Aceragen (ACGN) 10-Q 29 Apr 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 29, 2021
Document and Entity Information
Document Type	10-Q
Document Period End Date	Mar. 31, 2021
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-31918
Entity Registrant Name	IDERA PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3072298
Entity Address, Address Line One	505 Eagleview Blvd., Suite 212
Entity Address, City or Town	Exton
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19341
City Area Code	484
Local Phone Number	348-1600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	IDRA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		50,033,297
Entity Central Index Key	0000861838
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 44,541	$ 33,229
Short-term investments		4,499
Prepaid expenses and other current assets	2,477	3,627
Total current assets	47,018	41,355
Property and equipment, net	38	44
Operating lease right-of-use assets	882	930
Other assets	70	70
Total assets	48,008	42,399
Current liabilities:
Accounts payable	185	329
Accrued expenses	4,398	6,072
Operating lease liability	196	191
Other current liability	217	435
Total current liabilities	4,996	7,027
Warrant liability, long-term		6,983
Future tranche right liability, long-term		118,803
Operating lease liability, net of current portion	708	758
Total liabilities	5,704	133,571
Commitments and contingencies (Note 13)
Stockholders' equity (deficit):
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 46,537 and 38,291 at March 31, 2021 and December 31, 2020, respectively	46	38
Additional paid-in capital	760,072	742,342
Accumulated deficit	(717,814)	(833,552)
Total stockholders' equity (deficit)	42,304	(91,172)
Total liabilities and stockholders' equity (deficit)	48,008	42,399
Series B1 Redeemable Convertible Preferred Stock
Stockholders' equity (deficit):
Preferred stock
Series A Convertible Preferred Stock
Stockholders' equity (deficit):
Preferred stock

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	140,000,000	140,000,000
Common stock, shares issued	46,537,000	38,291,000
Common stock, shares outstanding	46,537,000	38,291,000
Series B1 Redeemable Convertible Preferred Stock
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated	278,000	278,000
Preferred stock, shares issued	10,000	24,000
Preferred stock, shares outstanding	10,000	24,000
Common stock, shares outstanding	10,000	24,000
Series A Convertible Preferred Stock
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated	1,500,000	1,500,000
Preferred stock, shares issued	1,000	1,000
Preferred stock, shares outstanding	1,000	1,000

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 6,871	$ 9,510
General and administrative	3,156	3,642
Total operating expenses	10,027	13,152
Loss from operations	(10,027)	(13,152)
Other income (expense):
Interest income	3	125
Interest expense	(3)
Warrant revaluation gain	6,983	1,101
Future tranche right revaluation gain	118,803	20,711
Foreign currency exchange (loss) gain	(21)	32
Net income	115,738	8,817
Net loss attributable to common stockholders	109,606	8,178
Net income (loss) applicable to common stockholders (Note 12)
Net income applicable to common stockholders - basic	109,606	8,178
Net income attributable to common stockholders - diluted	$ (10,048)	$ 7,199
Net income (loss) per share applicable to common stockholders (Note 12)
Basic	$ 2.66	$ 0.27
Diluted	$ (0.14)	$ 0.22
Weighted-average number of common shares used in computing net income (loss) per share applicable to common stockholders
Basic	41,193	30,300
Diluted	70,980	33,010

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities:
Net income	$ 115,738	$ 8,817
Adjustments to reconcile net income to net cash used in operating activities:
Stock-based compensation	1,111	750
Warrant liability revaluation gain	(6,983)	(1,101)
Future tranche right liability revaluation gain	(118,803)	(20,711)
Issuance of common stock for services rendered	67	26
Accretion of discounts on short-term investments	(1)	(18)
Depreciation and amortization expense	6	24
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,150	1,313
Accounts payable, accrued expenses, and other liabilities	(1,879)	148
Other	3	4
Net cash used in operating activities	(9,591)	(10,748)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities		(5,535)
Proceeds from maturity of available-for-sale securities	4,500	2,749
Purchases of property and equipment		(7)
Net cash provided by (used in) investing activities	4,500	(2,793)
Cash Flows from Financing Activities:
Proceeds from common stock financings, net	16,322	1,406
Proceeds from employee stock purchases	28	25
Proceeds from exercise of common stock options and warrants	271
Payments on seller-financed purchases	(218)
Net cash provided by financing activities	16,403	1,431
Net increase (decrease) in cash and cash equivalents	11,312	(12,110)
Cash and cash equivalent, beginning of period	33,229	40,019
Cash and cash equivalents, end of period	44,541	27,909
Supplemental disclosure of cash flow information:
Cash paid for interest	3
Supplemental disclosure of non-cash financing and investing activities:
Offering costs in accounts payable and accrued expenses	$ 61	$ 260

CONDENSED STATEMENTS OF REDEEMA

CONDENSED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' DEFICIT - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Series B1 Redeemable Convertible Preferred Stock	Total
Beginning balance at Dec. 31, 2019	$ 30	$ 709,692	$ (720,890)		$ (11,168)
Beginning balance (in shares) at Dec. 31, 2019	29,672,000			24,000
Sale of common stock, net of issuance costs	$ 1	1,405			1,406
Sale of common stock, net of issuance costs (in shares)	854,000
Issuance of common stock under equity incentive plan (vesting of restricted stock units (in shares)	48,000
Issuance of common stock under employee stock purchase plan		25			25
Issuance of common stock under employee stock purchase plan (in shares)	19,000
Issuance of common stock for services rendered		26			26
Issuance of common stock for services rendered (in shares)	14,000
Stock-based compensation expense		750			750
Net income			8,817		8,817
Ending balance at Mar. 31, 2020	$ 31	711,898	(712,073)		(144)
Ending balance (in shares) at Mar. 31, 2020	30,607,000			24,000
Beginning balance at Dec. 31, 2020	$ 38	742,342	(833,552)		$ (91,172)
Beginning balance (in shares) at Dec. 31, 2020	38,291,000			24,000	38,291,000
Sale of common stock, net of issuance costs	$ 3	16,258			$ 16,261
Sale of common stock, net of issuance costs (in shares)	3,195,000
Issuance of common stock under equity incentive plan (vesting of restricted stock units (in shares)	237,000
Issuance of common stock under employee stock purchase plan		28			28
Issuance of common stock under employee stock purchase plan (in shares)	8,000
Issuance of common stock upon exercise of common stock options and warrants	$ 4	267			271
Issuance of common stock upon exercise of common stock options and warrants (in shares)	3,375,000
Issuance of common stock for services rendered		67			67
Issuance of common stock for services rendered (in shares)	16,000
Stock-based compensation expense		1,111			1,111
Conversion of preferred stock to common	$ 1	(1)
Conversion of preferred stock to common (in shares)	1,415,000			(14,150)
Net income			115,738		115,738
Ending balance at Mar. 31, 2021	$ 46	$ 760,072	$ (717,814)		$ 42,304
Ending balance (in shares) at Mar. 31, 2021	46,537,000			10,000	46,537,000

Business and Organization

Business and Organization	3 Months Ended
	Mar. 31, 2021
Business and Organization
Business and Organization	Note 1. Business and Organization ​ Business Overview ​ Idera Pharmaceuticals, Inc. (“Idera” or the “Company”), a Delaware corporation, is a clinical-stage biopharmaceutical company with a business strategy focused on the clinical development, and ultimately the commercialization, of drug candidates for both oncology and rare disease indications characterized by small, well-defined patient populations with serious unmet medical needs. The Company’s current focus is on its Toll-like receptor (“TLR”) agonist, tilsotolimod (IMO-2125), for oncology. The Company is currently seeking to develop and commercialize targeted therapies on its own. To the extent the Company seeks to develop drug candidates for broader disease indications, it has entered into and may explore additional collaborative alliances to support development and commercialization. ​ Liquidity and Financial Condition ​ As of March 31, 2021, the Company had an accumulated deficit of $717.8 million and a cash and cash equivalents balance of $44.5 million. The Company expects to incur substantial operating losses in future periods and will require additional capital as it seeks to advance tilsotolimod and/or any future drug candidates through development to commercialization. The Company does not expect to generate product revenue, sales-based milestones or royalties until the Company successfully completes development of and obtains marketing approval for tilsotolimod or other future drug candidates, either alone or in collaboration with third parties, which the Company expects will take a number of years, if at all. In order to commercialize tilsotolimod and any future drug candidates, the Company needs to complete clinical development and comply with comprehensive regulatory requirements. The Company is subject to a number of risks and uncertainties similar to those of other companies of the same size within the biotechnology industry, such as uncertainty of clinical trial outcomes, uncertainty of additional funding and history of operating losses. ​ The Company follows the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 205-40, Presentation of Financial Statements—Going Concern ​

