the Reverse Stock Split, proportionate adjustments were made to the number of shares underlying, and the exercise or conversion prices of, the Company's outstanding stock options and outstanding shares of Series C Cumulative Convertible Preferred Stock and to the number of shares of common stock issuable under the Company's equity incentive plans. The reverse stock split did not change the par value of the Company's common stock or the authorized number of shares of the Company's common stock. All share amounts and per share amounts disclosed in this Annual Report on Form 10-K have been restated to reflect the reverse stock split on a retroactive basis for all periods presented. Consolidation The consolidated financial statements include the accounts of Inovio Pharmaceuticals, Inc. and its wholly-owned subsidiary Inovio Asia LLC. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one segment operating primarily within the United States. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and short-term investments. The Company limits its exposure to credit loss by placing its cash and investments with high credit quality financial institutions. Additionally, the Company has established guidelines regarding diversification of its investments and their maturities which are designed to maintain principal and maximize liquidity. The Company has contracts with certain of its customers that have represented more than 10% of the Company's total revenues, as discussed in Note 3. Fair Value Measurements The guidance regarding fair value measurements establishes a three-tier fair value hierarchy which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets that are accessible at the measurement date; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. The Company’s financial instruments include cash equivalents, short-term investments, investments in affiliated entity, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses, and convertible senior notes. The carrying amounts of cash equivalents, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses approximate the related fair values due to the short-term maturities of these instruments. Short-term investments are recorded at fair value on a recurring basis, based on current market valuations. The Company carries convertible senior notes at face value less unamortized debt discount and issuance costs on its consolidated balance sheet, and it presents the fair value of such convertible notes for disclosure purposes only. Cash and Cash Equivalents Cash equivalents are considered by the Company to be highly liquid investments purchased with original maturities of three months or less from the date of purchase. Cash and cash equivalents included certain mutual funds and U.S. treasury securities at December 31, 2023 and 2022. Short-term Investments The Company defines investments as income-yielding securities that can be readily converted into cash or equity investments classified as available-for-sale. Investments included mutual funds, U.S. treasury securities, certificates of deposit, U.S. agency mortgage-backed securities and an equity investment in the Company’s affiliated entity, PLS, at December 31, 2023 and 2022. Short-term investments are recorded at fair value, based on current market valuations. Unrealized gains and losses on the Company's short-term debt investments are excluded from earnings and reported as a separate component of other comprehensive loss until realized. Realized gains and losses and unrealized gains and losses on available-for-sale equity securities are included in non-operating other income (expense) on the consolidated statements of operations and are derived using the specific identification method for determining the cost of the securities sold. Accounts Receivable Accounts receivable are recorded at invoiced amounts and do not bear interest. The Company performs ongoing credit evaluations of its customers’ financial condition. Credit is extended to customers as deemed necessary and generally does not require collateral. Management believes that the risk of loss is significantly reduced due to the quality and financial position of the Company's customers. There was no allowance for doubtful accounts for potential credit losses as of December 31, 2023 and 2022. Fixed Assets Fixed assets include property and equipment and leasehold improvements. Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful life of the assets, generally three The Company evaluates the carrying value of long-lived assets, which includes fixed assets and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amounts of the asset may not be fully recoverable. No impairment losses have been recognized related to long-lived assets for the year ended December 31, 2023 and 2022. Goodwill and Intangible Assets Goodwill represents the excess of acquisition cost over the fair value of the net assets of acquired businesses. Goodwill is reviewed for impairment at least annually, or more frequently if an event occurs indicating the potential for impairment. The Company evaluates intangible assets for impairment whenever events or changes in circumstances indicate the carrying amounts of the assets may not be recoverable. During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is likely that the fair value of its reporting unit is less than its carrying amount, including goodwill. The qualitative factors include, but are not limited to, macroeconomic conditions, industry and market considerations, and the overall financial performance of the Company. If, after assessing the totality of these qualitative factors, the Company determines that it is not likely that the fair value of its reporting unit is less than its carrying amount, then no additional assessment is deemed necessary. Otherwise, the Company will proceed to perform the impairment test in which the fair value of the reporting unit is compared with its carrying amount, and an impairment charge will be recorded for the amount by which the carrying amount exceeds the reporting unit's fair value, if any. Calculating the fair value of a reporting unit, an asset group and an individual asset involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates, future economic and market conditions, and the determination of appropriate market comparables. Changes in these factors and assumptions used can materially affect the amount of impairment loss recognized in the period the asset was considered impaired. During 2023, the Company experienced a decline in its market capitalization as a result of a sustained decrease in the Company’s stock price. This sustained decrease was considered to represent a triggering event requiring management to perform a quantitative goodwill impairment test as of September 30, 2023. The Company first tested its long-lived assets for impairment. The Company determined that all of its long-lived assets, which include property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value. Next, the Company determined that the fair value of its reporting unit was less than its carrying value and the Company recorded a loss on impairment of goodwill of $10.5 million. During 2023, the Company also recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology. Refer to Note 8 for further information regarding Goodwill and Intangible Assets. Income Taxes The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities along with net operating loss and tax credit carry forwards. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made. Valuation allowances against the Company’s deferred tax assets were $327.5 million and $299.1 million at December 31, 2023 and 2022, respectively. Changes in the valuation allowances, when they are recognized in the provision for income taxes, are included as a component of the estimated annual effective tax rate. Collaboration Agreements and Revenue Recognition The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") Topic 808: Collaborative Arrangements (“Topic 808”) based on whether they involve joint operating activities and whether both parties have active participation in the arrangement and are exposed to significant risks and rewards. To the extent that the arrangement falls within the scope of Topic 808 and the Company concludes that its collaboration partner is not a customer, the Company presents such payments as a reduction of research and development expense. If payments from the collaboration partner to the Company represent consideration from a customer, then the Company accounts for those payments within the scope of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (“Topic 606”). Grants The Company accounts for various grant agreements under the contributions guidance under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition , which is outside the scope of Topic 606, as the government agencies granting the Company funds are not receiving reciprocal value for their contributions. All contributions received from current grant agreements are recorded as a contra-research and development expense as opposed to revenue on the consolidated statement of operations. Foreign Currency Transactions The functional and presentation currency of the Company is the U.S. dollar. Transactions denominated in a currency other than the functional currency are recorded on the initial recognition at the exchange rate at the date of the transaction. After initial recognition, monetary assets and liabilities denominated in foreign currency are translated at the end of each reporting period into the functional currency at the exchange rate at that date. The cumulative translation adjustment is included in the accumulated other comprehensive income (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the consolidated statement of operations. Non-monetary assets and liabilities measured at cost are remeasured at the exchange rate at the date of the transaction. Variable Interest Entities (VIE) The Company evaluates its ownership, contractual and other interests in entities that are not wholly-owned to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company will continuously perform this assessment, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of a VIE. Equity Investments Under ASC Topic 321, Investments - Equity Securities, the Company must measure equity investments (except those accounted for under the equity method, those that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in the consolidated statement of operations. The Company can elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC Topic 820, Fair Value Measurement, to estimate fair value using the net asset value per share (or its equivalent). The Company's equity investments that do not have readily determinable fair values and do not qualify for the net asset value practical expedient for estimating fair value are measured at cost, less any impairments, plus or minus changes resulting from observable price changes in orderly transactions for identifiable or similar investments of the same issuer. Research and Development Expenses - Clinical Trial Accruals The Company's activities have largely consisted of research and development efforts related to developing its proprietary device technology and DNA medicine candidates. For clinical trial expenses, judgements used in estimating accruals rely on estimates of total costs incurred based on participant enrollment, completion of studies and other events. Accrued clinical trial costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. Historically, revisions have not resulted in material changes to research and development expense; however, a modification in the protocol of a clinical trial or cancellation of a trial could result in a charge to the Company's results of operations. Net Loss Per Share Basic net loss per share is computed by dividing the net loss for the year by the weighted average number of shares of common stock outstanding during the year. Diluted net loss per share is calculated in accordance with the treasury stock method for the outstanding stock options and restricted stock units ("RSUs") and reflects the potential dilution that would occur if securities or other contracts to issue common stock were exercised or converted to common stock. The dilutive impact of the outstanding Notes issued by the Company (discussed in Note 9) has been considered using the "if-converted" method. The calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the options or other securities and the presumed exercise of such securities are dilutive to net loss per share for the period, an adjustment to net loss used in the calculation is required to remove the change in fair value of such securities from the numerator for the period. Likewise, an adjustment to the denominator is required to reflect the related dilutive shares, if any. For the years ended December 31, 2023, 2022 and 2021, basic and diluted net loss per share are the same, as the assumed exercise or settlement of stock options, RSUs and the potentially dilutive shares issuable upon conversion of the Notes would have been anti-dilutive. The following table summarizes potential shares of common stock that were excluded from diluted net loss per share calculation because of their anti-dilutive effect: Year Ended December 31, 2023 2022 2021 Options to purchase common stock 1,128,864 1,018,095 874,082 Service-based restricted stock units 274,794 212,964 204,005 Performance-based restricted stock units — 9,328 55,279 Convertible preferred stock 275 275 275 Convertible notes 254,165 254,165 254,165 Total 1,658,098 1,494,827 1,387,806 Leases For its long-term operating leases, the Company recognized an operating lease right-of-use asset and an operating lease liability on its consolidated balance sheets. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The Company determines the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. Fixed rent expense for the Company's operating leases is recognized on a straight-line basis over the term of the lease and is included in operating expenses on the consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred. Stock-Based Compensation The Company incurs stock-based compensation expense related to RSUs and stock options. The fair value of restricted stock is determined by the closing price of the Company's common stock reported on the Nasdaq Global Select Market on the date of grant. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options, which have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of subjective assumptions, including the expected stock price volatility and expected option life. The Company amortizes the fair value of the awards on a straight-line basis over the requisite vesting period of the awards. Expected volatility is based on historical volatility. The expected life of options granted is based on historical expected life. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield is based on the fact that no dividends have been paid historically and none are currently expected to be paid in the foreseeable future. The Company recognizes forfeitures as they occur. The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below: Year Ended December 31, 2023 2022 2021 Risk-free interest rate 4.05% 2.05% 0.91% Expected volatility 100% 94% 93% Expected life in years 5.5 5.7 6 Dividend yield — — — The weighted average assumptions used in the Black-Scholes model for option grants to non-employees are presented below: Year Ended December 31, 2023 2022 2021 Risk-free interest rate 3.90% 1.96% 1.45% Expected volatility 89% 87% 87% Expected life in years 10 10 10 Dividend yield — — — Recent Accounting Pronouncements The recent accounting pronouncements below may have a significant effect on the Company's financial statements. Recent accounting pronouncements that are not anticipated to have an impact on or are unrelated to the Company's financial condition, results of operations, or related disclosures are not discussed. ASU No. 2023-07. In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures . The ASU expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the Chief Operating Decision Maker (CODM) and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The ASU also allows, in addition to the measure that is most consistent with U.S. GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, on a retrospective basis, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures. ASU No. 2023-09. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as information on income taxes paid. ASU 2023-09 is effective for public entities with annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

Revenue Recognition and Concent

Revenue Recognition and Concentration of Credit Risk	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue Recognition and Concentration of Credit Risk	Revenue Recognition and Concentration of Credit Risk During the years ended December 31, 2023, 2022 and 2021, the Company recognized revenue from various license and other agreements. The following table indicates the percentage of total revenues in excess of 10% with any single customer: Customer 2023 Revenue % of Total 2022 Revenue % of Total 2021 Revenue % of Total ApolloBio Corporation $ 245,056 29 % $ — — % $ — — % Plumbline Life Sciences, Inc. (affiliated entity) — — 33,596 — 245,310 14 U.S. Department of Defense — — 9,591,778 94 754,853 43 All other, including affiliated entities 586,954 71 636,894 6 774,595 43 Total revenue $ 832,010 100 % $ 10,262,268 100 % $ 1,774,758 100 % No revenue recognized during the year ended December 31, 2023 was in deferred revenue as of December 31, 2022. During the year ended December 31, 2022, the Company recognized revenue of $14,000 that was included in deferred revenue at December 31, 2021. Performance obligations are generally satisfied within 12 months of the initial contract date. As of December 31, 2023, the Company had no accounts receivable balance. As of December 31, 2022, all of the Company's accounts receivable was attributable to the CEPI MERS grant. There is minimal credit risk with the Company's customers based upon the short-term nature of the accounts receivable, collection history, their size and financial condition. Accordingly, the Company does not record an allowance for potential credit losses against its accounts receivable.

