Viridian Therapeutics (VRDN) 10-Q 12 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Aug. 10, 2021
Entity Addresses [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-36483
Entity Registrant Name	Viridian Therapeutics, Inc./DE
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-1187261
Entity Address, Address Line One	203 Crescent Street, Bldg. 17, Suite 102B
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02453
City Area Code	617
Local Phone Number	272-4600
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	VRDN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in share)		9,587,155
Entity Central Index Key	0001590750
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Former Address
Entity Addresses [Line Items]
Entity Address, Address Line One	6200 Lookout Road
Entity Address, City or Town	Boulder
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80301

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 27,704	$ 45,897
Short-term investments	81,597	81,742
Prepaid expenses and other current assets	4,110	1,972
Unbilled revenue - related party	2,051	0
Total current assets	115,462	129,611
Property and equipment, net	298	309
Operating lease right-of-use asset, net	1,567	478
Other assets - related party	778	856
Other assets	97	1
Total assets	118,202	131,255
Current liabilities:
Accounts payable	2,392	670
Accrued liabilities	14,150	9,703
Current portion of deferred revenue - related party	288	301
Total current liabilities	16,830	10,674
Other liabilities - related party	1,293	501
Other liabilities	1,167	43
Total liabilities	19,290	11,218
Commitments and contingencies
Stockholders’ equity:
Preferred stock	0	0
Common stock, $0.01 par value; 200,000,000 shares authorized; 8,608,886 and 4,231,135 shares issued and outstanding as of June 30, 2021 and December 31, 2020, respectively	86	42
Additional paid-in capital	259,786	218,089
Accumulated other comprehensive loss	(12)	(8)
Accumulated deficit	(315,311)	(278,887)
Total stockholders’ equity	98,912	120,037
Total liabilities and stockholders’ equity	118,202	131,255
Series A Preferred Stock
Stockholders’ equity:
Preferred stock	$ 154,363	$ 180,801

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	8,608,886	4,231,135
Common stock, shares outstanding (in shares)	8,608,886	4,231,135
Series A Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	435,000	435,000
Preferred stock, shares issued (in shares)	340,219	398,487
Preferred stock outstanding (in shares)	340,219	398,487

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
Total revenue	$ 1,090,000	$ 168,000	$ 2,541,000	$ 996,000
Operating expenses:
Research and development	12,565,000	3,836,000	26,371,000	9,939,000
General and administrative	6,523,000	2,706,000	12,683,000	5,429,000
Total operating expenses	19,088,000	6,542,000	39,054,000	15,368,000
Loss from operations	(17,998,000)	(6,374,000)	(36,513,000)	(14,372,000)
Other income (expense):
Interest and other income	34,000	33,000	89,000	128,000
Interest and other expense	0	(94,000)	0	(235,000)
Net loss	(17,964,000)	(6,435,000)	(36,424,000)	(14,479,000)
Change in unrealized gain (loss) on investments	9,000	0	(4,000)	0
Comprehensive loss	(17,955,000)	(6,435,000)	(36,428,000)	(14,479,000)
Net loss	(17,964,000)	(6,435,000)	(36,424,000)	(14,479,000)
Net loss	$ (17,964,000)	$ (6,435,000)	$ (36,424,000)	$ (14,479,000)
Net loss per share, basic (in dollars per share)	$ (2.21)	$ (1.82)	$ (5.04)	$ (4.41)
Net loss per share, diluted (in dollars per share)	$ (2.21)	$ (1.82)	$ (5.04)	$ (4.41)
Weighted-average shares used to compute basic net loss per share (in shares)	8,106,765	3,538,490	7,226,447	3,285,123
Weighted-average shares used to compute diluted net loss per share (in shares)	8,106,765	3,538,490	7,226,447	3,285,123
Collaboration revenue - related party
Revenue:
Total revenue	$ 1,090,000	$ 0	$ 2,541,000	$ 0
Collaboration revenue
Revenue:
Total revenue	0	0	0	681,000
Grant revenue
Revenue:
Total revenue	$ 0	$ 168,000	$ 0	$ 315,000

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($)	Total	Public offering	2019 Stock purchase agreement	ATM Agreement	Adjustment From Adoption of ASC 842	Preferred StockSeries A Preferred Stock	Common Stock	Common StockPublic offering	Common Stock2019 Stock purchase agreement	Common StockATM Agreement	Additional Paid-in Capital	Additional Paid-in CapitalPublic offering	Additional Paid-in Capital2019 Stock purchase agreement	Additional Paid-in CapitalATM Agreement	Accumulated Deficit	Accumulated DeficitAdjustment From Adoption of ASC 842
Beginning balance (in shares) at Dec. 31, 2019						0	2,324,126
Beginning balance at Dec. 31, 2019	$ 15,754,000				$ (3,000)	$ 0	$ 23,000				$ 183,900,000				$ (168,169,000)	$ (3,000)
Stockholders’ deficit
Issuance of common stock, net of issuance cost (in shares)								1,000,000	146,667	65,004
Issuance of common stock, net of issuance cost		$ 13,881,000	$ 4,049,000	$ 670,000				$ 10,000	$ 2,000	$ 1,000		$ 13,871,000	$ 4,047,000	$ 669,000
Shares issued for cash upon the exercise of stock options under an equity incentive plan (in shares)							1,149
Shares issued for cash upon the exercise of stock options under an equity incentive plan	13,000										13,000
Issuance of common stock for cash under employee stock purchase plan (in shares)							1,545
Issuance of common stock for cash under employee stock purchase plan	16,000										16,000
Share-based compensation expense	664,000										664,000
Net loss	(8,044,000)														(8,044,000)
Ending balance (in shares) at Mar. 31, 2020						0	3,538,491
Ending balance at Mar. 31, 2020	27,000,000					$ 0	$ 36,000				203,180,000				(176,216,000)
Beginning balance (in shares) at Dec. 31, 2019						0	2,324,126
Beginning balance at Dec. 31, 2019	15,754,000				$ (3,000)	$ 0	$ 23,000				183,900,000				(168,169,000)	$ (3,000)
Stockholders’ deficit
Change in unrealized gain (loss) on investments	0
Net loss	(14,479,000)
Ending balance (in shares) at Jun. 30, 2020						0	3,538,491
Ending balance at Jun. 30, 2020	21,171,000					$ 0	$ 36,000				203,786,000				(182,651,000)
Beginning balance (in shares) at Mar. 31, 2020						0	3,538,491
Beginning balance at Mar. 31, 2020	27,000,000					$ 0	$ 36,000				203,180,000				(176,216,000)
Stockholders’ deficit
Issuance of common stock and warrants in a public offering, net of issuance costs		$ (17,000)										$ (17,000)
Share-based compensation expense	623,000										623,000
Change in unrealized gain (loss) on investments	0
Net loss	(6,435,000)														(6,435,000)
Ending balance (in shares) at Jun. 30, 2020						0	3,538,491
Ending balance at Jun. 30, 2020	21,171,000					$ 0	$ 36,000				203,786,000				(182,651,000)
Beginning balance (in shares) at Dec. 31, 2020						398,487	4,231,135
Beginning balance at Dec. 31, 2020	120,037,000					$ 180,801,000	$ 42,000				218,089,000				(278,887,000)
Stockholders’ deficit
Issuance of common stock upon the conversion of convertible preferred stock (in shares)						(43,664)	2,911,071
Issuance of common stock upon the conversion of convertible preferred stock	0					$ (19,811,000)	$ 29,000				19,782,000
Issuance of common stock upon exercise of warrants (in shares)							56,935
Issuance of common stock upon exercises of warrants	940,000						$ 1,000				939,000
Issuance of common stock for exercises of stock options and vesting of restricted stock units (in shares)							31,249
Issuance of common stock for exercises of stock options and vesting of restricted stock units	307,000										307,000
Issuance of common stock for cash under employee stock purchase plan (in shares)							980
Issuance of common stock for cash under employee stock purchase plan	12,000										12,000
Share-based compensation expense	3,175,000										3,175,000
Change in unrealized gain (loss) on investments	(13,000)
Net loss	(18,460,000)														(18,460,000)
Ending balance (in shares) at Mar. 31, 2021						354,823	7,231,370
Ending balance at Mar. 31, 2021	105,998,000					$ 160,990,000	$ 72,000				242,304,000				(297,347,000)
Beginning balance (in shares) at Dec. 31, 2020						398,487	4,231,135
Beginning balance at Dec. 31, 2020	120,037,000					$ 180,801,000	$ 42,000				218,089,000				(278,887,000)
Stockholders’ deficit
Change in unrealized gain (loss) on investments	(4,000)
Net loss	(36,424,000)
Ending balance (in shares) at Jun. 30, 2021						340,219	8,608,886
Ending balance at Jun. 30, 2021	98,912,000					$ 154,363,000	$ 86,000				259,786,000				(315,311,000)
Beginning balance (in shares) at Mar. 31, 2021						354,823	7,231,370
Beginning balance at Mar. 31, 2021	105,998,000					$ 160,990,000	$ 72,000				242,304,000				(297,347,000)
Stockholders’ deficit
Issuance of common stock upon the conversion of convertible preferred stock (in shares)						(14,604)	973,648
Issuance of common stock upon the conversion of convertible preferred stock	0					$ (6,627,000)	$ 10,000				6,617,000
Issuance of common stock, net of issuance cost (in shares)										403,868
Issuance of common stock, net of issuance cost				$ 7,052,000						$ 4,000				$ 7,048,000
Share-based compensation expense	3,817,000										3,817,000
Change in unrealized gain (loss) on investments	9,000
Net loss	(17,964,000)														(17,964,000)
Ending balance (in shares) at Jun. 30, 2021						340,219	8,608,886
Ending balance at Jun. 30, 2021	$ 98,912,000					$ 154,363,000	$ 86,000				$ 259,786,000				$ (315,311,000)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (36,424,000)	$ (14,479,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	6,992,000	1,287,000
Other non-cash lease expenses	(1,200,000)	131,000
Depreciation and amortization	58,000	132,000
Loss on sale of equipment	67,000	0
Amortization of premiums and discounts on available-for-sale securities	481,000	281,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,156,000)	622,000
Unbilled revenue - related party	(2,051,000)	0
Deferred revenue - related party	779,000	0
Accounts payable	1,601,000	(810,000)
Accrued and other liabilities	5,683,000	(2,412,000)
Net cash used in operating activities	(26,170,000)	(15,248,000)
Cash flows from investing activities:
Purchases of short-term investments	(67,381,000)	0
Maturities of short-term investments	67,042,000	2,000,000
Purchases of property and equipment	(69,000)	0
Proceeds from sale of property and equipment	75,000	1,000
Net cash provided by (used in) investing activities	(333,000)	2,001,000
Cash flows from financing activities:
Proceeds from the issuance of common stock	8,529,000	19,783,000
Payment of issuance costs associated with the sale of common stock	(218,000)	(1,193,000)
Payments of principal of notes payable	0	(1,333,000)
Proceeds from the issuance of notes payable	0	1,726,000
Net cash provided by financing activities	8,311,000	18,983,000
Net increase (decrease) in cash and cash equivalents	(18,192,000)	5,736,000
Cash and cash equivalents at beginning of period	45,897,000	24,846,000
Cash and cash equivalents at end of period	27,704,000	30,582,000	$ 24,846,000
Supplemental disclosure of cash flow information
Cash paid for interest	0	145,000
Supplemental disclosure of non-cash investing and financing activities
Purchase of property and equipment in accounts payable	120,000	0
Unpaid common stock issuance costs included in current liabilities	0	19,000
Change in unrealized loss on investments	(4,000)	0
Amortization of public offering costs	$ 0	$ 30,000
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201602Member