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies ​ Basis of Presentation ​ The accompanying unaudited financial statements included herein have been prepared by the Company in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and pursuant to the rules and regulations of the SEC. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments, consisting of normal recurring adjustments, and disclosures considered necessary for a fair presentation of interim period results have been included. Interim results for the three months ended March 31, 2021 are not necessarily indicative of results that may be expected for the year ending December 31, 2021. For further information, refer to the financial statements and footnotes thereto included in the Company’s 2020 Form 10-K. ​ Cash and Cash Equivalents ​ The Company considers all highly liquid investments with maturities of 90 days or less when purchased to be “cash equivalents.” Cash and cash equivalents at March 31, 2021 and December 31, 2020 consisted of cash and money market funds. ​ Financial Instruments ​ The fair value of the Company’s financial instruments is determined and disclosed in accordance with the three-tier fair value hierarchy specified in Note 3. The Company is required to disclose the estimated fair values of its financial instruments. As of March 31, 2021, the Company’s financial instruments consisted of cash and cash equivalents. As of December 31, 2020, the Company’s financial instruments consisted of cash, cash equivalents, short-term investments, receivables and warrant and future tranche right liabilities. The estimated fair values of these financial instruments approximate their carrying values. As of March 31, 2021, the Company did not have any derivatives, hedging instruments or other similar financial instruments. ​ Concentration of Credit Risk ​ Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents, and short-term investments. The Company’s credit risk is managed by investing in highly rated money market instruments, U.S. treasury bills, corporate bonds, commercial paper and/or other debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of March 31, 2021, all of the Company’s cash and cash equivalents were held at two financial institutions. ​ Operating Lease Right-of-use Asset and Lease Liability ​ The Company accounts for leases under ASC 842, Leases. Operating leases are included in “Operating lease right-of-use assets” within the Company’s balance sheets and represent the Company’s right to use an underlying asset for the lease term. The Company’s related obligation to make lease payments are included in “Operating lease liability” and “Operating lease liability, net of current portion” within the Company’s balance sheets. Operating lease right-of-use (“ROU”) assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The ROU assets are tested for impairment according to ASC 360, Property, Plant, and Equipmen ​ As of March 31, 2021 and December 31, 2020, the Company’s operating lease ROU assets and corresponding short-term and long-term lease liabilities primarily relate to its existing Exton, PA facility operating lease which expires on May 31, 2025. ​ ​ ​ Note 2. Summary of Significant Accounting Policies (Continued) ​ Warrant Liability ​ The Company accounts for stock warrants as either equity instruments, liabilities or derivative liabilities in accordance with ASC 480, Distinguishing Liabilities from Equity Derivatives and Hedging ​ Future Tranche Right Liability ​ On December 23, 2019, the Company entered into a Securities Purchase Agreement (the “December 2019 Securities Purchase Agreement”) with institutional investors affiliated with Baker Brothers, an existing stockholder (see Note 11). As more fully described in Note 7, the December 2019 Securities Purchase Agreement contained call options on redeemable preferred shares with warrants (conditionally exercisable for shares that are puttable). The Company determined that these call options represented freestanding financial instruments and accounted for the options as liabilities (“Future Tranche Right Liability”) under ASC 480, which requires the measurement and recognition of the fair value of the liability at the time of issuance and at each reporting period. Any change in fair value is recognized in Future Tranche Right Liability Revaluation Gain (Loss) in the Company’s condensed statements of operations. During the three months ended March 31, 2021, the liability-classified call options provided for under the December 2019 Securities Purchase Agreement terminated and, accordingly, the liability balance was derecognized. ​ Preferred Stock ​ The Company applies ASC 480 when determining the classification and measurement of its preferred stock. Preferred shares subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred shares are classified as stockholders’ equity. ​ Accretion of redeemable convertible preferred stock includes the accretion of the Company's Series B redeemable convertible preferred stock to its stated value. The carrying value of the Series B redeemable convertible preferred stock is being accreted to redemption value using the effective interest method, from the date of issuance to the earliest date the holders can demand redemption. ​ Income Taxes ​ In accordance with ASC 270, Interim Reporting Income Taxes ​ Note 2. Summary of Significant Accounting Policies (Continued) ​ New Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB and rules are issued by the SEC that the Company has or will adopt as of a specified date. Unless otherwise noted, management does not believe that any other recently issued accounting pronouncements issued by the FASB or guidance issued by the SEC had, or is expected to have, a material impact on the Company’s present or future financial statements. ​ Recently Adopted Accounting Pronouncements ​ ​ COVID-19 ​ While the Company is not aware of a material impact from the novel coronavirus disease ("COVID-19") pandemic through March 31, 2021, the full extent to which COVID-19 will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses and manufacturing, clinical trials and research and development costs, depends on future developments that are highly uncertain at this time. ​ ​

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements
Fair Value Measurements	Note 3. Fair Value Measurements ​ Assets and Liabilities Measured at Fair Value on a Recurring Basis ​ The Company applies the guidance in ASC 820, Fair Value Measurement ​ The Company uses a fair value hierarchy, which distinguishes between assumptions based on market data (observable inputs) and an entity's own assumptions (unobservable inputs). The guidance requires that fair value measurements be classified and disclosed in one of the following three categories: ● Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; ● Level 2: Quoted prices in markets that are not active or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability ● Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). ​ Determining which category an asset or liability falls within the hierarchy requires significant judgment. The Company evaluates its hierarchy disclosures each reporting period. There were no transfers between Level 1 , 2 and 3 during the three months ended March 31, 2021. ​ ​ Note 3. Fair Value Measurements ​ The table below presents the assets and liabilities measured and recorded in the financial statements at fair value on a recurring basis at March 31, 2021 and December 31, 2020 categorized by the level of inputs used in the valuation of each asset and liability. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 44,291 ​ ​ 44,291 ​ ​ — ​ ​ — Total assets ​ $ 44,541 ​ $ 44,541 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 32,979 ​ ​ 32,979 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ ​ 3,499 ​ ​ — ​ 3,499 ​ — Short-term investments – US treasury bills ​ 1,000 ​ — ​ 1,000 ​ — Total assets ​ $ 37,728 ​ $ 33,229 ​ $ 4,499 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 6,983 ​ $ — ​ $ — ​ $ 6,983 Future tranche right liability ​ ​ 118,803 ​ ​ — ​ ​ — ​ ​ 118,803 Total liabilities ​ $ 125,786 ​ $ — ​ $ — ​ $ 125,786 ​ The Level 1 assets consist of money market funds, which are actively traded daily. The Level 2 assets consist of commercial paper and US treasury bills whose fair value may not represent actual transactions of identical securities. The fair value of commercial paper is generally determined based on the relationship between the investment’s discount rate and the discount rates of the same issuer’s commercial paper available in the market which may not be actively traded daily. Since these fair values may not be based upon actual transactions of identical securities, they are classified as Level 2. ​ Changes in Level 3 Liabilities Measured at Fair Value on a Recurring Basis ​ Warrant Liability and Future Tranche Right Liability ​ The reconciliation of the Company's warrant and future tranche right liability measured at fair value on a recurring basis using unobservable inputs (Level 3) is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Future ​ ​ Warrant ​ Tranche Right (In thousands) ​ Liability ​ Liability Balance, December 31, 2020 $ 6,983 ​ $ 118,803 Change in the fair value of liability (1) (6,983) ​ (118,803) Balance, March 31, 2021 $ — ​ $ — (1) During the three months ended March 31, 2021, the Company’s liability-classified warrants and future tranche rights terminated, and accordingly, the liabilities were derecognized. ​ ​

Investments

Investments	3 Months Ended
	Mar. 31, 2021
Investments
Investments	Note 4. Investments ​ The Company’s available-for-sale investments at fair value consisted of the following as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) Cost (Losses) Gains Value Short-term investments – commercial paper ​ $ 3,499 ​ $ — ​ $ — ​ $ 3,499 Short-term investments – US treasury bills ​ 1,000 ​ — ​ — ​ 1,000 Total short-term investments ​ $ 4,499 ​ $ — ​ $ — ​ $ 4,499 ​ The Company had no realized gains or losses from the sale of investments in available-for-sale securities for the three months ended March 31, 2021 and 2020. In accordance with ASU 2016-13, if the fair value of the Company’s investments in available-for-sale debt securities is less than the amortized cost, the Company records (i) an allowance for credit losses with a corresponding charge to net income (loss) for any credit-related impairment, with subsequent improvements in expected credit losses recognized as a reversal of the allowance, and/or (ii) any non-credit impairment loss to other comprehensive income (loss). ​ As of December 31, 2020, the Company had no allowance for credit losses pertaining to the Company’s investments in available-for-sale debt securities. Additionally, there were no impairment charges or recoveries recorded during each of the three months ended March 31, 2021 and 2020. ​

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2021
Property and Equipment
Property and Equipment	Note 5. Property and Equipment ​ At March 31, 2021 and December 31, 2020, property and equipment, at cost, consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, (In thousands) 2021 2020 Leasehold improvements ​ $ 107 ​ $ 107 Equipment and other ​ 727 ​ 770 Total property and equipment, at cost ​ $ 834 ​ $ 877 Less: Accumulated depreciation and amortization ​ 796 ​ 833 Property and equipment, net ​ $ 38 ​ $ 44 ​ Depreciation and amortization expense on property and equipment was less than $0.1 million for the three months ended March 31, 2021 and 2020. Additionally, there were

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2021
Accrued Expenses
Accrued Expenses	Note 6. Accrued Expenses ​ At March 31, 2021 and December 31, 2020, accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, (In thousands) ​ 2021 2020 Payroll and related costs ​ $ 642 ​ $ 2,133 Clinical and nonclinical trial expenses ​ 3,123 ​ 3,229 Professional and consulting fees ​ 500 ​ 584 Other ​ 133 ​ 126 Total accrued expenses ​ $ 4,398 ​ $ 6,072 ​

