Aceragen (ACGN) 10-Q 4 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 31, 2020
Document and Entity Information
Document Type	10-Q
Document Period End Date	Jun. 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		35,199,246
Entity Central Index Key	0000861838
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 27,810	$ 40,019
Short-term investments	3,196	2,774
Prepaid expenses and other current assets	2,681	3,475
Total current assets	33,687	46,268
Property and equipment, net	63	97
Operating lease right-of-use asset	965	1,054
Other assets	70	70
Total assets	34,785	47,489
Current liabilities:
Accounts payable	345	457
Accrued expenses	7,023	7,461
Operating lease liability	166	163
Future tranche right liability		46,436
Total current liabilities	7,534	54,517
Warrant liability, long-term	3,053	3,241
Future tranche right liability, long-term	41,074
Operating lease liability, net of current portion	815	899
Total liabilities	52,476	58,657
Commitments and contingencies
Stockholders' equity (deficit)
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 34,291 and 29,672 at June 30, 2020 and December 31, 2019, respectively	34	30
Additional paid-in capital	718,574	709,692
Accumulated deficit	(736,299)	(720,890)
Total stockholders' deficit	(17,691)	(11,168)
Total liabilities and stockholders' deficit	34,785	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	Jun. 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	34,291,000	29,672,000
Common stock, shares outstanding	34,291,000	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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Alliance revenue		$ 1,448		$ 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	$ 5,379	$ 10,024	$ 14,889	$ 18,126
General and administrative	2,632	2,895	6,274	6,038
Restructuring costs		45		176
Total operating expenses	8,011	12,964	21,163	24,340
Loss from operations	(8,011)	(11,516)	(21,163)	(22,892)
Other income (expense):
Interest income	27	339	152	743
Warrant revaluation (loss) gain	(913)		188
Future tranche right revaluation (loss) gain	(15,349)		5,362
Foreign currency exchange gain (loss)	20	1	52	(1)
Net loss	$ (24,226)	$ (11,176)	$ (15,409)	$ (22,150)
Net loss per share applicable to common stockholders (Note 12)
Basic	$ (0.72)	$ (0.39)	$ (0.48)	$ (0.79)
Diluted	$ (0.72)	$ (0.39)	$ (0.52)	$ (0.79)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders
Basic	33,583	28,461	31,941	28,070
Diluted	33,583	28,461	34,123	28,070
Comprehensive loss:
Net loss	$ (24,226)	$ (11,176)	$ (15,409)	$ (22,150)
Unrealized gain on available-for-sale securities				2
Total other comprehensive income				2
Comprehensive loss	$ (24,226)	$ (11,176)	$ (15,409)	$ (22,148)

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash Flows from Operating Activities:
Net loss	$ (15,409)	$ (22,150)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,504	1,905
Warrant liability revaluation gain	(188)
Future tranche right liability revaluation gain	(5,362)
Issuance of common stock for services rendered	98	59
Accretion of discounts on short-term investments	(36)	(353)
Unrealized gain on available-for-sale securities		2
Depreciation and amortization expense	41	67
Gain on disposal of property and equipment		(11)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	819	(423)
Accounts payable, accrued expenses, and other liabilities	(575)	(2,426)
Other	8
Net cash used in operating activities	(19,100)	(23,330)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(5,535)	(35,486)
Proceeds from maturity of available-for-sale securities	5,149	23,350
Proceeds from the sale of property and equipment		11
Purchases of property and equipment	(7)	(11)
Net cash used in investing activities	(393)	(12,136)
Cash Flows from Financing Activities:
Proceeds from common stock financings, net	7,230	3,857
Proceeds from employee stock purchases	54	68
Other		(6)
Net cash provided by financing activities	7,284	3,919
Net decrease in cash and cash equivalents	(12,209)	(31,547)
Cash and cash equivalent, beginning of period	40,019	71,431
Cash and cash equivalents, end of period	27,810	39,884
Supplemental disclosure of cash flow information:
Increase to right-of-use asset upon adoption of ASC 842		261
Increase to lease liability upon adoption of ASC 842		$ 261
Supplemental disclosure of non-cash financing and investing activities:
Capitalized offering costs in accounts payable and accrued expenses	$ 25

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
Beginning balance at Dec. 31, 2018	$ 27	$ 728,342	$ (664,375)			$ 63,994
Beginning balance (in shares) at Dec. 31, 2018	27,188
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
Net income (loss)						(22,150)
Ending balance at Jun. 30, 2019	$ 29	734,229	(686,525)	2		47,735
Ending balance (in shares) at Jun. 30, 2019	28,827
Beginning balance at Mar. 31, 2019	$ 28	730,991	(675,349)	2		55,672
Beginning balance (in shares) at Mar. 31, 2019	28,008
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
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
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
Net income (loss)						$ (15,409)
Ending balance at Jun. 30, 2020	$ 34	718,574	(736,299)			$ (17,691)
Ending balance (in shares) at Jun. 30, 2020	34,291				24	34,291
Beginning balance at Mar. 31, 2020	$ 31	711,898	(712,073)			$ (144)
Beginning balance (in shares) at Mar. 31, 2020	30,607				24
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	34,291

