Aceragen (ACGN) 10-Q 29 Oct 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 29, 2020
Document and Entity Information
Document Type	10-Q
Document Period End Date	Sep. 30, 2020
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	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		35,250,789
Entity Central Index Key	0000861838
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 22,332	$ 40,019
Short-term investments	6,647	2,774
Prepaid expenses and other current assets	2,260	3,475
Total current assets	31,239	46,268
Property and equipment, net	52	97
Operating lease right-of-use assets	977	1,054
Other assets	70	70
Total assets	32,338	47,489
Current liabilities:
Accounts payable	310	457
Accrued expenses	6,308	7,461
Operating lease liability	187	163
Future tranche right liability		46,436
Total current liabilities	6,805	54,517
Warrant liability, long-term	3,736	3,241
Future tranche right liability, long-term	53,424
Operating lease liability, net of current portion	808	899
Total liabilities	64,773	58,657
Commitments and contingencies
Stockholders' equity (deficit)
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 35,219 and 29,672 at September 30, 2020 and December 31, 2019, respectively	35	30
Additional paid-in capital	724,381	709,692
Accumulated deficit	(756,851)	(720,890)
Total stockholders' deficit	(32,435)	(11,168)
Total liabilities and stockholders' deficit	32,338	47,489
Series B1 redeemable convertible preferred stock
Stockholders' equity (deficit)
Preferred stock
Series A convertible preferred stock; Designated - 1,500 shares, Issued and outstanding - 1 share
Stockholders' equity (deficit)
Preferred stock

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	140,000,000	140,000,000
Common stock, shares issued	35,219,000	29,672,000
Common stock, shares outstanding	35,219,000	29,672,000
Series A convertible preferred stock; Designated - 1,500 shares, Issued and outstanding - 1 share
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
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	24,000	24,000
Preferred stock, shares outstanding	24,000	24,000
Common stock, shares outstanding	24,000	24,000

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Alliance revenue				$ 1,448
Revenue, Product and Service [Extensible List]	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax
Operating expenses:
Research and development	$ 4,766	$ 8,359	$ 19,655	$ 26,485
General and administrative	2,718	3,023	8,992	9,061
Restructuring costs		5		181
Total operating expenses	7,484	11,387	28,647	35,727
Loss from operations	(7,484)	(11,387)	(28,647)	(34,279)
Other income (expense):
Interest income	9	249	161	992
Warrant revaluation loss	(683)		(495)
Future tranche right revaluation loss	(12,350)		(6,988)
Foreign currency exchange (loss) gain	(44)	5	8	4
Net loss	$ (20,552)	$ (11,133)	$ (35,961)	$ (33,283)
Net loss per share applicable to common stockholders - basic and diluted (Note 12)	$ (0.59)	$ (0.39)	$ (1.09)	$ (1.17)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders - basic and diluted	35,091	28,847	32,999	28,332
Comprehensive loss:
Net loss	$ (20,552)	$ (11,133)	$ (35,961)	$ (33,283)
Unrealized (loss) gain on available-for-sale securities		(1)		1
Total other comprehensive (loss) income		(1)		1
Comprehensive loss	$ (20,552)	$ (11,134)	$ (35,961)	$ (33,282)

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities:
Net loss	$ (35,961)	$ (33,283)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,273	2,868
Warrant liability revaluation loss	495
Future tranche right liability revaluation loss	6,988
Issuance of common stock for services rendered	170	92
Accretion of discounts on short-term investments	(43)	(377)
Depreciation and amortization expense	52	94
Gain on disposal of property and equipment		(10)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,215	(2,298)
Accounts payable, accrued expenses, and other liabilities	(1,391)	(1,257)
Other	10
Net cash used in operating activities	(26,192)	(34,171)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(12,180)	(44,447)
Proceeds from maturity of available-for-sale securities	8,350	35,850
Proceeds from the sale of property and equipment		11
Purchases of property and equipment	(7)	(11)
Net cash used in investing activities	(3,837)	(8,597)
Cash Flows from Financing Activities:
Proceeds from equity financings, net	12,258	3,857
Proceeds from employee stock purchases	84	97
Other		(6)
Net cash provided by financing activities	12,342	3,948
Net decrease in cash and cash equivalents	(17,687)	(38,820)
Cash and cash equivalent, beginning of period	40,019	71,431
Cash and cash equivalents, end of period	22,332	32,611
Supplemental disclosure of cash flow information:
Increase to right-of-use asset upon adoption of ASC 842		261
Increase to operating lease right-of-use assets upon acquisition	54
Increase to lease liability upon adoption of ASC 842		$ 261
Increase to operating lease liability upon acquisition	54
Supplemental disclosure of non-cash financing and investing activities:
Offering costs in accounts payable and accrued expenses	$ 91

CONDENSED STATEMENTS OF REDEEMA

CONDENSED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Series B1 redeemable convertible preferred stock	Total
Cumulative effect from adoption of new accounting standard (Note 2)	$ 27	$ 728,342	$ (664,375)			$ 63,994
Beginning balance at Dec. 31, 2018	$ 27	728,342	(664,375)			63,994
Beginning balance (in shares) at Dec. 31, 2018	27,188
Cumulative effect from adoption of new accounting standard (Note 2)	$ 28	730,991	(675,349)	$ 2		55,672
Sale of common stock, net of issuance costs	$ 1	1,584				1,585
Sale of common stock, net of issuance costs (in shares)	533
Issuance of commitment shares (Note 8) (in shares)	270
Issuance of common stock under employee stock purchase plan		26				26
Issuance of common stock under employee stock purchase plan (in shares)	11
Issuance of common stock for services rendered		23				23
Issuance of common stock for services rendered (in shares)	6
Stock-based compensation expense		1,016				1,016
Unrealized gain on marketable securities				2		2
Net income (loss)			(10,974)			(10,974)
Ending balance at Mar. 31, 2019	$ 28	730,991	(675,349)	2		55,672
Ending balance (in shares) at Mar. 31, 2019	28,008
Beginning balance at Dec. 31, 2018	$ 27	728,342	(664,375)			63,994
Beginning balance (in shares) at Dec. 31, 2018	27,188
Cumulative effect from adoption of new accounting standard (Note 2)	$ 29	735,254	(697,658)	1		37,626
Net income (loss)						(33,283)
Ending balance at Sep. 30, 2019	$ 29	735,254	(697,658)	1		37,626
Ending balance (in shares) at Sep. 30, 2019	28,858
Cumulative effect from adoption of new accounting standard (Note 2)	$ 28	730,991	(675,349)	2		55,672
Beginning balance at Mar. 31, 2019	$ 28	730,991	(675,349)	2		55,672
Beginning balance (in shares) at Mar. 31, 2019	28,008
Cumulative effect from adoption of new accounting standard (Note 2)	$ 29	734,229	(686,525)	2		47,735
Sale of common stock, net of issuance costs	$ 1	2,271				2,272
Sale of common stock, net of issuance costs (in shares)	786
Issuance of common stock under employee stock purchase plan		42				42
Issuance of common stock under employee stock purchase plan (in shares)	19
Issuance of common stock for services rendered		36				36
Issuance of common stock for services rendered (in shares)	14
Stock-based compensation expense		889				889
Net income (loss)			(11,176)			(11,176)
Ending balance at Jun. 30, 2019	$ 29	734,229	(686,525)	2		47,735
Ending balance (in shares) at Jun. 30, 2019	28,827
Cumulative effect from adoption of new accounting standard (Note 2)	$ 29	734,229	(686,525)	2		47,735
Cumulative effect from adoption of new accounting standard (Note 2)	$ 29	735,254	(697,658)	1		37,626
Issuance of common stock under employee stock purchase plan		29				29
Issuance of common stock under employee stock purchase plan (in shares)	15
Issuance of common stock upon exercise of warrants (in shares)	4
Issuance of common stock for services rendered		33				33
Issuance of common stock for services rendered (in shares)	12
Stock-based compensation expense		963				963
Unrealized gain on marketable securities				(1)		(1)
Net income (loss)			(11,133)			(11,133)
Ending balance at Sep. 30, 2019	$ 29	735,254	(697,658)	1		37,626
Ending balance (in shares) at Sep. 30, 2019	28,858
Cumulative effect from adoption of new accounting standard (Note 2)	$ 29	735,254	(697,658)	$ 1		37,626
Cumulative effect from adoption of new accounting standard (Note 2)	30	709,692	(720,890)			(11,168)
Beginning balance at Dec. 31, 2019	$ 30	709,692	(720,890)			$ (11,168)
Beginning balance (in shares) at Dec. 31, 2019	29,672				24	29,672
Cumulative effect from adoption of new accounting standard (Note 2)	$ 31	711,898	(712,073)			$ (144)
Sale of common stock, net of issuance costs	$ 1	1,405				1,406
Sale of common stock, net of issuance costs (in shares)	854
Issuance of common stock under employee stock purchase plan		25				25
Issuance of common stock under employee stock purchase plan (in shares)	19
Issuance of common stock under equity incentive plan (vesting of restricted stock units)	48
Issuance of common stock for services rendered		26				26
Issuance of common stock for services rendered (in shares)	14
Stock-based compensation expense		750				750
Net income (loss)			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				24
Beginning balance at Dec. 31, 2019	$ 30	709,692	(720,890)			$ (11,168)
Beginning balance (in shares) at Dec. 31, 2019	29,672				24	29,672
Cumulative effect from adoption of new accounting standard (Note 2)	$ 35	724,381	(756,851)			$ (11,168)
Net income (loss)						(35,961)
Ending balance at Sep. 30, 2020	$ 35	724,381	(756,851)			$ (32,435)
Ending balance (in shares) at Sep. 30, 2020	35,219				24	35,219
Cumulative effect from adoption of new accounting standard (Note 2)	$ 31	711,898	(712,073)			$ (144)
Beginning balance at Mar. 31, 2020	$ 31	711,898	(712,073)			(144)
Beginning balance (in shares) at Mar. 31, 2020	30,607				24
Cumulative effect from adoption of new accounting standard (Note 2)	$ 34	718,574	(736,299)			(17,691)
Sale of common stock, net of issuance costs	$ 3	5,821				5,824
Sale of common stock, net of issuance costs (in shares)	3,607
Issuance of common stock under employee stock purchase plan		29				29
Issuance of common stock under employee stock purchase plan (in shares)	21
Issuance of common stock for services rendered		72				72
Issuance of common stock for services rendered (in shares)	56
Stock-based compensation expense		754				754
Net income (loss)			(24,226)			(24,226)
Ending balance at Jun. 30, 2020	$ 34	718,574	(736,299)			(17,691)
Ending balance (in shares) at Jun. 30, 2020	34,291				24
Cumulative effect from adoption of new accounting standard (Note 2)	$ 34	718,574	(736,299)			(17,691)
Cumulative effect from adoption of new accounting standard (Note 2)	35	724,381	(756,851)			(17,691)
Sale of common stock, net of issuance costs	$ 1	4,936				4,937
Sale of common stock, net of issuance costs (in shares)	868
Issuance of common stock under employee stock purchase plan		30				30
Issuance of common stock under employee stock purchase plan (in shares)	19
Issuance of common stock for services rendered		72				72
Issuance of common stock for services rendered (in shares)	41
Stock-based compensation expense		769				769
Net income (loss)			(20,552)			(20,552)
Ending balance at Sep. 30, 2020	$ 35	724,381	(756,851)			$ (32,435)
Ending balance (in shares) at Sep. 30, 2020	35,219				24	35,219
Cumulative effect from adoption of new accounting standard (Note 2)	$ 35	$ 724,381	$ (756,851)			$ (32,435)