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2021
Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock	Note 7. Redeemable Convertible Preferred Stock ​ December 2019 Private Placement ​ On December 23, 2019, the Company entered into the December 2019 Securities Purchase Agreement under which the Company sold 23,684 shares of Series B1 convertible preferred stock (“Series B1 Preferred Stock”) and warrants to purchase 2,368,400 shares of the Company’s common stock at an exercise price of $1.52 per share (or, if the holder elects to exercise the warrants for shares of Series B1 Preferred Stock, 23,684 shares of Series B1 Preferred Stock at an exercise price of $152 per share) for aggregate gross proceeds of $3.9 million (the “Initial Closing”). ​ In addition, the Company agreed to sell to the purchasers, at their option and subject to certain conditions, (i) 98,685 shares of Series B2 convertible preferred stock (“Series B2 Preferred Stock”) and 9,868,500 warrants to purchase common stock at an exercise price of $1.52 per share (or, at the election of the holder, 98,685 shares of Series B2 Preferred Stock at an price of $152 per share), for aggregate gross proceeds of $15 million (the “Series B2 Tranche”), (ii) 82,418 shares of Series B3 convertible preferred stock (“Series B3 Preferred Stock”) and 6,593,440 warrants to purchase common stock at an exercise price of $1.82 per share (or, at the election of the holder, 65,934 shares of Series B3 Preferred Stock at a price of $182 per share), for aggregate gross proceeds of $15 million (the “Series B3 Tranche”), and (iii) 82,418 shares of Series B4 convertible preferred stock (“Series B4 Preferred Stock”) and 6,593,440 warrants to purchase common stock at an exercise price of $1.82 per share (or, at the election of the holder, 65,934 shares of Series B3 Preferred Stock at a price of $182 per share), for aggregate gross proceeds of $15 million (the “Series B4 Tranche”) over a period of up to 21-months following the Company’s 2020 Annual Meeting of Stockholders held on May 12, 2020, where stockholders of the Company voted to approve an amendment to the Company’s Restated Certificate of Incorporation to increase the authorized number of shares of the Company’s common stock to 140,000,000 . As consideration for the future tranche rights, the Company received aggregate gross proceeds of $6.2 million in December 2019. ​ The purchase and sale of the securities issuable under the Series B2, B3, and B4 tranches described above were subject to three separate closings, each to be conducted at the purchasers’ discretion. The right of the purchasers to purchase Series B2, Series B3 and Series B4 Preferred Stock was set to expire on the 10 th business day following the Company’s ORR Data Announcement, as defined in the December 2019 Securities Purchase Agreement, for its ILLUMINATE-301 study. As a result of the purchasers not exercising the Series B2 Tranche prior to expiration, all future tranche rights and outstanding warrants previously issued pursuant to the December 2019 Securities Purchase Agreement were terminated during the three months ended March 31, 2021. Accordingly, the Company is no longer eligible to receive additional proceeds pursuant to the December 2019 Securities Purchase Agreement and the related warrant liability and future tranche right liability were derecognized during the period. ​ Accounting Considerations ​ The Company determined that the Series B1 Preferred Stock, the accompanying Series B1 warrants, and each of the future tranche rights represent freestanding financial instruments. The Series B1 warrants and the future tranche rights were classified as liabilities until their termination in March 2021 as the underlying shares were potentially redeemable and such redemption was deemed to be outside of the Company’s control. ​ Due to the redeemable nature of the Series B1 Preferred Stock, the Series B1 Preferred Stock is classified as temporary equity. While the Series B1 Preferred Stock is not currently redeemable, it will become redeemable either on (i) the fifth anniversary of the initial issue date, or December 23, 2024, provided that certain events (the “Redemption Loss Events”) do not occur first or (ii) upon a liquidation or deemed liquidation event, provided that certain events (the “Liquidation Loss Events”) do not occur first. The Company cannot assess the probability of whether the Redemption Loss Events will occur prior to the fifth anniversary of the initial issue date, if ever, as certain factors triggering such events are outside the control of the Company. Accordingly, the carrying value of the Series B1 Preferred Stock is currently being accreted to its redemption value. In the event the holders of the Series B1 Preferred Stock lose their right to request redemption, the Series B Preferred Stock will no longer be accreted to its redemption value until redemption upon a liquidation event is deemed probable. For the three months ended March 31, 2021 and 2020, accretion was de minimis. ​ ​ Note 7. Redeemable Convertible Preferred Stock (Continued) ​ During the three months ended March 31, 2021, 14,150 shares Series B1 Preferred Stock were converted into shares of the Company’s common stock. Subsequent to March 31, 2021, the Company’s remaining outstanding Series B1 Preferred Stock were converted into shares of the Company’s common stock. See Note 11 for details.

Collaboration and License Agree

Collaboration and License Agreements	3 Months Ended
	Mar. 31, 2021
Collaboration and License Agreements
Collaboration and License Agreements	Note 9. Collaboration and License Agreements ​ Scriptr Collaboration and Option Agreement ​ In February 2021, the Company entered into a collaboration and option agreement with Scriptr Global, Inc. (“Scriptr”), pursuant to which (i) the Company and Scriptr will conduct a research collaboration utilizing Scriptr Platform Technology (“SPT”) to identify, research and develop gene therapy candidates (each, a “Collaboration Candidate”) for the treatment, palliation, diagnosis or prevention of (a) myotonic dystrophy type 1 (“DM1 Field”) and (b) Friedreich’s Ataxia (“FA Field”) on a Research Program-by-Research Program basis, as applicable, and (ii) the Company was granted an exclusive option, in its sole discretion, to make effective the Scriptr License Agreement, as defined below, for a given Research Program, as defined below, to make use of Collaboration Candidates and related intellectual property (collectively, the “Scriptr Agreement”). ​ Pursuant to the Scriptr Agreement, Scriptr will use commercially reasonable efforts to carry out research activities set forth in accordance with the applicable DM1 Field and FA Field research plans, including certain pre-clinical proof of concept studies, to identify research Collaboration Candidates utilizing SPT (each, a “Research Program”). Following the completion of activities under a given Research Program, Scriptr will prepare and submit to Idera a comprehensive data package (each, a “Data Package”) that summarizes, on a Program-by-Program basis, any Collaboration Candidates researched under the Research Program, including any data and results. Upon receipt of a Data Package, the Company has, in its sole discretion, up to two-hundred seventy (270) calendar days to make effective the exclusive license agreement entered into by and between the Company and Scriptr, pursuant to which, among other things, grants Idera exclusive rights and licenses with respect to the development, manufacture and commercialization of licensed candidates and products, subject to certain conditions and limitations (the “Scriptr License Agreement”), for a given Research Program (each licensed Research Program, a “Licensed Program”). The Scriptr License Agreement provides for customary development milestones on candidates developed under a Licensed Program and royalties on licensed products, if any. ​ In partial consideration of the rights granted by Scriptr to the Company under the Scriptr Agreement, the Company made a one-time, non-creditable and non-refundable payment to Scriptr during the first quarter of 2021. In order to fund conduct of the Research Programs, the Company shall reimburse Scriptr for costs incurred by or on behalf of Scriptr in connection with the conduct of each Research Program during the Research Term in accordance with the applicable Research Program budget and payment schedule. The Company incurred approximately