Collaborative Agreements

Collaborative Agreements	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative Agreements	Collaborative Agreements Advaccine Biopharmaceuticals Suzhou Co., Ltd. On December 31, 2020, the Company entered into a Collaboration and License Agreement with Advaccine Biopharmaceuticals Suzhou Co., Ltd. (“Advaccine”), which was amended and restated on June 7, 2021 (as amended and restated, the “Advaccine Agreement”). Under the terms of the Advaccine Agreement, the Company granted to Advaccine the exclusive right to develop, manufacture and commercialize the Company’s vaccine candidate INO-4800 within the territories of China, Taiwan, Hong Kong and Macau (referred to collectively as “Greater China”) and 33 additional countries in Asia. The June 2021 amendment related to a collaboration between the Company and Advaccine to jointly conduct a global Phase 3 segment of the Company’s clinical trial of INO-4800 that was planned. The parties were jointly participating in the trial and were to equally share the global development costs for the trial, including the Company’s manufacturing costs to supply INO-4800. Advaccine agreed to be fully responsible for conducting the trial in Greater China, including its costs and expenses incurred. In the fourth quarter of 2022, the Company discontinued its internally funded efforts to develop INO-4800 as a COVID-19 heterologous booster vaccine. Advaccine continues to develop INO-4800 with its own resources under the terms of the Advaccine Agreement. In connection with the June 2021 amendment, the Company determined that the global Phase 3 trial component of the agreement was a collaboration and not a contract with a customer and therefore accounted for the June 2021 amendment under ASC Topic 808. Reimbursements from Advaccine were recognized as contra-research and development expense on the consolidated statement of operations once earned and collectibility was assured. During the years ended December 31, 2023, 2022 and 2021, the Company received funding of $3.6 million, $1.2 million and $4.5 million, respectively, from Advaccine that was recorded as contra-research and development expense. ApolloBio Corporation On December 29, 2017, the Company entered into an Amended and Restated License and Collaboration Agreement (the "ApolloBio Agreement"), with ApolloBio Corporation ("ApolloBio"), which was amended on June 14, 2023. Under the terms of the ApolloBio Agreement, the Company granted to ApolloBio the exclusive right to develop and commercialize VGX-3100, its DNA immunotherapy product candidate designed to treat pre-cancers caused by HPV, within the agreed upon territories. The Company is entitled to receive up to an aggregate of $20.0 million, less required income, withholding or other taxes, upon the achievement of specified milestones related to the regulatory approval of VGX-3100 in accordance with the ApolloBio Agreement. In the event that VGX-3100 is approved for marketing, the Company will be entitled to receive royalty payments based on a tiered percentage of annual net sales, with such percentage being in the low- to mid-teens, subject to reduction in the event of generic competition in a particular territory. ApolloBio’s obligation to pay royalties will continue for 10 years after the first commercial sale in a particular territory or, if later, until the expiration of the last-to-expire patent covering the licensed products in the specified territory. During the year ended December 31, 2023, the Company received funding of $245,000 from the ApolloBio Agreement that was recorded as revenue. For the years ended December 31, 2022 and 2021, there were no significant reimbursable program costs under the ApolloBio Agreement. Coalition for Epidemic Preparedness Innovations The Company previously entered into agreements with CEPI, pursuant to which the Company intended to develop vaccine candidates against Lassa fever and MERS. As part of the arrangement between the parties, CEPI agreed to fund up to an aggregate of $56 million of costs over a five-year period for preclinical studies, as well as planned Phase 1 and Phase 2 clinical trials, to be conducted by the Company and collaborators, with funding from CEPI based on the achievement of identified milestones. In November 2022, the Company announced that it and CEPI would discontinue the development of these product candidates targeting Lassa fever and MERS, following the initial analysis of data from the studies conducted by the Company and funded by CEPI. During the years ended December 31, 2023, 2022 and 2021, the Company received funding of $1.8 million, $6.7 million and $10.0 million, respectively, related to these grants and recorded those payments as contra-research and development expense. As of December 31, 2023 and 2022, the Company had an accounts receivable balance of $0 and $1.7 million, respectively, on the consolidated balance sheet related to these CEPI grants. As of December 31, 2023, the Company had $2.2 million recorded as an accrued liability, and at December 31, 2022, had $0 recorded as deferred grant funding on the consolidated balance sheet related to these CEPI grants. In January 2020, CEPI awarded the Company a grant of up to $9.0 million to support preclinical and clinical development of INO-4800 through Phase 1 human testing in the United States. In April 2020, CEPI awarded the Company a grant of $6.9 million to work with the International Vaccine Institute ("IVI") and the Korea National Institute of Health ("KNIH") to conduct clinical trials of INO-4800 in South Korea, a grant of $5.0 million to accelerate development of the Company's next-generation intradermal electroporation device, known as CELLECTRA 3PSP, for the intradermal delivery of INO-4800, and a grant of $1.3 million to support large-scale manufacturing of INO-4800. During the years ended December 31, 2023, 2022 and 2021 , the Company received funding of $330,000, $1.1 million and $6.9 million, respectively, from CEPI related to these grants for INO-4800 and recorded such amounts as contra-research and development expense. As of December 31, 2023, the Company had $2.1 million recorded as an accrued liability, and at December 31, 2022, had $2.3 million recorded as deferred grant funding on the consolidated balance sheet related to the CEPI grants related to INO-4800. Bill & Melinda Gates Foundation In October 2018, Gates awarded and funded the Company a grant of $2.2 million to advance the development of dMAbs to address issues in infectious disease prevention and therapy. This technology has high relevance for the control of influenza and HIV. This next-generation approach to the delivery of monoclonal antibodies would make the technology accessible to low and middle-income countries. In August 2019, Gates funded an additional $1.1 million for the project. During the years ended December 31, 2023, 2022 and 2021, the Company recorded $70,000, $233,000 and $182,000, respectively, as contra-research and development expense related to the Gates dMAb grant. As of December 31, 2023 and 2022, the Company had $87,000 and $153,000, respectively, recorded as deferred grant funding on the consolidated balance sheet related to the grant. Department of Defense (DoD) In June 2020, the Company entered into an Other Transaction Authority for Prototype Agreement (the “OTA Agreement”) with the DoD to fund the Company’s efforts in developing the CELLECTRA ® 3PSP device and associated arrays to be used for delivery of INO-4800 against COVID-19. The total amount of funding provided to the Company under the OTA Agreement was $54.5 million. The Company determined that the OTA Agreement should be considered under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition , which is outside the scope of Topic 606, as the government agency granting the Company funds was not receiving reciprocal value for their contributions. The Company recorded contra-research and development expense on the consolidated statement of operations in the same period that the underlying expenses were incurred. During the years ended December 31, 2023, 2022 and 2021, the Company recorded $0, $6.1 million and $27.1 million, respectively, as contra-research and development expense related to the OTA agreement. Additionally, in June 2020, the Company was awarded a fixed-price contract (the “Procurement Contract”) from the DoD for the purchase of the Company’s intradermal CELLECTRA ® 2000 device and accessories. The total purchase price under the Procurement Contract was $16.8 million. The Company determined that the Procurement Contract fell under the scope of ASC Topic 606 as the contract was with a customer and the Company was able to satisfy its obligations under the arrangement. Performance obligations under the Procurement Contract consisted of the delivery of a specified number of CELLECTRA ® 2000 devices and accessories. The total transaction price was allocated to the individual performance obligations based on the determined standalone selling price for the devices and accessories. In 2021, the DoD announced that it would discontinue funding for the Phase 3 segment of the Company's clinical trials for INO-4800 and in January 2022, the total purchase price under the Procurement Contract was reduced to $10.7 million. During the year ended December 31, 2022, all performance obligations under the Procurement Contract were satisfied. During the years ended December 31, 2023, 2022 and 2021

Short-term Investments and Fair

Short-term Investments and Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Short-term Investments and Fair Value Measurements	Short-term Investments and Fair Value Measurements The following is a summary of available-for-sale securities as of December 31, 2023 and 2022: As of December 31, 2023 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 55,389,289 $ — $ (3,522,888) $ 51,866,401 U.S. treasury securities Less than 1 75,164,782 24,938 — 75,189,720 Certificates of deposit Less than 1 2,978,917 11,709 (300) 2,990,326 U.S. agency mortgage-backed securities * 1,340,439 — (403,973) 936,466 $ 134,873,427 $ 36,647 $ (3,927,161) $ 130,982,913 As of December 31, 2022 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 117,036,232 $ — $ (9,373,514) $ 107,662,718 U.S. treasury securities Less than 1 95,001,209 7,567 (44,266) 94,964,510 Certificates of deposit Less than 1 2,977,564 13,664 (320) 2,990,908 U.S. agency mortgage-backed securities * 1,435,592 — (384,331) 1,051,261 $ 216,450,597 $ 21,231 $ (9,802,431) $ 206,669,397 *No single maturity date. During the years ended December 31, 2023 and 2022, the Company recorded gross realized ga in on investments of $1,000 and $21,000, respectively, and gross realized loss on investments of $4.8 million and $4.1 million, respectively. During the years ended December 31, 2023 and 2022, the Company recorded net unrealized gain (loss) on available-for-sale equity securities of $5.9 million and $(7.8) million, respectively. No material balances were reclassified out of accumulated other comprehensive loss for the years ended December 31, 2023, 2022 and 2021. Interest and dividends on investments classified as available-for-sale are included in interest income in the consolidated statements of operations. As of December 31, 2023, the Company had 21 available-for-sale securities in a gross unrealized loss position, of which 20 with an aggregate total unrealized loss of $3.9 million were in such position for longer than 12 months. The Company periodically reviews its portfolio of available-for-sale debt securities to determine if any investment is impaired due to credit loss or other potential valuation concerns. For the debt securities where the fair value of the investment is less than the amortized cost basis, the Company has assessed at the individual security level for various quantitative factors including, but not limited to, the nature of the investments, changes in credit ratings, interest rate fluctuations, industry analyst reports, and the severity of impairment. Unrealized losses on available-for-sale debt securities as of December 31, 2023 were primarily due to changes in interest rates, and not due to increased credit risks associated with specific securities. Based on the credit quality of the available-for-sale debt securities that are in an unrealized loss position, and the Company’s estimates of future cash flows to be collected from those securities, the Company believes the unrealized losses are not credit losses. Accordingly, at December 31, 2023, the Company did not record an allowance for credit losses related to its available-for-sale debt securities. The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023: Fair Value Measurements at December 31, 2023 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 51,866,401 $ 51,866,401 $ — $ — U.S. treasury securities 75,189,720 75,189,720 — — Certificates of deposit 2,990,326 — 2,990,326 — U.S. agency mortgage-backed securities 936,466 — 936,466 — Total short-term investments 130,982,913 127,056,121 3,926,792 — Investment in affiliated entity 2,780,287 2,780,287 — — Total assets measured at fair value $ 133,763,200 $ 129,836,408 $ 3,926,792 $ — The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022: Fair Value Measurements at December 31, 2022 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 107,662,718 $ 107,662,718 $ — $ — U.S. treasury securities 94,964,510 94,964,510 — — Certificates of deposit 2,990,908 — 2,990,908 — U.S. agency mortgage-backed securities 1,051,261 — 1,051,261 — Total short-term investments 206,669,397 202,627,228 4,042,169 — Investments in affiliated entity 2,007,142 2,007,142 — — Total assets measured at fair value $ 208,676,539 $ 204,634,370 $ 4,042,169 $ — Level 1 assets at December 31, 2023 and 2022 consisted of mutual funds and U.S. treasury securities held by the Company that are valued at quoted market prices, as well as the Company’s investment in its affiliated entity, PLS. The Company accounts for its investment in 597,808 common shares of PLS based on the closing price of the shares on the Korea New Exchange Market on the applicable balance sheet date. Unrealized gains and losses on the Company's equity securities are reported in the consolidated statement of ope rations as unrealized gain or loss on available-for-sale equity securities or as a gain or loss on investment in affiliated entity. Level 2 assets at December 31, 2023 and 2022 consisted of certificates of deposit and U.S. agency mortgage-backed securities held by the Company that are initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing market observable data. The Company obtains the fair value of its Level 2 assets from a professional pricing service, which may use quoted market prices for identical or comparable instruments, or inputs other than quoted prices that are observable either directly or indirectly. The professional pricing service gathers quoted market prices and observable inputs from a variety of industry data providers. The valuation techniques used to measure the fair value of the Company's Level 2 financial instruments were derived from non-binding market consensus prices that are corroborated by observable market data, quoted market prices for similar instruments, or pricing models such as discounted cash flow techniques. The Company validates the quoted market prices provided by the primary pricing service by comparing the service's assessment of the fair values of the Company's investment portfolio balance against the fair values of the Company's investment portfolio balance obtained from an independent source.
Short-term Investments and Fair Value Measurements	Short-term Investments and Fair Value Measurements The following is a summary of available-for-sale securities as of December 31, 2023 and 2022: As of December 31, 2023 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 55,389,289 $ — $ (3,522,888) $ 51,866,401 U.S. treasury securities Less than 1 75,164,782 24,938 — 75,189,720 Certificates of deposit Less than 1 2,978,917 11,709 (300) 2,990,326 U.S. agency mortgage-backed securities * 1,340,439 — (403,973) 936,466 $ 134,873,427 $ 36,647 $ (3,927,161) $ 130,982,913 As of December 31, 2022 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 117,036,232 $ — $ (9,373,514) $ 107,662,718 U.S. treasury securities Less than 1 95,001,209 7,567 (44,266) 94,964,510 Certificates of deposit Less than 1 2,977,564 13,664 (320) 2,990,908 U.S. agency mortgage-backed securities * 1,435,592 — (384,331) 1,051,261 $ 216,450,597 $ 21,231 $ (9,802,431) $ 206,669,397 *No single maturity date. During the years ended December 31, 2023 and 2022, the Company recorded gross realized ga in on investments of $1,000 and $21,000, respectively, and gross realized loss on investments of $4.8 million and $4.1 million, respectively. During the years ended December 31, 2023 and 2022, the Company recorded net unrealized gain (loss) on available-for-sale equity securities of $5.9 million and $(7.8) million, respectively. No material balances were reclassified out of accumulated other comprehensive loss for the years ended December 31, 2023, 2022 and 2021. Interest and dividends on investments classified as available-for-sale are included in interest income in the consolidated statements of operations. As of December 31, 2023, the Company had 21 available-for-sale securities in a gross unrealized loss position, of which 20 with an aggregate total unrealized loss of $3.9 million were in such position for longer than 12 months. The Company periodically reviews its portfolio of available-for-sale debt securities to determine if any investment is impaired due to credit loss or other potential valuation concerns. For the debt securities where the fair value of the investment is less than the amortized cost basis, the Company has assessed at the individual security level for various quantitative factors including, but not limited to, the nature of the investments, changes in credit ratings, interest rate fluctuations, industry analyst reports, and the severity of impairment. Unrealized losses on available-for-sale debt securities as of December 31, 2023 were primarily due to changes in interest rates, and not due to increased credit risks associated with specific securities. Based on the credit quality of the available-for-sale debt securities that are in an unrealized loss position, and the Company’s estimates of future cash flows to be collected from those securities, the Company believes the unrealized losses are not credit losses. Accordingly, at December 31, 2023, the Company did not record an allowance for credit losses related to its available-for-sale debt securities. The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023: Fair Value Measurements at December 31, 2023 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 51,866,401 $ 51,866,401 $ — $ — U.S. treasury securities 75,189,720 75,189,720 — — Certificates of deposit 2,990,326 — 2,990,326 — U.S. agency mortgage-backed securities 936,466 — 936,466 — Total short-term investments 130,982,913 127,056,121 3,926,792 — Investment in affiliated entity 2,780,287 2,780,287 — — Total assets measured at fair value $ 133,763,200 $ 129,836,408 $ 3,926,792 $ — The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022: Fair Value Measurements at December 31, 2022 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 107,662,718 $ 107,662,718 $ — $ — U.S. treasury securities 94,964,510 94,964,510 — — Certificates of deposit 2,990,908 — 2,990,908 — U.S. agency mortgage-backed securities 1,051,261 — 1,051,261 — Total short-term investments 206,669,397 202,627,228 4,042,169 — Investments in affiliated entity 2,007,142 2,007,142 — — Total assets measured at fair value $ 208,676,539 $ 204,634,370 $ 4,042,169 $ — Level 1 assets at December 31, 2023 and 2022 consisted of mutual funds and U.S. treasury securities held by the Company that are valued at quoted market prices, as well as the Company’s investment in its affiliated entity, PLS. The Company accounts for its investment in 597,808 common shares of PLS based on the closing price of the shares on the Korea New Exchange Market on the applicable balance sheet date. Unrealized gains and losses on the Company's equity securities are reported in the consolidated statement of ope rations as unrealized gain or loss on available-for-sale equity securities or as a gain or loss on investment in affiliated entity. Level 2 assets at December 31, 2023 and 2022 consisted of certificates of deposit and U.S. agency mortgage-backed securities held by the Company that are initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing market observable data. The Company obtains the fair value of its Level 2 assets from a professional pricing service, which may use quoted market prices for identical or comparable instruments, or inputs other than quoted prices that are observable either directly or indirectly. The professional pricing service gathers quoted market prices and observable inputs from a variety of industry data providers. The valuation techniques used to measure the fair value of the Company's Level 2 financial instruments were derived from non-binding market consensus prices that are corroborated by observable market data, quoted market prices for similar instruments, or pricing models such as discounted cash flow techniques. The Company validates the quoted market prices provided by the primary pricing service by comparing the service's assessment of the fair values of the Company's investment portfolio balance against the fair values of the Company's investment portfolio balance obtained from an independent source.

Certain Balance Sheet Items

Certain Balance Sheet Items	12 Months Ended
	Dec. 31, 2023
Certain Balance Sheet Items [Abstract]
Certain Balance Sheet Items	Certain Balance Sheet Items Prepaid and other current assets at December 31, 2023 and 2022 consisted of the following: 2023 2022 Insurance recovery (a) $ — $ 30,000,000 Prepaid manufacturing expenses 1,486,638 1,401,028 Other prepaid expenses 3,907,027 18,729,453 $ 5,393,665 $ 50,130,481 Accounts payable and accrued expenses at December 31, 2023 and 2022 consisted of the following: 2023 2022 Trade accounts payable $ 3,577,826 $ 19,862,487 Accrued compensation 9,837,104 12,574,921 Accrued litigation settlement (a) — 44,000,000 Other accrued expenses (b) (c) 6,432,814 3,249,477 $ 19,847,744 $ 79,686,885 (a) In July 2022, the Company entered into a memorandum of understanding for the proposed settlement of class action securities litigation (see Note 11). The final judicial order for the settlement was issued in January 2023. The settlement consisted of $30.0 million in cash and $14.0 million in shares of the Company's common stock to settle all outstanding claims. As of December 31, 2022, the Company's insurance carriers had paid the cash component of the proposed settlement, which amounts were being held in escrow. The Company's insurance carriers paid $252,000 of other expenses on behalf of the Company, which amounts were offset against the insurers' cash commitment as part of the settlement. During the three months ended March 31, 2023, the cash component of the settlement was released from escrow and the Company issued 760,083 shares of common stock pursuant to the securities class action settlement. (b) In March 2023, the Company entered into a stipulation of settlement for the proposed settlement of shareholder derivative litigation (see Note 11). In June 2023, the court preliminarily approved the proposed settlement. As part of the settlement, in July 2023, the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. This amount was accrued within “Other accrued expenses” as of December 31, 2022. On October 12, 2023, the court entered an order and final judgment approving the Settlement, which was effective on November 13, 2023. (c) December 31, 2023 balance includes $4.3 million liability for unused grant funding.