Business and Organization

Business and Organization	9 Months Ended
	Sep. 30, 2020
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 believes it can 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 September 30, 2020, the Company had an accumulated deficit of $756.9 million and a cash, cash equivalents, and short-term investments balance of $29.0 million. The Company expects to incur substantial operating losses in future periods and will require additional capital as it seeks to advance tilsotolimod and 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. 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”) Topic 205-40, Presentation of Financial Statements—Going Concern

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
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 and nine months ended September 30, 2020 are not necessarily indicative of results that may be expected for the year ending December 31, 2020. For further information, refer to the financial statements and footnotes thereto included in the Company’s 2019 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 September 30, 2020 and December 31, 2019 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 September 30, 2020 and December 31, 2019, 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 September 30, 2020, the Company did not have any other derivatives, or any hedging 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 credit risk is believed by management to be inherent in the Company’s assets. As of September 30, 2020, all of the Company’s cash, cash equivalents and short-term investments were held at two financial institutions. ​ Operating Lease Right-of-use Assets and Lease Liability ​ The Company accounts for leases under ASC Topic 842, Leases Property, Plant, and Equipment ​ As of September 30, 2020 and December 31, 2019, 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 Topic 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 (the “Purchasers”), an existing stockholder and related party (see Note 11). As more fully described in Note 7, the December 2019 Securities Purchase Agreement contains call options on redeemable preferred shares with warrants (conditionally exercisable for shares that are puttable). The Company determined that these call options represent freestanding financial instruments and accounts 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 (Loss) Gain in the Company’s condensed statements of operations and comprehensive loss. ​ As of September 30, 2020, the Future Tranche Right Liability is classified as a long-term liability in the Company’s condensed balance sheet as settlement is in the form of the applicable Series B convertible preferred stock and warrants exercisable for shares of either Series B1 Preferred Stock or the Company’s common stock. As of December 31, 2019, the Future Tranche Right Liability was classified as a current liability because the Future Tranche Rights and related Option Fee, each defined in Note 7, were subject to the Company obtaining required shareholder approval, which was obtained in May 2020. ​ 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 Topic 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 ​ Financial Instruments Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ​ In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurement Fair Value Measurement ​ Recently Issued (But Not Yet Adopted) Accounting Pronouncements ​ In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity ​ COVID-19 ​ While the Company is not aware of a material impact from the novel coronavirus disease ("COVID-19") pandemic through September 30, 2020, 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	9 Months Ended
	Sep. 30, 2020
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 Topic 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 nine months ended September 30, 2020. ​ The table below presents the assets and liabilities measured and recorded in the financial statements at fair value on a recurring basis at September 30, 2020 and December 31, 2019 categorized by the level of inputs used in the valuation of each asset and liability. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 22,082 ​ ​ 22,082 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 5,647 ​ — ​ 5,647 ​ — Short-term investments – US treasury bills ​ 1,000 ​ — ​ 1,000 ​ — Total assets ​ $ 28,979 ​ $ 22,332 ​ $ 6,647 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,736 ​ $ — ​ $ — ​ $ 3,736 Future tranche right liability ​ ​ 53,424 ​ ​ — ​ ​ — ​ ​ 53,424 Total liabilities ​ $ 57,160 ​ $ — ​ $ — ​ $ 57,160 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 39,769 ​ ​ 39,769 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 2,774 ​ — ​ 2,774 ​ — Total assets ​ $ 42,793 ​ $ 40,019 ​ $ 2,774 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,241 ​ $ — ​ $ — ​ $ 3,241 Future tranche right liability ​ ​ 46,436 ​ ​ — ​ ​ — ​ ​ 46,436 Total liabilities ​ $ 49,677 ​ $ — ​ $ — ​ $ 49,677 ​ ​ Note 3. Fair Value Measurements (Continued) ​ The Level 1 assets consist of money market funds, which are actively traded daily. The Level 2 assets consist of commercial paper 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, 2019 $ 3,241 ​ $ 46,436 Change in the fair value of liability 495 ​ 6,988 Balance, September 30, 2020 $ 3,736 ​ $ 53,424 ​ Assumptions Used in Determining Fair Value of Liability-Classified Warrants ​ The Company utilizes an option pricing model to value its liability-classified warrants. Inherent in the valuation model are assumptions related to volatility, risk-free interest rate, expected term, dividend rate, and other scenarios (i.e. probability of complex features of the warrants being triggered). ​ The fair value of the warrants has been estimated with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.35% ​ ​ 1.79% Expected dividend yield ​ — ​ ​ — Expected term (years) ​ 6.23 ​ ​ 6.98 Expected volatility ​ 80% ​ ​ 80% Exercise price (per share) $ 1.52 ​ $ 1.52 ​ Assumptions Used in Determining Fair Value of Future Tranche Rights ​ The Company utilizes a lattice model to value the Series B2 and B3 tranches and a Monte Carlo simulation to value the Series B4 future tranche rights. The Company selected these models as it believes they are reflective of all significant assumptions that market participants would likely consider in negotiating the transfer of the Future Tranche Rights (as defined in Note 7). Such assumptions include, among other inputs, stock price volatility, risk-free rates, and expected terms inclusive of early exercise and cancellation assumptions. ​ The estimated fair value of the Future Tranche Rights is determined using Level 2 and Level 3 inputs. Significant inputs and assumptions used in the valuation models are as follows: ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.45% - 0.53% ​ ​ 1.84% - 1.88% Expected dividend yield ​ — ​ ​ — Expected term (years) of call options on preferred stock ​ 0.41 - 1.37 ​ ​ 1.16 - 2.16 Expected term (years) of warrants ​ 7.41 - 8.37 ​ ​ 8.16 - 9.16 Expected volatility ​ 80% ​ ​ 80% Exercise price (per share) for common stock equivalent for preferred stock and warrant $ 1.52 - 1.82 ​ $ 1.52 - 1.82 ​

Investments

Investments	9 Months Ended
	Sep. 30, 2020
Investments
Investments	Note 4. Investments ​ The Company’s available-for-sale investments at fair value consisted of the following as of September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ Gross Gross Estimated ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Cost ​ (Losses) ​ Gains ​ Value Short-term investments – commercial paper ​ $ 5,647 ​ $ — ​ $ — ​ $ 5,647 Short-term investments – US treasury bills ​ ​ 1,000 ​ ​ — ​ ​ — ​ ​ 1,000 Total short-term investments ​ $ 6,647 ​ $ — ​ $ — ​ $ 6,647 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) Cost (Losses) Gains Value Short-term investments – commercial paper ​ $ 2,774 ​ $ — ​ $ — ​ $ 2,774 Total short-term investments ​ $ 2,774 ​ $ — ​ $ — ​ $ 2,774 ​ The Company had no realized gains or losses from the sale of investments in available-for-sale securities during each of the nine months ended September 30, 2020 and 2019. 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 September 30, 2020 and December 31, 2019, 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 nine months ended September 30, 2020 and 2019.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2020
Property and Equipment
Property and Equipment	Note 5. Property and Equipment ​ At September 30, 2020 and December 31, 2019, property and equipment, net, consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) 2020 2019 Leasehold improvements ​ $ 107 ​ $ 107 Equipment and other ​ 770 ​ 764 Total property and equipment, at cost ​ $ 877 ​ $ 871 Less: Accumulated depreciation and amortization ​ 825 ​ 774 Property and equipment, net ​ $ 52 ​ $ 97 ​ Depreciation and amortization expense on property and equipment was less than $0.1 million for each of the three and nine months ended September 30, 2020 and 2019. Additionally, there were