Business and Organization

Business and Organization	6 Months Ended
	Jun. 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 June 30, 2020, the Company had an accumulated deficit of $736.3 million and a cash, cash equivalents, and short-term investments balance of $31.0 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	6 Months Ended
	Jun. 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 six months ended June 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 June 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 June 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 June 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, 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 June 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 ​ The Company accounts for leases under ASC Topic 842, Leases Property, Plant, and Equipment ​ As of June 30, 2020 and December 31, 2019, the Company’s operating lease ROU asset and corresponding short-term and long-term lease liabilities relate to its existing Exton, PA facility operating lease which expires on May 31, 2025 as a result of the Company’s election to exercise its five-year renewal option in January 2020. ​ ​ 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 June 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 as the Future Tranche Rights and related Option Fee, each defined in Note 7, were subject to the Company obtaining required shareholder approval and filing the Charter Amendment, as defined in Note 3. ​ 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 ​ COVID-19 ​ The full extent to which the novel coronavirus disease ("COVID-19") pandemic 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, will depend on future developments that are highly uncertain at this time.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 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). ​ ​ Note 3. Fair Value Measurements (Continued) ​ 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 six months ended June 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 June 30, 2020 and December 31, 2019 categorized by the level of inputs used in the valuation of each asset and liability. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 27,560 ​ ​ 27,560 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 3,196 ​ — ​ 3,196 ​ — Total assets ​ $ 31,006 ​ $ 27,810 ​ $ 3,196 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,053 ​ $ — ​ $ — ​ $ 3,053 Future tranche right liability ​ ​ 41,074 ​ ​ — ​ ​ — ​ ​ 41,074 Total liabilities ​ $ 44,127 ​ $ — ​ $ — ​ $ 44,127 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 ​ 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 (188) ​ (5,362) Balance, June 30, 2020 $ 3,053 ​ $ 41,074 ​ ​ Note 3. Fair Value Measurements (Continued) ​ 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: ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.42% ​ ​ 1.79% Expected dividend yield ​ — ​ ​ — Expected term (years) ​ 6.48 ​ ​ 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 binomial lattice model to value the Series B2 (tranche 2) and B3 (tranche 3) tranches and a Monte Carlo simulation to value the Series B4 (tranche 4) 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, redemption and early exercise assumptions, cancellation and conversion assumptions, and the potential for future adjustment of the conversion price due to a future dilutive financing. ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.49% - 0.55% ​ ​ 1.84% - 1.88% Expected dividend yield ​ — ​ ​ — Expected term (years) of call option on preferred stock ​ 0.66 - 1.62 ​ ​ 1.16 - 2.16 Expected term (years) of warrants ​ 7.66 - 8.62 ​ ​ 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	6 Months Ended
	Jun. 30, 2020
Investments
Investments	Note 4. Investments ​ The Company’s available-for-sale investments at fair value consisted of the following as of June 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Gross Gross Estimated ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Cost ​ (Losses) ​ Gains ​ Value Short-term investments – commercial paper ​ $ 3,196 ​ $ — ​ $ — ​ $ 3,196 Total short-term investments ​ $ 3,196 ​ $ — ​ $ — ​ $ 3,196 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 six months ended June 30, 2020 and December 31, 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 June 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 periods ended June 30, 2020 and December 31, 2019.

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2020
Property and Equipment
Property and Equipment	Note 5. Property and Equipment ​ At June 30, 2020 and December 31, 2019, property and equipment, net, consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 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 ​ 814 ​ 774 Property and equipment, net ​ $ 63 ​ $ 97 ​ Depreciation and amortization expense on property and equipment was less than $0.1 million for each of the three and six months ended June 30, 2020 and 2019. Additionally, there were

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2020
Accrued Expenses
Accrued Expenses	Note 6. Accrued Expenses ​ At June 30, 2020 and December 31, 2019, accrued expenses consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (In thousands) ​ 2020 2019 Payroll and related costs ​ $ 1,796 ​ $ 2,179 Clinical and nonclinical trial expenses ​ 4,405 ​ 4,199 Professional and consulting fees ​ 692 ​ 859 Restructuring expenses ​ 16 ​ 113 Other ​ 114 ​ 111 Total accrued expenses ​ $ 7,023 ​ $ 7,461 ​

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	6 Months Ended
	Jun. 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 June 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. In the event the Company did not receive the required shareholder approval to increase the Company’s authorized shares of common stock in an amount sufficient to cover the conversion of all potential convertible securities issuable under the December 2019 Securities Purchase Agreement on or prior to December 31, 2020, the Option Fee was refundable to the Purchasers. At the Company’s 2020 Annual Meeting of Stockholders held on May 12, 2020, 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 common stock, par value $0.001 per share, to 140,000,000 (the “Charter Amendment”), representing an amount sufficient to cover the conversion of all potential future convertible securities. As a result of stockholder approval of the Charter Amendment, the Company is not required to return the Option Fee. Note 7. Redeemable Convertible Preferred Stock (Continued) ​ 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. ​ 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 June 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 six months ended June 30, 2020, accretion was de minimis.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 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, an existing stockholder and 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. ​ Note 8. Stockholders’ Equity (Continued) ​ Through June 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 all securities issued in connection with the April 2020 Securities Purchase Agreement, including the option provided to Pillar Partners’ to participate in the April 2020 Private Placement Second Closing as further described below, were determined to be freestanding equity-classified instruments. ​ 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 June 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. ​ Common Stock Purchase Agreement ​ On March 4, 2019, the Company entered into a Purchase Agreement with Lincoln Park Capital Fund, LLC (“Lincoln Park”), 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 (the “LPC Purchase Agreement”). As consideration for entering into the LPC Purchase Agreement, 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 six months ended June 30, 2020 and 2019, the Company sold 600,000 and 785,848 shares pursuant to the LPC Purchase Agreement, resulting in net proceeds of $1.1 million and $2.3 million, respectively. As of June 30, 2020, the Company may sell up to an additional $30.2 million of shares under the LPC Agreement, subject to certain limitations. ​ "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 six months ended June 30, 2020 and 2019, the Company sold 821,018 and 532,700 Shares, respectively, pursuant to the ATM Agreement, resulting in net proceeds, after deduction of commissions and other offering expenses, of $1.4 million and $1.6 million, respectively. As of June 30, 2020, the Company may sell up to an additional $46.8 million of shares under the ATM Agreement. ​ Note 8. Stockholders’ Equity (Continued) ​ 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 June 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ June 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 ​ ​ 5,770,030 ​ 2,730,516 ​ ​ ​ ​ ​ Total outstanding 8,138,430 ​ 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	6 Months Ended
	Jun. 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. ​ ​ Note 9. Collaboration and License Agreements (Continued) ​ The Company accounts for the Licensee Agreement in accordance with ASC Topic 606. As of June 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

