Inovio Pharmaceuticals (INO) 10-Q 11 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 08, 2020
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	INOVIO PHARMACEUTICALS, INC.
Entity Central Index Key	0001055726
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		158,096,451

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 158,447,065	$ 22,196,097
Short-term investments	111,550,890	67,338,017
Accounts receivable	641,643	700,073
Accounts receivable from affiliated entities	634,198	1,332,044
Prepaid expenses and other current assets	2,479,204	1,584,598
Prepaid expenses and other current assets from affiliated entities	1,790,609	1,050,140
Total current assets	275,543,609	94,200,969
Fixed assets, net	12,104,410	12,773,017
Investment in affiliated entities	21,210,745	6,315,356
Intangible assets, net	3,557,081	3,693,851
Goodwill	10,513,371	10,513,371
Operating lease right-of-use assets	13,511,381	13,783,009
Other assets	2,480,087	2,672,024
Total assets	338,920,684	143,951,597
Current liabilities:
Accounts payable and accrued expenses	11,019,582	18,237,258
Accounts payable and accrued expenses due to affiliated entities	263,456	729,729
Accrued clinical trial expenses	5,061,166	4,049,727
Deferred revenue	67,269	92,353
Deferred revenue from affiliated entities	525	31,775
Operating lease liability	2,132,045	2,074,842
Grant funding liability	13,091,424	6,065,212
Grant funding liability from affiliated entities	659,175	708,425
Total current liabilities	32,294,642	31,989,321
Deferred revenue, net of current portion	100,354	101,567
Derivative liability	22,041,000	8,819,023
Operating lease liability, net of current portion	19,834,770	20,409,922
Deferred tax liabilities	32,046	32,046
Grant funding liability from affiliated entity, net of current portion	135,000	135,000
Other liabilities	73,444	36,943
Total liabilities	151,066,581	138,546,739
Stockholders’ equity:
Preferred stock	0	0
Common stock	145,915	101,361
Additional paid-in capital	957,962,628	742,646,785
Accumulated deficit	(772,326,709)	(739,785,655)
Accumulated other comprehensive income (loss)	(1,456,930)	472,608
Total Inovio Pharmaceuticals, Inc. stockholders’ equity	184,324,904	3,435,099
Non-controlling interest	3,529,199	1,969,759
Total stockholders’ equity	187,854,103	5,404,858
Total liabilities and stockholders’ equity	338,920,684	143,951,597
6.50% Convertible Senior Notes Due 2024
Current liabilities:
Convertible debt	63,730,182	64,180,325
Convertible Bonds [Member]
Current liabilities:
Convertible debt	$ 12,825,143	$ 12,842,592

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Total revenues	$ 1,327,274	$ 2,829,905
Operating expenses:
Research and development	19,111,188	24,389,888
General and administrative	7,448,354	6,975,029
Total operating expenses	26,559,542	31,364,917
Loss from operations	(25,232,268)	(28,535,012)
Other income (expense):
Interest income	416,569	625,535
Interest expense	(2,803,755)	(656,248)
Change in fair value of derivative liability	(13,221,977)	0
Gain (loss) on investment in affiliated entities	13,181,619	(750,103)
Other income (expense), net	(425,500)	(35,839)
Net loss before income tax benefit/(provision for income tax)	(33,135,404)	(29,351,667)
Income tax benefit/(provision for income taxes)	0	62,800
Net loss	(33,135,404)	(29,288,867)
Net loss attributable to non-controlling interest	594,350	69,605
Net loss attributable to Inovio Pharmaceuticals, Inc.	$ (32,541,054)	$ (29,219,262)
Net loss per share attributable to Inovio Pharmaceuticals, Inc. stockholders
Basic and diluted (in dollars per share)	$ (0.26)	$ (0.30)
Weighted average number of common shares outstanding
Basic and diluted (in shares)	124,623,263	97,494,968
Revenue under collaborative research and development arrangements
Revenues:
Total revenues	$ 71,500	$ 2,770,712
Revenue under collaborative research and development arrangements with affiliated entities
Revenues:
Total revenues	1,172,126	55,579
Miscellaneous revenue
Revenues:
Total revenues	$ 83,648	$ 3,614

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (33,135,404)	$ (29,288,867)
Other comprehensive income (loss):
Unrealized (loss) gain on short-term investments, net of tax	(1,929,538)	819,177
Comprehensive loss	(35,064,942)	(28,469,690)
Comprehensive loss attributable to non-controlling interest	594,350	69,605
Comprehensive loss attributable to Inovio Pharmaceuticals, Inc.	$ (34,470,592)	$ (28,400,085)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Total	Preferred stock	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	Non- controlling interest
Beginning balance (in shares) at Dec. 31, 2018		23	97,225,810
Beginning balance at Dec. 31, 2018	$ 87,032,407	$ 0	$ 97,226	$ 707,794,215	$ (620,426,436)	$ (528,867)	$ 96,269
Issuance of common stock for cash (in shares)			183,200
Issuance of common stock for cash	907,330		$ 183	907,147
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares)			525,000
Exercise of stock options for cash and vesting of RSUs, net of tax payments	(719,397)		$ 525	(719,922)
Equity component of issuance of convertible notes	15,752,698			15,752,698
Stock-based compensation	3,432,796			3,432,796
Acquisition of non-controlling interest in Geneos	3,030,107						3,030,107
Net loss attributable to common stockholders	(29,288,867)				(29,219,262)		(69,605)
Unrealized gain (loss) on short-term investments, net of tax	819,177					819,177
Ending balance (in shares) at Mar. 31, 2019		23	97,934,010
Ending balance at Mar. 31, 2019	80,966,251	$ 0	$ 97,934	727,166,934	(649,645,698)	290,310	3,056,771
Beginning balance (in shares) at Dec. 31, 2019		23	101,361,034
Beginning balance at Dec. 31, 2019	5,404,858	$ 0	$ 101,361	742,646,785	(739,785,655)	472,608	1,969,759
Issuance of common stock for cash (in shares)			43,148,952
Issuance of common stock for cash	208,241,933		$ 43,149	208,198,784
Exercise of stock options and warrants for cash and vesting of RSUs, net of tax payments (in shares)			1,405,114
Exercise of stock options for cash and vesting of RSUs, net of tax payments	3,100,703		$ 1,405	3,099,298
Stock-based compensation	4,001,553			4,017,761			(16,208)
Acquisition of non-controlling interest in Geneos	2,169,998						2,169,998
Net loss attributable to common stockholders	(33,135,404)				(32,541,054)		(594,350)
Unrealized gain (loss) on short-term investments, net of tax	(1,929,538)					(1,929,538)
Ending balance (in shares) at Mar. 31, 2020		23	145,915,100
Ending balance at Mar. 31, 2020	$ 187,854,103	$ 0	$ 145,915	$ 957,962,628	$ (772,326,709)	$ (1,456,930)	$ 3,529,199

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (33,135,404)	$ (29,288,867)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	809,559	930,907
Amortization of intangible assets	136,770	266,563
Amortization of operating lease right-of-use assets	271,628	0
Change in fair value of derivative liability	13,221,977	0
Stock-based compensation	4,001,553	3,432,796
Non-cash interest expense	213,559	656,248
Amortization of premiums on investments	0	1,908
Loss on short-term investments	475,490	35,839
Settlement of receivable with shares of common stock from affiliated entity (PLS)	(1,713,770)	0
(Gain) loss on equity investment in affiliated entities	(13,181,619)	750,103
Tax benefit from other unrealized gains on short-term investments	0	(217,820)
Unrealized transaction loss on foreign-currency denominated debt	(681,151)	0
Changes in operating assets and liabilities:
Accounts receivable	58,430	533,097
Accounts receivable from affiliated entities	697,846	(557,154)
Prepaid expenses and other current assets	(894,606)	19,789
Prepaid expenses and other current assets from affiliated entities	(740,469)	(320,741)
Other assets	191,937	(311,272)
Accounts payable and accrued expenses	(7,217,676)	(6,999,110)
Accrued clinical trial expenses	1,011,439	1,487,479
Accounts payable and accrued expenses due to affiliated entities	(466,273)	337,818
Deferred revenue	(26,297)	(121,873)
Deferred revenue from affiliated entities	(31,250)	(31,250)
Operating lease right-of-use assets and liabilities, net	(517,949)	(136,388)
Grant funding liability	7,026,212	(2,886,843)
Grant funding liability from affiliated entities	(49,250)	(12,500)
Other liabilities	36,501	(23,076)
Net cash used in operating activities	(25,452,721)	(32,454,347)
Cash flows from investing activities:
Purchases of investments	(56,698,250)	(65,198,491)
Proceeds from sale or maturity of investments	5,030,257	16,520,095
Purchases of capital assets	(140,952)	(658,731)
Net cash used in investing activities	(51,808,945)	(49,337,127)
Cash flows from financing activities:
Proceeds from issuance of convertible senior notes	0	75,658,953
Proceeds from issuance of common stock, net of issuance costs	208,241,933	907,330
Proceeds from stock option exercises	5,173,534	12,334
Taxes paid related to net share settlement of equity awards	(2,072,831)	(731,731)
Acquisition of non-controlling interest	2,169,998	3,030,107
Net cash provided by financing activities	213,512,634	78,876,993
Increase (Decrease) in cash and cash equivalents	136,250,968	(2,914,481)
Cash and cash equivalents, beginning of period	22,196,097	23,693,633	$ 23,693,633
Cash and cash equivalents, end of period	158,447,065	20,779,152	$ 22,196,097
Supplemental disclosures:
Amounts accrued for purchases of property and equipment	0	68,806
Interest paid	2,590,196	0
Right-of-use assets obtained in exchange for lease obligations	$ 0	$ 14,634,769

Organization and Operations

Organization and Operations	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Operations	Organization and Operations Inovio Pharmaceuticals, Inc. (the “Company” or “Inovio”), is a biotechnology company focused on rapidly bringing to market precisely designed DNA medicines to treat, cure, and protect people from diseases associated with human papillomavirus (HPV), cancer, and infectious diseases. The Company's DNA medicine pipeline is comprised of three types of candidates, DNA vaccines, DNA immunotherapies and DNA encoded monoclonal antibodies (dMABs). In clinical trials, Inovio has demonstrated that a DNA medicine can be delivered directly into cells in the body via its proprietary smart device to consistently activate robust and fully functional T cell and antibody responses against targeted cancers and pathogens. The Company's novel DNA medicines are made using its proprietary SynCon ® technology that creates optimized plasmids, which are circular strands of DNA that can produce antigens independently inside a cell to help the person's immune system recognize and destroy cancerous or virally infected cells. Inovio's hand-held CELLECTRA ® smart delivery devices provide optimized uptake of its DNA medicines within the cell, overcoming a key limitation of other DNA-based technology approaches. Human data to date have shown a favorable safety profile of Inovio’s DNA medicines delivered directly into cells in the body using the CELLECTRA ® smart delivery device in more than 6,000 administrations across more than 2,000 patients. Inovio's corporate strategy is to advance, protect, and provide its novel DNA medicines to meet urgent and emerging global health needs. The Company continues to advance and validate an array of DNA medicine candidates that target HPV-related diseases, cancer, and infectious diseases. The Company aims to advance these candidates through commercialization and continue to leverage third-party resources through collaborations and partnerships, including product license agreements. The Company's partners and collaborators include ApolloBio Corp., AstraZeneca, Beijing Advaccine, The Bill & Melinda Gates Foundation, Coalition for Epidemic Preparedness Innovations (CEPI), Defense Advanced Research Projects Agency (DARPA), GeneOne Life Science, HIV Vaccines Trial Network, the U.S. Defense Threat Reduction Agency’s Medical CBRN Defense Consortium (MCDC), National Cancer Institute, National Institutes of Health, National Institute of Allergy and Infectious Diseases, Plumbline Life Sciences, Regeneron Pharmaceuticals, Inc., Roche/Genentech, the University of Pennsylvania, the Walter Reed Army Institute of Research, and The Wistar Institute. The Company and its collaborators are currently conducting or planning clinical studies of its DNA medicines for HPV-associated precancers, including cervical, vulvar, and anal dysplasia; HPV-associated cancers, including head & neck, cervical, anal, penile, vulvar, and vaginal; other HPV-associated disorders, such as recurrent respiratory papillomatosis (RRP); glioblastoma multiforme (GBM); prostate cancer; HIV; Ebola; Middle East Respiratory Syndrome (MERS); Lassa fever; Zika virus; and the COVID-19 virus (coronavirus). Inovio was incorporated in Delaware in June 2001 and has its principal executive offices in Plymouth Meeting, Pennsylvania.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Inovio have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) as contained in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") for interim financial information and with instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The condensed consolidated balance sheet as of March 31, 2020 , the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, the condensed consolidated statements of stockholders' equity and the condensed consolidated statements of cash flows for the three months ended March 31, 2020 and 2019 are unaudited, but include all adjustments (consisting of normal recurring adjustments) that the Company considers necessary for a fair presentation of the financial position, results of operations, cash flows and changes in stockholders' equity for the periods presented. The results of operations for the three months ended March 31, 2020 shown herein are not necessarily indicative of the results that may be expected for the year ending December 31, 2020 , or for any other period. These unaudited financial statements, and notes thereto, should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2019 , included in the Company's Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (“SEC”) on March 12, 2020. The balance sheet at December 31, 2019 has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements include the accounts of Inovio Pharmaceuticals, Inc. and its subsidiaries. The Company consolidates its wholly-owned subsidiaries Genetronics, Inc. and VGX Pharmaceuticals, Inc. ("VGX") and records a 48% non-controlling interest for its subsidiary Geneos Therapeutics, Inc. ("Geneos") as well as 15% of VGX Animal Health, Inc., a subsidiary of VGX. All intercompany accounts and transactions have been eliminated upon consolidation. Inovio incurred a net loss attributable to common stockholders of $32.5 million for the three months ended March 31, 2020 . Inovio had working capital of $243.2 million and an accumulated deficit of $772.3 million as of March 31, 2020 . 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 $270.0 million and long-term investments of $21.2 million as of March 31, 2020 , 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 and/or future public or private debt or equity financings including use of its current or potential future At-the-Market Equity Offering Sales Agreements (each, a “Sales Agreement” and collectively, the “Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $208.2 million under a prior Sales Agreement, as amended, during the three months ended March 31, 2020, and net proceeds of $9.1 million under that Sales Agreement during the year ended December 31, 2019. The Company also received net proceeds of $75.7 million from a private placement of 6.50% convertible senior notes due 2024 (the “Notes”), net proceeds of $14.5 million from the private placement of 18 billion Korean Won (KRW) (approximately USD $15.0 million based on the exchange rate on the date of issuance) aggregate principal amount of its 1.0% convertible bonds due August 2024 (the "August 2019 Bonds"), and net proceeds of $4.0 million from the private placement of 4.7 billion KRW (approximately USD $4.1 million based on the exchange rate on the date of issuance) aggregate principal amount of its 1.0% convertible bonds due December 2024 (the "December 2019 Bonds" and, together with the August 2019 Bonds, the “Bonds”) during the year ended December 31, 2019. 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’s ability to continue its operations is dependent upon its ability to obtain additional capital in the future and achieve profitable operations. The Company expects to continue to rely on outside sources of financing to meet its capital needs and the Company may never achieve positive cash flow. These condensed consolidated financial statements do not include any adjustments to the specific amounts and classifications of assets and liabilities, which might be necessary should Inovio be unable to continue as a going concern. Inovio’s condensed consolidated financial statements as of and for the three months ended March 31, 2020 have been prepared on a going concern basis, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business for the foreseeable future. The Company has evaluated subsequent events after the balance sheet date through the date it issued these condensed consolidated financial statements.

