Viridian Therapeutics (VRDN) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Entity Registrant Name	MIRAGEN THERAPEUTICS, INC.
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
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 Common Stock, Shares Outstanding		53,077,348
Entity Central Index Key	0001590750
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Shell Company	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 36,103	$ 24,846
Short-term investments	0	1,999
Accounts receivable	4	108
Prepaid expenses and other current assets	2,234	2,786
Total current assets	38,341	29,739
Property and equipment, net	443	523
Operating lease right-of-use asset, net	266
Total assets	39,050	30,262
Current liabilities:
Accounts payable	1,629	1,096
Accrued liabilities	3,055	5,108
Current portion of note payable	3,977	3,976
Total current liabilities	8,661	10,180
Note payable, net of current portion	3,389	4,328
Total liabilities	12,050	14,508
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 100,000,000 shares authorized; 53,077,348 and 34,861,876 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	531	349
Additional paid-in capital	202,685	183,574
Accumulated deficit	(176,216)	(168,169)
Total stockholders’ equity	27,000	15,754
Total liabilities and stockholders’ equity	$ 39,050	$ 30,262

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	53,077,348	34,861,876
Common stock, shares outstanding (in shares)	53,077,348	34,861,876

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Total revenue	$ 828	$ 372
Operating expenses:
Research and development	6,103	8,751
General and administrative	2,723	3,357
Total operating expenses	8,826	12,108
Loss from operations	(7,998)	(11,736)
Other income (expense):
Interest and other income	95	339
Interest and other expense	(141)	(232)
Net loss	(8,044)	(11,629)
Change in unrealized gain on investments	0	5
Comprehensive loss	(8,044)	(11,624)
Net loss	$ (8,044)	$ (11,629)
Net loss per share, basic and diluted (in dollars per share)	$ (0.18)	$ (0.38)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	45,476,338	30,886,085
Collaboration revenue
Revenue:
Total revenue	$ 681	$ 348
Grant revenue
Revenue:
Total revenue	$ 147	$ 24

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Public offering	2019 Stock purchase agreement	At-the-market	Common Stock	Common StockPublic offering	Common Stock2019 Stock purchase agreement	Common StockAt-the-market	Additional Paid-in Capital	Additional Paid-in CapitalPublic offering	Additional Paid-in Capital2019 Stock purchase agreement	Additional Paid-in CapitalAt-the-market	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018					30,839,463
Beginning balance at Dec. 31, 2018	$ 51,344				$ 308				$ 177,335				$ (3)	$ (126,296)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)					47,589
Issuance of common stock, net of issuance cost	134				$ 1				133
Issuance of common stock for cash under employee stock purchase plan (in shares)					34,167
Issuance of common stock for cash under employee stock purchase plan	84								84
Share-based compensation expense	1,018								1,018
Change in unrealized gain on investments	5												5
Net loss	(11,629)													(11,629)
Ending balance (in shares) at Mar. 31, 2019					30,921,219
Ending balance at Mar. 31, 2019	$ 40,956				$ 309				178,570				2	(137,925)
Beginning balance (in shares) at Dec. 31, 2019	34,861,876				34,861,876
Beginning balance at Dec. 31, 2019	$ 15,754				$ 349				183,574				0	(168,169)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)						15,000,000	2,200,000	975,063
Issuance of common stock, net of issuance cost		$ 13,881	$ 4,049	$ 670		$ 150	$ 22	$ 10		$ 13,731	$ 4,027	$ 660
Shares issued for cash upon the exercise of stock options (in shares)					17,238
Shares issued for cash upon the exercise of stock options	13								13
Issuance of common stock for cash under employee stock purchase plan (in shares)					23,171
Issuance of common stock for cash under employee stock purchase plan	16								16
Share-based compensation expense	664								664
Change in unrealized gain on investments	0
Net loss	$ (8,044)													(8,044)
Ending balance (in shares) at Mar. 31, 2020	53,077,348				53,077,348
Ending balance at Mar. 31, 2020	$ 27,000				$ 531				$ 202,685				$ 0	$ (176,216)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (8,044)	$ (11,629)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	664	1,018
Implementation of ASC 842 and other non-cash lease expenses	75
Non-cash interest expense	63	94
Depreciation and amortization	68	73
Loss on sale of equipment	11	0
Amortization of premiums and discounts on available-for-sale securities	(1)	(182)
Changes in operating assets and liabilities:
Accounts receivable	104	18
Prepaid expenses and other assets	436	(298)
Accounts payable	410	(54)
Accrued and other liabilities	(2,245)	(849)
Net cash used in operating activities	(8,459)	(11,809)
Cash flows from investing activities:
Purchases of short-term investments	0	(23,783)
Maturities of short-term investments	2,000	21,000
Proceeds from sale of property and equipment	1	0
Purchases of property and equipment	0	(37)
Net cash provided by (used in) investing activities	2,001	(2,820)
Cash flows from financing activities:
Proceeds from the sale of common stock and warrants	19,754	138
Payment of issuance costs associated with the sale of common stock	(1,068)	(4)
Payments of principal on note payable	(1,000)	0
Proceeds from stock purchases under employee stock purchase plan	16	84
Proceeds from the exercise of stock options	13	0
Net cash provided by financing activities	17,715	218
Net increase (decrease) in cash and cash equivalents	11,257	(14,411)
Cash and cash equivalents at beginning of period	24,846	32,606
Cash and cash equivalents at end of period	36,103	18,195
Supplemental disclosure of cash flow information
Cash paid for interest	61	136
Supplemental disclosure of non-cash investing and financing activities
Amortization of public offering costs	30	1
Change in unrealized gain on investments	$ 0	$ 5

DESCRIPTION OF BUSINESS

DESCRIPTION OF BUSINESS	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	DESCRIPTION OF BUSINESS Miragen Therapeutics, Inc., a Delaware corporation (the “Company” or “miRagen”), is a clinical-stage biopharmaceutical company discovering and developing proprietary RNA-targeted therapies with a specific focus on microRNAs and their role in diseases where there is a high unmet medical need. The Company has three clinical stage product candidates: cobomarsen, remlarsen, and MRG-110. The Company is developing cobomarsen for the treatment of patients with certain cancers that have elevated microRNA-155, including cutaneous T-cell lymphoma and adult T-cell leukemia/lymphoma. Cobomarsen is an inhibitor of microRNA‑155, which is found at abnormally high levels in malignant cells of several blood cancers. The Company is also developing remlarsen and MRG-229, which are product candidates being developed for the treatment of patients with pathological fibrosis. These product candidates are replacements for microRNA‑29 (“miR‑29”), which is found at abnormally low levels in a number of pathological fibrotic conditions, including cutaneous, cardiac, renal, hepatic, pulmonary and ocular fibrosis, as well as in systemic sclerosis. MRG-110, an inhibitor of microRNA‑92, is the Company’s product candidate for the treatment of heart failure, wound healing, and other ischemic disease. The Company believes its experience in microRNA biology and chemistry, drug discovery, bioinformatics, translational medicine, and drug development allows it to identify and develop microRNA-targeted drugs that are designed to regulate gene pathways to return diseased tissues to a healthy state. The Company believes its drug discovery and development strategy will enable it to progress its product candidates from preclinical discovery to confirmation of mechanism of action in humans quickly and efficiently. The elements of this strategy include identification of mechanistic biomarkers, in early-stage clinical trials to assess target engagement in humans, as well as monitoring outcomes in these early-stage clinical trials to help guide later clinical development. Liquidity The Company has funded its operations to date principally through proceeds received from the sale of the Company’s common stock (“Common Stock”) and other equity securities, debt financings, up-front milestones, and reimbursements received under a prior license and collaboration agreement. Since its inception and through March 31, 2020 , the Company has generated an accumulated deficit of $176.2 million . As of March 31, 2020 , the Company had approximately $36.1 million in cash and cash equivalents. Based on its current operating plans, management believes that the Company’s cash and cash equivalents, combined with the effect of the six-month deferral of interest-only payments and the maturity date related to the Company’s loan and security agreement with Silicon Valley Bank (the “2017 SVB Loan Agreement”) in April 2020 (see Note 7. Notes Payable ), will be sufficient to fund the Company’s operations into the third quarter of 2021 . In March 2020, the World Health Organization declared the outbreak of COVID-19, a novel strain of Coronavirus, a global pandemic. This outbreak is causing major disruptions to businesses and markets worldwide as the virus spreads. The Company cannot predict what the long-term effects of this pandemic and the resulting economic disruptions may have on the Company’s liquidity and results of operations. The extent of the effect of the COVID-19 pandemic on the Company’s liquidity and results of operations will depend on a number future developments, including the duration, spread and intensity of the pandemic, and governmental, regulatory and private sector responses, all of which are uncertain and difficult to predict. The COVID-19 pandemic may make it more difficult for the Company to enroll patients in any future clinical trials or cause the Company to further delay enrollment or announcement of results from its ongoing clinical trials. The economic uncertainty surrounding the COVID-19 pandemic may also dramatically reduce the Company’s ability to secure debt or equity financing necessary to support the Company’s operations. The Company is unable to currently estimate the financial effect of the pandemic. If the pandemic continues to be a severe worldwide crisis, it could have a material adverse effect on the Company’s business, results of operations, financial condition, and cash flows. The financial statements do not reflect any adjustments as a result of the COVID-19 pandemic. The Company has no products approved for commercial sale, has not generated any revenue from product sales, and cannot guarantee when or if it will generate any revenue from product sales. Since its inception and through March 31, 2020, the Company has generated an accumulated deficit of $176.2 million . Substantially all of the Company’s operating losses resulted from expenses incurred in connection with its research and development programs and from general and administrative costs associated with its operations. The Company expects to incur significant expenses and operating losses for at least the next several years as it continues the clinical development of, and seeks regulatory approval for, its product candidates. It is expected that operating losses will fluctuate significantly from quarter to quarter and year to year due to timing of clinical development programs and efforts to achieve regulatory approval. The Company will continue to require additional capital beyond its current cash runway guidance of into the third quarter of 2021 to continue its operations. The amount and timing of future funding requirements will depend on many factors, including the pace and results of the Company’s clinical development efforts, equity financings, entering into license and collaboration agreements, and issuing debt or other financing vehicles. The Company’s ability to secure additional capital is dependent upon a number of factors, some of which are outside of the Company’s control, including success in developing its technology and drug product candidates, operational performance, and market conditions, including resulting from the ongoing COVID-19 pandemic. Failure to raise capital as and when needed, on favorable terms or at all, would have a negative impact on the Company’s financial condition and its ability to develop its product candidates. Changing circumstances may cause the Company to consume capital significantly faster or slower than currently anticipated. If the Company is unable to acquire additional capital or resources, it will be required to modify its operational plans. The estimates included herein are based on assumptions that may prove to be wrong, and the Company could exhaust its available financial resources sooner than currently anticipated.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2020 , or for any other interim period, or for any other future year. The balance sheet as of December 31, 2019 has been derived from audited consolidated financial statements at that date but does not include all the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements of the Company and the notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2019 , filed with the SEC on March 13, 2020. The Company’s management performed an evaluation of its activities through the date of filing of these financial statements and concluded that there are no subsequent events requiring disclosure, other than as disclosed. Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company’s evaluation entails, among other things, analyzing the results of the Company’s clinical development efforts, license and collaboration agreements as well as the entity’s current financial condition including conditional and unconditional obligations anticipated within a year, and related liquidity sources at the date the financial statements are issued. This is reflected in the Company’s prospective operating budgets and forecasts and compared to the current cash and cash equivalent balance. Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with U.S. GAAP, which requires it to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Although these estimates are based on the Company’s knowledge of current events and actions it may take in the future, actual results may ultimately differ from these estimates and assumptions. Revenue Recognition The Company accounts for revenue in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”). The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license, or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such agreements. The terms of these agreements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; developmental, clinical, regulatory, and commercial sales milestone payments; and royalties on net sales of licensed products. 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 Company expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized, for agreements within the scope of ASC 606, the Company performs the following five steps: (i) identification of the goods or services within the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct within the terms of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the identified performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s agreements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. Performance obligations are promises in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available, and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each agreement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical 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 collaboration and other research and development revenue in the period of adjustment. For agreements that include sales-based royalties, 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, 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 the Company’s collaboration or strategic alliance agreements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction, and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and 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. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. Research and Development Research and development costs are expensed as incurred in performing research and development activities. The costs include employee-related expense including salaries, benefits, share-based compensation, restructuring charges, fees for acquiring and maintaining licenses under third-party license agreements, consulting fees, market research, costs of research and development activities conducted by third parties on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, and facilities and overhead costs. The Company records research and development expense in the period in which the Company receives or takes ownership of the applicable goods or when the applicable services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records up-front and milestone payments to acquire and retain contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights. The Company considers future economic benefits from acquired contractual rights to licensed technology to be uncertain until such a drug candidate is approved for sale by the U.S. Food and Drug Administration or when other significant risk factors are abated. Clinical Trial and Preclinical Study Accruals The Company makes estimates of accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on certain facts and circumstances at that time. The Company’s accrued expenses for clinical trials and preclinical studies are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and other providers. Payments under the Company’s agreements with external service providers depend on a number of factors, such as site initiation, patient screening, enrollment, delivery of reports, and other events. In accruing for these activities, the Company obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to the Company’s research and development expenses may be necessary in future periods as its estimates change. Restructuring and Other Charges The Company accounts for exit or disposal activities in accordance with FASB ASC Topic 420, Exit or Disposal Cost Obligations ( “ ASC 420 ” ). A business restructuring is defined as an exit or disposal activity that includes, but is not limited to, a program that is planned and controlled by management and materially changes either the scope of a business or the manner in which that business is conducted. Business restructuring charges include (i) one-time termination benefits related to employee separations, (ii) contract termination costs, and (iii) other related costs associated with exit or disposal activities including. In 2020 and 2019, t he Company implemented two phases of a restructuring plan to streamline the organization, reduce costs, and direct resources to advance the Company’s primary operating goals. The Company recognizes and measures a liability for one-time termination benefits, for which no future service is required, once the plan of termination meets all of the following criteria for an established communication date: (i) management commits to a plan of termination, (ii) the plan identifies the number of employees to be terminated and their job classifications or functions, locations and the expected completion date, (iii) the plan establishes the terms of the benefit arrangement, and (iv) it is unlikely that significant changes to the plan will be made or the plan will be withdrawn. For one-time termination benefits for which future service is required, a liability is measured at the communication date based on its value as of the termination date and recognized ratably over the future service period. The Company recognizes and measures a liability for other related costs in the period in which the liability is incurred. Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees and members of its board of directors under its 2008 Equity Incentive Plan (the “2008 Plan”) and under its 2016 Equity Incentive Plan (the “2016 Plan”) by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model. The Company recognizes share-based compensation expense on a straight-line basis over the vesting term. Prior to 2019, the Company determined the value of Common Stock options issued to non-employees (other than members of its board of directors) using the Black-Scholes option pricing model and adjusting the value of such awards to current fair value each reporting period until the awards were vested or a performance commitment had otherwise been reached. After adoption of Accounting Standards Update (“ASU”) 2018-07, Compensation-Stock Compensation (Topic 718) , on January 1, 2019, non-employee stock options are valued at the award’s inception using grant-date fair value, in the same manner of stock options granted to employees. Any outstanding and partially vested non-employee stock option shares were remeasured on January 1, 2019. The adoption of this standard had an immaterial impact on the Company’s condensed consolidated financial statements. Cash and Cash Equivalents All highly-liquid investments that have maturities of 90 days or less at the date of purchase are classified as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments. Investments The Company has designated its investments as available-for-sale securities and accounts for them at their respective fair values. The securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are readily available for use in current operations are classified as short-term available-for-sale securities and are reported as a component of current assets in the accompanying condensed consolidated balance sheets. Securities that are classified as available-for-sale are measured at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders’ equity until their disposition. The Company reviews available-for-sale securities at the end of each period to determine whether they remain available-for-sale based on its then current intent. The cost of securities sold is based on the specific identification method. The securities are subject to a periodic impairment review. An impairment charge would occur when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary. As of March 31, 2020 , the Company did not have any balances associated with available-for-sale securities. As of December 31, 2019 , the Company’s short-term available-for-sale securities had an amortized cost of $2.0 million , fair value of $2.0 million , and no associated unrealized gain or loss. The Company had no long-term investments as of March 31, 2020 or December 31, 2019 . Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. March 31, 2020 December 31, 2019 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 36,896 $ — $ 25,263 $ — U.S. treasury securities (included in short-term investments) — — 1,999 — Total assets $ 36,896 $ — $ 27,262 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 100 $ — $ 100 Fair Value of Financial Instruments Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate their fair value due to the short-term nature of their maturities, such as cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses. The carrying amount of the Company’s note payable approximates its fair value (a Level 2 fair value measurement), reflecting interest rates currently available to the Company. The Company accounts for warrants to purchase its stock pursuant to ASC Topic 470, Debt , and ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for Common Stock as liabilities or equity. The warrants classified as liabilities are reported at their estimated fair value and any changes in fair value are reflected in interest and other expense. The warrants classified as equity are reported at their estimated fair value with no subsequent remeasurement. The Company’s outstanding warrants are discussed in more detail in Note 10. Warrants . Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts. The Company invests its excess cash primarily in deposits and money market funds held with one financial institution. Property and Equipment The Company carries its property and equipment at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the life of the lease (including any renewal periods that are deemed to be reasonably assured) or the estimated useful life of the assets. Construction in progress is not depreciated until placed in service. Repairs and maintenance costs are expensed as incurred and expenditures for major improvements are capitalized. Operating Lease Right-of-Use Asset The Company determines if an arrangement is, or contains, a lease at contract inception and during modifications or renewal of existing leases. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. The Company’s existing operating lease assets and liabilities were recognized upon the date of transition to ASC 842, on January 1, 2020. Going forward the Company’s operating lease assets and liabilities will be recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. The lease payments used to determine the Company’s operating lease assets may include lease incentives, stated rent increases, and escalation clauses and are recognized in the Company’s operating lease assets in the Company’s condensed consolidated balance sheets. The Company’s operating leases are reflected in operating lease right-of-use asset and operating lease liability within accrued liabilities in the Company’s consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Short-term leases, defined as leases that have a lease term of 12 months or less at the commencement date, are excluded from this treatment and are recognized on a straight-line basis over the term of the lease. Refer to Note 8. Commitments and Contingencies - Lease Obligations Payable for additional information related to the Company’s operating leases. Impairment of Long-Lived Assets The Company assesses the carrying amount of its property and equipment whenever events or changes in circumstances indicate the carrying amount of such assets may not be recoverable. No impairment charges were recorded during the three months ended March 31, 2020 and 2019 . Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is antidilutive. Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments. Unrealized accumulated comprehensive gains or losses are reflected as a separate component in the statement of stockholders’ equity. The Company had no realized or unrealized gains or losses during the three months ended March 31, 2020 . The Company had an unrealized gain of $5 thousand and no realized gains or losses during the three months ended March 31, 2019. Income Taxes The Company accounts for income taxes by using an asset and liability method of accounting for deferred income taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is recorded to the extent it is more likely than not that a deferred tax asset will not be realized. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. The Company’s significant deferred tax assets are for net operating loss carryforwards, tax credits, accruals and reserves, and capitalized start-up costs. The Company has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, the Company has concluded that it is more likely than not that its deferred tax assets will not be realized. The Company has no unrecognized tax benefits. The Company classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations and comprehensive loss as general and administrative expenses. No such expenses have been recognized during the three months ended March 31, 2020 and 2019 . The legislation informally titled the Tax Cuts and Jobs Act of 2017 (“Tax Act”) was signed into law on December 22, 2017. The Tax Act includes significant changes to the U.S. corporate income tax system, including: (i) a federal corporate rate reduction from 35% to 21%; (ii) limitations on the deductibility of interest expense and executive compensation; (iii) elimination of the corporate alternative minimum tax (“AMT”) and a change in how existing AMT credits can be realized; (iv) change in the rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017; (v) reduction of the orphan drug credit from 50% to 25%; and (vi) transition of U.S. international taxation from a worldwide tax system to a territorial tax system. The Tax Act did not have a material impact on the Company’s condensed consolidated financial statements primarily due to the valuation allowance recorded against its net deferred tax assets. Segment Information The Company operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with the Company’s partners are denominated in U.S. dollars, except where noted. Recent Accounting Pronouncements – Adopted Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842), and subsequent amendments to the initial guidance: ASU No. 2017-13, ASU No. 2018-10, and ASU No. 2018-11 (collectively, “ASC 842”). The Company adopted ASC 842 on January 1, 2020, using the optional transition method permitted by ASU No. 2018-11. The Company’s building operating lease commitments are subject to the new standard, which resulted in an operating lease liability of $0.4 million and a right-of-use asset of $0.4 million , with no material effect on the Company’s condensed consolidated statements of operations and comprehensive loss.