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Stock-Based Compensation
Stock-Based Compensation	Note 10. Stock-Based Compensation ​ As of June 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, 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 June 30, 2020, options to purchase a total of 4,035,439 shares of common stock and 376,210 restricted stock units were outstanding and up to 1,464,378 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 June 30, 2020, options to purchase a total of 327,262 shares of common stock were outstanding under the 2008 Plan. In addition, as of June 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. ​ ​ Note 10. Stock-Based Compensation (Continued) ​ 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 June 30, 2020, 281,317 shares remained available for issuance under the 2017 ESPP. ​ For the six months ended June 30, 2020 and 2019, the Company issued 40,024 and 30,570 shares of common stock, respectively, under the 2017 ESPP and received proceeds of less than $0.1 million during each period, as a result of employee stock purchases. ​ Accounting for Stock-based Compensation ​ The Company recognizes non-cash compensation expense for stock-based awards under the Company’s equity incentive plans over an award’s requisite service period, or vesting period, using the straight-line attribution method, based on their grant date fair value determined using the Black-Scholes option-pricing model. The Company also recognizes non-cash compensation for stock purchases made under the 2017 ESPP. The fair value of the discounted purchases made under the Company’s 2017 ESPP is calculated using the Black-Scholes option-pricing model. The fair value of the look-back provision plus the 15% discount is recognized as compensation expense over each plan period. ​ Total stock-based compensation expense attributable to stock-based payments 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 six months ended June 30, 2020 and 2019 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ June 30, ​ June 30, (in thousands) ​ 2020 2019 ​ 2020 2019 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plans ​ $ 15 $ 12 ​ $ 26 $ 18 Equity Incentive Plans ​ ​ 192 ​ 320 ​ ​ 385 ​ 650 ​ ​ $ 207 $ 332 ​ $ 411 $ 668 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plans ​ $ 1 $ 8 ​ $ 2 $ 14 Equity Incentive Plans ​ ​ 546 ​ 549 ​ ​ 1,091 ​ 1,223 ​ ​ $ 547 $ 557 ​ $ 1,093 $ 1,237 Total stock-based compensation expense ​ $ 754 $ 889 ​ $ 1,504 $ 1,905 ​ During the six months ended June 30, 2020 and 2019, the weighted average fair market value of stock options granted was $1.09 and $1.83, respectively. ​ ​ Note 10. Stock-Based Compensation (Continued) ​ The following weighted average assumptions apply to the options to purchase 727,129 and 610,002 shares of common stock granted to employees and directors during the six months ended June 30, 2020 and 2019, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2020 2019 Average risk-free interest rate ​ 1.5% ​ ​ 2.3% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 4.0 Expected volatility ​ 82.5% ​ ​ 82.8% Weighted average exercise price (per share) ​ $ 1.82 ​ $ 3.02 ​ All options granted during the six months ended June 30, 2020 and 2019 were granted at exercise prices equal to the fair market value of the common stock on the dates of grant . ​ Stock Option Activity ​ The following table summarizes stock option activity for the six months ended June 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 727,129 ​ ​ 1.82 ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ Forfeited (38,874) ​ ​ 5.67 ​ ​ ​ ​ ​ Expired (152,221) ​ ​ 19.83 ​ ​ ​ ​ ​ Outstanding at June 30, 2020 (1) 4,756,451 ​ $ 11.20 ​ 6.8 ​ $ — Exercisable at June 30, 2020 2,541,439 ​ $ 17.18 ​ 5.0 ​ $ — (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 six months ended June 30, 2020 was $1.5 million. As of June 30, 2020, there was $4.5 million of unrecognized compensation cost related to unvested options, which the Company expects to recognize over a weighted average period of 2. 3 years. ​ Restricted Stock Activity ​ The following table summarizes restricted stock activity for the six months ended June 30, 2020: ​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average Grant Date Fair Value Nonvested shares at December 31, 2019 193,625 ​ $ 3.14 Granted 237,675 ​ 1.79 Cancelled (6,688) ​ 2.34 Vested (48,402) ​ 3.14 Nonvested shares at June 30, 2020 376,210 ​ $ 2.30 ​ As of June 30, 2020, there was $0.7 million of unrecognized compensation expense related to the restricted stock units, which is expected to be recognized over a weighted-average period of 3. 0 years.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 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 June 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% of the Company's outstanding common stock. ​ As of June 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 Pharmaceuticals 6 L.P. (“Pillar 6”), and Pillar Partners Foundation, L.P. (“Pillar Partners”) (collectively, “Pillar”). As of June 30, 2020, Pillar owned approximately 18% of the Company's common stock. ​ In April 2020, the Company sold shares of common stock and common stock warrants to Pillar Partners in a private placement transaction as more fully described in Note 8. As of June 30, 2020, Pillar held warrants to purchase up to 3,039,514 shares of the Company’s common stock at an exercise price of $2.28 and an option to purchase Company securities in the April 2020 Private Placement Second Closing, provided for in the April 2020 Securities Purchase Agreement, as more fully described in Note 8. ​ Subsequent to June 30, 2020, in July 2020, the Company sold shares of its common stock, pre-funded warrants and warrants to purchase shares of the Company’s common stock to Pillar Partners in a private placement transaction, as more fully described in Note 13. Immediately following the private placement transaction, Pillar owned approximately 19.99% of the Company’s common stock. ​ Board Fees Paid in Stock ​ Pursuant to the Company’s director compensation program, in lieu of director board and committee fees of $0.1 million during each of the six months ended June 30, 2020 and 2019, the Company issued 96,551 and 26,331 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	6 Months Ended
	Jun. 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. ​ Details in the computation of basic and diluted net loss per common share were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ($ in thousands except per share data) ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Net loss per share — Basic: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (24,226) ​ $ (11,176) ​ $ (15,409) ​ $ (22,150) Denominator for basic net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 31,941 ​ ​ 28,070 Basic net loss per common share ​ $ (0.72) ​ $ (0.39) ​ $ (0.48) ​ $ (0.79) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share — Diluted: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (24,226) ​ $ (11,176) ​ $ (15,409) ​ $ (22,150) Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights ​ ​ — ​ ​ — ​ ​ (2,284) ​ ​ — Numerator for diluted net loss per share ​ $ (24,226) ​ $ (11,176) ​ $ (17,693) ​ $ (22,150) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 31,941 ​ ​ 28,070 Plus: Incremental shares underlying “in the money” liability-classified future tranche rights outstanding ​ ​ — ​ ​ — ​ ​ 2,182 ​ ​ — Denominator for diluted net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 34,123 ​ ​ 28,070 Diluted net loss per common share ​ $ (0.72) ​ $ (0.39) ​ $ (0.52) ​ $ (0.79) ​ 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 six months ended June 30, 2020 and 2019. Total antidilutive securities excluded from the calculation of diluted net loss per share for the respected periods were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (in thousands) ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Stock options ​ ​ 4,756 ​ ​ 3,844 ​ ​ 4,756 ​ ​ 3,844 Restricted stock units ​ ​ 376 ​ ​ 194 ​ ​ 376 ​ ​ 194 Common stock warrants ​ ​ 8,138 ​ ​ 2,769 ​ ​ 8,138 ​ ​ 2,769 Convertible preferred stock ​ ​ 2,369 ​ ​ — ​ ​ 2,369 ​ ​ — Future tranche rights ​ ​ 53,528 ​ ​ — ​ ​ 33,791 ​ ​ — Total ​ ​ 69,167 ​ ​ 6,807 ​ ​ 49,430 ​ ​ 6,807 ​