Critical Accounting Policies

Critical Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Critical Accounting Policies	Critical Accounting Policies Collaboration Agreements The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") 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, the Company assesses whether the payments between the Company and the collaboration partner are subject to other accounting literature. 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”). However, if the Company concludes that its collaboration partner is not a customer for certain activities, such as for certain collaborative research and development activities, the Company presents such payments as a reduction of research and development expense. Revenue Recognition The Company recognizes revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which it expects to be entitled in exchange for those goods or services. To determine revenue recognition for contracts with customers, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies its performance obligations. At contract inception, the Company assesses the goods or services agreed upon within each contract and assess whether each good or service is distinct and determine those that are performance obligations. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Collaborative Arrangements The Company enters into collaborative arrangements with partners that typically include payment of one or more of the following: (i) license fees; (ii) product supply services; (iii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; and (iv) royalties on net sales of licensed products. Where a portion of non-refundable, upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue when (or as) the underlying performance obligation is satisfied. As part of the accounting for these arrangements, the Company must develop estimates and assumptions that require judgment of management to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligation. The standalone selling price may include items such as forecasted revenues, development timelines, discount rates and probabilities of technical and regulatory success. The Company evaluates each performance obligation to determine if it can be satisfied at a point in time or over time. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. License Fees If a license to intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company will utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Product Supply Services Arrangements that include a promise for future supply of drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company will assess if these options provide a material right to the licensee and if so, they will be accounted for as separate performance obligations. The Company evaluates whether it is the principal or agent in the arrangement. The Company had determined that it is the principal in the current arrangements as the Company controls the product supply before it is transferred to the customer. Milestone Payments At the inception of each arrangement that includes milestone payments (variable consideration), the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company's or its collaboration partner’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achieving such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration or other revenues and earnings in the period of adjustment. Royalties For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaborative arrangements. Grants The Company has determined that as of January 1, 2018, accounting for the Company’s various grant agreements falls 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. Beginning on January 1, 2018, all contributions received from current grant agreements are recorded as a contra-expense as opposed to revenue on the condensed consolidated statement of operations. Leases For its long-term operating leases, the Company recognized an operating lease right-of-use asset and an operating lease liability on its condensed 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 condensed consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred. Research and Development Expenses The Company’s activities have largely consisted of research and development efforts related to developing electroporation delivery technologies and DNA immunotherapies and vaccines. Research and development expenses consist of expenses incurred in performing research and development activities including salaries and benefits, facilities and other overhead expenses, clinical trials, contract services and other outside expenses. Research and development expenses are charged to operations as they are incurred. These expenses result from the Company's independent research and development efforts as well as efforts associated with collaborations and licensing arrangements. The Company reviews and accrues clinical trial expense based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of studies and other events. The Company follows this method since reasonably dependable estimates of the costs applicable to various stages of a research agreement or clinical trial can be made. 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. Valuation of Intangible Assets and Goodwill Intangible assets are amortized over their estimated useful lives ranging from two to 18 years. Acquired intangible assets are continuously being developed for the future economic viability contemplated at the time of acquisition. The Company is concurrently conducting preclinical studies and clinical trials using the acquired intangibles and has entered into licensing agreements for the use of these acquired intangibles. License costs are recorded based on the fair value of consideration paid and are amortized using the straight-line method over the shorter of the expected useful life of the underlying patents or the term of the related license agreement to the extent the license has an alternative future use. As of March 31, 2020 and December 31, 2019 , the Company’s intangible assets resulting from the acquisition of Inovio AS and Bioject Medical Technologies, Inc. ("Bioject"), and additional intangibles including license costs, net of accumulated amortization, totaled $3.6 million and $3.7 million , respectively. The determination of the value of intangible assets requires management to make estimates and assumptions that affect the Company’s condensed consolidated financial statements. The Company assesses potential impairments to intangible assets when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. The Company’s judgments regarding the existence of impairment indicators and future cash flows related to intangible assets are based on operational performance of its acquired businesses, market conditions and other factors. If impairment is indicated, the Company will reduce the carrying value of the intangible asset to fair value. While current and historical operating and cash flow losses are potential indicators of impairment, the Company believes the future cash flows to be received from its intangible assets will exceed the intangible assets’ carrying value, and accordingly, the Company has not recognized any impairment losses through March 31, 2020 . 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 at November 30, or more frequently if an event occurs indicating the potential for impairment. During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is more likely than not 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. The Company performed its annual assessment for goodwill impairment as of November 30, 2019 , identifying no impairment. Although there are inherent uncertainties in this assessment process, the estimates and assumptions the Company is using are consistent with its internal planning. If these estimates or their related assumptions change in the future, the Company may be required to record an impairment charge on all or a portion of its goodwill and intangible assets. Furthermore, the Company cannot predict the occurrence of future impairment triggering events nor the impact such events might have on its reported asset values. Future events could cause the Company to conclude that impairment indicators exist and that goodwill or other intangible assets associated with its acquired businesses are impaired. Any resulting impairment loss could have an adverse impact on the Company’s results of operations. See Note 8 for further discussion of the Company’s goodwill and intangible assets. Derivative Liabilities The Company evaluates its debt and equity issuances to determine if those contracts or embedded components of those contracts qualify as derivatives requiring separate recognition in the Company’s financial statements. The result of this accounting treatment is that the fair value of the embedded derivative is revalued at each balance sheet date and recorded as a liability, and the change in fair value during the reporting period is recorded in other income (expense) in the condensed consolidated statements of operations. In circumstances where the embedded conversion option in a convertible instrument is required to be bifurcated and there are also other embedded derivative instruments in the convertible instrument that are required to be bifurcated, the bifurcated derivative instruments are accounted for as a single, compound derivative instrument. The classification of derivative instruments, including whether such instruments should be recorded as liabilities or as equity, is reassessed at the end of each reporting period. Derivative instrument liabilities are classified in the balance sheet as current or non-current based on whether or not net-cash settlement of the derivative instrument is expected within twelve months of the balance sheet date. Foreign Currency Translation 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 gain (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the condensed consolidated statement of operations. Non- monetary assets and liabilities measured at cost are translated at the exchange rate at the date of the transaction.

Impact of Recently Issued Accou

Impact of Recently Issued Accounting Standards	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Impact of Recently Issued Accounting Standards	Impact of Recently Issued Accounting Standards 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. Accounting Standards Recently Adopted ASU No. 2019-12. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes . The Board issued this Update as part of its simplification initiative to improve areas of GAAP and reduce cost and complexity while maintaining usefulness. The main provision that impacts the Company is the removal of the exception to the incremental approach of intra-period tax allocation when there is a loss from continuing operations and income or gain from other items (for example, discontinued operations and other comprehensive income). ASU 2019-12 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2020. Early adoption is permitted, including adoption in an interim period. The Company has elected to early adopt ASU 2019-12. By early adopting, ASU 2019-12 became effective as of the beginning of 2020; however, there was no cumulative effect to be recognized with the early adoption. As of March 31, 2020, there was a loss from continuing operations and a cumulative loss in other comprehensive income and there was therefore no effect on the tax provision for the period ended March 31, 2020. ASU No. 2016-13 . In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) , which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available for sale debt securities. This standard includes the Company's financial instruments, such as accounts receivable and investments that are generally of high credit quality. Previously, when credit losses were measured under GAAP, an entity generally only considered past events and current conditions in measuring the incurred loss. The new guidance requires the Company to identify, analyze, document and support new methodologies for quantifying expected credit loss estimates for its financial instruments, using information such as historical experience and current economic conditions, plus the use of reasonably supportable forecast information. The Company adopted ASU 2016-13 on January 1, 2020, and there was no material impact to its condensed consolidated financial statements. The Company will continue to monitor the impact of the coronavirus, SARS-CoV-2 (“COVID-19”) outbreak on expected credit losses. ASU No. 2018-13 . In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement , which amends certain disclosure requirements over fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statement disclosures (see Note 7 for more information about the Company’s fair value classifications). ASU No. 2018-18 . In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarified the interaction between Topic 808, Collaborative Arrangements , and Topic 606, Revenue from Contracts with Customers . The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statements. ASU 2017-04. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). ASU 2017-04 simplifies the recognition and measurement of a goodwill impairment loss by eliminating Step 2 of the quantitative goodwill impairment test. The guidance requires a one-step impairment test in which an entity compares the fair value of a reporting unit with its carrying amount and recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, if any. ASU 2017-04 is effective for fiscal years beginning after December 15, 2019 and should be applied on a prospective basis. The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statements.

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue Recognition	Revenue Recognition During the three months ended March 31, 2020 , the Company recognized total revenue under collaborative research and development and other agreements of $1.1 million from its affiliated entity Plumbline Life Sciences, Inc. ("PLS"), $72,000 from AstraZeneca and $115,000 from various other contracts. Of the total revenue recognized during the three months ended March 31, 2020 , $58,000 was in deferred revenue as of December 31, 2019 . Performance obligations are generally satisfied within 12 months of the initial contract date.

Short-term Investments

Short-term Investments	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Short-term Investments	Short-term Investments Short-term investments at March 31, 2020 consisted of mutual funds, corporate debt securities and certificates of deposit. Short-term investments at December 31, 2019 consisted of mutual funds. 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 condensed consolidated statements of operations and are derived using the specific identification method for determining the cost of the securities sold. During the three months ended March 31, 2020 and 2019 , the Company recorded gross realized gain on investments of $50,000 and $18,000 , respectively, and gross realized loss on investments of $525,000 and $53,000 , respectively. During the three months ended March 31, 2020 and 2019 , the Company recorded net unrealized loss on available-for-sale equity securities of $5.1 million and $0 , respectively. No material balances were reclassified out of accumulated other comprehensive income (loss) for the three months ended March 31, 2020 and 2019. Interest and dividends on investments classified as available-for-sale are included in interest income in the condensed consolidated statements of operations. As of March 31, 2020 , the Company had 25 available-for-sale securities in an unrealized loss position, of which 2 with an aggregate total unrealized loss of $560,000 were in such position for longer than 12 months . The following is a summary of available-for-sale securities as of March 31, 2020 and December 31, 2019 : As of March 31, 2020 Contractual Maturity (in years) Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Mutual funds --- $ 109,616,722 $ 5,000 $ (5,055,092 ) $ 104,566,630 Corporate debt securities --- 5,175,000 — (1,202,700 ) 3,972,300 Certificates of deposit Less than 1 3,000,000 41,960 (30,000 ) 3,011,960 $ 117,791,722 $ 46,960 $ (6,287,792 ) $ 111,550,890 As of December 31, 2019 Contractual Maturity (in years) Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Mutual funds --- $ 66,599,219 $ 754,709 $ (15,911 ) $ 67,338,017 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 March 31, 2020 were primarily due to changes in interest rates, including credit spreads from perceived increased credit risks as a result of the COVID-19 global pandemic, and not due to increased credit risks associated with specific securities. The Company does not intend to sell these investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost bases, which may be at maturity. 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 March 31, 2020, the Company has not recorded an allowance for credit losses related to its available-for-sale debt securities.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	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. Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. The Company reviews the fair value hierarchy classification on a quarterly basis. Changes in the ability to observe valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy. The Company did not have any transfer of assets or liabilities between Level 1, Level 2 and Level 3 of the fair value hierarchy during the three months ended March 31, 2020 or 2019 . The following table presents the Company’s assets and liabilities that are measured at fair value on a recurring basis, and are determined using the following inputs as of March 31, 2020 : Fair Value Measurements at March 31, 2020 Total Quoted Prices in Active Markets (Level 1) Significant Other Unobservable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds $ 2,759,436 $ 2,759,436 $ — $ — Mutual funds 104,566,630 104,566,630 — — Corporate debt securities 3,972,300 — 3,972,300 — Certificates of deposit 3,011,960 — 3,011,960 — Investment in affiliated entities 21,210,745 21,210,745 — — Total assets $ 135,521,071 $ 128,536,811 $ 6,984,260 $ — Liabilities: Derivative liability (Note 9) $ 22,041,000 $ — $ — 22,041,000 Total liabilities $ 22,041,000 $ — $ — $ 22,041,000 The following table presents the Company’s assets and liabilities that are measured at fair value on a recurring basis, and are determined using the following inputs as of December 31, 2019 : Fair Value Measurements at December 31, 2019 Total Quoted Prices in Active Markets (Level 1) Significant Other Unobservable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds $ 2,349,729 $ 2,349,729 $ — $ — Mutual funds 67,338,017 67,338,017 — — Investment in affiliated entities 6,315,356 6,315,356 — — Total assets $ 76,003,102 $ 76,003,102 $ — $ — Liabilities: Derivative liability (Note 9) $ 8,819,023 $ — $ — $ 8,819,023 Total Liabilities $ 8,819,023 $ — $ — $ 8,819,023 Level 1 assets at March 31, 2020 consisted of money market funds and mutual funds held by the Company that are valued at quoted market prices, as well as the Company’s investments in affiliates, GeneOne and PLS. The Company accounts for its investment in 1,644,155 common shares of GeneOne based on the closing price of the shares on the Korean Stock Exchange on the applicable balance sheet date. 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 (KONEX) Market on the applicable balance sheet date. Unrealized gains and losses on the Company's equity securities are reported in the condensed consolidated statement of operations as a gain (loss) on investment in affiliated entities. Level 2 assets at March 31, 2020 consisted of corporate debt securities and certificates of deposit 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. There were no Level 3 assets held as of March 31, 2020 . Level 3 liabilities held as of March 31, 2020 consisted of the embedded conversion option contained in the August 2019 Bonds that met the criteria to be bifurcated and accounted for separately from the August 2019 Bonds (the "derivative liability") (see Note 9 below for more information). The derivative liability was recorded at fair value of $ 7.1 million upon the issuance of the August 2019 Bonds, and is subsequently remeasured to fair value at each reporting period. The derivative liability was initially valued and remeasured using a "with-and-without" method. The "with-and-without" methodology involves valuing the whole instrument on an as-is basis and then valuing the instrument without the embedded conversion option. The difference between the entire instrument with the embedded conversion option compared to the instrument without the embedded conversion option is the fair value of the derivative, recorded as the derivative liability. There was no derivative liability associated with the issuance of the December 2019 Bonds. The fair value of the August 2019 Bonds with the conversion option is estimated using a Monte Carlo simulation approach. The key inputs to valuing the August 2019 Bonds with the conversion option on the date of issuance and as of March 31, 2020 include the Company’s stock price on the valuation date; the expected annual volatility of the Company’s common stock, and the discount yield, which was derived by making the fair value of the August 2019 Bonds equal to the face value on the issuance date. Fair value measurements are highly sensitive to changes in these inputs and significant changes in these inputs could result in a significantly higher or lower fair value. The following table presents the changes in fair value of the Company's derivative liability for the three months ended March 31, 2020 : Balance at December 31, 2019 $ 8,819,023 Change in fair value 13,221,977 Balance at March 31, 2020 $ 22,041,000