DESCRIPTION OF BUSINESS

DESCRIPTION OF BUSINESS	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS	DESCRIPTION OF BUSINESS Viridian Therapeutics, Inc., a Delaware corporation (the “Company” or “Viridian”), is a biotechnology company advancing new treatments for patients with diseases that are underserved by current therapies. The Company’s most advanced program, VRDN-001, is a differentiated intravenously administered IGF-1R monoclonal antibody being developed for thyroid eye disease, a debilitating condition caused by an autoimmune reaction that causes the immune system to attack tissues in the orbital socket. Agreement and Plan of Merger On October 27, 2020, the Company acquired a private company, Viridian Therapeutics, Inc. (“Private Viridian”) in accordance with the terms of the Agreement and Plan of Merger, dated October 27, 2020 (the “Merger Agreement”). Pursuant to the Merger Agreement, Oculus Merger Sub I, Inc., a Delaware corporation and a wholly-owned subsidiary of the Company (“First Merger Sub”), merged with and into Private Viridian, pursuant to which Private Viridian was the surviving corporation and became a wholly-owned subsidiary of the Company (the “First Merger”). Immediately following the First Merger, Private Viridian merged with and into Oculus Merger Sub II, LLC, a Delaware limited liability company and wholly-owned subsidiary of the Company (“Second Merger Sub”), pursuant to which Second Merger Sub was the surviving entity (together with the First Merger, the “Merger”). The Merger is intended to qualify as a tax-free reorganization for U.S. federal income tax purposes. On October 27, 2020, the Company completed a short-form merger under which the Second Merger Sub merged with Viridian Therapeutics, Inc (then Miragen Therapeutics, Inc.) pursuant to which Viridian Therapeutics, Inc. was the surviving entity. Under the terms of the Merger Agreement, at the closing of the Merger, the Company issued 72,131 shares of the Company’s common stock (“Common Stock”) and 203,197 shares of Series A Non-Voting Convertible Preferred Stock (the “Series A Preferred Stock”) to securityholders of Private Viridian. Each share of Series A Preferred Stock is convertible into 66.67 shares of Common Stock, subject to certain conditions described below. Private Placement and Securities Purchase Agreement Concurrent with the acquisition of Private Viridian, on October 27, 2020, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with the purchasers named therein, pursuant to which the Company sold an aggregate of approximately 195,290 shares of Series A Preferred Stock for an aggregate purchase price of approximately $91.0 million (collectively, the “Financing”). Each share of Series A Preferred Stock is convertible into 66.67 shares of Common Stock, as described below. The powers, preferences, rights, qualifications, limitations, and restrictions applicable to the Series A Preferred Stock are set forth in the Certificate of Designation filed in connection with the Financing. Holders of Series A Preferred Stock are entitled to receive dividends on shares of Series A Preferred Stock equal, on an as-if-converted-to-Common-Stock basis, and in the same form as dividends actually paid on shares of the Common Stock. Except as otherwise required by law, the Series A Preferred Stock does not have voting rights. However, as long as any shares of Series A Preferred Stock are outstanding, the Company will not, without the affirmative vote of the holders of a majority of the then outstanding shares of the Series A Preferred Stock, (a) alter or change adversely the powers, preferences or rights given to the Series A Preferred Stock, (b) alter or amend the Certificate of Designation, (c) amend its certificate of incorporation or other charter documents in any manner that adversely affects any rights of the holders of Series A Preferred Stock, (d) increase the number of authorized shares of Series A Preferred Stock, (e) at any time while at least 30% of the originally issued Series A Preferred Stock remains issued and outstanding, consummate a Fundamental Transaction (as defined in the Certificate of Designation) or (f) enter into any agreement with respect to any of the foregoing. The Series A Preferred Stock does not have a preference upon any liquidation, dissolution, or winding-up of the Company. Following stockholder approval of the conversion of the Series A Preferred Stock into shares of Common Stock in December 2020, each share of Series A Preferred Stock became convertible into 66.67 shares of Common Stock at any time at the option of the holder thereof, subject to certain limitations, including that a holder of Series A Preferred Stock is prohibited from converting shares of Series A Preferred Stock into shares of Common Stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than a specified percentage (to be established by the holder between 4.99% and 19.99%) of the total number of shares of Common Stock issued and outstanding immediately after giving effect to such conversion. As of June 30, 2021, 58,268 shares of Series A Preferred Stock had been converted into 3,884,719 shares of Common Stock. The shares of Common Stock sold to investors in the Financing were registered for resale pursuant to a registration statement, which was declared effective by the SEC on December 22, 2020. Liquidity The accompanying condensed consolidated financial statements have been prepared on a basis that assumes the Company is a going concern and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classifications of liabilities that may result from any uncertainty related to its ability to continue as a going concern. The Company has funded its operations to date principally through proceeds received from the sale of the Company’s Common Stock, its Series A Preferred Stock, and other equity securities, debt financings, license fees, and reimbursements received under collaboration agreements. Since its inception and through June 30, 2021, the Company has generated an accumulated deficit of $315.3 million. The Company expects to continue to generate operating losses in the foreseeable future. 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. 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 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 development programs and efforts to achieve regulatory approval. As of June 30, 2021, the Company had approximately $109.3 million in cash, cash equivalents, and short-term investments. As of the issuance date of these condensed consolidated financial statements, the Company expects that its current resources will be sufficient to fund its operations into 2024. The Company will continue to require additional capital in order to continue to finance 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