Fixed Assets

Fixed Assets	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Fixed Assets	Fixed Assets Fixed assets at December 31, 2023 and 2022 consisted of the following: Cost Accumulated Net Book As of December 31, 2023 Leasehold improvements $ 15,917,596 $ (11,753,081) $ 4,164,515 Research and development equipment 3,538,698 (3,078,165) 460,533 Office furniture and fixtures 2,827,476 (2,816,577) 10,899 Computer equipment and other 3,529,129 (3,204,090) 325,039 $ 25,812,899 $ (20,851,913) $ 4,960,986 As of December 31, 2022 Leasehold improvements $ 15,803,108 $ (10,036,080) $ 5,767,028 Research and development equipment 5,300,104 (4,295,217) 1,004,887 Office furniture and fixtures 2,827,476 (2,803,800) 23,676 Computer equipment and other 5,360,712 (4,428,306) 932,406 $ 29,291,400 $ (21,563,403) $ 7,727,997

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets During the three months ended September 30, 2023, as a result of the sustained decline in the Company’s stock price and related market capitalization, and a general decline in equity values in the biotechnology industry, the Company performed an impairment assessment of its goodwill and long-lived assets. The Company operates as a single reporting unit based on its business and reporting structure. For goodwill, a quantitative impairment assessment was performed using a market approach, whereby the Company’s fair value of equity was compared to its carrying value. The fair value of equity was derived using both the market capitalization of the Company and an estimate of a reasonable range of values of a control premium applied to the Company’s implied business enterprise value. The control premium was estimated based upon control premiums observed in comparable market transactions. This represented a level 2 nonrecurring fair value measurement. Based on this analysis, the Company recognized a non-cash, pre-tax goodwill impairment charge of $10.5 million during the three months ended September 30, 2023. As a result, the goodwill was fully impaired as of September 30, 2023. Before completing the goodwill impairment assessment, the Company first tested its long-lived assets for impairment. The Company held no indefinite-lived intangible assets as of Sep tember 30, 2023. The Company determined that all of its long-lived assets, which included property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value. During the quarter ended June 30, 2023, the Company recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology. The following sets forth goodwill and intangible assets by major asset class: December 31, 2023 December 31, 2022 Weighted Average Useful Gross Accumulated Impairment Net Book Gross Accumulated Net Book Indefinite lived: Goodwill $ 10,513,371 $ — $ (10,513,371) $ — $ 10,513,371 $ — $ 10,513,371 Definite lived: Licenses 10 — — — — 1,323,761 (1,323,761) — Bioject — 5,100,000 (3,115,556) (1,984,444) — 5,100,000 (2,988,889) 2,111,111 Other (a) 18 4,050,000 (4,050,000) — — 4,050,000 (4,031,250) 18,750 Total intangible assets 11 9,150,000 (7,165,556) (1,984,444) — 10,473,761 (8,343,900) 2,129,861 Total goodwill and intangible assets $ 19,663,371 $ (7,165,556) $ (12,497,815) $ — $ 20,987,132 $ (8,343,900) $ 12,643,232 (a) Other intangible assets represent the estimated fair value of acquired intellectual property. Aggregate amortization expense related to intangible assets was $145,000, $496,000 and $520,000 for the years ended December 31, 2023, 2022 and 2021, respectively. There were no impairment or impairment indicators present and no losses were recorded during the years ended December 31, 2022 and 2021.

Convertible Debt

Convertible Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Convertible Debt	Convertible Debt Convertible Senior Notes On February 19, 2019 and March 1, 2019, the Company completed a private placement of $78.5 million aggregate principal amount of its 6.50% convertible senior notes due 2024 (the “Notes”). The Notes were sold in a private offering to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended. Net proceeds from the offering were $75.7 million. The Notes were senior unsecured obligations of the Company and accrued interest payable in cash semi-annually in arrears on March 1 and September 1 of each year at a rate of 6.50% per annum. The Notes matured on March 1, 2024 and the Company paid the then remaining $16.9 million obligation in full, including accrued interest. Initially, in accounting for the issuance of the Notes, the Company separated the Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar debt instruments, which do not have an associated convertible feature. The carrying amount of the equity component representing the conversion option for the Notes was $16.3 million and was recorded as a debt discount, which was being amortized to interest expense at an effective interest rate of 13.1%. In addition, the Company allocated $592,000 of debt issuance costs to the equity component and the remaining debt issuance costs of $2.2 million were allocated to the liability component, which were being amortized to interest expense under the effective interest rate method. On January 1, 2022, the Company adopted ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”). The ASU eliminated the cash conversion feature models in ASC 470-20, Debt with Conversion and Other Options, which required an issuer of certain convertible debt to separately account for embedded conversion features as a component of equity. Instead, the Company accounted for these securities as a single unit of account, unless the conversion feature met certain criteria. The Company adopted the new standard using the modified retrospective method and recorded a net reduction to accumulated deficit of $1.8 million, a decrease to additional paid-in capital of $3.3 million, and an increase to convertible senior notes of $1.5 million to reflect the impact of the accounting change. The Notes were subsequently accounted for as a single liability measured at amortized cost, as no other embedded features required bifurcation and recognition as derivatives. The balance of the Notes at December 31, 2023 was as follows: Principal amount $ 78,500,000 Principal amount converted into common shares (62,085,000) Unamortized debt issuance cost — Accrued interest 355,654 Net carrying amount $ 16,770,654

