SELLAS Life Sciences (SLS) 10-Q 13 May 21 2021 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2021	May 13, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-33958
Entity Registrant Name	SELLAS Life Sciences Group, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8099512
Entity Address, Address Line One	7 Times Square, Suite 2503,
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10036
City Area Code	(646)
Local Phone Number	200-5278
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	SLS
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		15,084,754
Entity Central Index Key	0001390478
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 28,033	$ 35,302
Restricted cash and cash equivalents	100	100
Contract asset	282	1,128
Prepaid expenses and other current assets	3,016	395
Total current assets	31,431	36,925
Operating lease right-of-use asset	854	896
In-process research and development	5,700	5,700
Goodwill	1,914	1,914
Deposits and other assets	676	614
Total assets	40,575	46,049
Current liabilities:
Accounts payable	2,350	4,657
Accrued expenses and other current liabilities	2,547	1,913
Operating lease liability	174	166
Deferred revenue	900	5,600
Total current liabilities	5,971	12,336
Operating lease liability, non-current	775	825
Deferred tax liability	239	239
Warrant liability	86	55
Contingent consideration	4,762	4,633
Total liabilities	11,833	18,088
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; Series A convertible preferred stock, 17,500 shares designated; no shares issued and outstanding at March 31, 2021 and December 31, 2020	0	0
Common stock, $0.0001 par value; 350,000,000 shares authorized, 15,084,754 and 14,254,554 shares issued and outstanding at March 31, 2021and December 31, 2020, respectively.	2	1
Additional paid-in capital	149,047	145,864
Accumulated deficit	(120,307)	(117,904)
Total stockholders’ equity	28,742	27,961
Total liabilities and stockholders’ equity	$ 40,575	$ 46,049

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	350,000,000	350,000,000
Common stock, shares issued (in shares)	15,084,754	14,254,554
Common stock, shares outstanding (in shares)	15,084,754	14,254,554
Series A Preferred Stock
Preferred stock, shares authorized (in shares)	17,500	17,500

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Licensing revenue	$ 5,700,000	$ 0
Operating expenses:
Cost of licensing revenue	100,000	0
Research and development	4,284,000	1,864,000
General and administrative	3,561,000	2,200,000
Total operating expenses	7,945,000	4,064,000
Operating loss	(2,245,000)	(4,064,000)
Non-operating income (expense), net:
Change in fair value of warrant liability	(31,000)	35,000
Change in fair value of contingent consideration	(129,000)	(138,000)
Interest income, net	2,000	24,000
Total non-operating expense, net	(158,000)	(79,000)
Net loss	(2,403,000)	(4,143,000)
Deemed dividend arising from warrant modifications	0	(78,000)
Net loss attributable to common stockholders	$ (2,403,000)	$ (4,221,000)
Per share information:
Net loss per common share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.16)	$ (0.66)
Weighted-average common shares outstanding, basic and diluted (in shares)	14,877,317	6,374,979

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		5,080,100
Beginning balance at Dec. 31, 2019	$ 6,093	$ 1	$ 107,239	$ (101,147)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		1,189,000
Issuance of common stock and common stock warrants, net of issuance costs	5,963		5,963
Issuance of common stock upon exercise of pre-funded warrants (in shares)		448,800
Issuance of common stock upon exercise of pre-funded warrants	4		4
Stock-based compensation	145		145
Net loss	(4,143)			(4,143)
Ending balance (in shares) at Mar. 31, 2020		6,717,900
Ending balance at Mar. 31, 2020	8,062	$ 1	113,351	(105,290)
Beginning balance (in shares) at Dec. 31, 2020		14,254,554
Beginning balance at Dec. 31, 2020	27,961	$ 1	145,864	(117,904)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of warrants (in shares)		830,200
Issuance of common stock upon exercise of warrants	3,000	$ 1	2,999
Stock-based compensation	184		184
Net loss	(2,403)			(2,403)
Ending balance (in shares) at Mar. 31, 2021		15,084,754
Ending balance at Mar. 31, 2021	$ 28,742	$ 2	$ 149,047	$ (120,307)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (2,403,000)	$ (4,143,000)
Adjustment to reconcile net loss to net cash used in operating activities:
Non-cash stock-based compensation	184,000	145,000
Amortization of contract asset	846,000	0
Change in operating lease right of use assets	0	0
Change in fair value of common stock warrants	31,000	(35,000)
Change in fair value of contingent consideration	129,000	138,000
Changes in operating assets and liabilities:
Contract asset	(1,410,000)	0
Prepaid expenses and other assets	(2,683,000)	(1,350,000)
Accounts payable	(897,000)	(1,303,000)
Accrued expenses and other current liabilities	634,000	(283,000)
Deferred revenue	(4,700,000)	0
Net cash used in operating activities	(10,269,000)	(6,831,000)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of offering costs		5,988,000
Collection of stock subscription receivable	0	308,000
Net proceeds from exercise of warrants	3,000,000	4,000
Net cash provided by financing activities	3,000,000	6,300,000
Net decrease in cash, cash equivalents, restricted cash, and restricted cash equivalents	(7,269,000)	(531,000)
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the beginning of period	35,402,000	7,377,000
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the end of period	28,133,000	6,846,000
Supplemental disclosure of non-cash investing and financing activities:
Offering expenses in accounts payable and accrued expenses and other current liabilities	$ 0	$ 25,000

Description of Business

Description of Business	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Overview SELLAS Life Sciences Group, Inc. (the "Company" or "SELLAS") is a late-stage clinical biopharmaceutical company focused on novel cancer immunotherapeutics for a broad range of cancer indications. SELLAS’ lead product candidate, galinpepimut-S ("GPS"), is a cancer immunotherapeutic agent licensed from Memorial Sloan Kettering Cancer Center ("MSK") and targets the Wilms Tumor 1 ("WT1") protein, which is present in 20 or more cancer types. Based on its mechanism of action as a directly immunizing agent, GPS has potential as a monotherapy or in combination with other immunotherapeutic agents to address a broad spectrum of hematologic, or blood, cancers and solid tumor indications. SELLAS’ second product candidate, nelipepimut-S ("NPS"), is a cancer immunotherapy targeting the human epidermal growth factor receptor 2 ("HER2") expressing cancers with potential for the treatment of patients with early stage breast cancer with low to intermediate HER2 expression, otherwise known as HER2 1+ or 2+, which includes triple negative breast cancer ("TNBC") patients, following standard of care. As used in this Quarterly Report on Form 10-Q, the words the "Company," and "SELLAS" refer to SELLAS Life Sciences Group, Inc. and its consolidated subsidiaries following the completion of the business combination with Galena Biopharma, Inc., a Delaware corporation ("Galena"), and SELLAS Life Sciences Group, Ltd., a privately held Bermuda exempted company ("Private SELLAS"), in December 2017. This business combination is referred to as the Merger. Upon completion of the Merger, the Company's name changed from "Galena Biopharma, Inc." to "SELLAS Life Sciences Group, Inc." and the Company's financial statements became those of Private SELLAS.