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 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. ​ 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, an existing stockholder and 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 Pillar Partners 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 Pillar Partners, at its 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 will occur on or before the tenth Business Day following the ORR Data Announcement (as defined in the Securities Purchase Agreement) and will be held on or before the fifth day following delivery of written notice by Pillar Partners to the Company. Subject to certain beneficial ownership limitation, the pre-funded warrants will be immediately exercisable upon issuance and do not have an expiration date. ​ The common warrants are exercisable at any time or times upon issuance, provided that Pillar Partners will be prohibited, subject to certain exceptions, from exercising to the extent that immediately prior to or after giving effect to such exercise, Pillar Partners, together with their affiliates and other attribution parties, would own more than 19.99% of the total number of shares of the Company’s common stock then issued and outstanding, which percentage may be changed at the holder’s election to a lower percentage at any time or to a higher percentage not to exceed 19.99% upon 61 days ’ notice to the Company. The common warrants will expire three years from the date of issuance. ​ Concurrent with the execution of the July 2020 Securities Purchase Agreement, the Company entered into a registration rights agreement (the “July 2020 Registration Rights Agreement”) with Pillar Partners, pursuant to which the Company agreed, following demand by Pillar Partners, to file a registration statement on Form S-3 covering the resale of all of the registrable securities as promptly as reasonably practicable following such demand, and in any event within 60 days of such demand. ​ The foregoing descriptions of the July 2020 Securities Purchase Agreement, July 2020 Registration Rights Agreement, and the warrants are qualified in their entirety by reference to Exhibits 4.1, 4.2,4.4, and 10.1 of this Form 10-Q, which exhibits are incorporated herein by reference.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 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 six months ended June 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 June 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 June 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 June 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, 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 June 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 Asset and Lease Liability ​ The Company accounts for leases under ASC Topic 842, Leases Property, Plant, and Equipment ​ As of June 30, 2020 and December 31, 2019, the Company’s operating lease ROU asset and corresponding short-term and long-term lease liabilities relate to its existing Exton, PA facility operating lease which expires on May 31, 2025 as a result of the Company’s election to exercise its five-year renewal option in January 2020. ​
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 June 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 as the Future Tranche Rights and related Option Fee, each defined in Note 7, were subject to the Company obtaining required shareholder approval and filing the Charter Amendment, as defined in Note 3.
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
COVID-19	COVID-19 ​ The full extent to which the novel coronavirus disease ("COVID-19") pandemic 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, will depend on future developments that are highly uncertain at this time.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Schedule of assets and liabilities measured and recorded in financial statements at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 (In thousands) ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 250 ​ $ 250 ​ $ — ​ $ — Cash equivalents – money market funds ​ ​ 27,560 ​ ​ 27,560 ​ ​ — ​ ​ — Short-term investments – commercial paper ​ 3,196 ​ — ​ 3,196 ​ — Total assets ​ $ 31,006 ​ $ 27,810 ​ $ 3,196 ​ $ — Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Warrant liability ​ $ 3,053 ​ $ — ​ $ — ​ $ 3,053 Future tranche right liability ​ ​ 41,074 ​ ​ — ​ ​ — ​ ​ 41,074 Total liabilities ​ $ 44,127 ​ $ — ​ $ — ​ $ 44,127 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 (188) ​ (5,362) Balance, June 30, 2020 $ 3,053 ​ $ 41,074
Warrant liability
Schedule of assumptions used in determining fair value	​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.42% ​ ​ 1.79% Expected dividend yield ​ — ​ ​ — Expected term (years) ​ 6.48 ​ ​ 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	​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2020 ​ 2019 Risk-free interest rate ​ 0.49% - 0.55% ​ ​ 1.84% - 1.88% Expected dividend yield ​ — ​ ​ — Expected term (years) of call option on preferred stock ​ 0.66 - 1.62 ​ ​ 1.16 - 2.16 Expected term (years) of warrants ​ 7.66 - 8.62 ​ ​ 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)	6 Months Ended
	Jun. 30, 2020
Investments
Schedule of available-for-sale investments at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2020 ​ ​ Gross Gross Estimated ​ ​ ​ ​ Unrealized ​ Unrealized ​ Fair (In thousands) ​ Cost ​ (Losses) ​ Gains ​ Value Short-term investments – commercial paper ​ $ 3,196 ​ $ — ​ $ — ​ $ 3,196 Total short-term investments ​ $ 3,196 ​ $ — ​ $ — ​ $ 3,196 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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)	6 Months Ended
	Jun. 30, 2020
Property and Equipment
Schedule of net property and equipment at cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 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 ​ 814 ​ 774 Property and equipment, net ​ $ 63 ​ $ 97 ​