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets The following sets forth the goodwill and intangible assets by major asset class: March 31, 2020 December 31, 2019 Weighted Average Useful Life (Yrs) Gross Accumulated Amortization Net Book Value Gross Accumulated Amortization Net Book Value Indefinite lived: Goodwill(a) $ 10,513,371 $ — $ 10,513,371 $ 10,513,371 $ — $ 10,513,371 Definite lived: Licenses 10 1,323,761 (1,255,291 ) 68,470 1,323,761 (1,248,104 ) 75,657 Bioject(b) 12 5,100,000 (2,248,889 ) 2,851,111 5,100,000 (2,175,556 ) 2,924,444 Other(c) 18 4,050,000 (3,412,500 ) 637,500 4,050,000 (3,356,250 ) 693,750 Total intangible assets 11 10,473,761 (6,916,680 ) 3,557,081 10,473,761 (6,779,910 ) 3,693,851 Total goodwill and intangible assets $ 20,987,132 $ (6,916,680 ) $ 14,070,452 $ 20,987,132 $ (6,779,910 ) $ 14,207,222 (a) Goodwill was recorded from the Inovio AS acquisition in January 2005, the acquisition of VGX in June 2009 and the acquisition of Bioject in April 2016 for $3.9 million , $6.2 million and $400,000 , respectively. (b) Bioject intangible assets represent the estimated fair value of developed technology and intellectual property which were recorded from the Bioject asset acquisition. (c) Other intangible assets represent the estimated fair value of acquired intellectual property from the Inovio AS acquisition. Aggregate amortization expense on intangible assets for the three months ended March 31, 2020 and 2019 was $137,000 and $267,000 , respectively. Estimated aggregate amortization expense is $ 410,000 for the remainder of fiscal year 2020 , $520,000 for 2021 , $ 493,000 for 2022 , $ 276,000 for 2023 , $ 253,000 for 2024 and $ 1.6 million for 2025 and subsequent years combined.

Convertible Debt

Convertible Debt	3 Months Ended
	Mar. 31, 2020
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 approximately $75.7 million . The Notes are senior unsecured obligations of the Company and accrue interest payable in cash semi-annually in arrears on March 1 and September 1 of each year, beginning on September 1, 2019, at a rate of 6.50% per annum. The Notes will mature on March 1, 2024, unless earlier converted, redeemed or repurchased. Prior to the close of business on the business day immediately preceding November 1, 2023, the Notes will be convertible at the option of the holders only upon the satisfaction of certain circumstances. Thereafter, the Notes will be convertible at the option of the holders at any time until the close of business on the scheduled trading day immediately before the maturity date. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election. The initial conversion rate will be 185.8045 shares per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $5.38 per share), subject to adjustment upon the occurrence of specified events. The Company may not redeem the Notes prior to March 1, 2022. On or after March 1, 2022, the Company may redeem all, or any portion, of the Notes for cash if the last reported sale price per share of the Company's common stock exceeds 130% of the conversion price on (i) each of at least 20 trading days (whether or not consecutive) during the 30 consecutive trading days ending on, and including, the trading day immediately before the Company sends the related redemption notice; and (ii) the trading day immediately before the date the Company sends such redemption notice. The redemption price will be equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. The Company evaluated the accounting for the issuance of the Notes and concluded that the embedded conversion features meet the requirements for a derivative scope exception for instruments that are both indexed to an entity’s own stock and classified in stockholders’ equity in its condensed consolidated balance sheet, and that the cash conversion guidance applies. Therefore, the Notes issuance proceeds of $78.5 million are allocated first to the liability component based on the fair value of non-convertible debt with otherwise identical residual terms with the residual proceeds allocated to equity for the conversion features. The Company determined that the fair value of the non-convertible debt upon issuance of the Notes was $62.2 million and recorded this amount as a liability and the offsetting amount as a debt discount as a reduction to the carrying value of the Notes on the closing date. The debt issuance costs associated with the Notes of $2.8 million are allocated to the liability and equity component in the same proportion as the issuance proceeds. The Company determined that all other features of the Notes were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to the Company's condensed consolidated financial statements. The balance of the Notes at March 31, 2020 is as follows: Principal amount $ 78,500,000 Unamortized debt discount on the liability component (13,356,690 ) Unamortized debt issuance cost (1,838,336 ) Accrued interest 425,208 Net carrying amount $ 63,730,182 The Company determined that the expected life of the Notes was equal to the period through November 1, 2023 as this represents the point at which the Notes are initially subject to repurchase by the Company at the option of the holders. Accordingly, the total debt discount of $18.6 million , inclusive of the fair value of the embedded conversion feature derivative at issuance, is being amortized using the effective interest method through November 1, 2023. The effective interest rate of the liability component is 13.1% . For the three months ended March 31, 2020 , the Company recognized $2.1 million of interest expense related to the Notes, of which $1.3 million related to the contractual interest coupon. As of March 31, 2020 , there have not been any conversions or redemptions of the Notes. August 2019 Convertible Bonds On August 1, 2019, the Company closed a private placement of the August 2019 Bonds with an aggregate principal amount of 18 billion Korean Won (KRW) (approximately USD $15.0 million based on the exchange rate on the date of issuance) issued to institutional investors led by Korea Investment Partners (KIP), a global venture capital and private equity firm based in Seoul, Korea. Net proceeds from the offering were approximately $14.5 million . The Company also announced its intent to pursue a listing of its securities on the KOSDAQ Market of the Korea Exchange (KOSDAQ) in the form of Korean Depositary Receipts (KDRs) representing shares of common stock. The August 2019 Bonds, which are unsecured obligations of the Company, were issued on August 1, 2019 and will accrue interest at a coupon rate of 1.00% per annum, payable quarterly. The August 2019 Bonds will mature on July 31, 2024, unless earlier converted or repurchased. The outstanding August 2019 Bonds will be repaid at maturity at a price equal to the principal of the outstanding bonds to be repaid plus a premium on such bonds to provide an internal rate of return with respect to such bonds of 6.00% . Commencing on August 1, 2020, the August 2019 Bonds will be convertible until the date that is one month prior to maturity date. Upon conversion, the Company will deliver KDRs, if the Company has any such securities listed on the KOSDAQ at that time, or otherwise shares of common stock, if KDRs are not listed on KOSDAQ at that time or the converting holder requests delivery of shares of common stock. The initial conversion rate was 211.0595 shares per KRW 1,000,000 in principal amount (equivalent to an initial conversion price of approximately USD $4.00 per share based on the exchange rate as of July 30, 2019), subject to adjustment upon the occurrence of specified events. The conversion rate was reset on January 2, 2020 and is subject to be reset on each three month anniversary thereafter until the maturity date to the then current market price if the current market price is lower than the conversion price then in effect; provided that the conversion rate will not exceed 351.7658 shares per KRW 1,000,000 (equivalent to a conversion price of approximately USD $2.40 per share based on the exchange rates as of July 30, 2019). The conversion rate was reset on January 2, 2020 to 273.8255 shares per KRW 1,000,000 in principal amount (equivalent to a conversion price of approximately USD $3.15 per share based on the exchange rate as of January 2, 2020). The August 2019 Bonds will be subject to repurchase by the Company at the option of the bondholders from and including July 31, 2022 up to the date that is one month prior to the maturity date at a repurchase price equal to the principal of the August 2019 Bonds to be repurchased plus a premium in order to provide an internal rate of return with respect to the August 2019 Bonds of 6.00% . In addition, upon the occurrence of a fundamental change (as defined in the August 2019 Bonds), the Company will be required to offer to repurchase the August 2019 Bonds at a repurchase price equal to the principal amount thereof plus accrued and unpaid interest thereon to but excluding the applicable repurchase date. Upon the occurrence of an event of default (as defined in the August 2019 Bonds), with the approval of at least 25% of the bondholders, the Company will be required to offer to repurchase the August 2019 Bonds at a repurchase price equal to the principal amount thereof plus a premium in order to provide an internal rate of return with respect to the August 2019 Bonds of 8.00% . The Company evaluated the accounting for the issuance of the August 2019 Bonds and concluded that the embedded conversion feature is considered a derivative requiring bifurcation from the August 2019 Bonds as it does not meet the equity scope exception due to the fact that it is denominated in a currency other than the Company's functional currency. The fair value of the conversion feature at August 1, 2019 was $7.1 million , which was recorded as a reduction to the carrying value of the debt. This debt discount is being amortized to interest expense over the term of the debt using the effective interest method. The conversion option is accounted for as a derivative liability, which is revalued each reporting period with the resulting change in fair value reflected in other income (expense), net, in the condensed consolidated statements of operations. The Company determined that all other features of the August 2019 Bonds were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to the Company's condensed consolidated financial statements. The balance of the August 2019 Bonds at March 31, 2020 is as follows: Principal amount $ 14,767,171 Unamortized debt discount (5,980,204 ) Unamortized debt issuance cost (225,603 ) Accretion of premium associated with the August 2019 Bonds 357,994 Accrued interest 36,918 Net carrying amount $ 8,956,276 The Company determined that the expected life of the August 2019 Bonds was equal to the period through August 1, 2022 as this represents the point at which the August 2019 Bonds are initially subject to repurchase by the Company at the option of the holders. Accordingly, the total debt discount of $7.3 million, inclusive of the fair value of the embedded conversion feature derivative at issuance, is being amortized using the effective interest method through August 1, 2022. The effective interest rate of the August 2019 Bonds is 29.4% . For the three months ended March 31, 2020 , the Company recognized $641,000 of interest expense related to the August 2019 Bonds, of which $38,000 related to the contractual interest coupon. As of March 31, 2020 , there have not been any conversions or redemptions of the August 2019 Bonds. The derivative liability is valued at $22.0 million as of March 31, 2020 . The change in fair value of the derivative liability was $13.2 million for the three months ended March 31, 2020 . December 2019 Convertible Bonds On December 26, 2019, the Company closed a private placement of convertible promissory notes (the “December 2019 Bonds”) with an aggregate principal amount of 4.7 billion KRW (approximately USD $4.1 million based on the exchange rate on the date of issuance) issued to a Korea-based institutional investor. Net proceeds from the offering were approximately $4.0 million . The December 2019 Bonds, which are unsecured obligations of the Company, were issued on December 31, 2019 and will accrue interest at a coupon rate of 1.00% per annum, payable quarterly. The December 2019 Bonds will mature on December 31, 2024, unless earlier converted or repurchased. The outstanding December 2019 Bonds will be repaid at maturity at a price equal to the principal of the outstanding bonds to be repaid plus a premium on such bonds to provide an internal rate of return with respect to such bonds of 6.00% . Commencing on December 31, 2020, the December 2019 Bonds will be convertible until the date that is one month prior to maturity date. Upon conversion, the Company will deliver KDRs, if the Company has any such securities listed on the KOSDAQ at that time, or otherwise shares of common stock of the Company. The initial conversion rate is 214.7766 shares per KRW 1,000,000 principal amount of Bonds (equivalent to an initial conversion price of approximately USD $4.00 per share based on the exchange rate as of December 19, 2019), subject to adjustment upon the occurrence of certain events. The conversion rate is subject to reset on July 2, 2020 and on each three month anniversary thereafter until the maturity date to the then current market price if the current market price is lower than the conversion price then in effect; provided that the conversion rate will not exceed 357.9611 shares per KRW 1,000,000 (equivalent to a conversion price of approximately USD $2.40 per share based on the exchange rate as of December 19, 2019). The December 2019 Bonds will be subject to repurchase by the Company at the option of the bondholders from and including December 31, 2022 up to the date that is one month prior to the maturity date at a repurchase price equal to the principal of the December 2019 Bonds to be repurchased plus a premium on the Bonds in order to ensure an internal rate of return with respect to the Bonds equal to 6.00% . In addition, upon the occurrence of a fundamental change (as defined in the Subscription Agreement) the Company will be required to offer to repurchase the Bonds at a repurchase price equal to the principal amount thereof plus accrued and unpaid interest thereon to but excluding the applicable repurchase date. If certain bankruptcy and insolvency-related events of default occur, the principal of, and accrued and unpaid interest on, all of the then outstanding December 2019 Bonds shall automatically become due and payable. If any other event of default occurs and is continuing, the holders of at least 25% of the in aggregate principal amount of the December 2019 Bonds by notice to the Company may declare the principal of, and accrued and unpaid interest on, all of the then-outstanding December 2019 Bonds to be due and payable. The Company evaluated the accounting for the issuance of the December 2019 Bonds and concluded that the embedded conversion feature does not require bifurcation from the December 2019 Bonds. Although the embedded conversion feature meets the definition of a derivative, it qualifies for the equity scope exception for instruments that are both indexed to an entity’s own stock and classified in stockholders’ equity in its consolidated balance sheet. The December 2019 Bonds are denominated in a foreign currency other than the Company’s functional currency, which would typically violate the settlement provision criteria when analyzing whether the conversion option is indexed to an entity’s own stock. However, per the terms of the agreement, the functional currency rate required to be used in a conversion scenario is fixed as of the date preceding the date of issuance of the Bonds. Therefore, the fluctuation in functional currency does not impact the settlement of the conversion option. Further, as there was no cash conversion feature or beneficial conversion feature on the date of issuance, and the Bonds were not issued at a substantial premium, all of the proceeds were recorded as a liability. The Company determined that all other features of the December 2019 Bonds were clearly and closely associated with a debt host and did not require bifurcation as a derivative liability, or the fair value of the feature was immaterial to the Company's consolidated financial statements. The balance of the December 2019 Bonds at March 31, 2020 is as follows: Principal amount $ 3,855,872 Unamortized debt issuance cost (43,740 ) Accretion of premium associated with the December 2019 Bonds 46,988 Accrued interest 9,747 Net carrying amount $ 3,868,867 The Company determined that the expected life of the December 2019 Bonds was equal to the period through December 31, 2022 as this represents the point at which the December 2019 Bonds are initially subject to repurchase by the Company at the option of the holders. The effective interest rate of the December 2019 Bonds is 6.2% . For the three months ended March 31, 2020 , the Company recognized $62,000 of interest expense related to the December 2019 Bonds, of which $10,000 related to the contractual interest coupon. As of March 31, 2020 , there have not been any conversions or redemptions of the December 2019 Bonds. As of March 31, 2020 , future minimum payments due under the Company's convertible debt instruments are as follows: Convertible Notes (1) August 2019 Bonds (2) December 2019 Bonds (2) Total Remainder of 2020 $ 2,551,000 $ 111,000 $ 29,000 $ 2,691,000 2021 5,103,000 148,000 39,000 5,290,000 2022 5,103,000 148,000 39,000 5,290,000 2023 5,103,000 148,000 39,000 5,290,000 2024 81,051,000 19,789,000 5,176,000 106,016,000 Total $ 98,911,000 $ 20,344,000 $ 5,322,000 $ 124,577,000 (1) Amounts represent contractual amounts due under the Notes, including interest based on the fixed rate of 6.5% per year. (2) Amounts represent contractual amounts due under the August 2019 and December 2019 Bonds, including interest based on the fixed rate of 1% per year plus a premium on such bonds to provide an internal rate of return with respect to such Bonds of 6% at maturity.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity The following is a summary of the Company's authorized and issued common and preferred stock as of March 31, 2020 and December 31, 2019 : Outstanding as of Authorized Issued March 31, 2020 December 31, 2019 Common Stock, par value $0.001 per share 600,000,000 145,915,100 145,915,100 101,361,034 Series C Preferred Stock, par value $0.001 per share 1,091 1,091 23 23 Common Stock In May 2018, the Company entered into a Sales Agreement with an outside placement agent (the “Placement Agent”) to sell shares of its common stock with aggregate gross proceeds of up to $100.0 million , from time to time, through an “at-the-market” equity offering program under which the Placement Agent would act as sales agent. During the first quarter of 2020, the Company and the Placement Agent entered into a first and second amendment to the Sales Agreement to increase the amount of common stock that may be sold under the Sales Agreement from $100.0 million to $250.0 million . Under the Sales Agreement, the Company set the parameters for the sale of shares, including the number of shares to be issued, the time period during which sales were requested to be made, limitation on the number of shares that may be sold in any one trading day and any minimum price below which sales may not be made. The Sales Agreement provided that the Placement Agent was entitled to compensation for its services in an amount equal to up to 3.0% of the gross proceeds from the sales of shares sold through the Placement Agent under the Sales Agreement. The Company had no obligation to sell any shares under the Sales Agreement, and could at any time suspend solicitation and offers under the Sales Agreement. During the three months ended March 31, 2020 , the Company sold 43,148,952 shares of its common stock, under the amended Sales Agreement. The sales were made at a weighted average price of $4.92 per share, resulting in aggregate net proceeds of $208.2 million . Following these sales, there was no remaining capacity under this Sales Agreement. As described in Note 18 below, subsequent to March 31, 2020, the Company and the Placement Agent entered into a new Sales Agreement to sell shares of its common stock with aggregate gross proceeds of up to $150.0 million . Stock Options and Restricted Stock Units The Company has a stock-based incentive plan, the 2016 Omnibus Incentive Plan (as amended to date, the "2016 Incentive Plan"), pursuant to which the Company may grant stock options, restricted stock awards, restricted stock units and other stock-based awards or short-term cash incentive awards to employees, directors and consultants. The 2016 Incentive Plan was originally approved by the Company's stockholders on May 13, 2016, and an amendment to the plan to increase the number of shares available for issuance was approved by the stockholders on May 8, 2019. The maximum number of shares of the Company’s common stock available for issuance over the term of the 2016 Incentive Plan may not exceed 18,000,000 shares, provided that commencing with the first business day of each calendar year beginning January 1, 2020, such maximum number of shares shall be increased by 2,000,000 shares of common stock unless the Company's Board of Directors determines, prior to January 1 for any such calendar year, to increase such maximum amount by a fewer number of shares or not to increase the maximum amount at all for such year. On January 1, 2020, the maximum number of shares to be issued increased by 2,000,000 . At March 31, 2020 , there were 18,000,000 shares of common stock reserved for issuance upon exercise of incentive awards granted and to be granted at future dates under the 2016 Incentive Plan. At March 31, 2020 , the Company had 7,536,221 shares of common stock available for future grant under the 2016 Incentive Plan, 2,667,710 shares underlying outstanding but unvested restricted stock units and options outstanding to purchase 5,631,777 shares of common stock under the 2016 Incentive Plan. The awards granted and available for future grant under the 2016 Incentive Plan generally vest over three years and have a maximum contractual term of ten years. The 2016 Incentive Plan terminates by its terms on March 9, 2026. 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 March 31, 2020 , the Company had options outstanding to purchase 3,984,209 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.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
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 common shares 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 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 and Bonds issued by the Company (discussed in Note 9) has been considered using the "if-converted" method. For the three months ended March 31, 2020 and 2019, basic and diluted net loss per share are the same, as the assumed exercise or settlement of stock options, restricted stock units and the potentially dilutive shares issuable upon conversion of the Notes and Bonds are anti-dilutive. The following table summarizes potential shares of common stock that were excluded from the diluted net loss per share calculation because of their anti-dilutive effect for the three months ended March 31, 2020 and 2019 : Common Stock Equivalents 2020 2019 Options to purchase common stock 9,615,986 11,027,600 Restricted stock units 2,667,710 1,720,128 Convertible preferred stock 8,456 8,456 Convertible notes 14,585,653 14,585,653 August 2019 Bonds 4,928,859 — December 2019 Bonds 1,009,450 — Total 32,816,114 27,341,837

