Aceragen (ACGN) 10-K 11 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 15, 2020	Jun. 28, 2019
Document and Entity Information
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Entity Registrant Name	IDERA PHARMACEUTICALS, INC.
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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		30,538,478
Entity Public Float			$ 63.6
Entity Central Index Key	0000861838
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 40,019	$ 71,431
Short-term investments	2,774
Prepaid expenses and other current assets	3,475	1,376
Total current assets	46,268	72,807
Property and equipment, net	97	207
Operating lease right-of-use asset	1,054
Other assets	70	9
Total assets	47,489	73,023
Current liabilities:
Accounts payable	457	1,134
Accrued expenses	7,461	7,884
Operating lease liability	163
Future tranche right liability	46,436
Total current liabilities	54,517	9,018
Warrant liability, long-term	3,241
Operating lease liability, net of current portion	899
Other liabilities		11
Total liabilities	58,657	9,029
Commitments and contingencies (Note 13)
Stockholders’ equity (deficit)
Common stock, $0.001 par value, Authorized — 70,000 shares; Issued and outstanding — 29,672 and 27,188 at December 31, 2019 and December 31, 2018, respectively	30	27
Additional paid-in capital	709,692	728,342
Accumulated deficit	(720,890)	(664,375)
Total stockholders’ equity (deficit)	(11,168)	63,994
Total liabilities and stockholders’ equity (deficit)	47,489	73,023
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	Dec. 31, 2019	Dec. 31, 2018
Preferred stock, shares issued	500,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	70,000,000	70,000,000
Common stock, shares issued	29,672,000	27,188,000
Common stock, shares outstanding	29,672,000	27,188,000
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 (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares designated	277,921	278,000
Preferred stock, shares issued	24,000	0
Preferred stock, shares outstanding	24,000	0
Common stock, shares outstanding	23,684,000

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Alliance revenue	$ 1,448	$ 662	$ 902
Revenue, Product and Service [Extensible List]	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax	us_gaap:RevenueFromContractWithCustomerIncludingAssessedTax
Operating expenses:
Research and development	$ 34,853	$ 41,841	$ 50,653
General and administrative	12,481	15,420	15,588
Merger-related costs, net		1,245	1,128
Restructuring costs	181	3,112
Total operating expenses	47,515	61,618	67,369
Loss from operations	(46,067)	(60,956)	(66,467)
Other income (expense):
Interest income	1,150	1,089	574
Interest expense		(11)	(50)
Warrant revaluation expense	(598)
Future tranche right revaluation expense	(10,964)
Foreign currency exchange loss	(36)	(3)	(41)
Net loss	(56,515)	(59,881)	(65,984)
Deemed dividend related to December 2019 Private Placement (see Note 7)	(28,043)
Net loss attributable to common stockholders	$ (84,558)	$ (59,881)	$ (65,984)
Net loss per share applicable to common stockholders - basic and diluted (Note 17)	$ (2.96)	$ (2.25)	$ (3.35)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders - basic and diluted	28,545	26,601	19,675
Comprehensive loss:
Net loss	$ (56,515)	$ (59,881)	$ (65,984)
Unrealized gain on available-for-sale securities			17
Total other comprehensive income			17
Comprehensive loss	$ (56,515)	$ (59,881)	$ (65,967)

CONDENSED STATEMENTS OF REDEEMA

CONDENSED STATEMENTS OF REDEEMABLE PREFERRED STOCK AND STOCKHOLDER’S 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 (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively	Total
Beginning balance at Dec. 31, 2016	$ 18	$ 641,818	$ (538,470)	$ (17)		$ 103,349
Beginning balance (in shares) at Dec. 31, 2016	18,633
Cumulative effect from adoption of new accounting standard (Note 2)		40	(40)
Sale of common stock, net of issuance costs	$ 5	53,741				53,746
Sale of common stock, net of issuance costs (in shares)	4,792
Issuance of common stock under employee stock purchase plan		253				253
Issuance of common stock under employee stock purchase plan (in shares)	22
Issuance of common stock upon exercise of common stock options and warrants	$ 1	5,443				5,444
Issuance of common stock upon exercise of common stock options and warrants (in shares)	996
Issuance of common stock for services rendered		150				150
Issuance of common stock for services rendered (in shares)	10
Stock-based compensation expense		10,720				10,720
Unrealized gain on marketable securities				$ 17		17
Net loss			(65,984)			(65,984)
Ending balance at Dec. 31, 2017	$ 24	712,165	(604,494)			107,695
Ending balance (in shares) at Dec. 31, 2017	24,453
Issuance of common stock under employee stock purchase plan		243				243
Issuance of common stock under employee stock purchase plan (in shares)	25
Issuance of common stock upon exercise of common stock options and warrants	$ 3	10,163				10,166
Issuance of common stock upon exercise of common stock options and warrants (in shares)	2,702
Issuance of common stock for services rendered		97				97
Issuance of common stock for services rendered (in shares)	8
Stock-based compensation expense		5,674				5,674
Net loss			(59,881)			(59,881)
Ending balance at Dec. 31, 2018	$ 27	728,342	(664,375)			$ 63,994
Ending balance (in shares) at Dec. 31, 2018	27,188					27,188
Sale of common stock, net of issuance costs	$ 3	5,295				$ 5,298
Sale of common stock, net of issuance costs (in shares)	2,068
Sale of redeemable convertible preferred stock					23,684
Deemed dividend related to December 2019 Private Placement (Note 7)		(28,043)				(28,043)
Issuance of commitment shares (in shares)	270
Issuance of common stock under employee stock purchase plan		121				121
Issuance of common stock under employee stock purchase plan (in shares)	61
Issuance of common stock upon exercise of warrants		3				3
Issuance of common stock upon exercise of warrants (in shares)	38
Issuance of common stock for services rendered		129				129
Issuance of common stock for services rendered (in shares)	47
Stock-based compensation expense		3,845				3,845
Net loss			(56,515)			(56,515)
Ending balance at Dec. 31, 2019	$ 30	$ 709,692	$ (720,890)			$ (11,168)
Ending balance (in shares) at Dec. 31, 2019	29,672				23,684	29,672

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net loss	$ (56,515)	$ (59,881)	$ (65,984)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	3,845	5,674	10,720
Warrant liability revaluation expense	598
Future tranche right liability revaluation expense	10,964
Issuance of common stock for services rendered	129	97	150
Accretion of discounts and premiums on investments	(372)		94
Depreciation and amortization expense	120	432	746
(Gain) Loss on disposal or impairment of property and equipment	(10)	477
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,160)	2,717	(1,962)
Accounts payable, accrued expenses, and other liabilities	(1,105)	(866)	1,674
Deferred revenue		(566)	(697)
Other	8
Net cash used in operating activities	(44,498)	(51,916)	(55,259)
Cash Flows from Investing Activities:
Purchases of available-for-sale securities	(44,502)
Proceeds from maturity of available-for-sale securities	42,100		28,270
Proceeds from the sale of property and equipment	11	290
Purchases of property and equipment	(11)	(75)	(206)
Net cash (used in) provided by investing activities	(2,402)	215	28,064
Cash Flows from Financing Activities:
Proceeds from private placement	10,072
Proceeds from common stock financings, net	5,298		53,763
Proceeds from employee stock purchases	121	243	253
Proceeds from exercise of common stock options and warrants	3	10,166	5,444
Payments on note payable		(209)	(292)
Payments on capital leases	(6)
Payments on capital leases		(8)	(11)
Net cash provided by financing activities	15,488	10,192	59,157
Net (decrease) increase in cash, cash equivalents and restricted cash	(31,412)	(41,509)	31,962
Cash, cash equivalents and restricted cash, beginning of period	71,431	112,940	80,978
Cash, cash equivalents and restricted cash, end of period	40,019	71,431	112,940
Supplemental disclosure of cash flow information:
Cash paid for interest		9	42
Increase to right-of-use asset at adoption of ASC 842 and upon lease reassessment	1,236
Increase to lease liability at adoption of ASC 842 and upon lease reassessment	1,236
Supplemental disclosure of non-cash financing and investing activities:
Non-cash property additions			150
Accrued financing transaction costs	$ 165	$ 101	$ 17