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock Shares Outstanding as of Shares Authorized Shares Issued 2023 2022 Series C Preferred Stock, par $0.001 1,091 1,091 9 9 The holder of a share or shares of Series C preferred stock has the right at any time, at such holder’s option, to convert all or any lesser portion of such holder’s shares of the preferred stock into fully paid and non-assessable shares of common stock. As of December 31, 2021, the conversion value w as $326.40 per share, such that the outstanding shares of Series C preferred stock were convertible into an aggregate of 275 shares of common stock. Issuances of Common Stock On November 9, 2021, the Company entered into an ATM Equity Offering SM Sales Agreement (the “2021 Sales Agreement”) with outside sales agents (collectively, the “Sales Agents”) for the offer and sale of its common stock for an aggregate offering price of up to $300.0 million. The 2021 Sales Agreement provides that the Sales Agents will be entitled to compensation in an amount equal to up to 3.0% of the gross sales proceeds of any common stock sold through the Sales Agents under the 2021 Sales Agreement. During the years ended December 31, 2023 and 2022, the Company sold 875,305 and 2,870,478 shares, respectively, of its common stock under the 2021 Sales Agreement. The sales were made at a weighted average price of $6.33 and $29.34 per share, respectively, resulting in aggregate net proceeds of $5.5 million and $83.0 million, respectively. As of December 31, 2023 there was $161.8 million of remaining capacity under the 2021 Sales Agreement. During the three months ended March 31, 2023, the Company issued 760,083 shares of common stock pursuant to the securities class action settlement, as described in Note 11. Stock Options and Restricted Stock Units The Company's Board of Directors adopted the 2023 Omnibus Incentive Plan (the “2023 Plan”) on March 24, 2023, pursuant to which the Company may grant stock options, restricted stock awards, RSUs and other stock-based awards or short-term cash incentive awards to employees, directors and consultants. The 2023 Plan was approved by stockholders on May 16, 2023. The aggregate number of shares of the Company’s common stock that may be issued under the 2023 Plan will not exceed the sum of 1,166,666 shares plus any shares that may return from time to time from the 2016 Omnibus Incentive Plan (as amended, the “2016 Plan”) as a result of expirations, terminations or forfeitures of awards outstanding under the 2016 Plan as of May 16, 2023. At December 31, 2023, the Company had 1,334,012 shares of common stock available for future grant under the 2023 Plan, 1,875 shares underlying outstanding but unvested RSUs and 3,150 shares underlying options outstanding to purchase common stock under the 2023 Plan. The awards granted and available for future grant under the 2023 Plan generally vest over three years and have a maximum contractual term of ten years. The 2023 Plan terminates by its terms on March 24, 2033. At December 31, 2023, the Company had 262,641 shares underlying outstanding but unvested RSU and options outstanding to purchase 961,499 shares of common stock under the 2016 Plan. The outstanding awards granted under the 2016 Plan generally vest over three years and have a maximum contractual term of ten years. Following adoption of the 2023 Plan, no further awards may be made under the 2016 Plan, but outstanding awards continue to be governed by their existing terms. On June 24, 2022, the Company's board of directors adopted a stock-based incentive plan (the "2022 Inducement Plan"), which provides for the discretionary grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, RSU awards, performance awards, and other awards to individuals as a material inducement to entering into employment with the Company. The aggregate number of shares of the Company’s common stock that may be issued under the 2022 Inducement Plan will not exceed 166,666 shares. At December 31, 2023 the Company had 125,575 shares of common stock available for future grant under the 2022 Inducement Plan, 10,278 shares underlying outstanding but unvested RSUs and options outstanding to purchase 27,759 shares of common stock under the 2022 Inducement Plan. The 2022 Inducement Plan can be terminated by the Company's board of directors at any time. The Amended and Restated 2007 Omnibus Incentive Plan (the "2007 Incentive Plan") was adopted on March 31, 2007 and terminated by its terms on March 31, 2017. At December 31, 2023, the Company had options outstanding to purchase 136,456 shares of common stock under the 2007 Incentive Plan. The awards granted under the 2007 Incentive Plan generally vest over three years and have a maximum contractual term of ten years. Total employee and director stock-based compensation expense recognized in the consolidated statements of operations for the years ended December 31, 2023, 2022 and 2021 was $10.4 million, $22.2 million and $25.0 million, respectively, of which $4.5 million, $8.8 million and $13.4 million was included in research and development expenses and $5.9 million, $13.4 million and $11.6 million was included in general and administrative expenses, respectively. At December 31, 2023 and 2022, there was $4.3 million and $10.5 million, respectively, of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of 1.3 years and 1.6 years, respectively. At December 31, 2023 and 2022, there was $3.5 million and $7.2 million, respectively, of total unrecognized compensation expense related to unvested RSUs, which is expected to be recognized over a weighted-average period of 1.5 years and 1.7 years, respectively. The fair value of stock options granted to non-employees was estimated using the Black-Scholes pricing model. Total stock-based compensation expense for stock options and RSUs granted to non-employees for the years ended December 31, 2023, 2022 and 2021 was $669,000, $1.3 million and $1.4 million, respectively. As of December 31, 2023, options to purchase 61,808 shares of common stock granted to non-employees remained outstanding. The following table summarizes total stock options outstanding at December 31, 2023: Options Outstanding Options Exercisable Exercise Price Shares Underlying Options Weighted-Average Weighted Shares Underlying Options Weighted Average $4.32-$18.00 283,472 9.2 $ 14.11 66,918 $ 14.45 $18.01-$39.00 264,108 7.3 $ 35.69 141,600 $ 34.99 $39.01-$52.00 156,505 4.5 $ 44.93 156,271 $ 44.93 $52.01-$90.00 129,681 4.2 $ 76.82 121,124 $ 77.75 $90.01-$130.00 136,716 4.2 $ 100.15 131,640 $ 100.00 $130.01-$233.28 158,382 5.4 $ 140.27 129,250 $ 141.78 1,128,864 6.4 $ 58.76 746,803 $ 72.11 At December 31, 2023, the aggregate intrinsic value of options outstanding was $2,000, the aggregate intrinsic value of options exercisable was $1,000, and the weighted average remaining contractual term of options exercisable was 5.5 years. At December 31, 2023, the aggregate intrinsic value of unvested RSUs was $1.7 million and the aggregate intrinsic value of RSUs which vested during the year ended December 31, 2023 was $1.3 million. At December 31, 2023, options to purchase 1,128,864 shares of common stock and 274,794 RSUs were expected to vest. Stock option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Number of Weighted-Average Balance, December 31, 2022 1,018,095 $ 75.32 Granted 339,019 14.23 Exercised — — Cancelled (228,250) 66.47 Balance, December 31, 2023 1,128,864 $ 58.76 Restricted stock unit activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Number of Balance, December 31, 2022 212,964 Granted 194,747 Vested (99,420) Cancelled (33,497) Balance, December 31, 2023 274,794 The weighted average exercise price per share was $38.86 for the 9,357 options which expired during the year ended December 31, 2023, $101.64 for the 6,437 options which expired during the year ended December 31, 2022 and $54.72 for the 583 options which expired during the year ended December 31, 2021. The weighted average grant date fair value per share was $11.19, $28.08 and $91.32 for options granted during the years ended December 31, 2023, 2022 and 2021, respectively. The weighted average grant date fair value was $10.34, $37.44 and $124.44 per share for RSUs granted during the years ended December 31, 2023, 2022 and 2021, respectively. No stock options were exercised during the year ended December 31, 2023. The Company received $283,000 and $6.7 million in proceeds from the exercise of stock options during the years ended December 31, 2022 and 2021, respectively. The aggregate intrinsic value of options exercised was $81,000 and $7.0 million during the years ended December 31, 2022 and 2021, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company leases approximately 56,600 square feet of office, laboratory, and manufacturing space in San Diego, California and 57,360 square feet of office space in Plymouth Meeting, Pennsylvania under various non-cancellable operating lease agreements with remaining lease terms as of December 31, 2023 of 3.4 years to 6.0 years, which represent the non-cancellable periods of the leases. The Company has excluded the extension options from its lease terms in the calculation of future lease payments as they are not reasonably certain to be exercised. The Company's lease payments consist primarily of fixed rental payments for the right to use the underlying leased assets over the lease terms as well as payments for common area maintenance and administrative services. The Company has received customary incentives from its landlords, such as reimbursements for tenant improvements and rent abatement periods, which effectively reduce the total lease payments owed for these leases. In November 2023, the Company amended one of its leases representing 31,207 square feet of office and laboratory space with a lease term expiring in November 2023, to extend the term to February 29, 2024. In November 2023, the Company entered into a lease agreement for research and development laboratory space in San Diego, California ("New San Diego Lease"). The total space under the New San Diego Lease is approximately 5,563 square feet. The term of the New San Diego Lease commenced on February 10, 2024 and the initial term is 4.3 years. The base rent adjusts periodically throughout the term of the New San Diego Lease. Rent payments under the New San Diego Lease will include base rent with an annual increase of approximately three percent, and additional monthly fees to cover the Company's share of certain facility expenses, including utilities, property taxes, insurance and maintenance. In addition, the Company has paid a security deposit of $33,000. The Company performed an evaluation of its contracts with customers and suppliers in accordance with ASC Topic 842 and determined that, except for the real estate leases described above and various copier leases, none of its other contracts contain a right-of-use asset. Operating lease right-of-use assets and liabilities on the consolidated balance sheet represents the present value of the remaining lease payments over the remaining lease terms. Payments for additional monthly fees to cover the Company's share of certain facility expenses are not included in operating lease right-of-use assets and liabilities. The Company uses its incremental borrowing rate to calculate the present value of its lease payments, as the implicit rates in the leases are not readily determinable. As of December 31, 2023, the maturities of the Company's operating lease liabilities were as follows: Year ending December 31, 2024 $ 3,247,000 2025 3,466,000 2026 3,555,000 2027 2,955,000 2028 2,310,000 Thereafter 2,132,000 Total remaining lease payments 17,665,000 Less: present value adjustment (4,226,000) Total operating lease liabilities 13,439,000 Less: current portion (2,407,000) Long-term operating lease liabilities $ 11,032,000 Weighted-average remaining lease term 5.3 years Weighted-average discount rate 8.9 % Lease costs included in operating expenses in the consolidated statements of operations for the years ended December 31, 2023, 2022 and 2021 were $3.5 million, $3.4 million and $3.4 million, respectively. Operating lease costs consisting of the fixed lease payments included in operating lease liabilities are recorded on a straight-line basis over the lease terms. Variable lease costs are recorded as incurred. In the third and fourth quarters of 2023, the Company entered into agreements to sublease a total of approximately 4,400 and 7,000 square feet, respectively, in its Plymouth Meeting headquarters, in each case with sublease terms through December 31, 2026. In the fourth quarter of 2019, the Company entered into two agreements to sublease a total of approximately 13,500 square feet in its Plymouth Meeting headquarters, with one sublease term through March 31, 2025 and the other month-to-month. In the normal course of business, the Company is a party to a variety of agreements pursuant to which it may be obligated to indemnify the other party. It is not possible to predict the maximum potential amount of future payments under these types of agreements due to the conditional nature of the Company's obligations and the unique facts and circumstances involved in each particular agreement. Historically, payments made by the Company under these types of agreements have not had a material effect on its business, consolidated results of operations or financial condition. Legal Proceedings Securities Litigation In March 2020, a purported shareholder class action complaint, McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim, was filed in the United States District Court for the Eastern District of Pennsylvania, naming the Company and its former President and Chief Executive Officer as defendants. The lawsuit alleged that the Company made materially false and misleading statements in violation of certain federal securities laws. The plaintiffs sought unspecified monetary damages on behalf of the putative class and an award of costs and expenses, including reasonable attorneys’ fees. The plaintiffs’ complaint was later amended to include certain of the Company’s other officers as defendants. After additional motions were filed in the case, in June 2022 the parties negotiated an agreement in principle to settle the shareholder class action complaint, which was approved by the court in January 2023. Under the settlement, the Company agreed to pay $30.0 million in cash and $14.0 million in shares of its common stock to settle all outstanding claims. The Company's insurance carriers paid the $30.0 million cash component of the settlement. During the three months ended March 31, 2023, the Company issued 760,083 shares of common stock pursuant to the securities class action settlement. Shareholder Derivative Litigation In April 2020, a purported shareholder derivative complaint, Behesti v. Kim, et al., was filed in the United States District Court for the Eastern District of Pennsylvania, naming eight current and former directors of the Company as defendants. The lawsuit asserted state and federal claims and was based on the same alleged misstatements as the shareholder class action complaint described above. The lawsuit accused the Company’s board of directors of failing to exercise reasonable and prudent supervision over the Company’s management, policies, practices, and internal controls. The plaintiff sought unspecified monetary damages on behalf of the Company as well as governance reforms. Between June 2020 and August 2020, additional shareholder derivative complaints were filed and later consolidated by the court. In March 2022, an additional shareholder derivative complaint was filed in the Delaware Court of Chancery, asserting substantially similar claims as those in the consolidated derivative action. In May 2022, the Delaware Court of Chancery entered a stay of the litigation. In March 2023, the parties submitted a joint status report to the Court of Chancery reporting that the parties agreed to a settlement in principle, which also provided for the resolution of the consolidated derivative action and certain stockholder demands. In April 2023, the plaintiffs in the consolidated derivative action filed a motion for preliminary approval of settlement with the United States District Court for the Eastern District of Pennsylvania. The proposed settlement provided for resolution of the consolidated derivative action, the derivative action pending in the Delaware Court of Chancery, and certain stockholder demands. In June 2023, the court entered an order preliminarily approving the proposed settlement of the derivative claims, in accordance with a Stipulation of Settlement. The Stipulation of Settlement contemplated that, following the settlement hearing and the final approval of the settlement by the court, the Company would implement certain corporate governance reforms described in the Stipulation of Settlement. The preliminary order also approved the form and manner of the notice of the Settlement. As part of the Settlement, in July 2023 the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. In October 2023, the court entered an order and final judgment approving the Settlement, which became effective in November 2023. The Company has implemented the corporate governance reforms in response to the provisions of the Stipulation of Settlement. VGXI Litigation In June 2020, the Company filed a complaint in the Court of Common Pleas of Montgomery County, Pennsylvania against VGXI, Inc. and GeneOne Life Science, Inc., or GeneOne, and together with VGXI, Inc. collectively referred to as VGXI, alleging that VGXI had materially breached the Company’s supply agreement with them. The complaint seeks declaratory judgments, specific performance of the agreement, injunctive relief, an accounting, damages, attorneys’ fees, interest, costs and other relief from VGXI. In June 2020, the Company filed a petition for preliminary injunction, which was denied. Following an appeal by the Company, in July 2020, VGXI filed counterclaims against the Company, alleging that the Company had breached the supply agreement, as well as misappropriation of trade secrets and unjust enrichment. The counterclaims seek injunctive relief, damages, attorneys’ fees, interest, costs and other relief from the Company. VGXI also filed a third-party complaint against Ology Bioservices, Inc., a contract manufacturing organization that the Company had engaged to provide services similar to those that were being provided by VGXI. The Company filed an answer to VGXI’s counterclaims, disputing the allegations and the claims raised in VGXI’s filing. In October 2020, the Company filed a notice of discontinuance of appeal with the Pennsylvania Superior Court. A trial date for the litigation has not been set. The Company intends to aggressively prosecute the claims set forth in its complaint against VGXI and to vigorously defend itself against VGXI’s counterclaims. GeneOne Litigation In December 2020, GeneOne filed a complaint in the Court of Common Pleas of Montgomery County, Pennsylvania against the Company, alleging that the Company had breached the CELLECTRA Device License Agreement, or the Agreement, between the Company and GeneOne. The Company terminated the Agreement in October 2020. The complaint asserts claims for breach of contract, declaratory judgment, unfair competition, and unjust enrichment. The complaint seeks injunctive relief, an accounting, damages, disgorgement of profits, attorneys’ fees, interest, and other relief from the Company. The Company filed preliminary objections to the complaint, which were overruled by the court. In September 2021, the Company filed an answer to the complaint, new matter, and counterclaims. The Company’s counterclaims allege that GeneOne breached the Agreement and assert claims for breach of contract and declaratory judgment. The counterclaims seek damages, interest, expenses, attorney’s fees, and costs. A trial date for this litigation has not been set. The Company intends to aggressively prosecute the claims set forth in its counterclaims against GeneOne and to vigorously defend itself against the claims in GeneOne’s complaint. Other Matters From time to time, the Company may be involved in disputes, including litigation, relating to claims arising out of operations in the normal course of its business. Any of these claims could subject the Company to costly legal expenses and, while the Company generally believes that it has adequate insurance to cover many different types of liabilities, its insurance carriers may deny coverage or its policy limits may be inadequate to fully satisfy any damage awards or settlements. If this were to happen, the payment of any such awards could have a material adverse effect on the Company's consolidated results of operations and financial position. Additionally, any such claims, whether or not successful, could damage the Company's reputation and business. Except as described above, the Company is not a party to any legal proceedings, the adverse outcome of which, in management’s opinion, individually or in the aggregate, would be reasonably expected to have a material adverse effect on the Company’s consolidated results of operations or financial position.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes In accordance with the guidance pursuant to accounting for income taxes, a deferred tax asset or liability is determined based on the difference between the financial statement and tax basis of assets and liabilities as measured by the enacted tax rates which will be in effect when these differences reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax asset will be realized. The components of pretax loss from operations are as follows: Year Ended December 31, 2023 2022 2021 U.S. Domestic $ (134,979,579) $ (277,440,803) $ (302,614,003) Foreign (137,772) (211,249) (610,320) Pretax loss from operations $ (135,117,351) $ (277,652,052) $ (303,224,323) There was no provision for or benefit from income taxes for the years ended December 31, 2023, 2022 and 2021. The reconciliation of income taxes attributable to continuing operations computed at the statutory tax rates to income tax benefit, using a 21% statutory tax rate for December 31, 2023, 2022 and 2021, is as follows: Year Ended December 31, 2023 2022 2021 Benefit from income taxes at statutory rates $ (28,375,000) $ (58,307,000) $ (63,677,000) State income tax, net of federal benefit (3,922,000) (3,601,000) (3,447,000) Change in valuation allowance 28,394,000 61,065,000 77,424,000 Research and development tax credits (2,139,000) (7,534,000) (16,523,000) Stock-based compensation 2,099,000 2,913,000 483,000 Uncertain tax positions 861,000 2,291,000 6,509,000 Goodwill Impairment 1,962,000 — — Expired NOLs and credits 1,352,000 1,459,000 616,000 Limited NOLs and credits (997,000) (1,337,000) (542,000) Change in tax rates 365,000 (187,000) — Foreign tax rate differential (4,000) (8,000) (24,000) Other 404,000 3,246,000 (819,000) $ — $ — $ — Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2023 and 2022 are shown below: As of December 31, 2023 2022 Deferred tax assets: Capitalized research expense $ 50,143,000 $ 41,252,000 NOL carryforwards 235,624,000 212,768,000 Research and development and other tax credits 27,734,000 26,442,000 Deferred revenue 22,000 538,000 Stock-based compensation 3,683,000 3,945,000 Acquired intangibles 907,000 559,000 Investment in affiliated entity 1,406,000 1,569,000 Lease liability 2,822,000 3,247,000 Fixed assets 337,000 57,000 Other 6,808,000 11,062,000 329,486,000 301,439,000 Valuation allowance (327,493,000) (299,124,000) Total deferred tax assets 1,993,000 2,315,000 Deferred tax liabilities: Acquired intangibles — (199,000) Right of use asset (1,993,000) (2,148,000) Total deferred tax liabilities (1,993,000) (2,347,000) Net deferred tax liabilities $ — $ (32,000) As of December 31, 2023, the Company had federal, California and other state tax net operating loss (NOL) carryforwards of $1,013.3 million, $251.4 million and $102.6 million, respectively, net of the net operating losses that will expire due to IRC Section 382 limitations. The aggregate federal net operating losses generated in 2018 and after for the amount of $719.3 million will carryforward indefinitely and be available to offset up to 80% of future taxable income each year. The federal NOL carryforward began to expire in 2023, and the California and other state NOL carryforwards will begin and have begun to expire in 2028 and 2023, respectively, unless previously utilized. The Company also had Korean NOL carryforwards of $1.1 million as of December 31, 2023. The Korean NOLs are available to offset up to 60% of future taxable income and will begin to expire in 2035, unless previously utilized. In addition, as of December 31, 2023, the Company had federal and state research and development (R&D) tax credit carryforwards of $41.6 million and $6.1 million, respectively. The federal tax credit carryforwards will begin to expire in 2029. The California research tax credits do not expire. Based upon statute, federal and state losses and credits are expected to expire as follows (in millions): Expiration Date: Federal NOLs State NOLs Foreign NOLs Federal R&D State R&D 2024 $ 18.9 $ 9.1 $ — $ — $ — 2025 13.7 5.2 — — — 2026 12.2 7.1 — — — 2027 and thereafter 249.2 332.0 1.1 41.6 — Indefinite 719.3 0.6 — — 6.1 $ 1,013.3 $ 354.0 $ 1.1 $ 41.6 $ 6.1 Pursuant to Internal Revenue Code (IRC) Sections 382 and 383, annual use of the Company’s NOL and R&D credit carryforwards may be limited in the event that a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has completed an IRC Section 382/383 analysis regarding the limitation of NOL and R&D credit carryforwards as of December 31, 2023. As a result of the analysis, the Company estimates that approximately $7.3 million of tax benefits related to NOL and R&D carryforwards will expire unused. Accordingly, the related NOL and R&D credit carryforwards have been removed from deferred tax assets accompanied by a corresponding reduction of the valuation allowance. Due to the existence of the valuation allowance, limitations created by current and future ownership changes, if any, related to the Company's operations in the United States will not impact its effective tax rate. Any additional ownership changes, may further limit the ability to use the NOL and R&D carryforwards. The Tax Cuts and Jobs Act of 2017 subjects a U.S. stockholder to tax on Global Intangible Low-Taxed Income (GILTI) earned by certain foreign subsidiaries. The FASB Staff Q&A, Topic 740, No. 5, Accounting for Global Intangible Low-Taxed Income, states that an entity can make an accounting policy election to recognize deferred taxes for temporary basis differences expected to reverse as GILTI in future years or to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. The Company has elected to provide for the tax expense related to GILTI in the year the tax is incurred as a period expense only. For 2023, 2022 and 2021, the Company did not generate any GILTI due to losses earned by its foreign subsidiary. The following table summarizes the activity related to the Company's unrecognized tax benefits: Year ended December 31, 2023 2022 2021 Balance at beginning of the year $ 21,139,000 $ 18,819,000 $ 12,210,000 Increases related to current year tax positions 1,816,000 2,902,000 6,602,000 Increases (decreases) related to prior year tax positions (841,000) (582,000) 7,000 Balance at end of the year $ 22,114,000 $ 21,139,000 $ 18,819,000 The amount of unrecognized tax benefits that, if recognized and realized, would affect the effective tax rate was $20.5 million, $19.7 million and $17.4 million as of December 31, 2023, 2022 and 2021, respectively, subject to valuation allowances. The Company has not recorded any interest and penalties on the unrecognized tax positions as the Company has continued to generate net operating losses after accounting for the unrecognized tax benefits. The Company does not anticipate that the total amount of unrecognized tax benefits will significantly increase or decrease within twelve months of the reporting date. The Company and its subsidiaries are subject to U.S. federal income tax as well as income tax in multiple state and foreign jurisdictions. With few exceptions, the Company is no longer subject to United States federal income tax examinations for years before 2020 and state and local income tax examinations before 2019. However, to the extent allowed by law, the tax authorities may have the right to examine prior periods where net operating losses were generated and carried forward, and make adjustments up to the amount of the NOL carryforward amount. The Company is not to its knowledge currently under Internal Revenue Service (“IRS”), state, local or foreign tax examination.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
401(k) Plan	401(k) Plan The Company has adopted a 401(k) Profit Sharing Plan covering substantially all of its employees. The defined contribution plan allows the employees to contribute a percentage of their compensation each year. The Company currently matches 50% of its employees’ contributions, up to 6% of their annual compensation. The Company’s contributions are recorded as expense in the accompanying consolidated statements of operations and totaled $1.4 million, $1.8 million and $1.5 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Plumbline Life Sciences, Inc. T he Company owned 597,808 shares of common stock in PLS as of December 31, 2023 and 2022 , representing a 17.8% and 18.7% ownership interest, respectively. One of the Company's directors, Dr. David B. Weiner, acts as a consultant to PLS. Revenue recognized from PLS consists of milestone, license and patent fees. For the years ended December 31, 2023, 2022 and 2021, the Company recognized revenue from PLS of $0, $34,000 and $245,000, respectively. At December 31, 2023 and 2022, the Company had an accounts receivable balance of $0 and $59,000, respectively, related to PLS. The Wistar Institute The Company's director Dr. David B. Weiner is a director of the Vaccine Center of The Wistar Institute ("Wistar"). Dr. Weiner is also the Executive Vice President of Wistar. In March 2016, the Company entered into collaborative research agreements with Wistar for preventive and therapeutic DNA-based immunotherapy applications and products developed by Dr. Weiner and Wistar for the treatment of cancers and infectious diseases. Under the terms of the agreement, the Company reimbursed Wistar for all direct and indirect costs incurred in the conduct of the collaborative research, not to exceed $3.1 million during the five-year term of the agreement. In March 2021, upon expiration of the March 2016 agreements, the Company entered into new collaborative research agreements with Wistar with the same terms. The Company has the exclusive right to in-license new intellectual property developed under this agreement. In 2020, the Company received a $10.7 million sub-grant through Wistar, which was amended in 2021 to $13.6 million, for the preclinical development and translational studies of dMAbs as countermeasures for COVID-19, with funding extended through August 2024 . The sub-grant also includes an option for an additional $1.6 million in funding through September 2025. In December 2022, the Company received a $1.2 million sub-grant through Wistar with funding through November 2023, with an option for an additional $5.4 million in funding through November 2027. The Company will support the Wistar lead consortium in the research and development of synthetic DNA-launched nanoparticles (dLNPs) for vaccination against HIV infection. Deferred grant funding recognized from Wistar and recorded as contra-research and development expense is related to work performed by the Company on the research sub-contract agreements. For the years ended December 31, 2023 and 2022, the Company recorded $1.0 million and $8.7 million, respectively, as contra-research and development expense from Wistar. Research and development expenses recorded from Wistar relate primarily to the collaborative research agreements and sub-contract agreements related to Gates and CEPI (see Note 4). Research and development expenses recorded from Wistar for the years ended December 31, 2023, 2022 and 2021 were $1.8 million, $1.4 million and $2.9 million, respectively. At December 31, 2023 and 2022, the Company had an accounts receivable balance of $2.4 million and $9.9 million, respectively, and an accounts payable and accrued liability balance of $1.1 million and $1.2 million, respectively, related to Wistar. As of December 31, 2023 and 2022, the Company had a prepaid expense balance of $20,000 and $375,000, respectively, and recorded $22,000 and $88,000, respectively, as deferred grant funding on its consolidated balance sheet related to Wistar.

Geneos Therapeutics, Inc.