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company incurs stock-based compensation expense related to restricted stock units 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 weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below: Three Months Ended March 31, 2020 2019 Risk-free interest rate 0.74% 2.44% Expected volatility 76% 70% Expected life in years 5.9 6.2 Dividend yield — — Total employee and director stock-based compensation expense recognized in the condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019 was $ 3.6 million and $3.2 million , respectively, of which $ 2.3 million and $1.9 million , respectively, was included in research and development expenses, and $ 1.3 million and $1.3 million , respectively, was included in general and administrative expenses. At March 31, 2020 , there was $8.0 million of total unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of 2.5 years . The weighted average grant date fair value per share, calculated using the Black-Scholes option pricing model, was $5.37 and $2.19 for employee and director stock options granted during the three months ended March 31, 2020 and 2019, respectively. At March 31, 2020 , there was $13.9 million of total unrecognized compensation expense related to unvested restricted stock units, which is expected to be recognized over a weighted-average period of 2.6 years. The weighted average grant date fair value per share was $8.32 and $3.38 for restricted stock units granted during the three months ended March 31, 2020 and 2019, 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 restricted stock units granted to non-employees for the three months ended March 31, 2020 and 2019 was $383,000 and $274,000 , respectively.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transaction, Due from (to) Related Party [Abstract]
Related Party Transactions	Related Party Transactions GeneOne Life Sciences The Company owns 1,644,155 shares of common stock in GeneOne as of March 31, 2020 and one of the Company's directors, Dr. David B. Weiner, acts as a consultant to GeneOne. In 2010, the Company entered into a collaboration and license agreement (the “GeneOne Agreement”) with GeneOne. Under the GeneOne Agreement, the Company granted GeneOne an exclusive license to the Company's SynCon ® universal influenza vaccine delivered with electroporation to be developed in certain countries in Asia (the “Product”). As consideration for the license granted to GeneOne, the Company received an upfront payment of $3.0 million , and is entitled to receive research support, annual license maintenance fees and royalties on net Product sales. The GeneOne Agreement also provides the Company with exclusive rights to supply devices for clinical and commercial purposes (including single use components) to GeneOne for use in the Product. The term of the GeneOne Agreement commenced upon execution and will extend on a country by country basis until the last to expire of all Royalty Periods for the territory (as such term is defined in the GeneOne Agreement) for any Product in that country, unless the GeneOne Agreement is terminated earlier in accordance with its provisions as a result of breach, by mutual agreement, or by GeneOne's right to terminate without cause upon prior written notice. In 2011, the Company entered into a collaborative development and license agreement (the “Hep Agreement”) with GeneOne. Under the Hep Agreement, as originally executed, the Company and GeneOne agreed to co-develop the Company’s SynCon ® therapeutic vaccines for hepatitis B and C infections (the “Hep Products”). Under the terms of the Hep Agreement, GeneOne will receive marketing rights for the Products in Asia, excluding Japan, and in return will fully fund IND-enabling and initial Phase 1 and 2 clinical studies with respect to the Hep Products. The Company will receive from GeneOne payments based on the achievement of clinical milestones and royalties based on sales of the Hep Products in the licensed territories, retaining all commercial rights to the Hep Products in all other territories. In 2013, the Company amended the Hep Agreement to grant back to the Company the SynCon ® therapeutic vaccines targeting hepatitis B, along with all associated rights, from the collaboration in return for certain remuneration including a percentage of license fees. In 2013, the Company further amended the Hep Agreement to in part provide exclusive patent rights to IL-28 technology for use with the Hep Products in Asia, excluding Japan. The Hep Agreement shall terminate upon the later of the expiration or abandonment of the last patent that is a component of the rights or 20 years after the effective date. In May 2015, the Company entered into a Collaborative Development Agreement with GeneOne to co-develop a DNA vaccine for MERS through Phase 1 clinical trials. Under the terms of the agreement, GeneOne will be responsible for funding all preclinical and clinical studies through Phase 1. In return, GeneOne will receive up to a 35% milestone-based ownership interest in the MERS immunotherapy upon achievement of the last milestone event of completion of the Phase 1 safety and immunogenicity study. The collaborative research program shall terminate upon the completion of activities under the development plan, unless sooner terminated. In January 2016, the Company and GeneOne amended the Collaborative Development Agreement for MERS to expand the agreement to test and advance the Company's DNA-based vaccine for preventing and treating Zika virus. GeneOne will be responsible for funding all preclinical and clinical studies through Phase 1. In return, GeneOne will receive up to a 35% milestone-based ownership interest in the Zika immunotherapy upon achievement of the last milestone event of the completion of the Phase 1 safety and immunogenicity study. All other agreement terms remain the same. Revenue recognized from GeneOne consisted of patent and device maintenance fees. For the three months ended March 31, 2020 and 2019, the Company recognized revenue from GeneOne of $31,000 and $31,000 , respectively. Operating expenses recorded from transactions with GeneOne related primarily to biologics manufacturing were $606,000 and $1.1 million for the three months ended March 31, 2020 and 2019, respectively. At March 31, 2020 and December 31, 2019 , the Company had an accounts receivable balance of $3,000 and $128,000 , respectively, and an accounts payable and accrued liability balance of $2,000 and $511,000 , respectively, related to GeneOne and its subsidiaries. At March 31, 2020 and December 31, 2019 , $294,000 and $284,000 , respectively, of prepayments made to GeneOne were classified as long-term other assets on the Company's condensed consolidated balance sheet. Plumbline Life Sciences, Inc. The Company owns 597,808 shares of common stock in Plumbline Life Sciences, Inc. ("PLS") as of March 31, 2020 and one of the Company's directors, Dr. David B. Weiner, acts as a consultant to PLS. On February 20, 2020, the Company entered into a Debt and Share Subscription Agreement with PLS under which the Company received 202,050 shares of PLS common stock in exchange for a portion of the outstanding accounts receivable balance due from PLS. Following the issuance of these shares and as of March 31, 2020, the Company holds a 19.9% ownership interest in PLS. Revenue recognized from PLS consists of milestone, license and patent fees. For the three months ended March 31, 2020 and 2019, the Company recognized revenue from PLS of $1.1 million and $24,000 , respectively. At March 31, 2020 and December 31, 2019 , the Company had an accounts receivable balance of $5,000 and $589,000 , 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 will reimburse 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. The Company will have the exclusive right to in-license new intellectual property developed under the agreement. In November 2016, the Company received a $6.1 million sub-grant through Wistar to develop a DNA-based monoclonal antibody against the Zika infection, with funding through July 2020. The Company is also a collaborator with Wistar on an Integrated Preclinical/Clinical AIDS Vaccine Development grant from the NIAID, with funding through February 2020. 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 three months ended March 31, 2020 and 2019, the Company recorded $619,000 and $838,000 , 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 the Bill and Melinda Gates Foundation and CEPI (see Note 15). Research and development expenses recorded from Wistar for the three months ended March 31, 2020 and 2019 were $362,000 and $487,000 , respectively. At March 31, 2020 and December 31, 2019 , the Company had an accounts receivable balance of $626,000 and $616,000 , respectively, and an accounts payable and accrued liability balance of $262,000 and $219,000 , respectively, related to Wistar. As of March 31, 2020 , the Company had $794,000 recorded as deferred grant funding on the condensed consolidated balance sheet related to Wistar.