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2020
Accrued Expenses
Schedule of accrued expenses	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (In thousands) ​ 2020 2019 Payroll and related costs ​ $ 1,796 ​ $ 2,179 Clinical and nonclinical trial expenses ​ 4,405 ​ 4,199 Professional and consulting fees ​ 692 ​ 859 Restructuring expenses ​ 16 ​ 113 Other ​ 114 ​ 111 Total accrued expenses ​ $ 7,023 ​ $ 7,461

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 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)	6 Months Ended
	Jun. 30, 2020
Stockholders' Equity
Schedule of warrants outstanding and exercisable for purchase of common stock	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ ​ ​ ​ ​ ​ June 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 ​ ​ 5,770,030 ​ 2,730,516 ​ ​ ​ ​ ​ Total outstanding 8,138,430 ​ 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)	6 Months Ended
	Jun. 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 ​ Six Months Ended ​ June 30, ​ June 30, (in thousands) ​ 2020 2019 ​ 2020 2019 Stock-based compensation: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plans ​ $ 15 $ 12 ​ $ 26 $ 18 Equity Incentive Plans ​ ​ 192 ​ 320 ​ ​ 385 ​ 650 ​ ​ $ 207 $ 332 ​ $ 411 $ 668 General and administrative ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee Stock Purchase Plans ​ $ 1 $ 8 ​ $ 2 $ 14 Equity Incentive Plans ​ ​ 546 ​ 549 ​ ​ 1,091 ​ 1,223 ​ ​ $ 547 $ 557 ​ $ 1,093 $ 1,237 Total stock-based compensation expense ​ $ 754 $ 889 ​ $ 1,504 $ 1,905
Schedule of weighted average assumptions applied to options	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ 2020 2019 Average risk-free interest rate ​ 1.5% ​ ​ 2.3% Expected dividend yield ​ — ​ ​ — Expected lives (years) ​ 3.9 ​ ​ 4.0 Expected volatility ​ 82.5% ​ ​ 82.8% Weighted average exercise price (per share) ​ $ 1.82 ​ $ 3.02
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 727,129 ​ ​ 1.82 ​ ​ ​ ​ ​ Exercised — ​ ​ — ​ ​ ​ ​ ​ Forfeited (38,874) ​ ​ 5.67 ​ ​ ​ ​ ​ Expired (152,221) ​ ​ 19.83 ​ ​ ​ ​ ​ Outstanding at June 30, 2020 (1) 4,756,451 ​ $ 11.20 ​ 6.8 ​ $ — Exercisable at June 30, 2020 2,541,439 ​ $ 17.18 ​ 5.0 ​ $ — (1) Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition.
Schedule of summary of restricted stock activity	​ ​ ​ ​ ​ ​ ($ in thousands, except per share data) ​ Number of Shares ​ Weighted-Average Grant Date Fair Value Nonvested shares at December 31, 2019 193,625 ​ $ 3.14 Granted 237,675 ​ 1.79 Cancelled (6,688) ​ 2.34 Vested (48,402) ​ 3.14 Nonvested shares at June 30, 2020 376,210 ​ $ 2.30