Business and Organization

Business and Organization	12 Months Ended
	Dec. 31, 2019
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, or 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 December 31, 2019, the Company had an accumulated deficit of $720.9 million and a cash, cash equivalents and short-term investments balance of $42.8 million, which includes the $6.2 million contingently refundable option fee received in connection with the 2019 Private Placement, as more fully described in Note 7. 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 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 believes, based on management’s current operating plan, that its existing balance of cash, cash equivalents and short-term investments on hand as of December 31, 2019, excluding the $6.2 million contingently refundable Option Fee (Note 7) and including interest income and cash received through February 2020 from the ATM Agreement (Note 8) and the LPC Purchase Agreement (Note 8) , will be sufficient to fund operations into the first quarter of 2021. Management’s operating plan which underlies the analysis of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Actual results could vary from the operating plan. The Company follows the provisions of Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 205-40, Presentation of Financial Statements—Going Concern , which requires management to assess the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. The Company’s balance of cash, cash equivalents and short-term investments on hand as of December 31, 2019, excluding the $6.2 million contingently refundable option fee (Note 7), is not sufficient to fund operations for the one-year period after the date the financial statements are issued. As a result, there is substantial doubt about the Company’s ability to continue as a going concern through the one-year period from the date these financial statements are issued. Management’s plans that are intended to mitigate this risk include raising additional capital through the Company’s December 2019 Securities Purchase Agreement (Note 7), Common Stock Purchase Agreement (Note 8), “At-The-Market” Equity Program (Note 8), or additional financing or strategic transactions. Management’s plans may also include the possible deferral of certain operating expenses unless additional capital is received. The Company has and will continue to evaluate available alternatives to extend its operations beyond the one-year period after the date the financial statements are issued. Note 1. Business and Organization (Continued) Reverse Stock Split As further described in Note 8, on July 27, 2018, the Company effected a 1-for-8 reverse stock split of the Company's outstanding shares of common stock, as authorized at a special meeting. All share and per share amounts of common stock, preferred stock, options and warrants in the accompanying financial statements and notes thereto have been retroactively adjusted for all periods presented to reflect the reverse stock split.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, judgements, and assumptions that affect the reported amounts of assets, liabilities, equity, revenues and expenses, and related disclosure of contingencies in the accompanying financial statements and these notes. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable. Actual results could differ materially from those estimates. Segment Information Operating segments are defined as components of an enterprise in which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and assessing performance. The Company views its operations and manages its business as one operating segment, which is the business of developing novel therapeutics for oncology and rare diseases. 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 December 31, 2019 and 2018, 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 December 31, 2019 and 2018. As of December 31, 2019, the Company did not have any other derivatives, hedging instruments or other similar financial instruments. Concentration of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents and investments. The Company’s credit risk is managed by investing in highly rated money market instruments, certificates of deposit, corporate bonds, commercial paper and debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of December 31, 2019, all of the Company’s cash and cash equivalents were held at two financial institutions. 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 December 31, 2019 and 2018 consisted of cash and money market funds. Note 2. Summary of Significant Accounting Policies (Continued) Property and Equipment Property and equipment is carried at acquisition cost less accumulated depreciation, subject to review for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable as described further under the heading "Impairment of Long-Lived Assets" below. The cost of normal, recurring, or periodic repairs and maintenance activities related to property and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits. Depreciation and amortization are computed using the straight-line method based on the estimated useful lives of the related assets. Laboratory and other equipment are depreciated over three to five years. Leasehold improvements are amortized over the remaining lease term or the related useful life, if shorter. When an asset is disposed of, the associated cost and accumulated depreciation is removed from the related accounts on the Company's balance sheet with any resulting gain or loss included in the Company's statement of operations. Operating Lease Right-of-use Asset and Lease Liability The Company accounts for leases under ASC Topic 842, Leases . The Company determines if an arrangement is a lease at inception. Operating leases are included in long-term right-of-use assets and current and long-term lease liabilities within the Company’s balance sheets. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The right-of-use assets are tested for impairment according to ASC 360. Leases with an initial term of 12 months or less are not recorded on the balance sheet and are recognized as lease expense on a straight-line basis over the lease term. In December 2019, the Company determined it was reasonably certain that it would exercise its five-year renewal option to extend its Exton, PA office lease, which was scheduled to expired in May 2020. As a result of this determination, the renewal option was included in the lease term and the Company recorded an incremental ROU asset and lease liability of $1.0 million as of December 31, 2019, the date this determination was made. Subsequently, in January 2020, the Company exercised its option to renew and extend the lease term for a period of five years from June 1, 2020 through May 31, 2025. Impairment of Long-Lived Assets In accordance with ASC 360-10-35, Impairment or Disposal of Long-Lived Assets , the Company reviews its long-lived assets and identifiable finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable (i.e. impaired). Once an impairment is determined, the actual impairment recognized is the difference between the carrying amount and the fair value (less costs to sell for assets to be disposed of) as estimated using one of the following approaches: income, cost and/or market. Fair value using the income approach is determined primarily using a discounted cash flow model that uses the estimated cash flows associated with the asset or asset group under review, discounted at a rate commensurate with the risk involved. Fair value utilizing the cost approach is determined based on the replacement cost of the asset reduced for, among other things, depreciation and obsolescence. Fair value, utilizing the market approach, benchmarks the fair value against the carrying amount. Note 2. Summary of Significant Accounting Policies (Continued) Warrant Liability The Company accounts for stock warrants as either equity instruments, liabilities or derivative liabilities in accordance with ASC 480, Distinguishing Liabilities from Equity (ASC 480) and/or ASC 815, Derivatives and Hedging (ASC 815), depending on the specific terms of the warrant agreement. Freestanding warrants for shares that are potentially redeemable, whereby the Company may be required to transfer assets (e.g. cash or other assets) outside of its control, are classified as liabilities. Liability-classified warrants are recorded at their estimated fair values at each reporting period until they are exercised, terminated, reclassified or otherwise settled. Changes in the estimated fair value of liability-classified warrants are recorded in Warrant Revaluation Income (Expense) in the Company’s statements of operations and comprehensive loss. Equity classified warrants are recorded within additional paid-in capital at the time of issuance and not subject to remeasurement. For additional discussion on warrants, see Note 8. Future Tranche Right Liability In connection with the Company’s 2019 Private Placement, as more fully described in Note 7, the Company entered into the December 2019 Securities Purchase Agreement, which 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 a liabilities (“Future Tranche Right Liability”) under ASC 480, which requires the measurement of the fair value of the liability at the time of issuance and recording changes as a charge to current earnings at each reporting period, which is included in Future Tranche Right Liability Revaluation Expense in the Company’s statements of operations and comprehensive loss. 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. Redeemable Preferred Stock Issued with Other Freestanding Instruments The Company considers guidance within ASC 470-20, Debt (ASC 470), ASC 480, and ASC 815 when accounting for a redeemable equity instrument issued with other freestanding instruments (e.g. detachable warrants and future tranche right liabilities), such as in the December 2019 Private Placement. In circumstances in which redeemable convertible preferred stock is issued with freestanding liability-classified instruments, the proceeds from the issuance of the convertible preferred stock are first allocated to those instruments at their full estimated fair value. The remaining proceeds, as further reduced by discounts created by the bifurcation of embedded derivatives and/or beneficial conversion features, if any, are allocated to the redeemable equity instrument. See Note 7 for additional discussion on the Company’s accounting for the 2019 Private Placement. Note 2. Summary of Significant Accounting Policies (Continued) Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606’), which applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. In accordance with ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC Topic 606, it performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current portion of deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Alliance Revenues The Company’s revenues have primarily been generated through collaborative research, development and/or commercialization agreements. The terms of these agreements may include payment to the Company of one or more of the following: nonrefundable, up-front license fees; research, development and commercial milestone payments; and other contingent payments due based on the activities of the counterparty or the reimbursement by licensees of costs associated with patent maintenance. Each of these types of revenue are recorded as Alliance revenues in the Company’s statements of operations. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Note 2. Summary of Significant Accounting Policies (Continued) See Note 10, “Collaboration and License Agreements” for additional details regarding the Company’s collaboration arrangements. As part of the accounting for these arrangements, the Company allocates the transaction price to each performance obligation on a relative stand-alone selling price basis. The stand-alone selling price may be, but is not presumed to be, the contract price. In determining the allocation, the Company maximizes the use of observable inputs. When the stand-alone selling price of a good or service is not directly observable, the Company estimates the stand-alone selling price for each performance obligation using assumptions that require judgment. Acceptable estimation methods include, but are not limited to: (i) the adjusted market assessment approach, (ii) the expected cost plus margin approach, and (iii) the residual approach (when the stand-alone selling price is not directly observable and is either highly variable or uncertain). In order for the residual approach to be used, the Company must demonstrate that (a) there are observable stand-alone selling prices for one or more of the performance obligations and (b) one of the two criteria in ASC 606-10-32-34(c)(1) and (2) is met. The residual approach cannot be used if it would result in a stand-alone selling price of zero for a performance obligation as a performance obligation, by definition, has value on a stand-alone basis. An option in a contract to acquire additional goods or services gives rise to a performance obligation only if the option provides a material right to the customer that it would not receive without entering into that contract. Factors that the Company considers in evaluating whether an option represents a material right include, but are not limited to: (i) the overall objective of the arrangement, (ii) the benefit the collaborator might obtain from the arrangement without exercising the option, (iii) the cost to exercise the option (e.g. priced at a significant and incremental discount) and (iv) the likelihood that the option will be exercised. With respect to options determined to be performance obligations, the Company recognizes revenue when those future goods or services are transferred or when the options expire. The Company’s revenue arrangements may include the following: Up-front License Fees: If a license is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of an agreement that includes research and development milestone payments, the Company evaluates whether each milestone is considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect Alliance revenues and earnings in the period of adjustment. Research and Development Activities: If the Company is entitled to reimbursement from its collaborators for specified research and development activities or the reimbursement of costs associated with patent maintenance, the Company determines whether such funding would result in Alliance revenues or an offset to research and development expenses. Reimbursement of patent maintenance costs are recognized during the period in which the related expenses are incurred as Alliance revenues in the Company’s statements of operations. Note 2. Summary of Significant Accounting Policies (Continued) Royalties: If the Company is entitled to receive sales-based royalties from its collaborator, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, provided the reported sales are reliably measurable, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaboration and license arrangements. Manufacturing Supply and Research Services: Arrangements that include a promise for future supply of drug substance, drug product or research services at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the licensee exercises these options, any additional payments are recorded in Alliance revenues when the licensee obtains control of the goods, which is upon delivery, or as the services are performed. The Company receives payments from its licensees based on schedules established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less. Research and Development Expenses All research and development expenses are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including drug development trials and studies, drug manufacturing, laboratory supplies, external research, payroll including stock-based compensation and overhead. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are accepted by the Company or the services are performed. As of December 31, 2019 and 2018, the Company recorded approximately $2.8 million and $0.6 million as prepaid research and development, respectively, which is included within prepaid expenses and other current assets in the accompanying balance sheets. Stock-Based Compensation The Company accounts for stock-based compensation using ASC 718, Compensation – Stock Compensation (“ASC 718”), or ASC 505-50, Equity – Equity Based Payments to Non-Employees , as applicable. The Company accounts for stock-based awards to employees and non-employee directors using the fair value based method to determine compensation expense for all arrangements where shares of stock or equity instruments are issued for compensation. In addition, the Company accounts for stock-based compensation to other non-employees in accordance with the accounting guidance for equity instruments that are issued to entities or persons other than employees. The Company recognizes all share-based payments to employees and directors as expense in the statements of operations and comprehensive loss based on their fair values. The Company records compensation expense on a straight-line basis over an award’s requisite service period, or vesting period, based on the award’s fair value at the date of grant. Vesting is generally four years for employees and one year for directors. The Company uses a Black-Scholes option-pricing model to determine the fair value of each option grant as of the date of grant for expense incurred. The Black-Scholes option pricing model requires inputs for risk-free interest rate, dividend yield, expected stock price volatility and expected term of the options. See Note 12, “Stock-based Compensation” for additional details. Note 2. Summary of Significant Accounting Policies (Continued) Prior to the adoption of Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), ASC 718 required forfeitures to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differed from those estimates. However, ASU 2016-09 allows an entity to elect as an accounting policy upon adoption either to continue to estimate the total number of awards for which the requisite service period will not be rendered or to account for forfeitures when they occur. In connection with the adoption of this ASU in the first quarter of 2017, the Company made an accounting policy election to account for forfeitures as they occur and applied this change in accounting policy on a modified retrospective basis, resulting in less than a $0.1 million reduction in Additional paid-in capital and an increase in Accumulated deficit as of January 1, 2017, to reflect the cumulative effect of previously estimated forfeitures. See the caption “ Cumulative effect from adoption of new accounting standard” within the accompanying statements of redeemable preferred stock and stockholders’ equity (deficit). Merger-related Costs, net On January 21, 2018, the Company, BioCryst Pharmaceuticals, Inc., a Delaware corporation (“BioCryst”), Nautilus Holdco, Inc., a Delaware corporation and a direct, wholly owned subsidiary of BioCryst (“Holdco”), Island Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Holdco, and Boat Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Holdco, entered into an Agreement and Plan of Merger (the “Merger Agreement”). The board of directors of each of Idera and BioCryst unanimously approved the Merger Agreement and the transactions contemplated thereby and the required regulatory approvals were received. However, the proposed merger was subject to approval by the stockholders of Idera and BioCryst, and satisfaction of other customary closing conditions, as specified in the Merger Agreement. At a special meeting of BioCryst stockholders held on July 10, 2018, BioCryst’s stockholders voted against the adoption of the Merger Agreement. Following such vote and in accordance with the terms of the Merger Agreement, BioCryst terminated the Merger Agreement. In accordance with the Merger Agreement, BioCryst paid the Company a fixed expense reimbursement amount of $6 million in July 2018 in connection with the termination of the Merger Agreement. The fixed expense reimbursement amount is included in “Merger-related costs, net” in the accompanying statements of operations. Merger-related costs, net includes amounts related to the transactions contemplated under the Merger Agreement, including charges incurred for transaction and integration-related professional fees, employee retention costs, and other incremental costs directly related to the potential merger; less the $6 million fixed expense reimbursement termination fee, which was received by the Company in July 2018. Restructuring Costs Restructuring charges are primarily comprised of severance costs related to workforce reductions, contract termination and wind-down costs and asset impairments. In accordance with ASC 420, Exit or Disposal Cost Obligations , the Company recognizes restructuring charges when the liability has been incurred, except for one-time employee termination benefits that are incurred over time. Generally, one-time employee termination benefits (i.e. severance costs) are accrued at the date management has committed to a plan of termination and employees have been notified of their termination dates and expected severance payments. Other costs will be recorded as incurred. Asset impairment charges have been, and will be, recognized when management has concluded that the assets have been impaired in accordance with ASC 360-10-35, Impairment or Disposal of Long-Lived Assets , or other applicable authoritative guidance. See Note 11 for additional details. Income Taxes An asset and liability approach is used for financial accounting and reporting for income taxes. Deferred income taxes arise from temporary differences between income tax and financial reporting and principally relate to recognition of revenue and expenses in different periods for financial and tax accounting purposes and are measured using currently enacted tax rates and laws. In addition, a deferred tax asset can be generated by a net operating loss carryover. If it is more likely than not that some portion or all of a deferred tax asset will not be realized, a valuation allowance is recognized. Note 2. Summary of Significant Accounting Policies (Continued) In the event the Company is charged interest or penalties related to income tax matters, the Company would record such interest as interest expense and would record such penalties as other expense in the Statements of Operations. No such charges have been incurred by the Company. For each of the years ended December 31, 2019, 2018 and 2017, the Company had no uncertain tax positions. See Note 14, “Income Taxes” for additional details. Net Loss per Common Share applicable to Common Stockholders Basic and diluted net loss per common share applicable to common stockholders is computed using the weighted average number of shares of common stock outstanding during the period. The diluted loss per share calculation gives effect to dilutive stock options, warrants, convertible preferred stock and other potentially dilutive common stock equivalents outstanding during the period. Diluted loss per share is based on the if-converted method or the treasury stock method, as applicable, and includes the effect from the potential issuance of common stock, such as shares issuable pursuant to the conversion of convertible preferred stock and the exercise of stock options and warrants, assuming the exercise of all “in-the-money” common stock equivalents based on the average market price during the period. Common stock equivalents have been excluded where their inclusion would be anti-dilutive. Diluted net loss per common share applicable to common stockholders is the same as basic net loss per common share applicable to common stockholders for each of the three years in the period ended December 31, 2019 as the effects of the Company’s potential common stock equivalents are antidilutive (see Note 17). Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017 is comprised of reported net income (loss) and any change in net unrealized gains and losses on investments in available-for-sale securities during each year, which is included in “Accumulated other comprehensive income” on the accompanying balance sheets. In accordance with ASC Topic 220, Comprehensive Income , the Company has elected to present the components of net income and other comprehensive income as one continuous statement. New Accounting Pronouncements Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 requires organizations that lease assets, with lease terms of more than 12 months, to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Consistent with GAAP, the recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will depend primarily on its classification as a finance or operating lease. However, unlike the previous standard, which required only capital leases to be recognized on the balance sheet, ASU 2016-02 requires both types of leases to be recognized on the balance sheet. This guidance was applicable to the Company's fiscal year beginning January 1, 2019, and the Company adopted ASU 2016-02 in the first quarter of 2019 using the alternative modified retrospective transition method, which allowed the Company to apply the new lease standard to the beginning of the 2019 period and did not require adjusting comparative period financial information. Additionally, the Company elected the package of practical expedients to not reassess prior conclusions related to contracts containing leases, lease classification and initial direct costs. As a result of adopting ASU 2016-02, the primary impact on the Company’s fi

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Measurements
Fair Value Measurements	Note 3. Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis The Company applies the guidance in ASC 820, Fair Value Measurement , to account for financial assets and liabilities measured on a recurring basis. Fair value is measured at the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that is determined based on assumptions that market participants would use in pricing an asset or liability. The Company uses a fair value hierarchy, which distinguishes between assumptions based on market data (observable inputs) and an entity's own assumptions (unobservable inputs). The guidance requires that fair value measurements be classified and disclosed in one of the following three categories: · Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; · Level 2: Quoted prices in markets that are not active or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; · Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Determining which category an asset or liability falls within the hierarchy requires significant judgment. The Company evaluates its hierarchy disclosures each reporting period. There were no transfers between Level 1, 2 and 3 during the years ended December 31, 2019, 2018 and 2017. Note 3. Fair Value Measurements (Continued) The table below presents the assets and liabilities measured and recorded in the financial statements at fair value on a recurring basis at December 31, 2019 and 2018 categorized by the level of inputs used in the valuation of each asset and liability. December 31, 2019 (In thousands) Total Level 1 Level 2 Level 3 Assets Cash $ 250 $ 250 $ — $ — 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 December 31, 2018 (In thousands) Total Level 1 Level 2 Level 3 Assets Cash $ 8,446 $ 8,446 $ — $ — Money market funds 61,177 61,177 — — Other cash equivalents – commercial paper 1,808 — 1,808 — Total assets $ 71,431 $ 69,623 $ 1,808 $ — Total liabilities $ — $ — $ — $ — 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: Warrant Derivative (In thousands) Liability Liability Balance at December 31, 2018 $ — $ — Issuance of redeemable preferred stock and warrants (1) 2,643 35,472 Change in the fair value of liability 598 10,964 Balance at December 31, 2019 $ 3,241 $ 46,436 (1) Represents fair value of freestanding warrants and the future tranche right related to the December 2019 Private Placement on the issuance date . 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: December 23, December 31, 2019 2019 Risk-free interest rate Expected dividend yield — — Expected term (years) 7.00 6.98 Expected volatility 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. 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: December 23, December 31, 2019 2019 Risk-free interest rate for warrants Risk-free interest rate for preferred stock 1.86% - 1.89% 1.84% - 1.88% Expected dividend yield — — Expected term (years) of call option on preferred stock 1.18 - 2.18 1.16 - 2.16 Expected term (years) of warrants 8.18 - 9.18 8.16 - 9.16 Expected volatility Exercise price (per share) for common stock equivalent for preferred stock and warrant $ 1.52 - 1.82 $ 1.52 - 1.82 As of December 23, 2019 and December 31, 2019, the Company deemed it probable that shareholder approval would be obtained, on or prior to December 31, 2020, with respect to increasing the Company’s authorized shares of common stock in an amount sufficient to cover the conversion of all potential convertible securities issuable upon exercise of the Future Tranche Rights. See Note 7 for further details on the such required shareholder approval.