Liquidity

Liquidity	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Liquidity	Liquidity Since inception, the Company has incurred recurring losses and negative cash flows from operations and, as of March 31, 2021, has an accumulated deficit of $120.3 million. During the quarter ended March 31, 2021, the Company incurred a net loss of $2.4 million and used $10.3 million of cash in operations which included one-time payments of $1.4 million for contract acquisition costs related to the out-licensing of intellectual property rights and transfer of technical know-how, a $2.7 million increase in prepaid expenses and other assets primarily for insurance and prepaid clinical trial costs and a $0.3 million decrease in accounts payable and accrued expenses and other current liabilities. The Company expects to continue to generate operating losses and negative cash flows for the next few years and will need additional funding to support its planned operating activities through profitability. The transition to profitability is dependent upon the successful development, approval, and commercialization of the Company's product candidates and the achievement of a level of revenues adequate to support its cost structure. On April 16, 2021, the Company entered into a Controlled Equity Offering SM Sales Agreement (the "Sales Agreement") with Cantor Fitzgerald & Co. (the "Agent"). From time to time during the term of the Sales Agreement, the Company may offer and sell shares of common stock having an aggregate offering price up to a total of $50.0 million in gross proceeds. The Agent will collect a fee equal to 3% of the gross sales price of all shares of common stock sold. Shares of common stock sold under the Sales Agreement will be offered and sold pursuant to the Company's registration statement on Form S-3, which was filed with the SEC on April 16, 2021 and was declared effective on April 29, 2021. Other than the Sales Agreement, the Company currently does not have any commitments to obtain additional funds. As of March 31, 2021, the Company had cash and cash equivalents of approximately $28.0 million, and restricted cash and cash equivalents of $0.1 million. In accordance with Accounting Standards Codification ("ASC") 205-40, Presentation of Financial Statements - Going Concern , the Company evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the consolidated financial statements are issued. The Company expects its cash and cash equivalents, together with access to the Sales Agreement to sell common stock, will be sufficient to fund current planned operations for at least the next twelve months from the date of issuance of these financial statements, though it may pursue additional capital resources through public or private equity or debt financings or by entering into additional license agreements or collaborations with other companies. Management's expectations with respect to its ability to fund current planned operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management's estimates, the Company may need to seek additional strategic or financing opportunities sooner than would otherwise be expected. There is no guarantee that any of these strategic or financing opportunities will be executed or executed on favorable terms, and some could be dilutive to existing stockholders. If the Company is unable to obtain additional funding on a timely basis, it may be forced to significantly curtail, delay, or discontinue one or more of its planned research and development programs or be unable to expand its operations or otherwise prepare for the potential regulatory approval and commercialization of its product candidates, assuming positive data.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies The Company's complete summary of significant accounting policies can be found in "Item 8. Financial Statements and Supplementary Data - Note 3. Basis of Presentation and Significant Accounting Policies" in the audited annual consolidated financial statements included in the 2020 Annual Report. The significant accounting policies summarized and included in the 2020 Annual Report have not materially changed, except as set forth below. Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification ("ASC") and Accounting Standards Updates ("ASU") of the Financial Accounting Standards Board ("FASB"). Principles of Consolidation The consolidated financial statements include the financial statements of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated upon consolidation. Unless the context otherwise indicates, reference in these notes to the "Company" refer to SELLAS Life Sciences Group, Inc., and its wholly owned subsidiaries, Private SELLAS, SLSG Limited, LLC, Sellas Life Sciences Limited, and Apthera, Inc. The functional currency of the Company's non-U.S. operations is the U.S. dollar. Unaudited Interim Results These consolidated financial statements and accompanying notes should be read in conjunction with the Company's annual consolidated financial statements and the notes thereto included in the 2020 Annual Report. The accompanying consolidated financial statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020, are unaudited, but include all adjustments, consisting of normal recurring entries, that management believes to be necessary for a fair presentation of the periods presented. Interim results are not necessarily indicative of results for a full year. Balance sheet amounts as of December 31, 2020 have been derived from the audited financial statements as of that date. Time-Vested Restricted Stock Units During the three months ended March 31, 2021, the Board of Directors granted restricted stock units ("RSUs") to employees that vest based on continuous service. Time-vested RSUs awarded to employees vest one-fourth per year annually over four years, provided the employee remains employed with the Company. The fair values of the RSUs are measured on the date of grant and are based on the Company's closing stock price on such date. Compensation expense for RSUs with only service conditions is recognized straight-line over the applicable service period. The Company accounts for forfeitures of RSUs when they occur. Previously recognized compensation expense for forfeited RSUs are reversed in the period the RSUs are forfeited. Net Loss Per Share Net loss per share is computed by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as warrants, stock options and unvested restricted stock that would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation as the impact is anti-dilutive. The following potentially dilutive securities outstanding have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive (in thousands): Three Months Ended March 31, 2021 2020 Common stock warrants 561 1,120 Stock options 486 194 RSUs 210 170 1,257 1,484 Recent Accounting Standards Adopted and Recent Accounting Standards Not Yet Adopted Recent Accounting Standards Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes which among other things, eliminates certain exceptions in the current rules regarding the approach for intraperiod tax allocations and the methodology for calculating income taxes in an interim period, and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard was adopted by the Company on January 1, 2021. This new standard did not have a material impact on the Company’s financial statements. Recent accounting standards not yet adopted In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity which among other things, simplifies the accounting models for the allocation of proceeds attributable to the issuance of a convertible debt instrument. As a result, after adopting the ASU’s guidance, entities will not separately present in equity an embedded conversion feature in such debt. Instead, they will account for a convertible debt instrument wholly as debt, and for convertible preferred stock wholly as preferred stock (i.e., as a single unit of account), unless (i) a convertible instrument contains features that require bifurcation as a derivative under ASC 815 or (ii) a convertible debt instrument was issued at a substantial premium. The standard becomes effective for the Company in the first quarter of 2022 and early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of this standard on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following tables present information about the Company's assets and liabilities measured at fair value on a recurring basis in the consolidated balance sheets (in thousands): Description March 31, 2021 Quoted Prices In Significant Other Unobservable Assets: Cash equivalents $ 27,680 $ 27,680 $ — $ — Restricted cash equivalents 100 100 — — Total assets measured and recorded at fair value $ 27,780 $ 27,780 $ — $ — Liabilities: Warrant liability $ 86 $ — $ — $ 86 Contingent consideration 4,762 — — 4,762 Total liabilities measured and recorded at fair value $ 4,848 $ — $ — $ 4,848 Description December 31, 2020 Quoted Prices In Significant Other Unobservable Assets: Cash equivalents $ 34,959 $ 34,959 $ — $ — Restricted cash equivalents 100 100 — — Total assets measured and recorded at fair value $ 35,059 $ 35,059 $ — $ — Liabilities: Warrant liability $ 55 $ — $ — $ 55 Contingent consideration 4,633 — — 4,633 Total liabilities measured and recorded at fair value $ 4,688 $ — $ — $ 4,688 The Company did not transfer any financial instruments into or out of Level 3 classification during the three months ended March 31, 2021 or during the year ended December 31, 2020. See Note 8, Warrants to Acquire Shares of Common Stock, for a reconciliation of the changes in the fair value of the warrant liability for the three months ended March 31, 2021. A reconciliation of the change in the fair value of the contingent consideration liability for the three months ended March 31, 2021 is as follows (in thousands): Fair Value Contingent consideration, December 31, 2020 $ 4,633 Change in the estimated fair value of the contingent consideration 129 Contingent consideration, March 31, 2021 $ 4,762 The fair value of the contingent consideration is measured at the end of each reporting period using Level 3 inputs in a probability-weighted, discounted cash-outflow model. The contingent consideration relates to Galena's acquisition of Apthera, Inc. in 2011 and the future contingent payments of up to $32.0 million based on the achievement of certain development and commercial milestones relating to the Company’s NPS product candidate, of which $2.0 million has been paid to date. The remaining contingent consideration of up to $30.0 million is payable at the election of the Company in either cash or shares of common stock, provided that the Company may not issue any shares in satisfaction of any contingent consideration, unless it has first obtained approval from its stockholders in accordance with Rule 5635(a) of the Nasdaq Marketplace Rules. The significant unobservable assumptions include the probability of achieving each milestone, the date the Company expects to reach the milestone, and a determination of present value factors used to discount future expected cash outflows. Changes in fair value reflect new information about the probability and anticipated timing of meeting the conditions of the milestone payments. In the absence of new information, changes in fair value will only reflect the interest component of contingent consideration related to the passage of time. As of March 31, 2021, estimated future contingent milestone payments related to the Company's business range from zero, if no milestone events are achieved, to a maximum of $30.0 million if all development and commercial milestones are reached. As of March 31, 2021, resulting probability-weighted cash flows were discounted using a weighted average cost of capital of 11.8% for development milestones and cost of debt of 5.4% for the commercial milestones. The Company estimates the timing of achievement of these development milestones to range from five