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Accrued Expenses
Accrued Expenses	Note 6. Accrued Expenses ​ At September 30, 2020 and December 31, 2019, accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) ​ 2020 2019 Payroll and related costs ​ $ 2,294 ​ $ 2,179 Clinical and nonclinical trial expenses ​ 3,397 ​ 4,199 Professional and consulting fees ​ 493 ​ 859 Restructuring expenses ​ — ​ 113 Other ​ 124 ​ 111 Total accrued expenses ​ $ 6,308 ​ $ 7,461 ​

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2020
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 has agreed to sell to the Purchasers, at their option and subject to certain conditions, shares of Series B2 convertible preferred stock (“Series B2 Preferred Stock”), Series B3 convertible preferred stock (“Series B3 Preferred Stock”) and Series B4 convertible preferred stock (“Series B4 Preferred Stock) and accompanying warrants to purchase common stock (or preferred stock at the election of the holder) over a 21-month period following stockholder approval for the Charter Amendment (the “Future Tranche Rights”). As of September 30, 2020, the Company’s outstanding Future Tranche Rights are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Price Per ​ ​ Aggregate Future Tranche Rights ​ Preferred Shares ​ Share ​ ​ Purchase Price Tranche 2 (Series B2) (1) ​ 98,685 ​ $ 152 ​ $ 15,000,120 Tranche 3 (Series B3) (2) ​ 82,418 ​ $ 182 ​ ​ 15,000,076 Tranche 4 (Series B4) (2) ​ 82,418 ​ $ 182 ​ ​ 15,000,076 Total ​ 263,521 ​ ​ ​ ​ $ 45,000,272 (1) Accompanied by related warrants to purchase up to 9,868,500 shares of the Company’s common stock (or, if the holder elects to exercise the warrants for shares of Series B1 Preferred Stock, 98,685 shares of Series B1 Preferred Stock), at an exercise price of $1.52 per share (or, if the holder elects to exercise the warrants for Series B1 Preferred Stock, $152 per share of Series B1 Preferred Stock). (2) Accompanied by related warrants to purchase up to 6,593,440 shares of the Company’s common stock (or, if the holder elects to exercise the warrants for shares of Series B1 Preferred Stock, 65,934 shares of Series B1 Preferred Stock), at an exercise price of $1.82 per share (or, if the holder elects to exercise the warrants for Series B1 Preferred Stock, $182 per share of Series B1 Preferred Stock). ​ As consideration for the Future Tranche Rights, the Company received aggregate gross proceeds of $6.2 million (the “Option Fee”) in December 2019. 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 (the “Charter Amendment”), the Company is not required to return the Option Fee. ​ The purchase and sale of the securities issuable under tranches 2, 3 and 4 may occur in up 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 will expire on February 12, 2021 (or 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, if later) , August 12, 2021, and February 12, 2022, respectively. However, the Purchasers’ right to purchase securities under tranches 3 and 4 is contingent on the purchase of all of the securities in each preceding tranche right. In the event the Purchaser’s do not purchase all of the securities in a given tranche, their right to purchase shares in future tranches terminates and any outstanding warrants issued under the December 2019 Securities Purchase Agreement would terminate. Additionally, the Company has the right to decline the Series B4 Preferred Stock investment if its common stock trades at $7.60 for 20 days out of 30 days subsequent to the closing of the Series B3 Preferred Stock investment. ​ In addition to the aggregate gross proceeds received from the Initial Closing and the Option Fee, the Company is eligible, at the discretion of the Purchasers, to receive aggregate gross proceeds of up to an additional $87.6 million under the December 2019 Securities Purchase Agreement. ​ ​ Note 7. Redeemable Convertible Preferred Stock (Continued) ​ Accounting Considerations ​ The Company determined that the Series B1 Preferred Stock, the accompanying Series B1 warrants, and each of the Future Tranche Rights represented a freestanding financial instrument. The warrants and the Future Tranche Rights are liability classified as the underlying shares are potentially redeemable and such redemption is 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 currently 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 being accreted to its redemption value as of September 30, 2020. 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 and nine months ended September 30, 2020, accretion was de minimis.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity
Stockholders' Equity	Note 8. Stockholders’ Equity ​ Common Stock – Authorized Shares ​ On May 12, 2020, the Company’s stockholders approved the Charter Amendment. Also, on May 12, 2020, following stockholder approval, the Company filed the Charter Amendment with the Secretary of State of the State of Delaware. ​ Equity Financings ​ April 2020 Private Placement ​ On April 7, 2020, the Company entered into a Securities Purchase Agreement (the “April 2020 Securities Purchase Agreement”) with Pillar Partners Foundation, L.P. (“Pillar Partners”), a related party as more fully described in Note 11, under which the Company sold 3,039,514 shares of common stock and accompanying warrants to purchase 3,039,514 shares of the Company’s common stock with an exercise price of $2.28 per share, for aggregate gross proceeds of $5.0 million. Each share and the accompanying common warrant had a combined purchase price of $1.645, which included $0.125 for each share of common stock underlying each warrant. ​ In addition, the Company has agreed to sell to Pillar Partners, at its option, 2,747,252 shares of the Company’s common stock (or pre-funded warrants to purchase shares of the Company’s common stock in lieu of certain shares to the extent that purchasing such shares will cause Pillar Investment Entities to beneficially own in excess of 19.99% of the total number of shares of common stock outstanding post transaction) and warrants to purchase up to 1,373,626 shares of the Company’s common stock (with an exercise price of $2.71 ), for aggregate gross proceeds of $5.0 million (the “April 2020 Private Placement Second Closing”). Each share and the accompanying 0.5 common warrant will have a combined purchase price of $1.82 and each pre-funded warrant and the accompanying 0.5 common warrant will have a combined purchase price of $1.81 . The pre-funded warrants issued in the April 2020 Private Placement Second Closing will have an exercise price of $0.01 per share of common stock. The April 2020 Private Placement Second Closing can occur on or before December 30, 2020 (at the option of Pillar Partners) and will be held on or before the fifth day following delivery of written notice by Pillar Partners to the Company; provided that, if at any time after September 30, 2020, the Company’s common stock has achieved a closing price on the Nasdaq Capital Market of at least $3.01 per share for twenty ( 20 ) consecutive trading days, the Company may elect, in its sole discretion, to cancel the April 2020 Private Placement Second Closing. ​ ​ Note 8. Stockholders’ Equity (Continued) ​ Through September 30, 2020, net proceeds received pursuant to the April 2020 Securities Purchase Agreement, after deduction of offering expenses, was $4.7 million. All proceeds have been recorded within the Company’s condensed statements of stockholders’ equity (deficit) as the securities issued pursuant to the April 2020 Securities Purchase Agreement, including the April 2020 Private Placement Second Closing option, were determined to be freestanding equity-classified instruments. ​ July 2020 Private Placement On July 13, 2020, the Company entered into a Securities Purchase Agreement (the “July 2020 Securities Purchase Agreement”) with Pillar Partners, Pillar Pharmaceuticals 6 L.P. (“Pillar 6”), and Pillar Pharmaceuticals 7 L.P. (“Pillar 7”) (collectively, the “July 2020 Purchasers”), each a related party as more fully described in Note 11, under which the Company sold in a private placement transaction (i) 749,993 shares of common stock, (ii) pre-funded warrants to purchase up to 2,014,234 shares of common stock, at an exercise price of $0.01 per share, in lieu of certain shares of common stock to the extent that purchasing such shares would have caused the July 2020 Purchasers to beneficially own in excess of 19.99% of the total number of shares of the Company’s common stock outstanding post transaction, and (iii) warrants to purchase 2,764,227 shares of the Company’s common stock with an exercise price of $2.58 per share, for aggregate gross proceeds of $5.1 million. Each share (or pre-funded warrant) and the accompanying common warrant had a combined purchase price of $1.845, which included $0.125 for each share of common stock underlying each accompanying warrant. ​ In addition, the Company has agreed to sell to the July 2020 Purchasers, at their option, pre-funded warrants to purchase up to 784,615 shares of the Company’s common stock, at an exercise price of $0.01 per share, and warrants to purchase up to 274,615 shares of the Company’s common stock, at an exercise price of $9.75, for aggregate gross proceeds of $5.1 million (the “July 2020 Private Placement Second Closing”). Each pre-funded warrant and the 0.35 associated common warrant will have a combined purchase price of $6.50 ($6.45625 per pre-funded warrant plus $0.04375 per 0.35 associated common warrant). The July 2020 Private Placement Second Closing can occur (at the option of the July 2020 Purchasers) on or before the tenth Business Day following the ORR Data Announcement (as defined in the July 2020 Securities Purchase Agreement) and will be held on or before the fifth day following delivery of written notice by the July 2020 Purchasers to the Company. Through September 30, 2020, net proceeds received pursuant to the July 2020 Securities Purchase Agreement, after deduction of offering expenses, was $5.0 million. All proceeds have been recorded within the Company’s condensed statements of stockholders’ equity (deficit) as the securities issued pursuant to the July 2020 Securities Purchase Agreement, including the July 2020 Private Placement Second Closing option, were determined to be freestanding equity-classified instruments. ​ Common Stock Purchase Agreement ​ On March 4, 2019, the Company entered into a Purchase Agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”), which was amended on September 2, 2020 (as amended to date, the “LPC Agreement”), pursuant to which, upon the terms and subject to the conditions and limitations set forth therein, Lincoln Park has committed to purchase an aggregate of $35.0 million of shares of Company common stock from time to time at the Company’s sole discretion. In connection therewith, the Company issued 269,749 shares of Company common stock to Lincoln Park as a commitment fee (the “Commitment Shares”). The closing price of the Company’s common stock on March 4, 2019 was $2.84 and the Company did not receive any cash proceeds from the issuance of the Commitment Shares. ​ During the nine months ended September 30, 2020 and 2019, the Company sold 600,000 and 785,848 shares pursuant to the LPC Purchase Agreement, resulting in net proceeds of $1.0 million and $2.3 million, respectively, after deduction of offering related costs. As of September 30, 2020, the Company may sell up to an additional $30.2 million of shares under the LPC Purchase Agreement, subject to certain limitations. ​ ​ Note 8. Stockholders’ Equity (Continued) ​ "At-The-Market" Equity Program ​ In November 2018, the Company entered into an Equity Distribution Agreement (the “ATM Agreement”) with JMP Securities LLC (“JMP”) pursuant to which the Company may issue and sell shares of its common stock having an aggregate offering price of up to $50.0 million (the “Shares”) through JMP as its agent. Subject to the terms and conditions of the ATM Agreement, JMP will use its commercially reasonable efforts to sell the Shares from time to time, based upon the Company’s instructions, by methods deemed to be an “at the market offering” as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, or if specified by the Company, by any other method permitted by law, including but not limited to in negotiated transactions. The Company has no obligation to sell any of the Shares, and the Company or JMP may at any time suspend sales under the ATM Agreement or terminate the ATM Agreement. JMP is entitled to a fixed commission of 3.0% of the gross proceeds from Shares sold. During the nine months ended September 30, 2020 and 2019, the Company sold 938,669 and 532,700 Shares, respectively, pursuant to the ATM Agreement, resulting in net proceeds, after deduction of commissions and other offering expenses, of $1.6 million during each nine-month period. As of September 30, 2020, the Company may sell up to an additional $46.6 million of shares under the ATM Agreement. ​ Common Stock Warrants ​ In connection with various financing transactions, the Company has issued warrants to purchase shares of the Company’s common and preferred stock. The Company accounts for common and preferred stock warrants as equity instruments or liabilities, depending on the specific terms of the warrant agreement. ​ The following table summarizes outstanding warrants to purchase shares of the Company’s common and preferred stock as of September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ Weighted-Average ​ ​ Description ​ 2020 ​ 2019 ​ Exercise Price ​ Expiration Date Liability-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ December 2019 Series B1 warrants (1) ​ 2,368,400 ​ 2,368,400 ​ ​ $ 1.52 ​ Dec 2026 ​ ​ 2,368,400 ​ 2,368,400 ​ ​ ​ ​ ​ Equity-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ May 2013 warrants 1,949,754 ​ 1,949,754 ​ ​ $ 0.08 ​ None September 2013 warrants 514,756 ​ 514,756 ​ ​ $ 0.08 ​ None February 2014 warrants 266,006 ​ 266,006 ​ ​ $ 0.08 ​ None April 2020 warrants ​ 3,039,514 ​ — ​ ​ $ 2.28 ​ Apr 2023 July 2020 prefunded warrants ​ 2,014,234 ​ — ​ ​ $ 0.01 ​ None July 2020 warrants ​ 2,764,227 ​ — ​ ​ $ 2.58 ​ Jul 2023 ​ ​ 10,548,491 ​ 2,730,516 ​ ​ ​ ​ ​ Total outstanding 12,916,891 ​ 5,098,916 ​ ​ ​ ​ ​ (1) The Series B1 warrants are 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.