Leases

Leases	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases	Leases The Company leases approximately 82,200 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 of 3.7 to 9.8 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. The Company performed an evaluation of its contracts with customers and suppliers in accordance with 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 condensed 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 March 31, 2020 , the maturities of the Company's operating lease liabilities were as follows: Remainder of 2020 $ 2,920,000 2021 3,968,000 2022 4,045,000 2023 4,023,000 2024 3,001,000 Thereafter 12,951,000 Total remaining lease payments 30,908,000 Less: present value adjustment (8,941,000 ) Total operating lease liabilities 21,967,000 Less: current portion (2,132,000 ) Long-term operating lease liabilities $ 19,835,000 Weighted-average remaining lease term 8.0 years Weighted-average discount rate 8.4 % Lease costs included in operating expenses in the condensed consolidated statements of operations for the three months ended March 31, 2020 and 2019 were $834,000 and $817,000 , 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 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.

Collaborative Agreements

Collaborative Agreements	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborative Agreements	Collaborative Agreements 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"), with an effective date of March 20, 2018. Under the terms of the ApolloBio Agreement, the Company has granted to ApolloBio the exclusive right to develop and commercialize VGX-3100, its DNA immunotherapy product designed to treat pre-cancers caused by HPV, within the territories of China, Hong Kong, Macao, Taiwan, and may include Korea in the event that no patent covering VGX-3100 is issued in China within the three years following the effective date of the ApolloBio Agreement. Under the ApolloBio Agreement, the Company received proceeds of $19.4 million in March 2018 which comprised the upfront payment of $23.0 million less $2.2 million in foreign income taxes and $1.4 million in certain foreign non-income taxes. The foreign income taxes were recorded as a provision for income taxes and the foreign non-income taxes were recorded as a general and administrative expense, on the condensed consolidated statement of operations. The Company also incurred advisory fees of $960,000 in connection with receiving the upfront payment from ApolloBio. These fees were determined to be incremental costs of obtaining the contract. The Company applied the practical expedient that permits a company to expense incremental costs to obtain a contract when the expected amortization period is one year or less and recorded the fees in general and administrative expense during the quarter ended March 31, 2018. No additional advisory fees are due related to the ApolloBio Agreement. In addition to the upfront payment, 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 the United States, China and Korea. 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. The Company evaluated the terms of the ApolloBio Agreement under Topic 606, and the license to VGX-3100 in the territories was identified as the only distinct performance obligation on a standalone basis as of the inception of the agreement. The Company concluded that the license was distinct from potential future manufacturing and supply obligations. The Company further determined that the transaction price under the agreement consisted of the $23.0 million upfront payment. The future potential milestone amounts were not included in the transaction price, as they were all determined to be fully constrained. As part of the evaluation of the development and regulatory milestones constraint, the Company determined that the achievement of such milestones is contingent upon success in future clinical trials and regulatory approvals, each of which is uncertain at this time. Future potential milestone amounts may be recognized as revenue under the ApolloBio Agreement, as well as under other collaborative research and development arrangements, if unconstrained. Reimbursable program costs will be recognized proportionately with the performance of the underlying services or delivery of drug supply and are excluded from the transaction price. The ApolloBio Agreement will continue in force until ApolloBio has no remaining royalty obligations. Either party may terminate the ApolloBio Agreement in the event the other party shall materially breach or default in the performance of its material obligations thereunder and such default continues for a specified period after written notice thereof. In addition, ApolloBio may terminate the ApolloBio Agreement at any time beginning one year after the effective date for any reason upon 90 days written notice to the Company. Under Topic 606, the entire transaction price of $23.0 million was allocated to the license performance obligation. The Company determined that during the quarter ended June 30, 2018, the transfer of technology occurred and accordingly, the performance obligation was fully satisfied. The Company has recorded the gross upfront payment received from ApolloBio of $23.0 million as revenue under collaborative research and development arrangements on the condensed consolidated statement of operations during the three months ended June 30, 2018. AstraZeneca On August 7, 2015, the Company entered into a license and collaboration agreement with MedImmune, the global biologics research and development arm of AstraZeneca ("AstraZeneca"). Under the agreement, AstraZeneca acquired exclusive rights to the Company's INO-3112 immunotherapy, renamed as MEDI0457, which targets cancers caused by human papillomavirus (HPV) types 16 and 18, with the ability to sublicense those license rights. AstraZeneca made an upfront payment of $27.5 million to the Company in September 2015. AstraZeneca may be obligated to make potential future development and regulatory event-based payments to the Company totaling up to $125 million and potential future commercial event-based payments totaling up to $115 million , in each case upon the achievement of specified milestones related to MEDI0457 set forth in the license and collaboration agreement. AstraZeneca will fund all development costs associated with MEDI0457 immunotherapy. The Company is entitled to receive up to mid-single to double-digit tiered royalties on MEDI0457 product sales. Under the agreement, AstraZeneca can also request the Company to provide certain clinical manufacturing at an agreed upon price. The Company determined these options did not represent material rights at the inception of the agreement. Within the broader collaboration, AstraZeneca had rights to co-develop up to two additional DNA-based cancer vaccine product candidates not included in the Company's current product pipeline. The Company has received notice that AstraZeneca intends to discontinue activities with respect to the research collaboration programs, other than MEDI0457, that were covered by the collaboration agreement. As of December 31, 2017, the Company had recognized all of the $27.5 million upfront payment as revenue, as all identified material performance obligations had been met with respect to that payment. During the three months ended March 31, 2020 , the Company recognized revenues of $72,000 from AstraZeneca primarily for manufacturing services. During the three months ended March 31, 2019 , the Company recognized revenues of $2.7 million from AstraZeneca primarily from a milestone achieved in the first quarter of 2019 triggered by the initiation of a Phase 2 portion of an ongoing clinical trial in the third major indication, as well as for manufacturing services. As of March 31, 2020 , the Company had deferred revenue of $62,000 related to AstraZeneca. The deferred revenue relates to advanced payments made by the Company to a third-party biologics manufacturer for which AstraZeneca is obligated to reimburse the Company. Coalition for Epidemic Preparedness Innovations In April 2018, the Company entered into agreements with CEPI, pursuant to which the Company intends to develop vaccine candidates against Lassa fever and MERS. The goal of the collaboration between the Company and CEPI is to conduct research and development so that investigational stockpiles will be ready for clinical efficacy trial testing during potential disease outbreaks. The agreements with CEPI contemplate preclinical studies, as well as Phase 1 and Phase 2 clinical trials, occurring over multiple years. As part of the arrangement between the parties, CEPI has 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. During the three months ended March 31, 2020 and 2019, the Company received funding of $987,000 and $1.7 million , respectively, related to the CEPI Lassa and MERS grant and recorded it as contra-research and development expense. As of March 31, 2020 , the Company had $4.4 million recorded as deferred grant funding on the condensed consolidated balance sheet related to the CEPI Lassa and MERS grant. In January 2020, CEPI awarded the Company a grant of up to $9.0 million to develop a vaccine against SARS-CoV-2/COVID-19. This initial CEPI funding will support the preclinical and clinical development through Phase 1 human testing in the United States of INO-4800, the Company's coronavirus vaccine candidate matched to the outbreak strain. During the three months ended March 31, 2020 , the Company received funding of $2.4 million related to the CEPI COVID-19 grant and recorded it as contra-research and development expense. As of March 31, 2020 , the Company had $2.9 million recorded as deferred grant funding on the condensed consolidated balance sheet related to the CEPI COVID-19 grant. Bill & Melinda Gates Foundation In October 2018, the Bill & Melinda Gates Foundation (“Gates”) awarded and funded the Company a grant of $2.2 million to advance the development of DNA-encoded monoclonal antibody technology (“dMAb”) 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 three months ended March 31, 2020 and 2019, the Company recorded $134,000 and $1.1 million as contra-research and development expense, respectively, related to the Gates dMAb grant. As of March 31, 2020, the Company had $892,000 recorded as deferred grant funding on the condensed consolidated balance sheet related to the grant. In March 2020, Gates awarded and funded the Company a grant of $5.0 million to accelerate the development of its CELLECTRA ® 3PSP proprietary smart device for the intradermal delivery of INO-4800, the Company's DNA vaccine candidate for COVID-19. During the three months ended March 31, 2020 , the Company recorded $64,000 as contra-research and development expense and had $4.9 million recorded as deferred grant funding on the condensed consolidated balance sheet related to this Gates grant.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company uses an estimated annual effective tax rate, which is based on expected annual income, statutory tax rates and tax planning opportunities available in the various jurisdictions in which the Company operates, to determine its quarterly provision for income taxes. Certain significant or unusual items are separately recognized in the quarter in which they occur and can be a source of variability in the effective tax rates from quarter to quarter. Due to the adoption of ASU 2019-12 which removes the exception under ASC 740-20-45-7 to consider all sources of income in order to determine the tax benefit resulting from a loss from continuing operations, ASC 740-20-45-7 no longer applies. On March 27, 2020, the United States enacted the Coronavirus Aid, Relief and Economic Security Act (CARES Act). The CARES Act is an emergency economic stimulus package that includes spending and tax breaks to strengthen the United States economy and fund a nationwide effort to curtail the effect of COVID-19. The CARES Act provides sweeping tax changes in response to the COVID-19 pandemic; some of the more significant provisions are removal of certain limitations on utilization of net operating losses, increasing the loss carryback period for certain losses to five years, and increasing the ability to deduct interest expense, as well as amending certain provisions of the previously enacted Tax Cuts and Jobs Act. At March 31, 2020, the Company has not recorded any income tax provision/(benefit) for the impact for the CARES Act due to the Company’s history of net operating losses generated and the maintenance of a full valuation allowance against its net deferred tax assets. The Company will continue to analyze the impact that the CARES Act will have, if any, on its financial position, results of operations or cash flows.

Geneos Therapeutics, Inc.

Geneos Therapeutics, Inc.	3 Months Ended
	Mar. 31, 2020
Noncontrolling Interest [Abstract]
Geneos Therapeutics, Inc.	Geneos Therapeutics, Inc. In August 2016, the Company incorporated a subsidiary, Geneos Therapeutics, Inc. (“Geneos”), to develop and commercialize neoantigen-based personalized cancer therapies. In February 2019, the Company completed a spin-out of Geneos, after Geneos completed the initial closing of a $4.5 million preferred stock financing. The Company invested $1.2 million in the preferred stock financing, which was led by an outside investor. In January 2020, Geneos completed the second closing of a $3.0 million preferred stock financing, where the Company invested an additional $800,000 . Following this transaction, as of March 31, 2020, the Company holds 52% of the outstanding equity, on an as-converted to common stock basis, of Geneos. The Company's ownership percentage of Geneos would decrease in the event of additional purchases of preferred stock of Geneos by other investors. The Company has exclusively licensed its SynCon ® immunotherapy and CELLECTRA ® technology platform to Geneos to be used in the field of personalized, neoantigen-based therapy for cancer. The license agreement provides for potential royalty payments to the Company in the event that Geneos commercializes any products using the licensed technology.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 3, 2020, the Company entered into a new Sales Agreement with the Placement Agent to sell shares of its common stock with aggregate gross proceeds of up to $150.0 million . Under the new Sales Agreement, the Company will set the parameters for the sale of shares, including the number of shares to be issued, the time period during which sales are requested to be made, limitation on the number of shares that may be sold in any one trading day and any minimum price below which sales may not be made. The Placement Agent will be entitled to compensation for its services in an amount equal to up to 3.0% of the gross proceeds from the sales of shares sold through the Placement Agent under the new Sales Agreement. The Company has no obligation to sell any shares under the Sales Agreement, and may at any time suspend solicitation and offers under the Sales Agreement. From April 6, 2020 through May 8, 2020, the Company has sold 12,041,178 shares of common stock under the new Sales Agreement for net proceeds of $121.7 million . The sales were made at a weighted average price of $10.26 per share.