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Stock-Based Compensation
Stock-Based Compensation	Note 10. Stock-Based Compensation ​ As of March 31, 2021, the only equity compensation plans from which the Company may currently issue new awards are the Company’s 2013 Stock Incentive Plan (as amended to date, the “2013 Plan”) and 2017 Employee Stock Purchase Plan (the “2017 ESPP”), each as more fully described below. ​ Equity Incentive and Employee Stock Purchase Plans ​ 2013 Stock Incentive Plan ​ The 2013 Plan allows for the issuance of incentive stock options intended to qualify under Section 422 of the Internal Revenue Code, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units (“RSUs”), other stock-based awards and performance awards. The total number of shares of common stock authorized for issuance under the 2013 Plan is 5,653,057 shares of the Company’s common stock, plus such additional number of shares of common stock (up to 868,372 shares) as is equal to the number of shares of common stock subject to awards granted under the Company’s 2005 Stock Incentive Plan or 2008 Stock Incentive Plan (the “2008 Plan”), to the extent such awards expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right. ​ As of March 31, 2021, options to purchase a total of 4,462,125 shares of common stock and 618,456 restricted stock units were outstanding and up to 420,222 shares of common stock remained available for grant under the 2013 Plan. ​ Other Awards and Inducement Grants ​ The Company has not made any awards pursuant to other equity incentive plans, including the 2008 Plan, since the Company’s stockholders approved the 2013 Plan. As of March 31, 2021, options to purchase a total of 220,408 shares of common stock were outstanding under the 2008 Plan. In addition, as of March 31, 2021, non-statutory stock options to purchase an aggregate of 325,000 shares of common stock were outstanding that were issued outside of the 2013 Plan to certain employees in 2015 and 2014 pursuant to the Nasdaq inducement grant exception as a material component of new hires’ employment compensation. ​ 2017 Employee Stock Purchase Plan ​ The 2017 ESPP is intended to qualify as an "employee stock purchase plan" as defined in Section 423 of the Internal Revenue Code, ​ For the three months ended March 31, 2021 and 2020, the Company issued 7,648 and 18,848 shares of common stock, respectively, under the 2017 ESPP and received proceeds of less than $0.1 million during each period, as a result of employee stock purchases. ​ ​ Note 10. Stock-Based Compensation (Continued) ​ Accounting for Stock-based Compensation ​ The Company recognizes non-cash compensation expense for stock-based awards under the Company’s equity incentive plans and employee stock purchases under the Company’s 2017 ESPP as follows: ​ • Stock Options : Compensation cost is recognized over an award’s requisite service period, or vesting period, using the straight-line attribution method, based on the grant date fair value determined using the Black-Scholes option-pricing model. ​ • RSUs : Compensation cost for time-based RSUs, which vest over time based only on continued service, is recognized on a straight-line basis over the requisite service period based on the fair value of the Company’s common stock on the date of grant. Compensation cost for awards that are subject to market considerations is recognized on a straight-line basis over the implied requisite service period, based on the grant date fair value estimated using a Monte Carlo simulation. Compensation cost for awards that are subject to performance conditions is recognized over the period of time commencing when the performance condition is deemed probable of achievement based on the fair value of the Company’s common stock on the date of grant. ​ • Employee Stock Purchases : Compensation cost is recognized over each plan period based on the fair value of the look-back provision, calculated using the Black-Scholes option-pricing model, considering the 15% discount on shares purchased. ​ Total stock-based compensation expense attributable to stock-based awards made to employees and directors and employee stock purchases included in operating expenses in the Company's condensed statements of operations for the three months ended March 31, 2021 and 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ March 31, (in thousands) ​ 2021 2020 Stock-based compensation: ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 12 $ 11 Equity Incentive Plan ​ ​ 368 ​ 193 ​ ​ $ 380 $ 204 General and administrative ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ 1 Equity Incentive Plan ​ ​ 729 ​ 545 ​ ​ $ 731 $ 546 Total stock-based compensation expense ​ $ 1,111 $ 750 ​ During the three months ended March 31, 2021 and 2020, the weighted average fair market value of stock options granted was $2.53 and $1.07, respectively. ​ ​ Note 10. Stock-Based Compensation (Continued) ​ The following weighted average assumptions apply to the options to purchase 677,500 and 643,629 shares of common stock granted to employees during the three months ended March 31, 2021 and 2020, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 Average risk-free interest rate ​ 0.3% ​ ​ 1.0% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 3.9 Expected volatility ​ 85% ​ ​ 84% Weighted average exercise price (per share) ​ $ 4.20 ​ $ 2.08 ​ All options granted during the three months ended March 31, 2021 and 2020 were granted at exercise prices equal to the fair market value of the Company’s common stock on the date of grant. As further described below, the vesting of certain options granted to employees during the three months ended March 31, 2021 were accelerated during the period. ​ Stock Option Activity ​ The following table summarizes stock option activity for the three months ended March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Stock ​ Weighted-Average ​ Weighted-Average ​ Aggregate Outstanding at December 31, 2020 4,614,323 ​ $ 9.78 6.8 ​ $ 2,949 Granted 677,500 ​ ​ 4.20 ​ ​ ​ ​ ​ Exercised (22,500) ​ ​ 2.11 ​ ​ ​ ​ ​ Forfeited (219,564) ​ ​ 4.09 ​ ​ ​ ​ ​ Expired (42,226) ​ ​ 11.72 ​ ​ ​ ​ ​ Outstanding at March 31, 2021 (1) 5,007,533 ​ $ 9.29 ​ 6.6 ​ $ — Exercisable at March 31, 2021 4,234,391 ​ $ 10.12 ​ 6.3 ​ $ — (1) Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition. ​ During the three months ended March 31, 2021, the Company accelerated the vesting of 1,535,578 options, which were previously granted from 2019 through 2021. As of March 31, 2021, there was $1.8 million of unrecognized compensation cost related to unvested options, which the Company expects to recognize over a weighted average period of 1.8 years. ​ Restricted Stock Activity ​ The following table summarizes restricted stock activity for the three months ended March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time-based Awards ​ Market/Performance-based Awards ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average ​ Number of Shares ​ Weighted-Average Nonvested shares at December 31, 2020 354,003 ​ $ 2.27 ​ 549,318 ​ $ 1.54 Granted — ​ — ​ — ​ — Cancelled (48,100) ​ 2.30 ​ — ​ — Vested (236,765) ​ 2.25 ​ — ​ — Nonvested shares at March 31, 2021 69,138 ​ $ 2.31 ​ 549,318 ​ $ 1.54 ​ ​ ​ ​ Note 10. Stock-Based Compensation (Continued) ​ Time-based Restricted Stock Units ​ During the three months ended March 31, 2021, the Company accelerated the vesting of 137,872 unvested time-based restricted stock units which were previously granted in 2019 and 2020. As of March 31, 2021, there was $0.1 million of unrecognized compensation expense related to the Company’s time-based RSUs, which is expected to be recognized over a weighted-average period of 2.3 years. ​ Market/Performance-based Restricted Stock Units ​ In July 2020, the Company granted RSUs to certain employees, including executive officers, under the 2013 Plan, with vesting that may occur upon a combination of specific performance and/or market conditions. Accordingly, the Company views these RSUs as two separate awards: (i) an award that vests if the market condition is achieved, and (ii) an award that vests whether or not the market condition is achieved, so long as the performance condition is achieved. The Company is currently recognizing compensation expense for these awards over the estimated requisite service period of 2.36 years based on the estimated fair value when considering the market condition of the award, which was determined using a Monte Carlo simulation. During the three months ended March 31, 2021, the Company recognized $0.1 million of compensation expense related to these awards. As of March 31, 2021, the remaining unrecognized compensation cost for the market-based component of these awards, which is expected to be recognized over a weighted-average period of 1.7 years, is $0.6 million. In addition, should the performance condition be achieved, the Company would recognize an additional $0.3 million of compensation expense.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2021
Related Party Transactions
Related Party Transactions	Note 11. Related Party Transactions ​ Baker Brothers ​ Julian C. Baker, a member of the Company’s Board until his resignation in September 2018, is a principal of Baker Bros. Advisors, LP. Additionally, Kelvin M. Neu, a member of Company’s Board until his resignation in June 2019, is an employee of Baker Bros. Advisors, LP. At December 31, 2020, Baker Bros. Advisors, LP and certain of its affiliated funds (collectively, “Baker Brothers”) held sole voting power with respect to an aggregate of 4,608,786 shares of the Company’s common stock, representing approximately 12% of the Company's then outstanding common stock. ​ During the three months ended March 31, 2021, Baker Brothers exercised warrants to purchase 2,708,812 shares of the Company’s common stock at an exercise price of $0.08 per share for a total exercise price of approximately $0.2 million. Additionally, during the three ​ As of March 31, 2021, Baker Brothers held 9,534 shares of the Company’s Series B1 Preferred Stock, which were subsequently converted into 953,400 shares of the Company’s common stock in April 2021. See Note 13. ​ Pillar Investment Entities ​ Youssef El Zein, a member of the Company’s board of directors until his resignation in October 2017, is a director and controlling stockholder of Pillar Invest Corporation (“Pillar Invest”), which is the general partner of Pillar Pharmaceuticals I, L.P., Pillar Pharmaceuticals II, L.P., Pillar Pharmaceuticals III, L.P., Pillar Pharmaceuticals IV, L.P., Pillar Pharmaceuticals V, L.P., Pillar 6, Pillar 7, and Pillar Partners (collectively, the “Pillar Investment Entities”). As of March 31, 2021, the Pillar Investment Entities own approximately 13% of the Company's common stock. ​ During the three months ended March 31, 2021, Pillar 6 exercised warrants to purchase 643,525 shares of the Company’s common stock at an exercise price of $0.01 per share for a total exercise price of less than $0.1 million. ​ ​ Note 11. Related Party Transactions (Continued) ​ As of March 31, 2021, the Pillar Investment Entities held (i) prefunded warrants to purchase up to 4,048,020 shares of the Company’s common stock at an exercise price of $0.01 per share, (ii) warrants to purchase up to 3,039,514 shares of the Company’s common stock at an exercise price of $2.28 per share, (iii) warrants to purchase up to 2,764,227 shares of the Company’s common stock at an exercise price of $2.58 per share, and (iv) warrants to purchase up to 1,373,626 shares of the Company’s common stock at an exercise price of $2.71 per share. ​ Subsequent to March 31, 2021, in April 2021, certain of the Pillar Investment Entities exercised prefunded warrants to purchase 2,514,861 shares of the Company’s common stock at an exercise price of $0.01 per share. See Note 13. ​ Board Fees Paid in Stock ​ Pursuant to the Company’s director compensation program, in lieu of director board and committee fees of less than $0.1 million during each of the three months ended March 31, 2021 and 2020, the Company issued 47,400 and 56,014 shares of common stock, respectively, to certain of its directors. Director board and committee fees are paid in arrears and the number of shares issued was calculated based on the market closing price of the Company’s common stock on the issuance date.