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2020
Collaboration and License Agreements
Collaboration and License Agreements	Note 9. Collaboration and License Agreements ​ Option and License Agreement with Licensee ​ In April 2019, the Company entered into an amended and restated option and license agreement with a privately-held biopharmaceutical company (“Licensee”), pursuant to which the Company granted Licensee (i) exclusive worldwide rights to develop and market IMO-8400 for the treatment, palliation and diagnosis of all diseases, conditions or indications in humans (the “IMO-8400 License”), (ii) an exclusive right and license to develop IMO-9200 in accordance with certain IMO-9200 pre-option exercise protocols (the “IMO-9200 Option Period License”), and (iii) an exclusive option, exercisable at Licensee’s discretion, to obtain the exclusive worldwide rights to develop and market IMO-9200 for the treatment, palliation and diagnosis of all diseases, conditions or indications in humans (the “IMO-9200 Option”) (collectively, the “Licensee Agreement”). In connection with the Licensee Agreement, the Company transferred certain drug material to Licensee for Licensee’s use in development activities. Licensee is solely responsible for the development and commercialization of IMO-8400 and, if Licensee exercises the IMO-9200 Option, Licensee would be solely responsible for the development and commercialization of IMO-9200. ​ Under the terms of the Licensee Agreement, the Company received upfront, non-refundable fees totaling approximately $1.4 million and ownership of 10% of Licensee’s outstanding common stock, subject to future adjustment, for granting Licensee the IMO-8400 License, the IMO-9200 Option Period License and transfer of related drug materials. In addition, the Company is eligible to receive a $1 million non-refundable fee upon Licensee exercising the IMO-9200 Option (“Option Fee”) and is entitled to certain sub-licensing payments on sublicense revenue received by Licensee, if any. The Company may also be eligible for certain development and sales-based milestone payments and royalties on global net sales for any future products. The Company does not anticipate the receipt of any of the future milestones or royalties in the short term, if ever. ​ The Company accounts for the Licensee Agreement in accordance with ASC Topic 606. As of September 30, 2020, the Option Fee and all potential future development/sales milestone payments were fully constrained, and there were no remaining performance obligations under the Licensee Agreement. The Company re-evaluates its performance obligations and the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. As disclosed above, in connection with the Licensee Agreement, the Company owns 10% of Licensee’s outstanding common stock, subject to future adjustment. The Company accounts for the investment using the measurement alternative provided for in ASC Topic 321, Investments-Equity Securities ​ For the nine months ended September 30, 2019, the Company recognized Alliance revenues of $1.4 million under the Licensee Agreement, primarily related to the transfer of the IMO-8400 License and IMO-8400 drug product. No such revenues were recognized during the nine months ended September 30, 2020. ​