RESTRUCTURING PLAN

RESTRUCTURING PLAN	3 Months Ended
	Mar. 31, 2020
Restructuring and Related Activities [Abstract]
RESTRUCTURING PLAN	RESTRUCTURING PLAN In August 2019, the Company began implementing two phases of a cost restructuring plan to streamline the organization, reduce costs, and direct resources to advance cobomarsen and miR-29 mimics, including remlarsen and MRG-229, while reducing investments in new discovery research. The restructuring plan identified approximately 44 positions for elimination, or approximately 50% of the Company’s then total workforce. The eliminated positions were primarily related to research and development and corresponding project, general, and administrative support. Through March 31, 2020 , the Company had recorded cumulative restructuring expense of $2.2 million and expects to incur approximately $0.2 million in additional restructuring expense, primarily related to retention, during the remainder of 2020. The Company recorded $0.1 million in restructuring charges during the three months ended March 31, 2020 , which was primarily related to retention transactions and recorded in research and development expenses on the condensed consolidated statements of operations and comprehensive loss. The following table summarizes the Company’s accrued restructuring liability balance and associated activity (in thousands): December 31, 2019 Additions Cash Payments March 31, 2020 Retention $ 935 $ 119 $ (935 ) $ 119 Severance and severance-related expenses 580 — (283 ) 297 Total restructuring liability $ 1,515 $ 119 $ (1,218 ) $ 416

STRATEGIC ALLIANCE AND COLLABOR

STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER	STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER In October 2011, the Company entered into a license and collaboration agreement (the “Servier Collaboration Agreement”) with Les Laboratoires Servier and Institut de Recherches Servier (collectively, “Servier”) for the research, development, and commercialization of RNA-targeting therapeutics in cardiovascular disease. Under the Servier Collaboration Agreement, the Company granted Servier an exclusive license to research, develop, manufacture, and commercialize RNA-targeting therapeutics for certain microRNA targets in the cardiovascular field. In August 2019, Servier terminated the Servier Collaboration Agreement effective in February 2020. During the period from receipt of notice from Servier in August 2019 and termination in February 2020, the Company completed certain activities under its development plan with Servier, which included finalizing the two Phase 1 clinical trials of MRG-110. The activities for which the Company is eligible for reimbursement under the Servier Collaboration Agreement are considered a research and development performance obligation and revenue are recognized in accordance with ASC 606 through the termination date. Accounting Analysis The Company evaluated the Servier Collaboration Agreement in accordance with the provisions in ASC 606. The Company has accounted for amendments to the Servier Collaboration Agreement as modifications to the original contract and not as separate contracts. The Company combined the amendments with the original agreement due to the modifications not resulting in increased promised goods or services that were distinct, and the price of the contract did not increase by an amount of consideration that reflects the Company’s standalone selling prices. The Company identified the following performance obligations under the Servier Collaboration Agreement: (i) up-front license fee for a multiple-year research collaboration, under which it jointly performed agreed upon research activities directed to the identification and characterization of named targets and oligonucleotides in the cardiovascular field (the “Research Collaboration”); (ii) research and development activities; (iii) transfer of materials; (iv) developmental, clinical, regulatory, and commercial sales milestone payments; and (v) royalties on net sales of licensed products. The Company acts as a principal as it controls the goods or services prior to transfer to the customer. The Company performed the research and development activities specified in the contracts and controlled the laboratories and resources that performed the research and development activities. The Company concluded that the up-front license fees were not distinct from the Research Collaboration as Servier cannot obtain the benefit of the license without the Research Collaboration. This performance obligation represented the licensing of Company‑owned intellectual property related to the Company’s knowledge of microRNA therapeutics for certain specific diseases, together with research activities that were interdependent with licensed intellectual property to determine feasibility of commercialization. As of January 1, 2019, the date of the initial application of ASC 606 by the Company, the remaining total transaction price associated with the Servier Collaboration Agreement was determined to be approximately $3.1 million consisting of maximum reimbursements of development costs under the development plan. During February 2019, the Joint Steering Committee approved an additional $1.0 million of development plan activities. As of January 1, 2019, the Company identified up to $60.4 million in development and regulatory milestones under the Servier Collaboration Agreement, and the Company had recognized $7.5 million in milestone revenue through the initial application date. The Company utilizes the most likely amount method to estimate any development and regulatory milestone payments to be received. The Company considered the stage of development and the risks associated with the remaining development required to achieve these milestones, as well as whether the achievement of the milestones is outside the control of the Company. The Company determined that the remaining milestone payments were fully constrained, as a result of the uncertainty whether the milestones would be achieved by March 31, 2020 . The Company also determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur and, therefore, these payments have also been excluded from the transaction price. The Company re-evaluates the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. As of March 31, 2020 , no adjustments to the transaction price were noted. The transaction price was allocated to the performance obligations based on the relative estimated standalone selling prices of each performance obligation or, in the case of certain variable consideration, to one or more performance obligations. Research and development activities are priced generally at the standard labor rates for the respective activity and transfer of materials are generally priced at cost. Milestone payments are individually negotiated and because of the unique nature of each milestone, there are no comparable transactions to compare to; therefore, the negotiated amounts of the milestones in the agreement are the standalone selling price. Amounts incurred and billable, but not billed to Servier, for research and related intellectual property activities totaled $1 thousand and $0.3 million as of March 31, 2020 and December 31, 2019 , respectively. These amounts are included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheets. As of March 31, 2020 and December 31, 2019 , the Company had no accounts receivable balances outstanding for Servier research and related intellectual property activities. The amounts recognized in 2019 under ASC 606 did not materially differ from what the Company would have recognized under ASC 605. During the three months ended March 31, 2020 and 2019 , the Company recorded collaboration revenue related to reimbursable research and development costs under the Servier Collaboration Agreement of $0.7 million and $0.3 million , respectively.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment, net, consisted of the following: March 31, December 31, (in thousands) Lab equipment $ 2,507 $ 2,507 Leasehold improvements 741 741 Computer hardware and software 403 457 Furniture and fixtures 166 166 Property and equipment, gross 3,817 3,871 Less: accumulated depreciation and amortization (3,374 ) (3,348 ) Property and equipment, net $ 443 $ 523 During the three months ended March 31, 2020 and 2019 , depreciation and amortization expense was $0.1 million . Depreciation and amortization expense is recorded primarily in research and development expense on the condensed consolidated statements of operations and comprehensive loss.