Investments

Investments	12 Months Ended
	Dec. 31, 2019
Investments
Investments	Note 4. Investments The Company’s available-for-sale investments at fair value consisted of the following at December 31, 2019: 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 Total investments $ 2,774 $ — $ — $ 2,774 The Company had no realized gains or losses from the sale of investments in available-for-sale securities in the year ended December 31, 2019. There were no losses or other-than-temporary declines in value included in “Interest income” on the Company’s statements of operations and comprehensive loss for any securities for the year ended December 31, 2019.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property and Equipment
Property and Equipment	Note 5. Property and Equipment At December 31, 2019 and 2018, net property and equipment at cost consisted of the following: December 31, December 31, (In thousands) 2019 2018 Leasehold improvements $ 107 $ 104 Equipment and other 764 767 Total property and equipment, at cost 871 871 Less: Accumulated depreciation and amortization 774 664 Property and equipment, net $ 97 $ 207 Depreciation and amortization expense on property and equipment was approximately $0.1 million, $0.4 million, and $0.7 million in 2019, 2018 and 2017, respectively. During the year ended December 31, 2018, the Company recorded asset impairments related to its property equipment in the amount of $0.5 million in connection with restructuring activities more fully described in Note 11. No impairment charges were recognized during the years ended December 31, 2019 or 2017.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Accrued Expenses	Note 6. Accrued Expenses At December 31, 2019 and 2018, accrued expenses consisted of the following: December 31, December 31, (In thousands) 2019 2018 Payroll and related costs $ 2,179 $ 1,962 Clinical and nonclinical trial expenses 4,199 3,958 Professional and consulting fees 859 605 Restructuring expenses 113 1,147 Other 111 212 Total accrued expenses $ 7,461 $ 7,884 Included in accrued Payroll and related costs as December 31, 2018 is $0.7 million of salary continuation severance benefits which was paid in equal installments through October 31, 2019 to former executives.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2019
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 a Securities Purchase Agreement (the “December 2019 Securities Purchase Agreement”) with institutional investors affiliated with Baker Brothers (the “Purchasers”), an existing shareholder and related party as more fully described in Note 16, 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, we have agreed to sell to the Purchasers, at their option and subject to certain conditions including stockholder approval to increase the Company’s authorized shares of common stock, 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 after stockholder approval is received (the “Future Tranche Rights”) as follows: Price Per Aggregate Future Tranche Rights Preferred Shares Share Purchase Price Tranche 2 (Series B2) (1) 98,685 $ $ 15,000,120 Tranche 3 (Series B3) (2) 82,418 $ 15,000,076 Tranche 4 (Series B4) (2) 82,418 $ 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 the event the Company does 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 shall be returned to the Purchasers. The Board recommends the stockholders support the proposal to increase the authorized shares. The purchase and sale of the securities issuable under tranches 2, 3 and 4 may occur in two or more 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 9 months, 15 months, and 21 months following shareholder approval, 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 to receive aggregate gross proceeds of up to an additional $87.6 million under the December 2019 Securities Purchase Agreement. Note 7. Redeemable Convertible Preferred Stock (Continued) Accounting Considerations The Company determined that the Series B1 Preferred Stock, the accompanying Series B1 warrants, and each of the Future Tranche Rights represented a freestanding financial instrument. The warrants and the Future Tranche Rights are liability classified as the underlying shares are potentially redeemable and such redemption is deemed to be outside of the Company’s control. The $10.1 million in gross proceeds received in December 2019 was allocated to the Series B1 warrants and the Future Tranche Rights based on their estimated fair values of $2.6 million and $35.5 million, respectively. The excess fair value of $28.0 million over the gross proceeds received of $10.1 million was recorded as a deemed dividend to Baker Brothers, an existing significant shareholder. Costs in connection with the December 2019 Securities Purchase Agreement were expensed as incurred. Due to the redeemable nature of the Series B1 Preferred Stock, the Series B1 Preferred Stock has been 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 December 31, 2019. 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 year ended December 31, 2019, accretion was de minimis.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity
Stockholders' Equity	Note 8. Stockholders’ Equity Preferred Stock The Restated Certificate of Incorporation, as amended, of the Company permits its board of directors to issue up to 5,000,000 shares of preferred stock, par value $0.01 per share, in one or more series, to designate the number of shares constituting such series, and fix by resolution, the powers, privileges, preferences and relative, optional or special rights thereof, including liquidation preferences and dividends, and conversion and redemption rights of each such series. As of December 31, 2019, the Company has designated the following class of preferred stock: · Series A: · Series B1: · Series B2: · Series B3: · Series B4: Note 8. Stockholders’ Equity (Continued) Series A Convertible Preferred Stock . The dividends on the Series A convertible preferred stock (“Series A Preferred Stock”) are payable semi-annually in arrears at the rate of 1% per annum, at the election of the Company, either in cash or additional duly designated, fully paid and nonassessable shares of Series A Preferred Stock. In the event of liquidation, dissolution or winding up of the Company, after payment of debts and other liabilities of the Company, the holders of the Series A Preferred Stock then outstanding will be entitled to a distribution of $1 per share out of any assets available to shareholders. The Series A Preferred Stock is non-voting. All remaining shares of Series A Preferred Stock rank, as to payment upon the occurrence of any liquidation event, senior to the Company’s common stock. Shares of Series A Preferred Stock are convertible, in whole or in part, at the option of the holder into fully paid and nonassessable shares of common stock at $272.00 per share, subject to adjustment. As of December 31, 2019 and 2018, there were 655 shares of Series A Preferred Stock outstanding. Series B1, B2, B3 and B4 Convertible Preferred Stock . Holders of Series B1 Preferred Stock, Series B2 Preferred Stock, Series B3 Preferred Stock and Series B4 Preferred Stock (collectively, the “B1/B2/B3/B4 Preferred Stock”) are entitled to the amount of dividends, if and when declared, as would be payable to holders of common stock on an “as converted” basis (e.g. participating dividends). Until the applicable Transition Date (defined below), in the event of a liquidation event or deemed liquidation event, after payment of debts and other liabilities of the Company, the holders of the Series B1/B2/B3/B4 Preferred Stock then outstanding will be entitled to a distribution equal to the then applicable stated value per share of the Series B1/B2/B3/B4 Preferred Stock. Additionally, until the applicable Transition Date (defined below), at any time on or after the date that is the fifth (5th) anniversary of the initial issue date of the applicable series of preferred stock, all or any portion of the preferred stock is redeemable at the option of the holder at a redemption price of $152.00 per share (for Series B1 and Series B2 Preferred Stock) and $182.00 per share (for Series B3 and Series B4 Preferred Stock). The “Transition Date” means: a) With respect to the Series B1 Preferred Stock, the first date following December 23, 2021, on which each of the Conditions (as defined below) is met (the “Series B1 Transition Date”); and b) With respect to the Series B2 Preferred Stock, Series B3 Preferred Stock and Series B4 Preferred Stock, the first date following the two-year anniversary of the applicable series of preferred stock’s initial issue date, on which each of the Conditions (as defined below) is met (the “Series B2 Transition Date”). The “Conditions” shall mean: (a) the closing price of the Company’s common stock has been equal to or exceeded the price that is equal to three times (3x) the applicable series of preferred stock’s conversion price ($1.52 for Series B1 Preferred Stock and B2 Preferred Stock; $1.82 for Series B3 Preferred Stock and Series B4 Preferred Stock) for 180 calendar days; (b) the 50-day average trading volume of the Company’s common stock is greater than 500,000 shares (subject to adjustment for any stock dividend, stock split, stock combination or other similar transaction); and (c) the presentation by the Company at an appropriate medical conference of the “Overall Survival” data as defined in its ILLUMINATE-301 study protocol. The Series B1/B2/B3/B4 Preferred Stock is non-voting and rank, as to payment upon the occurrence of any liquidation event, senior to the Company’s common stock. Shares of Series B1 Preferred Stock and Series B2 Preferred Stock are convertible, in whole or in part, at the option of the holder into fully paid and nonassessable shares of common stock at $1.52 per share, subject to adjustment. Shares of Series B2 Preferred Stock and Series B3 Preferred Stock are convertible, in whole or in part, at the option of the holder into fully paid and nonassessable shares of common stock at $1.82 per share, subject to adjustment. As more fully described in Note 7, the Company’s outstanding Series B1 Preferred Stock is classified in temporary equity, outside of stockholders’ equity as of December 31, 2019. No shares of Series B2 Preferred Stock, Series B3 Preferred Stock or Series B4 Preferred Stock are outstanding as of December 31, 2019. Note 8. Stockholders’ Equity (Continued) Common Stock On June 20, 2018, the Company's stockholders approved an amendment to the Company's Restated Certificate of Incorporation, as amended, to effect a reverse stock split of the Company's outstanding shares of common stock at a ratio within a range from 1-for-4 to 1-for-8 and set the number of authorized shares of the Company’s common stock at a number determined by calculating the product of 280,000,000 (previous number of authorized shares) multiplied by two times (2x) the reverse stock split ratio. On July 27, 2018, the Company implemented a 1-for-8 reverse split of its issued and outstanding shares of common stock (the “Reverse Split”), and set the number of its authorized shares of common stock to 70,000,000. The Reverse Split became effective on July 27, 2018 at 5:00 p.m., Eastern Time, and the Company’s common stock began trading on the Nasdaq Capital Market on a Reverse Split-adjusted basis at the opening of trading on July 30, 2018. As of a result of the Reverse Split, every eight shares of the Company’s issued and outstanding common stock were combined into one share of its common stock, except to the extent that the Reverse Split resulted in any of the Company’s stockholders owning a fractional share, which was settled in cash. In connection with the Reverse Split, there was no change in the nominal par value per share of $0.001. The Reverse Split did not change the number of authorized shares or par value of the Company’s preferred stock. Common Stock Authorized As of December 31, 2019, the Company had 70,000,000 shares of common stock authorized of which 25,066,074 shares of common stock were reserved for the issuance upon the exercise of outstanding warrants and options to purchase common stock, outstanding restricted stock units, the conversion of Series A and Series B1 convertible preferred stock, shares required to be reserved under the LPC Purchase Agreement (defined below), and shares available for grant under the Company’s 2013 Stock Incentive Plan and shares available for purchase under the Company’s 2017 Employee Stock Purchase Plan. Put Shares Pursuant to the terms of a unit purchase agreement dated as of May 5, 1998, the Company issued and sold a total of 149,960 shares of common stock (the “Put Shares”) at a price of $128.00 per share. Under the terms of the unit purchase agreement, the initial purchasers (the “Put Holders”) of the Put Shares have the right (the “Put Right”) to require the Company to repurchase the Put Shares. The Put Right may not be exercised by any Put Holder unless: (1) the Company liquidates, dissolves or winds up its affairs pursuant to applicable bankruptcy law, whether voluntarily or involuntarily; (2) all of the Company’s indebtedness and obligations, including without limitation the indebtedness under the Company’s then outstanding notes, has been paid in full; and (3) all rights of the holders of any series or class of capital stock ranking prior and senior to the common stock with respect to liquidation, including without limitation the Series A convertible preferred stock, have been satisfied in full. The Company may terminate the Put Right upon written notice to the Put Holders if the closing sales price of its common stock exceeds $256.00 per share for the twenty consecutive trading days prior to the date of notice of termination. Because the Put Right is not transferable, in the event that a Put Holder has transferred Put Shares since May 5, 1998, the Put Right with respect to those shares has terminated. As a consequence of the Put Right, in the event the Company is liquidated, holders of shares of common stock that do not have Put Rights with respect to such shares may receive smaller distributions per share upon the liquidation than if there were no Put Rights outstanding. As of December 31, 2019, the Company has repurchased or received documentation of the transfer of 49,993 Put Shares and 4,472 of the Put Shares continued to be held in the name of Put Holders. The Company cannot determine at this time what portion of the Put Rights of the remaining 95,494 Put Shares have terminated. Note 8. Stockholders’ Equity (Continued) Equity Financings 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 year ended December 31, 2019, the Company sold 1,535,848 shares pursuant to the LPC Purchase Agreement, resulting in net proceeds of $3.7 million. "At-The-Market" Equity Program In November 2018, the Company entered into a 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 year ended December 31, 2019, the Company sold 532,700 Shares pursuant to the ATM Agreement resulting in net proceeds, after deduction of commissions and other offering expenses, of $1.6 million. No Shares were sold pursuant to the ATM Agreement during 2018. October 2017 Follow-on Underwritten Public Offering On October 30, 2017, the Company closed a follow-on underwritten public offering, in which it sold 4,166,666 shares of common stock at a price to the public of $12.00 per share for aggregate gross proceeds of $50.0 million (“2017 Offering”). On November 1, 2017, the Company sold an additional 625,000 shares of common stock pursuant to the exercise in full of the underwriters’ 30-day option to purchase additional shares of the Company’s common stock at the public offering price less the underwriting discount. The net proceeds to the Company from the 2017 Offering, including the exercise by the underwriters of their option to purchase additional shares and after deducting underwriters’ discounts and commissions and other offering costs and expenses, were approximately $53.7 million. Baker Brothers, which is affiliated with two of the Company’s directors, participated in the 2017 Offering and purchased 1,000,000 shares of the Company’s common stock at the price offered to the public. 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 stock and preferred stock. The Company accounts for common stock and preferred stock warrants as equity instruments or liabilities, depending on the specific terms of the warrant agreement. See Note 2 for further details on accounting policies related to the Company’s warrants. The following table summarizes outstanding warrants to purchase shares of the Company’s common stock and/or preferred stock as of December 31, 2019 and 2018: Number of Shares December 31, December 31, Weighted-Average Description 2019 2018 Exercise Price Expiration Date Liability-classified Warrants December 2019 Series B1 warrants (1) 2,368,400 — $ 1.52 Dec 2026 2,368,400 — Equity-classified Warrants May 2013 warrants 1,949,754 1,977,041 $ 0.08 None (2) September 2013 warrants 514,756 521,997 $ 0.08 None (2) February 2014 warrants 266,006 269,844 $ 0.08 None (2) 2,730,516 2,768,882 Total outstanding 5,098,916 2,768,882 (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. (2) In connection with December 2019 Private Placement, the expiration date on these warrants was amended to be indefinite. The table below is a summary of the Company's warrant activity for the year ended December 31, 2019. Number of Weighted-Average Warrants Exercise Price Outstanding at December 31, 2018 2,768,882 $ 0.08 Issued (1) 2,368,400 1.52 Exercised (38,366) 0.08 Expired — — Outstanding at December 31, 2019 5,098,916 $ 0.75 (1) During the year ended December 31, 2019, certain related parties were issued warrants as more fully described in Note 16.

Alliance Revenue

Alliance Revenue	12 Months Ended
	Dec. 31, 2019
Alliance Revenue
Alliance Revenue	Note 9. Alliance Revenue Alliance revenue for the years ended December 31, 2019, 2018 and 2017 represents revenue from contracts with customers accounted for in accordance with ASC Topic 606. For the years ended December 31, 2019, 2018 and 2017, Alliance revenue in the accompanying statements of operations and comprehensive loss is comprised of the following: (In thousands) 2019 2018 2017 Out-license arrangement (1) $ 1,447 $ — $ — GSK collaboration (2) — 517 863 Vivelix collaboration (3) — 56 14 Other (4) 1 89 25 Total Alliance revenue $ 1,448 $ 662 $ 902 (1) For the year ended December 31, 2019, the Company recognized Alliance revenues of $1.4 million under the Licensee Agreement, as more fully described in Note 10, primarily related to the transfer of the IMO-8400 License and IMO-8400 drug product. (2) For the years ended December 31, 2018 and 2017, revenue recognized primarily relates to the amortization of the $2.5 million upfront, non-refundable, non-creditable cash payment received upon the execution of the GSK Agreement, as more fully described in Note 10, which was recognized as revenue on a straight-line basis over the estimated 36-month research plan period, which approximated the timing in which performance obligations were satisfied. No such revenue was recognized during 2019. Revenue recognized for the year ended December 31, 2017 also includes an additional $0.1 million related to additional research services performed in connection with the GSK Agreement. (3) For each of the years ended December 31, 2018 and 2017, revenue recognized relates to reimbursements for research services performed in connection with the Vivelix Agreement, as more fully described in Note 10. (4) For all periods presented, revenue recognized relates to collaborations which are not material to the Company’s current operations nor expected to be material in the future, including reimbursements by licensees of costs associated with patent maintenance. During each of the years ended December 31, 2018 and 2017, the Company recognized Alliance revenues of $0.6 million and $0.7 million, respectively, as a result of changes in the contract liability balances associated with its contracts with customers. Such revenue recognized was included in the contract liability balance at the beginning of each respective period. See Note 10 for additional details regarding the Company’s collaboration arrangements.