Basis of Presentation (Policies

Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements of Inovio have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) as contained in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") for interim financial information and with instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. The condensed consolidated balance sheet as of March 31, 2020 , the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, the condensed consolidated statements of stockholders' equity and the condensed consolidated statements of cash flows for the three months ended March 31, 2020 and 2019 are unaudited, but include all adjustments (consisting of normal recurring adjustments) that the Company considers necessary for a fair presentation of the financial position, results of operations, cash flows and changes in stockholders' equity for the periods presented. The results of operations for the three months ended March 31, 2020 shown herein are not necessarily indicative of the results that may be expected for the year ending December 31, 2020 , or for any other period. These unaudited financial statements, and notes thereto, should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2019 , included in the Company's Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (“SEC”) on March 12, 2020. The balance sheet at December 31, 2019 has been derived from the audited financial statements at that date, but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements include the accounts of Inovio Pharmaceuticals, Inc. and its subsidiaries. The Company consolidates its wholly-owned subsidiaries Genetronics, Inc. and VGX Pharmaceuticals, Inc. ("VGX") and records a 48% non-controlling interest for its subsidiary Geneos Therapeutics, Inc. ("Geneos") as well as 15% of VGX Animal Health, Inc., a subsidiary of VGX. All intercompany accounts and transactions have been eliminated upon consolidation. Inovio incurred a net loss attributable to common stockholders of $32.5 million for the three months ended March 31, 2020 . Inovio had working capital of $243.2 million and an accumulated deficit of $772.3 million as of March 31, 2020 . 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 $270.0 million and long-term investments of $21.2 million as of March 31, 2020 , 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 and/or future public or private debt or equity financings including use of its current or potential future At-the-Market Equity Offering Sales Agreements (each, a “Sales Agreement” and collectively, the “Sales Agreements”). The Company has a history of conducting debt and equity financings, including the receipt of net proceeds of $208.2 million under a prior Sales Agreement, as amended, during the three months ended March 31, 2020, and net proceeds of $9.1 million under that Sales Agreement during the year ended December 31, 2019. The Company also received net proceeds of $75.7 million from a private placement of 6.50% convertible senior notes due 2024 (the “Notes”), net proceeds of $14.5 million from the private placement of 18 billion Korean Won (KRW) (approximately USD $15.0 million based on the exchange rate on the date of issuance) aggregate principal amount of its 1.0% convertible bonds due August 2024 (the "August 2019 Bonds"), and net proceeds of $4.0 million from the private placement of 4.7 billion KRW (approximately USD $4.1 million based on the exchange rate on the date of issuance) aggregate principal amount of its 1.0% convertible bonds due December 2024 (the "December 2019 Bonds" and, together with the August 2019 Bonds, the “Bonds”) during the year ended December 31, 2019. 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’s ability to continue its operations is dependent upon its ability to obtain additional capital in the future and achieve profitable operations. The Company expects to continue to rely on outside sources of financing to meet its capital needs and the Company may never achieve positive cash flow. These condensed consolidated financial statements do not include any adjustments to the specific amounts and classifications of assets and liabilities, which might be necessary should Inovio be unable to continue as a going concern. Inovio’s condensed consolidated financial statements as of and for the three months ended March 31, 2020 have been prepared on a going concern basis, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business for the foreseeable future. The Company has evaluated subsequent events after the balance sheet date through the date it issued these condensed consolidated financial statements.
Collaboration Agreements	Collaboration Agreements The Company assesses whether its collaboration agreements are subject to Accounting Standards Codification ("ASC") 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, the Company assesses whether the payments between the Company and the collaboration partner are subject to other accounting literature. 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”). However, if the Company concludes that its collaboration partner is not a customer for certain activities, such as for certain collaborative research and development activities, the Company presents such payments as a reduction of research and development expense.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which it expects to be entitled in exchange for those goods or services. To determine revenue recognition for contracts with customers, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies its performance obligations. At contract inception, the Company assesses the goods or services agreed upon within each contract and assess whether each good or service is distinct and determine those that are performance obligations. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Collaborative Arrangements The Company enters into collaborative arrangements with partners that typically include payment of one or more of the following: (i) license fees; (ii) product supply services; (iii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; and (iv) royalties on net sales of licensed products. Where a portion of non-refundable, upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue when (or as) the underlying performance obligation is satisfied. As part of the accounting for these arrangements, the Company must develop estimates and assumptions that require judgment of management to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligation. The standalone selling price may include items such as forecasted revenues, development timelines, discount rates and probabilities of technical and regulatory success. The Company evaluates each performance obligation to determine if it can be satisfied at a point in time or over time. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. License Fees If a license to intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company will recognize revenues from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company will utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Product Supply Services Arrangements that include a promise for future supply of drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company will assess if these options provide a material right to the licensee and if so, they will be accounted for as separate performance obligations. The Company evaluates whether it is the principal or agent in the arrangement. The Company had determined that it is the principal in the current arrangements as the Company controls the product supply before it is transferred to the customer. Milestone Payments At the inception of each arrangement that includes milestone payments (variable consideration), the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company's or its collaboration partner’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achieving such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration or other revenues and earnings in the period of adjustment. Royalties For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaborative arrangements.
Grants	Grants The Company has determined that as of January 1, 2018, accounting for the Company’s various grant agreements falls 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. Beginning on January 1, 2018, all contributions received from current grant agreements are recorded as a contra-expense as opposed to revenue on the condensed consolidated statement of operations.
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 condensed 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 condensed consolidated statements of operations. Variable lease payments including lease operating expenses are recorded as incurred.
Research and Development Expense	Research and Development Expenses The Company’s activities have largely consisted of research and development efforts related to developing electroporation delivery technologies and DNA immunotherapies and vaccines. Research and development expenses consist of expenses incurred in performing research and development activities including salaries and benefits, facilities and other overhead expenses, clinical trials, contract services and other outside expenses. Research and development expenses are charged to operations as they are incurred. These expenses result from the Company's independent research and development efforts as well as efforts associated with collaborations and licensing arrangements. The Company reviews and accrues clinical trial expense based on work performed, which relies on estimates of total costs incurred based on patient enrollment, completion of studies and other events. The Company follows this method since reasonably dependable estimates of the costs applicable to various stages of a research agreement or clinical trial can be made. 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.
Valuation of Intangible Assets and Goodwill	Valuation of Intangible Assets and Goodwill Intangible assets are amortized over their estimated useful lives ranging from two to 18 years. Acquired intangible assets are continuously being developed for the future economic viability contemplated at the time of acquisition. The Company is concurrently conducting preclinical studies and clinical trials using the acquired intangibles and has entered into licensing agreements for the use of these acquired intangibles. License costs are recorded based on the fair value of consideration paid and are amortized using the straight-line method over the shorter of the expected useful life of the underlying patents or the term of the related license agreement to the extent the license has an alternative future use. As of March 31, 2020 and December 31, 2019 , the Company’s intangible assets resulting from the acquisition of Inovio AS and Bioject Medical Technologies, Inc. ("Bioject"), and additional intangibles including license costs, net of accumulated amortization, totaled $3.6 million and $3.7 million , respectively. The determination of the value of intangible assets requires management to make estimates and assumptions that affect the Company’s condensed consolidated financial statements. The Company assesses potential impairments to intangible assets when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. The Company’s judgments regarding the existence of impairment indicators and future cash flows related to intangible assets are based on operational performance of its acquired businesses, market conditions and other factors. If impairment is indicated, the Company will reduce the carrying value of the intangible asset to fair value. While current and historical operating and cash flow losses are potential indicators of impairment, the Company believes the future cash flows to be received from its intangible assets will exceed the intangible assets’ carrying value, and accordingly, the Company has not recognized any impairment losses through March 31, 2020 . 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 at November 30, or more frequently if an event occurs indicating the potential for impairment. During its goodwill impairment review, the Company may assess qualitative factors to determine whether it is more likely than not 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. The Company performed its annual assessment for goodwill impairment as of November 30, 2019 , identifying no impairment. Although there are inherent uncertainties in this assessment process, the estimates and assumptions the Company is using are consistent with its internal planning. If these estimates or their related assumptions change in the future, the Company may be required to record an impairment charge on all or a portion of its goodwill and intangible assets. Furthermore, the Company cannot predict the occurrence of future impairment triggering events nor the impact such events might have on its reported asset values. Future events could cause the Company to conclude that impairment indicators exist and that goodwill or other intangible assets associated with its acquired businesses are impaired. Any resulting impairment loss could have an adverse impact on the Company’s results of operations.
Derivative Liabilities	Derivative Liabilities The Company evaluates its debt and equity issuances to determine if those contracts or embedded components of those contracts qualify as derivatives requiring separate recognition in the Company’s financial statements. The result of this accounting treatment is that the fair value of the embedded derivative is revalued at each balance sheet date and recorded as a liability, and the change in fair value during the reporting period is recorded in other income (expense) in the condensed consolidated statements of operations. In circumstances where the embedded conversion option in a convertible instrument is required to be bifurcated and there are also other embedded derivative instruments in the convertible instrument that are required to be bifurcated, the bifurcated derivative instruments are accounted for as a single, compound derivative instrument. The classification of derivative instruments, including whether such instruments should be recorded as liabilities or as equity, is reassessed at the end of each reporting period. Derivative instrument liabilities are classified in the balance sheet as current or non-current based on whether or not net-cash settlement of the derivative instrument is expected within twelve months of the balance sheet date.
Foreign Currency Translation	Foreign Currency Translation 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 gain (loss) within the statement of stockholders' equity. Exchange differences are included in general and administrative expenses in the condensed consolidated statement of operations. Non- monetary assets and liabilities measured at cost are translated at the exchange rate at the date of the transaction.
Recently Issued Accounting Standards	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. Accounting Standards Recently Adopted ASU No. 2019-12. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes . The Board issued this Update as part of its simplification initiative to improve areas of GAAP and reduce cost and complexity while maintaining usefulness. The main provision that impacts the Company is the removal of the exception to the incremental approach of intra-period tax allocation when there is a loss from continuing operations and income or gain from other items (for example, discontinued operations and other comprehensive income). ASU 2019-12 is effective for annual periods, and interim periods within those annual periods, beginning after December 15, 2020. Early adoption is permitted, including adoption in an interim period. The Company has elected to early adopt ASU 2019-12. By early adopting, ASU 2019-12 became effective as of the beginning of 2020; however, there was no cumulative effect to be recognized with the early adoption. As of March 31, 2020, there was a loss from continuing operations and a cumulative loss in other comprehensive income and there was therefore no effect on the tax provision for the period ended March 31, 2020. ASU No. 2016-13 . In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) , which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available for sale debt securities. This standard includes the Company's financial instruments, such as accounts receivable and investments that are generally of high credit quality. Previously, when credit losses were measured under GAAP, an entity generally only considered past events and current conditions in measuring the incurred loss. The new guidance requires the Company to identify, analyze, document and support new methodologies for quantifying expected credit loss estimates for its financial instruments, using information such as historical experience and current economic conditions, plus the use of reasonably supportable forecast information. The Company adopted ASU 2016-13 on January 1, 2020, and there was no material impact to its condensed consolidated financial statements. The Company will continue to monitor the impact of the coronavirus, SARS-CoV-2 (“COVID-19”) outbreak on expected credit losses. ASU No. 2018-13 . In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement , which amends certain disclosure requirements over fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statement disclosures (see Note 7 for more information about the Company’s fair value classifications). ASU No. 2018-18 . In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarified the interaction between Topic 808, Collaborative Arrangements , and Topic 606, Revenue from Contracts with Customers . The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statements. ASU 2017-04. In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). ASU 2017-04 simplifies the recognition and measurement of a goodwill impairment loss by eliminating Step 2 of the quantitative goodwill impairment test. The guidance requires a one-step impairment test in which an entity compares the fair value of a reporting unit with its carrying amount and recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, if any. ASU 2017-04 is effective for fiscal years beginning after December 15, 2019 and should be applied on a prospective basis. The Company adopted this guidance on January 1, 2020, and there was no material impact to its condensed consolidated financial statements.

Short-term Investments (Tables)

Short-term Investments (Tables)	3 Months Ended
	Mar. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Summary of Investments	The following is a summary of available-for-sale securities as of March 31, 2020 and December 31, 2019 : As of March 31, 2020 Contractual Maturity (in years) Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Mutual funds --- $ 109,616,722 $ 5,000 $ (5,055,092 ) $ 104,566,630 Corporate debt securities --- 5,175,000 — (1,202,700 ) 3,972,300 Certificates of deposit Less than 1 3,000,000 41,960 (30,000 ) 3,011,960 $ 117,791,722 $ 46,960 $ (6,287,792 ) $ 111,550,890 As of December 31, 2019 Contractual Maturity (in years) Cost Gross Unrealized Gains Gross Unrealized Losses Fair Market Value Mutual funds --- $ 66,599,219 $ 754,709 $ (15,911 ) $ 67,338,017

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the Company’s assets and liabilities that are measured at fair value on a recurring basis, and are determined using the following inputs as of March 31, 2020 : Fair Value Measurements at March 31, 2020 Total Quoted Prices in Active Markets (Level 1) Significant Other Unobservable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds $ 2,759,436 $ 2,759,436 $ — $ — Mutual funds 104,566,630 104,566,630 — — Corporate debt securities 3,972,300 — 3,972,300 — Certificates of deposit 3,011,960 — 3,011,960 — Investment in affiliated entities 21,210,745 21,210,745 — — Total assets $ 135,521,071 $ 128,536,811 $ 6,984,260 $ — Liabilities: Derivative liability (Note 9) $ 22,041,000 $ — $ — 22,041,000 Total liabilities $ 22,041,000 $ — $ — $ 22,041,000 The following table presents the Company’s assets and liabilities that are measured at fair value on a recurring basis, and are determined using the following inputs as of December 31, 2019 : Fair Value Measurements at December 31, 2019 Total Quoted Prices in Active Markets (Level 1) Significant Other Unobservable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds $ 2,349,729 $ 2,349,729 $ — $ — Mutual funds 67,338,017 67,338,017 — — Investment in affiliated entities 6,315,356 6,315,356 — — Total assets $ 76,003,102 $ 76,003,102 $ — $ — Liabilities: Derivative liability (Note 9) $ 8,819,023 $ — $ — $ 8,819,023 Total Liabilities $ 8,819,023 $ — $ — $ 8,819,023
Changes in Fair Value of the Company's Derivative Liability	The following table presents the changes in fair value of the Company's derivative liability for the three months ended March 31, 2020 : Balance at December 31, 2019 $ 8,819,023 Change in fair value 13,221,977 Balance at March 31, 2020 $ 22,041,000

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets by Major Asset Class	The following sets forth the goodwill and intangible assets by major asset class: March 31, 2020 December 31, 2019 Weighted Average Useful Life (Yrs) Gross Accumulated Amortization Net Book Value Gross Accumulated Amortization Net Book Value Indefinite lived: Goodwill(a) $ 10,513,371 $ — $ 10,513,371 $ 10,513,371 $ — $ 10,513,371 Definite lived: Licenses 10 1,323,761 (1,255,291 ) 68,470 1,323,761 (1,248,104 ) 75,657 Bioject(b) 12 5,100,000 (2,248,889 ) 2,851,111 5,100,000 (2,175,556 ) 2,924,444 Other(c) 18 4,050,000 (3,412,500 ) 637,500 4,050,000 (3,356,250 ) 693,750 Total intangible assets 11 10,473,761 (6,916,680 ) 3,557,081 10,473,761 (6,779,910 ) 3,693,851 Total goodwill and intangible assets $ 20,987,132 $ (6,916,680 ) $ 14,070,452 $ 20,987,132 $ (6,779,910 ) $ 14,207,222 (a) Goodwill was recorded from the Inovio AS acquisition in January 2005, the acquisition of VGX in June 2009 and the acquisition of Bioject in April 2016 for $3.9 million , $6.2 million and $400,000 , respectively. (b) Bioject intangible assets represent the estimated fair value of developed technology and intellectual property which were recorded from the Bioject asset acquisition. (c) Other intangible assets represent the estimated fair value of acquired intellectual property from the Inovio AS acquisition.