ACCRUED LIABILITIES

ACCRUED LIABILITIES	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
ACCRUED LIABILITIES	ACCRUED LIABILITIES Accrued liabilities consisted of the following: March 31, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 1,012 $ 2,259 Accrued employee compensation and related taxes 524 508 Restructuring liability 416 1,515 Accrued legal fees and expenses 323 284 Operating lease liability 306 — Accrued other professional service fees 282 254 Value of liability-classified stock purchase warrants 100 100 Deferred and accrued facility lease obligations — 66 Accrued equipment and lab materials 11 1 Other accrued liabilities 81 121 Total accrued liabilities $ 3,055 $ 5,108

NOTES PAYABLE

NOTES PAYABLE	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
NOTES PAYABLE	NOTE PAYABLE 2017 Silicon Valley Bank Loan Agreement In November 2017, the Company entered into the 2017 SVB Loan Agreement. Upon entry into the 2017 SVB Loan Agreement, the Company borrowed $10.0 million with a 30 -month payment period following an 18 -month interest-only payment period ending in November 2021. In April 2020, the 2017 Loan Agreement was amended to extend the interest-only payment period and extended maturity date by an additional six months. Amounts outstanding bear interest at the prime rate ( 3.25% and 4.75% at March 31, 2020 and December 31, 2019 , respectively), with a final payment fee equal to $0.9 million due upon maturity. As of March 31, 2020 , no additional amounts are available under the 2017 SVB Loan Agreement. The Company may elect to prepay prior to maturity all or any portion of the outstanding principal amounts under the 2017 SVB Loan Agreement, subject to a prepayment charge, depending on the date of prepayment or upon the occurrence of an event of default in which the Company’s obligations to repay the outstanding principal is accelerated. The Company’s obligations under the 2017 SVB Loan Agreement are secured by a first-priority security interest, right, and title in all business assets, excluding the Company’s intellectual property, which is subject to a negative pledge. The 2017 SVB Loan Agreement includes customary representations, warranties, and covenants (affirmative and negative), including restrictive covenants that limit the Company’s ability to: encumber or dispose of the collateral securing the loan; change the business of the Company; transfer a material portion of the Company’s assets; acquire other businesses; and merge or consolidate with or into any other business organization; incur additional indebtedness; declare or pay any cash dividend or make a cash distribution on any class of stock or other equity interest; enter into specified material transactions with Company affiliates; make non-ordinary course payments or enter into any amendment regarding subordinated debt of the Company; or become an “investment company” under the Investment Company Act of 1940, as amended; in each case subject to specified exceptions. The 2017 SVB Loan Agreement also includes standard events of default, including payment defaults; breaches of covenants following any applicable cure period; material breaches of representations or warranties; the occurrence of a material adverse change (as defined in the 2017 SVB Loan Agreement); events relating to bankruptcy or insolvency; breaches of material third-party agreements; the occurrence of an unsatisfied material judgment against the Company; and specified governmental actions against the Company, including specified actions by the U.S. Food and Drug Administration. Upon the occurrence of an event of default, Silicon Valley Bank may declare all outstanding obligations immediately due and payable, including a prepayment charge, and take such other actions as are set forth in the 2017 SVB Loan Agreement. Upon the occurrence of an event of default, at the Silicon Valley Bank’s discretion, interest on the 2017 SVB Loan Agreement will accrue at 5.0% above the rate that is otherwise applicable thereto until the earlier of the repayment of the Company’s obligations under the 2017 SVB Loan Agreement or the cure of such event of default. Amounts outstanding under the 2017 SVB Loan Agreement were as follows: March 31, December 31, (in thousands) Principal amount outstanding $ 6,667 $ 7,667 Unamortized debt discount (27 ) (32 ) Accreted final payment fee 726 669 Total note payable 7,366 8,304 Less: current maturities (3,977 ) (3,976 ) Note payable, net of current portion $ 3,389 $ 4,328 Future annual minimum principal payments under the 2017 SVB Loan Agreement as of March 31, 2020 for the respective calendar years are as follows (in thousands): 2020 $ 3,000 2021 3,667 Total $ 6,667 Future annual minimum principal payments under the 2017 SVB Loan Agreement as of March 31, 2020 (after giving effect to the amendment of the 2017 SVB Loan Agreement in April 2020), for the respective calendar years would have been as follows (in thousands): 2020 $ 1,000 2021 4,000 2022 1,667 Total $ 6,667

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Indemnification Agreements The Company has entered into indemnification agreements with each of its directors and officers whereby it has agreed to indemnify such persons for certain events or occurrences while the individual is, or was, serving as a director, officer, employee, or other agent of the Company. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. Employment Agreements The Company has entered into agreements with its executives and its employees that provide for base salary, severance, eligibility for bonuses, and other generally available benefits. The agreements provide that the Company may terminate the employment of its employees, including executives, at any time, with or without cause. If an employee under an employment agreement is terminated without cause, as defined in the employment agreements, or an employee under an employment agreement resigns for good reason, as defined in the employment agreements, then the employee under the employment agreement is entitled to receive, upon the execution of a release agreement, a severance package consisting of one or more of the following provisions: (i) the equivalent of up to 3 months of the employee’s base salary in effect immediately prior to date of termination; (ii) acceleration of vesting of the equivalent of up to 3 months of vesting of the executive’s outstanding unvested stock options or other equity awards that were outstanding as of the effective date of the executive’s employment agreement; and (iii) up to 3 months of continued health coverage. If an executive is terminated without cause or resigns for good reason within one month prior to or 12 months following a change of control, as defined in the employment agreements, the executive is entitled to receive, upon the execution of a release agreement, a severance package consisting of: (i) the equivalent of 12 months of the executive’s base salary in effect immediately prior to date of termination; (ii) the vesting in full of the executive’s then-outstanding stock options or other equity awards subject to time-based vesting; and (iii) 12 months of continued health coverage. Solely in the case of the Company’s Chief Executive Officer, if such termination occurs one month before or 12 months following a change of control, then, upon the execution of a release agreement, the executive is entitled to: (i) the equivalent of 24 months of the executive’s base salary in effect immediately prior to the date of termination; (ii) the vesting in full of the executive’s outstanding stock options or other equity awards subject to time-based vesting; and (iii) 12 months of continued health coverage. License Agreement with the University of Texas As of March 31, 2020 , the Company had one exclusive patent license agreement (the “UT License Agreement”) with the Board of Regents of The University of Texas System (the “University of Texas”). Under the UT License Agreement, the University of Texas granted the Company exclusive and nonexclusive licenses to certain patent and technology rights. At the time the UT License Agreement was entered into, the University of Texas was a minority stockholder of the Company. In consideration of rights granted by the University of Texas, the Company is required to: (i) pay a nonrefundable up-front license documentation fee in the amount of $10 thousand ; (ii) pay an annual license maintenance fee in the amount of $10 thousand starting one year from the date of the agreement; (iii) reimburse the University of Texas for actual costs incurred in conjunction with the filing, prosecution, enforcement, and maintenance of patent rights prior to the effective date; and (iv) bear all future costs of and manage the filing, prosecution, enforcement, and maintenance of patent rights. During the three months ended March 31, 2020 and 2019 , the Company incurred immaterial up-front and maintenance fees, which were recorded as research and development expense. All costs related to the filing, prosecution, and maintenance of patent and technology rights are recorded as general and administrative expense when incurred. Under the terms of the UT License Agreement, the Company may be obligated to make the following future milestone payments for each licensed product candidate: (i) up to approximately $0.6 million upon the initiation of defined clinical trials; (ii) $2.0 million upon regulatory approval in the United States; and (iii) $0.5 million per region upon regulatory approval in other specified regions. Additionally, if the Company or any of its sublicensees successfully commercializes any product candidate subject to the UT License Agreement, it is responsible for royalty payments in the low-single digits based upon net sales of such licensed products and payments at a percentage in the mid-teens of any sublicense income, subject to specified exceptions. The University of Texas’s right to these royalty payments will expire upon the expiration of the last patent claim subject to the UT License Agreement. During the three months ended March 31, 2020 and 2019, the Company did not incur any milestone payments. The license term extends on a product-by-product and country-by-country basis until the expiration of the last to expire of the licensed patents that covers such product in such country. Upon expiration of the royalty payment obligation, the Company will have a fully-paid license in such country. The Company may also terminate each UT License Agreement for convenience upon a specified number of days’ prior notice to the University of Texas. The University of Texas also has the right to earlier terminate the UT License Agreement after a defined date under specified circumstances where the Company has effectively abandoned its research and development efforts or has no sales. The UT License Agreement will terminate under customary termination provisions including automatic termination upon the Company’s bankruptcy or insolvency, upon notice of an uncured material breach, and upon mutual written consent. All charges incurred under the UT License Agreement have been expensed to date due to the uncertainty as to future economic benefit from the acquired rights. License Agreement with Roche Innovation Center Copenhagen A/S (formerly Santaris Pharma A/S) The Company is party to a license agreement with Santaris Pharma A/S, which subsequently changed its name to Roche Innovation Center Copenhagen A/S (“RICC”), which was acquired by F. Hoffmann-La Roche Ltd (“Roche”), in 2014. The agreement was entered into in June 2010, was amended in October 2011, amended and restated in December 2012, and further amended in August 2019 (the “RICC License Agreement”). At the time the RICC License Agreement was entered into, Roche was a minority stockholder of the Company. Under the RICC License Agreement, the Company has received exclusive and nonexclusive licenses from RICC to use specified technology of RICC (the “RICC Technology”) for specified uses, including research, development, and commercialization of pharmaceutical products using this technology worldwide. Under the RICC License Agreement, the Company has the right to develop and commercialize the RICC Technology directed to four specified targets and the option to obtain exclusive product licenses for up to six additional targets. The acquisition of Santaris Pharma A/S by Roche was considered a change of control under the RICC License Agreement, and as such, certain terms and conditions of the RICC License Agreement changed, as contemplated and in accordance with the RICC License Agreement. These changes primarily relate to milestone payments reflected in the disclosures below. If the Company exercises its option to obtain additional product licenses or to replace the target families, it will be required to make additional payments to RICC. Under the terms of the RICC License Agreement, milestone payments were previously decreased by a specified percentage as a result of the change of control by RICC referenced above. The Company is obligated to make milestone payments for each licensed product of up to $5.2 million , which is inclusive of a potential product license option fee. Certain of these milestones will be increased by a specified percentage if the Company undergoes a change of control as defined under the RICC License Agreement. If the Company grants a third party a sublicense to the RICC Technology, it is required to remit to Roche up to a specified percentage of the up-front, milestone, and other specified payments it receives under its sublicense, and if such sublicense covers use of the RICC Technology in the United States or the entire European Union, the Company will not have any further obligation to pay the fixed milestone payments noted above. During the three months ended March 31, 2020 and 2019 , the Company did not incur expense related to any milestones reached under the RICC License Agreement. If the Company or its sublicensee successfully commercializes any product candidate subject to the RICC License Agreements, then RICC is entitled to royalty payments in the mid-single digits on the net sales of such product, provided that if such net sales are made by a sublicensee under the RICC License Agreement, RICC is entitled to royalty payments equal to the lesser of a percentage in the mid-single digits on the net sales of such product or a specified percentage of the royalties paid to the Company by such sublicensee, subject to specified restrictions. The Company is obligated to make any such royalty payments until the later of: (i) a specified anniversary of the first commercial sale of the applicable product or (ii) the expiration of the last valid patent claim licensed by RICC under the RICC License Agreement underlying such product. Upon the occurrence of specified events, the royalty owed to RICC will be decreased by a specified percentage. The RICC License Agreement will terminate upon the latest of the expiration of all of RICC’s royalty rights, the termination of the last miRagen target, or the expiration of its right to obtain a product license for a new target under the RICC License Agreement. The Company may also terminate the RICC License Agreement for convenience upon a specified number of days’ prior notice to RICC, subject to specified terms and conditions. Either party may terminate the RICC License Agreement upon an uncured material breach by the other party and RICC may terminate the RICC License Agreement upon the occurrence of other specified events immediately or after such event is not cured within a specified number of days, as applicable. All charges incurred under the RICC License Agreement have been expensed to date due to the uncertainty as to future economic benefit from the acquired rights. During the three months ended March 31, 2020 and 2019, the Company did not make any payments to RICC for raw materials to be used in its drug manufacturing process. Subcontract Agreement with Yale University The Company is party to a subcontract agreement that began in October 2014 and a subaward agreement that began in March 2015 (the “Yale Agreements”) with Yale University (“Yale”), which were subsequently amended. Under the Yale Agreements, the Company is providing specified services regarding the development of a proprietary compound that targets miR-29 in the indication of idiopathic pulmonary fibrosis. Yale entered into the Yale Agreements in connection with a grant that Yale received from the National Institutes of Health (“NIH”) for the development of a miR-29 mimic as a potential therapy for pulmonary fibrosis. In consideration of the Company’s services under the Yale Agreements, Yale has agreed to reimburse the Company up to a specified amount over five years , subject to the availability of funds under the grant and continued eligibility. Under the terms of the Yale Agreements, the Company retains all rights to any and all intellectual property developed solely by the Company in connection with the Yale Agreements. Yale has also agreed to provide the Company with an exclusive option to negotiate in good faith for an exclusive, royalty-bearing license from Yale for any intellectual property developed by Yale or jointly by the parties under the Yale Agreements. Yale is responsible for filing, prosecuting, and maintaining foreign and domestic patent applications and patents on all inventions jointly developed by the parties under the Yale Agreements. Through March 31, 2020 , the Company has received $1.0 million under the Yale Agreements. The Yale Agreements terminate automatically on the date that Yale delivers its final research report to the NIH under the terms of the grant underlying the Yale Agreements. Each party may also terminate the Yale Agreements upon a specified number of days’ notice in the event that the NIH’s grant funding is reduced or terminated or upon material breach by the other party. License Agreements with the t2cure GmbH The Company is party to a license and collaboration agreement (the “t2cure Agreement”) that began in October 2010 with t2cure GmbH (“t2cure”), which was subsequently amended. Under the t2cure Agreement, the Company received a worldwide, royalty-bearing, and exclusive license to specified patent and technology rights relating to microRNA-92. In consideration of rights granted by t2cure, the Company paid an up-front fee of $46 thousand and the Company is obligated to: (i) pay an annual license maintenance fee in the amount of €3 thousand ( $3 thousand as of March 31, 2020 ); and (ii) reimburse t2cure for costs incurred in conjunction with the filing, prosecution, enforcement, and maintenance of patent rights. Under the terms of the t2cure Agreement, the Company is obligated to make the following future milestone payments for each licensed product, as defined in the t2cure Agreement: (i) up to approximately $0.7 million upon the initiation of certain defined clinical trials; (ii) $2.5 million upon regulatory approval in the United States; and (iii) up to $1.5 million per region upon regulatory approval in the European Union or Japan. Additionally, if the Company or any of its sublicensees successfully commercialize any product candidate subject to the t2cure Agreement, it is responsible for royalty payments equal to percentages in the low-single digits upon net sales of licensed products, and under specified circumstances, sublicense fees equal to a percentage in the low twenties of sublicense income received by it. The Company is obligated to make any such royalty payment until the later of: (i) the tenth anniversary of the first commercial sale of the applicable product or (ii) the expiration of the last valid claim to a patent licensed by t2cure under the t2cure Agreement covering such product. If such patent claims expire prior to the end of the ten -year term, then the royalty owed to t2cure will be decreased by a specified percentage. The Company also has the right to decrease its royalty payments by a specified percentage for royalties paid to third parties for licenses to certain third-party intellectual property. The license term extends on a country-by-country basis until the later of: (i) the tenth anniversary of the first commercial sale of a licensed product in a country and (ii) the expiration of the last to expire valid claim that claims such licensed product in such country. Upon expiration of the royalty payment obligation, the Company will have a fully-paid license in such country. The Company has the right to terminate the t2cure Agreement at will, on a country-by-country basis, after 60 days’ written notice. The t2cure Agreement will also automatically terminate upon the Company’s bankruptcy or insolvency or upon notice of an uncured material breach. All charges incurred under the t2cure Agreement have been expensed to date, due to the uncertainty as to future economic benefit from the acquired rights. Lease Obligation Payable Effective January 1, 2019, the Company adopted ASC 842 using the optional transition method provided by ASU No. 2018-11, which requires recognition of a right-of-use asset and a lease liability for all leases at the transition date, based on the present value of the lease payment over the lease term. The Company is party to a multi-year, noncancelable lease agreement that began in December 2010 for its current office and lab space. The lease agreement includes rent escalation clauses through the lease term and a Company option to extend the lease term for up to two terms of three years each. Minimum base lease payments under the lease agreement, including the impact of tenant improvement allowances, are recognized on a straight-line basis over the full term of the lease. As of March 31, 2020 , the lease was scheduled to mature on December 31, 2020, but was subsequently amended in April 2020 to extend the maturity to December 31, 2021. The Company recognized a right-of-use asset and corresponding lease liability for the lease agreement of $0.4 million as of January 1, 2020, by calculating the present value of lease payments, discounted at 6% , the Company’s estimated incremental borrowing rate, over the 12 months expected remaining term. As a result of the transition to ASC 842, the Company recorded an immaterial prior-period adjustment, as a cumulative-effect adjustment, at January 1, 2020. The interest rate implicit in the lease contract is not readily determinable and as such, the Company’s uses an incremental borrowing rate, based on prior borrowing rates, at the implementation date. This is an internally developed rate that would be incurred to borrow, with similar collateral, over the term of the lease. Amortization of the operating lease right-of-use asset, and corresponding reduction of operating lease obligation, amounted to $0.1 million for the three months ended March 31, 2020 , and was included in operating expense. As of March 31, 2020, the remaining lease term was nine months . In April 2020, the lease was amended to extend the term to December 31, 2021. During the three months ended March 31, 2020 and 2019 , lease rental expense, and the corresponding cash outflow, was approximately $0.1 million . Future minimum payments as of March 31, 2020 were approximately $0.3 million , through December 31, 2020. After giving effect to the April 2020 lease amendment, future minimum payments were approximately $0.7 million through December 31, 2021. The Company is also required to pay for operating expenses related to the leased space, which were $0.1 million for the three months ended March 31, 2020 and 2019 . The operating expenses are incurred separately and were not included in the present value of lease payments.