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Viridian Therapeutics Europe Limited and Viridian Therapeutics S.à.r.l., each of which were formed for the sole purpose of submitting regulatory filings in Europe. The Company’s subsidiaries have no employees or operations. The condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. All significant intercompany balances have been eliminated in consolidation. The Company’s management performed an evaluation of its activities through the date of filing of these condensed consolidated financial statements and concluded that there are no subsequent events requiring disclosure, other than as disclosed. Risk and Uncertainties – Impact of the COVID-19 Pandemic The Company is subject to risks and uncertainties as a result of the ongoing COVID-19 pandemic. The virus continues to spread globally and has been declared a pandemic by the World Health Organization. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world. The spread of COVID-19 has caused the Company to modify its business practices, including implementing a work-from-home policy for all employees who are able to perform their duties remotely and restricting all nonessential travel, and it expects to continue to take actions as may be required or recommended by government authorities or as the Company determines are in the best interests of its employees, the patients it serves, and other business partners in light of COVID-19. Potential impacts to the Company’s business include temporary closures of its facilities or those of its vendors, disruptions or restrictions on its employees’ ability to travel, disruptions to or delays in ongoing laboratory experiments and operations, and the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, and its ability to raise capital. As of June 30, 2021, there have been no material impacts to the Company as a result of the COVID-19 pandemic. The Company continually assesses the impacts of COVID-19 and the extent to which the pandemic may materially impact the Company’s financial condition, liquidity, or results of operations in the future is uncertain. 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, such as contract research organizations and contract manufacturing operations, on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, non-clinical activities, regulatory operations, 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. Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees, members of its board of directors, and non-employees under its 2008 Equity Incentive Plan (the “2008 Plan”), its amended and restated 2016 Equity Incentive Plan (the “2016 Plan”), and the 2020 Equity Incentive Plan (the “2020 Plan”) (collectively, the “Equity Incentive Plans”) 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. 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. 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 utilizes 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. June 30, 2021 December 31, 2020 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 27,693 $ — $ 45,960 $ — U.S. treasury securities (included in short-term investments) 81,597 — 81,742 — Total assets $ 109,290 $ — $ 127,702 $ — 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 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 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 on January 1, 2020, the date of transition to Accounting Standards Update (“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”). After January 1, 2020, the Company’s operating lease assets and liabilities are 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 and other liabilities in the Company’s condensed 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. Convertible Preferred Stock The Company records shares of non-voting convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The Company has applied the guidance in ASC 480-10-S99-3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities , and at issuance classified the Series A Preferred Stock outside of stockholders’ equity because, if convertibility of Series A Preferred Stock into Common Stock was not approved by the stockholders, the Series A Preferred Stock would be redeemable at the option of the holders for cash equal to the closing price of the Common Stock on last trading day prior to the holder’s redemption request. On December 31, 2020, the stockholders approved the convertibility of the Series A Preferred Stock into Common Stock and as such, the Company reclassified the Series A Preferred Stock to permanent equity. 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 and six months ended June 30, 2021 and 2020. 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 condensed consolidated statements of changes in stockholders’ equity. The Company had an unrealized gain and loss of $9.0 thousand and $4.0 thousand during the three and six months ended June 30, 2021, respectively. The Company had no realized or unrealized gains or losses during the three and six months ended June 30, 2020. 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 and six months ended June 30, 2021 and 2020. 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 condensed consolidated balance sheets. Any changes in the warrant liability during each reporting period would be reflected as other expense in the condensed consolidated statement of operations and comprehensive loss. 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 – To Be Adopted From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company does not believe that the adoption of recently issued standards have or may have a material impact on the Company’s consolidated financial statements or disclosures.

ACQUISITION OF PRIVATE VIRIDIAN

ACQUISITION OF PRIVATE VIRIDIAN	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
ACQUISITION OF PRIVATE VIRIDIAN	ACQUISITION OF PRIVATE VIRIDIAN On October 27, 2020, the Company completed its acquisition of Private Viridian in accordance with the terms of the Merger Agreement as discussed in Note 1. Description of Business. Under the terms of the Merger Agreement, the Company issued 72,131 shares of Common Stock and 203,197 shares of Series A Preferred Stock. Each share of Series A Preferred Stock is convertible into 66.67 shares of Common Stock, subject to certain conditions. The Company concluded that the acquisition of Private Viridian did not result in the acquisition of a business, as substantially all of the fair value of the non-monetary assets acquired was concentrated in a single identifiable asset, the exclusive license agreement with ImmunoGen, which includes the Company’s lead program VRDN-001. The Company determined that the cost to acquire the assets was $97.4 million, based on the fair value of the equity consideration issued and including direct costs of the acquisition of $2.0 million. The net assets acquired in connection with the Merger were recorded at their estimated fair values as of October 27, 2020, the date the Merger was completed. The following table summarizes the net assets acquired based on their estimated fair values as of October 27, 2020 (in thousands): Acquired IPR&D $ 69,861 Cash and cash equivalents 29,371 Accrued liabilities (1,843) Net acquired tangible assets $ 97,389 In the estimation of fair value of the asset purchase consideration, the Company used the carrying value of the cash and cash equivalents and accrued liabilities as the most reliable indicator of fair value based on the associated short-term nature of the balances. The remaining fair value was attributable to the acquired in-process research and development (“IPR&D”). As the asset had not yet received regulatory approval in any territory, the cost attributable to the license agreement was expensed in the Company’s condensed consolidated statements of operations and comprehensive loss for the year ended December 31, 2020, as the acquired IPR&D had no alternative future use, as determined by the Company in accordance with U.S. GAAP.

COLLABORATION AGREEMENTS

COLLABORATION AGREEMENTS	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
COLLABORATION AGREEMENTS	COLLABORATION AGREEMENTS License Agreement with Zenas BioPharma In October 2020, Private Viridian entered a license agreement with Zenas BioPharma (Cayman) Limited (“Zenas BioPharma”) to license technology comprising certain materials, patent rights, and know-how to Zenas BioPharma. On October 27, 2020, in connection with the closing of the Private Viridian acquisition, the Company became party to the license agreement with Zenas BioPharma. Since February 2021, the Company has entered into several letter agreements with Zenas BioPharma pursuant to which the Company agreed to provide assistance to Zenas BioPharma with certain development activities, including manufacturing. The license agreement and subsequent letter agreements (collectively, the “Zenas Agreements”) were negotiated with a single commercial objective and are treated as a combined contract for accounting purposes. Under the terms of the Zenas Agreements, the Company granted Zenas BioPharma an exclusive license to develop, manufacture, and commercialize certain IGF-1R directed antibody products for non-oncology indications in the greater area of China. As consideration for the Zenas Agreements, the transaction price included upfront non-cash consideration and variable consideration in the form of payment for the Company’s goods and services and milestone payments due upon the achievement of specified events. Under the Zenas Agreements, the Company can receive non-refundable milestone payments upon achieving specific milestone events during the contract term. Additionally, the Company may receive royalty payments based on a percentage of the annual net sales of any licensed products sold on a country-by-country basis in the greater area of China. The royalty percentage may vary based on different tiers of annual net sales of the licensed products made. Zenas BioPharma is obligated to make royalty payments to the Company for the royalty term in the Zenas Agreements. The Zenas Agreements would qualify as a collaborative arrangement under the scope of Accounting Standards Codification, Topic 808, Collaborative Arrangements (“ASC 808”). While this arrangement is in the scope of ASC 808, the Company applied ASC 606 to account for certain aspects of this arrangement. The Company applied ASC 606 for certain activities within the arrangement associated with the Company’s transfer of a good or service (i.e., a unit of account) that is part of the Company’s ongoing major or central operations. The Company allocated the transaction price 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 cost. The Company’s license of goods and services to Zenas BioPharma during the contract term was determined to be a single performance obligation satisfied over time. The Company will recognize the transaction price from the license agreement over the Company’s estimated period to complete its activities. At the inception of the arrangement, the Company evaluated whether the milestones were considered probable of being reached and estimated the amount to be included in the transaction price using the most likely amount method. As it was not probable that a significant revenue reversal would not occur, none of the associated milestone payments were included in the transaction price at contract inception. For the sales-based royalties included in the arrangement, the license was deemed to be the predominant item to which the royalties relate. The Company will recognize royalty revenues 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). During the three and six months ended June 30, 2021, the Company recognized $1.1 million and $2.5 million, respectively, of collaboration revenue related to the Zenas Agreements. As of June 30, 2021 and December 31, 2020, the Company had deferred revenue balances of $1.6 million and $0.8 million, respectively, and accounts receivable balances of $1.4 million and $9 thousand , respectively, with the Zenas Agreements, which are reported in the condensed consolidated balance sheets as current portion of deferred revenue - related party and other liabilities - related party. The Zenas Agreements may be considered related party transactions because Tellus BioVentures, LLC (“Tellus BioVentures”), a 5% or greater stockholder of the Company (on an as-converted basis, assuming only shares of Series A Preferred Stock held by Tellus BioVentures are converted into shares of Common Stock), is also a 5% or greater stockholder of Zenas BioPharma and has a seat on Zenas BioPharma’s board of directors. Servier License and Collaboration Agreement In 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, with such termination becoming 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 two Phase 1 clinical trials of a legacy product candidate. The activities for which the Company was eligible for reimbursement under the Servier Collaboration Agreement were considered a research and development performance obligation and revenue was recognized in accordance with ASC 606 through the termination date. 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 several performance obligations under the Servier Collaboration Agreement and allocated the transaction price to these 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 the transfer of materials is 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. During the three and six months ended June 30, 2020, the Company recognized $0.0 million and $0.7 million of collaboration revenue under the Servier Collaboration Agreement, respectively. As the Servier Collaboration Agreement was terminated in February 2020, no revenue was recorded under the Servier Collaboration Agreement subsequent to March 31, 2020.