Convertible Debt (Tables)

Convertible Debt (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Schedule of Convertible Debt	The balance of the August 2019 Bonds at March 31, 2020 is as follows: Principal amount $ 14,767,171 Unamortized debt discount (5,980,204 ) Unamortized debt issuance cost (225,603 ) Accretion of premium associated with the August 2019 Bonds 357,994 Accrued interest 36,918 Net carrying amount $ 8,956,276 The balance of the Notes at March 31, 2020 is as follows: Principal amount $ 78,500,000 Unamortized debt discount on the liability component (13,356,690 ) Unamortized debt issuance cost (1,838,336 ) Accrued interest 425,208 Net carrying amount $ 63,730,182 The balance of the December 2019 Bonds at March 31, 2020 is as follows: Principal amount $ 3,855,872 Unamortized debt issuance cost (43,740 ) Accretion of premium associated with the December 2019 Bonds 46,988 Accrued interest 9,747 Net carrying amount $ 3,868,867
Schedule of Maturities of Long-term Debt	As of March 31, 2020 , future minimum payments due under the Company's convertible debt instruments are as follows: Convertible Notes (1) August 2019 Bonds (2) December 2019 Bonds (2) Total Remainder of 2020 $ 2,551,000 $ 111,000 $ 29,000 $ 2,691,000 2021 5,103,000 148,000 39,000 5,290,000 2022 5,103,000 148,000 39,000 5,290,000 2023 5,103,000 148,000 39,000 5,290,000 2024 81,051,000 19,789,000 5,176,000 106,016,000 Total $ 98,911,000 $ 20,344,000 $ 5,322,000 $ 124,577,000 (1) Amounts represent contractual amounts due under the Notes, including interest based on the fixed rate of 6.5% per year. (2) Amounts represent contractual amounts due under the August 2019 and December 2019 Bonds, including interest based on the fixed rate of 1% per year plus a premium on such bonds to provide an internal rate of return with respect to such Bonds of 6% at maturity.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2020
Stockholders' Equity Note [Abstract]
Summary of Common and Preferred Stock Authorized, Issued and Outstanding	The following is a summary of the Company's authorized and issued common and preferred stock as of March 31, 2020 and December 31, 2019 : Outstanding as of Authorized Issued March 31, 2020 December 31, 2019 Common Stock, par value $0.001 per share 600,000,000 145,915,100 145,915,100 101,361,034 Series C Preferred Stock, par value $0.001 per share 1,091 1,091 23 23

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table summarizes potential shares of common stock that were excluded from the diluted net loss per share calculation because of their anti-dilutive effect for the three months ended March 31, 2020 and 2019 : Common Stock Equivalents 2020 2019 Options to purchase common stock 9,615,986 11,027,600 Restricted stock units 2,667,710 1,720,128 Convertible preferred stock 8,456 8,456 Convertible notes 14,585,653 14,585,653 August 2019 Bonds 4,928,859 — December 2019 Bonds 1,009,450 — Total 32,816,114 27,341,837

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Weighted Average Assumptions	The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below: Three Months Ended March 31, 2020 2019 Risk-free interest rate 0.74% 2.44% Expected volatility 76% 70% Expected life in years 5.9 6.2 Dividend yield — —

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	As of March 31, 2020 , the maturities of the Company's operating lease liabilities were as follows: Remainder of 2020 $ 2,920,000 2021 3,968,000 2022 4,045,000 2023 4,023,000 2024 3,001,000 Thereafter 12,951,000 Total remaining lease payments 30,908,000 Less: present value adjustment (8,941,000 ) Total operating lease liabilities 21,967,000 Less: current portion (2,132,000 ) Long-term operating lease liabilities $ 19,835,000 Weighted-average remaining lease term 8.0 years Weighted-average discount rate 8.4 %

Basis of Presentation (Details)

Basis of Presentation (Details)	Dec. 26, 2019USD ($)	Aug. 01, 2019USD ($)	Mar. 01, 2019USD ($)	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019KRW (₩)	Dec. 26, 2019KRW (₩)	Aug. 01, 2019KRW (₩)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net loss				$ 32,541,054	$ 29,219,262
Working capital				243,200,000
Retained earnings (accumulated deficit)				(772,326,709)		$ (739,785,655)
Cash, cash equivalents, and short-term investments				270,000,000
Long-term investments				21,200,000
Proceeds from issuance of stock				208,241,933	$ 907,330
Common stock | Sales Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of stock				208,200,000		9,100,000
6.50% Convertible Senior Notes Due 2024
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Principal amount				$ 78,500,000
6.50% Convertible Senior Notes Due 2024 | Convertible Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of debt			$ 75,700,000			$ 75,700,000
Stated interest rate			6.50%	6.50%		6.50%	6.50%
Principal amount			$ 78,500,000	$ 78,500,000
August 2019 Convertible Bonds
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Principal amount				$ 14,767,171
August 2019 Convertible Bonds | Convertible Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of debt		$ 14,500,000				$ 14,500,000
Stated interest rate		1.00%		1.00%		1.00%	1.00%		1.00%
Principal amount		$ 15,000,000				$ 15,000,000	₩ 18,000,000,000		₩ 18,000,000,000
December 2019 Convertible Bonds
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Principal amount				$ 3,855,872
December 2019 Convertible Bonds | Convertible Debt
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Proceeds from issuance of debt	$ 4,000,000					$ 4,000,000
Stated interest rate	1.00%			1.00%		1.00%	1.00%	1.00%
Principal amount	$ 4,100,000					$ 4,100,000	₩ 4,700,000,000	₩ 4,700,000,000
Geneos Therapeutics, Inc.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-controlling interest				48.00%
VGX Animal Health, Inc
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-controlling interest				15.00%

Critical Accounting Policies (D

Critical Accounting Policies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net	$ 3,557,081	$ 3,693,851
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	18 years

Revenue Recognition (Details)

Revenue Recognition (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,327,274	$ 2,829,905
Revenue recognized from deferred revenue beginning balance	58,000
Plumbline Life Sciences
Disaggregation of Revenue [Line Items]
Total revenues	1,100,000
AstraZeneca
Disaggregation of Revenue [Line Items]
Total revenues	72,000	$ 2,700,000
Other Counterparty
Disaggregation of Revenue [Line Items]
Total revenues	$ 115,000

Short-term Investments - Narrat

Short-term Investments - Narrative (Details)	3 Months Ended
	Mar. 31, 2020USD ($)investment	Mar. 31, 2019USD ($)
Investments, Debt and Equity Securities [Abstract]
Realized gain on investments	$ 50,000	$ 18,000
Realized loss on investments	525,000	53,000
Equity securities, unrealized gain (loss)	$ (5,100,000)	$ 0
Number of securities in a gross unrealized loss position | investment	25
Number of securities in a gross unrealized loss position for more than twelve months | investment	2
Unrealized loss	$ 560,000

Short-term Investments - Summar

Short-term Investments - Summary of Available-for-sale Securities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Abstract]
Cost	$ 117,791,722
Gross unrealized gains	46,960
Gross unrealized losses	(6,287,792)
Fair market value	111,550,890
Mutual funds
Debt Securities, Available-for-sale [Abstract]
Cost	109,616,722	$ 66,599,219
Gross unrealized gains	5,000	754,709
Gross unrealized losses	(5,055,092)	(15,911)
Fair market value	104,566,630	$ 67,338,017
Corporate securities
Debt Securities, Available-for-sale [Abstract]
Cost	5,175,000
Gross unrealized gains	0
Gross unrealized losses	(1,202,700)
Fair market value	$ 3,972,300
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Contractual maturity (less than)	1 year
Debt Securities, Available-for-sale [Abstract]
Cost	$ 3,000,000
Gross unrealized gains	41,960
Gross unrealized losses	(30,000)
Fair market value	$ 3,011,960

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	$ 111,550,890
Investment in affiliated entities	21,210,745	$ 6,315,356
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	22,041,000	8,819,023
Significant Unobservable Inputs (Level 3)
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	7,100,000
Mutual funds
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	104,566,630	67,338,017
Corporate securities
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	3,972,300
Certificates of deposit
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	3,011,960
Fair Value, Measurements, Recurring
Financial assets and liabilities that are measured at fair value on recurring basis
Investment in affiliated entities	21,210,745	6,315,356
Total assets	135,521,071	76,003,102
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	22,041,000	8,819,023
Total liabilities	22,041,000	8,819,023
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Investment in affiliated entities	21,210,745	6,315,356
Total assets	128,536,811	76,003,102
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Investment in affiliated entities	0	0
Total assets	6,984,260	0
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Investment in affiliated entities	0	0
Total assets	0	0
Liabilities, Fair Value Disclosure [Abstract]
Derivative liability (Note 9)	22,041,000	8,819,023
Total liabilities	22,041,000	8,819,023
Fair Value, Measurements, Recurring | Money market funds
Financial assets and liabilities that are measured at fair value on recurring basis
Cash and cash equivalents, fair value	2,759,436	2,349,729
Fair Value, Measurements, Recurring | Money market funds | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Cash and cash equivalents, fair value	2,759,436	2,349,729
Fair Value, Measurements, Recurring | Money market funds | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Cash and cash equivalents, fair value	0	0
Fair Value, Measurements, Recurring | Money market funds | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Cash and cash equivalents, fair value	0	0
Fair Value, Measurements, Recurring | Mutual funds
Financial assets and liabilities that are measured at fair value on recurring basis
Cash and cash equivalents, fair value	104,566,630	67,338,017
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
Cash and cash equivalents, fair value	104,566,630	67,338,017
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
Cash and cash equivalents, fair value	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
Cash and cash equivalents, fair value	0	$ 0
Fair Value, Measurements, Recurring | Corporate securities
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	3,972,300
Fair Value, Measurements, Recurring | Corporate securities | Quoted Prices in Active Markets (Level 1)
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	0
Fair Value, Measurements, Recurring | Corporate securities | Significant Other Unobservable Inputs (Level 2)
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	3,972,300
Fair Value, Measurements, Recurring | Corporate securities | Significant Unobservable Inputs (Level 3)
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	0
Fair Value, Measurements, Recurring | Certificates of deposit
Financial assets and liabilities that are measured at fair value on recurring basis
Debt securities, available for sale	3,011,960
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
Debt securities, available for sale	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
Debt securities, available for sale	3,011,960
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
Debt securities, available for sale	$ 0

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Marketable Securities and Fair Value Measurements (Textual) [Abstract]
Derivative liability	$ 22,041,000	$ 8,819,023
Using Quoted Prices in Active Markets for Identical Assets (Level 1)
Marketable Securities and Fair Value Measurements (Textual) [Abstract]
Number of shares held in an affiliated entity (in shares)	1,644,155
Using Quoted Prices in Active Markets for Identical Assets (Level 1) | Common stock
Marketable Securities and Fair Value Measurements (Textual) [Abstract]
Investment owned (in shares)	597,808
Fair Value, Inputs, Level 3
Marketable Securities and Fair Value Measurements (Textual) [Abstract]
Derivative liability	$ 7,100,000

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of the Company's Derivative Liability (Details)	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 8,819,023,000
Change in fair value	13,221,977,000
Ending balance	$ 22,041,000,000

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule Goodwill and Intangible Assets (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Apr. 30, 2016	Jun. 30, 2009	Jan. 31, 2005
Indefinite lived:
Goodwill, gross	$ 10,513,371	$ 10,513,371
Goodwill, net book value	10,513,371	10,513,371
Definite lived:
Intangible assets, gross	10,473,761	10,473,761
Intangible assets, accumulated amortization	(6,916,680)	(6,779,910)
Intangible assets, net book value	3,557,081	3,693,851
Total goodwill and intangible assets, gross	20,987,132	20,987,132
Total goodwill and intangible assets, net book value	14,070,452	14,207,222
Inovio AS
Indefinite lived:
Goodwill, net book value					$ 3,900,000
VGX
Indefinite lived:
Goodwill, net book value				$ 6,200,000
Bioject
Indefinite lived:
Goodwill, net book value			$ 400,000
Licenses
Definite lived:
Intangible assets, gross	1,323,761	1,323,761
Intangible assets, accumulated amortization	(1,255,291)	(1,248,104)
Intangible assets, net book value	68,470	75,657
Bioject
Definite lived:
Intangible assets, gross	5,100,000	5,100,000
Intangible assets, accumulated amortization	(2,248,889)	(2,175,556)
Intangible assets, net book value	2,851,111	2,924,444
Other
Definite lived:
Intangible assets, gross	4,050,000	4,050,000
Intangible assets, accumulated amortization	(3,412,500)	(3,356,250)
Intangible assets, net book value	$ 637,500	$ 693,750
Weighted Average
Definite lived:
Useful life	11 years
Weighted Average | Licenses
Definite lived:
Useful life	10 years
Weighted Average | Bioject
Definite lived:
Useful life	12 years
Weighted Average | Other
Definite lived:
Useful life	18 years

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Aggregate amortization expense on intangible assets	$ 136,770	$ 266,563
Estimated aggregate amortization expense for remainder of 2020	410,000
Estimated aggregate amortization expense for 2021	520,000
Estimated aggregate amortization expense for 2022	493,000
Estimated aggregate amortization expense for 2023	276,000
Estimated aggregate amortization expense for 2024	253,000
Estimated aggregate amortization expense for 2025	$ 1,600,000

Convertible Debt - Narrative (D

Convertible Debt - Narrative (Details)	Jan. 02, 2020	Dec. 26, 2019USD ($)$ / shares	Aug. 01, 2019USD ($)$ / shares	Mar. 01, 2019USD ($)	Mar. 31, 2020USD ($)day$ / shares	Mar. 31, 2019USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019KRW (₩)	Dec. 26, 2019KRW (₩)	Aug. 01, 2019KRW (₩)
Debt Instrument [Line Items]
Debt instrument, convertible conversion price (in dollars per share) | $ / shares					$ 5.38
Debt instrument, convertible, threshold percentage of stock price trigger					130.00%
Debt instrument, convertible, threshold trading days | day					20
Debt instrument, convertible, threshold consecutive trading days | day					30
Debt instrument, redemption price percentage					100.00%
Debt instrument, convertible, carrying amount of equity component					$ 62,200,000
Unamortized debt issuance cost					2,800,000
Non-cash interest expense					2,803,755	$ 656,248
Derivative liability					22,041,000		$ 8,819,023
Change in fair value of derivative liability					(13,221,977)	$ 0
December 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount					3,855,872
Unamortized debt issuance cost					$ 43,740
December 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Principal amount		$ 4,100,000					$ 4,100,000	₩ 4,700,000,000	₩ 4,700,000,000
Stated interest rate		1.00%			1.00%		1.00%	1.00%	1.00%
Proceeds from issuance of debt		$ 4,000,000					$ 4,000,000
Debt instrument, convertible, conversion ratio		0.0002147766
Debt instrument, effective interest rate					6.20%
Non-cash interest expense					$ 62,000
Interest expense, contractual interest					$ 10,000
Debt instrument, convertible, internal rate of return		6.00%			6.00%				6.00%
Debt instrument, convertible, required bondholder approval, percentage		25.00%
August 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount					$ 14,767,171
Unamortized debt issuance cost					225,603
Debt instrument, unamortized discount					$ 5,980,204
August 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Principal amount			$ 15,000,000				$ 15,000,000	₩ 18,000,000,000		₩ 18,000,000,000
Stated interest rate			1.00%		1.00%		1.00%	1.00%		1.00%
Proceeds from issuance of debt			$ 14,500,000				$ 14,500,000
Debt instrument, convertible, conversion ratio	0.0002738255		0.0002110595
Debt instrument, convertible, carrying amount of equity component			$ 7,100,000
Debt instrument, unamortized discount			$ 7,300,000
Debt instrument, effective interest rate					29.40%
Non-cash interest expense					$ 641,000
Interest expense, contractual interest					$ 38,000
Debt instrument, convertible, internal rate of return			6.00%		6.00%					6.00%
Debt instrument, convertible, required bondholder approval, percentage			25.00%
Derivative liability					$ 22,000,000
Change in fair value of derivative liability					13,200,000
6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Principal amount					78,500,000
Unamortized debt issuance cost					1,838,336
Debt instrument, unamortized discount				$ 18,600,000	$ 13,356,690
Debt instrument, effective interest rate					13.10%
Non-cash interest expense					$ 2,100,000
Interest expense, contractual interest					1,300,000
6.50% Convertible Senior Notes Due 2024 | Convertible Debt
Debt Instrument [Line Items]
Principal amount				$ 78,500,000	$ 78,500,000
Stated interest rate				6.50%	6.50%		6.50%	6.50%
Proceeds from issuance of debt				$ 75,700,000			$ 75,700,000
Debt instrument, convertible, conversion ratio				0.1858045
Initial Conversion Price | December 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible conversion price (in dollars per share) | $ / shares		$ 4
Initial Conversion Price | August 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible conversion price (in dollars per share) | $ / shares			$ 4
Event Of Default | August 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible, internal rate of return			8.00%							8.00%
Maximum | December 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio		0.0003579611
Maximum | August 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible, conversion ratio			0.0003517658
Debt instrument, convertible conversion price (in dollars per share) | $ / shares			$ 3.15
Maximum | After January 2, 2020 Conversion Price | August 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible conversion price (in dollars per share) | $ / shares			$ 2.40
Maximum | After July 2, 2020 Conversion Price | December 2019 Convertible Bonds | Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible conversion price (in dollars per share) | $ / shares		$ 2.40