Balance Sheet Accounts

Balance Sheet Accounts	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Accounts	Balance Sheet Accounts Prepaid expenses and other current assets consist of the following (in thousands): March 31, 2021 December 31, 2020 Insurance $ 1,273 $ 221 Clinical trial costs 1,645 95 Professional fees 68 49 Other 30 30 Prepaid expenses and other current assets $ 3,016 $ 395 Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2021 December 31, 2020 Clinical trial costs $ 1,660 $ 631 Compensation and related benefits 391 812 Professional fees 296 276 Other 200 194 Accrued expenses and other current liabilities $ 2,547 $ 1,913

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases During the second quarter of 2020, the Company entered into a non-cancelable operating lease for certain executive, administrative, and general business office space for its headquarters in New York, New York, which began on June 5, 2020 and has a term through December 31, 2024. At inception, the Company recognized a current operating lease liability of $0.1 million and a non-current operating lease liability of $0.9 million with a corresponding right of use asset ("ROU") of $1.0 million, which is based on the present value of the minimum rental payments of the lease. The discount rate of the Company's operating lease under ASC 842: Leases is the Company's estimated incremental borrowing rate of 13%. As of March 31, 2021, the lease has a remaining term of 3.76 years. Rent expense related to the Company's operating lease was approximately $0.1 million for each of the three months ended March 31, 2021 and 2020. The Company made cash payments related to its operating lease of approximately $0.1 million for each of the three months ended March 31, 2021 and 2020. Future minimum lease payments under the Company's non-cancelable operating lease are as follows as of March 31, 2021 (in thousands): Future minimum lease payments: 2021 (remaining) $ 227 2022 311 2023 321 2024 330 Total future minimum lease payments 1,189 Less: imputed interest (240) Current and non-current operating lease liability $ 949 Legal Proceedings From time to time, the Company is subject to various pending or threatened legal actions and proceedings, including those that arise in the ordinary course of its business, which may include employment matters, breach of contract disputes and stockholder litigation. Such actions and proceedings are subject to many uncertainties and to outcomes that are not predictable with assurance and that may not be known for extended periods of time. The Company records a liability in its consolidated financial statements for costs related to claims, including future legal costs, settlements and judgments, when the Company has assessed that a loss is probable and an amount can be reasonably estimated. If the reasonable estimate of a probable loss is a range, the Company records the most probable estimate of the loss or the minimum amount when no amount within the range is a better estimate than any other amount. The Company discloses a contingent liability even if the liability is not probable or the amount is not estimable, or both, if there is a reasonable possibility that a material loss may have been incurred. In the opinion of management, as of the date hereof, the amount of liability, if any, with respect to these matters, individually or in the aggregate, will not materially affect the Company’s consolidated results of operations, financial position or cash flows. The Company’s predecessor company, Galena, was involved in multiple legal proceedings and administrative actions, including stockholder class actions, both state and federal. The remaining legal proceedings to which the Company is now subject are as follows: On February 13, 2017, certain putative shareholder securities class action complaints were filed in federal court alleging, among other things, that Galena and certain of Galena's former officers and directors failed to disclose that Galena’s promotional practices for Abstral® (fentanyl sublingual tablets) were allegedly improper and that Galena may be subject to civil and criminal liability, and that these alleged failures rendered Galena’s statements about its business misleading. The actions were consolidated, lead plaintiffs were named by the U.S. District Court for the District of New Jersey and a consolidated complaint was filed. The Company filed a motion to dismiss the consolidated complaint. On August 21, 2018, the Company's motion to dismiss the consolidated complaint was granted without prejudice to file an amended complaint. On September 20, 2018, the plaintiffs filed an amended complaint. On October 22, 2018, the Company filed a motion to dismiss the amended complaint. On November 13, 2019, the U.S. District Court for the District of New Jersey granted the Company's motion to dismiss without prejudice to file an amended complaint. On December 20, 2019, the lead plaintiffs filed a second Amended Consolidated Class Action Complaint. On January 29, 2020, the Company filed a motion to dismiss the amended complaint. On January 5, 2021, the U.S. District Court for the District of New Jersey granted the Company's motion to dismiss without prejudice to file an amended complaint. On February 18, 2021, the lead plaintiffs filed a third Amended Consolidated Class Action Complaint. The Company has reached a settlement in principle with the plaintiffs in this action which is subject to final documentation and court approval. In March 2017, a derivative complaint was filed in the U.S. District Court for the District of New Jersey against the Company’s former directors and Galena, as a nominal defendant. In July 2017, a derivative complaint was filed in California state court against the Company’s former directors and Galena, as a nominal defendant. In January 2018, a derivative complaint was filed in the U.S. District Court for the District of New Jersey against the Company’s former directors, officers and employees, and the Company as a nominal defendant. These complaints purport to assert derivative claims for breach of fiduciary duty on the Company’s behalf against the Company’s former directors and, in certain of the complaints, the Company’s current directors, and the Company’s former officers and former employees, based on substantially similar facts as alleged in the putative shareholder securities class action complaints mentioned above. The derivative lawsuit filed in California state court is currently stayed pending resolution of a motion to dismiss in the referenced securities class action. On July 13, 2020 and July 16, 2020, respectively, the Company filed motions to dismiss the two complaints filed in the U.S. District Court for the District of New Jersey. The Company has reached a settlement in principle with the plaintiffs in these three cases which is subject to final documentation and court approval.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock The Company has authorized up to 5,000,000 shares of preferred stock, $0.0001 par value per share, for issuance. Common Stock The Company has authorized up to 350,000,000 shares of common stock, $0.0001 par value per share, for issuance. As of March 31, 2021, the Company has shares of common stock reserved for future issuance as follows (in thousands): Warrants outstanding 561 Stock options outstanding 486 RSUs outstanding 210 Shares reserved for future issuance under the Company’s 2019 Equity Incentive Plan 495 Shares reserved for future issuance under the Employee Stock Purchase Plan 11 Total common stock reserved for future issuance 1,763