CAPITAL STOCK

CAPITAL STOCK	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCK Common Stock The Company is authorized to issue 105,000,000 shares of its stock, of which 100,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as preferred stock with a par value of $0.01 per share. The number of authorized shares of Common Stock may be increased or decreased by the affirmative vote of the holders of a majority of the Company’s stock who are entitled to vote. Each share of Common Stock is entitled to one vote. The holders of Common Stock are entitled to receive dividends when and as declared or paid by its board of directors. Common Stock Purchase Agreement - Aspire Capital Fund, LLC In December 2019, the Company entered into a common stock purchase agreement (“the Aspire Stock Purchase Agreement”), with Aspire Capital Fund, LLC (“Aspire Capital”), which provides that, subject to the terms, conditions, and limitations set forth therein, Aspire Capital is committed to purchase up to an aggregate of $20.0 million of shares of Common Stock over the 30 -month term of the Aspire Stock Purchase Agreement. Upon execution of the Aspire Stock Purchase Agreement, the Company sold to Aspire Capital 1,598,465 shares of Common Stock at $0.63 per share for proceeds of $1.0 million (the “Initial Purchase Shares”). As consideration for entering into the Purchase Agreement, concurrently with the execution of the Purchase Agreement and the Initial Purchase Shares, the Company issued to 959,079 shares of Common Stock to Aspire Capital as a non-refundable commitment fee, for a total issuance of 2,557,544 shares. In January 2020, the Company sold to Aspire Capital 2,200,000 shares Common Stock at a weighted-average price of $1.84 per share for proceeds of $4.1 million . As of May 8, 2020 , the Company may sell an additional $14.9 million of shares of Common Stock to Aspire Capital. Under the Aspire Stock Purchase Agreement, the Company has the right, in its sole discretion, on any trading day selected by it, and within certain specified limitations, to present Aspire Capital with a purchase notice, directing Aspire Capital (as principal) to purchase up to 200,000 shares of Common Stock per business day at a per share price equal to the lesser of (i) the lowest sale price of Common Stock on the purchase date or (ii) the average of the three lowest closing sale prices for the Common Stock during the 10 consecutive business days ending on the business day immediately preceding the purchase date. The Company also has the right to require Aspire Capital to purchase up to an additional 30% of the trading volume of the shares for the next business day at a purchase price (the “VWAP Purchase Price”), equal to the lesser of: (i) the closing sale price of the shares on the purchase date, or (ii) ninety-seven percent ( 97% ) of the next business day’s volume weighted average price (each such purchase, a “VWAP Purchase”). The Company shall have the right, in its sole discretion, to determine a maximum number of shares and set a minimum market price threshold for each VWAP Purchase. The Company can only require a VWAP Purchase if the Company has also submitted a regular purchase on the notice date for the VWAP Purchase. There are no limits on the number of VWAP purchases that the Company may require. The Aspire Stock Purchase Agreement may be terminated by the Company at any time, at the Company’s discretion, without any cost to the Company. There are no limitations on use of proceeds, financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties, or liquidated damages in the Aspire Stock Purchase Agreement. Common Stock Purchase Agreement - The Leukemia & Lymphoma Society, Inc. In August 2018 , the Company and The Leukemia & Lymphoma Society, Inc. (“LLS”) entered into a Common Stock Purchase Agreement (the “LLS Stock Purchase Agreement”), which was subsequently assigned to LLS TAP Miragen, LLC (“LLS TAP”) pursuant to an Assignment and Assumption Agreement, effective October 28, 2019 (the “Assignment Agreement”), for the sale of up to $5.0 million of shares of Common Stock to LLS and its affiliates in a private placement (the “Offering”). Under the terms of the LLS Stock Purchase Agreement, the Company may raise up to approximately $5.0 million in gross proceeds by selling shares of Common Stock to LLS and its affiliates in up to five separate closings. The initial closing of the Offering was held on August 6, 2018 . At the initial closing, the Company issued 150,987 shares of Common Stock at a price per share equal to $ 6.62 . On October 31, 2019, the Company issued an additional 606,364 shares of Common Stock to LLS TAP at a price per share of approximately $0.82 . The Company has received aggregate net proceeds of approximately $1.4 million after expenses incurred in connection with the Offering. The price per share of Common Stock to be sold in any subsequent closing will be equal to the average of the volume weighted-average prices of a share of Common Stock on the Nasdaq Capital Market for the three trading days beginning with the first trading day after the date of achievement of the relevant milestone for each such closing. Each closing is subject to the Company’s achievement of specified operational milestones under the LLS Stock Purchase Agreement and other customary closing conditions, provided, however, that each such closing must be completed prior to December 31, 2021. Based on the modifications to its Phase 2 clinical trial of cobomarsen in CTCL in December 2019, the Company does not anticipate it will achieve any of the remaining milestones under the LLS Stock Purchase Agreement. Common Stock Sales Agreement In March 2017 , the Company entered into a Common Stock Sales Agreement (the “ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its Common Stock having an aggregate offering price of up to $50.0 million through Cowen as its sales agent in an “at the market” offering. Cowen may sell the Common Stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, including without limitation sales made by means of ordinary brokers’ transactions on The Nasdaq Capital Market or otherwise at market prices prevailing at the time of sale, in block transactions, or as otherwise directed by the Company. Cowen will use commercially reasonable efforts to sell the Common Stock from time to time, based upon instructions from the Company (including any price, time, or size limits or other customary parameters or conditions the Company may impose). The Company will pay Cowen a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the ATM Agreement. The Company also has provided Cowen with customary indemnification rights. The Company is not obligated to make any sales of Common Stock under the ATM Agreement. The offering of shares of Common Stock pursuant to the ATM Agreement will terminate upon the earlier of: (i) the sale of all Common Stock subject to the ATM Agreement or (ii) termination of the ATM Agreement in accordance with its terms. During the three months ended March 31, 2020 , the Company sold, pursuant to the terms of the ATM Agreement, 975,063 shares of Common Stock, at a weighted average price of $0.72 per share, for aggregate net proceeds of approximately $0.7 million , including commissions to Cowen as sales agent. Since March 2017 and through March 31, 2020 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 2,846,449 shares of Common Stock, at a weighted average price of $4.25 per share, for aggregate net proceeds of approximately $11.6 million , including initial expenses for executing the “at the market offering” and commissions to Cowen as sales agent. Common Stock Public Offering In February 2020, the Company entered into an underwriting agreement with Oppenheimer & Co. Inc. (“Oppenheimer”) as the underwriter relating to a public offering of Common Stock, pursuant to which Oppenheimer purchased 15,000,000 shares of Common Stock and warrants to purchase 7,500,000 shares of Common Stock. Each whole warrant has an exercise price of $1.10 per share and expires on the fifth anniversary of the date of issuance. The shares of common stock and warrants were sold together as a fixed combination, each consisting of one share of Common Stock and one-half warrant, with each whole warrant exercisable to purchase one whole share of Common Stock but were issued separately and were immediately separable upon issuance. The combined price to the public in the offering for each share of Common Stock and accompanying half warrant was $1.00 , which resulted in approximately $13.9 million of net proceeds to the Company after deducting underwriting commissions and discounts and other estimated offering expenses payable by the Company and excluding the proceeds, if any, from the exercise of the warrants. Series Preferred As of March 31, 2020 , the Company had no shares of preferred stock outstanding and had not designated any class or series of preferred stock. Under the Company’s amended and restated certificate of incorporation, the Company’s board of directors has the authority to designate and issue up to 5,000,000 shares of preferred stock, at its discretion, in one or more classes or series and to fix the powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, and liquidation preferences, without further vote or action by the Company’s stockholders. WARRANTS Upon the issuance of warrants to purchase shares of common stock, the Company evaluates the terms of the warrant issue to determine the appropriate accounting and classification of the warrant issue pursuant to FASB ASC Topic 480, Distinguishing Liabilities from Equity, FASB ASC Topic 505, Equity , FASB ASC 815, Derivatives and Hedging, and ASC 718, Compensation - Stock Compensation . Warrants are classified as liabilities when the Company may be required to settle a warrant exercise in cash and classified as equity when the Company settles a warrant exercise in shares of its common stock. Liability-classified warrants are valued at fair value at the date of issue and at each reporting date pursuant to FASB ASC 820, Fair Value Measurement , and are reflected as a warrant liability on the Company’s consolidated balance sheets with the change in the warrant liability during each reporting period reflected as a gain (loss) from change in fair value of warrant liability in the consolidated statement of operations. Number of Underlying Shares (1) Weighted Average Exercise Price at March 31, 2020 Remaining Contractual Life at March 31, 2020 March 31, 2020 December 31, 2019 Liability-classified warrants Issued April 2017 11,718 11,718 $8.53 5.08 Equity-classified warrants Issued February 2020 (2) 7,500,000 — $1.10 4.86 Issued November 2017 24,097 24,097 $7.15 4.63 Acquired February 2017 — 10,707 $— — Subtotal 7,524,097 34,804 $1.12 Total warrants 7,535,815 46,522 $1.13 ____________________ (1) If the Company subdivides (by any stock split, stock dividend, recapitalization or otherwise) its outstanding shares of its common stock into a smaller number of shares, the warrant exercise price is proportionately reduced and the number of shares under outstanding warrants is proportionately increased. Additionally, if the Company combines (by combination, reverse stock split or otherwise) its outstanding shares of common stock into a smaller number of shares, the warrant exercise price is proportionately increased and the number of shares under outstanding warrants is proportionately decreased. (2) Subject to specified conditions, the Company may voluntarily reduce the warrant exercise price of the warrants issued in February 2020. A summary of the Company’s warrant activity during the three months ended March 31, 2020 is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2019 46,522 $ 17.93 Granted 7,500,000 $ 1.10 Expired (10,707 ) $ 52.50 Outstanding at March 31, 2020 7,535,815 $ 1.13 Liability-Classified Warrants Unless the warrant contract specifies otherwise, the Company uses the Black-Scholes option pricing model to determine the fair value of its warrants at the date of issue and outstanding at each reporting date. The risk-free interest rate assumption is based upon observed interest rates on zero coupon U.S. Treasury bonds commensurate with the term of the warrants. Estimated volatility is a measure of the amount by which the Company’s stock price is expected to fluctuate each year during the expected life of the warrants. Where appropriate, the Company uses the historical volatility of peer entities, due to the lack of sufficient historical data of its stock price. In connection with the 2017 merger, the Company exchanged warrants issued in 2015 for new warrants to purchase 11,718 shares of its Common Stock. These warrants have an exercise price of $8.53 per share and expire ten years from the date of issuance. The fair value of the warrants issued in April 2015, was determined by the redemption amount of $0.1 million , or $8.53 per share, as stated in the warrant contract. Equity-Classified Warrants In connection with the Company’s public offering of its Common Stock and warrants that closed in February 2020, the Company issued warrants to purchase 7,500,000 shares of its common stock at a price of $1.10 per share that expire five years from the date of issuance. The terms of the warrants include certain provisions related to fundamental transactions, a cashless exercise provision in the event registered shares are not available, and do not include any mandatory redemption provisions. Therefore, the warrants have been classified as equity with no subsequent remeasurement as long as the warrants continue to be classified as equity. In connection with the 2017 merger, the Company assumed 13,534 outstanding warrants to purchase shares of Common Stock at an exercise price of $52.50 per share. In June 2019, 2,827 of these warrants expired. The remaining 10,707 warrants expired on February 17, 2020. At issuance, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement. In connection with a debt financing in 2017, the Company issued detachable warrants to purchase up to 24,097 shares of the Company’s Common Stock at an exercise price of $7.15 per share that expire seven years from the date of issuance. At issuance, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement.