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Stock-Based Compensation
Stock-Based Compensation	Note 10. Stock-Based Compensation ​ As of September 30, 2020, 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 (as amended to date, 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 September 30, 2020, options to purchase a total of 4,390,306 shares of common stock and 908,757 RSUs were outstanding and up to 531,681 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 September 30, 2020, options to purchase a total of 327,262 shares of common stock were outstanding under the 2008 Plan. In addition, as of September 30, 2020, non-statutory stock options to purchase an aggregate of 393,750 shares of common stock were outstanding. These options were issued outside of the 2013 Plan to certain newly-hired employees in 2017, 2015 and 2014 pursuant to the Nasdaq inducement grant exception as a material component of such 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. The total number of shares of common stock authorized for issuance under the 2017 ESPP is 412,500 shares of common stock, subject to adjustment as described in the 2017 ESPP. As of September 30, 2020, 262,022 shares remained available for issuance under the 2017 ESPP. ​ For the nine months ended September 30, 2020 and 2019, the Company issued 59,319 and 45,241 shares of common stock, respectively, under the 2017 ESPP and received proceeds of $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 and nine months ended September 30, 2020 and 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ September 30, ​ September 30, (in thousands) ​ 2020 2019 ​ 2020 2019 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 17 $ 9 ​ $ 43 $ 27 Equity Incentive Plans ​ ​ 141 ​ 328 ​ ​ 526 ​ 978 ​ ​ $ 158 $ 337 ​ $ 569 $ 1,005 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ 4 ​ $ 4 $ 18 Equity Incentive Plans ​ ​ 609 ​ 622 ​ ​ 1,700 ​ 1,845 ​ ​ $ 611 $ 626 ​ $ 1,704 $ 1,863 Total stock-based compensation expense ​ $ 769 $ 963 ​ $ 2,273 $ 2,868 ​ During the nine months ended September 30, 2020 and 2019, the weighted average fair market value of stock options granted was $1.25 and $1.83, respectively. ​ The following weighted average assumptions apply to the options to purchase 1,215,382 and 1,259,016 shares of common stock granted to employees and directors during the nine months ended September 30, 2020 and 2019, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2020 2019 Average risk-free interest rate ​ 1.0% ​ ​ 2.1% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 3.8 Expected volatility ​ 83.5% ​ ​ 83.7% Weighted average exercise price (per share) ​ $ 2.08 ​ $ 2.76 ​ All options granted during the nine months ended September 30, 2020 and 2019 were granted at exercise prices equal to the fair market value of the common stock on the dates of grant . ​ ​ Note 10. Stock-Based Compensation (Continued) ​ Stock Option Activity ​ The following table summarizes stock option activity for the nine months ended September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Stock ​ Weighted-Average ​ Weighted-Average ​ Aggregate Intrinsic Value Outstanding at December 31, 2019 4,220,417 ​ $ 13.08 6.6 ​ $ — Granted 1,215,382 ​ ​ 2.08 ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ Forfeited (172,260) ​ ​ 6.45 ​ ​ ​ ​ ​ Expired (152,221) ​ ​ 19.83 ​ ​ ​ ​ ​ Outstanding at September 30, 2020 (1) 5,111,318 ​ $ 10.49 ​ 6.6 ​ $ 231 Exercisable at September 30, 2020 2,803,681 ​ $ 16.06 ​ 4.6 ​ $ — (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. ​ The fair value of options that vested during the nine months ended September 30, 2020 was $2.3 million. As of September 30, 2020, there was $4.2 million of unrecognized compensation cost related to unvested options, which the Company expects to recognize over a weighted average period of 2.4 years. ​ Restricted Stock Activity ​ The following table summarizes restricted stock activity for the nine months ended September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Time-based Awards ​ Market/Performance-based Awards ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average Grant Date Fair Value ​ Number of Shares ​ Weighted-Average Grant Date Fair Value Nonvested shares at December 31, 2019 193,625 ​ $ 3.14 ​ — ​ $ — Granted 237,675 ​ 1.79 ​ 556,888 ​ 1.54 Cancelled (24,270) ​ 2.83 ​ (6,759) ​ 1.54 Vested (48,402) ​ 3.14 ​ — ​ — Nonvested shares at September 30, 2020 358,628 ​ $ 2.27 ​ 550,129 ​ $ 1.54 ​ Time-based Restricted Stock Units ​ As of September 30, 2020, there was $0.6 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 2.8 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 nine months ended September 30, 2020, the Company recognized $0.1 million of compensation expense related to these awards. As of September 30, 2020, 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 2.2 years, is $0.8 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	9 Months Ended
	Sep. 30, 2020
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. As of September 30, 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 13.1% of the Company's outstanding common stock. ​ As of September 30, 2020, Baker Brothers held warrants to purchase up to 2,708,812 shares of the Company’s common stock at an exercise price of $0.08 per share, and warrants to purchase up to 2,368,400 shares of the Company’s common stock (or, if Baker Brothers 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 $1.52 per share (or, if Baker Brothers elects to exercise the warrants for shares of Series B1 Preferred Stock, $152 per Series B1 Preferred Warrant Share). ​ 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, which is the general partner of Pillar Pharmaceuticals I, L.P. (“Pillar I”), Pillar Pharmaceuticals II, L.P. (“Pillar II”), Pillar Pharmaceuticals III, L.P. (“Pillar III”), Pillar Pharmaceuticals IV, L.P. (“Pillar IV”), Pillar Pharmaceuticals V, L.P. (“Pillar V”), Pillar 6”), Pillar 7, and Pillar Partners (collectively, “Pillar”). As of September 30, 2020, Pillar owned approximately 19.9% of the Company's common stock. ​ During the nine months ended September 30, 2020, the Company sold shares of common stock, prefunded warrants and common stock warrants to entities affiliated with Pillar Invest Corporation in connection with private placement transactions, as more fully described in Note 8. ​ As of September 30, 2020, Pillar held (i) warrants to purchase up to 3,039,514 shares of the Company’s common stock at an exercise price of $2.28 per share, (ii) 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 (iii) prefunded warrants to purchase up to 2,014,234 shares of the Company’s common stock at an exercise price of $0.01 per share. Additionally, Pillar held options to purchase Company securities in the April 2020 Private Placement Second Closing and July 2020 Private Placement Second Closing, ​ Board Fees Paid in Stock ​ Pursuant to the Company’s director compensation program, in lieu of director board and committee fees of $0.2 million and $0.1 million during each of the nine months ended September 30, 2020 and 2019, the Company issued 128,799 and 40,158 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 Loss per Common Share

Net Loss per Common Share	9 Months Ended
	Sep. 30, 2020
Net Loss per Common Share
Net Loss per Common Share	Note 12. Net Loss per Common Share ​ The Company uses the two-class method to compute net income (loss) 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. For all periods presented, the two-class method was not applicable. ​ 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 the three and nine months ended September 30, 2020 and 2019, diluted net loss per common share applicable to common stockholders was the same as basic net loss per common share applicable to common stockholders as the effects of the Company’s potential common stock equivalents are antidilutive. Potentially dilutive securities, whose effect would have been antidilutive, were excluded from the computation of diluted earnings per share for each of the three and nine months ended September 30, 2020 and 2019. ​ Total antidilutive securities excluded from the calculation of diluted net loss per share for the three and nine months ended September 30, 2020 and 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ (in thousands) ​ ​ 2020 ​ ​ 2019 Stock options ​ ​ 5,111 ​ ​ 4,394 Restricted stock units ​ ​ 914 ​ ​ 194 Common stock warrants ​ ​ 12,917 ​ ​ 2,765 Convertible preferred stock ​ ​ 2,369 ​ ​ — Future tranche rights ​ ​ 54,588 ​ ​ — Total ​ ​ 75,899 ​ ​ 7,353 ​

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
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. ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
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 and nine months ended September 30, 2020 are not necessarily indicative of results that may be expected for the year ending December 31, 2020. For further information, refer to the financial statements and footnotes thereto included in the Company’s 2019 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 September 30, 2020 and December 31, 2019 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 September 30, 2020 and December 31, 2019, 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 September 30, 2020, the Company did not have any other derivatives, or any hedging 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 credit risk is believed by management to be inherent in the Company’s assets. As of September 30, 2020, all of the Company’s cash, cash equivalents and short-term investments were held at two financial institutions.
Operating Lease Right-of-use Asset and Lease Liability	Operating Lease Right-of-use Assets and Lease Liability ​ The Company accounts for leases under ASC Topic 842, Leases Property, Plant, and Equipment ​ As of September 30, 2020 and December 31, 2019, 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 Topic 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 (the “Purchasers”), an existing stockholder and related party (see Note 11). As more fully described in Note 7, the December 2019 Securities Purchase Agreement contains call options on redeemable preferred shares with warrants (conditionally exercisable for shares that are puttable). The Company determined that these call options represent freestanding financial instruments and accounts 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 (Loss) Gain in the Company’s condensed statements of operations and comprehensive loss. ​ As of September 30, 2020, the Future Tranche Right Liability is classified as a long-term liability in the Company’s condensed balance sheet as settlement is in the form of the applicable Series B convertible preferred stock and warrants exercisable for shares of either Series B1 Preferred Stock or the Company’s common stock. As of December 31, 2019, the Future Tranche Right Liability was classified as a current liability because the Future Tranche Rights and related Option Fee, each defined in Note 7, were subject to the Company obtaining required shareholder approval, which was obtained in May 2020.
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 Topic 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 ​ Financial Instruments Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ​ In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurement Fair Value Measurement ​ Recently Issued (But Not Yet Adopted) Accounting Pronouncements ​ In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity
COVID-19	COVID-19 ​ While the Company is not aware of a material impact from the novel coronavirus disease ("COVID-19") pandemic through September 30, 2020, 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)	9 Months Ended
	Sep. 30, 2020
Schedule of assets and liabilities measured and recorded in financial statements at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 22,082 ​ ​ 22,082 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 5,647 ​ — ​ 5,647 ​ — Short-term investments – US treasury bills ​ 1,000 ​ — ​ 1,000 ​ — Total assets ​ $ 28,979 ​ $ 22,332 ​ $ 6,647 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,736 ​ $ — ​ $ — ​ $ 3,736 Future tranche right liability ​ ​ 53,424 ​ ​ — ​ ​ — ​ ​ 53,424 Total liabilities ​ $ 57,160 ​ $ — ​ $ — ​ $ 57,160 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 39,769 ​ ​ 39,769 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 2,774 ​ — ​ 2,774 ​ — Total assets ​ $ 42,793 ​ $ 40,019 ​ $ 2,774 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,241 ​ $ — ​ $ — ​ $ 3,241 Future tranche right liability ​ ​ 46,436 ​ ​ — ​ ​ — ​ ​ 46,436 Total liabilities ​ $ 49,677 ​ $ — ​ $ — ​ $ 49,677
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, 2019 $ 3,241 ​ $ 46,436 Change in the fair value of liability 495 ​ 6,988 Balance, September 30, 2020 $ 3,736 ​ $ 53,424
Warrant liability
Schedule of assumptions used in determining fair value	​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.35% ​ ​ 1.79% Expected dividend yield ​ — ​ ​ — Expected term (years) ​ 6.23 ​ ​ 6.98 Expected volatility ​ 80% ​ ​ 80% Exercise price (per share) $ 1.52 ​ $ 1.52
Future tranche right liability
Schedule of assumptions used in determining fair value	​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.45% - 0.53% ​ ​ 1.84% - 1.88% Expected dividend yield ​ — ​ ​ — Expected term (years) of call options on preferred stock ​ 0.41 - 1.37 ​ ​ 1.16 - 2.16 Expected term (years) of warrants ​ 7.41 - 8.37 ​ ​ 8.16 - 9.16 Expected volatility ​ 80% ​ ​ 80% Exercise price (per share) for common stock equivalent for preferred stock and warrant $ 1.52 - 1.82 ​ $ 1.52 - 1.82