Convertible Debt - Balance of C

Convertible Debt - Balance of Convertible Bonds and Notes (Details)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2019KRW (₩)	Dec. 26, 2019USD ($)	Dec. 26, 2019KRW (₩)	Aug. 01, 2019USD ($)	Aug. 01, 2019KRW (₩)	Mar. 01, 2019USD ($)
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ (2,800,000)
6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Principal amount	78,500,000
Unamortized debt discount	(13,356,690)							$ (18,600,000)
Unamortized debt issuance cost	(1,838,336)
Accrued interest	425,208
Total	63,730,182
August 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount	14,767,171
Unamortized debt discount	(5,980,204)
Unamortized debt issuance cost	(225,603)
Accretion of premium associated with the Bonds	357,994
Accrued interest	36,918
Total	8,956,276
December 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount	3,855,872
Unamortized debt issuance cost	(43,740)
Accretion of premium associated with the Bonds	46,988
Accrued interest	9,747
Total	3,868,867
Convertible Debt
Debt Instrument [Line Items]
Total	124,577,000
Convertible Debt | 6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Principal amount	78,500,000							$ 78,500,000
Total	98,911,000
Convertible Debt | August 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount		$ 15,000,000	₩ 18,000,000,000			$ 15,000,000	₩ 18,000,000,000
Unamortized debt discount						$ (7,300,000)
Total	20,344,000
Convertible Debt | December 2019 Convertible Bonds
Debt Instrument [Line Items]
Principal amount		$ 4,100,000	₩ 4,700,000,000	$ 4,100,000	₩ 4,700,000,000
Total	$ 5,322,000

Convertible Debt - Schedule of

Convertible Debt - Schedule of Maturities (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Dec. 26, 2019	Aug. 01, 2019	Mar. 01, 2019
6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Total	$ 63,730,182
August 2019 Convertible Bonds
Debt Instrument [Line Items]
Total	8,956,276
December 2019 Convertible Bonds
Debt Instrument [Line Items]
Total	3,868,867
Convertible Debt
Debt Instrument [Line Items]
Remainder of 2020	2,691,000
2021	5,290,000
2022	5,290,000
2023	5,290,000
2024	106,016,000
Total	124,577,000
Convertible Debt | 6.50% Convertible Senior Notes Due 2024
Debt Instrument [Line Items]
Remainder of 2020	2,551,000
2021	5,103,000
2022	5,103,000
2023	5,103,000
2024	81,051,000
Total	$ 98,911,000
Stated interest rate	6.50%	6.50%			6.50%
Convertible Debt | August 2019 Convertible Bonds
Debt Instrument [Line Items]
Remainder of 2020	$ 111,000
2021	148,000
2022	148,000
2023	148,000
2024	19,789,000
Total	$ 20,344,000
Stated interest rate	1.00%	1.00%		1.00%
Debt instrument, convertible, internal rate of return	6.00%			6.00%
Convertible Debt | December 2019 Convertible Bonds
Debt Instrument [Line Items]
Remainder of 2020	$ 29,000
2021	39,000
2022	39,000
2023	39,000
2024	5,176,000
Total	$ 5,322,000
Stated interest rate	1.00%	1.00%	1.00%
Debt instrument, convertible, internal rate of return	6.00%		6.00%

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Authorized and Issued Common and Preferred Stock (Details) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Summary of common and preferred stock authorized, issued and outstanding
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares, authorized (in shares)	600,000,000
Common stock, shares, issued (in shares)	145,915,100
Common stock, shares, outstanding (in shares)	145,915,100	101,361,034
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)	23	23

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
	May 31, 2018	Mar. 31, 2020	Jan. 01, 2020	May 13, 2016
2016 Incentive Plan
Class of Stock [Line Items]
Number of shares authorized (in shares)		18,000,000		18,000,000
Number of potential shares authorized for issuance under share based compensation plan (in shares)				2,000,000
Increase in number of shares authorized (in shares)			2,000,000
Number of shares available for grant (in shares)		7,536,221
Number of shares of unvested restricted stock units and options outstanding (in shares)		2,667,710
Common stock, other shares, outstanding (in shares)		5,631,777
Award vesting period		3 years
Maximum contractual term		10 years
2007 Incentive Plan
Class of Stock [Line Items]
Common stock, other shares, outstanding (in shares)		3,984,209
Award vesting period		3 years
Maximum contractual term		10 years
Common stock | Sales Agreement
Class of Stock [Line Items]
Maximum authorized amount	$ 100,000,000	$ 250,000,000
Agent fee	3.00%
Aggregate number of shares issued (in shares)		43,148,952
Stock sale agreement weighted average price per share		$ 4.92
Aggregate proceeds		$ 208,200,000
Stock sales agreement, remaining authorized sales amount		$ 150,000,000

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Anti-Dilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	32,816,114	27,341,837
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	9,615,986	11,027,600
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	2,667,710	1,720,128
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	8,456	8,456
6.50% Convertible Senior Notes Due 2024 | Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	14,585,653	14,585,653
August 2019 Convertible Bonds | Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	4,928,859	0
December 2019 Convertible Bonds | Convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded (in shares)	1,009,450	0

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 4,001,553	$ 3,432,796
Total unrecognized compensation cost related to unvested stock options	$ 8,000,000
Period over which total unrecognized compensation cost related to unvested stock options will be recognized	2 years 5 months 30 days
Weighted average grant date fair value (in dollars per share)	$ 5.37	$ 2.19
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost related to unvested stock options	$ 13,900,000
Period over which total unrecognized compensation cost related to unvested stock options will be recognized	2 years 7 months
Weighted average grant date fair value, restricted stock units (in dollars per share)	$ 8.32	$ 3.38
Employees and Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,600,000	$ 3,200,000
Employees and Directors | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.74%	2.44%
Expected volatility	76.00%	70.00%
Expected life in years	5 years 11 months	6 years 2 months
Dividend yield	0.00%	0.00%
Non Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 383,000	$ 274,000
Research and Development Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	2,300,000	1,900,000
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense	$ 1,300,000	$ 1,300,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	1 Months Ended				3 Months Ended		12 Months Ended
	Nov. 30, 2016	Mar. 31, 2016	Jan. 31, 2016	May 31, 2015	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2013	Dec. 31, 2010	Feb. 20, 2020	Dec. 31, 2019
Related-Party Transactions (Textual) [Abstract]
Long-term other assets					$ 2,480,087					$ 2,672,024
GeneOne Life Sciences
Related-Party Transactions (Textual) [Abstract]
Investment owned (in shares)					1,644,155
Payment received for license granted								$ 3,000,000
Term							20 years
Milestone-based ownership target			35.00%	35.00%
Revenue from related parties					$ 31,000	$ 31,000
Operating expenses related to affiliated entity					606,000	1,100,000
Accounts receivable					3,000					128,000
Accounts payable and accrued liability					2,000					511,000
Long-term other assets					294,000					284,000
Director
Related-Party Transactions (Textual) [Abstract]
Term		5 years
Revenue from related parties						838,000
Operating expenses related to affiliated entity					362,000	487,000
Accounts receivable					626,000					616,000
Expenses to reimburse		$ 3,100,000
Awarded amount	$ 6,100,000
Contra-research and development expense					619,000
Accounts payable/accrued liabilities					262,000					219,000
Deferred grant funding, from affiliate					794,000
Plumbline Life Sciences
Related-Party Transactions (Textual) [Abstract]
Revenue from related parties						$ 24,000
Accounts receivable					$ 5,000					$ 589,000
Ownership percentage									19.90%
Plumbline Life Sciences | Available-for-sale Securities
Related-Party Transactions (Textual) [Abstract]
Investment owned (in shares)					597,808
Investment owned, additional shares acquired (in shares)									202,050

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)ft²	Mar. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Lease cost | $	$ 834	$ 817
San Diego, California
Lessee, Lease, Description [Line Items]
Area leased (in square feet)	82,200
Plymouth Meeting, Pennsylvania
Lessee, Lease, Description [Line Items]
Area leased (in square feet)	57,360
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease term	3 years 8 months 12 days
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease term	9 years 9 months 19 days

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Remainder of 2020	$ 2,920,000
2021	3,968,000
2022	4,045,000
2023	4,023,000
2024	3,001,000
Thereafter	12,951,000
Total remaining lease payments	30,908,000
Less: present value adjustment	(8,941,000)
Total operating lease liabilities	21,967,000
Less: current portion	(2,132,045)	$ (2,074,842)
Long-term operating lease liabilities	$ 19,834,770	$ 20,409,922
Weighted-average remaining lease term	8 years
Weighted-average discount rate	8.40%

Collaborative Agreements (Detai

Collaborative Agreements (Details)

Apr. 11, 2018USD ($)

Dec. 31, 2017USD ($)

Dec. 29, 2017

Aug. 07, 2015product

Mar. 31, 2020USD ($)

Jan. 31, 2020USD ($)

Aug. 30, 2019USD ($)

Oct. 31, 2018USD ($)

Mar. 31, 2018USD ($)

Sep. 30, 2015USD ($)

Mar. 31, 2020USD ($)

Mar. 31, 2019USD ($)

Jun. 30, 2018USD ($)

Dec. 31, 2019USD ($)

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenues

$ 1,327,274

$ 2,829,905

Grant funding liability

$ 13,091,424

13,091,424

$ 6,065,212

AstraZeneca

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenues

72,000

2,700,000

Collaborative Arrangement, Product | ApolloBio

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Territory expansion option period

3 years

Proceeds received in upfront payment

$ 19,400,000

Upfront payment received

23,000,000

23,000,000

$ 23,000,000

Advisory fees

960,000

Additional revenue to be achieved

$ 20,000,000

Royalty period

10 years

Period from effective date for termination

1 year

Number of days written notice before termination

90 days

Collaborative Arrangement, Product | AstraZeneca

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Upfront payment received

$ 27,500,000

$ 27,500,000

Anticipated development and regulatory event based payment receivable milestones

$ 125,000,000

Anticipated commercial event based payment receivable milestones

115,000,000

Number of additional products to be developed | product

2

Deferred revenue

62,000

62,000

Foreign Tax Authority | Collaborative Arrangement, Product | ApolloBio

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Foreign corporate income taxes reducing upfront payment

2,200,000

Foreign non-corporate income taxes reducing upfront payment

$ 1,400,000

Lassa Fever And MERS Vaccine | Collaborative Arrangement, Product | Coalition for Epidemic Preparedness Innovations

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

Funding received for research and development

987,000

1,700,000

Grant funding liability

4,400,000

4,400,000

SARS-CoV-2/COVID-19 Vaccine | Collaborative Arrangement, Product | Coalition for Epidemic Preparedness Innovations

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Collaborative agreement, funding to be received

$ 9,000,000

Funding received for research and development

2,400,000

Grant funding liability

2,900,000

2,900,000

DNA-Encoded Monoclonal Antibody Technology | Collaborative Arrangement, Product | Bill And Melinda Gates Foundation

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Funding received for research and development

$ 1,100,000

$ 2,200,000

134,000

$ 1,100,000

Grant funding liability

892,000

892,000

CELLECTRA 3PSP Proprietary Smart Device | Collaborative Arrangement, Product | Bill And Melinda Gates Foundation

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Funding received for research and development

5,000,000

64,000

Grant funding liability

$ 4,900,000

$ 4,900,000

Geneos Therapeutics, Inc. (Deta

Geneos Therapeutics, Inc. (Details) - USD ($) $ in Millions	1 Months Ended
	Jan. 31, 2020	Feb. 28, 2019	Mar. 31, 2020
Geneos Therapeutics, Inc.
Noncontrolling Interest [Line Items]
Sale of stock, consideration received		$ 4.5
Geneos Therapeutics, Inc.
Noncontrolling Interest [Line Items]
Payments to acquire additional interest in subsidiaries	$ 3	$ 1.2
Stock purchase agreement, commitment of additional investment	$ 0.8
Noncontrolling interest, ownership percentage by parent			52.00%

Subsequent Events (Details)

Subsequent Events (Details) - USD ($)	Apr. 03, 2020	May 08, 2020	May 31, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Subsequent Event [Line Items]
Proceeds from issuance of common stock, net of issuance costs				$ 208,241,933	$ 907,330
Common stock | Sales Agreement
Subsequent Event [Line Items]
Maximum authorized amount			$ 100,000,000	250,000,000
Agent fee			3.00%
Proceeds from issuance of common stock, net of issuance costs				$ 208,200,000		$ 9,100,000
Common stock | Sales Agreement | Subsequent Events
Subsequent Event [Line Items]
Maximum authorized amount	$ 150,000,000
Agent fee	3.00%
Number of common shares sold (in shares)		12,041,178
Proceeds from issuance of common stock, net of issuance costs		$ 121,700,000
Common shares sold (in dollars per share)		$ 10.26