Net Income per Common Share

Net Income per Common Share	3 Months Ended
	Mar. 31, 2021
Net Income per Common Share
Net Income per Common Share	Note 12. Net Income per Common Share ​ The Company uses the two-class method to compute net income per common share during periods the Company realizes net income and has securities outstanding (redeemable convertible preferred stock) that entitle the holder to participate in dividends and earnings of the Company. In addition, the Company analyzes the potential dilutive effect of outstanding redeemable convertible preferred stock under the "if-converted" method when calculating diluted earnings per share and reports the more dilutive of the approaches (two class or "if-converted"). The two-class method is not applicable during periods with a net loss, as the holders of the redeemable convertible preferred stock have no obligation to fund losses. ​ The Company also analyzes the potential dilutive effect of stock options, restricted stock units, warrants and shares underlying future tranche rights under the treasury stock method (as applicable), during periods of income, or during periods in which income is recognized related to changes in fair value of its liability-classified securities. ​ For each of the three months ended March 31, 2021 and 2020, the Company used the two-class method to compute net income per common share. Under this method, net income is reduced by the amount of any dividends earned and the accretion of redeemable convertible preferred stock to its redemption value, if any, during the period. The remaining earnings (undistributed earnings) are allocated to common stock and each series of redeemable convertible preferred stock to the extent that each preferred security may share in earnings as if all of the earnings for the period had been distributed. The total earnings allocated to common stock is then divided by the number of outstanding shares to which the earnings are allocated to determine the earnings per share. ​ ​ Note 12. Net Income per Common Share (Continued) ​ Details in the computation of basic and diluted net income per common share were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ($ in thousands except per share data) ​ ​ 2021 ​ ​ 2020 Net income per share — Basic: ​ ​ ​ ​ ​ ​ Net income ​ $ 115,738 ​ $ 8,817 Less: Undistributed earnings to preferred stockholders ​ ​ (6,132) ​ ​ (639) Net income applicable to common stockholders - basic ​ $ 109,606 ​ $ 8,178 ​ ​ ​ ​ ​ ​ ​ Net income applicable to common stockholders ​ $ 109,606 ​ $ 8,178 Denominator for basic net income per share ​ ​ 41,193 ​ ​ 30,300 Basic net income per common share ​ $ 2.66 ​ $ 0.27 ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share — Diluted: ​ ​ ​ ​ ​ ​ Net income ​ $ 115,738 ​ $ 8,817 Less: Warrant revaluation gain applicable to dilutive warrants ​ ​ (6,983) ​ ​ (1,101) Less: Future tranche right revaluation gain applicable to dilutive future tranche rights ​ ​ (118,803) ​ ​ — Less: Undistributed earnings to preferred stockholders ​ ​ — ​ ​ (517) Numerator for diluted net (loss) income per share ​ $ (10,048) ​ $ 7,199 ​ ​ ​ ​ ​ ​ ​ Denominator for basic net income per share ​ ​ 41,193 ​ ​ 30,300 Plus: Incremental shares underlying “in the money” warrants outstanding ​ ​ 1,449 ​ ​ 2,710 Plus: Incremental shares underlying “in the money” future tranche rights outstanding ​ ​ 28,338 ​ ​ — Denominator for diluted net (loss) income per share ​ ​ 70,980 ​ ​ 33,010 Diluted net (loss) income per common share ​ $ (0.14) ​ $ 0.22 ​ Total antidilutive securities excluded from the calculation of diluted net income per share for the three months ended March 31, 2021 and 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) ​ 2021 ​ 2020 Stock options ​ 5,008 ​ 4,705 Restricted stock units ​ 618 ​ 376 Common stock warrants ​ 11,247 ​ — Convertible preferred stock ​ 954 ​ — Future tranche rights ​ — ​ 49,407 Total ​ 17,827 ​ 54,488 ​

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events
Subsequent Events	Note 13. Subsequent Events ​ The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the financial statements to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. ​ Common Stock Issuance ​ Subsequent to March 31, 2021, in April 2021, the Company (i) issued 953,400 shares of its common stock upon the conversion of the Company’s remaining outstanding Series B1 Preferred Stock and (ii) issued 2,495,809 shares of the Company’s common stock upon the exercise of certain prefunded warrants for aggregate gross proceeds of less than $0.1 million, each as more fully described in Note 11. ​ Reduction-in-Force ​ In April 2021, following the announcement that the Company’s ILLUMINATE-301 trial did not meet its primary endpoint of objective response rate (ORR), the Company decided to implement a reduction in force which is expected to affect approximately 50% of its workforce by May 31, 2021. The decision was made in order to align the Company’s workforce to its needs in light of the outcome of ILLUMINATE-301’s ORR endpoint as the Company evaluates ne xt steps regarding continuation of the trial toward its overall survival (OS) endpoint and other business development activities. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation ​ The accompanying unaudited financial statements included herein have been prepared by the Company in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and pursuant to the rules and regulations of the SEC. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. In the opinion of management, all adjustments, consisting of normal recurring adjustments, and disclosures considered necessary for a fair presentation of interim period results have been included. Interim results for the three months ended March 31, 2021 are not necessarily indicative of results that may be expected for the year ending December 31, 2021. For further information, refer to the financial statements and footnotes thereto included in the Company’s 2020 Form 10-K. ​
Cash and Cash Equivalents	Cash and Cash Equivalents ​ The Company considers all highly liquid investments with maturities of 90 days or less when purchased to be “cash equivalents.” Cash and cash equivalents at March 31, 2021 and December 31, 2020 consisted of cash and money market funds.
Financial Instruments	Financial Instruments ​ The fair value of the Company’s financial instruments is determined and disclosed in accordance with the three-tier fair value hierarchy specified in Note 3. The Company is required to disclose the estimated fair values of its financial instruments. As of March 31, 2021, the Company’s financial instruments consisted of cash and cash equivalents. As of December 31, 2020, the Company’s financial instruments consisted of cash, cash equivalents, short-term investments, receivables and warrant and future tranche right liabilities. The estimated fair values of these financial instruments approximate their carrying values. As of March 31, 2021, the Company did not have any derivatives, hedging instruments or other similar financial instruments.
Concentration of Credit Risk	Concentration of Credit Risk ​ Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents, and short-term investments. The Company’s credit risk is managed by investing in highly rated money market instruments, U.S. treasury bills, corporate bonds, commercial paper and/or other debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of March 31, 2021, all of the Company’s cash and cash equivalents were held at two financial institutions.
Operating Lease Right-of-use Asset and Lease Liability	Operating Lease Right-of-use Asset and Lease Liability ​ The Company accounts for leases under ASC 842, Leases. Operating leases are included in “Operating lease right-of-use assets” within the Company’s balance sheets and represent the Company’s right to use an underlying asset for the lease term. The Company’s related obligation to make lease payments are included in “Operating lease liability” and “Operating lease liability, net of current portion” within the Company’s balance sheets. Operating lease right-of-use (“ROU”) assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The ROU assets are tested for impairment according to ASC 360, Property, Plant, and Equipmen ​ As of March 31, 2021 and December 31, 2020, the Company’s operating lease ROU assets and corresponding short-term and long-term lease liabilities primarily relate to its existing Exton, PA facility operating lease which expires on May 31, 2025.
Warrant Liability	Warrant Liability ​ The Company accounts for stock warrants as either equity instruments, liabilities or derivative liabilities in accordance with ASC 480, Distinguishing Liabilities from Equity Derivatives and Hedging
Future Tranche Right Liability	Future Tranche Right Liability ​ On December 23, 2019, the Company entered into a Securities Purchase Agreement (the “December 2019 Securities Purchase Agreement”) with institutional investors affiliated with Baker Brothers, an existing stockholder (see Note 11). As more fully described in Note 7, the December 2019 Securities Purchase Agreement contained call options on redeemable preferred shares with warrants (conditionally exercisable for shares that are puttable). The Company determined that these call options represented freestanding financial instruments and accounted for the options as liabilities (“Future Tranche Right Liability”) under ASC 480, which requires the measurement and recognition of the fair value of the liability at the time of issuance and at each reporting period. Any change in fair value is recognized in Future Tranche Right Liability Revaluation Gain (Loss) in the Company’s condensed statements of operations. During the three months ended March 31, 2021, the liability-classified call options provided for under the December 2019 Securities Purchase Agreement terminated and, accordingly, the liability balance was derecognized.
Preferred Stock	Preferred Stock ​ The Company applies ASC 480 when determining the classification and measurement of its preferred stock. Preferred shares subject to mandatory redemption are classified as liability instruments and are measured at fair value. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified as temporary equity. At all other times, preferred shares are classified as stockholders’ equity. ​ Accretion of redeemable convertible preferred stock includes the accretion of the Company's Series B redeemable convertible preferred stock to its stated value. The carrying value of the Series B redeemable convertible preferred stock is being accreted to redemption value using the effective interest method, from the date of issuance to the earliest date the holders can demand redemption. ​
Income Taxes	Income Taxes ​ In accordance with ASC 270, Interim Reporting Income Taxes
New Accounting Pronouncements	New Accounting Pronouncements ​ From time to time, new accounting pronouncements are issued by the FASB and rules are issued by the SEC that the Company has or will adopt as of a specified date. Unless otherwise noted, management does not believe that any other recently issued accounting pronouncements issued by the FASB or guidance issued by the SEC had, or is expected to have, a material impact on the Company’s present or future financial statements. ​ Recently Adopted Accounting Pronouncements ​
COVID-19	COVID-19 ​ While the Company is not aware of a material impact from the novel coronavirus disease ("COVID-19") pandemic through March 31, 2021, the full extent to which COVID-19 will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses and manufacturing, clinical trials and research and development costs, depends on future developments that are highly uncertain at this time.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements
Schedule of assets and liabilities measured and recorded in financial statements at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 44,291 ​ ​ 44,291 ​ ​ — ​ ​ — Total assets ​ $ 44,541 ​ $ 44,541 ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 32,979 ​ ​ 32,979 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ ​ 3,499 ​ ​ — ​ 3,499 ​ — Short-term investments – US treasury bills ​ 1,000 ​ — ​ 1,000 ​ — Total assets ​ $ 37,728 ​ $ 33,229 ​ $ 4,499 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 6,983 ​ $ — ​ $ — ​ $ 6,983 Future tranche right liability ​ ​ 118,803 ​ ​ — ​ ​ — ​ ​ 118,803 Total liabilities ​ $ 125,786 ​ $ — ​ $ — ​ $ 125,786
Schedule of reconciliation measured at fair value on a recurring basis using unobservable inputs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Future ​ ​ Warrant ​ Tranche Right (In thousands) ​ Liability ​ Liability Balance, December 31, 2020 $ 6,983 ​ $ 118,803 Change in the fair value of liability (1) (6,983) ​ (118,803) Balance, March 31, 2021 $ — ​ $ — (1) During the three months ended March 31, 2021, the Company’s liability-classified warrants and future tranche rights terminated, and accordingly, the liabilities were derecognized.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2021
Investments
Schedule of available-for-sale investments at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) Cost (Losses) Gains Value Short-term investments – commercial paper ​ $ 3,499 ​ $ — ​ $ — ​ $ 3,499 Short-term investments – US treasury bills ​ 1,000 ​ — ​ — ​ 1,000 Total short-term investments ​ $ 4,499 ​ $ — ​ $ — ​ $ 4,499