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	6 Months Ended
	Jun. 30, 2021
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	PROPERTY AND EQUIPMENT Property and equipment, net, consisted of the following: June 30, December 31, (in thousands) Lab equipment $ 753 $ 2,509 Leasehold improvements 741 741 Computer hardware and software 389 336 Furniture and fixtures 165 166 Property and equipment, gross 2,048 3,752 Less: accumulated depreciation and amortization (1,750) (3,443) Property and equipment, net $ 298 $ 309 During the quarter ended March 31, 2021, certain lab equipment associated with legacy microRNA programs met the criteria to be classified and were reclassified as held for sale and included in prepaid expenses and other current assets. The assets held for sale totaled $142 thousand , which was the net book value on the date of transfer. During the quarter ended June 30, 2021, the Company sold the equipment, received proceeds of approximately $75 thousand and recorded a loss of approximately $67 thousand. During the three and six months ended June 30, 2021, and 2020, depreciation and amortization expense was $25 thousand and $58 thousand, respectively, and $64 thousand and $132 thousand, respectively. Depreciation

ACCRUED LIABILITIES

ACCRUED LIABILITIES	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
ACCRUED LIABILITIES	ACCRUED LIABILITIES Accrued liabilities consisted of the following: June 30, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 10,314 $ 5,400 Accrued employee compensation and related taxes 2,566 1,963 Operating lease liability 412 455 Accrued legal fees and expenses 88 380 Accrued other professional service fees 278 796 Value of liability-classified stock purchase warrants 100 100 License agreement liability 177 86 Other accrued liabilities 215 523 Total accrued liabilities $ 14,150 $ 9,703

NOTES PAYABLE

NOTES PAYABLE	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
NOTES PAYABLE	NOTES PAYABLE 2017 Silicon Valley Bank Loan Agreement In November 2017, the Company entered into a loan and security agreement with Silicon Valley Bank (the “2017 SVB Loan Agreement”). Upon entry into the 2017 SVB Loan Agreement, the Company borrowed $10.0 million bearing interest at the prime rate 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 the maturity date by an additional six months. On December 18, 2020, the Company repaid the full outstanding loan balance, including accrued interest and a final payment fee equal to $0.9 million that was due upon maturity. As of June 30, 2021 and December 31, 2020, no additional amounts were outstanding under the 2017 SVB Loan Agreement. Paycheck Protection Program Loan In April 2020, the Company received approximately $1.7 million in loan funding under the Paycheck Protection Program (the “PPP”), which was established pursuant to the recently enacted Coronavirus Aid, Relief, and Economic Security Act and is administered by the U.S. Small Business Administration. The unsecured loan (the “PPP Loan”) was 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”). Under the terms of the Note and the PPP Loan, interest accrued on the outstanding principal at the rate of 1.0% per annum. On December 18, 2020, the PPP Loan, including accrued interest, was repaid to the Bank. As of June 30, 2021 and December 31, 2020, there were no amounts outstanding under the PPP Loan.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES License Agreement with ImmunoGen, Inc. On October 27, 2020, in connection with the closing of the Private Viridian acquisition, the Company became party to a license agreement (the “ImmunoGen License Agreement”) with Immunogen, Inc. (“ImmunoGen”), under which the Company obtained an exclusive, sublicensable, worldwide license to certain patents and other intellectual property rights to develop, manufacture, and commercialize certain products for non-oncology and non-radiopharmaceutical indications. In consideration for rights granted by ImmunoGen, the Company is obligated to make certain development milestone payments of up to $48.0 million. Additionally, if the Company successfully commercializes any product candidate subject to the ImmunoGen License Agreement, it is responsible for royalty payments equal to a percentage in the mid-single digits of net sales and commercial milestone payments of up to $95.0 million. The Company is obligated to make any such royalty payments on a product-by-product and country-by-country basis from the first commercial sale of a specified product in each country until the later of (i) the expiration of the last patent claim subject to the ImmunoGen License Agreement in such country, (ii) the expiration of any applicable regulatory exclusivity obtained for each product in such country, or (iii) the 12th anniversary of the date of the first commercial sale of such product in such country. License Agreement with Xencor, Inc. On December 16, 2020, the Company entered into a license agreement (the “Xencor License Agreement”) with Xencor, Inc. (“Xencor”), under which Xencor granted the Company rights to an exclusive, worldwide, sublicensable, non-transferable, royalty-bearing license to use specified Xencor technology for the research, development, manufacturing, and commercialization of therapeutic antibodies targeting IGF-1R indications. In consideration for rights granted by Xencor, the Company issued 322,407 shares of its Common Stock in December 2020. The shares were valued at $6.0 million and recorded as research and development expense in 2020. Under the terms of the Xencor License Agreement, the Company is obligated to make future development milestone payments of up to $30.0 million. Additionally, if the Company successfully commercializes any product candidate subject to the Xencor License Agreement, it is responsible for royalty payments equal to a percentage in the mid-single digits of net sales and commercial milestone payments of up to $25.0 million. The Company is obligated to make any such royalty payments on a product-by-product and country-by-country basis from the first commercial sale of products containing the licensed technology in each country until the later of (i) the expiration of the last patent claim subject to the Xencor License Agreement in such country, (ii) the expiration of any applicable regulatory exclusivity obtained, or (iii) the 12 th anniversary of the date of the first commercial sale. Contingent Value Rights Agreement Pursuant to the Merger Agreement, on November 4, 2020, the Company and the Rights Agent (as defined therein) executed a contingent value rights agreement (the “CVR Agreement”), pursuant to which each holder of Common Stock as of November 6, 2020, other than former stockholders of Private Viridian, is entitled to one contractual contingent value right issued by the Company, subject to and in accordance with the terms and conditions of the CVR Agreement, for each share of Common Stock held by such holder. Each contingent value right entitles the holder thereof to receive certain cash payments equal to 80% of the net proceeds, if any, related to the disposition of the Company’s legacy programs to develop product candidates that modulate microRNAs within five years following the date of the Merger. The contingent value rights are not transferable, except in certain limited circumstances as provided in the CVR Agreement, will not be certificated or evidenced by any instrument, and will not be registered with the SEC or listed for trading on any exchange. Lease Obligations The Company is party to a multi-year, noncancelable lease agreement for its Colorado-based 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. The lease term was amended in March 2021 to extend the lease maturity date to December 31, 2024. Upon adoption of ASC 842 and upon subsequent modification of the lease in 2020 and in March 2021, the Company recognized a right-of-use asset and corresponding lease liability for the lease agreement of approximately $1.6 million 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. In April 2021, the Company entered into a sublease with Cogent Biosciences, Inc. (“Cogent”) for its Colorado-based office and lab space. As of the sublease inception date, Fairmount Funds Management LLC beneficially owned more than 5% of the Company’s Common Stock and Cogent’s capital stock. Under the terms of the nine-month sublease, which expires on December 31, 2021, Cogent will pay the Company an aggregate of $0.1 million in rent payments plus related taxes and lease operating costs. The sublease was negotiated on an arm’s-length basis and is a market-rate transaction on terms that the Company believes are no less favorable than would have been reached with an unrelated third party. In connection with the acquisition of Private Viridian, the Company became party to a multi-year, noncancelable lease agreement in October 2020 for its Massachusetts-based office space. The lease agreement included rent escalation clauses through the lease term. Minimum base lease payments under the lease agreement are recognized on a straight-line basis over the full term of the lease. As of June 30, 2021, the lease was scheduled to mature on February 28, 2023. Upon assumption of the lease, the Company recognized a right-of-use asset and corresponding lease liability for the lease agreement of $0.7 million by calculating the present value of lease payments, discounted at 6%, the Company’s estimated incremental borrowing rate, over the expected remaining term. Consolidated future minimum lease payments as of June 30, 2021 were approximately $1.8 million through December 31, 2024. As of June 30, 2021, the Company’s operating lease obligations were reflected as operating lease liabilities of $412 thousand as accrued liabilities other liabilities