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2019
Collaboration and License Agreements
Collaboration and License Agreements	Note 10. 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 Note 10. Collaboration and License Agreements (Continued) Under the terms of the Licensee Agreement, the Company received upfront, non-refundable fees totaling approximately $1.4 million and ownership of 10% of Licensee’s outstanding common stock, subject to future adjustment, for granting Licensee the IMO-8400 License, the IMO-9200 Option Period License and transfer of related drug materials. In addition, the Company is eligible to receive a $1 million non-refundable fee upon Licensee exercising the IMO-9200 Option (“Option Fee”) and is entitled to certain sub-licensing payments on sublicense revenue received by Licensee, if any. The Company may also be eligible for certain development and sales-based milestone payments and royalties on global net sales for any future products. The Company does not anticipate the receipt of any of the future milestones or royalties in the short term, if ever. The Company concluded that the contract counterparty, Licensee, is a customer and accounted for the Licensee Agreement in accordance with ASC 606. As of December 31, 2019, the total transaction price of the contract was $1.4 million, which excluded the Option Fee and all development and sales milestones as all such payments were fully constrained. Additionally, as of December 31, 2019, there were no remaining performance obligations under the Licensee Agreement. The Company re-evaluates its performance obligations and 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 evaluated the guidance in ASC Topic 321, Investments-Equity Securities , and elected to account for the investment using the measurement alternative as the equity securities are without a readily determinable fair value, and the arrangement does not result in Idera having control or significant influence over Licensee. Accordingly, the securities are measured at cost, less any impairment, plus or minus changes resulting from observable price changes and are recorded in Other assets at a value of less than $0.1 million in the accompanying balance sheets. As of December 31, 2019, the Company considered the cost of the investment to not exceed the fair value of the investment and did not identify any observable price changes. See Note 9 for details on revenue recognized in connection with the Company’s collaboration with Licensee for each of the years ended December 31, 2019, 2018 and 2017. Collaboration with Vivelix In November 2016, the Company entered into an exclusive license and collaboration agreement with Vivelix Pharmaceuticals, Ltd. (“Vivelix”) pursuant to which the Company granted Vivelix worldwide rights to develop and market IMO-9200 for non-malignant gastrointestinal disorders and certain back-up compounds to IMO-9200 (the “Vivelix Agreement”). Under the terms of the Vivelix Agreement, Vivelix was solely responsible for the development and commercialization of IMO-9200 and any designated back-up compounds. In connection with the Vivelix Agreement, Idera also transferred certain drug material to Vivelix for Vivelix’s use in its development activities. Additionally, Vivelix could request that the Company create, characterize and perform research on back-up compounds. At the effective date of the Vivelix Agreement, Baker Bros. Advisors LP and certain of its affiliated funds (collectively “Baker Brothers”) beneficially owned approximately 7.0% of the Company’s outstanding common stock and affiliates of Baker Brothers constituted two of the four directors on the board of directors of Vivelix and two of the seven directors on the board of directors of the Company. Under the terms of the Vivelix Agreement, the Company received an upfront, non-refundable fee of $15 million related to the license granted for IMO-9200 and back-up compounds to IMO-9200, which was recognized at the inception of the Vivelix Agreement in the fourth quarter of 2016. Additionally, the Company was eligible for future IMO-9200 related development, regulatory and sales milestone payments and sales-based royalties. However, on March 4, 2019, the Company and Vivelix mutually agreed to terminate the Vivelix Agreement. Accordingly, the Company is no longer eligible to receive any future milestone or royalty-based payments and all rights previously granted to Vivelix with respect to IMO-9200 and certain back-up compounds to IMO-9200 reverted back to the Company. See Note 9 for details on revenue recognized in connection with the Company’s collaboration with Vivelix for each of the years ended December 31, 2019, 2018 and 2017. Note 10. Collaboration and License Agreements (Continued) Collaboration with GSK In November 2015, the Company entered into a collaboration and license agreement with GSK to license, research, develop and commercialize pharmaceutical compounds from the Company’s nucleic acid chemistry technology for the treatment of selected targets in renal disease (the “GSK Agreement”). In connection with the GSK Agreement, GSK identified an initial target for the Company to attempt to identify a potential population of development candidates to address such target under a mutually agreed upon research plan. Prior to the wind-down of its discovery operations as more fully described in Note 10, the Company created multiple development candidates to address the initial target designated by GSK. Until November 2019, the expiration of the collaboration term, GSK had the right to designate one development candidate in its sole discretion, from the population of identified candidates, to move forward into clinical development. However, GSK did not designate any candidate for development during the collaboration term. If such designation had occurred, GSK would have been solely responsible for the development and commercialization activities of that designated development candidate. The GSK Agreement also provided GSK with the option to select up to two additional targets at any time during the first two years of the GSK agreement, for further research under mutually agreed upon research plans. Upon selecting additional targets, GSK then had the option to designate one development candidate for each additional target, at which time GSK would have sole responsibility to develop and commercialize each such designated development candidate. GSK did not select any additional targets for research through expiry of the option period. Under the terms of the GSK Agreement, the Company received a $2.5 million upfront, non-refundable, non-creditable cash payment upon the execution of the GSK Agreement. Additionally, the Company was initially eligible to receive a total of up to approximately $100 million in license, research, clinical development and commercialization milestone payments, of which $9 million of these milestone payments would have been payable by GSK upon the identification of the additional targets, the completion of current and future research plans and the designation of development candidates and $89 million would have been payable by GSK upon the achievement of clinical milestones and commercial milestones. As a result of GSK not designating a development candidate during the collaboration term, the Company is no longer eligible to receive any additional license, research, clinical development and commercialization milestone payments, or any royalty payments. See Note 9 for details on revenue recognized in connection with the Company’s collaboration with GSK for each of the years ended December 31, 2019, 2018 and 2017. Collaboration with Abbott Molecular Inc. In May 2014, the Company entered into a development and commercialization agreement with Abbott Molecular, Inc. (“Abbott Molecular”) for the development of an in vitro companion diagnostic intended to be used in the Company’s prior clinical development programs to treat certain genetically defined forms of B-cell lymphoma with IMO-8400. The agreement provided for the development and subsequent commercialization by Abbott Molecular of a companion diagnostic test utilizing polymerase chain reaction technology to identify with high sensitivity and specificity the presence in tumor biopsy samples of the oncogenic mutation referred to scientifically as MYD88 L265P. Under the agreement, Abbott Molecular was primarily responsible for developing and obtaining regulatory approvals for the companion diagnostic in accordance with an agreed development plan and regulatory plan and for making the companion diagnostic test commercially available in accordance with an agreed commercialization plan. Abbott Molecular would retain all proceeds from commercialization of the companion diagnostic test, if any. In September 2016, the Company suspended internal clinical development of IMO-8400 for B-cell lymphomas. While the Company has maintained its relationship with Abbott, the Company is permitted to terminate the agreement upon 90 days written notice to Abbott Molecular and, under circumstances specified in the agreement, payment of a termination fee and wind-down costs. The parties also may terminate the agreement based on uncured material breaches by or the bankruptcy or insolvency of the other party, and each party has the right to terminate the agreement in the event of specified permanent injunctions based on infringement of third party intellectual property rights. Note 10. Collaboration and License Agreements (Continued) The Company incurred approximately $0.4 million, and $0.8 million in expenses under the Abbott Molecular agreement during the years ended December 31, 2018 and 2017, respectively, related to funding Abbott Molecular’s development of the companion diagnostic test. No such costs were incurred during 2019.

Restructuring Costs

Restructuring Costs	12 Months Ended
	Dec. 31, 2019
Restructuring Costs
Restructuring Costs	Note 11. Restructuring Costs In July 2018, the Company determined to wind-down its discovery operations, reduce the workforce in Cambridge, Massachusetts that supports such operations, and close its Cambridge facility. In connection with the reduction-in-workforce, 18 positions were being eliminated, primarily in the area of discovery, representing approximately 40% of the Company’s employees. Of the 18 positions eliminated, 15 were effective July 31, 2018 with the remaining effective during the first half of 2019. The Company completed the consolidation of its operations to its Exton, Pennsylvania location in the third quarter of 2018. Total restructuring-related charges incurred through December 31, 2019 totaled $3.3 million and were comprised of (i) one-time termination costs in connection with the reduction in workforce, including severance, benefits and related costs, of approximately $2.8 million; (ii) contract termination costs of approximately $0.2 million in connection with the early lease termination for the Cambridge facility; and (iii) non-cash asset impairments of approximately $0.7 million, inclusive of $0.5 million of fixed asset impairments and $0.2 million in write-offs of facility-related prepaid expenses; offset by (iv) a non-cash gain of approximately $0.4 million related to the write-off of the remaining deferred rent liability associated with the Cambridge facility lease. The following summarizes restructuring-related activity for the years ended December 31, 2019 and 2018: (in thousands) Employee Severance Contract Termination Costs Asset Impairments Total Accrued restructuring balance as of December 31, 2017 $ — $ — $ — $ — Charges incurred (1) 2,635 225 674 3,534 Cash payments (1,380) (225) — (1,605) Non-cash settlements (24) — (674) (698) Adjustments (84) — — (84) Accrued restructuring balance as of December 31, 2018 $ 1,147 $ — $ — $ 1,147 Charges incurred 181 — — 181 Cash payments (1,215) — — (1,215) Accrued restructuring balance as of December 31, 2019 $ 113 $ — $ — $ 113 (1) Excludes $0.4 million gain due to the write-off of the remaining deferred rent liability associated with the termination of the Cambridge, Massachusetts facility lease. As of December 31, 2019, the entire accrued restructuring balance is classified as a current liability and included in “Accrued expenses” in the accompanying balance sheets. See Note 6.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Stock-Based Compensation
Stock-Based Compensation	Note 12. Stock-based Compensation As of December 31, 2019, the only equity compensation plans from which the Company may currently issue new awards are the Company’s 2013 Stock Incentive Plan Equity Incentive Plans 2013 Stock Incentive Plan The Company's board of directors adopted the 2013 Plan Amendments to the 2013 Plan were approved by the Company’s stockholders in June 2014, June 2015, June 2017 and June 2019. The 2013 Plan is intended to further align the interests of the Company and its stockholders with its employees, including its officers, non-employee directors, consultants and advisers by providing equity-based incentives. T he 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 As of December 31, 2019, options to purchase a total of 3,459,693 shares of common stock and 193,625 restricted stock units were outstanding and up to 2,301,240 shares of common stock remained available for grant under the 2013 Plan. 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 December 31, 2019, options to purchase a total of 366,974 shares of common stock were outstanding under the 2008 Plan. In addition, as of December 31, 2019, non-statutory stock options to purchase an aggregate of 393,750 shares of common stock were outstanding that were issued outside of the 2013 Plan to certain employees in 2017, 2015 and 2014 pursuant to the Nasdaq inducement grant exception as a material component of new hires’ employment compensation. Employee Stock Purchase Plans 1995 Employee Stock Purchase Plan The Company’s 1995 Employee Stock Purchase Plan (the “1995 ESPP”), as amended, provided for the issuance of up to 62,500 shares of common stock to participating employees of the Company or its subsidiaries. The 1995 ESPP was terminated effective August 31, 2017 as a result of the adoption by the Company’s board of directors and approval of shareholders of the 2017 Employee Stock Purchase Plan (the “2017 ESPP”), as described below. 2017 Employee Stock Purchase Plan The Company’s board of directors adopted the 2017 ESPP which was approved by the Company’s stockholders and became effective June 7, 2017. An amendment to the 2017 ESPP was approved by the Company’s stockholders in June 2019. The 2017 ESPP is intended to qualify as an "employee stock purchase plan" as defined in Section 423 of the Internal Revenue Code, and is intended to encourage our employees to become stockholders of ours, to stimulate increased interest in our affairs and success, to afford employees the opportunity to share in our earnings and growth and to promote systematic savings by them. 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. Participation is limited to employees that would not own 5% or more of the total combined voting power or value of the stock of the Company after the grant. As of December 31, 2019, 321,341 shares remained available for issuance under the 2017 ESPP. Note 12. Stock-based Compensation (Continued) Stock Purchase Plan Administration The 1995 ESPP provided for and 2017 ESPP provides for offerings to employees to purchase common stock with offerings beginning on dates determined by the compensation committee of the board of directors or on the first business day thereafter. Each offering begins a “plan period” during which payroll deductions are to be made and held for the purchase of common stock at the end of the plan period. The compensation committee may, at its discretion, choose a plan period of 12 months or less for subsequent offerings and/or choose a different commencement date for offerings. During each plan period participating employees may elect to have a portion of their compensation, ranging from 1% to 10% of compensation as defined by the plan, withheld and used for the purchase of common stock at the end of each plan period. The purchase price is equal to 85% of the lower of the fair market value of a share of common stock on the first trading date of each plan period or the fair market value of a share of common stock on the last trading day of the plan period, and is limited by participant to $25,000 in fair value of common stock per year as well as other quarterly plan limitations as defined by each plan. For the years ended December 31, 2019, 2018 and 2017, the Company issued 60,953, 24,824, and 21,869 shares of common stock, respectively, under the Company’s employee stock purchase plans and recognized $0.1 million, $0.1 million, and $0.2 million, respectively, in related stock-based compensation expense. 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 fair value of the discounted purchases made under the Company’s 2015 ESPP and 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 statements of operations for the years ended December 31, 2019, 2018 and 2017 was as follows: (in thousands) 2019 2018 2017 Stock-based compensation: Research and development Employee Stock Purchase Plans $ 36 $ 71 $ 96 Equity Incentive Plans (1) 1,312 1,780 6,398 $ 1,348 $ 1,851 $ 6,494 General and administrative Employee Stock Purchase Plans $ 20 $ 48 $ 63 Equity Incentive Plans 2,477 3,751 4,163 $ 2,497 $ 3,799 $ 4,226 Restructuring costs Equity Incentive Plans $ — $ 24 $ — $ — $ 24 $ — Total stock-based compensation expense $ 3,845 $ 5,674 $ 10,720 (1) The 2017 charge includes approximately $4.3 million of additional stock-based compensation recognized as a result of modifications to previously issued stock option awards in connection with the resignation of an executive. During the years ended December 31, 2019, 2018 and 2017, the weighted average fair market value of stock options granted was $1.64, $7.00, and $8.08, respectively. Note 12. Stock-based Compensation (Continued) Assumptions Used in Determining Fair Value of Stock Options Inherent in the Black-Scholes option-pricing model are the following assumptions: Volatility . The Company estimates stock price volatility based on the Company’s historical stock price performance over a period of time that matches the expected term of the stock options. Risk-free interest rate . The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant commensurate with the expected term assumption. Expected term . The expected term of stock options granted is based on an estimate of when options will be exercised or cancelled in the future. Dividend rate. The dividend rate is based on the historical rate, which the Company anticipates will remain at zero. Forfeitures . The Company accounts for forfeitures when they occur. Ultimately, the actual expense recognized over the vesting period will be for only those shares that vest. See Note 2. The fair value of each option award at the date of grant was estimated using the Black-Scholes option pricing model. All options granted during the three years in the period ended December 31, 2019 were granted at exercise prices equal to the fair market value of the common stock on the dates of grant . The following weighted average assumptions apply to the options to purchase 1,279,016, 1,136,874, and 527,039 shares of common stock granted to employees and directors during the years ended December 31, 2019, 2018 and 2017, respectively: 2019 2018 2017 Average risk-free interest rate Expected dividend yield — — — Expected lives (years) 3.7 3.7 4.0 Expected volatility Weighted average exercise price (per share) $ 2.75 $ 12.63 $ 12.96 All options granted during the year ended December 31, 2019 and 2018 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 year ended December 31, 2019. ($ in thousands, except per share data) Stock Weighted-Average Weighted-Average Aggregate Outstanding at December 31, 2018 3,304,531 $ 18.41 6.6 $ Granted 1,279,016 2.75 Exercised — — Forfeited (143,874) 12.95 Expired (219,256) 31.29 Outstanding at December 31, 2019 (1) 4,220,417 $ 13.08 6.6 $ — Exercisable at December 31, 2019 2,292,157 $ 19.20 4.7 $ — (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. Note 12. Stock-based Compensation (Continued) The fair value of options that vested during the year ended December 31, 2019 was $4.7 million. As of December 31, 2019, there was $5.2 million of unrecognized compensation cost related to unvested options, which the Company expects to recognize over a weighted average period of 2.5 years. Restricted Stock Activity The following table summarizes restricted stock activity for the year ended December 31, 2019: ($ in thousands, except per share data) Number of Shares Weighted-Average Nonvested shares at December 31, 2018 — $ — Granted 194,550 3.14 Cancelled (925) 3.14 Vested — — Nonvested shares at December 31, 2019 193,625 $ 3.14 As of December 31, 2019, there was $0.5 million of unrecognized compensation cost related to the restricted stock units, which is expected to be recognized over a weighted average period of 3.0 years.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Commitments and Contingencies	Note 13. Commitments and Contingencies Lease Commitments As of December 31, 2019, the Company’s leased assets consisted of its office headquarters in Exton, Pennsylvania. Prior to the September 30, 2018 termination date, the Company also leased a facility in Cambridge, Massachusetts. During 2019, 2018 and 2017, rent expense, including real estate taxes, was $0.3 million, $1.7 million, and $2.4 million, respectively. The leases are classified as operating leases. Future minimum commitments as of December 31, 2019 under the Company’s lease agreements are approximately: December 31, Operating Leases (in thousands) 2020 $ 217 2021 224 2022 229 2023 235 2024 240 2025 100 $ 1,245 The Company entered into the Exton, Pennsylvania facility lease on April 1, 2015, which was subsequently amended on September 23, 2015 to include additional space. We currently lease approximately 11,000 square feet of office space at our Exton facility. The lease expires on May 31, 2025 as a result of the Company’s election to exercise its five-year renewal option.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Taxes
Income Taxes	Note 14. Income Taxes In December 2017, the Tax Cuts and Jobs Act (“TCJA”) was signed into law. Among other things, the TCJA permanently lowers the The Company’s preliminary estimate of the TCJA and the remeasurement of its deferred tax assets and liabilities was subject to the finalization of management’s analysis related to certain matters, such as developing interpretations of the provisions of the TCJA, changes to certain estimates and the filing of the Company’s tax returns. The final determination of the TCJA and the remeasurement of the Company’s deferred assets and liabilities was completed during 2018, within one year from the enactment of the TCJA, as additional information became available. There were no changes to management’s analysis of the effects of TCJA originally performed as of December 31, 2017. Certain provisions from the Tax Reform Act of 1986 were not impacted by TCJA, such as those limiting the amount of net operating loss carryforwards (“NOLs”) and tax credit carryforwards that companies may utilize in any one year in the event of changes in ownership, as defined by Section 382 of the Internal Revenue Code. The Company has completed several financings since the effective date of the Tax Reform Act of 1986, which as of December 31, 2019, have resulted in ownership changes that will significantly limit the Company’s ability to utilize its net operating loss and tax credit carryforwards. In December 2017, the Company completed a study which determined that ownership changes had occurred. The federal and state net operating loss and tax credit carryforwards and related deferred tax assets shown in the table below have been adjusted to reflect the limitations that resulted from this study. The Company continues to monitor equity activity and potential ownership changes. As of December 31, 2019, the Company had cumulative federal and state NOLs of approximately $295.8 million and $290.2 million available to reduce federal and state taxable income, respectively. As a result of TCJA, federal net operating losses incurred for taxable years beginning after January 1, 2018 have an unlimited carryforward period, but can only be utilized to offset 80% of taxable income in future taxable periods. Of the $295.8 million of federal NOLs, $98.4 million have an unlimited carryforward and the remaining NOLs are still subject to expiration through 2037. State NOLs are still subject to expiration according to the laws of each respective jurisdiction. The Company files state tax returns in Massachusetts and Pennsylvania whereby both jurisdictions impose a 20-year carryforward period. All $290.2 million of state NOLs expire through 2039, with the first year of expiration being 2032 for $21.0 million of Massachusetts NOLs. In addition, at December 31, 2019, the Company had cumulative federal and state tax credit carryforwards of $21.6 million and $1.9 million, respectively, available to reduce federal and state income taxes, respectively, which expire through 2039 and 2034, respectively, for federal and state purposes. As of December 31, 2019 and 2018, the components of the deferred tax assets are approximately as follows: 2019 2018 (In thousands) Operating loss carryforwards $ 81,403 $ 70,509 Tax credit carryforwards 23,072 18,514 Lease liabilities 308 — Other 7,994 8,627 Total deferred tax assets 112,777 97,650 Right-of-use asset (306) — Valuation allowance (112,471) (97,650) Net deferred tax assets $ — $ — Note 14. Income Taxes (Continued) The Company has provided a full valuation allowance for its deferred tax asset due to the uncertainty surrounding the ability to realize these assets. The difference between the U.S. federal corporate tax rate and the Company’s effective tax rate for the years ended December 31, 2019, 2018 and 2017 is as follows: 2019 2018 2017 Expected federal income tax rate (21.0) % (21.0) % (34.0) % Expiring credits and NOLs — 1.0 — Change in valuation allowance 26.2 37.9 0.9 Federal and state credits (8.1) (7.4) (6.9) State income taxes, net of federal benefit (4.7) (9.7) (3.7) Permanent differences 4.8 0.5 2.4 Rate change related to TCJA — — 41.9 Other 2.8 (1.3) (0.6) Effective tax rate % % % The Company applies ASC 740-10, Accounting for Uncertainty in Income Taxes, an interpretation of ASC 740 . ASC 740-10 clarifies the accounting for uncertainty in income taxes recognized in financial statements and requires the impact of a tax position to be recognized in the financial statements if that position is more likely than not of being sustained by the taxing authority. The Company had no unrecognized tax benefits resulting from uncertain tax positions at December 31, 2019 and 2018. The Company has not conducted a study of its research and development tax credit carryforwards. Such a study might result in an adjustment to the Company’s research and development credit carryforwards, however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position under ASC 740-10. A full valuation allowance has been provided against the Company’s research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the statements of operations and comprehensive loss if an adjustment was required. The Company files income tax returns in the U.S. federal, Massachusetts and Pennsylvania jurisdictions. The Company is no longer subject to tax examinations for years before 2016, except to the extent that it utilizes NOLs or tax credit carryforwards that originated before 2016. The Company does not believe there will be any material changes in its unrecognized tax positions over the next 12 months. The Company has not incurred any interest or penalties. In the event that the Company is assessed interest or penalties at some point in the future, they will be classified in the statements of operations and comprehensive loss as general and administrative expense.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2019
Employee Benefit Plan
Employee Benefit Plan	Note 15. Employee Benefit Plan The Company has an employee benefit plan under Section 401(k) of the Internal Revenue Code. The plan allows employees to make contributions up to a specified percentage of their compensation. Under the plan, the Company matches a portion of the employees’ contributions up to a defined maximum. Prior to August 2018, the Company historically contributed up to 3% of employee base salary, by matching 50% of the first 6% of annual base salary contributed by each employee. Effective August 2018, the Company began contributing up to 5% of employee base salary, by matching 100% of the first 5% of annual base salary contributed by each employee. Approximately $0.3 million, $0.2 million and $0.3 million of 401(k) benefits were charged to operating expenses for the years ended December 31, 2019, 2018 and 2017, respectively.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions
Related Party Transactions	Note 16. 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 December 31, 2019, 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 16% of the Company's outstanding common stock. During 2019, Baker Brothers purchased shares of the Company’s Series B1 Preferred Stock and accompanying warrants to purchase common stock in connection with the 2019 Private Placement, as more fully described in Note 7. Concurrent with the 2019 Private Placement, the Company amended the warrants initially issued to Baker Brothers and other holders on May 7, 2013, September 30, 2013 and February 10, 2014 to remove expiration date. Following the amendment, these warrants will not expire. During 2018, Baker Brothers exercised warrants to purchase 2,700,791 shares of the Company’s common stock at an exercise price of $3.76 per share for a total exercise price of approximately $9.5 million. During 2017, Baker Brothers purchased shares of the Company’s common stock in connection with underwritten public offerings of shares of the Company’s common stock as more fully described in Note 8. As of December 31, 2019, 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, 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 (“Pillar Invest”), which is the general partner of Pillar Pharmaceuticals I, L.P., Pillar Pharmaceuticals II, L.P. (“Pillar II”), Pillar Pharmaceuticals III, L.P. (“Pillar III”), Pillar Pharmaceuticals IV, L.P. (“Pillar IV”) and Pillar Pharmaceuticals V, L.P. (“Pillar V”), Pillar Pharmaceuticals 6 L.P. and Pillar Partners Foundation L.P. (collectively, the “Pillar Investment Entities”). As of December 31, 2019, the Pillar Investment Entities own approximately 11% of the Company's common stock. During 2018, Participations Besancon , an investment fund advised by Pillar Invest having no affiliation with Mr. El Zein, exercised warrants to purchase 150,000 shares of the Company’s common stock at an exercise price of $3.76 per share for a total exercise price of approximately $0.6 million. During 2017, Pillar II exercised 629,257 warrants to purchase shares of the Company’s common stock at a total exercise price of approximately $3.5 million and Besancon exercised 364,752 warrants to purchase shares of the Company’s common stock at a total exercise price of approximately $1.9 million. The warrant exercise prices had been established at the time that the warrants were purchased. Board Fees Paid in Stock Pursuant to the Company’s director compensation program, in lieu of director board and committee fees of approximately $0.1 million incurred during each of the years ended December 31, 2019, 2018 and 2017, respectively, the Company issued 53,985, 13,654, and 7,867 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 Appli