Warrants to Acquire Shares of C

Warrants to Acquire Shares of Common Stock	3 Months Ended
	Mar. 31, 2021
Warrants and Rights Note Disclosure [Abstract]
Warrants to Acquire Shares of Common Stock	Warrants to Acquire Shares of Common Stock Warrants Outstanding The following is a summary of the activity of the Company's warrants to acquire shares of common stock for the three months ended March 31, 2021 (in thousands): Warrant Issuance Outstanding, December 31, 2020 Granted Exercised Canceled/Expired Outstanding, March 31, 2021 Expiration July 2020 PIPE Offering 445 — (420) — 25 August 2025 January 2020 Offering 719 — (410) — 309 July 2025 June 2019 Offering 2 — — — 2 June 2024 March 2019 Exercise Agreement 63 — — — 63 March 2024 July 2018 Offering 141 — — — 141 July 2023 Other 22 — — (1) 21 November 2023 1,392 — (830) (1) 561 Warrants to acquire shares of common stock consist of warrants that may be settled in cash, which are liability-classified warrants, and equity-classified warrants. Warrants Classified as Equity Warrants to acquire shares of common stock issued during the 2020, 2019 and July 2018 offerings were recorded as equity upon issuance. During its evaluation of equity classification of these warrants to acquire shares of common stock, the Company considered the conditions as prescribed within ASC 815-40, Derivatives and Hedging, Contracts in an Entity’s own Equity (“ASC 815-40”). The conditions within ASC 815-40 are not subject to a probability assessment. The warrants to acquire shares of common stock do not fall under the liability criteria within ASC 480, Distinguishing Liabilities from Equity , as they are not puttable and do not represent an instrument that has a redeemable underlying security. The warrants to acquire shares of common stock do meet the definition of a derivative instrument under ASC 815, but are eligible for the scope exception as they are indexed to the Company’s own stock and would be classified in permanent equity if freestanding. Warrants Classified as Liabilities Liability-classified warrants consist of warrants to acquire common stock issued in connection with certain previous equity financings. These warrants may be settled in cash and were determined not to be indexed to the Company’s common stock. The estimated fair value of outstanding warrants accounted for as liabilities is determined at each balance sheet date. Any decrease or increase in the estimated fair value of the warrant liability since the most recent balance sheet date is recorded in the consolidated statement of operations as change in fair value of warrant liability. The fair value of the warrants is estimated using a Black-Scholes pricing model with the following inputs: As of March 31, 2021 Warrant Issuance Outstanding (in thousands) Strike price (per share) Expected term (years) Volatility % Risk-free rate % Other warrants (liability-classified) 13 $ 7.50 2.50 149.40 % 0.25 % As of December 31, 2020 Warrant Issuance Outstanding (in thousands) Strike price (per share) Expected term (years) Volatility % Risk-free rate % Other warrants (liability-classified) 13 $ 7.50 2.75 150.38 % 0.16 % The expected volatility assumptions are based on the Company's implied volatility in combination with the implied volatilities of similar publicly traded entities. The expected life assumption is based on the remaining contractual terms of the warrants. The risk-free rate is based on the zero coupon rates in effect at the time of valuation. The dividend yield used in the pricing model is zero, because the Company has no present intention to pay cash dividends. The changes in fair value of the warrant liability for the three months ended March 31, 2021 were as follows (in thousands): Warrant Issuance Warrant liability, December 31, 2020 Change in fair value of warrants Warrant liability, March 31, 2021 Other warrants (liability-classified) $ 55 $ 31 $ 86 $ 55 $ 31 $ 86