Geneos Therapeutics, Inc.	12 Months Ended
	Dec. 31, 2023
Noncontrolling Interest [Abstract]
Geneos Therapeutics, Inc.	Geneos Therapeutics, Inc. In 2016, the Company formed Geneos to develop and commercialize neoantigen-based personalized cancer therapies. Geneos was considered a variable interest entity (VIE) for which the Company was the primary beneficiary. The Company's Chief Scientific Officer Dr. Laurent Humeau is on the Board of Directors of Geneos. The Company's director Dr. David B. Weiner is the Chairman of the Scientific Advisory Board of Geneos. Following a series of financing transactions through June 2020, the Company less than a majority of the outstanding equity of Geneos on an as-converted to common stock basis, which triggered a VIE reconsideration, as the Company no longer held a controlling financial interest. Based on the Company’s assessment, Geneos continued to be a VIE as it did not have sufficient equity at risk to finance its activities without additional subordinated financial support. However, the Company was not the primary beneficiary of Geneos, as it did not have the power to direct the activities that most significantly impact Geneos’ economic performance. Accordingly, the Company deconsolidated its investment in Geneos in 2020. Following the deconsolidation, the Company accounts for its common stock investment in Geneos, in which the Company lacks control but does have the ability to exercise significant influence over operating and financial policies, using the equity method. Generally, the ability to exercise significant influence is presumed when the investor possesses more than 20% of the voting interests of the investee. This presumption may be overcome based on specific facts and circumstances that demonstrate that the ability to exercise significant influence is restricted. The Company's equity method investments are reviewed for indicators of impairment at each reporting period and are written down to fair value if there is evidence of a loss in value that is other-than-temporary. Any difference between the carrying amount of the Company’s investment and the amount of underlying equity in Geneos’ net assets is amortized into income or expense accordingly. There were no basis differences identified as of the deconsolidation date that would need to be amortized. Upon deconsolidation, the Company recorded its investment at fair value. The Company determined that its investment in Geneos did not have a readily determinable fair value and therefore elected the measurement alternative in ASC 321 to subsequently record the investment at cost, less any impairments, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments of the same issuer. When fair value becomes determinable, from observable price changes in orderly transactions, the Company’s investment is marked to fair value. There have been no observable price changes or impairments identified since the deconsolidation date. The Company’s share of net losses of Geneos for the three months ended March 31, 2021 was $1.5 million; however, only $434,000 was recorded, reducing the Company's total investment in Geneos to $0. Of the total amount, $819,000 was allocated to the equity method investment, reducing the balance to $0 as of March 31, 2021. The remaining $4.2 million loss was allocated to the Company’s Series A and Series A-1 preferred stock investment in Geneos, on a ratable basis, reducing the balance to $0 as of March 31, 2021. In February 2021, Geneos completed a second closing of its Series A-1 preferred stock financing, in which the Company did not participate. Following this transaction, the Company held approximately 35% of the outstanding equity, on an as-converted to common stock basis. In March 2022, Geneos completed the closing of a Series A-2 preferred stock financing. The Company invested $2.0 million in the Series A-2 preferred stock financing, which was led by outside investors. The closing date of this transaction was determined to be a VIE reconsideration event; based on the Company’s assessment, Geneos continued to be a VIE as it did not have sufficient equity at risk to finance its activities without additional subordinated financial support. The Company continued to not be the primary beneficiary of Geneos, as it did not have the power to direct the activities that most significantly impact Geneos’s economic performance and should not consolidate Geneos. Following this transaction, the Company held approximately 28% of the outstanding equity, on an as-converted to common stock basis. Accordingly, the Company continued to account for its common stock investment in Geneos as an equity method investment under ASC 323 and its preferred stock investments as equity securities under ASC 321. The fair value of Geneos’s Series A-2 preferred stock was based on the per share price paid by third-party investors. The Company concluded that its Series A-2 preferred stock investment was a similar financial instrument as its Series A-1 preferred stock, and therefore remeasured the carrying value of the Series A-1 preferred stock investment at the Series A-2 preferred stock price, resulting in a gain on remeasurement of $165,000. The Company recorded its current and accumulated share of net losses of Geneos of $2.2 million, which was allocated to the Series A-1 and Series A-2 preferred stock investment in Geneos, thereby reducing the balance to $0 as of March 31, 2022. The Company has not made any further investment in Geneos subsequent to March 31, 2022. The Company will not reduce its investment below $0 and will not record its share of further net losses of Geneos as the Company has no obligation to fund Geneos. In 2023, Geneos completed the closing of its Series A-3 preferred stock financing, in which the Company did not participate. Following this transaction, the Company held approximately 23% of the outstanding equity of Geneos on an as-converted to common stock basis. The Company continues to exclusively license its SynCon ® immunotherapy and CELLECTRA ®

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 24, 2024, the Company implemented the 1-for-12 reverse stock split described in Note 2. All share information contained within this report, including the accompanying consolidated financial statements and footnotes, have been retroactively adjusted to reflect the effects of the reverse split. From January 1, 2024 through the date of these financial statements, the Company sold 543,620 shares of common stock under the 2021 Sales Agreement for net proceeds of $5.2 million. The sales were made at a weighted average price of $9.76 per share. On March 1, 2024, the Company's Convertible Senior Notes matured and the Company paid the $16.9 million obligation in full.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net loss	$ (135,117,352)	$ (279,818,065)	$ (303,658,710)

Insider Trading Arrangements

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

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation and Liquidity	Basis of Presentation and Liquidity The Company incurred a net loss of $135.1 million for the year ended December 31, 2023. The Company had working capital of $110.5 million and an accumulated deficit of $1.6 billion as of December 31, 2023. The Company has incurred losses in each year since its inception and expects to continue to incur significant expenses and operating losses for the foreseeable future in connection with the research and preclinical and clinical development of its product candidates. The Company’s cash, cash equivalents and short-term investments of $145.3 million as of December 31, 2023 are sufficient to support the Company's operations for a period of at least 12 months from the date it is issuing these financial statements. In order to continue to fund future research and development activities, the Company will need to seek additional capital. This may occur through strategic alliance and licensing arrangements, grant agreements and/or future public or private debt or equity financings, including under At-the-Market Equity Offering Sales Agreements (“Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $5.5 million, $83.0 million and $47.7 million from equity offerings under Sales Agreements during the years ending December 31, 2023, 2022 and 2021, respectively, and $162.1 million from a January 2021 underwritten public offering of common stock. However, sufficient funding may not be available in the future, or if available, may be on terms that significantly dilute or otherwise adversely affect the rights of existing stockholders. If adequate funds are not available, the Company may need to delay, reduce the scope of or put on hold one or more of its clinical and/or preclinical programs. The Company is and, from time to time, may in the future be subject to various legal proceedings and claims arising in the ordinary course of business. The Company assesses contingencies to determine the degree of probability and range of possible loss for potential accrual in its consolidated financial statements. An estimated loss contingency is accrued in the consolidated financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Legal proceedings, including litigation, government investigations and enforcement actions, could result in material costs,
Consolidation	Consolidation
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one segment operating primarily within the United States.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Concentration of Credit Risk	Concentration of Credit Risk
Fair value of Financial Instruments	Fair Value Measurements The guidance regarding fair value measurements establishes a three-tier fair value hierarchy which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets that are accessible at the measurement date; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. The Company’s financial instruments include cash equivalents, short-term investments, investments in affiliated entity, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses, and convertible senior notes. The carrying amounts of cash equivalents, accounts receivable, prepaid expenses and other assets, accounts payable and accrued expenses approximate the related fair values due to the short-term maturities of these instruments. Short-term investments are recorded at fair value on a recurring basis, based on current market valuations. The Company carries convertible senior notes at face value less unamortized debt discount and issuance costs on its consolidated balance sheet, and it presents the fair value of such convertible notes for disclosure purposes only.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents are considered by the Company to be highly liquid investments purchased with original maturities of three months or less from the date of purchase. Cash and cash equivalents included certain mutual funds and U.S. treasury securities at December 31, 2023 and 2022.
Short Term Investments	Short-term Investments The Company defines investments as income-yielding securities that can be readily converted into cash or equity investments classified as available-for-sale. Investments included mutual funds, U.S. treasury securities, certificates of deposit, U.S. agency mortgage-backed securities and an equity investment in the Company’s affiliated entity, PLS, at December 31, 2023 and 2022. Short-term investments are recorded at fair value, based on current market valuations. Unrealized gains and losses on the Company's short-term debt investments are excluded from earnings and reported as a separate component of other comprehensive loss until realized. Realized gains and losses and unrealized gains and losses on available-for-sale equity securities are included in non-operating other income (expense) on the
Accounts Receivable	Accounts Receivable
Fixed Assets	Fixed Assets Fixed assets include property and equipment and leasehold improvements. Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful life of the assets, generally three The Company evaluates the carrying value of long-lived assets, which includes fixed assets and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amounts of the asset may not be fully recoverable. No impairment losses have been recognized related to long-lived assets for the year ended December 31, 2023 and 2022.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of acquisition cost over the fair value of the net assets of acquired businesses. Goodwill is reviewed for impairment at least annually, or more frequently if an event occurs indicating the potential for impairment. The Company evaluates intangible assets for impairment whenever events or changes in circumstances indicate the carrying amounts of the assets may not be recoverable. During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is likely that the fair value of its reporting unit is less than its carrying amount, including goodwill. The qualitative factors include, but are not limited to, macroeconomic conditions, industry and market considerations, and the overall financial performance of the Company. If, after assessing the totality of these qualitative factors, the Company determines that it is not likely that the fair value of its reporting unit is less than its carrying amount, then no additional assessment is deemed necessary. Otherwise, the Company will proceed to perform the impairment test in which the fair value of the reporting unit is compared with its carrying amount, and an impairment charge will be recorded for the amount by which the carrying amount exceeds the reporting unit's fair value, if any. Calculating the fair value of a reporting unit, an asset group and an individual asset involves significant estimates and assumptions. These estimates and assumptions include, among others, projected future cash flows, risk-adjusted discount rates, future economic and market conditions, and the determination of appropriate market comparables. Changes in these factors and assumptions used can materially affect the amount of impairment loss recognized in the period the asset was considered impaired. During 2023, the Company experienced a decline in its market capitalization as a result of a sustained decrease in the Company’s stock price. This sustained decrease was considered to represent a triggering event requiring management to perform a quantitative goodwill impairment test as of September 30, 2023. The Company first tested its long-lived assets for impairment. The Company determined that all of its long-lived assets, which include property and equipment, leasehold improvements and right-of-use assets, represented one asset group for purposes of its long-lived asset impairment assessment. The Company concluded that the long-lived assets were not impaired, as their carrying values were not in excess of their fair value. Next, the Company determined that the fair value of its reporting unit was less than its carrying value and the Company recorded a loss on impairment of goodwill of $10.5 million. During 2023, the Company also recorded an impairment charge of $2.0 million to research and development expense for the remaining book value of intangible assets acquired in 2016 from Bioject Medical Technologies, as the Company had no plans to further develop or utilize this technology.
Income Taxes	Income Taxes The Company recognizes deferred tax assets and liabilities for temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities along with net operating loss and tax credit carry forwards. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made. Valuation allowances against the Company’s deferred tax assets were $327.5 million and $299.1 million at December 31, 2023 and 2022, respectively. Changes in the valuation allowances, when they are recognized in the provision for income taxes, are included as a component of the estimated annual effective tax rate.
Collaboration Agreements	Collaboration Agreements and Revenue Recognition
Revenue Recognition	Collaboration Agreements and Revenue Recognition
Grants	Grants The Company accounts for various grant agreements under the contributions guidance under Subtopic 958-605, Not-for-Profit Entities-Revenue Recognition
Foreign Currency Transactions	Foreign Currency Transactions The functional and presentation currency of the Company is the U.S. dollar. Transactions denominated in a currency other than the functional currency are recorded on the initial recognition at the exchange rate at the date of the transaction. After initial recognition, monetary assets and liabilities denominated in foreign currency are translated at the end of each reporting period into the functional currency at the exchange rate at that date. The cumulative translation adjustment is included in the accumulated other comprehensive income (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the consolidated statement of operations. Non-monetary assets and liabilities measured at cost are remeasured at the exchange rate at the date of the transaction.
Variable Interest Entities (VIE)	Variable Interest Entities (VIE) The Company evaluates its ownership, contractual and other interests in entities that are not wholly-owned to determine if these entities are VIEs, and, if so, whether the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE and therefore required to consolidate the VIE, the Company applies a qualitative approach that determines whether it has both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. The Company will continuously perform this assessment, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of a VIE.
Equity Method Investments	Equity Investments Under ASC Topic 321, Investments - Equity Securities, the Company must measure equity investments (except those accounted for under the equity method, those that result in consolidation of the investee and certain other investments) at fair value and recognize any changes in fair value in the consolidated statement of operations. The Company can elect a measurement alternative for equity investments that do not have readily determinable fair values and do not qualify for the practical expedient in ASC Topic 820, Fair Value Measurement,
Research and Development Expenses	Research and Development Expenses - Clinical Trial Accruals The Company's activities have largely consisted of research and development efforts related to developing its proprietary device technology and DNA medicine candidates. For clinical trial expenses, judgements used in estimating accruals rely on estimates of total costs incurred based on participant enrollment, completion of studies and other events. Accrued clinical trial costs are subject to revisions as trials progress. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. Historically, revisions have not resulted in material changes to research and development expense; however, a modification in the protocol of a clinical trial or cancellation of a trial could result in a charge to the Company's results of operations.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss for the year by the weighted average number of shares of common stock outstanding during the year. Diluted net loss per share is calculated in accordance with the treasury stock method for the outstanding stock options and restricted stock units ("RSUs") and reflects the potential dilution that would occur if securities or other contracts to issue common stock were exercised or converted to common stock. The dilutive impact of the outstanding Notes issued by the Company (discussed in Note 9) has been considered using the "if-converted" method. The calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the options or other securities and the presumed exercise of such securities are dilutive to net loss per share for the period, an adjustment to net loss used in the calculation is required to remove the change in fair value of such securities from the numerator for the period. Likewise, an adjustment to the denominator is required to reflect the related dilutive shares, if any.
Leases	Leases For its long-term operating leases, the Company recognized an operating lease right-of-use asset and an operating lease liability on its consolidated balance sheets. The lease liability is determined as the present value of future lease payments using an estimated rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. The Company determines the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. Fixed rent expense for the Company's operating leases is recognized on a straight-line basis over the term of the lease and is included in operating expenses on the consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred.
Stock-Based Compensation	Stock-Based Compensation The Company incurs stock-based compensation expense related to RSUs and stock options. The fair value of restricted stock is determined by the closing price of the Company's common stock reported on the Nasdaq Global Select Market on the date of grant. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model. The Black-Scholes option pricing model was developed for use in estimating the fair value of traded options, which have no vesting restrictions and are fully transferable. In addition, option valuation models require the input of subjective assumptions, including the expected stock price volatility and expected option life. The Company amortizes the fair value of the awards on a straight-line basis over the requisite vesting period of the awards. Expected volatility is based on historical volatility. The expected life of options granted is based on historical expected life. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant. The dividend yield is based on the fact that no dividends have been paid historically and none are currently expected to be paid in the foreseeable future.
Recent Accounting Pronouncements - Recently Adopted	Recent Accounting Pronouncements The recent accounting pronouncements below may have a significant effect on the Company's financial statements. Recent accounting pronouncements that are not anticipated to have an impact on or are unrelated to the Company's financial condition, results of operations, or related disclosures are not discussed. ASU No. 2023-07. In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures . The ASU expands public entities’ segment disclosures by requiring disclosure of significant segment expenses that are regularly reviewed by the Chief Operating Decision Maker (CODM) and included within each reported measure of segment profit or loss, an amount and description of its composition for other segment items, and interim disclosures of a reportable segment’s profit or loss and assets. The ASU also allows, in addition to the measure that is most consistent with U.S. GAAP, the disclosure of additional measures of segment profit or loss that are used by the CODM in assessing segment performance and deciding how to allocate resources. All disclosure requirements under ASU 2023-07 are also required for public entities with a single reportable segment. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, on a retrospective basis, with early adoption permitted. The Company is currently evaluating the impact of this standard on its consolidated financial statements and disclosures. ASU No. 2023-09. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as information on income taxes paid. ASU 2023-09 is effective for public entities with annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the impact of this guidance on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Common Shares That Were Excluded From The Diluted Net Loss Per Share Calculation Because of Their Anti-Dilutive Effect	The following table summarizes potential shares of common stock that were excluded from diluted net loss per share calculation because of their anti-dilutive effect: Year Ended December 31, 2023 2022 2021 Options to purchase common stock 1,128,864 1,018,095 874,082 Service-based restricted stock units 274,794 212,964 204,005 Performance-based restricted stock units — 9,328 55,279 Convertible preferred stock 275 275 275 Convertible notes 254,165 254,165 254,165 Total 1,658,098 1,494,827 1,387,806
Schedule of Assumptions Used To Estimate The Fair Value Of Stock Options	The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below: Year Ended December 31, 2023 2022 2021 Risk-free interest rate 4.05% 2.05% 0.91% Expected volatility 100% 94% 93% Expected life in years 5.5 5.7 6 Dividend yield — — — The weighted average assumptions used in the Black-Scholes model for option grants to non-employees are presented below: Year Ended December 31, 2023 2022 2021 Risk-free interest rate 3.90% 1.96% 1.45% Expected volatility 89% 87% 87% Expected life in years 10 10 10 Dividend yield — — —