WARRANTS

WARRANTS	3 Months Ended
	Mar. 31, 2020
Other Liabilities Disclosure [Abstract]
WARRANTS	CAPITAL STOCK Common Stock The Company is authorized to issue 105,000,000 shares of its stock, of which 100,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as preferred stock with a par value of $0.01 per share. The number of authorized shares of Common Stock may be increased or decreased by the affirmative vote of the holders of a majority of the Company’s stock who are entitled to vote. Each share of Common Stock is entitled to one vote. The holders of Common Stock are entitled to receive dividends when and as declared or paid by its board of directors. Common Stock Purchase Agreement - Aspire Capital Fund, LLC In December 2019, the Company entered into a common stock purchase agreement (“the Aspire Stock Purchase Agreement”), with Aspire Capital Fund, LLC (“Aspire Capital”), which provides that, subject to the terms, conditions, and limitations set forth therein, Aspire Capital is committed to purchase up to an aggregate of $20.0 million of shares of Common Stock over the 30 -month term of the Aspire Stock Purchase Agreement. Upon execution of the Aspire Stock Purchase Agreement, the Company sold to Aspire Capital 1,598,465 shares of Common Stock at $0.63 per share for proceeds of $1.0 million (the “Initial Purchase Shares”). As consideration for entering into the Purchase Agreement, concurrently with the execution of the Purchase Agreement and the Initial Purchase Shares, the Company issued to 959,079 shares of Common Stock to Aspire Capital as a non-refundable commitment fee, for a total issuance of 2,557,544 shares. In January 2020, the Company sold to Aspire Capital 2,200,000 shares Common Stock at a weighted-average price of $1.84 per share for proceeds of $4.1 million . As of May 8, 2020 , the Company may sell an additional $14.9 million of shares of Common Stock to Aspire Capital. Under the Aspire Stock Purchase Agreement, the Company has the right, in its sole discretion, on any trading day selected by it, and within certain specified limitations, to present Aspire Capital with a purchase notice, directing Aspire Capital (as principal) to purchase up to 200,000 shares of Common Stock per business day at a per share price equal to the lesser of (i) the lowest sale price of Common Stock on the purchase date or (ii) the average of the three lowest closing sale prices for the Common Stock during the 10 consecutive business days ending on the business day immediately preceding the purchase date. The Company also has the right to require Aspire Capital to purchase up to an additional 30% of the trading volume of the shares for the next business day at a purchase price (the “VWAP Purchase Price”), equal to the lesser of: (i) the closing sale price of the shares on the purchase date, or (ii) ninety-seven percent ( 97% ) of the next business day’s volume weighted average price (each such purchase, a “VWAP Purchase”). The Company shall have the right, in its sole discretion, to determine a maximum number of shares and set a minimum market price threshold for each VWAP Purchase. The Company can only require a VWAP Purchase if the Company has also submitted a regular purchase on the notice date for the VWAP Purchase. There are no limits on the number of VWAP purchases that the Company may require. The Aspire Stock Purchase Agreement may be terminated by the Company at any time, at the Company’s discretion, without any cost to the Company. There are no limitations on use of proceeds, financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties, or liquidated damages in the Aspire Stock Purchase Agreement. Common Stock Purchase Agreement - The Leukemia & Lymphoma Society, Inc. In August 2018 , the Company and The Leukemia & Lymphoma Society, Inc. (“LLS”) entered into a Common Stock Purchase Agreement (the “LLS Stock Purchase Agreement”), which was subsequently assigned to LLS TAP Miragen, LLC (“LLS TAP”) pursuant to an Assignment and Assumption Agreement, effective October 28, 2019 (the “Assignment Agreement”), for the sale of up to $5.0 million of shares of Common Stock to LLS and its affiliates in a private placement (the “Offering”). Under the terms of the LLS Stock Purchase Agreement, the Company may raise up to approximately $5.0 million in gross proceeds by selling shares of Common Stock to LLS and its affiliates in up to five separate closings. The initial closing of the Offering was held on August 6, 2018 . At the initial closing, the Company issued 150,987 shares of Common Stock at a price per share equal to $ 6.62 . On October 31, 2019, the Company issued an additional 606,364 shares of Common Stock to LLS TAP at a price per share of approximately $0.82 . The Company has received aggregate net proceeds of approximately $1.4 million after expenses incurred in connection with the Offering. The price per share of Common Stock to be sold in any subsequent closing will be equal to the average of the volume weighted-average prices of a share of Common Stock on the Nasdaq Capital Market for the three trading days beginning with the first trading day after the date of achievement of the relevant milestone for each such closing. Each closing is subject to the Company’s achievement of specified operational milestones under the LLS Stock Purchase Agreement and other customary closing conditions, provided, however, that each such closing must be completed prior to December 31, 2021. Based on the modifications to its Phase 2 clinical trial of cobomarsen in CTCL in December 2019, the Company does not anticipate it will achieve any of the remaining milestones under the LLS Stock Purchase Agreement. Common Stock Sales Agreement In March 2017 , the Company entered into a Common Stock Sales Agreement (the “ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its Common Stock having an aggregate offering price of up to $50.0 million through Cowen as its sales agent in an “at the market” offering. Cowen may sell the Common Stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, including without limitation sales made by means of ordinary brokers’ transactions on The Nasdaq Capital Market or otherwise at market prices prevailing at the time of sale, in block transactions, or as otherwise directed by the Company. Cowen will use commercially reasonable efforts to sell the Common Stock from time to time, based upon instructions from the Company (including any price, time, or size limits or other customary parameters or conditions the Company may impose). The Company will pay Cowen a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the ATM Agreement. The Company also has provided Cowen with customary indemnification rights. The Company is not obligated to make any sales of Common Stock under the ATM Agreement. The offering of shares of Common Stock pursuant to the ATM Agreement will terminate upon the earlier of: (i) the sale of all Common Stock subject to the ATM Agreement or (ii) termination of the ATM Agreement in accordance with its terms. During the three months ended March 31, 2020 , the Company sold, pursuant to the terms of the ATM Agreement, 975,063 shares of Common Stock, at a weighted average price of $0.72 per share, for aggregate net proceeds of approximately $0.7 million , including commissions to Cowen as sales agent. Since March 2017 and through March 31, 2020 , the Company sold, pursuant to the terms of the ATM Agreement, an aggregate of 2,846,449 shares of Common Stock, at a weighted average price of $4.25 per share, for aggregate net proceeds of approximately $11.6 million , including initial expenses for executing the “at the market offering” and commissions to Cowen as sales agent. Common Stock Public Offering In February 2020, the Company entered into an underwriting agreement with Oppenheimer & Co. Inc. (“Oppenheimer”) as the underwriter relating to a public offering of Common Stock, pursuant to which Oppenheimer purchased 15,000,000 shares of Common Stock and warrants to purchase 7,500,000 shares of Common Stock. Each whole warrant has an exercise price of $1.10 per share and expires on the fifth anniversary of the date of issuance. The shares of common stock and warrants were sold together as a fixed combination, each consisting of one share of Common Stock and one-half warrant, with each whole warrant exercisable to purchase one whole share of Common Stock but were issued separately and were immediately separable upon issuance. The combined price to the public in the offering for each share of Common Stock and accompanying half warrant was $1.00 , which resulted in approximately $13.9 million of net proceeds to the Company after deducting underwriting commissions and discounts and other estimated offering expenses payable by the Company and excluding the proceeds, if any, from the exercise of the warrants. Series Preferred As of March 31, 2020 , the Company had no shares of preferred stock outstanding and had not designated any class or series of preferred stock. Under the Company’s amended and restated certificate of incorporation, the Company’s board of directors has the authority to designate and issue up to 5,000,000 shares of preferred stock, at its discretion, in one or more classes or series and to fix the powers, preferences and rights, and the qualifications, limitations, or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption, and liquidation preferences, without further vote or action by the Company’s stockholders. WARRANTS Upon the issuance of warrants to purchase shares of common stock, the Company evaluates the terms of the warrant issue to determine the appropriate accounting and classification of the warrant issue pursuant to FASB ASC Topic 480, Distinguishing Liabilities from Equity, FASB ASC Topic 505, Equity , FASB ASC 815, Derivatives and Hedging, and ASC 718, Compensation - Stock Compensation . Warrants are classified as liabilities when the Company may be required to settle a warrant exercise in cash and classified as equity when the Company settles a warrant exercise in shares of its common stock. Liability-classified warrants are valued at fair value at the date of issue and at each reporting date pursuant to FASB ASC 820, Fair Value Measurement , and are reflected as a warrant liability on the Company’s consolidated balance sheets with the change in the warrant liability during each reporting period reflected as a gain (loss) from change in fair value of warrant liability in the consolidated statement of operations. Number of Underlying Shares (1) Weighted Average Exercise Price at March 31, 2020 Remaining Contractual Life at March 31, 2020 March 31, 2020 December 31, 2019 Liability-classified warrants Issued April 2017 11,718 11,718 $8.53 5.08 Equity-classified warrants Issued February 2020 (2) 7,500,000 — $1.10 4.86 Issued November 2017 24,097 24,097 $7.15 4.63 Acquired February 2017 — 10,707 $— — Subtotal 7,524,097 34,804 $1.12 Total warrants 7,535,815 46,522 $1.13 ____________________ (1) If the Company subdivides (by any stock split, stock dividend, recapitalization or otherwise) its outstanding shares of its common stock into a smaller number of shares, the warrant exercise price is proportionately reduced and the number of shares under outstanding warrants is proportionately increased. Additionally, if the Company combines (by combination, reverse stock split or otherwise) its outstanding shares of common stock into a smaller number of shares, the warrant exercise price is proportionately increased and the number of shares under outstanding warrants is proportionately decreased. (2) Subject to specified conditions, the Company may voluntarily reduce the warrant exercise price of the warrants issued in February 2020. A summary of the Company’s warrant activity during the three months ended March 31, 2020 is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2019 46,522 $ 17.93 Granted 7,500,000 $ 1.10 Expired (10,707 ) $ 52.50 Outstanding at March 31, 2020 7,535,815 $ 1.13 Liability-Classified Warrants Unless the warrant contract specifies otherwise, the Company uses the Black-Scholes option pricing model to determine the fair value of its warrants at the date of issue and outstanding at each reporting date. The risk-free interest rate assumption is based upon observed interest rates on zero coupon U.S. Treasury bonds commensurate with the term of the warrants. Estimated volatility is a measure of the amount by which the Company’s stock price is expected to fluctuate each year during the expected life of the warrants. Where appropriate, the Company uses the historical volatility of peer entities, due to the lack of sufficient historical data of its stock price. In connection with the 2017 merger, the Company exchanged warrants issued in 2015 for new warrants to purchase 11,718 shares of its Common Stock. These warrants have an exercise price of $8.53 per share and expire ten years from the date of issuance. The fair value of the warrants issued in April 2015, was determined by the redemption amount of $0.1 million , or $8.53 per share, as stated in the warrant contract. Equity-Classified Warrants In connection with the Company’s public offering of its Common Stock and warrants that closed in February 2020, the Company issued warrants to purchase 7,500,000 shares of its common stock at a price of $1.10 per share that expire five years from the date of issuance. The terms of the warrants include certain provisions related to fundamental transactions, a cashless exercise provision in the event registered shares are not available, and do not include any mandatory redemption provisions. Therefore, the warrants have been classified as equity with no subsequent remeasurement as long as the warrants continue to be classified as equity. In connection with the 2017 merger, the Company assumed 13,534 outstanding warrants to purchase shares of Common Stock at an exercise price of $52.50 per share. In June 2019, 2,827 of these warrants expired. The remaining 10,707 warrants expired on February 17, 2020. At issuance, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement. In connection with a debt financing in 2017, the Company issued detachable warrants to purchase up to 24,097 shares of the Company’s Common Stock at an exercise price of $7.15 per share that expire seven years from the date of issuance. At issuance, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
SHARE-BASED COMPENSATION	SHARE-BASED COMPENSATION Equity Incentive Plans As of March 31, 2020 , there were 1,072,787 options outstanding and no remaining equity awards available for future issuances under the 2008 Plan. All awards granted under the 2008 Plan that, after February 13, 2017, expire or terminate for any reason prior to exercise or settlement, are forfeited, or are reacquired, withheld, or not issued to satisfy a tax withholding obligation or to satisfy the exercise price of a stock award, will become available for grant under the 2016 Plan in accordance with its terms. The 2016 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, other stock awards, and performance awards that may be settled in cash, stock, or other property. All employees and non-employee directors are eligible to participate in the 2016 Plan and may receive all types of awards other than incentive stock options. Incentive stock options may be granted under the 2016 Plan only to employees (including officers) and employees of the Company’s affiliates. The aggregate number of shares of Common Stock that may be issued under the 2016 Plan will not exceed 4,182,404 shares, which number is the sum of: (i) 1,681,294 shares, plus (ii) the number of shares subject to outstanding stock awards that were granted under the 2008 Plan, that, from and after February 13, 2017, expire or terminate for any reason prior to exercise or settlement, are forfeited because of the failure to meet a contingency or condition required to vest such shares, or are reacquired, withheld, or not issued to satisfy a tax withholding obligation in connection with an award or to satisfy the purchase price or exercise price of a stock award, if any, as such shares become available from time to time, plus (iii) shares from automatic increases to the share reserve, as described in more detail below. In accordance with the 2016 Plan, the share reserve will automatically increase on January 1 of each year, for a period of not more than ten years , commencing on January 1 of the year following the year in which the effective date of the 2016 Plan occurs, and ending on (and including) January 1, 2026, in an amount equal to 4% of the shares of Common Stock outstanding on December 31 of the preceding calendar year; however, the board of directors or compensation committee may act prior to January 1 of a given year to provide that there will be no January 1 increase in the share reserve for such year or that the increase in the share reserve for such year will be a lesser number of shares of Common Stock than would otherwise occur pursuant to the automatic increase. On January 1, 2020 , the share reserve automatically increased by 1,394,475 shares. Cumulative increases to the share reserve through January 1, 2020 consisted of 3,530,773 shares. As of March 31, 2020 , there were outstanding stock options to purchase 3,732,288 shares of Common Stock and 1,895,040 shares of Common Stock available for issuance pursuant to the terms under the 2016 Plan. Options granted under the 2008 Plan and the 2016 Plan have an exercise price equal to the market value of the Common Stock at the date of grant and expire ten years from the date of grant. Generally, options vest 25% on the first anniversary of the vesting commencement date and 75% ratably in equal monthly installments over the remaining 36 months . The Company has also granted options that vest in equal monthly or quarterly amounts over periods up to 48 months . A summary of Common Stock option activity is as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2019 3,497 $ 5.19 5.91 $ — Granted 1,778 $ 0.89 Exercised (17 ) $ 0.76 Forfeited or expired (453 ) $ 6.62 Outstanding at March 31, 2020 4,805 $ 3.48 6.93 $ — Vested or expected to vest at March 31, 2020 4,805 $ 3.48 6.93 $ — Exercisable as of March 31, 2020 2,099 $ 4.84 5.42 $ — Vested as of March 31, 2020 2,099 $ 4.84 5.42 $ — Fair Value Assumptions The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options granted under its equity compensation plans. The Black-Scholes model requires inputs for risk-free interest rate, dividend yield, volatility, and expected lives of the options. Because the Company has a limited history of stock purchase and sale activity, expected volatility is based on historical data from public companies that are similar to the Company in size and nature of operations. The Company will continue to use similar entity volatility information until its historical volatility is relevant to measure expected volatility for option grants. The Company accounts for forfeitures as they occur. The risk-free rate for periods within the contractual life of each option is based on the U.S. Treasury yield curve in effect at the time of the grant for a period commensurate with the expected term of the grant. The expected term (without regard to forfeitures) for options granted represents the period of time that options granted are expected to be outstanding and is derived from the contractual terms of the options granted and expected option-exercise behaviors. The fair value of the underlying Common Stock is based on the closing price of the Common Stock on The Nasdaq Capital Market at the date of grant. Stock Options Granted The weighted-average grant-date fair value of options granted to the Company’s employees and members of its board of directors during the three months ended March 31, 2020 and 2019 was $0.61 and $2.37 , respectively. The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Three Months Ended 2020 2019 Expected term, in years 5.90 6.36 Expected volatility 89.7 % 98.5 % Risk-free interest rate 0.9 % 2.6 % Expected dividend yield — % — % Weighted-average exercise price $ 0.89 $ 2.95 Employee Stock Purchase Plan The 2016 Employee Stock Purchase Plan (“ESPP”) allows qualified employees to purchase shares of Common Stock at a price equal to 85% of the lower of: (i) the closing price at the beginning of the offering period or (ii) the closing price at the end of the offering period. The Company expects that a new 6 -month offering period will begin each August 22 and February 22. As of March 31, 2020 , the Company had 947,793 shares available for issuance and 145,061 cumulative shares had been issued under the ESPP. Share-Based Compensation Expense Share-based compensation related to all equity awards issued pursuant to the 2008 Plan and 2016 Plan and for estimated shares to be issued under the ESPP for the purchase periods active during each respective period is included in the condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended 2020 2019 (in thousands) Research and development $ 187 $ 395 General and administrative 477 623 Total share-based compensation expense $ 664 $ 1,018 As of March 31, 2020 , the Company had $4.6 million of total unrecognized employee and non-employee share-based compensation costs, which the Company expects to recognize over a weighted-average remaining period of 2.16 years.