License Revenue with 3D Medicin

License Revenue with 3D Medicines, Inc.	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
License Revenue with 3D Medicines, Inc.	License Revenue with 3D Medicines, Inc. Exclusive License Agreement with 3D Medicines, Inc. In December 2020, the Company, together with its wholly-owned subsidiary, SLSG Limited, LLC, entered into an Exclusive License Agreement (the “3DMed License Agreement”) with 3D Medicines Inc. ("3DMed"), pursuant to which the Company granted 3DMed a sublicensable, royalty-bearing license, under certain intellectual property owned or controlled by the Company, to develop, manufacture and have manufactured, and commercialize GPS and heptavalent GPS ("GPS Plus") product candidates ("GPS Licensed Products") for all therapeutic and other diagnostic uses in mainland China, Hong Kong, Macau and Taiwan ("3DMed Territory"). The license is exclusive, except with respect to certain know-how that has been non-exclusively licensed to the Company and is sublicensed to 3DMed on a non-exclusive basis. The Company has retained development, manufacturing and commercialization rights with respect to the GPS Licensed Products in the rest of the world. In partial consideration for the rights granted by the Company, 3DMed agreed to pay the Company (i) a one-time upfront cash payment of $7.5 million, and (ii) milestone payments totaling up to $194.5 million in the aggregate upon the achievement of certain technology transfer, development and regulatory milestones, as well as sales milestones based on certain net sales thresholds of GPS Licensed Products in the 3DMed Territory in a given calendar year. The Company is responsible for providing the licensed technology and data (the "3DMed License") as well as transferring certain technological and manufacturing know-how (the "transfer of know-how"). 3DMed also agreed to pay tiered royalties based upon a percentage of annual net sales of GPS Licensed Products in the 3DMed Territory ranging from the high single digits to the low double digits. The royalties are payable on a GPS Licensed Product-by-GPS Licensed Product and region-by-region basis commencing on the first commercial sale of a GPS Licensed Product in a region and continuing until the latest of (i) the date that is 15 years from the receipt of marketing authorization for such GPS Licensed Product in such region and (ii) the date that is 10 years from the expiration of the last valid claim of a licensed patent covering or claiming such GPS Licensed Product in such region. The royalty rate is subject to reduction under certain circumstances, including when generic competition for a GPS Licensed Product exists in a particular region. 3DMed is responsible for all costs related to developing, obtaining regulatory approval of and commercializing the GPS Licensed Products in the 3DMed Territory. 3DMed is required to use commercially reasonable best efforts to develop and obtain regulatory approval for, and upon receipt of regulatory approval, commercialize the GPS Licensed Products in the 3DMed Territory. A joint steering committee has been established between 3DMed and the Company to coordinate and review the development, manufacturing and commercialization plans with respect to the GPS Licensed Products in the 3DMed Territory. The Company and 3DMed also agreed to negotiate in good faith the terms and conditions of a clinical supply agreement, a commercial supply agreement, and related quality agreements pursuant to which the Company will manufacture or have manufactured and supply 3DMed with all quantities of the GPS Licensed Products necessary for 3DMed to develop and commercialize the GPS Licensed Products in the 3DMed Territory until 3DMed has received all approvals required for 3DMed or its designated contract manufacturing organization to manufacture the GPS Licensed Products in the 3DMed Territory. The 3DMed License Agreement will expire on a GPS Licensed Product-by-GPS Licensed Product and region-by-region basis on the date of the expiration of all of 3DMed’s payment obligations to the Company. Upon expiration of the 3DMed License Agreement, the license granted to 3DMed will become fully paid-up, perpetual and irrevocable. Either party may terminate the 3DMed License Agreement for the other party’s material breach following a cure period or upon certain insolvency events. The Company may terminate the 3DMed License Agreement if 3DMed or its affiliates or sublicensees challenge the validity or enforceability of the licensed patents. At any time following the two-year anniversary of the effective date, 3DMed has the right to terminate the 3DMed License Agreement for convenience, subject to certain requirements. 3DMed may terminate the 3DMed License Agreement upon prior notice to the Company if the grant of the license to 3DMed is prohibited or delayed for a period of time due to a change of U.S. export laws and regulations. The 3DMed License Agreement includes customary representations and warranties, covenants and indemnification obligations for a transaction of this nature. Revenue Recognition The Company evaluated the 3DMed License Agreement and concluded that 3DMed was a customer and the 3DMed License Agreement should be evaluated under ASC 606. In determining the appropriate amount of revenue to be recognized under ASC 606 as the Company fulfills its obligations under the 3DMed License Agreement, the Company performs the following steps: (i) identifies the promised goods or services in the contract; (ii) determines whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measures the transaction price, including any constraints on variable consideration; (iv) allocates the transaction price to the performance obligations; and (v) recognizes revenue when (or as) the Company satisfies each performance obligation. The Company identified the 3DMed License and the transfer of know-how to be the material promises under the 3DMed License Agreement. The Company determined that the 3DMed License and the transfer of know-how are not distinct from each other. As such, for the purposes of ASC 606, the Company determined that these two material promises, described above, should be combined into a single performance obligation. The Company determined the initial transaction price of the single performance obligation to be $9.5 million, which includes the $7.5 million upfront fee as well as $2.0 million in development milestones that are assessed to be probable of being achieved at the inception of the 3DMed License Agreement and therefore were not constrained. The Company achieved $1.0 million of these milestones in the first quarter of 2021 and expects to achieve the remaining $1.0 million in the second quarter of 2021. The Company determined that $192.5 million in future certain development, regulatory, and sales milestones to be variable consideration subject to constraint at inception. At the end of each subsequent reporting period, the Company will reevaluate the probability of achievement of the future development, regulatory, and sales milestones subject to constraint and, if necessary, will adjust its estimate of the overall transaction price. Any such adjustments will be recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. For the sales-based royalties, the Company will recognize revenue when the related sales occur. To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Since 3DMed is benefiting from the combined single performance obligation relating to the 3DMed License and the transfer of know-how as the technology transfer occurs, the Company is recognizing the transaction price over the technology transfer period, which is expected to be finalized in the second quarter of 2021. The revenue recognized is based on an output method to measure progress, using a straight-line convention, which the Company believes reasonably approximates its efforts in satisfying the combined performance obligation. The Company recognized $5.7 million of license revenue during the three months ended March 31, 2021. There was no license revenue recognized during the three months ended March 31, 2020. The following table presents a summary of the activity in the Company's deferred revenue, related to the total cash payments received of $8.5 million to date under the 3DMed License, during the three months ended March 31, 2021 (in thousands): December 31, 2020 Additions Revenue Recognized March 31, 2021 Deferred Revenue $ 5,600 $ 1,000 $ (5,700) $ 900 Cost of Contract Acquisition The Company incurred contract acquisition costs (commissions) recorded as a contract asset amounting to approximately $1.4 million at inception of the 3DMed License Agreement which were capitalized under ASC 340-40 as incremental costs of obtaining the 3DMed License Agreement. These costs are amortized through general and administrative expense over the technology transfer period, commensurate with when the license revenue is recognized. The Company recognized $0.8 million in expense associated with these costs during the three months ended March 31, 2021. There was no contract acquisitions expense during the three months ended March 31, 2020. Cost of License Revenue The Company incurred $0.1 million of sublicensing fees payable under our license from MSK in connection with the 3DMed License during the three months ended March 31, 2021. There was no cost of license revenue during the three months ended March 31, 2020.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation 2017 Equity Incentive Plan On December 29, 2017, the 2017 Equity Incentive Plan was approved by the stockholders of the Company, which provided for the issuance of up to a maximum of 24,204 shares of common stock underlying stock options granted prior to September 10, 2019. The 2017 Equity Incentive Plan was terminated upon the approval of the 2019 Incentive Plan subject to outstanding stock options granted under the 2017 Equity Incentive Plan that remain exercisable through maturity for the Company's employees and directors. 2019 Equity Incentive Plan On September 10, 2019, the 2019 Equity Incentive Plan was approved by the stockholders of the Company, which currently allows for issuance of up to approximately (i) 1,191,000 shares of common stock in connection with the grant of stock-based awards, including stock options, restricted stock, restricted stock units, stock appreciation rights and other types of awards as deemed appropriate plus (ii) 2,684 shares of common stock under the 2017 Equity Incentive Plan that were forfeited back to the Company subsequent to September 10, 2019 and are available for future issuance. The number of shares reserved for issuance under the 2019 Equity Incentive Plan will automatically increase on January 1 of each year, for a period of not more than four years, commencing on January 1, 2020 and ending on (and including) January 1, 2023, by an amount equal to the lesser of (i) 5% of the total number of shares of common stock outstanding at the end of the prior fiscal year; and (ii) an amount determined by the board of directors or authorized committee. As of March 31, 2021, approximately 495,000 shares of common stock were reserved for future grants under the 2019 Equity Incentive Plan. Options to Purchase Shares of Common Stock The following table summarizes stock option activity of the Company for the three months ended March 31, 2021: Total Weighted Weighted Average Remaining Contractual Term (In Years) Aggregate Outstanding at December 31, 2020 208 $ 13.38 9.08 $ 733 Granted 278 8.00 Outstanding at March 31, 2021 486 $ 10.30 9.46 $ 1,390 Options exercisable at March 31, 2021 76 $ 23.83 8.73 $ 416 The aggregate intrinsic values of outstanding and exercisable stock options at March 31, 2021 were calculated based on the closing price of the Company’s common stock as reported on the Nasdaq Capital Market on March 31, 2021 of $8.54 per share. The aggregate intrinsic value equals the positive difference between the closing fair market value of the Company’s common stock and the exercise price of the underlying stock options. The following table summarizes the components of stock-based compensation expense in the consolidated statements of operations for the three months ended March 31, 2021 and 2020, respectively (in thousands): Three Months Ended March 31, 2021 2020 Research and development $ 14 $ 1 General and administrative 170 144 Total stock-based compensation $ 184 $ 145 The Company uses the Black-Scholes option-pricing model to determine the fair value of all its stock options granted. The assumptions used during the three months ended March 31, 2021 and 2020, respectively, were as follows: Three Months Ended March 31, 2021 2020 Risk free interest rate 1.03 % 0.63 % Volatility 121.20 % 106.09 % Expected lives (years) 6.17 6.13 Expected dividend yield — % — % The weighted-average grant date fair value of options granted during the three months ended March 31, 2021 and 2020 was $6.98 and $1.54, respectively. The Company’s expected common stock price volatility assumption is based upon the Company's own implied volatility in combination with the implied volatility of a basket of comparable companies. The expected life assumptions for employee grants were based upon the simplified method, which averages the contractual term of the Company’s options of ten years with the average vesting term of four years for an average of approximately six years. The expected life assumptions for non-employees were based upon the contractual term of the option. The dividend yield assumption is zero because the Company has never paid cash dividends and presently has no intention to do so. The risk-free interest rate used for each grant was also based upon prevailing short-term interest rates. The Company accounts for forfeitures as they occur. As of March 31, 2021, there was $2.5 million of unrecognized compensation cost related to outstanding stock options that is expected to be recognized as a component of the Company’s operating expenses over a weighted-average period of 3.08 years. Time-vested RSUs and RSUs with Performance Conditions The following table summarizes RSU activity of the Company for the three months ended March 31, 2021: Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2020 170 $ 1.89 Granted 40 $ 8.00 Vested — $ — Unvested at March 31, 2021 210 $ 3.06 As of March 31, 2021, there was $0.6 million of unrecognized compensation cost related to outstanding RSUs. No RSUs vested during the three months ended March 31, 2021.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company evaluated all events or transactions that occurred after March 31, 2021 up through the date these financial statements were issued. Other than as disclosed elsewhere in the notes to the consolidated financial statements, the Company did not have any material subsequent events.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification ("ASC") and Accounting Standards Updates ("ASU") of the Financial Accounting Standards Board ("FASB").
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the financial statements of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated upon consolidation. Unless the context otherwise indicates, reference in these notes to the "Company" refer to SELLAS Life Sciences Group, Inc., and its wholly owned subsidiaries, Private SELLAS, SLSG Limited, LLC, Sellas Life Sciences Limited, and Apthera, Inc. The functional currency of the Company's non-U.S. operations is the U.S. dollar.
Time-Vested Restricted Stock Units	Time-Vested Restricted Stock Units During the three months ended March 31, 2021, the Board of Directors granted restricted stock units ("RSUs") to employees that vest based on continuous service. Time-vested RSUs awarded to employees vest one-fourth per year annually over four years, provided the employee remains employed with the Company. The fair values of the RSUs are measured on the date of grant and are based on the Company's closing stock price on such date. Compensation expense for RSUs with only service conditions is recognized straight-line over the applicable service period. The Company accounts for forfeitures of RSUs when they occur. Previously recognized compensation expense for forfeited RSUs are reversed in the period the RSUs are forfeited.
Net Loss Per Share	Net Loss Per Share Net loss per share is computed by dividing net loss applicable to common stockholders by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as warrants, stock options and unvested restricted stock that would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation as the impact is anti-dilutive.
Recent Accounting Pronouncements Adopted and Recent Accounting Standards Not Yet Adopted	Recent Accounting Standards Adopted and Recent Accounting Standards Not Yet Adopted Recent Accounting Standards Adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes which among other things, eliminates certain exceptions in the current rules regarding the approach for intraperiod tax allocations and the methodology for calculating income taxes in an interim period, and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard was adopted by the Company on January 1, 2021. This new standard did not have a material impact on the Company’s financial statements. Recent accounting standards not yet adopted In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity which among other things, simplifies the accounting models for the allocation of proceeds attributable to the issuance of a convertible debt instrument. As a result, after adopting the ASU’s guidance, entities will not separately present in equity an embedded conversion feature in such debt. Instead, they will account for a convertible debt instrument wholly as debt, and for convertible preferred stock wholly as preferred stock (i.e., as a single unit of account), unless (i) a convertible instrument contains features that require bifurcation as a derivative under ASC 815 or (ii) a convertible debt instrument was issued at a substantial premium. The standard becomes effective for the Company in the first quarter of 2022 and early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of this standard on its consolidated financial statements.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Schedule of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted Average Shares Outstanding	The following potentially dilutive securities outstanding have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive (in thousands): Three Months Ended March 31, 2021 2020 Common stock warrants 561 1,120 Stock options 486 194 RSUs 210 170 1,257 1,484