Net Loss per Common Share Applicable to Common Stockholders	12 Months Ended
	Dec. 31, 2019
Net Loss per Common Share Applicable to Common Stockholders
Net Loss per Common Share Applicable to Common Stockholders	Note 17. Net Loss per Common Share Applicable to Common Stockholders Net loss applicable to common stockholders represents net loss adjusted for deemed dividends related to the December 2019 Private Placement, as more fully described in Note 7. Basic and diluted net loss per common share applicable to common stockholders is calculated by dividing net loss applicable to common stockholders by the weighted-average number of shares of common stock outstanding during the period, without consideration of common stock equivalents. The Company’s potentially dilutive securities, which include outstanding stock option awards, unvested restricted stock units, common stock warrants, convertible preferred stock and securities underlying the Future Tranche Rights (see Note 7), are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. For the years ended December 31, 2019, 2018 and 2017, diluted net loss per common share applicable to common stockholders was the same as basic net loss per common share applicable to common stockholders as the effects of the Company’s potential common stock equivalents are antidilutive. Total antidilutive securities that were excluded from the calculation of diluted net loss per share applicable to common stockholders, due to their anti-dilutive effect, were 61,289,079, 6,075,339, and 8,145,188 as of December 31, 2019, 2018 and 2017, respectively. Such antidilutive securities consisted of stock options, unvested restricted stock units, convertible preferred stock, warrants and securities underlying Future Tranche Rights as December 31, 2019, and consisted of stock options, convertible preferred stock and warrants as of December 31, 2018 and 2017.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events
Subsequent Events	Note 18. 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. Proceeds from Sale of Common Stock "At-The-Market" Equity Program During the period January 1, 2020 through March 11, 2020, the Company sold 403,983 shares of its common stock pursuant to the ATM Agreement, as more fully described in Note 8, resulting in net proceeds after deduction of commissions of $0.6 million. Common Stock Purchase Agreement During the period January 1, 2020 through March 11, 2020, the Company sold 450,000 shares of its common pursuant to the LPC Purchase Agreement, as more fully described in Note 8, resulting in net proceeds of $0.8 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, judgements, and assumptions that affect the reported amounts of assets, liabilities, equity, revenues and expenses, and related disclosure of contingencies in the accompanying financial statements and these notes. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable. Actual results could differ materially from those estimates.
Segment Information	Segment Information Operating segments are defined as components of an enterprise in which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and assessing performance. The Company views its operations and manages its business as one operating segment, which is the business of developing novel therapeutics for oncology and rare diseases.
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 December 31, 2019 and 2018, 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 December 31, 2019 and 2018. As of December 31, 2019, the Company did not have any other derivatives, hedging instruments or other similar financial instruments.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents and investments. The Company’s credit risk is managed by investing in highly rated money market instruments, certificates of deposit, corporate bonds, commercial paper and debt securities. Due to these factors, no significant additional credit risk is believed by management to be inherent in the Company’s assets. As of December 31, 2019, all of the Company’s cash and cash equivalents were held at two financial institutions.
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 December 31, 2019 and 2018 consisted of cash and money market funds.
Property and Equipment	Property and Equipment Property and equipment is carried at acquisition cost less accumulated depreciation, subject to review for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable as described further under the heading "Impairment of Long-Lived Assets" below. The cost of normal, recurring, or periodic repairs and maintenance activities related to property and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits. Depreciation and amortization are computed using the straight-line method based on the estimated useful lives of the related assets. Laboratory and other equipment are depreciated over three to five years. Leasehold improvements are amortized over the remaining lease term or the related useful life, if shorter. When an asset is disposed of, the associated cost and accumulated depreciation is removed from the related accounts on the Company's balance sheet with any resulting gain or loss included in the Company's statement of operations.
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 . The Company determines if an arrangement is a lease at inception. Operating leases are included in long-term right-of-use assets and current and long-term lease liabilities within the Company’s balance sheets. Right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The right-of-use assets are tested for impairment according to ASC 360. Leases with an initial term of 12 months or less are not recorded on the balance sheet and are recognized as lease expense on a straight-line basis over the lease term. In December 2019, the Company determined it was reasonably certain that it would exercise its five-year renewal option to extend its Exton, PA office lease, which was scheduled to expired in May 2020. As a result of this determination, the renewal option was included in the lease term and the Company recorded an incremental ROU asset and lease liability of $1.0 million as of December 31, 2019, the date this determination was made. Subsequently, in January 2020, the Company exercised its option to renew and extend the lease term for a period of five years from June 1, 2020 through May 31, 2025.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets In accordance with ASC 360-10-35, Impairment or Disposal of Long-Lived Assets , the Company reviews its long-lived assets and identifiable finite-lived intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable (i.e. impaired). Once an impairment is determined, the actual impairment recognized is the difference between the carrying amount and the fair value (less costs to sell for assets to be disposed of) as estimated using one of the following approaches: income, cost and/or market. Fair value using the income approach is determined primarily using a discounted cash flow model that uses the estimated cash flows associated with the asset or asset group under review, discounted at a rate commensurate with the risk involved. Fair value utilizing the cost approach is determined based on the replacement cost of the asset reduced for, among other things, depreciation and obsolescence. Fair value, utilizing the market approach, benchmarks the fair value against the carrying amount.
Warrant Liability	Note 2. Summary of Significant Accounting Policies (Continued) Warrant Liability The Company accounts for stock warrants as either equity instruments, liabilities or derivative liabilities in accordance with ASC 480, Distinguishing Liabilities from Equity (ASC 480) and/or ASC 815, Derivatives and Hedging (ASC 815), depending on the specific terms of the warrant agreement. Freestanding warrants for shares that are potentially redeemable, whereby the Company may be required to transfer assets (e.g. cash or other assets) outside of its control, are classified as liabilities. Liability-classified warrants are recorded at their estimated fair values at each reporting period until they are exercised, terminated, reclassified or otherwise settled. Changes in the estimated fair value of liability-classified warrants are recorded in Warrant Revaluation Income (Expense) in the Company’s statements of operations and comprehensive loss. Equity classified warrants are recorded within additional paid-in capital at the time of issuance and not subject to remeasurement. For additional discussion on warrants, see Note 8.
Future Tranche Right Liability	Future Tranche Right Liability In connection with the Company’s 2019 Private Placement, as more fully described in Note 7, the Company entered into the December 2019 Securities Purchase Agreement, which 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 a liabilities (“Future Tranche Right Liability”) under ASC 480, which requires the measurement of the fair value of the liability at the time of issuance and recording changes as a charge to current earnings at each reporting period, which is included in Future Tranche Right Liability Revaluation Expense in the Company’s statements of operations and comprehensive loss.
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.
Redeemable Preferred Stock Issued with Other Freestanding Instruments	Redeemable Preferred Stock Issued with Other Freestanding Instruments The Company considers guidance within ASC 470-20, Debt (ASC 470), ASC 480, and ASC 815 when accounting for a redeemable equity instrument issued with other freestanding instruments (e.g. detachable warrants and future tranche right liabilities), such as in the December 2019 Private Placement. In circumstances in which redeemable convertible preferred stock is issued with freestanding liability-classified instruments, the proceeds from the issuance of the convertible preferred stock are first allocated to those instruments at their full estimated fair value. The remaining proceeds, as further reduced by discounts created by the bifurcation of embedded derivatives and/or beneficial conversion features, if any, are allocated to the redeemable equity instrument. See Note 7 for additional discussion on the Company’s accounting for the 2019 Private Placement.
Revenue Recognition	Note 2. Summary of Significant Accounting Policies (Continued) Revenue Recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606’), which applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. In accordance with ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC Topic 606, it performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it determines that it is probable it will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Amounts received prior to satisfying the revenue recognition criteria are recognized as deferred revenue in the Company’s balance sheet. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current portion of deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current portion. Alliance Revenues The Company’s revenues have primarily been generated through collaborative research, development and/or commercialization agreements. The terms of these agreements may include payment to the Company of one or more of the following: nonrefundable, up-front license fees; research, development and commercial milestone payments; and other contingent payments due based on the activities of the counterparty or the reimbursement by licensees of costs associated with patent maintenance. Each of these types of revenue are recorded as Alliance revenues in the Company’s statements of operations. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Note 2. Summary of Significant Accounting Policies (Continued) See Note 10, “Collaboration and License Agreements” for additional details regarding the Company’s collaboration arrangements. As part of the accounting for these arrangements, the Company allocates the transaction price to each performance obligation on a relative stand-alone selling price basis. The stand-alone selling price may be, but is not presumed to be, the contract price. In determining the allocation, the Company maximizes the use of observable inputs. When the stand-alone selling price of a good or service is not directly observable, the Company estimates the stand-alone selling price for each performance obligation using assumptions that require judgment. Acceptable estimation methods include, but are not limited to: (i) the adjusted market assessment approach, (ii) the expected cost plus margin approach, and (iii) the residual approach (when the stand-alone selling price is not directly observable and is either highly variable or uncertain). In order for the residual approach to be used, the Company must demonstrate that (a) there are observable stand-alone selling prices for one or more of the performance obligations and (b) one of the two criteria in ASC 606-10-32-34(c)(1) and (2) is met. The residual approach cannot be used if it would result in a stand-alone selling price of zero for a performance obligation as a performance obligation, by definition, has value on a stand-alone basis. An option in a contract to acquire additional goods or services gives rise to a performance obligation only if the option provides a material right to the customer that it would not receive without entering into that contract. Factors that the Company considers in evaluating whether an option represents a material right include, but are not limited to: (i) the overall objective of the arrangement, (ii) the benefit the collaborator might obtain from the arrangement without exercising the option, (iii) the cost to exercise the option (e.g. priced at a significant and incremental discount) and (iv) the likelihood that the option will be exercised. With respect to options determined to be performance obligations, the Company recognizes revenue when those future goods or services are transferred or when the options expire. The Company’s revenue arrangements may include the following: Up-front License Fees: If a license is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of an agreement that includes research and development milestone payments, the Company evaluates whether each milestone is considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect Alliance revenues and earnings in the period of adjustment. Research and Development Activities: If the Company is entitled to reimbursement from its collaborators for specified research and development activities or the reimbursement of costs associated with patent maintenance, the Company determines whether such funding would result in Alliance revenues or an offset to research and development expenses. Reimbursement of patent maintenance costs are recognized during the period in which the related expenses are incurred as Alliance revenues in the Company’s statements of operations. Note 2. Summary of Significant Accounting Policies (Continued) Royalties: If the Company is entitled to receive sales-based royalties from its collaborator, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, provided the reported sales are reliably measurable, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its collaboration and license arrangements. Manufacturing Supply and Research Services: Arrangements that include a promise for future supply of drug substance, drug product or research services at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the licensee exercises these options, any additional payments are recorded in Alliance revenues when the licensee obtains control of the goods, which is upon delivery, or as the services are performed. The Company receives payments from its licensees based on schedules established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensees and the transfer of the promised goods or services to the licensees will be one year or less.
Research and Development Expenses	Research and Development Expenses All research and development expenses are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including drug development trials and studies, drug manufacturing, laboratory supplies, external research, payroll including stock-based compensation and overhead. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. The capitalized amounts are expensed as the related goods are accepted by the Company or the services are performed. As of December 31, 2019 and 2018, the Company recorded approximately $2.8 million and $0.6 million as prepaid research and development, respectively, which is included within prepaid expenses and other current assets in the accompanying balance sheets.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation using ASC 718, Compensation – Stock Compensation (“ASC 718”), or ASC 505-50, Equity – Equity Based Payments to Non-Employees , as applicable. The Company accounts for stock-based awards to employees and non-employee directors using the fair value based method to determine compensation expense for all arrangements where shares of stock or equity instruments are issued for compensation. In addition, the Company accounts for stock-based compensation to other non-employees in accordance with the accounting guidance for equity instruments that are issued to entities or persons other than employees. The Company recognizes all share-based payments to employees and directors as expense in the statements of operations and comprehensive loss based on their fair values. The Company records compensation expense on a straight-line basis over an award’s requisite service period, or vesting period, based on the award’s fair value at the date of grant. Vesting is generally four years for employees and one year for directors. The Company uses a Black-Scholes option-pricing model to determine the fair value of each option grant as of the date of grant for expense incurred. The Black-Scholes option pricing model requires inputs for risk-free interest rate, dividend yield, expected stock price volatility and expected term of the options. See Note 12, “Stock-based Compensation” for additional details. Note 2. Summary of Significant Accounting Policies (Continued) Prior to the adoption of Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), ASC 718 required forfeitures to be estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differed from those estimates. However, ASU 2016-09 allows an entity to elect as an accounting policy upon adoption either to continue to estimate the total number of awards for which the requisite service period will not be rendered or to account for forfeitures when they occur. In connection with the adoption of this ASU in the first quarter of 2017, the Company made an accounting policy election to account for forfeitures as they occur and applied this change in accounting policy on a modified retrospective basis, resulting in less than a $0.1 million reduction in Additional paid-in capital and an increase in Accumulated deficit as of January 1, 2017, to reflect the cumulative effect of previously estimated forfeitures. See the caption “ Cumulative effect from adoption of new accounting standard” within the accompanying statements of redeemable preferred stock and stockholders’ equity (deficit).
Merger-related Costs, net	Merger-related Costs, net On January 21, 2018, the Company, BioCryst Pharmaceuticals, Inc., a Delaware corporation (“BioCryst”), Nautilus Holdco, Inc., a Delaware corporation and a direct, wholly owned subsidiary of BioCryst (“Holdco”), Island Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Holdco, and Boat Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Holdco, entered into an Agreement and Plan of Merger (the “Merger Agreement”). The board of directors of each of Idera and BioCryst unanimously approved the Merger Agreement and the transactions contemplated thereby and the required regulatory approvals were received. However, the proposed merger was subject to approval by the stockholders of Idera and BioCryst, and satisfaction of other customary closing conditions, as specified in the Merger Agreement. At a special meeting of BioCryst stockholders held on July 10, 2018, BioCryst’s stockholders voted against the adoption of the Merger Agreement. Following such vote and in accordance with the terms of the Merger Agreement, BioCryst terminated the Merger Agreement. In accordance with the Merger Agreement, BioCryst paid the Company a fixed expense reimbursement amount of $6 million in July 2018 in connection with the termination of the Merger Agreement. The fixed expense reimbursement amount is included in “Merger-related costs, net” in the accompanying statements of operations. Merger-related costs, net includes amounts related to the transactions contemplated under the Merger Agreement, including charges incurred for transaction and integration-related professional fees, employee retention costs, and other incremental costs directly related to the potential merger; less the $6 million fixed expense reimbursement termination fee, which was received by the Company in July 2018.
Restructuring Costs	Restructuring Costs Restructuring charges are primarily comprised of severance costs related to workforce reductions, contract termination and wind-down costs and asset impairments. In accordance with ASC 420, Exit or Disposal Cost Obligations , the Company recognizes restructuring charges when the liability has been incurred, except for one-time employee termination benefits that are incurred over time. Generally, one-time employee termination benefits (i.e. severance costs) are accrued at the date management has committed to a plan of termination and employees have been notified of their termination dates and expected severance payments. Other costs will be recorded as incurred. Asset impairment charges have been, and will be, recognized when management has concluded that the assets have been impaired in accordance with ASC 360-10-35, Impairment or Disposal of Long-Lived Assets , or other applicable authoritative guidance. See Note 11 for additional details.
Income Taxes	Income Taxes An asset and liability approach is used for financial accounting and reporting for income taxes. Deferred income taxes arise from temporary differences between income tax and financial reporting and principally relate to recognition of revenue and expenses in different periods for financial and tax accounting purposes and are measured using currently enacted tax rates and laws. In addition, a deferred tax asset can be generated by a net operating loss carryover. If it is more likely than not that some portion or all of a deferred tax asset will not be realized, a valuation allowance is recognized. Note 2. Summary of Significant Accounting Policies (Continued) In the event the Company is charged interest or penalties related to income tax matters, the Company would record such interest as interest expense and would record such penalties as other expense in the Statements of Operations. No such charges have been incurred by the Company. For each of the years ended December 31, 2019, 2018 and 2017, the Company had no uncertain tax positions. See Note 14, “Income Taxes” for additional details.
Net Loss per Common Share applicable to Common Stockholders	Net Loss per Common Share applicable to Common Stockholders Basic and diluted net loss per common share applicable to common stockholders is computed using the weighted average number of shares of common stock outstanding during the period. The diluted loss per share calculation gives effect to dilutive stock options, warrants, convertible preferred stock and other potentially dilutive common stock equivalents outstanding during the period. Diluted loss per share is based on the if-converted method or the treasury stock method, as applicable, and includes the effect from the potential issuance of common stock, such as shares issuable pursuant to the conversion of convertible preferred stock and the exercise of stock options and warrants, assuming the exercise of all “in-the-money” common stock equivalents based on the average market price during the period. Common stock equivalents have been excluded where their inclusion would be anti-dilutive. Diluted net loss per common share applicable to common stockholders is the same as basic net loss per common share applicable to common stockholders for each of the three years in the period ended December 31, 2019 as the effects of the Company’s potential common stock equivalents are antidilutive (see Note 17).
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive income (loss) for the years ended December 31, 2019, 2018 and 2017 is comprised of reported net income (loss) and any change in net unrealized gains and losses on investments in available-for-sale securities during each year, which is included in “Accumulated other comprehensive income” on the accompanying balance sheets. In accordance with ASC Topic 220, Comprehensive Income , the Company has elected to present the components of net income and other comprehensive income as one continuous statement.
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”). ASU 2016-02 requires organizations that lease assets, with lease terms of more than 12 months, to recognize on the balance sheet the assets and liabilities for the rights and obligations created by those leases. Consistent with GAAP, the recognition, measurement and presentation of expenses and cash flows arising from a lease by a lessee will depend primarily on its classification as a finance or operating lease. However, unlike the previous standard, which required only capital leases to be recognized on the balance sheet, ASU 2016-02 requires both types of leases to be recognized on the balance sheet. This guidance was applicable to the Company's fiscal year beginning January 1, 2019, and the Company adopted ASU 2016-02 in the first quarter of 2019 using the alternative modified retrospective transition method, which allowed the Company to apply the new lease standard to the beginning of the 2019 period and did not require adjusting comparative period financial information. Additionally, the Company elected the package of practical expedients to not reassess prior conclusions related to contracts containing leases, lease classification and initial direct costs. As a result of adopting ASU 2016-02, the primary impact on the Company’s financial statements was the recognition of a right-of-use asset and corresponding liability of approximately $0.3 million on its balance sheet as of January 1, 2019 related to its existing Exton, PA facility operating lease. In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718) (“ASU 2018-07”). ASU 2018-07 simplifies the accounting for nonemployee share-based payment transactions and was adopted by the Company in the first quarter of 2019. The adoption of this ASU did not have a material impact on the Company’s financial statements. Recently Issued (Not Yet Adopted) Accounting Pronouncements In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard will be effective for the Company on January 1, 2020. The Company is currently evaluating the potential impact that this standard may have on our financial position and results of operations but does not expect the impact of this standard to be material. In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which amends ASC 820, Fair Value Measurement . ASU 2018-13 modifies the disclosure requirements for fair value measurements by removing, modifying, or adding certain disclosures. The ASU is effective for annual periods, including interim periods within those annual periods, beginning after December 15, 2019, with early adoption permitted for removed or modified disclosures, and delayed adoption of the additional disclosures until their effective date. The Company is currently evaluating the effect that the ASU will have on its financial statements and related disclosures but does not expect the impact of this amendment to be material.
Accounting for Uncertainty in Income Taxes	The Company applies ASC 740-10, Accounting for Uncertainty in Income Taxes, an interpretation of ASC 740 . ASC 740-10 clarifies the accounting for uncertainty in income taxes recognized in financial statements and requires the impact of a tax position to be recognized in the financial statements if that position is more likely than not of being sustained by the taxing authority. The Company had no unrecognized tax benefits resulting from uncertain tax positions at December 31, 2019 and 2018.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Schedule of assets and liabilities measured and recorded in financial statements at fair value on a recurring basis	December 31, 2019 (In thousands) Total Level 1 Level 2 Level 3 Assets Cash $ 250 $ 250 $ — $ — 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 December 31, 2018 (In thousands) Total Level 1 Level 2 Level 3 Assets Cash $ 8,446 $ 8,446 $ — $ — Money market funds 61,177 61,177 — — Other cash equivalents – commercial paper 1,808 — 1,808 — Total assets $ 71,431 $ 69,623 $ 1,808 $ — Total liabilities $ — $ — $ — $ —
Schedule of reconciliation measured at fair value on a recurring basis using unobservable inputs	Warrant Derivative (In thousands) Liability Liability Balance at December 31, 2018 $ — $ — Issuance of redeemable preferred stock and warrants (1) 2,643 35,472 Change in the fair value of liability 598 10,964 Balance at December 31, 2019 $ 3,241 $ 46,436 (1) Represents fair value of freestanding warrants and the future tranche right related to the December 2019 Private Placement on the issuance date .
Warrant liability
Schedule of assumptions used in determining fair value	December 23, December 31, 2019 2019 Risk-free interest rate Expected dividend yield — — Expected term (years) 7.00 6.98 Expected volatility Exercise price (per share) $ 1.52 $ 1.52
Future tranche right liability
Schedule of assumptions used in determining fair value	December 23, December 31, 2019 2019 Risk-free interest rate for warrants Risk-free interest rate for preferred stock 1.86% - 1.89% 1.84% - 1.88% Expected dividend yield — — Expected term (years) of call option on preferred stock 1.18 - 2.18 1.16 - 2.16 Expected term (years) of warrants 8.18 - 9.18 8.16 - 9.16 Expected volatility 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)	12 Months Ended
	Dec. 31, 2019
Investments
Schedule of available-for-sale investments at fair value	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 Total investments $ 2,774 $ — $ — $ 2,774