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2021
Property and Equipment
Schedule of net property and equipment at cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, (In thousands) 2021 2020 Leasehold improvements ​ $ 107 ​ $ 107 Equipment and other ​ 727 ​ 770 Total property and equipment, at cost ​ $ 834 ​ $ 877 Less: Accumulated depreciation and amortization ​ 796 ​ 833 Property and equipment, net ​ $ 38 ​ $ 44 ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2021
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, (In thousands) ​ 2021 2020 Payroll and related costs ​ $ 642 ​ $ 2,133 Clinical and nonclinical trial expenses ​ 3,123 ​ 3,229 Professional and consulting fees ​ 500 ​ 584 Other ​ 133 ​ 126 Total accrued expenses ​ $ 4,398 ​ $ 6,072

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity
Schedule of warrants outstanding and exercisable for purchase of common stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ Weighted-Average ​ Contractual Description ​ 2021 ​ 2020 ​ Exercise Price ​ Expiration Date Liability-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ December 2019 Series B1 warrants (1) ​ — ​ 2,368,400 ​ ​ $ 1.52 ​ Dec 2026 ​ ​ — ​ 2,368,400 ​ ​ ​ ​ ​ Equity-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ May 2013 warrants 15,437 ​ 1,949,754 ​ ​ $ 0.08 ​ None September 2013 warrants 4,096 ​ 514,756 ​ ​ $ 0.08 ​ None February 2014 warrants 2,171 ​ 266,006 ​ ​ $ 0.08 ​ None April 2020 Private Placement first closing warrants ​ 3,039,514 ​ 3,039,514 ​ ​ $ 2.28 ​ Apr 2023 April 2020 Private Placement second closing warrants ​ 1,373,626 ​ 1,373,626 ​ ​ $ 2.71 ​ Dec 2023 April 2020 Private Placement second closing warrants ​ 2,033,786 ​ 2,677,311 ​ ​ $ 0.01 ​ None July 2020 Private Placement first closing warrants ​ 2,014,234 ​ 2,014,234 ​ ​ $ 0.01 ​ None July 2020 Private Placement first closing warrants ​ 2,764,227 ​ 2,764,227 ​ ​ $ 2.58 ​ Jul 2023 ​ ​ 11,247,091 ​ 14,599,428 ​ ​ ​ ​ ​ Total outstanding 11,247,091 ​ 16,967,828 ​ ​ ​ ​ ​ (1) The Series B1 warrants were exercisable for either common stock (exercise price of $1.52 ) or Series B1 Convertible Preferred Stock (exercise price of $152 ), at the discretion of the warrant holder. However, as more fully disclosed in Note 7, the December 2019 Series B1 warrants were terminated during the three months ended March 31, 2021 contemporaneously with the termination of the future tranche rights.
Summary of warrant activity	​ ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ Weighted-Average ​ ​ Warrants ​ Exercise Price Outstanding at December 31, 2020 16,967,828 ​ $ 1.28 Issued — ​ — Exercised (1) (3,352,337) ​ 0.07 Expired (2,368,400) ​ 1.52 Outstanding at March 31, 2021 11,247,091 ​ $ 1.58 (1) During the three months ended March 31, 2021, certain related parties exercised warrants as more fully described in Note 11.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Stock-Based Compensation
Schedule of stock-based compensation expense attributable to share-based payments made to employees and directors and included in operating expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ March 31, (in thousands) ​ 2021 2020 Stock-based compensation: ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 12 $ 11 Equity Incentive Plan ​ ​ 368 ​ 193 ​ ​ $ 380 $ 204 General and administrative ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ 1 Equity Incentive Plan ​ ​ 729 ​ 545 ​ ​ $ 731 $ 546 Total stock-based compensation expense ​ $ 1,111 $ 750
Schedule of weighted average assumptions applied to options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 2020 Average risk-free interest rate ​ 0.3% ​ ​ 1.0% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 3.9 Expected volatility ​ 85% ​ ​ 84% Weighted average exercise price (per share) ​ $ 4.20 ​ $ 2.08
Schedule of information related to outstanding and exercisable options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Stock ​ Weighted-Average ​ Weighted-Average ​ Aggregate Outstanding at December 31, 2020 4,614,323 ​ $ 9.78 6.8 ​ $ 2,949 Granted 677,500 ​ ​ 4.20 ​ ​ ​ ​ ​ Exercised (22,500) ​ ​ 2.11 ​ ​ ​ ​ ​ Forfeited (219,564) ​ ​ 4.09 ​ ​ ​ ​ ​ Expired (42,226) ​ ​ 11.72 ​ ​ ​ ​ ​ Outstanding at March 31, 2021 (1) 5,007,533 ​ $ 9.29 ​ 6.6 ​ $ — Exercisable at March 31, 2021 4,234,391 ​ $ 10.12 ​ 6.3 ​ $ — (1) Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition.
Schedule of summary of restricted stock activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time-based Awards ​ Market/Performance-based Awards ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average ​ Number of Shares ​ Weighted-Average Nonvested shares at December 31, 2020 354,003 ​ $ 2.27 ​ 549,318 ​ $ 1.54 Granted — ​ — ​ — ​ — Cancelled (48,100) ​ 2.30 ​ — ​ — Vested (236,765) ​ 2.25 ​ — ​ — Nonvested shares at March 31, 2021 69,138 ​ $ 2.31 ​ 549,318 ​ $ 1.54

Net Income per Common Share (Ta

Net Income per Common Share (Tables)	3 Months Ended
	Mar. 31, 2021
Net Income per Common Share
Computation of basic and diluted net income (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ March 31, ($ in thousands except per share data) ​ ​ 2021 ​ ​ 2020 Net income per share — Basic: ​ ​ ​ ​ ​ ​ Net income ​ $ 115,738 ​ $ 8,817 Less: Undistributed earnings to preferred stockholders ​ ​ (6,132) ​ ​ (639) Net income applicable to common stockholders - basic ​ $ 109,606 ​ $ 8,178 ​ ​ ​ ​ ​ ​ ​ Net income applicable to common stockholders ​ $ 109,606 ​ $ 8,178 Denominator for basic net income per share ​ ​ 41,193 ​ ​ 30,300 Basic net income per common share ​ $ 2.66 ​ $ 0.27 ​ ​ ​ ​ ​ ​ ​ Net (loss) income per share — Diluted: ​ ​ ​ ​ ​ ​ Net income ​ $ 115,738 ​ $ 8,817 Less: Warrant revaluation gain applicable to dilutive warrants ​ ​ (6,983) ​ ​ (1,101) Less: Future tranche right revaluation gain applicable to dilutive future tranche rights ​ ​ (118,803) ​ ​ — Less: Undistributed earnings to preferred stockholders ​ ​ — ​ ​ (517) Numerator for diluted net (loss) income per share ​ $ (10,048) ​ $ 7,199 ​ ​ ​ ​ ​ ​ ​ Denominator for basic net income per share ​ ​ 41,193 ​ ​ 30,300 Plus: Incremental shares underlying “in the money” warrants outstanding ​ ​ 1,449 ​ ​ 2,710 Plus: Incremental shares underlying “in the money” future tranche rights outstanding ​ ​ 28,338 ​ ​ — Denominator for diluted net (loss) income per share ​ ​ 70,980 ​ ​ 33,010 Diluted net (loss) income per common share ​ $ (0.14) ​ $ 0.22
Schedule of potentially dilutive securities excluded from diluted net income (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) ​ 2021 ​ 2020 Stock options ​ 5,008 ​ 4,705 Restricted stock units ​ 618 ​ 376 Common stock warrants ​ 11,247 ​ — Convertible preferred stock ​ 954 ​ — Future tranche rights ​ — ​ 49,407 Total ​ 17,827 ​ 54,488

Business and Organization (Deta

Business and Organization (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Business and Organization
Accumulated deficit	$ 717,814	$ 833,552
Cash, cash equivalents and investments	$ 44,500