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value	The following tables present information about the Company's assets and liabilities measured at fair value on a recurring basis in the consolidated balance sheets (in thousands): Description March 31, 2021 Quoted Prices In Significant Other Unobservable Assets: Cash equivalents $ 27,680 $ 27,680 $ — $ — Restricted cash equivalents 100 100 — — Total assets measured and recorded at fair value $ 27,780 $ 27,780 $ — $ — Liabilities: Warrant liability $ 86 $ — $ — $ 86 Contingent consideration 4,762 — — 4,762 Total liabilities measured and recorded at fair value $ 4,848 $ — $ — $ 4,848 Description December 31, 2020 Quoted Prices In Significant Other Unobservable Assets: Cash equivalents $ 34,959 $ 34,959 $ — $ — Restricted cash equivalents 100 100 — — Total assets measured and recorded at fair value $ 35,059 $ 35,059 $ — $ — Liabilities: Warrant liability $ 55 $ — $ — $ 55 Contingent consideration 4,633 — — 4,633 Total liabilities measured and recorded at fair value $ 4,688 $ — $ — $ 4,688
Reconciliation of Level 3 Liabilities	A reconciliation of the change in the fair value of the contingent consideration liability for the three months ended March 31, 2021 is as follows (in thousands): Fair Value Contingent consideration, December 31, 2020 $ 4,633 Change in the estimated fair value of the contingent consideration 129 Contingent consideration, March 31, 2021 $ 4,762

Balance Sheet Accounts (Tables)

Balance Sheet Accounts (Tables)	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): March 31, 2021 December 31, 2020 Insurance $ 1,273 $ 221 Clinical trial costs 1,645 95 Professional fees 68 49 Other 30 30 Prepaid expenses and other current assets $ 3,016 $ 395
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2021 December 31, 2020 Clinical trial costs $ 1,660 $ 631 Compensation and related benefits 391 812 Professional fees 296 276 Other 200 194 Accrued expenses and other current liabilities $ 2,547 $ 1,913