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2020
Investments
Schedule of available-for-sale investments at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ Gross Gross Estimated ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Cost ​ (Losses) ​ Gains ​ Value Short-term investments – commercial paper ​ $ 5,647 ​ $ — ​ $ — ​ $ 5,647 Short-term investments – US treasury bills ​ ​ 1,000 ​ ​ — ​ ​ — ​ ​ 1,000 Total short-term investments ​ $ 6,647 ​ $ — ​ $ — ​ $ 6,647 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ Gross ​ Gross ​ Estimated ​ ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) Cost (Losses) Gains Value Short-term investments – commercial paper ​ $ 2,774 ​ $ — ​ $ — ​ $ 2,774 Total short-term investments ​ $ 2,774 ​ $ — ​ $ — ​ $ 2,774

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2020
Property and Equipment
Schedule of net property and equipment at cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) 2020 2019 Leasehold improvements ​ $ 107 ​ $ 107 Equipment and other ​ 770 ​ 764 Total property and equipment, at cost ​ $ 877 ​ $ 871 Less: Accumulated depreciation and amortization ​ 825 ​ 774 Property and equipment, net ​ $ 52 ​ $ 97 ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, (In thousands) ​ 2020 2019 Payroll and related costs ​ $ 2,294 ​ $ 2,179 Clinical and nonclinical trial expenses ​ 3,397 ​ 4,199 Professional and consulting fees ​ 493 ​ 859 Restructuring expenses ​ — ​ 113 Other ​ 124 ​ 111 Total accrued expenses ​ $ 6,308 ​ $ 7,461

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2020
Redeemable Convertible Preferred Stock
Schedule of Redeemable Convertible Preferred Stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Price Per ​ ​ Aggregate Future Tranche Rights ​ Preferred Shares ​ Share ​ ​ Purchase Price Tranche 2 (Series B2) (1) ​ 98,685 ​ $ 152 ​ $ 15,000,120 Tranche 3 (Series B3) (2) ​ 82,418 ​ $ 182 ​ ​ 15,000,076 Tranche 4 (Series B4) (2) ​ 82,418 ​ $ 182 ​ ​ 15,000,076 Total ​ 263,521 ​ ​ ​ ​ $ 45,000,272 (1) Accompanied by related warrants to purchase up to 9,868,500 shares of the Company’s common stock (or, if the holder elects to exercise the warrants for shares of Series B1 Preferred Stock, 98,685 shares of Series B1 Preferred Stock), at an exercise price of $1.52 per share (or, if the holder elects to exercise the warrants for Series B1 Preferred Stock, $152 per share of Series B1 Preferred Stock). (2) Accompanied by related warrants to purchase up to 6,593,440 shares of the Company’s common stock (or, if the holder elects to exercise the warrants for shares of Series B1 Preferred Stock, 65,934 shares of Series B1 Preferred Stock), at an exercise price of $1.82 per share (or, if the holder elects to exercise the warrants for Series B1 Preferred Stock, $182 per share of Series B1 Preferred Stock). ​

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Stockholders' Equity
Schedule of warrants outstanding and exercisable for purchase of common stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ Weighted-Average ​ ​ Description ​ 2020 ​ 2019 ​ Exercise Price ​ Expiration Date Liability-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ December 2019 Series B1 warrants (1) ​ 2,368,400 ​ 2,368,400 ​ ​ $ 1.52 ​ Dec 2026 ​ ​ 2,368,400 ​ 2,368,400 ​ ​ ​ ​ ​ Equity-classified Warrants ​ ​ ​ ​ ​ ​ ​ ​ ​ May 2013 warrants 1,949,754 ​ 1,949,754 ​ ​ $ 0.08 ​ None September 2013 warrants 514,756 ​ 514,756 ​ ​ $ 0.08 ​ None February 2014 warrants 266,006 ​ 266,006 ​ ​ $ 0.08 ​ None April 2020 warrants ​ 3,039,514 ​ — ​ ​ $ 2.28 ​ Apr 2023 July 2020 prefunded warrants ​ 2,014,234 ​ — ​ ​ $ 0.01 ​ None July 2020 warrants ​ 2,764,227 ​ — ​ ​ $ 2.58 ​ Jul 2023 ​ ​ 10,548,491 ​ 2,730,516 ​ ​ ​ ​ ​ Total outstanding 12,916,891 ​ 5,098,916 ​ ​ ​ ​ ​ (1) The Series B1 warrants are 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.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
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 ​ Nine Months Ended ​ September 30, ​ September 30, (in thousands) ​ 2020 2019 ​ 2020 2019 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 17 $ 9 ​ $ 43 $ 27 Equity Incentive Plans ​ ​ 141 ​ 328 ​ ​ 526 ​ 978 ​ ​ $ 158 $ 337 ​ $ 569 $ 1,005 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plan ​ $ 2 $ 4 ​ $ 4 $ 18 Equity Incentive Plans ​ ​ 609 ​ 622 ​ ​ 1,700 ​ 1,845 ​ ​ $ 611 $ 626 ​ $ 1,704 $ 1,863 Total stock-based compensation expense ​ $ 769 $ 963 ​ $ 2,273 $ 2,868
Schedule of weighted average assumptions applied to options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ ​ September 30, ​ 2020 2019 Average risk-free interest rate ​ 1.0% ​ ​ 2.1% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 3.8 Expected volatility ​ 83.5% ​ ​ 83.7% Weighted average exercise price (per share) ​ $ 2.08 ​ $ 2.76
Schedule of information related to outstanding and exercisable options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Stock ​ Weighted-Average ​ Weighted-Average ​ Aggregate Intrinsic Value Outstanding at December 31, 2019 4,220,417 ​ $ 13.08 6.6 ​ $ — Granted 1,215,382 ​ ​ 2.08 ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ Forfeited (172,260) ​ ​ 6.45 ​ ​ ​ ​ ​ Expired (152,221) ​ ​ 19.83 ​ ​ ​ ​ ​ Outstanding at September 30, 2020 (1) 5,111,318 ​ $ 10.49 ​ 6.6 ​ $ 231 Exercisable at September 30, 2020 2,803,681 ​ $ 16.06 ​ 4.6 ​ $ — (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.

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	9 Months Ended
	Sep. 30, 2020
Net Loss per Common Share
Schedule of potentially dilutive securities excluded from diluted net income (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ (in thousands) ​ ​ 2020 ​ ​ 2019 Stock options ​ ​ 5,111 ​ ​ 4,394 Restricted stock units ​ ​ 914 ​ ​ 194 Common stock warrants ​ ​ 12,917 ​ ​ 2,765 Convertible preferred stock ​ ​ 2,369 ​ ​ — Future tranche rights ​ ​ 54,588 ​ ​ — Total ​ ​ 75,899 ​ ​ 7,353

Business and Organization (Deta

Business and Organization (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Business and Organization
Accumulated deficit	$ 756,851	$ 720,890
Cash, cash equivalents and investments	$ 29,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)Institution	Sep. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Summary of Significant Accounting Policies
Number of financial institutions | Institution			2
Tax expense (benefit)	$ 0	$ 0	$ 0	$ 0
Effect of recently adopted accounting pronouncements	(32,435)	$ 37,626	(32,435)	$ 37,626	$ (17,691)	$ (144)	$ (11,168)	$ 47,735	$ 55,672	$ 63,994
Uncertain tax positions	$ 0		$ 0				$ 0

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
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	Sep. 30, 2020	Dec. 31, 2019
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Cash equivalents and Short-term investments	$ 6,647	$ 2,774
Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	28,979	42,793
Total Liabilities	57,160	49,677
Fair value on a recurring basis | Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Liabilities	3,736	3,241
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	53,424	46,436
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	22,082	39,769
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	5,647	2,774
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	22,332	40,019
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	22,082	39,769
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	6,647	2,774
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	5,647	2,774
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	57,160	49,677
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	3,736	3,241
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	$ 53,424	$ 46,436

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	9 Months Ended
	Sep. 30, 2020USD ($)
Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Beginning balance	$ 3,241
Change in the fair value of liability	495
Ending balance	3,736
Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Beginning balance	46,436
Change in the fair value of liability	6,988
Ending balance	$ 53,424

Fair Value Measurements - Weigh

Fair Value Measurements - Weighted-average assumptions (Details)	Sep. 30, 2020USD ($)$ / shares	Dec. 31, 2019$ / sharesUSD ($)
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques
Debt instrument measurement input	0.35	1.79
Expected term
Fair Value Measurement Inputs and Valuation Techniques
Debt instrument measurement input | $	6.23	6.98
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques
Debt instrument measurement input	80	80
Exercise price
Fair Value Measurement Inputs and Valuation Techniques
Debt instrument measurement input | $ / shares	1.52	1.52