CAPITAL STOCK

CAPITAL STOCK	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCK Common Stock Under the Company’s amended and restated certificate of incorporation, the Company is authorized to issue 205,000,000 shares of its stock, of which 200,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as Preferred Stock, both 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 Sales Agreements Jefferies LLC In April 2021, the Company entered into an Open Market Sale Agreement SM (the “2021 ATM Agreement”) with Jefferies LLC (“Jefferies”) under which the Company could 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 Jefferies as its sales agent in an “at the market” offering. Jefferies will receive a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Jefferies under the 2021 ATM Agreement. Through June 30, 2021, the Company sold an aggregate of 403,868 shares of Common Stock pursuant to the terms of the 2021 ATM Agreement, at a weighted-average price of $18.00 per share, for aggregate net proceeds of approximately $7.1 million, including commissions to Jefferies as sales agent. Cowen and Company, LLC In March 2017, the Company entered into a Common Stock Sales Agreement (the “2017 ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company could 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 received a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the 2017 ATM Agreement. Since March 2017 and through March 31, 2021, the Company sold, pursuant to the terms of the 2017 ATM Agreement, an aggregate of 189,763 shares of Common Stock 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. In April 2021, the Company terminated the 2017 ATM Agreement with Cowen. Reverse Stock Split On November 12, 2020, the Company effected a reverse stock split of its shares of Common Stock at a ratio of 1-for-15, and trading of the Common Stock began on a split-adjusted basis on November 13, 2020. As a result of the reverse stock split, every 15 shares of the Company’s pre-reverse split Common Stock were combined and reclassified into one share of Common Stock. No fractional shares were issued in connection with the reverse stock split. In the result of any stockholders owning a fractional share, such stockholders received a cash payment in lieu of any fractional shares. The reverse stock split did not modify any rights of the Company’s Common Stock. The reverse stock split reduced the number of shares of Common Stock issuable upon the conversion of the Company’s outstanding shares of Series A Preferred Stock to a ratio of 66.67 and the exercise or vesting of its outstanding stock options and warrants in proportion to the ratio of the reverse stock split and caused a proportionate increase in the conversion and exercise prices of such preferred stock, stock options, and warrants. The accompanying condensed consolidated financial statements and notes to the condensed consolidated financial statements give retroactive effect to the exchange ratio for all periods presented. 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. As of June 30, 2021, the Company may sell an additional $10.2 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 13,333 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 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 1,000,000 shares of Common Stock and warrants to purchase 500,000 shares of Common Stock (the “2020 Public Offering”). Each whole warrant has an exercise price of $16.50 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 $15.00, 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 from the exercise of the warrants. Series A Preferred Conversion of Series A Preferred Stock As of June 30, 2021, the Company had 340,219 shares of preferred stock outstanding. 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. Refer to Note 1. Description of Business regarding the issuance of Series A Preferred Stock in October 2020. During the three and six months ended June 30, 2021, 14,604 and 58,268 shares of Series A Preferred Stock, respectively, had been converted into 973,648 and 3,884,719 shares of Common Stock, respectively. The following table presents information about the Company’s outstanding warrants: Number of Underlying Shares (1) Weighted-Average Exercise Price at June 30, 2021 Remaining Contractual Life at June 30, 2021 June 30, December 31, Liability-classified warrants Issued April 2017 781 781 $127.95 4.08 Equity-classified warrants Acquired October 2020 29,446 29,446 $0.15 9.49 Issued February 2020 (2) 409,712 466,667 $16.50 3.87 Issued November 2017 1,606 1,606 $107.25 3.63 Subtotal 440,764 497,719 $15.73 Total warrants 441,545 498,500 $15.94 ____________________ (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 six months ended June 30, 2021 is as follows: Common Stock Warrants Number Weighted-Average Exercise Price Outstanding at December 31, 2020 498,500 $16.00 Exercised (56,955) $16.50 Outstanding at June 30, 2021 441,545 $15.94 Equity-Classified Warrants In connection with the Merger in 2020, the Company assumed 29,446 outstanding warrants to purchase shares of Common Stock at an exercise price of $0.15 per share that expire ten years from the date of issuance. At the time of the Merger, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement. In connection with the Company’s 2020 Public Offering, the Company issued warrants to purchase 500,000 shares of its Common Stock at a price of $16.50 per share that expire five years from the date of issuance (the “Warrants”). 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 were classified as equity with no subsequent remeasurement as long as the warrants continued to be classified as equity. During the six months ended June 30, 2021, warrants were exercised to purchase 56,955 shares of Common Stock for proceeds of approximately $0.9 million.

WARRANTS

WARRANTS	6 Months Ended
	Jun. 30, 2021
Other Liabilities Disclosure [Abstract]
WARRANTS	CAPITAL STOCK Common Stock Under the Company’s amended and restated certificate of incorporation, the Company is authorized to issue 205,000,000 shares of its stock, of which 200,000,000 shares have been designated as Common Stock and 5,000,000 shares have been designated as Preferred Stock, both 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 Sales Agreements Jefferies LLC In April 2021, the Company entered into an Open Market Sale Agreement SM (the “2021 ATM Agreement”) with Jefferies LLC (“Jefferies”) under which the Company could 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 Jefferies as its sales agent in an “at the market” offering. Jefferies will receive a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Jefferies under the 2021 ATM Agreement. Through June 30, 2021, the Company sold an aggregate of 403,868 shares of Common Stock pursuant to the terms of the 2021 ATM Agreement, at a weighted-average price of $18.00 per share, for aggregate net proceeds of approximately $7.1 million, including commissions to Jefferies as sales agent. Cowen and Company, LLC In March 2017, the Company entered into a Common Stock Sales Agreement (the “2017 ATM Agreement”) with Cowen and Company, LLC (“Cowen”) under which the Company could 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 received a commission equal to 3.0% of the gross sales proceeds of any Common Stock sold through Cowen under the 2017 ATM Agreement. Since March 2017 and through March 31, 2021, the Company sold, pursuant to the terms of the 2017 ATM Agreement, an aggregate of 189,763 shares of Common Stock 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. In April 2021, the Company terminated the 2017 ATM Agreement with Cowen. Reverse Stock Split On November 12, 2020, the Company effected a reverse stock split of its shares of Common Stock at a ratio of 1-for-15, and trading of the Common Stock began on a split-adjusted basis on November 13, 2020. As a result of the reverse stock split, every 15 shares of the Company’s pre-reverse split Common Stock were combined and reclassified into one share of Common Stock. No fractional shares were issued in connection with the reverse stock split. In the result of any stockholders owning a fractional share, such stockholders received a cash payment in lieu of any fractional shares. The reverse stock split did not modify any rights of the Company’s Common Stock. The reverse stock split reduced the number of shares of Common Stock issuable upon the conversion of the Company’s outstanding shares of Series A Preferred Stock to a ratio of 66.67 and the exercise or vesting of its outstanding stock options and warrants in proportion to the ratio of the reverse stock split and caused a proportionate increase in the conversion and exercise prices of such preferred stock, stock options, and warrants. The accompanying condensed consolidated financial statements and notes to the condensed consolidated financial statements give retroactive effect to the exchange ratio for all periods presented. 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. As of June 30, 2021, the Company may sell an additional $10.2 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 13,333 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 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 1,000,000 shares of Common Stock and warrants to purchase 500,000 shares of Common Stock (the “2020 Public Offering”). Each whole warrant has an exercise price of $16.50 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 $15.00, 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 from the exercise of the warrants. Series A Preferred Conversion of Series A Preferred Stock As of June 30, 2021, the Company had 340,219 shares of preferred stock outstanding. 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. Refer to Note 1. Description of Business regarding the issuance of Series A Preferred Stock in October 2020. During the three and six months ended June 30, 2021, 14,604 and 58,268 shares of Series A Preferred Stock, respectively, had been converted into 973,648 and 3,884,719 shares of Common Stock, respectively. The following table presents information about the Company’s outstanding warrants: Number of Underlying Shares (1) Weighted-Average Exercise Price at June 30, 2021 Remaining Contractual Life at June 30, 2021 June 30, December 31, Liability-classified warrants Issued April 2017 781 781 $127.95 4.08 Equity-classified warrants Acquired October 2020 29,446 29,446 $0.15 9.49 Issued February 2020 (2) 409,712 466,667 $16.50 3.87 Issued November 2017 1,606 1,606 $107.25 3.63 Subtotal 440,764 497,719 $15.73 Total warrants 441,545 498,500 $15.94 ____________________ (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 six months ended June 30, 2021 is as follows: Common Stock Warrants Number Weighted-Average Exercise Price Outstanding at December 31, 2020 498,500 $16.00 Exercised (56,955) $16.50 Outstanding at June 30, 2021 441,545 $15.94 Equity-Classified Warrants In connection with the Merger in 2020, the Company assumed 29,446 outstanding warrants to purchase shares of Common Stock at an exercise price of $0.15 per share that expire ten years from the date of issuance. At the time of the Merger, the warrants were classified as equity and recorded at fair value with no subsequent remeasurement. In connection with the Company’s 2020 Public Offering, the Company issued warrants to purchase 500,000 shares of its Common Stock at a price of $16.50 per share that expire five years from the date of issuance (the “Warrants”). 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 were classified as equity with no subsequent remeasurement as long as the warrants continued to be classified as equity. During the six months ended June 30, 2021, warrants were exercised to purchase 56,955 shares of Common Stock for proceeds of approximately $0.9 million.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
SHARE-BASED COMPENSATION	SHARE-BASED COMPENSATION Equity Incentive Plans Upon closing of the Merger, the Company assumed all outstanding options issued under the 2020 Plan. The terms and conditions for each assumed option were substantially the same as prior to the Merger, including that the assumed options remained subject to the terms and conditions of the 2020 Plan, provided that each assumed option are exercisable for shares of the Company’s Common Stock and the number of shares issuable upon exercise of, and the exercise price per share for, each assumed option has been appropriately adjusted to give effect to the Merger. As of June 30, 2021, the Company had the following balances by plan: Stock Options Outstanding Shares Available for Issuance 2020 Plan 659,028 1,151,920 2016 Plan 2,010,039 1,139,287 2008 Plan 34,547 — Total 2,703,614 2,291,207 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 and employees of the Company’s affiliates. Pursuant to the 2016 Plan, the aggregate number of shares of Common Stock that may be issued will not exceed 3,419,368 shares. Subsequent to December 31, 2020, any awards granted under the 2016 Plan that expire or terminate subsequent to December 31, 2020, 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. Similarly, any shares of Common Stock issued pursuant to a stock award under the 2020 Plan that are forfeited, repurchased by the Company, or reacquired by the Company in satisfaction of tax withholding obligations will become available for grant under the 2020 Plan. Options granted under the Equity Incentive Plans 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, 2020 1,033,256 $15.34 8.56 $ 11,427 Granted 2,286,594 $22.13 — — Exercised (20,675) $14.83 — — Forfeited or expired (595,561) $24.41 — — Outstanding at June 30, 2021 2,703,614 $19.09 8.84 $ 12,500 Vested or expected to vest as of June 30, 2021 2,703,614 $19.09 8.84 $ 12,500 Exercisable as of June 30, 2021 336,561 $41.80 4.31 $ 164 Vested as of June 30, 2021 336,561 $41.80 4.31 $ 164 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 six months ended June 30, 2021 and 2020 was $19.33 and $9.11, respectively. The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Six Months Ended 2021 2020 Expected term, in years 5.91 4.82 Expected volatility 125.3% 99.3% Risk-free interest rate 0.6% 0.8% Expected dividend yield —% —% Weighted-average exercise price $22.13 $13.35 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. New six-month offering periods begin each August 22 and February 22. As of June 30, 2021, the Company had 85,657 shares available for issuance and 11,718 cumulative shares had been issued under the ESPP. Share-Based Compensation Expense Share-based compensation related to all equity awards issued pursuant to the Equity Incentive Plans and for 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 Six Months Ended 2021 2020 2021 2020 (in thousands) Research and development $ 1,002 $ 170 $ 2,113 $ 357 General and administrative 2,815 453 4,879 930 Total share-based compensation expense $ 3,817 $ 623 $ 6,992 $ 1,287 As of June 30, 2021, the Company had $36.8 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 3.45 years.