Revenue Recognition and Conce_2

Revenue Recognition and Concentration of Credit Risk (Tables)	12 Months Ended
	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Schedule of Revenue From External Customers	The following table indicates the percentage of total revenues in excess of 10% with any single customer: Customer 2023 Revenue % of Total 2022 Revenue % of Total 2021 Revenue % of Total ApolloBio Corporation $ 245,056 29 % $ — — % $ — — % Plumbline Life Sciences, Inc. (affiliated entity) — — 33,596 — 245,310 14 U.S. Department of Defense — — 9,591,778 94 754,853 43 All other, including affiliated entities 586,954 71 636,894 6 774,595 43 Total revenue $ 832,010 100 % $ 10,262,268 100 % $ 1,774,758 100 %

Short-term Investments and Fa_2

Short-term Investments and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities	The following is a summary of available-for-sale securities as of December 31, 2023 and 2022: As of December 31, 2023 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 55,389,289 $ — $ (3,522,888) $ 51,866,401 U.S. treasury securities Less than 1 75,164,782 24,938 — 75,189,720 Certificates of deposit Less than 1 2,978,917 11,709 (300) 2,990,326 U.S. agency mortgage-backed securities * 1,340,439 — (403,973) 936,466 $ 134,873,427 $ 36,647 $ (3,927,161) $ 130,982,913 As of December 31, 2022 Contractual Cost Gross Unrealized Gross Unrealized Fair Market Value Mutual funds --- $ 117,036,232 $ — $ (9,373,514) $ 107,662,718 U.S. treasury securities Less than 1 95,001,209 7,567 (44,266) 94,964,510 Certificates of deposit Less than 1 2,977,564 13,664 (320) 2,990,908 U.S. agency mortgage-backed securities * 1,435,592 — (384,331) 1,051,261 $ 216,450,597 $ 21,231 $ (9,802,431) $ 206,669,397 *No single maturity date.
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2023: Fair Value Measurements at December 31, 2023 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 51,866,401 $ 51,866,401 $ — $ — U.S. treasury securities 75,189,720 75,189,720 — — Certificates of deposit 2,990,326 — 2,990,326 — U.S. agency mortgage-backed securities 936,466 — 936,466 — Total short-term investments 130,982,913 127,056,121 3,926,792 — Investment in affiliated entity 2,780,287 2,780,287 — — Total assets measured at fair value $ 133,763,200 $ 129,836,408 $ 3,926,792 $ — The following table presents the Company’s assets that were measured at fair value on a recurring basis, determined using the following inputs as of December 31, 2022: Fair Value Measurements at December 31, 2022 Total Quoted Prices Significant Significant Short-term investments Mutual funds $ 107,662,718 $ 107,662,718 $ — $ — U.S. treasury securities 94,964,510 94,964,510 — — Certificates of deposit 2,990,908 — 2,990,908 — U.S. agency mortgage-backed securities 1,051,261 — 1,051,261 — Total short-term investments 206,669,397 202,627,228 4,042,169 — Investments in affiliated entity 2,007,142 2,007,142 — — Total assets measured at fair value $ 208,676,539 $ 204,634,370 $ 4,042,169 $ —

Certain Balance Sheet Items (Ta

Certain Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2023
Certain Balance Sheet Items [Abstract]
Schedule of Prepaid Expenses And Other Current Assets	Prepaid and other current assets at December 31, 2023 and 2022 consisted of the following: 2023 2022 Insurance recovery (a) $ — $ 30,000,000 Prepaid manufacturing expenses 1,486,638 1,401,028 Other prepaid expenses 3,907,027 18,729,453 $ 5,393,665 $ 50,130,481
Schedule of Accounts Payable And Accrued Expenses	Accounts payable and accrued expenses at December 31, 2023 and 2022 consisted of the following: 2023 2022 Trade accounts payable $ 3,577,826 $ 19,862,487 Accrued compensation 9,837,104 12,574,921 Accrued litigation settlement (a) — 44,000,000 Other accrued expenses (b) (c) 6,432,814 3,249,477 $ 19,847,744 $ 79,686,885 (a) In July 2022, the Company entered into a memorandum of understanding for the proposed settlement of class action securities litigation (see Note 11). The final judicial order for the settlement was issued in January 2023. The settlement consisted of $30.0 million in cash and $14.0 million in shares of the Company's common stock to settle all outstanding claims. As of December 31, 2022, the Company's insurance carriers had paid the cash component of the proposed settlement, which amounts were being held in escrow. The Company's insurance carriers paid $252,000 of other expenses on behalf of the Company, which amounts were offset against the insurers' cash commitment as part of the settlement. During the three months ended March 31, 2023, the cash component of the settlement was released from escrow and the Company issued 760,083 shares of common stock pursuant to the securities class action settlement. (b) In March 2023, the Company entered into a stipulation of settlement for the proposed settlement of shareholder derivative litigation (see Note 11). In June 2023, the court preliminarily approved the proposed settlement. As part of the settlement, in July 2023, the Company paid $1.2 million to plaintiffs’ counsel for their fees and expenses. This amount was accrued within “Other accrued expenses” as of December 31, 2022. On October 12, 2023, the court entered an order and final judgment approving the Settlement, which was effective on November 13, 2023. (c) December 31, 2023 balance includes $4.3 million liability for unused grant funding.

Fixed Assets (Tables)

Fixed Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule Of Fixed Assets	Fixed assets at December 31, 2023 and 2022 consisted of the following: Cost Accumulated Net Book As of December 31, 2023 Leasehold improvements $ 15,917,596 $ (11,753,081) $ 4,164,515 Research and development equipment 3,538,698 (3,078,165) 460,533 Office furniture and fixtures 2,827,476 (2,816,577) 10,899 Computer equipment and other 3,529,129 (3,204,090) 325,039 $ 25,812,899 $ (20,851,913) $ 4,960,986 As of December 31, 2022 Leasehold improvements $ 15,803,108 $ (10,036,080) $ 5,767,028 Research and development equipment 5,300,104 (4,295,217) 1,004,887 Office furniture and fixtures 2,827,476 (2,803,800) 23,676 Computer equipment and other 5,360,712 (4,428,306) 932,406 $ 29,291,400 $ (21,563,403) $ 7,727,997

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets By Major Asset Class	The following sets forth goodwill and intangible assets by major asset class: December 31, 2023 December 31, 2022 Weighted Average Useful Gross Accumulated Impairment Net Book Gross Accumulated Net Book Indefinite lived: Goodwill $ 10,513,371 $ — $ (10,513,371) $ — $ 10,513,371 $ — $ 10,513,371 Definite lived: Licenses 10 — — — — 1,323,761 (1,323,761) — Bioject — 5,100,000 (3,115,556) (1,984,444) — 5,100,000 (2,988,889) 2,111,111 Other (a) 18 4,050,000 (4,050,000) — — 4,050,000 (4,031,250) 18,750 Total intangible assets 11 9,150,000 (7,165,556) (1,984,444) — 10,473,761 (8,343,900) 2,129,861 Total goodwill and intangible assets $ 19,663,371 $ (7,165,556) $ (12,497,815) $ — $ 20,987,132 $ (8,343,900) $ 12,643,232 (a)

Convertible Debt (Tables)

Convertible Debt (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Schedule of Convertible Debt	The balance of the Notes at December 31, 2023 was as follows: Principal amount $ 78,500,000 Principal amount converted into common shares (62,085,000) Unamortized debt issuance cost — Accrued interest 355,654 Net carrying amount $ 16,770,654

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Schedule of Preferred Stock Authorized, Issued And Outstanding	Shares Outstanding as of Shares Authorized Shares Issued 2023 2022 Series C Preferred Stock, par $0.001 1,091 1,091 9 9
Schedule Of Shares Authorized Under Stock Option Plans, By Exercise Price Range	The following table summarizes total stock options outstanding at December 31, 2023: Options Outstanding Options Exercisable Exercise Price Shares Underlying Options Weighted-Average Weighted Shares Underlying Options Weighted Average $4.32-$18.00 283,472 9.2 $ 14.11 66,918 $ 14.45 $18.01-$39.00 264,108 7.3 $ 35.69 141,600 $ 34.99 $39.01-$52.00 156,505 4.5 $ 44.93 156,271 $ 44.93 $52.01-$90.00 129,681 4.2 $ 76.82 121,124 $ 77.75 $90.01-$130.00 136,716 4.2 $ 100.15 131,640 $ 100.00 $130.01-$233.28 158,382 5.4 $ 140.27 129,250 $ 141.78 1,128,864 6.4 $ 58.76 746,803 $ 72.11
Schedule Of Stock Options, Activity	Stock option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Number of Weighted-Average Balance, December 31, 2022 1,018,095 $ 75.32 Granted 339,019 14.23 Exercised — — Cancelled (228,250) 66.47 Balance, December 31, 2023 1,128,864 $ 58.76
Schedule Of Restricted Stock Unit Activity	Restricted stock unit activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Number of Balance, December 31, 2022 212,964 Granted 194,747 Vested (99,420) Cancelled (33,497) Balance, December 31, 2023 274,794

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Schedule Of Maturities Of Operating Lease Liabilities	As of December 31, 2023, the maturities of the Company's operating lease liabilities were as follows: Year ending December 31, 2024 $ 3,247,000 2025 3,466,000 2026 3,555,000 2027 2,955,000 2028 2,310,000 Thereafter 2,132,000 Total remaining lease payments 17,665,000 Less: present value adjustment (4,226,000) Total operating lease liabilities 13,439,000 Less: current portion (2,407,000) Long-term operating lease liabilities $ 11,032,000 Weighted-average remaining lease term 5.3 years Weighted-average discount rate 8.9 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule Of Components Of Pretax Loss From Operations	The components of pretax loss from operations are as follows: Year Ended December 31, 2023 2022 2021 U.S. Domestic $ (134,979,579) $ (277,440,803) $ (302,614,003) Foreign (137,772) (211,249) (610,320) Pretax loss from operations $ (135,117,351) $ (277,652,052) $ (303,224,323)
Schedule Of Effective Income Tax Rate Reconciliation	The reconciliation of income taxes attributable to continuing operations computed at the statutory tax rates to income tax benefit, using a 21% statutory tax rate for December 31, 2023, 2022 and 2021, is as follows: Year Ended December 31, 2023 2022 2021 Benefit from income taxes at statutory rates $ (28,375,000) $ (58,307,000) $ (63,677,000) State income tax, net of federal benefit (3,922,000) (3,601,000) (3,447,000) Change in valuation allowance 28,394,000 61,065,000 77,424,000 Research and development tax credits (2,139,000) (7,534,000) (16,523,000) Stock-based compensation 2,099,000 2,913,000 483,000 Uncertain tax positions 861,000 2,291,000 6,509,000 Goodwill Impairment 1,962,000 — — Expired NOLs and credits 1,352,000 1,459,000 616,000 Limited NOLs and credits (997,000) (1,337,000) (542,000) Change in tax rates 365,000 (187,000) — Foreign tax rate differential (4,000) (8,000) (24,000) Other 404,000 3,246,000 (819,000) $ — $ — $ —
Schedule Of Deferred Tax Assets And Liabilities	Significant components of the Company’s deferred tax assets and liabilities as of December 31, 2023 and 2022 are shown below: As of December 31, 2023 2022 Deferred tax assets: Capitalized research expense $ 50,143,000 $ 41,252,000 NOL carryforwards 235,624,000 212,768,000 Research and development and other tax credits 27,734,000 26,442,000 Deferred revenue 22,000 538,000 Stock-based compensation 3,683,000 3,945,000 Acquired intangibles 907,000 559,000 Investment in affiliated entity 1,406,000 1,569,000 Lease liability 2,822,000 3,247,000 Fixed assets 337,000 57,000 Other 6,808,000 11,062,000 329,486,000 301,439,000 Valuation allowance (327,493,000) (299,124,000) Total deferred tax assets 1,993,000 2,315,000 Deferred tax liabilities: Acquired intangibles — (199,000) Right of use asset (1,993,000) (2,148,000) Total deferred tax liabilities (1,993,000) (2,347,000) Net deferred tax liabilities $ — $ (32,000)
Schedule Of Operating Loss And Tax Credit Carryforward Expirations	Based upon statute, federal and state losses and credits are expected to expire as follows (in millions): Expiration Date: Federal NOLs State NOLs Foreign NOLs Federal R&D State R&D 2024 $ 18.9 $ 9.1 $ — $ — $ — 2025 13.7 5.2 — — — 2026 12.2 7.1 — — — 2027 and thereafter 249.2 332.0 1.1 41.6 — Indefinite 719.3 0.6 — — 6.1 $ 1,013.3 $ 354.0 $ 1.1 $ 41.6 $ 6.1
Schedule Of Unrecognized Tax Benefits Rollforward	The following table summarizes the activity related to the Company's unrecognized tax benefits: Year ended December 31, 2023 2022 2021 Balance at beginning of the year $ 21,139,000 $ 18,819,000 $ 12,210,000 Increases related to current year tax positions 1,816,000 2,902,000 6,602,000 Increases (decreases) related to prior year tax positions (841,000) (582,000) 7,000 Balance at end of the year $ 22,114,000 $ 21,139,000 $ 18,819,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)		3 Months Ended		12 Months Ended
	Jan. 24, 2024	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Property, Plant and Equipment [Line Items]
Net loss from operations				$ 135,117,352	$ 279,818,065	$ 303,658,710
Working capital				110,500,000
Accumulated deficit				1,622,965,136	1,487,847,784
Cash, cash equivalents, and short-term investments				145,300,000
Proceeds from issuance of common stock				$ 5,461,745	82,955,311	209,441,410
Number of operating segments | segment				1
Allowance for doubtful accounts				$ 0	0
Impairment of goodwill		$ 10,500,000		10,513,371	0	0
Valuation allowance				(327,493,000)	(299,124,000)
Impairment of intangible assets				$ 1,984,444	0	0
Bioject
Property, Plant and Equipment [Line Items]
Impairment of intangible assets			$ 2,000,000
Subsequent Event
Property, Plant and Equipment [Line Items]
Stock split, conversion ratio	0.083333
Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, useful life				3 years
Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, useful life				5 years
Common stock | Sales Agreement
Property, Plant and Equipment [Line Items]
Proceeds from issuance of common stock				$ 5,500,000	$ 83,000,000	47,700,000
Common stock | Underwritten Public Offering
Property, Plant and Equipment [Line Items]
Proceeds from issuance of common stock						$ 162,100,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Antidilutive Securities Table (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	1,658,098	1,494,827	1,387,806
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	1,128,864	1,018,095	874,082
Service-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	274,794	212,964	204,005
Performance-based restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	0	9,328	55,279
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	275	275	275
Convertible notes | 6.50% Convertible Senior Notes Due 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities (in shares)	254,165	254,165	254,165

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Stock-Based Compensation Assumptions (Details) - Stock Options	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employees and Directors
Summary of assumptions used to estimate the fair value of stock options
Risk-free interest rate	4.05%	2.05%	0.91%
Expected volatility	100%	94%	93%
Expected life in years	5 years 6 months	5 years 8 months 12 days	6 years
Dividend yield	0%	0%	0%
Non Employee
Summary of assumptions used to estimate the fair value of stock options
Risk-free interest rate	3.90%	1.96%	1.45%
Expected volatility	89%	87%	87%
Expected life in years	10 years	10 years	10 years
Dividend yield	0%	0%	0%