Fair Value Measurements - Futur

Fair Value Measurements - Future Tranche Rights (Details)	Sep. 30, 2020USD ($)$ / shares	Dec. 31, 2019$ / sharesUSD ($)
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.35	1.79
Risk-free interest rate | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.45	1.84
Risk-free interest rate | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.53	1.88
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input | $	6.23	6.98
Expected term | Warrants | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	7.41	8.16
Expected term | Warrants | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	8.37	9.16
Expected term | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.41	1.16
Expected term | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.37	2.16
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	80	80
Expected volatility | Future tranche right liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	80	80
Exercise price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input | $ / shares	1.52	1.52
Exercise price | Future tranche right liability | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.52	1.52
Exercise price | Future tranche right liability | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.82	1.82

Fair Value Measurements - Chart

Fair Value Measurements - Charter Amendment (Details) - $ / shares	Sep. 30, 2020	May 12, 2020	Dec. 31, 2019
Fair Value Measurements
Common Stock, Shares Authorized	140,000,000	140,000,000	140,000,000
Common Stock, Par or Stated Value Per Share	$ 0.001		$ 0.001

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Investments at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Short-term investments
Schedule of Available-for-sale Securities
Cost	$ 6,647	$ 2,774
Estimated Fair Value	6,647	2,774
Short-term investments - commercial paper
Schedule of Available-for-sale Securities
Cost	5,647	2,774
Estimated Fair Value	5,647	$ 2,774
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	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Investments
Realized gains or losses	$ 0	$ 0
Allowance for credit losses on available-for-sale debt securities	0		$ 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	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment
Total property and equipment, at cost	$ 877	$ 871
Less: Accumulated depreciation and amortization	825	774
Property and equipment, net	52	97
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	$ 770	$ 764

Property and Equipment - Deprec

Property and Equipment - Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Non-cash property additions	$ 0	$ 0	$ 0	$ 0
Maximum
Depreciation and amortization expense on property and equipment	$ 100	$ 100	$ 100	$ 100

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Expenses
Payroll and related costs	$ 2,294	$ 2,179
Clinical and nonclinical trial expenses	3,397	4,199
Professional and consulting fees	493	859
Restructuring expenses		113
Other	124	111
Total accrued expenses	$ 6,308	$ 7,461

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock (Details) - USD ($)	Dec. 23, 2019	Sep. 30, 2020	Sep. 30, 2019
Temporary Equity
Aggregate gross proceeds	$ 3,900,000	$ 12,258,000	$ 3,857,000
Preferred Shares		263,521
Aggregate Purchase Price		$ 45,000,272
Gross proceeds	$ 6,200,000
Common stock trading Price	$ 7.60
Common stock trading Price, Number of trading days	20 days
Common stock trading Price, Number of trading days Subsequent to closing	30 days
Aggregate gross proceeds	$ 87,600,000
Series B1 redeemable convertible preferred stock
Temporary Equity
Sale of redeemable convertible preferred stock	23,684
Series B1 redeemable convertible preferred stock | Common stock warrants
Temporary Equity
Warrant to purchase common stock	2,368,400
Warrant exercise price (per share)	$ 1.52
Series B1 redeemable convertible preferred stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase common stock	23,684
Warrant exercise price (per share)	$ 152
Series B2 Redeemable Convertible Preferred Stock
Temporary Equity
Preferred Shares		98,685
Share Price		$ 152
Aggregate Purchase Price		$ 15,000,120
Series B2 Redeemable Convertible Preferred Stock | Common stock warrants
Temporary Equity
Sale of redeemable convertible preferred stock		9,868,500
Warrant exercise price (per share)		$ 1.52
Series B2 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase common stock		98,685
Warrant exercise price (per share)		$ 152
Series B3 Redeemable Convertible Preferred Stock
Temporary Equity
Preferred Shares		82,418
Share Price		$ 182
Aggregate Purchase Price		$ 15,000,076
Series B3 Redeemable Convertible Preferred Stock | Common stock warrants
Temporary Equity
Warrant to purchase common stock		6,593,440
Warrant exercise price (per share)		$ 1.82
Series B3 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Warrant to purchase common stock		65,934
Warrant exercise price (per share)		$ 182
Series B4 Redeemable Convertible Preferred Stock
Temporary Equity
Preferred Shares		82,418
Share Price		$ 182
Aggregate Purchase Price		$ 15,000,076
Expiration period	21 months

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 13, 2020	Apr. 07, 2020	Dec. 23, 2019	Mar. 04, 2019	Nov. 30, 2018	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	May 12, 2020	Dec. 31, 2019
Class of Stock
Par value (per share)						$ 0.001	$ 0.001	$ 0.001			$ 0.001
Shares authorized (in shares)						140,000,000	140,000,000	140,000,000		140,000,000	140,000,000
Proceeds from issuance			$ 3,900					$ 12,258	$ 3,857
"At-The-Market" Equity Program
Class of Stock
Value of shares investor has committed to purchase from time to time at Company's sole discretion						$ 46,600	$ 46,600	$ 46,600
Stock issued (in shares)								938,669	532,700
Net proceeds from offering of common stock								$ 1,600	$ 1,600
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 from time to time at Company's sole discretion				$ 35,000		$ 30,200	$ 30,200	$ 30,200
Stock issued (in shares)				269,749				600,000	785,848
Stock issued (per share)				$ 2.84
Net proceeds from offering of common stock								$ 1,000	$ 2,300
Common Stock | "At-The-Market" Equity Program
Class of Stock
Net proceeds from offering of common stock					$ 50,000
Baker Bros. Advisors LP
Class of Stock
Ownership percentage						13.10%	13.10%	13.10%
Pillar Investment Entities
Class of Stock
Stock issued (in shares)		3,039,514
Ownership percentage	19.99%					19.90%	19.90%	19.90%
Shares of common stock that may be purchased upon exercise of warrants		3,039,514
Warrant exercise price (per share)		$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5,100	$ 5,000
Combined purchase price (per share)	$ 1.845	$ 1.645
Stock price underlying warrants (per share)	$ 0.125	$ 0.125
Net proceeds from offering of common stock						$ 5,000
Net proceeds from offering of common stock							$ 4,700
Pillar Investment Entities | Common stock warrants
Class of Stock
Shares of common stock that may be purchased upon exercise of warrants	2,764,227
Warrant exercise price (per share)	$ 2.58
Pillar Investment Entities | Pre-funded Warrants
Class of Stock
Stock issued (in shares)	749,993
Shares of common stock that may be purchased upon exercise of warrants	2,014,234					2,014,234	2,014,234	2,014,234
Warrant exercise price (per share)	$ 0.01					$ 0.01	$ 0.01	$ 0.01
Pillar Investment Entities | Future plans
Class of Stock
Stock issued (in shares)		2,747,252
Ownership percentage		19.99%
Shares of common stock that may be purchased upon exercise of warrants		1,373,626
Warrant exercise price (per share)		$ 2.71
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5,100	$ 5,000
Number of common warrants	0.35	0.5
Stock price (in dollars per share)	$ 6.50	$ 3.01
Number of consecutive trading days		20 days
Pillar Investment Entities | Future plans | Common stock warrants
Class of Stock
Shares of common stock that may be purchased upon exercise of warrants	274,615
Warrant exercise price (per share)	$ 9.75
Stock price (in dollars per share)	$ 0.04375
Combined purchase price (per share)		$ 1.82
Pillar Investment Entities | Future plans | Pre-funded Warrants
Class of Stock
Stock issued (in shares)	784,615
Warrant exercise price (per share)	$ 0.01	0.01
Stock price (in dollars per share)	$ 6.45625
Combined purchase price (per share)		$ 1.81

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Class of Warrant or Right
Number of Warrants	12,916,891	5,098,916
Warrants
Class of Warrant or Right
Warrant exercise price per share	$ 1.52
Preferred stock
Class of Warrant or Right
Warrant exercise price per share	$ 152
Liability Classified Warrants
Class of Warrant or Right
Number of Warrants	2,368,400	2,368,400
December 2019 Series B1 warrants
Class of Warrant or Right
Number of Warrants	2,368,400	2,368,400
Warrant exercise price per share	$ 1.52	$ 1.52
Equity Classified Warrants
Class of Warrant or Right
Number of Warrants	10,548,491	2,730,516
May 2013 Warrants
Class of Warrant or Right
Number of Warrants	1,949,754	1,949,754
Warrant exercise price per share	$ 0.08	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Warrants	514,756	514,756
Warrant exercise price per share	$ 0.08	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Warrants	266,006	266,006
Warrant exercise price per share	$ 0.08
April 2020 Warrants
Class of Warrant or Right
Number of Warrants	3,039,514
Warrant exercise price per share	$ 2.28
July 2020 Prefunded Warrants
Class of Warrant or Right
Number of Warrants	2,014,234
Warrant exercise price per share	$ 0.01
July 2020 Warrants
Class of Warrant or Right
Number of Warrants	2,764,227
Warrant exercise price per share	$ 2.58