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property and Equipment
Schedule of net property and equipment at cost	December 31, December 31, (In thousands) 2019 2018 Leasehold improvements $ 107 $ 104 Equipment and other 764 767 Total property and equipment, at cost 871 871 Less: Accumulated depreciation and amortization 774 664 Property and equipment, net $ 97 $ 207

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Accrued Expenses
Schedule of accrued expenses	December 31, December 31, (In thousands) 2019 2018 Payroll and related costs $ 2,179 $ 1,962 Clinical and nonclinical trial expenses 4,199 3,958 Professional and consulting fees 859 605 Restructuring expenses 113 1,147 Other 111 212 Total accrued expenses $ 7,461 $ 7,884

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2019
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 $ $ 15,000,120 Tranche 3 (Series B3) (2) 82,418 $ 15,000,076 Tranche 4 (Series B4) (2) 82,418 $ 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)	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity
Schedule of warrants outstanding and exercisable for purchase of common stock	Number of Shares December 31, December 31, Weighted-Average Description 2019 2018 Exercise Price Expiration Date Liability-classified Warrants December 2019 Series B1 warrants (1) 2,368,400 — $ 1.52 Dec 2026 2,368,400 — Equity-classified Warrants May 2013 warrants 1,949,754 1,977,041 $ 0.08 None (2) September 2013 warrants 514,756 521,997 $ 0.08 None (2) February 2014 warrants 266,006 269,844 $ 0.08 None (2) 2,730,516 2,768,882 Total outstanding 5,098,916 2,768,882 (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. (2) In connection with December 2019 Private Placement, the expiration date on these warrants was amended to be indefinite.
Summary of warrant activity	Number of Weighted-Average Warrants Exercise Price Outstanding at December 31, 2018 2,768,882 $ 0.08 Issued (1) 2,368,400 1.52 Exercised (38,366) 0.08 Expired — — Outstanding at December 31, 2019 5,098,916 $ 0.75 (1) During the year ended December 31, 2019, certain related parties were issued warrants as more fully described in Note 16.

Alliance Revenue (Tables)

Alliance Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Alliance Revenue
Schedule of accompanying statements of operations and comprehensive loss	(In thousands) 2019 2018 2017 Out-license arrangement (1) $ 1,447 $ — $ — GSK collaboration (2) — 517 863 Vivelix collaboration (3) — 56 14 Other (4) 1 89 25 Total Alliance revenue $ 1,448 $ 662 $ 902 (1) For the year ended December 31, 2019, the Company recognized Alliance revenues of $1.4 million under the Licensee Agreement, as more fully described in Note 10, primarily related to the transfer of the IMO-8400 License and IMO-8400 drug product. (2) For the years ended December 31, 2018 and 2017, revenue recognized primarily relates to the amortization of the $2.5 million upfront, non-refundable, non-creditable cash payment received upon the execution of the GSK Agreement, as more fully described in Note 10, which was recognized as revenue on a straight-line basis over the estimated 36-month research plan period, which approximated the timing in which performance obligations were satisfied. No such revenue was recognized during 2019. Revenue recognized for the year ended December 31, 2017 also includes an additional $0.1 million related to additional research services performed in connection with the GSK Agreement. (3) For each of the years ended December 31, 2018 and 2017, revenue recognized relates to reimbursements for research services performed in connection with the Vivelix Agreement, as more fully described in Note 10. (4) For all periods presented, revenue recognized relates to collaborations which are not material to the Company’s current operations nor expected to be material in the future, including reimbursements by licensees of costs associated with patent maintenance.