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)Institution	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Summary of Significant Accounting Policies
Number of financial institutions | Institution	2
Other current liability	$ 217		$ 435
Uncertain tax positions	0		$ 0
Tax expense (benefit)	$ 0	$ 0

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Fair Value Measurements
Fair value of assets transfers from level 1 to level 2	$ 0
Fair value of assets transfers from level 2 to level 1	0
Fair value of liabilities transfers from level 1 to level 2	0
Fair value of liabilities transfers from level 2 to level 1	0
Fair value of assets transfers into level 3	0
Fair value of assets transfers out of level 3	0
Fair value of liabilities transfers into level 3	0
Fair value of liabilities transfers out of level 3	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		$ 4,499
Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	$ 44,541	37,728
Total Liabilities		125,786
Fair value on a recurring basis | Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		6,983
Fair value on a recurring basis | Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		118,803
Fair value on a recurring basis | Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	250	250
Fair value on a recurring basis | Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	44,291	32,979
Fair value on a recurring basis | Short-term investments - commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		3,499
Fair value on a recurring basis | Short-term investments - U.S. treasury bills
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		1,000
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	44,541	33,229
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair value on a recurring basis | Cash
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	250	250
Quoted Prices in Active Markets for Identical Assets or Liabilities (Level 1) | Fair value on a recurring basis | Money market funds
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash and Money market funds	$ 44,291	32,979
Significant Other Observable Inputs (Level 2) | Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets		4,499
Significant Other Observable Inputs (Level 2) | Fair value on a recurring basis | Short-term investments - commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		3,499
Significant Other Observable Inputs (Level 2) | Fair value on a recurring basis | Short-term investments - U.S. treasury bills
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments		1,000
Significant Other Unobservable Inputs (Level 3) | Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		125,786
Significant Other Unobservable Inputs (Level 3) | Fair value on a recurring basis | Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		6,983
Significant Other Unobservable Inputs (Level 3) | Fair value on a recurring basis | Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities		$ 118,803

Fair Value Measurements - Ass_2

Fair Value Measurements - Assets and Liabilities at Fair Value Changes in Level 3 Liabilities (Details) - Fair value on a recurring basis $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Beginning balance	$ 6,983
Change in the fair value of liability	(6,983)
Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Beginning balance	118,803
Change in the fair value of liability	$ (118,803)

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Investments at Fair Value (Details) $ in Thousands	Dec. 31, 2020USD ($)
Short-term investments
Schedule of Available-for-sale Securities
Cost	$ 4,499
Estimated Fair Value	4,499
Short-term investments - commercial paper
Schedule of Available-for-sale Securities
Cost	3,499
Estimated Fair Value	3,499
Short-term investments - U.S. treasury bills
Schedule of Available-for-sale Securities
Cost	1,000
Estimated Fair Value	$ 1,000

Investments - Additional Inform

Investments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Investments
Realized gains or losses	$ 0	$ 0
Allowance for credit losses on available-for-sale debt securities			$ 0
Losses or other-than-temporary declines	$ 0	$ 0

Property and Equipment - Net Pr

Property and Equipment - Net Property and Equipment at Cost (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment
Total property and equipment, at cost	$ 834	$ 877
Less: Accumulated depreciation and amortization	796	833
Property and equipment, net	38	44
Leasehold improvements
Property, Plant and Equipment
Total property and equipment, at cost	107	107
Laboratory equipment and other
Property, Plant and Equipment
Total property and equipment, at cost	$ 727	$ 770

Property and Equipment - Deprec

Property and Equipment - Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property and Equipment
Depreciation and amortization expense on property and equipment	$ 0.1	$ 0.1
Non-cash property additions	$ 0	$ 0

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued Expenses
Payroll and related costs	$ 642	$ 2,133
Clinical and nonclinical trial expenses	3,123	3,229
Professional and consulting fees	500	584
Other	133	126
Total accrued expenses	$ 4,398	$ 6,072

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 23, 2019	Mar. 31, 2021	Dec. 31, 2020
Temporary Equity
Warrant exercised price (per share)		$ 1.58	$ 1.28
Common Stock, Shares Authorized		140,000,000	140,000,000
Expiration period	21 months
Baker Bros. Advisors LP
Temporary Equity
Warrant exercised price (per share)		$ 0.08
Series B1 Redeemable Convertible Preferred Stock
Temporary Equity
Sale of redeemable convertible preferred stock	23,684
Aggregate gross proceeds	$ 3.9
Conversion of preferred stock to common, shares		14,150
Series B1 Redeemable Convertible Preferred Stock | Baker Bros. Advisors LP
Temporary Equity
Conversion of preferred stock to common, shares		14,150
Series B1 Redeemable Convertible Preferred Stock | Common Stock Warrants
Temporary Equity
Warrant to purchase stock	2,368,400
Warrant exercised price (per share)	$ 1.52
Series B1 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase stock	23,684
Warrant exercised price (per share)	$ 152
Series B2 Redeemable Convertible Preferred Stock
Temporary Equity
Sale of redeemable convertible preferred stock	98,685
Aggregate gross proceeds	$ 15
Series B2 Redeemable Convertible Preferred Stock | Common Stock Warrants
Temporary Equity
Warrant to purchase stock	9,868,500
Warrant exercised price (per share)	$ 1.52
Series B2 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase stock	98,685
Warrant exercised price (per share)	$ 152
Series B3 Redeemable Convertible Preferred Stock
Temporary Equity
Sale of redeemable convertible preferred stock	82,418
Aggregate gross proceeds	$ 15
Series B3 Redeemable Convertible Preferred Stock | Common Stock Warrants
Temporary Equity
Warrant to purchase stock	6,593,440
Warrant exercised price (per share)	$ 1.82
Series B3 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase stock	65,934
Warrant exercised price (per share)	$ 182
Series B4 Redeemable Convertible Preferred Stock
Temporary Equity
Sale of redeemable convertible preferred stock	82,418
Aggregate gross proceeds	$ 15
Series B4 Redeemable Convertible Preferred Stock | Common Stock Warrants
Temporary Equity
Warrant to purchase stock	6,593,440
Warrant exercised price (per share)	$ 1.82
Series B4 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase stock	65,934
Warrant exercised price (per share)	$ 182

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 13, 2020	Mar. 04, 2019	Nov. 30, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Class of Stock
Par value (per share)				$ 0.001		$ 0.001
Warrant exercised price (per share)				$ 1.58		$ 1.28
"At-The-Market" Equity Program
Class of Stock
Maximum value of shares that are permitted to be sold, subject to certain limitations				$ 22.9
Stock issued (in shares)				2,394,956	403,983
Net proceeds from offering of common stock				$ 12.1	$ 0.6
Percentage of fixed commission expense of gross proceeds of shares sold in ATM agreement			3.00%
Lincoln Park Capital Fund, LLC ("Investor")
Class of Stock
Value of shares investor has committed to purchase		$ 35
Maximum value of shares that are permitted to be sold, subject to certain limitations				$ 25.3
Stock issued (in shares)		269,749		800,000	450,000
Stock issued (per share)		$ 2.84
Net proceeds from offering of common stock				$ 4.2	$ 0.8
Common Stock | "At-The-Market" Equity Program
Class of Stock
Net proceeds from offering of common stock			$ 50
July 2020 Private Placement Second Closing
Class of Stock
Stock issued (in shares)	784,615
Warrant exercised price (per share)	$ 9.75
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1
Stock price (in dollars per share)	$ 0.01
July 2020 Private Placement Second Closing | Warrants
Class of Stock
Shares of common stock that may be purchased upon exercise of warrants	274,615

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Class of Warrant or Right
Number of Warrants	11,247,091	16,967,828
Warrant exercise price per share	$ 1.58	$ 1.28
Warrants
Class of Warrant or Right
Warrant exercise price per share		$ 1.52
Liability Classified Warrants
Class of Warrant or Right
Number of Warrants		2,368,400
December 2019 Series B1 warrants
Class of Warrant or Right
Number of Warrants		2,368,400
Warrant exercise price per share		$ 1.52
December 2019 Series B1 warrants | Preferred stock
Class of Warrant or Right
Warrant exercise price per share		$ 152
Equity Classified Warrants
Class of Warrant or Right
Number of Warrants	11,247,091	14,599,428
May 2013 Warrants
Class of Warrant or Right
Number of Warrants	15,437	1,949,754
Warrant exercise price per share	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Warrants	4,096	514,756
Warrant exercise price per share	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Warrants	2,171	266,006
Warrant exercise price per share	$ 0.08
April 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Warrants	3,039,514	3,039,514
Warrant exercise price per share	$ 2.28
April 2020 Private Placement second closing warrants
Class of Warrant or Right
Number of Warrants	1,373,626	1,373,626
Warrant exercise price per share	$ 2.71
April 2020 Private Placement second closing warrants
Class of Warrant or Right
Number of Warrants	2,033,786	2,677,311
Warrant exercise price per share	$ 0.01
July 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Warrants	2,014,234	2,014,234
Warrant exercise price per share	$ 0.01
July 2020 Private Placement first closing warrants
Class of Warrant or Right
Number of Warrants	2,764,227	2,764,227
Warrant exercise price per share	$ 2.58