Stockholders' Equity - Proceeds

Stockholders' Equity - Proceeds from Sale of Common Stock (Details) - Pillar Investment Entities - USD ($) $ / shares in Units, $ in Millions	Jul. 13, 2020	Apr. 07, 2020	Sep. 30, 2020
Class of Stock [Line Items]
Stock issued (in shares)		3,039,514
Shares of common stock that may be purchased upon exercise of warrants		3,039,514
Warrant exercise price (per share)		$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1	$ 5
Net proceeds from offering of common stock			$ 5
Combined purchase price (per share)	$ 1.845	$ 1.645
Stock price underlying warrants (per share)	$ 0.125	$ 0.125
Ownership percentage	19.99%		19.90%
Common stock warrants
Class of Stock [Line Items]
Shares of common stock that may be purchased upon exercise of warrants	2,764,227
Warrant exercise price (per share)	$ 2.58
Pre-funded Warrants
Class of Stock [Line Items]
Stock issued (in shares)	749,993
Shares of common stock that may be purchased upon exercise of warrants	2,014,234		2,014,234
Warrant exercise price (per share)	$ 0.01		$ 0.01
Future plans
Class of Stock [Line Items]
Stock issued (in shares)		2,747,252
Shares of common stock that may be purchased upon exercise of warrants		1,373,626
Warrant exercise price (per share)		$ 2.71
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1	$ 5
Ownership percentage		19.99%
Number of common warrants	0.35	0.5
Stock price (in dollars per share)	$ 6.50	$ 3.01
Number of consecutive trading days		20 days
Future plans | Common stock warrants
Class of Stock [Line Items]
Shares of common stock that may be purchased upon exercise of warrants	274,615
Warrant exercise price (per share)	$ 9.75
Combined purchase price (per share)		$ 1.82
Stock price (in dollars per share)	$ 0.04375
Future plans | Pre-funded Warrants
Class of Stock [Line Items]
Stock issued (in shares)	784,615
Warrant exercise price (per share)	$ 0.01	0.01
Combined purchase price (per share)		$ 1.81
Stock price (in dollars per share)	$ 6.45625

Collaboration and License Agr_2

Collaboration and License Agreements (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Alliance revenue					$ 1,448,000
Operating expenses		$ 7,484,000	$ 11,387,000	$ 28,647,000	35,727,000
Option and License Agreement with Licensee
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Alliance revenue				0	$ 1,400,000
Performance obligation		0		$ 0
Percentage of shares acquired				10.00%
Maximum | Option and License Agreement with Licensee | Other Assets
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Value of securities without a readily determinable fair value		$ 100,000		$ 100,000
IMO-9200 License | Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement	$ 1,400,000
Non-refundable fee upon exercise of option	$ 1,000,000
IMO-9200 License | Option and License Agreement with Licensee
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Percentage of shares acquired	10.00%

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive Plans (Details) - shares	1 Months Ended	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Class of Stock
Common stock options outstanding		5,111,318	4,220,417
Options outstanding under earlier plans		327,262
Grant of inducement stock option		393,750
2013 Stock Incentive Plan
Class of Stock
Common stock, shares reserved for future issuance	5,653,057
Common shares available for grant		531,681
Maximum number of additional common shares	868,372
Common stock options outstanding		4,390,306
Restricted stock units outstanding		908,757

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jun. 07, 2017
Class of Stock
Proceeds from employee stock purchases	$ 84	$ 97
2017 Employee Stock Purchase Plan
Class of Stock
Common stock shares authorized for issuance under stock purchase plan			412,500
Proceeds from employee stock purchases	$ 100	$ 100
Common shares available for grant			262,022
Employee Stock Purchase Plan
Class of Stock
Common stock share issued	59,319	45,241

Stock-Based Compensation - Acco

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
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)			$ 1.25	$ 1.83
Stock-based compensation	$ 769	$ 963	$ 2,273	$ 2,868
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	158	337	569	1,005
Research and development | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	17	9	43	27
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	141	328	526	978
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	611	626	1,704	1,863
General and administrative | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	2	4	4	18
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 609	$ 622	$ 1,700	$ 1,845

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used in Determining Fair Value of Stock Options (Details) - $ / shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Summary of Significant Accounting Policies
Options to purchase common stock granted to employees and directors	1,215,382	1,259,016
Average risk free interest rate	1.00%	2.10%
Dividend rate	0.00%	0.00%
Expected lives (years)	3 years 10 months 24 days	3 years 9 months 18 days
Expected volatility	83.50%	83.70%
Weighted average exercise price of options granted during the period (per share)	$ 2.08	$ 2.76

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Options, Outstanding, Beginning Balance	4,220,417
Granted	1,215,382
Forfeited	(172,260)
Expired	(152,221)
Options, Outstanding, Ending Balance	5,111,318		4,220,417
Exercisable, Ending Balance	2,803,681
Weighted Average Exercise Price, Beginning Balance	$ 13.08
Granted, Weighted Average Exercise Price	2.08	$ 2.76
Forfeited, Weighted Average Exercise Price	6.45
Expired, Weighted Average Exercise Price	19.83
Weighted Average Exercise Price, Ending Balance	10.49		$ 13.08
Exercisable, Weighted Average Exercise Price	$ 16.06
Outstanding, Ending balance, Weighted Average Remaining Contractual Term	6 years 7 months 6 days		6 years 7 months 6 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term	4 years 7 months 6 days
Outstanding, Intrinsic Value, Ending Balance	$ 231
Fair value of options, vested	2,300
Unrecognized compensation cost related to nonvested stock-based compensation	$ 4,200
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 4 months 24 days
Time-based Awards
Unrecognized compensation cost related to nonvested stock-based compensation	$ 600
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 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		9 Months Ended
	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Unrecognized compensation expense		$ 4,200		$ 4,200
Weighted average remaining period over which unrecognized compensation expense will be recognized				2 years 4 months 24 days
Share-based compensation		$ 769	$ 963	$ 2,273	$ 2,868
Time-based Awards
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance				193,625
Granted				237,675
Cancelled				(24,270)
Vested				(48,402)
Nonvested shares, Ending Balance		358,628		358,628
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance				$ 3.14
Granted, Weighted-Average Grant Date Fair Value				1.79
Cancelled, Weighted-Average Grant Date Fair Value				2.83
Vested, Weighted-Average Grant Date Fair Value				3.14
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 2.27		$ 2.27
Unrecognized compensation expense		$ 600		$ 600
Weighted average remaining period over which unrecognized compensation expense will be recognized				2 years 9 months 18 days
Market/Performance-based Awards
Restricted Stock Activity, Number of Shares
Granted				556,888
Cancelled				(6,759)
Nonvested shares, Ending Balance		550,129		550,129
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Granted, Weighted-Average Grant Date Fair Value				$ 1.54
Cancelled, Weighted-Average Grant Date Fair Value				1.54
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance		$ 1.54		$ 1.54
Weighted average remaining period over which unrecognized compensation expense will be recognized				2 years 2 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		$ 800		800
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	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jul. 13, 2020	Apr. 07, 2020	Dec. 31, 2019
Related Party Transactions
Number of Warrants	12,916,891				5,098,916
Proceeds from issuance of common stock in lieu of director board and committee fees	$ 0.2	$ 0.1
Common stock issued in lieu of board fees	128,799	40,158
Baker Bros. Advisors LP
Related Party Transactions
Ownership percentage	13.10%
Aggregate common shares	4,608,786
Baker Bros. Advisors LP | Pre-funded Warrants | Scenario One
Related Party Transactions
Exercise price of warrants	$ 0.08
Baker Bros. Advisors LP | Pre-funded Warrants | Scenario One | Maximum
Related Party Transactions
Number of Shares	2,708,812
Baker Bros. Advisors LP | Series B1 Preferred Warrant | Scenario One
Related Party Transactions
Exercise price of warrants	$ 1.52
Number of Warrants	23,684
Baker Bros. Advisors LP | Series B1 Preferred Warrant | Scenario Two
Related Party Transactions
Exercise price of warrants	$ 152
Baker Bros. Advisors LP | Series B1 Preferred Warrant | Scenario Two | Maximum
Related Party Transactions
Number of Shares	2,368,400
Pillar Investment Entities
Related Party Transactions
Ownership percentage	19.90%		19.99%
Exercise price of warrants				$ 2.28
Number of Shares				3,039,514
Pillar Investment Entities | Scenario One
Related Party Transactions
Exercise price of warrants	$ 2.28
Number of Shares	3,039,514
Pillar Investment Entities | Scenario Two
Related Party Transactions
Exercise price of warrants	$ 2.58
Number of Shares	2,764,227
Pillar Investment Entities | Pre-funded Warrants
Related Party Transactions
Exercise price of warrants	$ 0.01		$ 0.01
Number of Shares	2,014,234		2,014,234

Net Loss per Common Share (Deta

Net Loss per Common Share (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Net loss per share - Basic:
Net loss	$ (20,552)	$ (24,226)	$ 8,817	$ (11,133)	$ (11,176)	$ (10,974)	$ (35,961)	$ (33,283)
Net loss per share - Diluted:
Net loss	$ (20,552)	$ (24,226)	$ 8,817	$ (11,133)	$ (11,176)	$ (10,974)	$ (35,961)	$ (33,283)

Net Loss per Common Share - Ant

Net Loss per Common Share - Antidilutive securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive securities
Total antidilutive securities	75,899	7,353
Stock options
Antidilutive securities
Total antidilutive securities	5,111	4,394
Time-based Awards
Antidilutive securities
Total antidilutive securities	914	194
Common stock warrants
Antidilutive securities
Total antidilutive securities	12,917	2,765
Convertible preferred stock
Antidilutive securities
Total antidilutive securities	2,369
Future tranche right liability
Antidilutive securities
Total antidilutive securities	54,588