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	6 Months Ended
	Jun. 30, 2020
Net Loss per Common Share
Computation of basic and diluted net income (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ($ in thousands except per share data) ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Net loss per share — Basic: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (24,226) ​ $ (11,176) ​ $ (15,409) ​ $ (22,150) Denominator for basic net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 31,941 ​ ​ 28,070 Basic net loss per common share ​ $ (0.72) ​ $ (0.39) ​ $ (0.48) ​ $ (0.79) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share — Diluted: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (24,226) ​ $ (11,176) ​ $ (15,409) ​ $ (22,150) Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights ​ ​ — ​ ​ — ​ ​ (2,284) ​ ​ — Numerator for diluted net loss per share ​ $ (24,226) ​ $ (11,176) ​ $ (17,693) ​ $ (22,150) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Denominator for basic net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 31,941 ​ ​ 28,070 Plus: Incremental shares underlying “in the money” liability-classified future tranche rights outstanding ​ ​ — ​ ​ — ​ ​ 2,182 ​ ​ — Denominator for diluted net loss per share ​ ​ 33,583 ​ ​ 28,461 ​ ​ 34,123 ​ ​ 28,070 Diluted net loss per common share ​ $ (0.72) ​ $ (0.39) ​ $ (0.52) ​ $ (0.79)
Schedule of potentially dilutive securities excluded from diluted net income (loss) per common share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, (in thousands) ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Stock options ​ ​ 4,756 ​ ​ 3,844 ​ ​ 4,756 ​ ​ 3,844 Restricted stock units ​ ​ 376 ​ ​ 194 ​ ​ 376 ​ ​ 194 Common stock warrants ​ ​ 8,138 ​ ​ 2,769 ​ ​ 8,138 ​ ​ 2,769 Convertible preferred stock ​ ​ 2,369 ​ ​ — ​ ​ 2,369 ​ ​ — Future tranche rights ​ ​ 53,528 ​ ​ — ​ ​ 33,791 ​ ​ — Total ​ ​ 69,167 ​ ​ 6,807 ​ ​ 49,430 ​ ​ 6,807

Business and Organization (Deta

Business and Organization (Details) - USD ($) $ in Thousands	1 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Business and Organization
Accumulated deficit	$ 736,299	$ 720,890
Cash, cash equivalents and investments	31,000
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5,100

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Institution	Jun. 30, 2019USD ($)	Jan. 31, 2020	Dec. 31, 2019USD ($)
Summary of Significant Accounting Policies
Number of financial institutions | Institution			2
Tax expense (benefit)	$ 0	$ 0	$ 0	$ 0
Uncertain tax positions	$ 0		$ 0			$ 0
Operating lease renewal term					5 years

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) $ in Thousands	6 Months Ended
	Jun. 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	Jun. 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	$ 3,196	$ 2,774
Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	31,006	42,793
Total Liabilities	44,127	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	3,053	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	41,074	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	27,560	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	3,196	2,774
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	27,810	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	27,560	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	3,196	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	3,196	2,774
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	44,127	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	3,053	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	$ 41,074	$ 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	6 Months Ended
	Jun. 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	(188)
Ending balance	3,053
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	(5,362)
Ending balance	$ 41,074

Fair Value Measurements - Weigh

Fair Value Measurements - Weighted-average assumptions (Details)	Jun. 30, 2020$ / sharesUSD ($)	Dec. 31, 2019USD ($)$ / shares
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.42	1.79
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input | $	6.48	6.98
Expected volatility
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

Fair Value Measurements - Futur

Fair Value Measurements - Future Tranche Rights (Details)	Jun. 30, 2020$ / sharesUSD ($)	Dec. 31, 2019$ / sharesUSD ($)
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.42	1.79
Risk-free interest rate | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.49	1.84
Risk-free interest rate | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.55	1.88
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input | $	6.48	6.98
Expected term | Warrants | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	7.66	8.16
Expected term | Warrants | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	8.62	9.16
Expected term | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.66	1.16
Expected term | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.62	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	Jun. 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	$ 0.001

Investments - Summary of Availa

Investments - Summary of Available-for-Sale Investments at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Short-term investments
Schedule of Available-for-sale Securities
Cost	$ 3,196	$ 2,774
Estimated Fair Value	3,196	2,774
Short-term investments - commercial paper
Schedule of Available-for-sale Securities
Cost	3,196	2,774
Estimated Fair Value	$ 3,196	$ 2,774

Investments - Additional Inform

Investments - Additional Information (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	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	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment
Total property and equipment, at cost	$ 877	$ 871
Less: Accumulated depreciation and amortization	814	774
Property and equipment, net	63	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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Non-cash property additions			$ 0	$ 0
Maximum
Depreciation and amortization expense on property and equipment	$ 100	$ 100	$ 100	$ 100

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Expenses
Payroll and related costs	$ 1,796	$ 2,179
Clinical and nonclinical trial expenses	4,405	4,199
Professional and consulting fees	692	859
Restructuring expenses	16	113
Other	114	111
Total accrued expenses	$ 7,023	$ 7,461