Revenue Recognition and Conce_3

Revenue Recognition and Concentration of Credit Risk- Revenue from External Customers (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity	$ 832,010	$ 10,262,268	$ 1,774,758
Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
% of Total Revenue	100%	100%	100%
ApolloBio Corporation
Disaggregation of Revenue [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity	$ 245,056	$ 0	$ 0
ApolloBio Corporation | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
% of Total Revenue	29%	0%	0%
Plumbline Life Sciences, Inc. (affiliated entity)
Disaggregation of Revenue [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity	$ 0	$ 33,596	$ 245,310
Plumbline Life Sciences, Inc. (affiliated entity) | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
% of Total Revenue	0%	0%	14%
U.S. Department of Defense
Disaggregation of Revenue [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity	$ 0	$ 9,591,778	$ 754,853
U.S. Department of Defense | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
% of Total Revenue	0%	94%	43%
All other, including affiliated entities
Disaggregation of Revenue [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity	$ 586,954	$ 636,894	$ 774,595
All other, including affiliated entities | Revenue from Contract with Customer Benchmark | Customer Concentration Risk
Disaggregation of Revenue [Line Items]
% of Total Revenue	71%	6%	43%

Revenue Recognition and Conce_4

Revenue Recognition and Concentration of Credit Risk - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Revenue recognized from deferred revenue	$ 0	$ 14,000

Collaborative Agreements (Detai

Collaborative Agreements (Details) - USD ($)	1 Months Ended							12 Months Ended
	Jan. 31, 2022	Jun. 30, 2020	Apr. 30, 2020	Jan. 31, 2020	Aug. 30, 2019	Oct. 31, 2018	Apr. 30, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity								$ 832,010	$ 10,262,268	$ 1,774,758
ApolloBio Corporation | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received								3,600,000	1,200,000	4,500,000
ApolloBio | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Additional revenue to be achieved								$ 20,000,000
Obligation period to pay royalties								10 years
Funding received								$ 245,000
Revenue from collaborative arrangements and other contracts, including affiliated entity									0	0
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received								1,800,000	6,700,000	10,000,000
Collaborative agreement, funding to be received			$ 6,900,000
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | Lassa Fever And MERS Vaccine
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, funding to be received							$ 56,000,000
Collaborative agreement, period to receive funding for research and development							5 years
Accounts receivable								0	1,700,000
Accrued Liabilities								2,200,000	0
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | COVID19 Vaccine
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, funding to be received				$ 9,000,000				330,000	1,100,000	6,900,000
Accrued Liabilities								2,100,000
Grants receivable									2,300,000
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | CELLECTRA 3PSP Proprietary Smart Device
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, funding to be received			5,000,000
Coalition for Epidemic Preparedness Innovations | Collaborative Arrangement | IN O4800
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, funding to be received			$ 1,300,000
Bill And Melinda Gates Foundation | Collaborative Arrangement | D N A Encoded Monoclonal Antibody Technology
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative agreement, funding to be received					$ 1,100,000	$ 2,200,000		70,000	233,000	182,000
Grants receivable								87,000	153,000
Department Of Defence | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Grant proceeds received								0	6,100,000	27,100,000
Procurement contract								$ 0	$ 9,600,000	$ 755,000
Department Of Defence | Collaborative Arrangement | CELLECTRA 3PSP Proprietary Smart Device
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Funding received		$ 54,500,000
Purchase price, procurement contract	$ 10,700,000	$ 16,800,000

Short-term Investments and Fa_3

Short-term Investments and Fair Value Measurements - Schedule of Available-for-sale Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Sale [Abstract]
Cost	$ 134,873,427	$ 216,450,597
Gross Unrealized Gains	36,647	21,231
Gross Unrealized Losses	(3,927,161)	(9,802,431)
Fair Market Value	130,982,913	206,669,397
Mutual funds
Debt Securities, Available-for-sale, Sale [Abstract]
Cost	55,389,289	117,036,232
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3,522,888)	(9,373,514)
Fair Market Value	$ 51,866,401	107,662,718
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Contractual maturity	1 year
Debt Securities, Available-for-sale, Sale [Abstract]
Cost	$ 75,164,782	95,001,209
Gross Unrealized Gains	24,938	7,567
Gross Unrealized Losses	0	(44,266)
Fair Market Value	75,189,720	94,964,510
Certificates of deposit
Debt Securities, Available-for-sale, Sale [Abstract]
Cost	2,978,917	2,977,564
Gross Unrealized Gains	11,709	13,664
Gross Unrealized Losses	(300)	(320)
Fair Market Value	$ 2,990,326	$ 2,990,908
Certificates of deposit | Maximum
Debt Securities, Available-for-sale [Line Items]
Contractual maturity	1 year	1 year
U.S. agency mortgage-backed securities
Debt Securities, Available-for-sale, Sale [Abstract]
Cost	$ 1,340,439	$ 1,435,592
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(403,973)	(384,331)
Fair Market Value	$ 936,466	$ 1,051,261

Short-term Investments and Fa_4

Short-term Investments and Fair Value Measurements - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) position shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, realized gain	$ 1,000	$ 21,000
Debt securities, available-for-sale, realized gain	4,800,000	4,100,000
Net unrealized gain (loss) on available-for-sale equity securities	$ 5,850,626	$ (7,846,172)	$ (3,222,838)
Number of securities in a gross unrealized loss position | position	21
Number of securities in a gross unrealized loss position for more than twelve months | position	20
Unrealized loss on investments	$ 3,900,000
Fair Value, Inputs, Level 1
Debt Securities, Available-for-sale [Line Items]
Number of shares owned (in shares) | shares	597,808	597,808

Short-term Investments and Fa_5

Short-term Investments and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	$ 130,982,913	$ 206,669,397
Mutual funds
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	51,866,401	107,662,718
Certificates of deposit
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	2,990,326	2,990,908
U.S. agency mortgage-backed securities
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	936,466	1,051,261
Fair Value, Measurements, Recurring
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	130,982,913	206,669,397
Investments in affiliated entity	2,780,287	2,007,142
Total assets measured at fair value	133,763,200	208,676,539
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	127,056,121	202,627,228
Investments in affiliated entity	2,780,287	2,007,142
Total assets measured at fair value	129,836,408	204,634,370
Fair Value, Measurements, Recurring | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	3,926,792	4,042,169
Investments in affiliated entity	0	0
Total assets measured at fair value	3,926,792	4,042,169
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Investments in affiliated entity	0	0
Total assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Mutual funds
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	51,866,401	107,662,718
Fair Value, Measurements, Recurring | Mutual funds | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	51,866,401	107,662,718
Fair Value, Measurements, Recurring | Mutual funds | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | Mutual funds | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | U.S. treasury securities
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	75,189,720	94,964,510
Fair Value, Measurements, Recurring | U.S. treasury securities | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	75,189,720	94,964,510
Fair Value, Measurements, Recurring | U.S. treasury securities | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | U.S. treasury securities | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | Certificates of deposit
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	2,990,326	2,990,908
Fair Value, Measurements, Recurring | Certificates of deposit | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	2,990,326	2,990,908
Fair Value, Measurements, Recurring | Certificates of deposit | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	936,466	1,051,261
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	0	0
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	936,466	1,051,261
Fair Value, Measurements, Recurring | U.S. agency mortgage-backed securities | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Short-term investments	$ 0	$ 0

Certain Balance Sheet Items - S

Certain Balance Sheet Items - Schedule of Prepaid and Other Current Assets (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Certain Balance Sheet Items [Abstract]
Insurance recovery	$ 0	$ 30,000,000
Prepaid manufacturing expenses	1,486,638	1,401,028
Other prepaid expenses	3,907,027	18,729,453
Prepaid expenses and other current assets	$ 5,393,665	$ 50,130,481

Certain Balance Sheet Items -_2

Certain Balance Sheet Items - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Mar. 31, 2023	Jan. 31, 2023	Jul. 31, 2022
Accounts Payable and Accrued Expenses [Line Items]
Unused grant funding		$ 4,300,000
Nonrelated Party
Accounts Payable and Accrued Expenses [Line Items]
Trade accounts payable		3,577,826	$ 19,862,487
Accrued compensation		9,837,104	12,574,921
Accrued litigation settlement		0	44,000,000
Other accrued expenses		6,432,814	3,249,477
Accounts payable and accrued liabilities		$ 19,847,744	79,686,885
McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim
Accounts Payable and Accrued Expenses [Line Items]
Estimate of cash settlement					$ 30,000,000	$ 30,000,000
Estimate of shares settlement					$ 14,000,000	$ 14,000,000
Amount paid to other party			$ 252,000
Shares issued in settlement (in shares)				760,083
Behesti v. Kim, et al.
Accounts Payable and Accrued Expenses [Line Items]
Damages paid	$ 1,200,000

Fixed Assets (Details)

Fixed Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Cost	$ 25,812,899	$ 29,291,400
Accumulated Depreciation and Amortization	(20,851,913)	(21,563,403)
Net Book Value	4,960,986	7,727,997
Depreciation	2,621,649	3,656,713	$ 3,040,096
Property, plant and equipment sold	148,000	6,100,000
Property, plant and equipment disposed of	466,000	1,100,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	15,917,596	15,803,108
Accumulated Depreciation and Amortization	(11,753,081)	(10,036,080)
Net Book Value	4,164,515	5,767,028
Research and development equipment
Property, Plant and Equipment [Line Items]
Cost	3,538,698	5,300,104
Accumulated Depreciation and Amortization	(3,078,165)	(4,295,217)
Net Book Value	460,533	1,004,887
Office furniture and fixtures
Property, Plant and Equipment [Line Items]
Cost	2,827,476	2,827,476
Accumulated Depreciation and Amortization	(2,816,577)	(2,803,800)
Net Book Value	10,899	23,676
Computer equipment and other
Property, Plant and Equipment [Line Items]
Cost	3,529,129	5,360,712
Accumulated Depreciation and Amortization	(3,204,090)	(4,428,306)
Net Book Value	$ 325,039	$ 932,406

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of goodwill	$ 10,500,000		$ 10,513,371	$ 0	$ 0
Impairment of intangible assets			1,984,444	0	0
Amortization of intangible assets			$ 145,417	496,494	520,415
Impairment				$ 0	$ 0
Bioject
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets		$ 2,000,000

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Goodwill and Intangible Assets By Major Asset Class (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Indefinite lived:
Goodwill, gross		$ 10,513,371	$ 10,513,371
Impairment loss	$ (10,500,000)	(10,513,371)	0	$ 0
Goodwill		0	10,513,371
Definite lived:
Intangible assets, gross		9,150,000	10,473,761
Intangible assets, accumulated amortization		(7,165,556)	(8,343,900)
Impairment of intangible assets		(1,984,444)	0	$ 0
Intangible assets, net book value		0	2,129,861
Goodwill and intangible asset impairment		(12,497,815)
Total goodwill and intangible assets, gross		19,663,371	20,987,132
Total goodwill and intangible assets, net book value		$ 0	12,643,232
Weighted Average Useful Life (Yrs)
Definite lived:
Useful life (in years)		11 years
Licenses
Definite lived:
Intangible assets, gross		$ 0	1,323,761
Intangible assets, accumulated amortization		0	(1,323,761)
Impairment of intangible assets		0
Intangible assets, net book value		$ 0	0
Licenses | Weighted Average Useful Life (Yrs)
Definite lived:
Useful life (in years)		10 years
Bioject
Definite lived:
Intangible assets, gross		$ 5,100,000	5,100,000
Intangible assets, accumulated amortization		(3,115,556)	(2,988,889)
Impairment of intangible assets		(1,984,444)
Intangible assets, net book value		0	2,111,111
Other
Definite lived:
Intangible assets, gross		4,050,000	4,050,000
Intangible assets, accumulated amortization		(4,050,000)	(4,031,250)
Impairment of intangible assets		0
Intangible assets, net book value		$ 0	$ 18,750
Other | Weighted Average Useful Life (Yrs)
Definite lived:
Useful life (in years)		18 years

Convertible Debt - Narrative (D

Convertible Debt - Narrative (Details) - USD ($)			12 Months Ended
	Mar. 01, 2024	Mar. 01, 2019	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2022	Feb. 19, 2019
Debt Instrument [Line Items]
Accumulated deficit			$ (1,622,965,136)	$ (1,487,847,784)
Additional paid-in capital			(1,740,954,074)	(1,710,888,191)
Interest expense			1,222,789	1,253,952	$ 1,936,447
Accounting Standards Update 2020-06
Debt Instrument [Line Items]
Accumulated deficit						$ 1,800,000
Additional paid-in capital						3,300,000
Convertible senior notes						$ 1,500,000
6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Debt instrument, face amount			78,500,000
Debt issuance costs, net			0
Convertible Debt
Debt Instrument [Line Items]
Debt issuance costs, net			$ 2,200,000
Convertible Debt | 6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Debt instrument, face amount		$ 78,500,000					$ 78,500,000
Debt interest based on the fixed rate		6.50%					6.50%
Proceeds from issuance of debt		$ 75,700,000
Debt instrument, unamortized discount		$ 16,300,000
Debt instrument, interest rate, effective percentage			13.10%
Debt issuance costs, net			$ 592,000
Interest expense			1,200,000	$ 1,300,000	$ 1,900,000
Interest expense, debt			$ 1,100,000
Convertible Debt | 6.50% Convertible Senior Notes Due 2024 | Subsequent Event
Debt Instrument [Line Items]
Repayments of convertible debt	$ 16,900,000

Convertible Debt - Schedule of

Convertible Debt - Schedule of Convertible Debt (Details) - 6.50% Convertible Senior Notes Due 2024	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Principal amount	$ 78,500,000
Principal amount converted into common shares	(62,085,000)
Unamortized debt issuance cost	0
Accrued interest	355,654
Net carrying amount	$ 16,770,654

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Preferred Stock (Details) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Summary of common and preferred stock authorized, issued and outstanding
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	9	9
Preferred stock, shares outstanding (in shares)	9	9
Series C Preferred Stock
Summary of common and preferred stock authorized, issued and outstanding
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	1,091
Preferred stock, shares issued (in shares)	1,091
Preferred stock, shares outstanding (in shares)	9	9