Restructuring Costs (Tables)

Restructuring Costs (Tables)	12 Months Ended
	Dec. 31, 2019
Restructuring Costs
Schedule of restructuring costs	(in thousands) Employee Severance Contract Termination Costs Asset Impairments Total Accrued restructuring balance as of December 31, 2017 $ — $ — $ — $ — Charges incurred (1) 2,635 225 674 3,534 Cash payments (1,380) (225) — (1,605) Non-cash settlements (24) — (674) (698) Adjustments (84) — — (84) Accrued restructuring balance as of December 31, 2018 $ 1,147 $ — $ — $ 1,147 Charges incurred 181 — — 181 Cash payments (1,215) — — (1,215) Accrued restructuring balance as of December 31, 2019 $ 113 $ — $ — $ 113 (1) Excludes $0.4 million gain due to the write-off of the remaining deferred rent liability associated with the termination of the Cambridge, Massachusetts facility lease.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Stock-Based Compensation
Schedule of stock-based compensation expense attributable to share-based payments made to employees and directors and included in operating expenses	(in thousands) 2019 2018 2017 Stock-based compensation: Research and development Employee Stock Purchase Plans $ 36 $ 71 $ 96 Equity Incentive Plans (1) 1,312 1,780 6,398 $ 1,348 $ 1,851 $ 6,494 General and administrative Employee Stock Purchase Plans $ 20 $ 48 $ 63 Equity Incentive Plans 2,477 3,751 4,163 $ 2,497 $ 3,799 $ 4,226 Restructuring costs Equity Incentive Plans $ — $ 24 $ — $ — $ 24 $ — Total stock-based compensation expense $ 3,845 $ 5,674 $ 10,720 (1) The 2017 charge includes approximately $4.3 million of additional stock-based compensation recognized as a result of modifications to previously issued stock option awards in connection with the resignation of an executive.
Schedule of weighted average assumptions applied to options	2019 2018 2017 Average risk-free interest rate Expected dividend yield — — — Expected lives (years) 3.7 3.7 4.0 Expected volatility Weighted average exercise price (per share) $ 2.75 $ 12.63 $ 12.96
Schedule of information related to outstanding and exercisable options	($ in thousands, except per share data) Stock Weighted-Average Weighted-Average Aggregate Outstanding at December 31, 2018 3,304,531 $ 18.41 6.6 $ Granted 1,279,016 2.75 Exercised — — Forfeited (143,874) 12.95 Expired (219,256) 31.29 Outstanding at December 31, 2019 (1) 4,220,417 $ 13.08 6.6 $ — Exercisable at December 31, 2019 2,292,157 $ 19.20 4.7 $ — (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 Nonvested shares at December 31, 2018 — $ — Granted 194,550 3.14 Cancelled (925) 3.14 Vested — — Nonvested shares at December 31, 2019 193,625 $ 3.14

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies
Schedule of future minimum commitments under company lease agreements	December 31, Operating Leases (in thousands) 2020 $ 217 2021 224 2022 229 2023 235 2024 240 2025 100 $ 1,245

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Taxes
Schedule of components of deferred tax assets	2019 2018 (In thousands) Operating loss carryforwards $ 81,403 $ 70,509 Tax credit carryforwards 23,072 18,514 Lease liabilities 308 — Other 7,994 8,627 Total deferred tax assets 112,777 97,650 Right-of-use asset (306) — Valuation allowance (112,471) (97,650) Net deferred tax assets $ — $ —
Schedule of difference between U.S. federal corporate tax rate and Company effective tax rate	2019 2018 2017 Expected federal income tax rate (21.0) % (21.0) % (34.0) % Expiring credits and NOLs — 1.0 — Change in valuation allowance 26.2 37.9 0.9 Federal and state credits (8.1) (7.4) (6.9) State income taxes, net of federal benefit (4.7) (9.7) (3.7) Permanent differences 4.8 0.5 2.4 Rate change related to TCJA — — 41.9 Other 2.8 (1.3) (0.6) Effective tax rate % % %

Business and Organization (Deta

Business and Organization (Details) $ in Thousands	Jul. 27, 2018	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Business and Organization
Accumulated deficit		$ 720,890	$ 664,375
Cash, cash equivalents and investments		42,800
Contingently refundable option fee received in connection with Private Placement		$ 6,200
Reverse stock split conversion ratio	0.125

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	1 Months Ended		12 Months Ended
	Dec. 31, 2019USD ($)	Jul. 31, 2018USD ($)	Dec. 31, 2019USD ($)segmentInstitution	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Accounting Policies
Number of operating segments | segment			1
Number of financial institutions | Institution			2
Operating lease right-of-use asset	$ 1,054		$ 1,054
Operating lease liability, net of current portion	899		899
Charges incurred			0
Uncertain tax positions	0		0		$ 0	$ 0
Prepaid expenses research and development	$ 2,800		$ 2,800		$ 600
Practical Expedient, Financing Component			true
Employees
Accounting Policies
Stock options, vesting period			4 years
Board of Director
Accounting Policies
Stock options, vesting period			1 year
Minimum
Accounting Policies
Equipment depreciation period			3 years
Maximum
Accounting Policies
Equipment depreciation period			5 years
BioCryst
Accounting Policies
Fixed expense reimbursement		$ 6,000
Exton Facility
Accounting Policies
Term of lease commitment (years)	5 years		5 years
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Operating lease right-of-use asset				$ 300

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Feb. 29, 2016	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle
Lease, Practical Expedients, Package [true false]	true
Operating lease right-of-use asset			$ 1,054
Minimum
New Accounting Pronouncements or Change in Accounting Principle
Lease term		12 months
Exton Facility
New Accounting Pronouncements or Change in Accounting Principle
Operating lease right-of-use asset	$ 300
Operating lease liability	$ 300

Fair Value Measurements - Trans

Fair Value Measurements - Transfers Between Levels (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Measurements
Fair value of assets transfers from level 1 to level 2	$ 0	$ 0	$ 0
Fair value of assets transfers from level 2 to level 1	0	0	0
Fair value of liabilities transfers from level 1 to level 2	0	0	0
Fair value of liabilities transfers from level 2 to level 1	0	0	0
Fair value of assets transfers into level 3	0	0	0
Fair value of assets transfers out of level 3	0	0	0
Fair value of liabilities transfers into level 3	0	0	0
Fair value of liabilities transfers out of level 3	$ 0	$ 0	$ 0

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Other cash equivalents and Short-term investments	$ 2,774
Fair value on a recurring basis
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Total Assets	42,793	$ 71,431
Total Liabilities	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	3,241
Issuance of redeemable preferred stock and warrants	2,643
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	46,436
Issuance of redeemable preferred stock and warrants	35,472
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	8,446
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	39,769	61,177
Fair value on a recurring basis | Other cash equivalents – commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Other cash equivalents and Short-term investments		1,808
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
Other cash equivalents and Short-term investments	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	40,019	69,623
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	8,446
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	39,769	61,177
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	2,774	1,808
Significant Other Observable Inputs (Level 2) | Fair value on a recurring basis | Other cash equivalents – commercial paper
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Other cash equivalents and Short-term investments		$ 1,808
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
Other cash equivalents and Short-term investments	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	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	3,241
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	$ 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	12 Months Ended
	Dec. 31, 2019USD ($)
Warrant liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Issuance of redeemable preferred stock and warrants	$ 2,643
Change in the fair value of liability	598
Ending balance	3,241
Future tranche right liability
Fair Value of Assets and Liabilities Measured at Fair Value on a Recurring Basis
Issuance of redeemable preferred stock and warrants	35,472
Change in the fair value of liability	10,964
Ending balance	$ 46,436

Fair Value Measurements - Weigh

Fair Value Measurements - Weighted-average assumptions (Details)	Dec. 31, 2019$ / shares	Dec. 23, 2019$ / shares
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.0179	0.0182
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.0698	0.0700
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.80	0.80
Exercise price
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.5200	1.5200

Fair Value Measurements - Futur

Fair Value Measurements - Future Tranche Rights (Details)	Dec. 31, 2019$ / shares	Dec. 23, 2019$ / shares
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.0179	0.0182
Risk-free interest rate | Warrants
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.82	1.82
Risk-free interest rate | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.84	1.86
Risk-free interest rate | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.88	1.89
Expected term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.0698	0.0700
Expected term | Warrants | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	8.16	8.18
Expected term | Warrants | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	9.16	9.18
Expected term | Preferred stock | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	1.16	1.18
Expected term | Preferred stock | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	2.16	2.18
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Debt instrument measurement input	0.80	0.80
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	1.5200	1.5200
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

Investments - Summary of Availa

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

Investments - Additional Inform

Investments - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Investments
Realized gains or losses	$ 0
Losses or other-than-temporary declines	$ 0

Property and Equipment - Net Pr

Property and Equipment - Net Property and Equipment at Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment
Total property and equipment, at cost	$ 871	$ 871
Less: accumulated depreciation and amortization	774	664
Property and equipment, net	97	207
Leasehold improvements
Property, Plant and Equipment
Total property and equipment, at cost	107	104
Laboratory equipment and other
Property, Plant and Equipment
Total property and equipment, at cost	$ 764	$ 767

Property and Equipment - Deprec

Property and Equipment - Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Depreciation and amortization expense on property and equipment	$ 0.1	$ 0.4	$ 0.7
Fixed asset impairments	$ 0	$ 0.5	$ 0

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses
Payroll and related costs	$ 2,179	$ 1,962
Clinical and nonclinical trial expenses	4,199	3,958
Professional and consulting fees	859	605
Restructuring expenses	113	1,147
Other	111	212
Total accrued expenses	$ 7,461	7,884
Salary continuation severance benefits		$ 700

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock (Details) - USD ($)	Dec. 23, 2019	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity
Warrant exercise price (per share)		$ 0.75	$ 0.08
Aggregate gross proceeds	$ 3,900,000	$ 10,072,000
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
Baker Bros. Advisors LP
Temporary Equity
Warrant exercise price (per share)			$ 3.76
Deemed Dividend	28,000,000
Preferred Stock Warrant
Temporary Equity
Preferred Shares		263,521
Aggregate Purchase Price		$ 45,000,272
Series B1 Warrants
Temporary Equity
Gross proceeds received	10,100,000
Estimated fair values	2,600,000
Future Tranche Rights
Temporary Equity
Estimated fair values	$ 35,500,000
Series B1 redeemable convertible preferred stock (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively
Temporary Equity
Sale of redeemable convertible preferred stock	23,684	23,684,000
Series B1 redeemable convertible preferred stock (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively | Common Stock Warrant
Temporary Equity
Warrant to purchase common stock	2,368,400
Warrant exercise price (per share)	$ 1.52
Series B1 redeemable convertible preferred stock (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively | 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
Expiration period	9 months
Series B2 Redeemable Convertible Preferred Stock | Common Stock Warrant
Temporary Equity
Warrant to purchase common 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
Preferred Shares		98,685
Share Price		$ 152
Aggregate Purchase Price		$ 15,000,120
Series B3 Redeemable Convertible Preferred Stock
Temporary Equity
Expiration period	15 months
Series B3 Redeemable Convertible Preferred Stock | Common Stock Warrant
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
Preferred Shares		82,418
Share Price		$ 182
Aggregate Purchase Price		$ 15,000,076
Series B4 Redeemable Convertible Preferred Stock
Temporary Equity
Expiration period	21 months
Series B4 Redeemable Convertible Preferred Stock | Preferred Stock Warrant
Temporary Equity
Preferred Shares		82,418
Share Price		$ 182
Aggregate Purchase Price		$ 15,000,076

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred Stock (Details)	12 Months Ended
	Dec. 31, 2019item$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock
Preferred stock, calendar days | item	180
Average Trading volume days | item	50
Preferred stock, shares issued	500,000
Series A convertible preferred stock; Designated — 1,500 shares, Issued and outstanding — 1 share
Class of Stock
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value | $ / shares	$ 0.01	$ 0.01
Preferred stock, shares designated	1,500,000	1,500,000
Annual percentage of dividend of preferred stock	1.00%
Preferred stock, shares outstanding	1,000	1,000
Series A preferred stock liquidation preference per share | $ / shares	$ 1
Series A Preferred stock conversion price per share | $ / shares	$ 272
Preferred stock, shares issued	1,000	1,000
Series B1 redeemable convertible preferred stock (Note 7); Designated — 278 shares, Issued and outstanding — 24 and 0 shares at December 31, 2019 and December 31, 2018, respectively
Class of Stock
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value | $ / shares	$ 0.01	$ 0.01
Preferred stock, shares designated	277,921	278,000
Preferred stock, shares outstanding	24,000	0
Preferred stock redemption price per share | $ / shares	$ 152
Preferred stock conversion price | $ / shares	$ 1.52
Preferred stock, shares issued	24,000	0
Series B2 Redeemable Convertible Preferred Stock
Class of Stock
Preferred stock, shares designated	98,685
Preferred stock redemption price per share | $ / shares	$ 152
Preferred stock conversion price | $ / shares	$ 1.52
Series B3 Redeemable Convertible Preferred Stock
Class of Stock
Preferred stock, shares designated	82,814
Preferred stock, shares outstanding	0
Preferred stock redemption price per share | $ / shares	$ 182
Preferred stock conversion price | $ / shares	$ 1.82
Series B4 Redeemable Convertible Preferred Stock
Class of Stock
Preferred stock, shares designated	82,814
Preferred stock, shares outstanding	4
Preferred stock redemption price per share | $ / shares	$ 182
Preferred stock conversion price | $ / shares	$ 1.82

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock (Details) $ / shares in Units, $ in Millions	Mar. 04, 2019USD ($)$ / sharesshares	Nov. 01, 2017USD ($)shares	Oct. 30, 2017USD ($)person$ / sharesshares	May 05, 1998$ / sharesshares	Nov. 30, 2018USD ($)	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Stock
Stock issued (in shares)						1,535,848
Net proceeds from offering of common stock | $						$ 3.7
Common stock, shares reserved for future issuance						25,066,074
Common stock, par value | $ / shares						$ 0.001	$ 0.001
"At-The-Market" Equity Program
Class of Stock
Stock issued (in shares)						532,700	0
Percentage of fixed commission expense of gross proceeds of shares sold in ATM agreement					3.00%
Gross proceeds from offering of common stock | $						$ 1.6
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
Stock issued (in shares)	269,749
Stock issued (per share) | $ / shares	$ 2.84
Common Stock
Class of Stock
Stock issued (in shares)		625,000	4,166,666	149,960
Sale price of common shares subject to the liquidation put | $ / shares				$ 128
Minimum closing sales price of common stock to issue termination notice to put holders | $ / shares						$ 256
Price exceeds on number of days						20 days
Liquidation put shares no longer held by original holders						49,993
Shares held by put holders						4,472
Put Rights outstanding						0
Remaining shares of common stock subject to the liquidation put						95,494
Net proceeds from offering of common stock | $		$ 53.7
Number of days underwriters have to purchase additional shares		30 days
Stock price (in dollars per share) | $ / shares			$ 12
Gross proceeds from offering of common stock | $			$ 50
Common Stock | "At-The-Market" Equity Program
Class of Stock
Net proceeds from offering of common stock | $					$ 50
Baker Bros. Advisors LP | Common Stock
Class of Stock
Stock issued (in shares)			1,000,000
Number of people | person			2

Stockholders' Equity - Reverse

Stockholders' Equity - Reverse Stock Split (Details)	Jul. 27, 2018shares	Jun. 20, 2018shares	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018$ / sharesshares
Class of Warrant or Right
Common stock, shares authorized		280,000,000	70,000,000	70,000,000
Reverse stock split conversion ratio	0.125
Multiplier used for the reverse stock split ratio		2
Number of shares to be exchange in the reverse stock split	8
Number of shares received in the reverse stock split	1
Common stock, par value | $ / shares			$ 0.001	$ 0.001
Minimum
Class of Warrant or Right
Reverse stock split conversion ratio		0.25
Maximum
Class of Warrant or Right
Reverse stock split conversion ratio		0.125