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock (Details) - USD ($)	Dec. 23, 2019	Jun. 30, 2020
Temporary Equity
Aggregate gross proceeds	$ 3,900,000
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 Millions	Apr. 07, 2020	Dec. 23, 2019	Mar. 04, 2019	Jun. 30, 2020	Nov. 30, 2018	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	May 12, 2020	Dec. 31, 2019
Class of Stock
Par value (per share)				$ 0.001		$ 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		$ 3.9
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any				$ 5.1
"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				46.8		$ 46.8	$ 46.8
Stock issued (in shares)							821,018	532,700
Net proceeds from offering of common stock							$ 1.4	$ 1.6
Percentage of fixed commission expense of gross proceeds of shares sold in ATM agreement					3.00%
Lincoln Park Capital Fund, LLC ("Investor")
Class of Stock
Value of shares investor has committed to purchase from time to time at Company's sole discretion			$ 35	$ 30.2		$ 30.2	$ 30.2
Stock issued (in shares)			269,749				600,000	785,848
Stock issued (per share)			$ 2.84
Net proceeds from offering of common stock							$ 1.1	$ 2.3
Common Stock | "At-The-Market" Equity Program
Class of Stock
Net proceeds from offering of common stock					$ 50
Future plans | Pillar Investment Entities
Class of Stock
Ownership percentage	19.99%
Pillar Investment Entities
Class of Stock
Stock issued (in shares)	3,039,514
Ownership percentage				19.99%		19.99%	19.99%
Shares of common stock that may be purchased upon exercise of warrants	3,039,514			3,039,514		3,039,514	3,039,514
Warrant exercise price (per share)	$ 2.28			$ 2.28		$ 2.28	$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5
Combined purchase price (per share)	$ 1.645
Stock price underlying warrants (per share)	$ 0.125
Net proceeds from offering of common stock						$ 4.7
Pillar Investment Entities | Future plans
Class of Stock
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
Number of common warrants	0.5
Stock price (in dollars per share)	$ 3.01
Number of consecutive trading days	20 days
Pillar Investment Entities | Future plans | Common stock warrants
Class of Stock
Combined purchase price (per share)	$ 1.82
Pillar Investment Entities | Future plans | Pre-funded Warrants
Class of Stock
Warrant exercise price (per share)	0.01
Combined purchase price (per share)	$ 1.81

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Class of Warrant or Right
Number of Warrants	8,138,430	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	5,770,030	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	$ 0.08
April 2020 Warrants
Class of Warrant or Right
Number of Warrants	3,039,514
Warrant exercise price per share	$ 2.28

Collaboration and License Agr_2

Collaboration and License Agreements (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Alliance revenue			$ 1,448,000		$ 1,448,000
Operating expenses		$ 8,011,000	$ 12,964,000	$ 21,163,000	$ 24,340,000
Option and License Agreement with Licensee
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Performance obligation		0		$ 0
Percentage of shares acquired				10.00%
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	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2019
Class of Stock
Common stock options outstanding		4,756,451	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		1,464,378
Maximum number of additional common shares	868,372
Common stock options outstanding		4,035,439
Restricted stock units outstanding		376,210

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plans (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 07, 2017
Class of Stock
Proceeds from employee stock purchases	$ 54	$ 68
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			281,317
Employee Stock Purchase Plans
Class of Stock
Common stock share issued	40,024	30,570

Stock-Based Compensation - Acco

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 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)			$ 1.09	$ 1.83
Stock-based compensation	$ 754	$ 889	$ 1,504	$ 1,905
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	207	332	411	668
Research and development | Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	15	12	26	18
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	192	320	385	650
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	547	557	1,093	1,237
General and administrative | Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	1	8	2	14
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 546	$ 549	$ 1,091	$ 1,223

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used in Determining Fair Value of Stock Options (Details) - $ / shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Summary of Significant Accounting Policies
Options to purchase common stock granted to employees and directors	727,129	610,002
Average risk free interest rate	1.50%	2.30%
Dividend rate	0.00%	0.00%
Expected lives (years)	3 years 10 months 24 days	4 years
Expected volatility	82.50%	82.80%
Weighted average exercise price of options granted during the period (per share)	$ 1.82	$ 3.02

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Options, Outstanding, Beginning Balance	4,220,417
Granted	727,129
Forfeited	(38,874)
Expired	(152,221)
Options, Outstanding, Ending Balance	4,756,451		4,220,417
Exercisable, Ending Balance	2,541,439
Weighted Average Exercise Price, Beginning Balance	$ 13.08
Granted, Weighted Average Exercise Price	1.82	$ 3.02
Forfeited, Weighted Average Exercise Price	5.67
Expired, Weighted Average Exercise Price	19.83
Weighted Average Exercise Price, Ending Balance	11.20		$ 13.08
Exercisable, Weighted Average Exercise Price	$ 17.18
Outstanding, Ending balance, Weighted Average Remaining Contractual Term	6 years 9 months 18 days		6 years 7 months 6 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term	5 years
Fair value of options, vested	$ 1.5
Unrecognized compensation cost related to nonvested stock-based compensation	$ 4.5
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 3 months 18 days
Restricted stock units
Unrecognized compensation cost related to nonvested stock-based compensation	$ 0.7
Weighted average remaining period over which unrecognized compensation expense will be recognized	3 years

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Activity (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Unrecognized compensation expense | $	$ 4.5
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 3 months 18 days
Restricted stock units
Restricted Stock Activity, Number of Shares
Nonvested shares, Beginning Balance | shares	193,625
Granted | shares	237,675
Cancelled | shares	(6,688)
Vested | shares	(48,402)
Nonvested shares, Ending Balance | shares	376,210
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Nonvested shares, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 3.14
Granted, Weighted-Average Grant Date Fair Value | $ / shares	1.79
Cancelled, Weighted-Average Grant Date Fair Value | $ / shares	2.34
Vested, Weighted-Average Grant Date Fair Value | $ / shares	3.14
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 2.30
Unrecognized compensation expense | $	$ 0.7
Weighted average remaining period over which unrecognized compensation expense will be recognized	3 years