NET LOSS PER SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE Basic net loss per share is computed by dividing the net loss available to common stockholders by the weighted-average number of Common Stock outstanding. Diluted net loss per share is computed similarly to basic net loss per share except that the denominator is increased to include the number of additional shares of Common Stock that would have been outstanding if the potential shares of Common Stock had been issued and if the additional shares of Common Stock were dilutive. Diluted net loss per share is the same as basic net loss per share of Common Stock, as the effects of potentially dilutive securities are antidilutive. Potentially dilutive securities include the following: March 31, 2020 2019 (in thousands) Options to purchase Common Stock 4,805 4,444 Warrants to purchase Common Stock 7,536 49 Total 12,341 4,493

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS In April 2020, the Company received approximately $1.7 million in loan funding under the Paycheck Protection Program (the “PPP”), established pursuant to the recently enacted Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) and administered by the U.S. Small Business Administration (the “SBA”). The unsecured loan (the “PPP Loan”) is evidenced by a promissory note of the Company (the “Note”) in the principal amount of approximately $1.7 million , to Silicon Valley Bank (the “Bank”), the lender. Under the terms of the Note and the PPP Loan, interest accrues on the outstanding principal at the rate of 1.0% per annum. The term of the Note is two years , though it may be payable sooner in connection with an event of default under the Note. To the extent the loan amount is not forgiven under the PPP, the Company is obligated to make equal monthly payments of principal and interest. Payments of principal and interest on the PPP Loan will be deferred for the first six months of the PPP Loan term. The CARES Act and the PPP provide a mechanism for forgiveness of up to the full amount borrowed. Under the PPP, the Company may apply for and be granted forgiveness for all or part of the PPP Loan. The amount of loan proceeds eligible for forgiveness is based on a formula that takes into account a number of factors, including the amount of loan proceeds used by the Company during the eight-week period after the loan origination for certain purposes, including payroll costs, interest on certain mortgage obligations, rent payments on certain leases, and certain qualified utility payments, provided that at least 75% of the loan amount is used for eligible payroll costs. Subject to the other requirements and limitations on loan forgiveness, only loan proceeds spent on payroll and other eligible costs during the covered eight-week period will qualify for forgiveness. The Company intends to use the PPP Loan for qualifying and other related expenses. The Company can provide no assurance that it will obtain forgiveness of the PPP Loan in whole or in part. The Note may be prepaid in part or in full, at any time, without penalty. The Note provides for certain customary events of default, including (i) the Company’s failure to make a payment when due under the Note, (ii) the Company’s failure to do anything required by the Note or any other loan document, (iii) if the Company defaults on any other loan with the Bank, (iv) the Company’s failure to preserve, or account to the Bank’s satisfaction for, any of the collateral or its proceeds, (v) the Company’s failure, or anyone acting on behalf of the Company’s failure, to disclose any material fact to the Bank or the SBA, (vi) if the Company makes, or anyone acting on behalf of the Company makes, a materially false or misleading representation to the Bank or the SBA, (vii) the Company’s default on any loan or agreement with another creditor, if the Bank believes the default may materially affect the Company’s ability to pay the Note, (viii) the Company’s failure to pay any taxes when due, (ix) if the Company becomes the subject of a proceeding under any bankruptcy or insolvency law, (x) if the Company has a receiver or liquidator appointed for any part of the Company’s business or property, (xi) if the Company makes an assignment for the benefit of creditors, (xii) if the Company has any adverse change in financial condition or business operation that the Bank believes may materially affect the Company’s ability to pay the Note, (xiii) if the Company reorganizes, merges, consolidates, or otherwise changes ownership or business structure without the Bank’s prior written consent, or (xiv) if the Company becomes the subject of a civil or criminal action that the Bank believes may materially affect the Company’s ability to pay the Note. Upon the occurrence of an event of default, the Bank has customary remedies and may, among other things, require immediate payment of all amounts owed under the Note, collect all amounts owing from the Company, and file suit and obtain judgment against the Company.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2020 , or for any other interim period, or for any other future year. The balance sheet as of December 31, 2019 has been derived from audited consolidated financial statements at that date but does not include all the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements of the Company and the notes thereto contained in the Company’s Form 10-K for the year ended December 31, 2019 , filed with the SEC on March 13, 2020. The Company’s management performed an evaluation of its activities through the date of filing of these financial statements and concluded that there are no subsequent events requiring disclosure, other than as disclosed.
Going Concern	Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company’s evaluation entails, among other things, analyzing the results of the Company’s clinical development efforts, license and collaboration agreements as well as the entity’s current financial condition including conditional and unconditional obligations anticipated within a year, and related liquidity sources at the date the financial statements are issued. This is reflected in the Company’s prospective operating budgets and forecasts and compared to the current cash and cash equivalent balance.
Use of Estimates	Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with U.S. GAAP, which requires it to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and contingent liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Although these estimates are based on the Company’s knowledge of current events and actions it may take in the future, actual results may ultimately differ from these estimates and assumptions.
Revenue Recognition	Revenue Recognition The Company accounts for revenue in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 606, Revenue from Contracts with Customers (“ASC 606”). The Company enters into collaboration agreements and certain other agreements that are within the scope of ASC 606, under which the Company licenses, may license, or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such agreements. The terms of these agreements typically include payment of one or more of the following: non-refundable, up-front fees; reimbursement of research and development costs; developmental, clinical, regulatory, and commercial sales milestone payments; and royalties on net sales of licensed products. 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 Company expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized, for agreements within the scope of ASC 606, the Company performs the following five steps: (i) identification of the goods or services within the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct within the terms of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the identified performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer. The promised goods or services in the Company’s agreements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. Performance obligations are promises in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available, and whether the goods or services are integral or dependent to other goods or services in the contract. The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each agreement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical 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 collaboration and other research and development revenue in the period of adjustment. For agreements that include sales-based royalties, 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, 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 the Company’s collaboration or strategic alliance agreements. The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction, and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation. The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and 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. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.
Research and Development	Research and Development Research and development costs are expensed as incurred in performing research and development activities. The costs include employee-related expense including salaries, benefits, share-based compensation, restructuring charges, fees for acquiring and maintaining licenses under third-party license agreements, consulting fees, market research, costs of research and development activities conducted by third parties on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, and facilities and overhead costs. The Company records research and development expense in the period in which the Company receives or takes ownership of the applicable goods or when the applicable services are performed. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. The Company records up-front and milestone payments to acquire and retain contractual rights to licensed technology as research and development expenses when incurred if there is uncertainty in the Company receiving future economic benefit from the acquired contractual rights. The Company considers future economic benefits from acquired contractual rights to licensed technology to be uncertain until such a drug candidate is approved for sale by the U.S. Food and Drug Administration or when other significant risk factors are abated.
Clinical Trials and Preclinical Study Accruals	Clinical Trial and Preclinical Study Accruals The Company makes estimates of accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on certain facts and circumstances at that time. The Company’s accrued expenses for clinical trials and preclinical studies are based on estimates of costs incurred for services provided by clinical research organizations, manufacturing organizations, and other providers. Payments under the Company’s agreements with external service providers depend on a number of factors, such as site initiation, patient screening, enrollment, delivery of reports, and other events. In accruing for these activities, the Company obtains information from various sources and estimates the level of effort or expense allocated to each period. Adjustments to the Company’s research and development expenses may be necessary in future periods as its estimates change.
Restructuring and Other Charges	Restructuring and Other Charges The Company accounts for exit or disposal activities in accordance with FASB ASC Topic 420, Exit or Disposal Cost Obligations ( “ ASC 420 ” ). A business restructuring is defined as an exit or disposal activity that includes, but is not limited to, a program that is planned and controlled by management and materially changes either the scope of a business or the manner in which that business is conducted. Business restructuring charges include (i) one-time termination benefits related to employee separations, (ii) contract termination costs, and (iii) other related costs associated with exit or disposal activities including. In 2020 and 2019, t he Company implemented two phases of a restructuring plan to streamline the organization, reduce costs, and direct resources to advance the Company’s primary operating goals. The Company recognizes and measures a liability for one-time termination benefits, for which no future service is required, once the plan of termination meets all of the following criteria for an established communication date: (i) management commits to a plan of termination, (ii) the plan identifies the number of employees to be terminated and their job classifications or functions, locations and the expected completion date, (iii) the plan establishes the terms of the benefit arrangement, and (iv) it is unlikely that significant changes to the plan will be made or the plan will be withdrawn. For one-time termination benefits for which future service is required, a liability is measured at the communication date based on its value as of the termination date and recognized ratably over the future service period. The Company recognizes and measures a liability for other related costs in the period in which the liability is incurred.
Share-Based Compensation	Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees and members of its board of directors under its 2008 Equity Incentive Plan (the “2008 Plan”) and under its 2016 Equity Incentive Plan (the “2016 Plan”) by estimating the fair value of each stock option or award on the date of grant using the Black-Scholes option pricing model. The Company recognizes share-based compensation expense on a straight-line basis over the vesting term. Prior to 2019, the Company determined the value of Common Stock options issued to non-employees (other than members of its board of directors) using the Black-Scholes option pricing model and adjusting the value of such awards to current fair value each reporting period until the awards were vested or a performance commitment had otherwise been reached. After adoption of Accounting Standards Update (“ASU”) 2018-07, Compensation-Stock Compensation (Topic 718) , on January 1, 2019, non-employee stock options are valued at the award’s inception using grant-date fair value, in the same manner of stock options granted to employees. Any outstanding and partially vested non-employee stock option shares were remeasured on January 1, 2019. The adoption of this standard had an immaterial impact on the Company’s condensed consolidated financial statements.
Cash and Cash Equivalents	Cash and Cash Equivalents All highly-liquid investments that have maturities of 90 days or less at the date of purchase are classified as cash equivalents. Cash equivalents are reported at cost, which approximates fair value due to the short maturities of these instruments.
Investments	Investments The Company has designated its investments as available-for-sale securities and accounts for them at their respective fair values. The securities are classified as short-term or long-term based on the nature of the securities and their availability to meet current operating requirements. Securities that are readily available for use in current operations are classified as short-term available-for-sale securities and are reported as a component of current assets in the accompanying condensed consolidated balance sheets. Securities that are classified as available-for-sale are measured at fair value, including accrued interest, with temporary unrealized gains and losses reported as a component of stockholders’ equity until their disposition. The Company reviews available-for-sale securities at the end of each period to determine whether they remain available-for-sale based on its then current intent. The cost of securities sold is based on the specific identification method. The securities are subject to a periodic impairment review. An impairment charge would occur when a decline in the fair value of the investments below the cost basis is judged to be other-than-temporary.
Fair Value Measurements	Fair Value of Financial Instruments Certain of the Company’s financial instruments are not measured at fair value on a recurring basis but are recorded at amounts that approximate their fair value due to the short-term nature of their maturities, such as cash and cash equivalents, accounts receivable, accounts payable, and accrued expenses. The carrying amount of the Company’s note payable approximates its fair value (a Level 2 fair value measurement), reflecting interest rates currently available to the Company. The Company accounts for warrants to purchase its stock pursuant to ASC Topic 470, Debt , and ASC Topic 480, Distinguishing Liabilities from Equity , and classifies warrants for Common Stock as liabilities or equity. The warrants classified as liabilities are reported at their estimated fair value and any changes in fair value are reflected in interest and other expense. The warrants classified as equity are reported at their estimated fair value with no subsequent remeasurement Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash equivalents, which include short-term investments that have maturities of less than three months. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts. The Company invests its excess cash primarily in deposits and money market funds held with one financial institution.
Property and Equipment	Property and Equipment The Company carries its property and equipment at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the life of the lease (including any renewal periods that are deemed to be reasonably assured) or the estimated useful life of the assets. Construction in progress is not depreciated until placed in service. Repairs and maintenance costs are expensed as incurred and expenditures for major improvements are capitalized.
Operating Lease Right-of-Use Asset	Operating Lease Right-of-Use Asset The Company determines if an arrangement is, or contains, a lease at contract inception and during modifications or renewal of existing leases. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. The Company’s existing operating lease assets and liabilities were recognized upon the date of transition to ASC 842, on January 1, 2020. Going forward the Company’s operating lease assets and liabilities will be recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. The lease payments used to determine the Company’s operating lease assets may include lease incentives, stated rent increases, and escalation clauses and are recognized in the Company’s operating lease assets in the Company’s condensed consolidated balance sheets. The Company’s operating leases are reflected in operating lease right-of-use asset and operating lease liability within accrued liabilities in the Company’s consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Short-term leases, defined as leases that have a lease term of 12 months or less at the commencement date, are excluded from this treatment and are recognized on a straight-line basis over the term of the lease. Refer to Note 8. Commitments and Contingencies - Lease Obligations Payable for additional information related to the Company’s operating leases.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company assesses the carrying amount of its property and equipment whenever events or changes in circumstances indicate the carrying amount of such assets may not be recoverable.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of Common Stock outstanding during the period without consideration of Common Stock equivalents. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods, as the inclusion of all potential common shares outstanding is antidilutive.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and adjustments for the change in unrealized gains and losses on investments. Unrealized accumulated comprehensive gains or losses are reflected as a separate component in the statement of stockholders’ equity.
Income Taxes	Income Taxes The Company accounts for income taxes by using an asset and liability method of accounting for deferred income taxes. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is recorded to the extent it is more likely than not that a deferred tax asset will not be realized. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in operations in the period that includes the enactment date. The Company’s significant deferred tax assets are for net operating loss carryforwards, tax credits, accruals and reserves, and capitalized start-up costs. The Company has provided a valuation allowance for its entire net deferred tax assets since inception as, due to its history of operating losses, the Company has concluded that it is more likely than not that its deferred tax assets will not be realized. The Company has no unrecognized tax benefits. The Company classifies interest and penalties arising from the underpayment of income taxes in the condensed consolidated statements of operations and comprehensive loss as general and administrative expenses. The legislation informally titled the Tax Cuts and Jobs Act of 2017 (“Tax Act”) was signed into law on December 22, 2017. The Tax Act includes significant changes to the U.S. corporate income tax system, including: (i) a federal corporate rate reduction from 35% to 21%; (ii) limitations on the deductibility of interest expense and executive compensation; (iii) elimination of the corporate alternative minimum tax (“AMT”) and a change in how existing AMT credits can be realized; (iv) change in the rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017; (v) reduction of the orphan drug credit from 50% to 25%; and (vi) transition of U.S. international taxation from a worldwide tax system to a territorial tax system. The Tax Act did not have a material impact on the Company’s condensed consolidated financial statements primarily due to the valuation allowance recorded against its net deferred tax assets.
Segment Information	Segment Information The Company operates in one operating segment and, accordingly, no segment disclosures have been presented herein. All equipment, leasehold improvements, and other fixed assets are physically located within the United States and all agreements with the Company’s partners are denominated in U.S. dollars, except where noted.
Recent Accounting Pronouncements	Recent Accounting Pronouncements – Adopted Leases In February 2016, the FASB issued ASU No. 2016-02 , Leases (Topic 842), and subsequent amendments to the initial guidance: ASU No. 2017-13, ASU No. 2018-10, and ASU No. 2018-11 (collectively, “ASC 842”). The Company adopted ASC 842 on January 1, 2020, using the optional transition method permitted by ASU No. 2018-11. The Company’s building operating lease commitments are subject to the new standard, which resulted in an operating lease liability of $0.4 million and a right-of-use asset of $0.4 million , with no material effect on the Company’s condensed consolidated statements of operations and comprehensive loss.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. March 31, 2020 December 31, 2019 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 36,896 $ — $ 25,263 $ — U.S. treasury securities (included in short-term investments) — — 1,999 — Total assets $ 36,896 $ — $ 27,262 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 100 $ — $ 100
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	The following tables present information about the Company’s financial assets and liabilities that have been measured at fair value and indicate the fair value of the hierarchy of the valuation inputs utilized to determine such fair value. In general, fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets or liabilities. Fair value determined by Level 2 inputs utilize observable inputs other than Level 1 prices, such as quoted prices, for similar assets or liabilities, quoted market prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities. Fair values determined by Level 3 inputs are unobservable data points for the asset or liability, and include situations where there is little, if any, market activity for the asset or liability. March 31, 2020 December 31, 2019 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 36,896 $ — $ 25,263 $ — U.S. treasury securities (included in short-term investments) — — 1,999 — Total assets $ 36,896 $ — $ 27,262 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 100 $ — $ 100