Stockholders' Equity - Common_2

Stockholders' Equity - Common Stock Warrants (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right
Number of Warrants	5,098,916	2,768,882
Warrant exercise price per share	$ 0.75	$ 0.08
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
December 2019 Series B1 warrants
Class of Warrant or Right
Number of Warrants	2,368,400
Warrant exercise price per share	$ 1.52
Equity Classified Warrants
Class of Warrant or Right
Number of Warrants	2,730,516	2,768,882
May 2013 Warrants
Class of Warrant or Right
Number of Warrants	1,949,754	1,977,041
Warrant exercise price per share	$ 0.08	$ 0.08
September 2013 Warrants
Class of Warrant or Right
Number of Warrants	514,756	521,997
Warrant exercise price per share	$ 0.08	$ 0.08
February 2014 Warrants
Class of Warrant or Right
Number of Warrants	266,006	269,844
Warrant exercise price per share	$ 0.08	$ 0.08

Stockholders' Equity - Common_3

Stockholders' Equity - Common Stock Warrant Activity (Details)	12 Months Ended
	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018$ / shares
Class of Warrant or Right
Outstanding warrants, beginning of period	2,768,882
Exercised	(38,366)
Outstanding warrants, end of period	5,098,916
Warrant exercise price (per share) | $ / shares	$ 0.75	$ 0.08
Warrant exercise price per share, expired | $ / shares	0.08
Expiration Date - November 2017
Class of Warrant or Right
Issued	2,368,400
Warrant exercise price (per share) | $ / shares	$ 1.52

Alliance Revenue (Details)

Alliance Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Alliance Revenue
Alliance revenue	$ 1,448	$ 662	$ 902
Deferred revenue recognized during the period		600	700
Out-license arrangement
Alliance Revenue
Alliance revenue	1,447
Gsk Collaboration
Alliance Revenue
Alliance revenue		517	863
Upfront payment received under collaboration agreement		$ 2,500	$ 2,500
Deferred revenue recognition period		36 months	36 months
Deferred revenue recognized during the period	0
Vivelix Collaboration
Alliance Revenue
Alliance revenue		$ 56	$ 14
Other
Alliance Revenue
Alliance revenue	$ 1	$ 89	25
Additional Research Services | Gsk Collaboration
Alliance Revenue
Deferred revenue recognized during the period			$ 100

Collaboration and License Agr_2

Collaboration and License Agreements (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Apr. 30, 2019USD ($)	Nov. 30, 2016USD ($)director	Nov. 30, 2015USD ($)person	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Alliance revenue				$ 1,448	$ 662	$ 902
Terminate agreement in days				90 days
Number of board director seats held | director		2
Total number of board of director seats | director		7
Deferred revenue recognized during the period					600	700
Operating expenses				$ 47,515	61,618	67,369
Baker Bros. Advisors LP
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Common stock ownership percentage under the collaboration agreement		7.00%
Option and License Agreement with Licensee
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Transaction price				1,400
Performance obligation				$ 0
Percentage of shares acquired	10.00%			10.00%
Option and License Agreement with Licensee | Other Assets
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Equity Securities without Readily Determinable Fair Value, Amount				$ 100
Abbott Molecular
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Operating expenses				$ 0	$ 400	$ 800
Vivelix
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Number of board director seats held | director		2
Total number of board of director seats | director		4
Vivelix | Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement		$ 15,000
GSK Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Number of development candidates | person			1
Number of optional additional targets | person			2
Research period			2 years
GSK Agreement | Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement			$ 2,500
GSK Agreement | License, Research, Clinical Development and Commercialization
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments			100,000
GSK Agreement | Research and Development Plans and Designation of Development Candidates
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments			9,000
GSK Agreement | Clinical and Commercial Milestones
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Milestone payments			$ 89,000
IMO-9200 License | Option and License Agreement with Licensee
Collaborative Arrangements and Non-collaborative Arrangement Transactions
Upfront payment received under collaboration agreement	$ 1,400
Non-refundable fee upon exercise of option	$ 1,000

Restructuring Costs (Details)

Restructuring Costs (Details) $ in Thousands	1 Months Ended	12 Months Ended			18 Months Ended
	Jul. 31, 2018employee	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)
Restructuring costs
Restructuring costs		$ 181	$ 3,112
Fixed asset impairments		0	500	$ 0
Long-term portion of restructuring accrual			11
Cambridge, Massachusetts facility operations
Restructuring costs
Number of positions eliminated | employee	18
Percentage of positions eliminated	40.00%
Number of positions eliminated since inception | employee	15
Restructuring costs		$ 181	$ 3,534		$ 3,300
Non-cash asset impairments					700
Non-cash gain due to write-off of remaining deferred rent liability					400
Fixed asset impairments					500
Expenses associated with lease termination or prepaid expenses					200
Termination costs in connection with the reduction in workforce, including severance, benefits and related costs					$ 2,800

Restructuring Costs - Accrual R

Restructuring Costs - Accrual Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended		18 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019
Restructuring costs
Charges incurred	$ 181	$ 3,112
Cambridge, Massachusetts facility operations
Restructuring costs
Accrued restructuring balance, beginning of period	1,147
Charges incurred	181	3,534	$ 3,300
Cash payments	(1,215)	(1,605)
Non-cash settlements		(698)
Adjustments		(84)
Accrued restructuring balance, end of period	113	1,147	113
Cambridge, Massachusetts facility operations | Employee Severance and Benefits
Restructuring costs
Accrued restructuring balance, beginning of period	1,147
Charges incurred	181	2,635
Cash payments	(1,215)	(1,380)
Non-cash settlements		(24)
Adjustments		(84)
Accrued restructuring balance, end of period	$ 113	1,147	$ 113
Cambridge, Massachusetts facility operations | Contract Termination Costs
Restructuring costs
Charges incurred		225
Cash payments		(225)
Cambridge, Massachusetts facility operations | Asset Impairments
Restructuring costs
Charges incurred		674
Non-cash settlements		$ (674)

Stock-Based Compensation - Equi

Stock-Based Compensation - Equity Incentive Plans (Details) - shares	Jul. 26, 2003	Dec. 31, 2019	Dec. 31, 2018
Class of Stock
Common stock, shares reserved for future issuance		25,066,074
Common stock options outstanding		4,220,417	3,304,531
Options outstanding under earlier plans		366,974
Grant of inducement stock option		393,750
2013 Stock Incentive Plan
Class of Stock
Common shares available for grant	5,653,057	2,301,240
Maximum number of additional common shares	868,372
Common stock options outstanding		3,459,693
Restricted stock units outstanding		193,625

Stock-Based Compensation - Empl

Stock-Based Compensation - Employee Stock Purchase Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 07, 2017
1995 Employee Stock Purchase Plan | Maximum
Class of Stock
Common stock shares authorized for issuance under stock purchase plan	62,500
2017 Employee Stock Purchase Plan
Class of Stock
Maximum percentage of total combined voting power or value of the stock of the Company after the grant	5.00%
Common shares available for grant	321,341
2017 Employee Stock Purchase Plan | Maximum
Class of Stock
Common stock shares authorized for issuance under stock purchase plan				412,500
Employee Stock Purchase Plans
Class of Stock
Minimum percentage in payroll of deduction base salary to acquire shares of common stock	1.00%
Maximum percentage in payroll of deduction base salary to acquire shares of common stock	10.00%
Percentage of fair market value of common stock for the ESPP option price	85.00%
Annual maximum a participant may purchase under the employee stock purchase plan	$ 25,000
Common stock share issued	60,953	24,824	21,869
Defined Contribution Plan, Cost	$ 100,000	$ 100,000	$ 200,000
Employee Stock Purchase Plans | Maximum
Class of Stock
Subsequent offering period as established by the compensation committee	12 months

Stock-Based Compensation - Acco

Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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)	$ 1.64	$ 7	$ 8.08
Stock-based compensation	$ 3,845	$ 5,674	$ 10,720
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	1,348	1,851	6,494
Research and development | Former Executive
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation			4,300
Research and development | Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	36	71	96
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	1,312	1,780	6,398
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	2,497	3,799	4,226
General and administrative | Employee Stock Purchase Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	20	48	63
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 2,477	3,751	$ 4,163
Restructuring costs
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation		24
Restructuring costs | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation		$ 24

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions Used in Determining Fair Value of Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies
Options to purchase common stock granted to employees and directors	1,279,016	1,136,874	527,039
Average risk free interest rate	2.10%	2.50%	1.70%
Dividend rate	0.00%
Expected lives (years)	3 years 8 months 12 days	3 years 8 months 12 days	4 years
Expected volatility	84.00%	74.00%	86.00%
Weighted average exercise price of options granted during the period (per share)	$ 2.75	$ 12.63	$ 12.96

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options, Outstanding, Beginning Balance	3,304,531
Granted	1,279,016
Forfeited	(143,874)
Expired	(219,256)
Options, Outstanding, Ending Balance	4,220,417	3,304,531
Exercisable, Ending Balance	2,292,157
Weighted Average Exercise Price, Beginning Balance	$ 18.41
Granted, Weighted Average Exercise Price	2.75	$ 12.63	$ 12.96
Forfeited, Weighted Average Exercise Price	12.95
Expired, Weighted Average Exercise Price	31.29
Weighted Average Exercise Price, Ending Balance	13.08	$ 18.41
Exercisable, Weighted Average Exercise Price	$ 19.20
Outstanding, Ending balance, Weighted Average Remaining Contractual Term	6 years 7 months 6 days	6 years 7 months 6 days
Exercisable Ending Balance, Weighted Average Remaining Contractual Term	4 years 8 months 12 days
Fair value of options, vested	$ 4.7
Unrecognized compensation cost related to nonvested stock-based compensation	$ 5.2
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 6 months
Restricted Stock Activity
Unrecognized compensation cost related to nonvested stock-based compensation	$ 0.5
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	12 Months Ended
	Dec. 31, 2019USD ($)$ / sharesshares
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Unrecognized compensation expense | $	$ 5.2
Weighted average remaining period over which unrecognized compensation expense will be recognized	2 years 6 months
Restricted Stock Activity
Restricted Stock Activity, Number of Shares
Granted | shares	194,550
Cancelled | shares	(925)
Nonvested shares, Ending Balance | shares	193,625
Restricted Stock Activity, Weighted-Average Grant Date Fair Value
Granted, Weighted-Average Grant Date Fair Value | $ / shares	$ 3.14
Cancelled, Weighted-Average Grant Date Fair Value | $ / shares	3.14
Nonvested shares, Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 3.14
Unrecognized compensation expense | $	$ 0.5
Weighted average remaining period over which unrecognized compensation expense will be recognized	3 years

Commitments and Contingencies -

Commitments and Contingencies - Rent Expense and Lease Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Property, Plant and Equipment [Line Items]
Rent expense, including real estate taxes	$ 0.3
Rent expense, including real estate taxes		$ 1.7	$ 2.4
Exton Facility
Property, Plant and Equipment [Line Items]
Leased office space | ft²	11,000
Term of lease commitment (years)	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Commitments Under Lease Agreements (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments and Contingencies
2020	$ 217
2021	224
2022	229
2023	235
2024	240
2025	100
Total future minimum lease commitments	$ 1,245

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2018
Income Taxes
TCJA of 2017 provisional income tax expense		$ 27,600
Period over which NOL and tax credit carryforward limitations are applied	1 year
Unrecognized tax benefits from uncertain tax	$ 0	$ 0	$ 0
Period over which material changes in unrecognized tax positions are not expected	12 months
Federal
Income Taxes
Cumulative net operating loss carryforwards	$ 295,800
Percentage of taxable income that can be used to offset future taxable periods as a result of the TCJA	80.00%
Unlimited carryforward	$ 98,400
Tax credit carryforwards	21,600
State
Income Taxes
Cumulative net operating loss carryforwards	290,200
Tax credit carryforwards	$ 1,900
State | Massachusetts
Income Taxes
Carryforward term	20 years
Potential amount that may expire in a future period	$ 21,000
State | Pennsylvania
Income Taxes
Carryforward term	20 years

Income Taxes - Components of th

Income Taxes - Components of the Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Taxes
Operating loss carryforwards	$ 81,403	$ 70,509
Tax credit carryforwards	23,072	18,514
Lease liabilities	308
Other	7,994	8,627
Deferred Tax Assets, Gross	112,777	97,650
Right-of-use asset	(306)
Valuation allowance	$ (112,471)	$ (97,650)

Income Taxes - Difference Betwe

Income Taxes - Difference Between U.S. Federal Corporate Tax Rate and Company's Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Expected federal income tax rate	(21.00%)	(21.00%)	(34.00%)
Expiring credits and NOLs		1.00%
Change in valuation allowance	26.20%	37.90%	0.90%
Federal and state credits	(8.10%)	(7.40%)	(6.90%)
State income taxes, net of federal benefit	(4.70%)	(9.70%)	(3.70%)
Permanent differences	4.80%	0.50%	2.40%
Rate change related to TCJA			41.90%
Other	2.80%	(1.30%)	(0.60%)
Effective tax rate	0.00%	0.00%	0.00%
Maximum
Expected federal income tax rate			(35.00%)

Employee Benefit Plan (Details)

Employee Benefit Plan (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Benefit Plan
Maximum employer match as a percentage of base pay	5.00%	3.00%
Percentage the employer matches of employee contributions	100.00%	50.00%
Portion of the employee's base salary that the Company matches	5.00%	6.00%
Employer matching contributions to the plan		$ 0.3	$ 0.2	$ 0.3

Related Party Transactions - Ov

Related Party Transactions - Overview of Related Parties (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 01, 2017	Oct. 30, 2017	May 05, 1998	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transactions
Exercise price of warrants				$ 0.75	$ 0.08
Number of Warrants				5,098,916	2,768,882
Common stock issued in lieu of board fees				53,985	13,654	7,867
Stock issued (in shares)				1,535,848
Maximum
Related Party Transactions
Proceeds from issuance of common stock in lieu of director board and committee fees				$ 0.1	$ 0.1	$ 0.1
Board of Director
Related Party Transactions
Aggregate common shares				4,608,786
Common Stock
Related Party Transactions
Stock issued (in shares)	625,000	4,166,666	149,960
Common Stock | Board of Director
Related Party Transactions
Ownership percentage				16.00%
Pillar II
Related Party Transactions
Number of warrants exercised						629,257
Proceeds from exercise of warrants						$ 3.5
Pillar Investment Entities
Related Party Transactions
Ownership percentage				11.00%
Besancon
Related Party Transactions
Number of warrants exercised						364,752
Exercise price of warrants					$ 3.76
Proceeds from exercise of warrants					$ 0.6	$ 1.9
Shares issued on exercise of warrants during the period					150,000
Baker Bros. Advisors LP
Related Party Transactions
Number of warrants exercised					2,700,791
Exercise price of warrants					$ 3.76
Proceeds from exercise of warrants					$ 9.5
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 Warrants				2,708,812
Baker Bros. Advisors LP | Pre-funded Warrants | Scenario Two | Maximum
Related Party Transactions
Number of Shares				2,368,400
Baker Bros. Advisors LP | Series B1 Preferred Warrant | Scenario Two
Related Party Transactions
Exercise price of warrants				$ 152
Baker Bros. Advisors LP | Preferred stock | Scenario Two
Related Party Transactions
Exercise price of warrants				$ 1.52
Number of Warrants				23,684
Baker Bros. Advisors LP | Common Stock
Related Party Transactions
Stock issued (in shares)		1,000,000

Net Loss per Common Share App_2

Net Loss per Common Share Applicable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Loss per Common Share Applicable to Common Stockholders
Total antidilutive securities	61,289,079	6,075,339	8,145,188

Subsequent Events - Proceeds fr

Subsequent Events - Proceeds from Sale of Common Stock (Details) - USD ($) $ in Thousands	Mar. 04, 2019	Mar. 11, 2020	Dec. 31, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Stock issued (in shares)			1,535,848
Net proceeds from offering of common stock			$ 3,700
"At-The-Market" Equity Program
Subsequent Event [Line Items]
Stock issued (in shares)			532,700	0
"At-The-Market" Equity Program | Subsequent Events
Subsequent Event [Line Items]
Stock issued (in shares)		403,983
Net proceeds from offering of common stock		$ 600
Lincoln Park Capital Fund, LLC (“Investor”)
Subsequent Event [Line Items]
Stock issued (in shares)	269,749
Lincoln Park Capital Fund, LLC (“Investor”) | Subsequent Events
Subsequent Event [Line Items]
Stock issued (in shares)		450,000
Net proceeds from offering of common stock		$ 800