NET LOSS PER SHARE

NET LOSS PER SHARE	6 Months Ended
	Jun. 30, 2021
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: June 30, 2021 2020 Series A Preferred Stock 22,682,400 — Options to purchase Common Stock 2,703,614 343,933 Warrants to purchase Common Stock 441,545 502,387 Total 25,827,559 846,320

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On July 15, 2021, the Company announced the appointment of Jennifer Moses, CPA to the Company’s Board of Directors and as Chair of the Company’s Audit Committee. On July 16, 2021, the Company amended its corporate office lease and entered into a 3 year lease for additional space with an option to extend for one additional term of 3 years. The new space is 3,284 square feet and carries an annual base rent of approximately $134,000 plus proportionate share of operating expenses.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Viridian Therapeutics Europe Limited and Viridian Therapeutics S.à.r.l., each of which were formed for the sole purpose of submitting regulatory filings in Europe. The Company’s subsidiaries have no employees or operations. The condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position, results of operations, and cash flows for the periods presented. All significant intercompany balances have been eliminated in consolidation. The Company’s management performed an evaluation of its activities through the date of filing of these condensed consolidated 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
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, such as contract research organizations and contract manufacturing operations, on the Company’s behalf, costs to manufacture or have manufactured clinical trial materials, laboratory supplies, depreciation, non-clinical activities, regulatory operations, 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.
Share-Based Compensation	Share-Based Compensation The Company accounts for share-based compensation expense related to stock options granted to employees, members of its board of directors, and non-employees under its 2008 Equity Incentive Plan (the “2008 Plan”), its amended and restated 2016 Equity Incentive Plan (the “2016 Plan”), and the 2020 Equity Incentive Plan (the “2020 Plan”) (collectively, the “Equity Incentive Plans”) 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.
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.
Fair Value Measurements and Fair Value of Financial Instruments	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 utilizes 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. June 30, 2021 December 31, 2020 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 27,693 $ — $ 45,960 $ — U.S. treasury securities (included in short-term investments) 81,597 — 81,742 — Total assets $ 109,290 $ — $ 127,702 $ — 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 Company accounts for warrants to purchase its stock pursuant to ASC Topic 470, Debt , and ASC Topic 480, Distinguishing Liabilities from Equity
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
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 on January 1, 2020, the date of transition to Accounting Standards Update (“ASU”) No. 2016-02 , Leases (Topic 842),
Convertible Preferred Stock	Convertible Preferred Stock The Company records shares of non-voting convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The Company has applied the guidance in ASC 480-10-S99-3A, SEC Staff Announcement: Classification and Measurement of Redeemable Securities , and at issuance classified the Series A Preferred Stock outside of stockholders’ equity because, if convertibility of Series A Preferred Stock into Common Stock was not approved by the stockholders, the Series A Preferred Stock would be redeemable at the option of the holders for cash equal to the closing price of the Common Stock on last trading day prior to the holder’s redemption request. On December 31, 2020, the stockholders approved the convertibility of the Series A Preferred Stock into Common Stock and as such, the Company reclassified the Series A Preferred Stock to permanent equity.
Impairment of Long-Lived Assets	Impairment of Long-Lived AssetsThe 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
Comprehensive Loss	Comprehensive LossComprehensive 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 condensed consolidated statements of changes in 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.
Warrants	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 condensed consolidated balance sheets. Any changes in the warrant liability during each reporting period would be reflected as other expense in the condensed consolidated statement of operations and comprehensive loss.
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 - To Be Adopted	Recent Accounting Pronouncements – To Be Adopted From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company does not believe that the adoption of recently issued standards have or may have a material impact on the Company’s consolidated financial statements or disclosures.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2021
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 utilizes 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. June 30, 2021 December 31, 2020 Level 1 Level 3 Level 1 Level 3 (in thousands) Assets: Money market funds (included in cash and cash equivalents) $ 27,693 $ — $ 45,960 $ — U.S. treasury securities (included in short-term investments) 81,597 — 81,742 — Total assets $ 109,290 $ — $ 127,702 $ — Liabilities: Common Stock warrants (included in accrued and other liabilities) $ — $ 100 $ — $ 100

ACQUISITION OF PRIVATE VIRIDI_2

ACQUISITION OF PRIVATE VIRIDIAN (Tables)	6 Months Ended
	Jun. 30, 2021
Business Combination and Asset Acquisition [Abstract]
Schedule of Asset Acquisition	The following table summarizes the net assets acquired based on their estimated fair values as of October 27, 2020 (in thousands): Acquired IPR&D $ 69,861 Cash and cash equivalents 29,371 Accrued liabilities (1,843) Net acquired tangible assets $ 97,389

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	6 Months Ended
	Jun. 30, 2021
Property, Plant and Equipment [Abstract]
Schedule of Components of Property and Equipment	Property and equipment, net, consisted of the following: June 30, December 31, (in thousands) Lab equipment $ 753 $ 2,509 Leasehold improvements 741 741 Computer hardware and software 389 336 Furniture and fixtures 165 166 Property and equipment, gross 2,048 3,752 Less: accumulated depreciation and amortization (1,750) (3,443) Property and equipment, net $ 298 $ 309

ACCRUED LIABILITIES (Tables)

ACCRUED LIABILITIES (Tables)	6 Months Ended
	Jun. 30, 2021
Payables and Accruals [Abstract]
Schedule of Components of Accrued Liabilities	Accrued liabilities consisted of the following: June 30, December 31, (in thousands) Accrued outsourced clinical trials and preclinical studies $ 10,314 $ 5,400 Accrued employee compensation and related taxes 2,566 1,963 Operating lease liability 412 455 Accrued legal fees and expenses 88 380 Accrued other professional service fees 278 796 Value of liability-classified stock purchase warrants 100 100 License agreement liability 177 86 Other accrued liabilities 215 523 Total accrued liabilities $ 14,150 $ 9,703

WARRANTS (Tables)

WARRANTS (Tables)	6 Months Ended
	Jun. 30, 2021
Other Liabilities Disclosure [Abstract]
Schedule of Summary of Warrants	The following table presents information about the Company’s outstanding warrants: Number of Underlying Shares (1) Weighted-Average Exercise Price at June 30, 2021 Remaining Contractual Life at June 30, 2021 June 30, December 31, Liability-classified warrants Issued April 2017 781 781 $127.95 4.08 Equity-classified warrants Acquired October 2020 29,446 29,446 $0.15 9.49 Issued February 2020 (2) 409,712 466,667 $16.50 3.87 Issued November 2017 1,606 1,606 $107.25 3.63 Subtotal 440,764 497,719 $15.73 Total warrants 441,545 498,500 $15.94 ____________________ (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 six months ended June 30, 2021 is as follows: Common Stock Warrants Number Weighted-Average Exercise Price Outstanding at December 31, 2020 498,500 $16.00 Exercised (56,955) $16.50 Outstanding at June 30, 2021 441,545 $15.94

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Summary of Balances by Plan	As of June 30, 2021, the Company had the following balances by plan: Stock Options Outstanding Shares Available for Issuance 2020 Plan 659,028 1,151,920 2016 Plan 2,010,039 1,139,287 2008 Plan 34,547 — Total 2,703,614 2,291,207
Schedule of 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, 2020 1,033,256 $15.34 8.56 $ 11,427 Granted 2,286,594 $22.13 — — Exercised (20,675) $14.83 — — Forfeited or expired (595,561) $24.41 — — Outstanding at June 30, 2021 2,703,614 $19.09 8.84 $ 12,500 Vested or expected to vest as of June 30, 2021 2,703,614 $19.09 8.84 $ 12,500 Exercisable as of June 30, 2021 336,561 $41.80 4.31 $ 164 Vested as of June 30, 2021 336,561 $41.80 4.31 $ 164
Schedule of Fair Value Assumptions for Stock Options	The fair value was determined by the Black-Scholes option pricing model using the following weighted-average assumptions: Six Months Ended 2021 2020 Expected term, in years 5.91 4.82 Expected volatility 125.3% 99.3% Risk-free interest rate 0.6% 0.8% Expected dividend yield —% —% Weighted-average exercise price $22.13 $13.35
Schedule of Allocation of Share-based Compensation Expense	Share-based compensation related to all equity awards issued pursuant to the Equity Incentive Plans and for 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 Six Months Ended 2021 2020 2021 2020 (in thousands) Research and development $ 1,002 $ 170 $ 2,113 $ 357 General and administrative 2,815 453 4,879 930 Total share-based compensation expense $ 3,817 $ 623 $ 6,992 $ 1,287