RESTRUCTURING PLAN (Tables)

RESTRUCTURING PLAN (Tables)	3 Months Ended
	Mar. 31, 2020
Restructuring and Related Activities [Abstract]
Summary of Restructuring Activity	The following table summarizes the Company’s accrued restructuring liability balance and associated activity (in thousands): December 31, 2019 Additions Cash Payments March 31, 2020 Retention $ 935 $ 119 $ (935 ) $ 119 Severance and severance-related expenses 580 — (283 ) 297 Total restructuring liability $ 1,515 $ 119 $ (1,218 ) $ 416

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment, net, consisted of the following: March 31, December 31, (in thousands) Lab equipment $ 2,507 $ 2,507 Leasehold improvements 741 741 Computer hardware and software 403 457 Furniture and fixtures 166 166 Property and equipment, gross 3,817 3,871 Less: accumulated depreciation and amortization (3,374 ) (3,348 ) Property and equipment, net $ 443 $ 523

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	3 Months Ended
	Mar. 31, 2020
Payables and Accruals [Abstract]
Components of Accrued Liabilities	Accrued liabilities consisted of the following: March 31, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 1,012 $ 2,259 Accrued employee compensation and related taxes 524 508 Restructuring liability 416 1,515 Accrued legal fees and expenses 323 284 Operating lease liability 306 — Accrued other professional service fees 282 254 Value of liability-classified stock purchase warrants 100 100 Deferred and accrued facility lease obligations — 66 Accrued equipment and lab materials 11 1 Other accrued liabilities 81 121 Total accrued liabilities $ 3,055 $ 5,108

NOTES PAYABLE (Tables)

NOTES PAYABLE (Tables)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Composition of Notes Payable	Amounts outstanding under the 2017 SVB Loan Agreement were as follows: March 31, December 31, (in thousands) Principal amount outstanding $ 6,667 $ 7,667 Unamortized debt discount (27 ) (32 ) Accreted final payment fee 726 669 Total note payable 7,366 8,304 Less: current maturities (3,977 ) (3,976 ) Note payable, net of current portion $ 3,389 $ 4,328
Future Annual Minimum Principal Payments of Notes Payable	Future annual minimum principal payments under the 2017 SVB Loan Agreement as of March 31, 2020 for the respective calendar years are as follows (in thousands): 2020 $ 3,000 2021 3,667 Total $ 6,667 Future annual minimum principal payments under the 2017 SVB Loan Agreement as of March 31, 2020 (after giving effect to the amendment of the 2017 SVB Loan Agreement in April 2020), for the respective calendar years would have been as follows (in thousands): 2020 $ 1,000 2021 4,000 2022 1,667 Total $ 6,667

WARRANTS (Tables)

WARRANTS (Tables)	3 Months Ended
	Mar. 31, 2020
Other Liabilities Disclosure [Abstract]
Summary of Warrants	Number of Underlying Shares (1) Weighted Average Exercise Price at March 31, 2020 Remaining Contractual Life at March 31, 2020 March 31, 2020 December 31, 2019 Liability-classified warrants Issued April 2017 11,718 11,718 $8.53 5.08 Equity-classified warrants Issued February 2020 (2) 7,500,000 — $1.10 4.86 Issued November 2017 24,097 24,097 $7.15 4.63 Acquired February 2017 — 10,707 $— — Subtotal 7,524,097 34,804 $1.12 Total warrants 7,535,815 46,522 $1.13 ____________________ (1) If the Company subdivides (by any stock split, stock dividend, recapitalization or otherwise) its outstanding shares of its common stock into a smaller number of shares, the warrant exercise price is proportionately reduced and the number of shares under outstanding warrants is proportionately increased. Additionally, if the Company combines (by combination, reverse stock split or otherwise) its outstanding shares of common stock into a smaller number of shares, the warrant exercise price is proportionately increased and the number of shares under outstanding warrants is proportionately decreased. (2) Subject to specified conditions, the Company may voluntarily reduce the warrant exercise price of the warrants issued in February 2020. A summary of the Company’s warrant activity during the three months ended March 31, 2020 is as follows: Common Stock Warrants Number Weighted Average Exercise Price Outstanding at December 31, 2019 46,522 $ 17.93 Granted 7,500,000 $ 1.10 Expired (10,707 ) $ 52.50 Outstanding at March 31, 2020 7,535,815 $ 1.13

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock Option Activity	A summary of Common Stock option activity is as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding at December 31, 2019 3,497 $ 5.19 5.91 $ — Granted 1,778 $ 0.89 Exercised (17 ) $ 0.76 Forfeited or expired (453 ) $ 6.62 Outstanding at March 31, 2020 4,805 $ 3.48 6.93 $ — Vested or expected to vest at March 31, 2020 4,805 $ 3.48 6.93 $ — Exercisable as of March 31, 2020 2,099 $ 4.84 5.42 $ — Vested as of March 31, 2020 2,099 $ 4.84 5.42 $ —
Fair Value Assumptions for Stock Options	The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Three Months Ended 2020 2019 Expected term, in years 5.90 6.36 Expected volatility 89.7 % 98.5 % Risk-free interest rate 0.9 % 2.6 % Expected dividend yield — % — % Weighted-average exercise price $ 0.89 $ 2.95
Allocation of Share-based Compensation Expense	Share-based compensation related to all equity awards issued pursuant to the 2008 Plan and 2016 Plan and for estimated shares to be issued under the ESPP for the purchase periods active during each respective period is included in the condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended 2020 2019 (in thousands) Research and development $ 187 $ 395 General and administrative 477 623 Total share-based compensation expense $ 664 $ 1,018

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities	Potentially dilutive securities include the following: March 31, 2020 2019 (in thousands) Options to purchase Common Stock 4,805 4,444 Warrants to purchase Common Stock 7,536 49 Total 12,341 4,493

DESCRIPTION OF BUSINESS - Narra

DESCRIPTION OF BUSINESS - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (176,216)	$ (168,169)
Cash, cash equivalents and short-term investments	$ 36,100

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
U.S. treasury securities (included in short-term investments)		$ 2,000
Level 1
Assets:
Money market funds (included in cash and cash equivalents)	$ 36,896	25,263
U.S. treasury securities (included in short-term investments)	0	1,999
Total assets	36,896	27,262
Liabilities:
Common Stock warrants (included in accrued and other liabilities)	0	0
Level 3
Assets:
Money market funds (included in cash and cash equivalents)	0	0
U.S. treasury securities (included in short-term investments)	0	0
Total assets	0	0
Liabilities:
Common Stock warrants (included in accrued and other liabilities)	$ 100	$ 100

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)	3 Months Ended
	Mar. 31, 2020USD ($)segmentshares	Mar. 31, 2019USD ($)	Jan. 01, 2020USD ($)	Dec. 31, 2019USD ($)shares
Property, Plant and Equipment [Line Items]
Available-for-sale securities, cost basis				$ 2,000,000
U.S. treasury securities (included in short-term investments)				2,000,000
Unrealized loss				$ 0
Issuance of warrants (in shares) | shares	7,535,815			46,522
Impairment charges	$ 0	$ 0
Realized investment gains (losses)	0	0
Unrealized gain on investments	0	5,000
Income tax penalties and interest expense	$ 0	$ 0
Number of operating segments | segment	1
Operating lease liability	$ 306,000		$ 400,000
Operating lease right-of-use asset, net	$ 266,000		$ 400,000
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years

RESTRUCTURING PLAN - Narrative

RESTRUCTURING PLAN - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)position	Dec. 31, 2020USD ($)
Restructuring and Related Activities [Abstract]
Expected position eliminations | position	44
Expected position eliminations, percent	50.00%
Cost incurred to date	$ 2,200
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 119
Forecast
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 200

RESTRUCTURING PLAN - Rollforwar

RESTRUCTURING PLAN - Rollforward of Restructuring Reserve (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Restructuring Reserve [Roll Forward]
Beginning balance	$ 1,515
Additions	119
Cash Payments	(1,218)
Ending balance	416
Retention
Restructuring Reserve [Roll Forward]
Beginning balance	935
Additions	119
Cash Payments	(935)
Ending balance	119
Severance and severance-related expenses
Restructuring Reserve [Roll Forward]
Beginning balance	580
Additions	0
Cash Payments	(283)
Ending balance	$ 297

STRATEGIC ALLIANCE AND COLLAB_2

STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		20 Months Ended
	Feb. 28, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Jan. 01, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 828,000	$ 372,000
Amounts incurred but not yet billed		1,000		$ 300,000
Accounts receivable		4,000		108,000
Servier
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable		0
Research and development reimbursable costs
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 700,000	$ 300,000
Servier Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum reimbursements of development costs					$ 3,100,000
Incremental increase in amount	$ 1,000,000
Development and regulatory milestones					$ 60,400,000
Servier Collaboration Agreement | Milestone payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue				$ 7,500,000

PROPERTY AND EQUIPMENT - Compon

PROPERTY AND EQUIPMENT - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 3,817	$ 3,871
Less: accumulated depreciation and amortization	(3,374)	(3,348)
Property and equipment, net	443	523
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment	2,507	2,507
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	741	741
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment	403	457
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment	$ 166	$ 166

PROPERTY AND EQUIPMENT - Narrat

PROPERTY AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 68	$ 73

ACCRUED LIABILITIES - Component

ACCRUED LIABILITIES - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued outsourced clinical trials and preclinical studies	$ 1,012		$ 2,259
Accrued employee compensation and related taxes	524		508
Restructuring liability	416		1,515
Accrued legal fees and expenses	323		284
Operating lease liability	306	$ 400
Accrued other professional service fees	282		254
Value of liability-classified stock purchase warrants	100		100
Deferred and accrued facility lease obligations	0		66
Accrued equipment and lab materials	11		1
Other accrued liabilities	81		121
Total accrued liabilities	$ 3,055		$ 5,108