Stockholders' Equity - Common_3

Stockholders' Equity - Common Stock Warrant Activity (Details)	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Stockholders' Equity
Outstanding warrants, beginning of period | shares	16,967,828
Exercised | shares	(3,352,337)
Expired | shares	(2,368,400)
Outstanding warrants, end of period | shares	11,247,091
Warrant exercise price per share, beginning of period | $ / shares	$ 1.28
Exercised | $ / shares	$ 0.07
Warrant exercise price per share, expired | $ / shares	1.52
Warrants exercise price per share, end of period | $ / shares	$ 1.58

Collaboration and License Agr_2

Collaboration and License Agreements (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Research and development		$ 6,871	$ 9,510
Scriptr Global, Inc. | Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Research period	270 days
Research and development		$ 700

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive Plans (Details) - shares	Jul. 26, 2013	Mar. 31, 2021	Dec. 31, 2020
Class of Stock
Common stock options outstanding		5,007,533	4,614,323
Options outstanding under earlier plans		220,408
Grant of inducement stock option		325,000
2013 Stock Incentive Plan | 2013 Stock Incentive Plan
Class of Stock
Common shares available for grant	5,653,057	420,222
Maximum number of additional common shares	868,372
Common stock options outstanding		4,462,125
Restricted stock units outstanding		618,456

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Jun. 07, 2017
Class of Stock
Proceeds from employee stock purchases	$ 28	$ 25
2017 Employee Stock Purchase Plan
Class of Stock
Common shares available for grant	237,694
Common stock share issued	7,648	18,848
Defined Contribution Plan, Cost	$ 100	$ 100
Maximum | 2017 Employee Stock Purchase Plan
Class of Stock
Common stock shares authorized for issuance under stock purchase plan			412,500

Stock-Based Compensation - Acco

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award
Percentage of share-based compensation expense	15.00%
Weighted average grant date fair value of options granted during the period (per share)	$ 2.53	$ 1.07
Stock-based compensation	$ 1,111	$ 750
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	380	204
Research and development | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	12	11
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	368	193
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	731	546
General and administrative | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	2	1
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 729	$ 545

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used in Determining Fair Value of Stock Options (Details) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock-Based Compensation
Options to purchase common stock granted to employees and directors	677,500	643,629
Average risk free interest rate	0.30%	1.00%
Expected lives (years)	3 years 10 months 24 days	3 years 10 months 24 days
Expected volatility	85.00%	84.00%
Weighted average exercise price of options granted during the period (per share)	$ 4.20	$ 2.08

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Stock-Based Compensation
Options, Outstanding, Beginning Balance	4,614,323
Granted	677,500
Exercised	(22,500)
Forfeited	(219,564)
Expired	(42,226)
Options, Outstanding, Ending Balance	5,007,533		4,614,323
Exercisable, Ending Balance	4,234,391
Weighted Average Exercise Price, Beginning Balance	$ 9.78
Granted, Weighted Average Exercise Price	4.20	$ 2.08
Exercised, Weighted Average Exercise Price	2.11
Forfeited, Weighted Average Exercise Price	4.09
Expired, Weighted Average Exercise Price	11.72
Weighted Average Exercise Price, Ending Balance	9.29		$ 9.78
Exercisable, Weighted Average Exercise Price	$ 10.12
Outstanding, Ending balance, Weighted Average Remaining Contractual Term	6 years 7 months 6 days		6 years 9 months 18 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term	6 years 3 months 18 days
Outstanding, Intrinsic Value, Ending Balance			$ 2,949
Number of shares vested	1,535,578
Unrecognized compensation cost related to nonvested stock-based compensation	$ 1,800
Weighted average remaining period over which unrecognized compensation expense will be recognized	1 year 9 months 18 days

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Jul. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Unrecognized compensation expense		$ 1,800
Weighted average remaining period over which unrecognized compensation expense will be recognized		1 year 9 months 18 days
Share-based compensation		$ 1,111	$ 750
Restricted stock units
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance		354,003
Cancelled		(48,100)
Vested		(236,765)
Nonvested shares, Ending Balance		69,138
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance		$ 2.27
Cancelled, Weighted-Average Grant Date Fair Value		2.30
Vested, Weighted-Average Grant Date Fair Value		2.25
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 2.31
Accelerated vesting, number of shares		137,872
Unrecognized compensation expense		$ 100
Weighted average remaining period over which unrecognized compensation expense will be recognized		2 years 3 months 18 days
Market/Performance-based Awards
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance		549,318
Nonvested shares, Ending Balance		549,318
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance		$ 1.54
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 1.54
Weighted average remaining period over which unrecognized compensation expense will be recognized		1 year 8 months 12 days
Requisite service period (in years)	2 years 4 months 9 days
Share-based compensation		$ 100
Unrecognized compensation expense related to the restricted stock units		600
Additional compensation expense as a result of meeting certain achievements		$ 300

Related Party Transactions - Ov

Related Party Transactions - Overview of Related Parties (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Related Party Transactions
Exercise price of warrants		$ 1.58		$ 1.28
Number of Warrants		11,247,091		16,967,828
Common stock issued in lieu of board fees		47,400	56,014
Maximum
Related Party Transactions
Proceeds from issuance of common stock in lieu of director board and committee fees		$ 0.1	$ 0.1
Series B1 Redeemable Convertible Preferred Stock
Related Party Transactions
Conversion of preferred stock to common, shares		14,150
Baker Bros. Advisors LP
Related Party Transactions
Ownership percentage		4.00%		12.00%
Issuance of common stock upon exercise of warrants (in shares)		2,708,812
Exercise price of warrants		$ 0.08
Proceeds from exercise of warrants		$ 0.2
Aggregate common shares				4,608,786
Baker Bros. Advisors LP | Series B1 Redeemable Convertible Preferred Stock
Related Party Transactions
Aggregate common shares		9,534
Conversion of preferred stock to common, shares		14,150
Baker Bros. Advisors LP | Common stock
Related Party Transactions
Shares issued on exercise of warrants during the period	953,400	1,415,000
Pillar Investment Entities
Related Party Transactions
Ownership percentage		13.00%
Exercise price of warrants		$ 0.01
Proceeds from exercise of warrants		$ 0.1
Pillar Investment Entities | Common Stock Warrants Exercise Price, Two Point Two Eight
Related Party Transactions
Exercise price of warrants		$ 2.28
Number of Shares		3,039,514
Pillar Investment Entities | Common Stock Warrants Exercise Price Two Point Five Eight
Related Party Transactions
Exercise price of warrants		$ 2.58
Number of Shares		2,764,227
Pillar Investment Entities | Pre Funded Warrant, Tranche One
Related Party Transactions
Exercise price of warrants		$ 0.01
Number of Shares		4,048,020
Pillar Investment Entities | Common Stock Warrants Exercise Price Two Point Seven One
Related Party Transactions
Exercise price of warrants		$ 2.71
Number of Shares		1,373,626
Pillar Investment Entities | Pre Funded Warrant, Tranche Two
Related Party Transactions
Exercise price of warrants	$ 0.01
Number of Shares	2,514,861
Pillar Six Entities [Member]
Related Party Transactions
Issuance of common stock upon exercise of warrants (in shares)		643,525

Net Income per Common Share -Co

Net Income per Common Share -Computation of basic and diluted net income per common share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Net loss per share - Basic:
Net income	$ 115,738	$ 8,817
Less: Undistributed earnings to preferred stockholders	(6,132)	(639)
Net income applicable to common stockholders - basic	109,606	8,178
Net income applicable to common stockholders	$ 109,606	$ 8,178
Denominator for basic net income per share	41,193	30,300
Basic net income per common share	$ 2.66	$ 0.27
Net (loss) income per share - Diluted:
Net income	$ 115,738	$ 8,817
Less: Warrant revaluation gain applicable to dilutive warrants	(6,983)	(1,101)
Less: Future tranche right revaluation gain applicable to dilutive future tranche rights	(118,803)
Less: Undistributed earnings to preferred stockholders		(517)
Numerator for diluted net (loss) income per share	$ (10,048)	$ 7,199
Denominator for basic net income per share	41,193	30,300
Plus: Incremental shares underlying "in the money" warrants outstanding	1,449	2,710
Plus: Incremental shares underlying "in the money" future tranche rights outstanding	28,338
Denominator for diluted net (loss) income per share	70,980	33,010
Diluted net (loss) income per common share	$ (0.14)	$ 0.22

Net Income per Common Share - A

Net Income per Common Share - Antidilutive securities (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive securities
Total antidilutive securities	17,827	54,488
Stock options
Antidilutive securities
Total antidilutive securities	5,008	4,705
Restricted stock units
Antidilutive securities
Total antidilutive securities	618	376
Common Stock Warrants
Antidilutive securities
Total antidilutive securities	11,247
Convertible preferred stock
Antidilutive securities
Total antidilutive securities	954
Future tranche right liability
Antidilutive securities
Total antidilutive securities		49,407

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Events - USD ($) $ in Millions	1 Months Ended		2 Months Ended
	May 31, 2021	Apr. 30, 2021	Jun. 30, 2021
Subsequent Events
Percentage of positions eliminated	50.00%
Termination costs in connection with the reduction in workforce, including severance, benefits and related costs		$ 0.7	$ 0.2
Maximum
Subsequent Events
Gross proceeds from issuance of common stock and warrants		$ 0.1
Pre-funded Warrants
Subsequent Events
Issuance of common stock upon exercise of warrants (in shares)		2,495,809
Common Stock
Subsequent Events
Shares of common stock issued upon conversion		953,400