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities	Potentially dilutive securities include the following: June 30, 2021 2020 Series A Preferred Stock 22,682,400 — Options to purchase Common Stock 2,703,614 343,933 Warrants to purchase Common Stock 441,545 502,387 Total 25,827,559 846,320

DESCRIPTION OF BUSINESS (Detail

DESCRIPTION OF BUSINESS (Details) - USD ($) $ in Thousands	Oct. 27, 2020	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Dec. 20, 2020	Nov. 12, 2020
Business Acquisition [Line Items]
Accumulated deficit		$ 315,311	$ 315,311	$ 278,887
Cash, cash equivalents and short-term investments		$ 109,300	$ 109,300
Common Stock
Business Acquisition [Line Items]
Conversion of stock, shares converted (in shares)		973,648	3,884,719
Viridian Merger
Business Acquisition [Line Items]
Gross proceeds of private placement	$ 91,000
Viridian Merger | Series A Preferred Stock
Business Acquisition [Line Items]
Stock issued (in shares)	203,197
Convertible stock percentage	30.00%
Viridian Merger | Series A Preferred Stock | Private Placement
Business Acquisition [Line Items]
Shares sold (in shares)	195,290
Viridian Merger | Common Stock
Business Acquisition [Line Items]
Stock issued (in shares)	72,131
Number of securities called by each warrant or right (in shares)	66.67					66.67
Viridian Merger | Common Stock | Minimum
Business Acquisition [Line Items]
Beneficial ownership					4.99%
Viridian Merger | Common Stock | Series A Preferred Stock | Maximum
Business Acquisition [Line Items]
Beneficial ownership					19.99%

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Level 1
Assets:
Money market funds (included in cash and cash equivalents)	$ 27,693	$ 45,960
U.S. treasury securities (included in short-term investments)	81,597	81,742
Total assets	109,290	127,702
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		6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)segment	Jun. 30, 2020USD ($)
Property, Plant and Equipment [Line Items]
Impairment charges	$ 0	$ 0	$ 0	$ 0
Unrealized gain (loss) on investments	9,000	0	(4,000)	0
Realized investment gains (losses)		0		0
Unrecognized tax benefits			0
Income tax penalties and interest expense	$ 0	$ 0	$ 0	$ 0
Number of operating segments | segment			1
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives			3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives			5 years

ACQUISITION OF PRIVATE VIRIDI_3

ACQUISITION OF PRIVATE VIRIDIAN - Narrative (Details) - Viridian Merger - USD ($) $ in Millions	Oct. 27, 2020	Nov. 12, 2020
Business Acquisition [Line Items]
Payments for asset acquisition	$ 97.4
Direct costs of the asset acquisition	$ 2
Series A Preferred Stock
Business Acquisition [Line Items]
Stock issued (in shares)	203,197
Common Stock
Business Acquisition [Line Items]
Stock issued (in shares)	72,131
Number of securities called by each warrant or right (in shares)	66.67	66.67

ACQUISITION OF PRIVATE VIRIDI_4

ACQUISITION OF PRIVATE VIRIDIAN - Summary of Assets Acquired and Liabilities Assumed (Details) - Viridian Merger $ in Thousands	Oct. 27, 2020USD ($)
Business Acquisition [Line Items]
Acquired IPR&D	$ 69,861
Cash and cash equivalents	29,371
Accrued liabilities	(1,843)
Net acquired tangible assets	$ 97,389

COLLABORATION AGREEMENTS (Detai

COLLABORATION AGREEMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	$ 1,090	$ 168	$ 2,541	$ 996
Current portion of deferred revenue - related party	288		288		$ 301
Collaboration revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	0	0	0	681
Zenas BioPharma
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Current portion of deferred revenue - related party	1,600		1,600		$ 800
Zenas BioPharma | Collaboration revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	$ 1,100		$ 2,500
Servier | Collaboration revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue		$ 0		$ 700

PROPERTY AND EQUIPMENT - Compon

PROPERTY AND EQUIPMENT - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,048	$ 3,752
Less: accumulated depreciation and amortization	(1,750)	(3,443)
Property and equipment, net	298	309
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	753	2,509
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	741	741
Computer hardware and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	389	336
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 165	$ 166

PROPERTY AND EQUIPMENT - Narrat

PROPERTY AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Assets held-for-sale					$ 142
Proceeds from sale of machinery and equipment	$ 75
Loss from disposition of equipment	(67)
Depreciation and amortization	$ 25	$ 64	$ 58	$ 132

ACCRUED LIABILITIES - Component

ACCRUED LIABILITIES - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Oct. 31, 2020	Jan. 01, 2020
Payables and Accruals [Abstract]
Accrued outsourced clinical trials and preclinical studies	$ 10,314	$ 5,400
Accrued employee compensation and related taxes	2,566	1,963
Operating lease liability	412	455	$ 700	$ 1,600
Accrued legal fees and expenses	88	380
Accrued other professional service fees	278	796
Value of liability-classified stock purchase warrants	100	100
License agreement liability	177	86
Other accrued liabilities	215	523
Total accrued liabilities	$ 14,150	$ 9,703
Operating lease, liability, current, statement of financial position [Extensible List]	Total accrued liabilities	Total accrued liabilities

NOTES PAYABLE - Narrative (Deta

NOTES PAYABLE - Narrative (Details) - USD ($)	1 Months Ended
	Apr. 30, 2020	Nov. 30, 2017	Jun. 30, 2021	Dec. 31, 2020	Dec. 18, 2020
2017 SVB Loan Agreement
Debt Instrument [Line Items]
Notes payable to bank			$ 0	$ 0
2017 SVB Loan Agreement | Note Payable to Banks
Debt Instrument [Line Items]
Proceeds from debt		$ 10,000,000
Repayment period		30 months
Interest-only period		18 months
Extended maturity period	6 months
Final payment fee					$ 900,000
Paycheck Protection Program Loan
Debt Instrument [Line Items]
Unsecured debt			$ 0	$ 0
Paycheck Protection Program Loan | Unsecured debt
Debt Instrument [Line Items]
Loan received	$ 1,700,000
Interest rate	1.00%

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details)	Nov. 04, 2020contingent_value_right	Dec. 31, 2020USD ($)shares	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)renewal_term	Jun. 30, 2020USD ($)	Apr. 30, 2021USD ($)	Dec. 16, 2020USD ($)	Oct. 31, 2020USD ($)	Oct. 27, 2020USD ($)	Jan. 01, 2020USD ($)
Commitments and Contingencies [Line Items]
Number of renewal terms (up to) | renewal_term					2
Lessee, operating lease, renewal term			3 years		3 years
Operating lease right-of-use asset, net		$ 478,000	$ 1,567,000		$ 1,567,000				$ 700,000		$ 1,600,000
Operating lease liability		$ 455,000	412,000		412,000				$ 700,000		$ 1,600,000
Lease discount rate									6.00%		6.00%
Lease remaining term											12 months
Sublease term							9 months
Operating sublease receivables							$ 100,000
Future lease payments due			$ 1,800,000		$ 1,800,000
Operating lease, liability, current, statement of financial position [Extensible List]		Accrued liabilities	Accrued liabilities		Accrued liabilities
Operating lease liability noncurrent			$ 1,200,000		$ 1,200,000
Operating lease, liability, noncurrent, statement of financial position [Extensible List]			Other liabilities		Other liabilities
Amortization of the operating lease right-of-use asset			$ 100,000	$ 100,000	$ 200,000	$ 200,000
Operating expenses of leases			$ 34,000	$ 100,000	$ 68,000	$ 200,000
Fairmount Funds Management
Commitments and Contingencies [Line Items]
Noncontrolling interest ownership percentage							5.00%
Viridian Merger
Commitments and Contingencies [Line Items]
Contractual contingent value right | contingent_value_right	1
Cash receivable percentage	80.00%
Period after closing of acquisition in which CVR holders are entitled to proceeds from disposition of legacy cell therapy assets	5 years
ImmunoGen, Inc
Commitments and Contingencies [Line Items]
Milestone payments										$ 48,000,000
Potential royalty payments										$ 95,000,000
Xencor, Inc
Commitments and Contingencies [Line Items]
Milestone payments								$ 30,000,000
Potential royalty payments								$ 25,000,000
Shares issued in exchange for rights granted (in shares) | shares		322,407
Value of shares issued in exchange for rights granted		$ 6,000,000

CAPITAL STOCK (Details)