NOTES PAYABLE - Narrative (Deta

NOTES PAYABLE - Narrative (Details) - 2017 SVB Loan Agreement - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 30, 2017	Mar. 31, 2020	Dec. 31, 2017	Dec. 31, 2019
Debt Instrument [Line Items]
Interest margin in event of default			5.00%
Notes Payable to Banks
Debt Instrument [Line Items]
Proceeds from debt	$ 10
Repayment period	30 months
Interest-only period		18 months
Interest rate at period end		3.25%		4.75%
Final payment fee		$ 0.9

NOTES PAYABLE - Composition of

NOTES PAYABLE - Composition of Notes Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Principal amount outstanding	$ 6,667	$ 7,667
Unamortized debt discount	(27)	(32)
Accreted final payment fee	726	669
Total note payable	7,366	8,304
Less: current maturities	(3,977)	(3,976)
Note payable, net of current portion	$ 3,389	$ 4,328

NOTES PAYABLE - Future Annual M

NOTES PAYABLE - Future Annual Minimum Principal Payments (Details) $ in Thousands	Mar. 31, 2020USD ($)
2017 SVB Loan Agreement
Debt Instrument [Line Items]
2020	$ 3,000
2021	3,667
Total	6,667
Amended 2017 SVB Loan Agreement
Debt Instrument [Line Items]
2020	1,000
2021	4,000
2022	1,667
Total	$ 6,667

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Details) € in Thousands	Dec. 31, 2019EUR (€)	Dec. 31, 2019USD ($)	Oct. 31, 2010USD ($)	Mar. 31, 2020USD ($)arrangementrenewal_term	Mar. 31, 2019USD ($)	Jan. 01, 2020USD ($)
Commitments and Contingencies [Line Items]
Term of employee's base salary				3 months
Term of employee health coverage				3 months
Number of renewal terms (up to) | renewal_term				2
Renewal term				3 years
Operating lease liability				$ 306,000		$ 400,000
Lease discount rate				6.00%
Lease remaining term				12 months
Rent expense				$ 100,000	$ 100,000
Remaining lease term				9 months
Operating lease right-of-use asset, net				$ 266,000		$ 400,000
Future annual minimum payment 2020				300,000
Future lease payments due				700,000
Operating expenses of leases				$ 100,000	$ 100,000
Yale University
Commitments and Contingencies [Line Items]
Term of agreement				5 years
Proceeds from collaboration				$ 1,000,000
University of Texas
Commitments and Contingencies [Line Items]
Number of arrangements | arrangement				1
Nonrefundable upfront license documentation fee				$ 10,000
Annual license maintenance fee				10,000
Potential milestone payment for initiation of defined clinical trials (up to)				600,000
License fee expense				0
University of Texas | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval (up to)				2,000,000
University of Texas | Other Regions
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval (up to)				500,000
RICC
Commitments and Contingencies [Line Items]
Potential future milestone payments per licensed product (up to)				5,200,000
Payments for raw materials				0
t2cure
Commitments and Contingencies [Line Items]
Nonrefundable upfront license documentation fee			$ 46,000
Annual license maintenance fee	€ 3	$ 3,000
Potential milestone payment for initiation of defined clinical trials (up to)				$ 700,000
Term of agreement				10 years
Period to terminate agreement				60 days
t2cure | United States
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval (up to)				$ 2,500,000
t2cure | European Union or Japan
Commitments and Contingencies [Line Items]
Potential milestone payment for regulatory approval (up to)				$ 1,500,000
Minimum
Commitments and Contingencies [Line Items]
Resignation for good reason term				1 month
Change on control term				1 month
Maximum
Commitments and Contingencies [Line Items]
Term of employee's base salary				12 months
Term of executive’s outstanding unvested stock options				3 months
Term of employee health coverage				12 months
Resignation for good reason term				12 months
Change on control term				12 months
Chief Executive Officer
Commitments and Contingencies [Line Items]
Term of employee health coverage				12 months
Total compensation due to change in control, in base salary term				24 months

CAPITAL STOCK - Narrative (Deta

CAPITAL STOCK - Narrative (Details) $ / shares in Units, $ in Thousands	Mar. 13, 2020shares	Oct. 31, 2019USD ($)$ / sharesshares	Mar. 31, 2017	Feb. 29, 2020USD ($)$ / sharesshares	Jan. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019$ / sharesshares	Aug. 31, 2018USD ($)closing$ / sharesshares	Mar. 31, 2017USD ($)	Mar. 31, 2020USD ($)vote$ / sharesshares	Mar. 31, 2019USD ($)	Mar. 31, 2020USD ($)vote$ / sharesshares
Class of Stock [Line Items]
Shares authorized (in shares)									105,000,000		105,000,000
Common stock, shares authorized (in shares)						100,000,000			100,000,000		100,000,000
Preferred stock, shares authorized (in shares)									5,000,000		5,000,000
Common stock, par value (in dollars per share) | $ / shares						$ 0.01			$ 0.01		$ 0.01
Common Stock, Vote per Share | vote									1		1
Shares sold (in shares)									2,557,544
Proceeds from the sale of common stock and warrants | $									$ 19,754	$ 138
Number of warrants to purchase (in shares)						46,522			7,535,815		7,535,815
Warrant exercise price (in usd per share) | $ / shares						$ 17.93			$ 1.13		$ 1.13
Preferred stock outstanding (in shares)									0		0
Aspire Stock Purchase Agreement
Class of Stock [Line Items]
Amount of shares authorized to be sold (in shares)	14,900,000					20,000,000
Sale of stock, term						30 months
Shares sold (in shares)					2,200,000				1,598,465
Sale price (in usd per share) | $ / shares									$ 0.63		$ 0.63
Transaction value | $					$ 4,100				$ 1,000
Weighted-average share price (in usd per share) | $ / shares					$ 1.84
Average over number of lowest sale prices						3 days
Number of consecutive days threshold						10 days
LLS Stock Purchase Agreement
Class of Stock [Line Items]
Amount of shares authorized to be sold (in shares)							5,000,000
Shares sold (in shares)		606,364					150,987
Sale price (in usd per share) | $ / shares		$ 0.82					$ 6.62
Transaction value | $							$ 5,000
Average over number of lowest sale prices							3 days
Number of separate closings | closing							5
Aggregate offering | $		$ 1,400
ATM Agreement
Class of Stock [Line Items]
Commission fee percent			3.00%
Oppenheimer
Class of Stock [Line Items]
Amount of shares authorized to be sold (in shares)				15,000,000
Proceeds from the sale of common stock and warrants | $				$ 13,900
Number of warrants to purchase (in shares)				7,500,000
Warrant exercise price (in usd per share) | $ / shares				$ 1.1
Expiration term				5 years
Number of shares sold per each combination (in shares)				1
Number of warrants sold per each combination (in shares)				0.5
Number of securities called by each warrant or right (in shares)				1
Combined price of instruments issued per share (in dollars per share) | $ / shares				$ 1
Maximum | ATM Agreement
Class of Stock [Line Items]
Aggregate offering | $								$ 50,000
Common Stock | Aspire Stock Purchase Agreement
Class of Stock [Line Items]
Amount of shares required to be purchased (in shares)						200,000
Additional trading volume available for purchase, percent						30.00%
Price of additional share, percent of next business days' volume weighted average price						97.00%
Common Stock | ATM Agreement
Class of Stock [Line Items]
Shares sold (in shares)									975,063		2,846,449
Sale price (in usd per share) | $ / shares									$ 0.72		$ 0.72
Weighted-average share price (in usd per share) | $ / shares											$ 4.25
Proceeds from the sale of common stock and warrants | $									$ 700		$ 11,600
Aspire Capital Fund,LLC
Class of Stock [Line Items]
Shares sold (in shares)									959,079

WARRANTS - Narrative (Details)

WARRANTS - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 17, 2020	Jun. 30, 2019	Mar. 31, 2020	Feb. 29, 2020	Dec. 31, 2019	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			7,535,815		46,522
Warrant exercise price (in usd per share)			$ 1.13		$ 17.93
Expired (in shares)			10,707
2017 Merger
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			11,718		11,718
Warrant exercise price (in usd per share)			$ 8.53
Expected life (years)			10 years
Warrant liability			$ 0.1
Warrant, fair value per share (in usd per share)			$ 8.53
Issued February 2020
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			7,500,000	7,500,000	0
Warrant exercise price (in usd per share)			$ 1.10	$ 1.10
Expected life (years)				5 years
Equity-classified warrants
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			7,524,097		34,804
Warrant exercise price (in usd per share)			$ 1.12
Acquired February 2017
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			0		10,707	13,534
Warrant exercise price (in usd per share)			$ 0			$ 52.50
Expired (in shares)	10,707	2,827
Issued November 2017
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			24,097		24,097
Warrant exercise price (in usd per share)			$ 7.15
Expected life (years)			7 years

WARRANTS - Stock Warrants Outst

WARRANTS - Stock Warrants Outstanding (Details) - $ / shares	3 Months Ended
	Mar. 31, 2020	Feb. 29, 2020	Dec. 31, 2019	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	7,535,815		46,522
Weighted average exercise price (in usd per share)	$ 1.13		$ 17.93
Issued April 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	11,718		11,718
Weighted average exercise price (in usd per share)	$ 8.53
Remaining Contractual Life at March 31, 2020 (No. Years)	5 years 29 days
Equity-classified warrants
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	7,524,097		34,804
Weighted average exercise price (in usd per share)	$ 1.12
Issued February 2020 (2)
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	7,500,000	7,500,000	0
Weighted average exercise price (in usd per share)	$ 1.10	$ 1.10
Remaining Contractual Life at March 31, 2020 (No. Years)	4 years 10 months 10 days
Issued November 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	24,097		24,097
Weighted average exercise price (in usd per share)	$ 7.15
Remaining Contractual Life at March 31, 2020 (No. Years)	4 years 7 months 17 days
Acquired February 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	0		10,707	13,534
Weighted average exercise price (in usd per share)	$ 0			$ 52.50

WARRANTS - Stock Warrant Activi

WARRANTS - Stock Warrant Activity (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Number
Beginning balance (in shares) | shares	46,522
Granted (in shares) | shares	7,500,000
Expired (in shares) | shares	(10,707)
Ending balance (in shares) | shares	7,535,815
Weighted Average Exercise Price
Beginning balance (in usd per share) | $ / shares	$ 17.93
Granted (in usd per share) | $ / shares	1.10
Expired (in usd per share) | $ / shares	52,500
Ending balance (in usd per share) | $ / shares	$ 1.13

SHARE-BASED COMPENSATION - Narr

SHARE-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2016	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance (in shares)				4,182,404
Expiration period				10 years
Percent of common stock authorized under plan				4.00%
Additional shares authorized for plan (in shares)	1,394,475				3,530,773
Outstanding, exercisable equity awards (in shares)		3,732,288
Remaining equity awards available for future issuances (in shares)		1,895,040
Cash received from exercise stock options		$ 13	$ 0
Unrecognized employee stock-based compensation costs		$ 4,600
Remaining weighted-average period for RSUs		2 years 1 month 28 days
Options to purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)		4,805,000			3,497,000
Expiration period			10 years
Vesting period (up to)			48 months
Weighted average fair value per option (in usd per share)		$ 0.61	$ 2.37
Shares issued in period (in shares)		1,778,000
Options to purchase Common Stock | Initial vesting period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent			25.00%
Options to purchase Common Stock | Subsequent vesting period
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent			75.00%
Vesting period (up to)			36 months
2008 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding (in shares)		1,072,787
2016 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Basis for equity incentive plan (in shares)				1,681,294
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percentage of fair market value				85.00%
Stock purchase offering period				6 months
Number of shares available for issuance under ESPP (in shares)		947,793
Issuance of common stock for cash under employee stock purchase plan (in shares)		23,171	34,167		145,061

SHARE-BASED COMPENSATION - Stoc

SHARE-BASED COMPENSATION - Stock Option Activity (Details) - Options to purchase Common Stock - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Number of Options (in thousands)
Beginning balance (in shares)	3,497
Granted (in shares)	1,778
Exercised (in shares)	(17)
Forfeited or Expired (in shares)	(453)
Ending balance (in shares)	4,805	3,497
Vested or expected to vest (in shares)	4,805
Exercisable (in shares)	2,099
Vested (in shares)	2,099
Weighted Average Exercise Price
Beginning balance (in usd per share)	$ 5.19
Granted (in usd per share)	0.89
Exercised (in usd per share)	0.76
Forfeited or expired (in usd per share)	6.62
Ending balance (in usd per share)	3.48	$ 5.19
Vested or expected to vest (in usd per share)	3.48
Exercisable (in usd per share)	4.84
Vested (in usd per share)	$ 4.84
Weighted average remaining contractual term and Aggregate intrinsic value
Outstanding (Weighted Average Remaining Contractual Term)	6 years 11 months 5 days	5 years 10 months 28 days
Vested or expected to vest (Weighted Average Remaining Contractual Term)	6 years 11 months 5 days	5 years 10 months 28 days
Outstanding (Aggregate Intrinsic Value)	$ 0	$ 0
Vested or expected to vest (Aggregate Intrinsic Value)	$ 0	$ 0
Exercisable (Weighted Average Remaining Contractual Term)	5 years 5 months 1 day
Vested (Weighted Average Remaining Contractual Term)	5 years 5 months 1 day
Exercisable (Aggregate Intrinsic Value)	$ 0
Vested (Aggregate Intrinsic Value)	$ 0

SHARE-BASED COMPENSATION - Fair

SHARE-BASED COMPENSATION - Fair Value Assumption for Stock Options (Details) - Options to purchase Common Stock - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term, in years	5 years 10 months 24 days	6 years 4 months 8 days
Expected volatility	89.70%	98.50%
Risk-free interest rate	0.90%	2.60%
Expected dividend yield	0.00%	0.00%
Weighted-average exercise price (in usd per share)	$ 0.89	$ 2.95

SHARE-BASED COMPENSATION - Allo

SHARE-BASED COMPENSATION - Allocation of Share-based Compensation Expense on Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 664	$ 1,018
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	187	395
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 477	$ 623

NET LOSS PER SHARE - Summary of

NET LOSS PER SHARE - Summary of Potential Dilutive Securities (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	12,341	4,493
Options to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	4,805	4,444
Warrants to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	7,536	49

Subsequent Events Subsequent Ev

Subsequent Events Subsequent Events (Details) - Paycheck Protection Program Loan - Subsequent event $ in Millions	Apr. 30, 2020USD ($)
Subsequent Event [Line Items]
Loan received	$ 1.7
Interest rate	1.00%
Debt term	2 years

Uncategorized Items - mgen-2020

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (3,000)
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (3,000)