Related Party Transactions - Ov

Related Party Transactions - Overview of Related Parties (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Apr. 07, 2020	Dec. 31, 2019
Related Party Transactions
Number of Warrants	8,138,430			5,098,916
Proceeds from issuance of common stock in lieu of director board and committee fees	$ 0.1	$ 0.1
Common stock issued in lieu of board fees	96,551	26,331
Baker Bros. Advisors LP
Related Party Transactions
Ownership percentage	13.00%
Aggregate common shares	4,608,786
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 | Board of Director
Related Party Transactions
Ownership percentage	18.00%
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
Pillar Investment Entities
Related Party Transactions
Ownership percentage	19.99%
Exercise price of warrants	$ 2.28		$ 2.28
Number of Shares	3,039,514		3,039,514

Net Loss per Common Share (Deta

Net Loss per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Net loss per share - Basic:
Net loss	$ (24,226)	$ 8,817	$ (11,176)	$ (10,974)	$ (15,409)	$ (22,150)
Denominator for basic net loss per share	33,583		28,461		31,941	28,070
Basic net loss per common share	$ (0.72)		$ (0.39)		$ (0.48)	$ (0.79)
Net loss per share - Diluted:
Net loss	$ (24,226)	$ 8,817	$ (11,176)	$ (10,974)	$ (15,409)	$ (22,150)
Less: Future tranche right revaluation gain applicable to dilutive liability-classified future tranche rights					(2,284)
Numerator for diluted net loss per share	$ (24,226)		$ (11,176)		$ (17,693)	$ (22,150)
Denominator for basic net loss per share	33,583		28,461		31,941	28,070
Plus: Incremental shares underlying "in the money" liability-classified future tranche rights outstanding					2,182
Denominator for diluted net loss per share	33,583		28,461		34,123	28,070
Diluted net loss per common share	$ (0.72)		$ (0.39)		$ (0.52)	$ (0.79)

Net Loss per Common Share - Ant

Net Loss per Common Share - Antidilutive securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive securities
Total antidilutive securities	69,167	6,807	49,430	6,807
Stock options
Antidilutive securities
Total antidilutive securities	4,756	3,844	4,756	3,844
Restricted stock units
Antidilutive securities
Total antidilutive securities	376	194	376	194
Common stock warrants
Antidilutive securities
Total antidilutive securities	8,138	2,769	8,138	2,769
Convertible preferred stock
Antidilutive securities
Total antidilutive securities	2,369		2,369
Future tranche right liability
Antidilutive securities
Total antidilutive securities	53,528		33,791

Subsequent Events - Proceeds fr

Subsequent Events - Proceeds from Sale of Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 13, 2020	Apr. 07, 2020	Jun. 30, 2020
Subsequent Events
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any			$ 5.1
Future plans | Pillar Investment Entities
Subsequent Events
Ownership percentage		19.99%
Pillar Investment Entities
Subsequent Events
Stock issued (in shares)		3,039,514
Shares of common stock that may be purchased upon exercise of warrants		3,039,514	3,039,514
Warrant exercise price (per share)		$ 2.28	$ 2.28
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any		$ 5
Combined purchase price (per share)		$ 1.645
Stock price underlying warrants (per share)		$ 0.125
Ownership percentage			19.99%
Pillar Investment Entities | Future plans
Subsequent Events
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
Number of common warrants		0.5
Stock price (in dollars per share)		$ 3.01
Number of consecutive trading days		20 days
Pillar Investment Entities | Future plans | Common stock warrants
Subsequent Events
Combined purchase price (per share)		$ 1.82
Pillar Investment Entities | Future plans | Pre-funded Warrants
Subsequent Events
Warrant exercise price (per share)		0.01
Combined purchase price (per share)		$ 1.81
Subsequent Events | Future plans | Pillar Investment Entities
Subsequent Events
Ownership percentage	19.99%
Subsequent Events | Pillar Investment Entities
Subsequent Events
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1
Combined purchase price (per share)	$ 1.845
Stock price underlying warrants (per share)	$ 0.125
Ownership percentage	19.99%
Subsequent Events | Pillar Investment Entities | Common stock warrants
Subsequent Events
Shares of common stock that may be purchased upon exercise of warrants	2,764,227
Warrant exercise price (per share)	$ 2.58
Number of days of notice for changes to holding percentage	61 days
Term of warrants	3 years
Subsequent Events | Pillar Investment Entities | Pre-funded Warrants
Subsequent Events
Stock issued (in shares)	749,993
Shares of common stock that may be purchased upon exercise of warrants	2,014,234
Warrant exercise price (per share)	$ 0.01
Subsequent Events | Pillar Investment Entities | Future plans
Subsequent Events
Gross proceeds from sale of common stock and warrants excluding the proceeds from exercise of the warrants, if any	$ 5.1
Number of common warrants	0.35
Stock price (in dollars per share)	$ 6.50
Subsequent Events | Pillar Investment Entities | Future plans | Common stock warrants
Subsequent Events
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
Subsequent Events | Pillar Investment Entities | Future plans | Pre-funded Warrants
Subsequent Events
Stock issued (in shares)	784,615
Warrant exercise price (per share)	$ 0.01
Stock price (in dollars per share)	$ 6.45625