CAPITAL STOCK (Details)	Nov. 12, 2020shares	Apr. 30, 2021USD ($)$ / sharesshares	Feb. 29, 2020USD ($)$ / sharesshares	Dec. 31, 2019closingshares	Mar. 31, 2017USD ($)	Jun. 30, 2021$ / sharesshares	Jun. 30, 2021$ / sharesshares	Mar. 31, 2021USD ($)shares	Jan. 04, 2021vote$ / sharesshares	Dec. 31, 2020$ / sharesshares	Oct. 27, 2020shares
Class of Stock [Line Items]
Shares authorized (in shares)									205,000,000
Common stock, shares authorized (in shares)						200,000,000	200,000,000		200,000,000	200,000,000
Preferred stock, shares authorized (in shares)						5,000,000	5,000,000		5,000,000	5,000,000
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01		$ 0.01	$ 0.01
Common stock, par value (in dollars per share) | $ / shares						0.01	0.01		$ 0.01	0.01
Common stock, vote per share | vote									1
Warrant exercise price (in dollars per share) | $ / shares						$ 15.94	$ 15.94			$ 16
Preferred stock outstanding (in shares)						0	0			0
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)						435,000	435,000			435,000
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01			$ 0.01
Preferred stock outstanding (in shares)						340,219	340,219			398,487
Common Stock
Class of Stock [Line Items]
Conversion of stock, shares converted (in shares)						973,648	3,884,719
Preferred Stock | Series A Preferred Stock
Class of Stock [Line Items]
Conversion of stock, shares converted (in shares)						14,604	58,268
Viridian Merger | Common Stock
Class of Stock [Line Items]
Stock split ratio, common stock	0.0666
Number of securities called by each warrant or right (in shares)	66.67										66.67
ATM Agreement
Class of Stock [Line Items]
Commission fee percent		3.00%			3.00%
ATM Agreement | Common Stock
Class of Stock [Line Items]
Shares sold (in shares)		403,868						189,763
Weighted-average share price (in dollars per share) | $ / shares		$ 18
Issuance of common stock under license agreement | $		$ 7,100,000						$ 11,600,000
ATM Agreement | Maximum
Class of Stock [Line Items]
Aggregate offering | $		$ 50,000,000			$ 50,000,000
Aspire Stock Purchase Agreement
Class of Stock [Line Items]
Amount of shares authorized to be sold (in shares)				20,000,000			10,200,000
Sale of stock, term				30 months
Average over number of lowest sale prices | closing				3
Number of consecutive days threshold				10 days
Aspire Stock Purchase Agreement | Common Stock
Class of Stock [Line Items]
Amount of shares required to be purchased (in shares)				13,333
Additional trading volume available for purchase, percent				30.00%
Price of additional share, percent of next business days' volume weighted average price				97.00%
Oppenheimer
Class of Stock [Line Items]
Issuance of common stock under license agreement | $			$ 13,900,000
Number of securities called by each warrant or right (in shares)			1
Amount of shares authorized to be sold (in shares)			1,000,000
Convertible preferred stock (in shares)			500,000
Warrant exercise price (in dollars per share) | $ / shares			$ 16.50
Number of shares sold per each combination (in shares)			1
Combined price of instruments issued per share (in dollars per share) | $ / shares			$ 15

WARRANTS - Stock Warrants Outst

WARRANTS - Stock Warrants Outstanding (Details) - $ / shares	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	441,545	498,500
Weighted average exercise price (in dollars per share)	$ 15.94	$ 16
Issued April 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	781	781
Weighted average exercise price (in dollars per share)	$ 127.95
Remaining contractual life	4 years 29 days
Acquired October 2020
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	29,446	29,446
Weighted average exercise price (in dollars per share)	$ 0.15	$ 0.15
Remaining contractual life	9 years 5 months 26 days
Issued February 2020
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	409,712	466,667
Weighted average exercise price (in dollars per share)	$ 16.50	$ 16.50
Remaining contractual life	3 years 10 months 13 days
Issued November 2017
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	1,606	1,606
Weighted average exercise price (in dollars per share)	$ 107.25		$ 107.25
Remaining contractual life	3 years 7 months 17 days
Equity-classified warrants
Class of Warrant or Right [Line Items]
Number of Underlying Shares (in shares)	440,764	497,719
Weighted average exercise price (in dollars per share)	$ 15.73

WARRANTS - Stock Warrant Activi

WARRANTS - Stock Warrant Activity (Details)	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Number
Beginning balance (in shares) | shares	498,500
Exercised (in shares) | shares	(56,955)
Ending balance (in shares) | shares	441,545
Weighted-Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 16
Exercised (in dollars per share) | $ / shares	16.50
Ending balance (in dollars per share) | $ / shares	$ 15.94

WARRANTS - Narrative (Details)

WARRANTS - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Warrant exercise price (in dollars per share)	$ 15.94	$ 16
Acquired October 2020
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)		29,446
Warrant exercise price (in dollars per share)	$ 0.15	$ 0.15
Expected life		10 years
Issued February 2020
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	56,955	500,000
Warrant exercise price (in dollars per share)	$ 16.50	$ 16.50
Expected life		5 years
Proceeds from warrant exercises	$ 0.9
Issued November 2017
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			1,606
Warrant exercise price (in dollars per share)	$ 107.25		$ 107.25
Expected life			7 years

SHARE-BASED COMPENSATION - Bala

SHARE-BASED COMPENSATION - Balance by Plans (Details)	Jun. 30, 2021shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding (in shares)	2,703,614
Shares Available for Issuance (in shares)	2,291,207
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding (in shares)	659,028
Shares Available for Issuance (in shares)	1,151,920
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding (in shares)	2,010,039
Shares Available for Issuance (in shares)	1,139,287
2008 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Options Outstanding (in shares)	34,547
Shares Available for Issuance (in shares)	0

SHARE-BASED COMPENSATION - Narr

SHARE-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended		55 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized employee stock-based compensation costs			$ 36.8		$ 36.8
Remaining weighted-average period for RSUs			3 years 5 months 12 days
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)			85,657		85,657
Issuance of common stock for cash under employee stock purchase plan (in shares)	980	1,545			11,718
Options to Purchase Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period			10 years
Vesting period (up to)			48 months
Weighted average fair value per option (in usd per share)			$ 19.33	$ 9.11
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
2016 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance (in shares)			3,419,368		3,419,368

SHARE-BASED COMPENSATION - Stoc

SHARE-BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Number of Options
Ending balance (in shares)	2,703,614
Options to purchase Common Stock
Number of Options
Beginning balance (in shares)	1,033,256
Granted (in shares)	2,286,594
Exercised (in shares)	(20,675)
Forfeited or expired (in shares)	(595,561)
Ending balance (in shares)	2,703,614	1,033,256
Vested or expected to vest (in shares)	2,703,614
Exercisable (in shares)	336,561
Vested (in shares)	336,561
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 15.34
Granted (in dollars per share)	22.13
Exercised (in dollars per share)	14.83
Forfeited or expired (in dollars per share)	24.41
Ending balance (in dollars per share)	19.09	$ 15.34
Vested or expected to vest (in dollars per share)	19.09
Exercisable (in dollars per share)	41.80
Vested (in dollars per share)	$ 41.80
Weighted average remaining contractual term and Aggregate intrinsic value
Outstanding (Weighted Average Remaining Contractual Term)	8 years 10 months 2 days	8 years 6 months 21 days
Vested or expected to vest (Weighted Average Remaining Contractual Term)	8 years 10 months 2 days	8 years 6 months 21 days
Exercisable (Weighted Average Remaining Contractual Term)	4 years 3 months 21 days
Vested (Weighted Average Remaining Contractual Term)	4 years 3 months 21 days
Outstanding (Aggregate Intrinsic Value)	$ 12,500	$ 11,427
Vested or expected to vest (Aggregate Intrinsic Value)	12,500	$ 11,427
Exercisable (Aggregate Intrinsic Value)	164
Vested (Aggregate Intrinsic Value)	$ 164

SHARE-BASED COMPENSATION - Fair

SHARE-BASED COMPENSATION - Fair Value Assumption for Stock Options (Details) - Options to purchase Common Stock - $ / shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term, in years	5 years 10 months 28 days	4 years 9 months 25 days
Expected volatility	125.30%	99.30%
Risk-free interest rate	0.60%	0.80%
Expected dividend yield	0.00%	0.00%
Weighted-average exercise price (in dollars per share)	$ 22.13	$ 13.35

SHARE-BASED COMPENSATION - Allo

SHARE-BASED COMPENSATION - Allocation of Share-based Compensation Expense on Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 3,817	$ 623	$ 6,992	$ 1,287
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	1,002	170	2,113	357
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total share-based compensation expense	$ 2,815	$ 453	$ 4,879	$ 930

NET LOSS PER SHARE - Summary of

NET LOSS PER SHARE - Summary of Potential Dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	25,827,559	846,320
Series A Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	22,682,400	0
Options to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	2,703,614	343,933
Warrants to purchase Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities (in shares)	441,545	502,387

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) $ in Thousands	Jul. 16, 2021USD ($)ft²	Jun. 30, 2021
Subsequent Event [Line Items]
Lessee, operating lease, renewal term		3 years
Subsequent Event
Subsequent Event [Line Items]
Lessee, operating lease, term of contract	3 years
Lessee, operating lease, renewal term	3 years
Area of real estate property | ft²	3,284
Annual base rent | $	$ 134