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($)			12 Months Ended
		Nov. 09, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	May 16, 2023	Mar. 31, 2023	Jun. 24, 2022
Class of Stock [Line Items]
Convertible preferred stock, shares issued upon conversion, conversion price (in dollars per share)					$ 326.40
Common stock, shares issued (in shares)	[1]		22,793,075	21,090,938
Allocated share-based compensation expense			$ 10,400,000	$ 22,200,000	$ 25,000,000
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized			$ 4,300,000	$ 10,500,000
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition			1 year 3 months 18 days	1 year 7 months 6 days
Number of options outstanding to purchase common stock (in shares)			1,128,864	1,018,095
Aggregate intrinsic value of options outstanding			$ 2,000
Aggregate intrinsic value for options exercisable			$ 1,000
Options exercisable, remaining contractual term			5 years 6 months
Number of options expected to vest (in shares)			1,128,864
Options, expirations in period, weighted average exercise price (in dollars per share)			$ 38.86	$ 101.64	$ 54.72
Options, expirations in period (in shares)			9,357	6,437	583
Options, grants in period, weighted average grant date fair value (in dollars per share)			$ 11.19	$ 28.08	$ 91.32
Proceeds from stock options exercised			$ 0	$ 283,000	$ 6,700,000
Options, exercises in period, aggregate intrinsic value				81,000	7,000,000
McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim
Class of Stock [Line Items]
Shares issued in settlement (in shares)							760,083
Nonemployee
Class of Stock [Line Items]
Allocated share-based compensation expense			$ 669,000	1,300,000	1,400,000
Number of options outstanding to purchase common stock (in shares)			61,808
Research and Development Expense
Class of Stock [Line Items]
Allocated share-based compensation expense			$ 4,500,000	8,800,000	13,400,000
General and Administrative Expense
Class of Stock [Line Items]
Allocated share-based compensation expense			$ 5,900,000	$ 13,400,000	$ 11,600,000
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Number of shares of unvested restricted stock units and options outstanding (in shares)			274,794	212,964
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized			$ 3,500,000	$ 7,200,000
Employee service share-based compensation, nonvested awards, total compensation cost not yet recognized, period for recognition			1 year 6 months	1 year 8 months 12 days
Aggregate intrinsic value of unvested			$ 1,700,000
Aggregate intrinsic value of vested			$ 1,300,000
RSU's expected to vest (in shares)			274,794
Weighted average grant date fair value (in dollars per share)			$ 10.34	$ 37.44	$ 124.44
Restricted Stock Units (RSUs) | Former President and Chief Executive Officer
Class of Stock [Line Items]
Awards settled in cash, percentage			50%
2016 Incentive Plan
Class of Stock [Line Items]
Number of shares of vested restricted stock outstanding under the plan (in shares)			262,641
Number of common stock shares outstanding under the Incentive Plan (in shares)			961,499
Vesting period of incentive plan			3 years
Contractual year term of incentive plan			10 years
2022 Inducement Plan
Class of Stock [Line Items]
Reserved number of shares under the Incentive Plan (in shares)								166,666
Number of shares available for grants under the Incentive Plan (in shares)			125,575
Number of common stock shares outstanding under the Incentive Plan (in shares)			27,759
Number of shares of unvested restricted stock units and options outstanding (in shares)			10,278
2007 Incentive Plan
Class of Stock [Line Items]
Number of common stock shares outstanding under the Incentive Plan (in shares)			136,456
Vesting period of incentive plan			3 years
Contractual year term of incentive plan			10 years
2023 Incentive Plan
Class of Stock [Line Items]
Reserved number of shares under the Incentive Plan (in shares)						1,166,666
Number of shares available for grants under the Incentive Plan (in shares)			1,334,012
Number of common stock shares outstanding under the Incentive Plan (in shares)			3,150
Number of shares of unvested restricted stock units and options outstanding (in shares)			1,875
Vesting period of incentive plan			3 years
Contractual year term of incentive plan			10 years
Series C Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock, shares issued upon conversion (in shares)					275
Common stock | 2021 Sales Agreement
Class of Stock [Line Items]
Common stock aggregate offering price		$ 300,000,000
Sales Agents will be entitled to compensation		3%
Stock sale agreement, aggregate number of shares issued (in shares)			875,305	2,870,478
Sales made at a weighted average price (in dollars per share)			$ 6.33	$ 29.34
Stock sale agreement, aggregate proceeds from issuance of stock			$ 5,500,000	$ 83,000,000
Remaining authorized amount			$ 161,800,000
[1] (1) The Company effected a reverse stock split of its outstanding shares of common stock on January 24, 2024 where every twelve shares of its common stock issued and outstanding was converted into one share of common stock. Any fractional post-split shares as a result of the reverse split were paid in cash. Shareholders of the Company authorized the Board of Directors to approve the reverse stock split at a special meeting of stockholders held on January 12, 2024. Outstanding share amounts have been restated to reflect the reverse stock split on a retroactive basis for all periods presented.

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Options outstanding (in shares) | shares	1,128,864
Weighted-average remaining contractual life (in Years)	6 years 4 months 24 days
Weighted average exercise price (in dollars per share)	$ 58.76
Options exercisable (in shares) | shares	746,803
Weighted average exercise price (in dollars per share)	$ 72.11
$4.32-$18.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	4.32
Exercise price, upper range limit (in dollars per share)	$ 18
Options outstanding (in shares) | shares	283,472
Weighted-average remaining contractual life (in Years)	9 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 14.11
Options exercisable (in shares) | shares	66,918
Weighted average exercise price (in dollars per share)	$ 14.45
$18.01-$39.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	18.01
Exercise price, upper range limit (in dollars per share)	$ 39
Options outstanding (in shares) | shares	264,108
Weighted-average remaining contractual life (in Years)	7 years 3 months 18 days
Weighted average exercise price (in dollars per share)	$ 35.69
Options exercisable (in shares) | shares	141,600
Weighted average exercise price (in dollars per share)	$ 34.99
$39.01-$52.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	39.01
Exercise price, upper range limit (in dollars per share)	$ 52
Options outstanding (in shares) | shares	156,505
Weighted-average remaining contractual life (in Years)	4 years 6 months
Weighted average exercise price (in dollars per share)	$ 44.93
Options exercisable (in shares) | shares	156,271
Weighted average exercise price (in dollars per share)	$ 44.93
$52.01-$90.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	52.01
Exercise price, upper range limit (in dollars per share)	$ 90
Options outstanding (in shares) | shares	129,681
Weighted-average remaining contractual life (in Years)	4 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 76.82
Options exercisable (in shares) | shares	121,124
Weighted average exercise price (in dollars per share)	$ 77.75
$90.01-$130.00
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	90.01
Exercise price, upper range limit (in dollars per share)	$ 130
Options outstanding (in shares) | shares	136,716
Weighted-average remaining contractual life (in Years)	4 years 2 months 12 days
Weighted average exercise price (in dollars per share)	$ 100.15
Options exercisable (in shares) | shares	131,640
Weighted average exercise price (in dollars per share)	$ 100
$130.01-$233.28
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price, lower range limit (in dollars per share)	130.01
Exercise price, upper range limit (in dollars per share)	$ 233.28
Options outstanding (in shares) | shares	158,382
Weighted-average remaining contractual life (in Years)	5 years 4 months 24 days
Weighted average exercise price (in dollars per share)	$ 140.27
Options exercisable (in shares) | shares	129,250
Weighted average exercise price (in dollars per share)	$ 141.78

Stockholders' Equity - Schedu_3

Stockholders' Equity - Schedule of Stock Option Activity Under Equity Incentive Plan (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Number of Shares
Beginning balance (in shares) | shares	1,018,095
Granted (in shares) | shares	339,019
Exercised (in shares) | shares	0
Cancelled (in shares) | shares	(228,250)
Ending balance (in shares) | shares	1,128,864
Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 75.32
Granted (in dollars per share) | $ / shares	14.23
Exercised (in dollars per share) | $ / shares	0
Cancelled (in dollars per share) | $ / shares	66.47
Ending balance (in dollars per share) | $ / shares	$ 58.76

Stockholders' Equity - Schedu_4

Stockholders' Equity - Schedule of RSU Activity Under Equity Incentive Plan (Details) - Performance-based restricted stock units	12 Months Ended
	Dec. 31, 2023 shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares)	212,964
Granted (in shares)	194,747
Vested (in shares)	(99,420)
Cancelled (in shares)	(33,497)
Ending balance (in shares)	274,794

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands

1 Months Ended

3 Months Ended

12 Months Ended

Nov. 30, 2023 USD ($) ft² lease

Jul. 31, 2023 USD ($)

Apr. 30, 2020 defendent

Dec. 31, 2023 ft²

Sep. 30, 2023 ft²

Dec. 31, 2019 ft² agreement

Dec. 31, 2023 USD ($) ft²

Dec. 31, 2022 USD ($)

Dec. 31, 2021 USD ($)

Mar. 31, 2023 shares

Jan. 31, 2023 USD ($)

Jul. 31, 2022 USD ($)

Operating Leased Assets [Line Items]

Number of leases amended | lease

1

Area under lease amended | ft²

31,207

Lease, cost

$ 3,500

$ 3,400

$ 3,400

Number of agreements | agreement

2

McDermid v. Inovio Pharmaceuticals, Inc. and J. Joseph Kim

Operating Leased Assets [Line Items]

Estimate of cash settlement

$ 30,000

$ 30,000

Estimate of shares settlement

$ 14,000

$ 14,000

Shares issued in settlement (in shares) | shares

760,083

Behesti v. Kim, et al.

Operating Leased Assets [Line Items]

Number of defendants | defendent

8

Damages paid

$ 1,200

Minimum

Operating Leased Assets [Line Items]

Operating lease, remaining lease term

3 years 4 months 24 days

3 years 4 months 24 days

Maximum

Operating Leased Assets [Line Items]

Operating lease, remaining lease term

6 years

6 years

San Diego, California

Operating Leased Assets [Line Items]

Lessee, operating lease, area of land under lease | ft²

5,563

56,600

Initial term of contract

4 years 3 months 18 days

Annual increase of base rent percentage

3%

Deposit payments

$ 33

Plymouth Meeting, Pennsylvania

Operating Leased Assets [Line Items]

Lessee, operating lease, area of land under lease | ft²

7,000

4,400

13,500

57,360

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Maturities of Operating Lease Payments (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 3,247,000
2025	3,466,000
2026	3,555,000
2027	2,955,000
2028	2,310,000
Thereafter	2,132,000
Total remaining lease payments	17,665,000
Less: present value adjustment	(4,226,000)
Total operating lease liabilities	13,439,000
Less: current portion	(2,406,522)	$ (2,803,973)
Long-term operating lease liabilities	$ 11,032,066	$ 12,655,586
Weighted-average remaining lease term	5 years 3 months 18 days
Weighted-average discount rate	8.90%

Income Taxes - Components of Pr

Income Taxes - Components of Pretax Loss from Operations (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. Domestic	$ (134,979,579)	$ (277,440,803)	$ (302,614,003)
Foreign	(137,772)	(211,249)	(610,320)
Net loss before share in net loss of Geneos	$ (135,117,351)	$ (277,652,052)	$ (303,224,323)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Benefit from income taxes at statutory rates	$ (28,375)	$ (58,307)	$ (63,677)
State income tax, net of federal benefit	(3,922)	(3,601)	(3,447)
Change in valuation allowance	28,394	61,065	77,424
Research and development tax credits	(2,139)	(7,534)	(16,523)
Stock-based compensation	2,099	2,913	483
Uncertain tax positions	861	2,291	6,509
Goodwill Impairment	1,962	0	0
Expired NOLs and credits	1,352	1,459	616
Limited NOLs and credits	(997)	(1,337)	(542)
Change in tax rates	365	(187)	0
Foreign tax rate differential	(4)	(8)	(24)
Other	404	3,246	(819)
Income tax expense (benefit)	$ 0	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ 0	$ 0	$ 0
Tax benefits expired	7,300,000
Unrecognized tax benefits that would impact effective tax rate	20,500,000	19,700,000	$ 17,400,000
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards that will expire due to IRC Section 382 limitations	1,013,300,000
Net operating loss carryforwards				$ 719,300,000
Federal | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward amount	41,600,000
California
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards that will expire due to IRC Section 382 limitations	251,400,000
Pennsylvania
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards that will expire due to IRC Section 382 limitations	102,600,000
Korean State Income Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards that will expire due to IRC Section 382 limitations		$ 1,100,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	354,000,000
State | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward amount	$ 6,100,000

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Capitalized research expense	$ 50,143	$ 41,252
NOL carryforwards	235,624	212,768
Research and development and other tax credits	27,734	26,442
Deferred revenue	22	538
Stock-based compensation	3,683	3,945
Acquired intangibles	907	559
Investment in affiliated entity	1,406	1,569
Lease liability	2,822	3,247
Fixed assets	337	57
Other	6,808	11,062
Deferred tax assets, gross	329,486	301,439
Valuation allowance	(327,493)	(299,124)
Total deferred tax assets	1,993	2,315
Deferred tax liabilities:
Acquired intangibles	0	(199)
Right of use asset	(1,993)	(2,148)
Total deferred tax liabilities	(1,993)	(2,347)
Net deferred tax liabilities	$ 0	$ (32)

Income Taxes - Expected Expirat

Income Taxes - Expected Expirations of Federal and State Losses and Credits (Details) $ in Millions	Dec. 31, 2023 USD ($)
Federal
Expirations of Operating Loss Carryforwards, Components [Abstract]
2024	$ 18.9
2025	13.7
2026	12.2
2027 and thereafter	249.2
Indefinite	719.3
Total	1,013.3
State
Expirations of Operating Loss Carryforwards, Components [Abstract]
2024	9.1
2025	5.2
2026	7.1
2027 and thereafter	332
Indefinite	0.6
Total	354
Foreign Tax Authority
Expirations of Operating Loss Carryforwards, Components [Abstract]
2024	0
2025	0
2026	0
2027 and thereafter	1.1
Indefinite	0
Total	1.1
Research Tax Credit Carryforward | Federal
Expirations of Tax Credit Carryforwards [Abstract]
2024	0
2025	0
2026	0
2027 and thereafter	41.6
Indefinite	0
Total	41.6
Research Tax Credit Carryforward | State
Expirations of Tax Credit Carryforwards [Abstract]
2024	0
2025	0
2026	0
2027 and thereafter	0
Indefinite	6.1
Total	$ 6.1

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of the year	$ 21,139	$ 18,819	$ 12,210
Increases related to current year tax positions	1,816	2,902	6,602
Increases (decreases) related to prior year tax positions	(841)	(582)
Increases (decreases) related to prior year tax positions			7
Balance at end of the year	$ 22,114	$ 21,139	$ 18,819

401(k) Plan (Details)

401(k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Employer matching contribution, percent	50%
Maximum annual contribution per employee, percent	6%
Company's contribution to 401(k) plan	$ 1.4	$ 1.8	$ 1.5

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2022	Mar. 31, 2016	Mar. 31, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity				$ 832,010	$ 10,262,268	$ 1,774,758
Research and development				$ 86,676,563	$ 187,650,503	249,240,324
Plumbline Life Sciences
Related Party Transaction [Line Items]
Number of shares owned (in shares)	597,808			597,808	597,808
Ownership percentage	18.70%			17.80%	18.70%
Affiliated Entity
Related Party Transaction [Line Items]
Expenses to reimburse		$ 3,100,000
Term		5 years
Grant proceeds received				$ 1,000,000	$ 8,700,000
Affiliated Entity | Revenue under collaborative research and development arrangements from affiliated entities
Related Party Transaction [Line Items]
Revenue from collaborative arrangements and other contracts, including affiliated entity				0	34,000	245,000
Plumbline Life Sciences | Affiliated Entity
Related Party Transaction [Line Items]
Accounts receivable	$ 59,000			0	59,000
The Wistar Institute
Related Party Transaction [Line Items]
Agreement amended amount						13,600,000
The Wistar Institute | Affiliated Entity
Related Party Transaction [Line Items]
Awarded amount	1,200,000		$ 10,700,000
Awarded option amount	5,400,000					1,600,000
Research and development				1,800,000	1,400,000	$ 2,900,000
Accounts receivable	9,900,000			2,400,000	9,900,000
Accounts payable and accrued expenses	1,200,000			1,100,000	1,200,000
Prepaid expense	375,000			20,000	375,000
Deferred grant funding from affiliate	$ 88,000			$ 22,000	$ 88,000

Geneos Therapeutics, Inc. - Nar

Geneos Therapeutics, Inc. - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Feb. 28, 2021
Noncontrolling Interest [Line Items]
Share in net loss of Geneos			$ 0	$ 2,165,213	$ 434,387
Payments to acquire additional interest in subsidiaries			$ 0	$ 1,999,998	$ 0
Series A-2 One Preferred Stock
Noncontrolling Interest [Line Items]
Share in net loss of Geneos	$ 2,200,000
Investment in Geneos	0
Resulting in again on memeasurement	$ 165,000
Geneos Therapeutics, Inc.
Noncontrolling Interest [Line Items]
Noncontrolling interest, ownership percentage by parent	28%		23%			35%
Geneos Therapeutics, Inc.
Noncontrolling Interest [Line Items]
Loss from equity method investment, recorded and allocated to investment		$ (1,500,000)
Share in net loss of Geneos		434,000
Investment in Geneos		0
Geneos Therapeutics, Inc. | Common stock
Noncontrolling Interest [Line Items]
Investment in Geneos		0
Geneos Therapeutics, Inc. | Series A-1 Preferred Stock
Noncontrolling Interest [Line Items]
Share in net loss of Geneos		819,000
Geneos Therapeutics, Inc. | Preferred stock
Noncontrolling Interest [Line Items]
Share in net loss of Geneos		4,200,000
Investment in Geneos		$ 0
Payments to acquire additional interest in subsidiaries	$ 2,000,000

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event $ / shares in Units, $ in Millions			2 Months Ended
	Mar. 01, 2024 USD ($)	Jan. 24, 2024	Mar. 06, 2024 USD ($) $ / shares shares
Subsequent Event [Line Items]
Stock split, conversion ratio		0.083333
2021 Sales Agreement
Subsequent Event [Line Items]
Number of shares issued in transaction (in shares) | shares			543,620
Consideration received			$ 5.2
Sale of stock, price per share (in dollars per share) | $ / shares			$ 9.76
6.50% Convertible Senior Notes Due 2024 | Convertible Debt
Subsequent Event [Line Items]
Repayments of convertible debt	$ 16.9