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Future minimum lease payments under the Company's non-cancelable operating lease are as follows as of March 31, 2021 (in thousands): Future minimum lease payments: 2021 (remaining) $ 227 2022 311 2023 321 2024 330 Total future minimum lease payments 1,189 Less: imputed interest (240) Current and non-current operating lease liability $ 949

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	As of March 31, 2021, the Company has shares of common stock reserved for future issuance as follows (in thousands): Warrants outstanding 561 Stock options outstanding 486 RSUs outstanding 210 Shares reserved for future issuance under the Company’s 2019 Equity Incentive Plan 495 Shares reserved for future issuance under the Employee Stock Purchase Plan 11 Total common stock reserved for future issuance 1,763

Warrants to Acquire Shares of_2

Warrants to Acquire Shares of Common Stock (Tables)	3 Months Ended
	Mar. 31, 2021
Warrants and Rights Note Disclosure [Abstract]
Schedule of Warrant Activity Table	The following is a summary of the activity of the Company's warrants to acquire shares of common stock for the three months ended March 31, 2021 (in thousands): Warrant Issuance Outstanding, December 31, 2020 Granted Exercised Canceled/Expired Outstanding, March 31, 2021 Expiration July 2020 PIPE Offering 445 — (420) — 25 August 2025 January 2020 Offering 719 — (410) — 309 July 2025 June 2019 Offering 2 — — — 2 June 2024 March 2019 Exercise Agreement 63 — — — 63 March 2024 July 2018 Offering 141 — — — 141 July 2023 Other 22 — — (1) 21 November 2023 1,392 — (830) (1) 561
Fair Value of Warrants is Estimated Using Black-Scholes Option Pricing Model	The fair value of the warrants is estimated using a Black-Scholes pricing model with the following inputs: As of March 31, 2021 Warrant Issuance Outstanding (in thousands) Strike price (per share) Expected term (years) Volatility % Risk-free rate % Other warrants (liability-classified) 13 $ 7.50 2.50 149.40 % 0.25 % As of December 31, 2020 Warrant Issuance Outstanding (in thousands) Strike price (per share) Expected term (years) Volatility % Risk-free rate % Other warrants (liability-classified) 13 $ 7.50 2.75 150.38 % 0.16 %
Changes in Fair Value of Warrant Liability	The changes in fair value of the warrant liability for the three months ended March 31, 2021 were as follows (in thousands): Warrant Issuance Warrant liability, December 31, 2020 Change in fair value of warrants Warrant liability, March 31, 2021 Other warrants (liability-classified) $ 55 $ 31 $ 86 $ 55 $ 31 $ 86

License Revenue with 3D Medic_2

License Revenue with 3D Medicines, Inc. (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Deferred Revenue, Related to Upfront Cash Payment Received	The following table presents a summary of the activity in the Company's deferred revenue, related to the total cash payments received of $8.5 million to date under the 3DMed License, during the three months ended March 31, 2021 (in thousands): December 31, 2020 Additions Revenue Recognized March 31, 2021 Deferred Revenue $ 5,600 $ 1,000 $ (5,700) $ 900

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity of the Company for the three months ended March 31, 2021: Total Weighted Weighted Average Remaining Contractual Term (In Years) Aggregate Outstanding at December 31, 2020 208 $ 13.38 9.08 $ 733 Granted 278 8.00 Outstanding at March 31, 2021 486 $ 10.30 9.46 $ 1,390 Options exercisable at March 31, 2021 76 $ 23.83 8.73 $ 416
Schedule of Allocated Stock-based Compensation Expense	The following table summarizes the components of stock-based compensation expense in the consolidated statements of operations for the three months ended March 31, 2021 and 2020, respectively (in thousands): Three Months Ended March 31, 2021 2020 Research and development $ 14 $ 1 General and administrative 170 144 Total stock-based compensation $ 184 $ 145
Assumptions for Option Grants Issued	The Company uses the Black-Scholes option-pricing model to determine the fair value of all its stock options granted. The assumptions used during the three months ended March 31, 2021 and 2020, respectively, were as follows: Three Months Ended March 31, 2021 2020 Risk free interest rate 1.03 % 0.63 % Volatility 121.20 % 106.09 % Expected lives (years) 6.17 6.13 Expected dividend yield — % — %
Summary of RSU Activity	The following table summarizes RSU activity of the Company for the three months ended March 31, 2021: Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2020 170 $ 1.89 Granted 40 $ 8.00 Vested — $ — Unvested at March 31, 2021 210 $ 3.06

Liquidity (Details)

Liquidity (Details) - USD ($) $ in Thousands	Oct. 29, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accumulated deficit		$ 120,307		$ 117,904
Net loss		2,403	$ 4,143
Net cash used in operating activities		10,269	6,831
Contract acquisition costs		1,400
Increase in prepaid expenses and other current assets		2,683	$ 1,350
Decrease in accounts payable and accrued expenses		300
Cash and cash equivalents		28,033		35,302
Restricted cash and cash equivalents		$ 100		$ 100
Sales Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of shares, common stock gross proceeds	$ 50,000
Percentage gross proceeds from the sale of share (as a percent)	3.00%

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Narrative (Details)	3 Months Ended
	Mar. 31, 2021
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Restricted stock unit award vested period	4 years

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	1,257	1,484
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	561	1,120
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	486	194
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	210	170

Fair Value Measurements - Conti

Fair Value Measurements - Contingent Purchase Price Consideration, Measured at Estimated Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Liabilities:
Warrant liability	$ 86	$ 55
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	27,680	34,959
Restricted cash equivalents	100	100
Total assets measured and recorded at fair value	27,780	35,059
Liabilities:
Warrant liability	86	55
Contingent consideration	4,762	4,633
Total liabilities measured and recorded at fair value	4,848	4,688
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets (Level 1)
Assets:
Cash equivalents	27,680	34,959
Restricted cash equivalents	100	100
Total assets measured and recorded at fair value	27,780	35,059
Liabilities:
Warrant liability	0	0
Contingent consideration	0	0
Total liabilities measured and recorded at fair value	0	0
Fair Value, Measurements, Recurring | Significant Other Observable  Inputs (Level 2)
Assets:
Cash equivalents	0	0
Restricted cash equivalents	0	0
Total assets measured and recorded at fair value	0	0
Liabilities:
Warrant liability	0	0
Contingent consideration	0	0
Total liabilities measured and recorded at fair value	0	0
Fair Value, Measurements, Recurring | Unobservable  Inputs (Level 3)
Assets:
Cash equivalents	0	0
Restricted cash equivalents	0	0
Total assets measured and recorded at fair value	0	0
Liabilities:
Warrant liability	86	55
Contingent consideration	4,762	4,633
Total liabilities measured and recorded at fair value	$ 4,848	$ 4,688

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Level 3 Liabilities (Details) - Unobservable  Inputs (Level 3) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration, December 31, 2020	$ 4,633
Change in the estimated fair value of the contingent consideration	129
Contingent consideration, March 31, 2021	$ 4,762

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - Apthera, Inc.	3 Months Ended
	Mar. 31, 2021USD ($)	Dec. 31, 2011USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration payable, maximum amount	$ 30,000,000	$ 32,000,000
Contingent consideration paid	2,000,000
Contingent consideration	30,000,000
Contingent consideration payable, minimum amount	$ 0
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration, timing of development milestones	5 years
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration, timing of development milestones	8 years
Weighted average cost of capital
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration, measurement input (as a percent)	0.118
Cost of debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business combination, contingent consideration, measurement input (as a percent)	0.054

Balance Sheet Accounts - Prepai

Balance Sheet Accounts - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Insurance	$ 1,273	$ 221
Clinical trial costs	1,645	95
Professional fees	68	49
Other	30	30
Prepaid expenses and other current assets	$ 3,016	$ 395

Balance Sheet Accounts - Accrue

Balance Sheet Accounts - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Clinical trial costs	$ 1,660	$ 631
Compensation and related benefits	391	812
Professional fees	296	276
Other	200	194
Accrued expenses and other current liabilities	$ 2,547	$ 1,913

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	Jul. 16, 2020complaint	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2020USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability		$ 174		$ 166
Operating lease liability, non-current		775		825
Operating lease right-of-use asset		$ 854		$ 896
Number of claims which the Company filed motions to dismiss | complaint	2
Office Space Lease Expiring December 31, 2024
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability					$ 100
Operating lease liability, non-current					900
Operating lease right-of-use asset					$ 1,000
Operating lease, discount rate (as a percent)					13.00%
Operating lease, remaining term		3 years 9 months 3 days
Rent expense		$ 100	$ 100
Cash payments related to operating lease		$ 100	$ 100

Commitments and Contingencies_2

Commitments and Contingencies - Maturities of Lease Liabilities - 842 (Details) $ in Thousands	Mar. 31, 2021USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021 (remaining)	$ 227
2022	311
2023	321
2024	330
Total future minimum lease payments	1,189
Less: imputed interest	(240)
Current and non-current operating lease liability	$ 949

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	350,000,000	350,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock are Reserved for Future Issuance (Details) - shares shares in Thousands	Mar. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	561	1,392
Stock options outstanding (in shares)	486	208
Shares reserved for future issuance under the Company’s 2019 Equity Incentive Plan (in shares)	495
Shares reserved for future issuance under the Employee Stock Purchase Plan (in shares)	11
Total common stock reserved for future issuance (in shares)	1,763
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)	210	170

Warrants to Acquire Shares of_3

Warrants to Acquire Shares of Common Stock - Warrants Outstanding (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2021shares
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	1,392
Granted (in shares)	0
Exercised (in shares)	(830)
Canceled/Expired (in shares)	(1)
Outstanding, end of period (in shares)	561
July 2020 PIPE Offering
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	445
Granted (in shares)	0
Exercised (in shares)	(420)
Canceled/Expired (in shares)	0
Outstanding, end of period (in shares)	25
January 2020 Offering
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	719
Granted (in shares)	0
Exercised (in shares)	(410)
Canceled/Expired (in shares)	0
Outstanding, end of period (in shares)	309
June 2019 Offering
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	2
Granted (in shares)	0
Exercised (in shares)	0
Canceled/Expired (in shares)	0
Outstanding, end of period (in shares)	2
March 2019 Exercise Agreement
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	63
Granted (in shares)	0
Exercised (in shares)	0
Canceled/Expired (in shares)	0
Outstanding, end of period (in shares)	63
July 2018 Offering
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	141
Granted (in shares)	0
Exercised (in shares)	0
Canceled/Expired (in shares)	0
Outstanding, end of period (in shares)	141
Other
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	22
Granted (in shares)	0
Exercised (in shares)	0
Canceled/Expired (in shares)	(1)
Outstanding, end of period (in shares)	21

Warrants to Acquire Shares of_4

Warrants to Acquire Shares of Common Stock - Fair Value of Warrants is Estimated Using Black-Scholes Option Pricing Model (Details) - $ / shares shares in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	561	1,392
Other warrants (liability-classified)
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	13	13
Strike price (in dollars per share)	$ 7.50	$ 7.50
Expected term (years)	2 years 6 months	2 years 9 months
Volatility %	149.40%	150.38%
Risk-free rate %	0.25%	0.16%

Warrants to Acquire Shares of_5

Warrants to Acquire Shares of Common Stock - Narrative (Details)	Mar. 31, 2021
Measurement Input, Risk Free Interest Rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input coupon rate	0
Measurement Input, Expected Dividend Rate
Class of Warrant or Right [Line Items]
Warrants and rights outstanding, measurement input coupon rate	0

Warrants to Acquire Shares of_6

Warrants to Acquire Shares of Common Stock - Changes in Fair Value of Warrant Liability (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Class of Warrant or Right, Fair Value [Roll Forward]
Warrant liability, beginning balance	$ 55
Change in fair value of warrants	31
Warrant liability, ending balance	86
Other warrants (liability-classified)
Class of Warrant or Right, Fair Value [Roll Forward]
Warrant liability, beginning balance	55
Change in fair value of warrants	31
Warrant liability, ending balance	$ 86

License Revenue with 3D Medic_3

License Revenue with 3D Medicines, Inc. - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended
	Dec. 31, 2020	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Upfront cash payment received	$ 7,500,000		$ 8,500,000
Future milestone payments received	$ 194,500,000
Royalties payable, maximum term	15 years
Royalties payable, minimum term	10 years
Performance obligation, amount	$ 9,500,000
Milestones probable of being achieved	$ 2,000,000
Milestone payment received			1,000,000
Potential milestone payments to be received			192,500,000
Licensing revenue			5,700,000	$ 0
Contract acquisition costs			1,400,000
Amortization of contract asset			846,000	0
Cost of licensing revenue			$ 100,000	$ 0
Forecast
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Milestone payment received		$ 1,000,000

License Revenue with 3D Medic_4

License Revenue with 3D Medicines, Inc. - Deferred Revenue (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Movement in Deferred Revenue [Roll Forward]
Beginning balance	$ 5,600,000
Additions	1,000,000
Revenue Recognized	(5,700,000)	$ 0
Ending balance	$ 900,000

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 10, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 29, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)		1,763,000
Closing price of the Company's common stock (in dollars per share)		$ 8.54
Weighted average exercise price, granted (in dollars per share)		$ 6.98	$ 1.54
Averages contractual term		10 years
Expected dividend yield (as a percent)		0.00%	0.00%
Unrecognized compensation cost, options		$ 2.5
Operating expenses weighted average period		3 years 29 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, granted (in dollars per share)		$ 8
Unrecognized compensation cost		$ 0.6
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average vesting term		6 years
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average vesting term		4 years
2017 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)		2,684
2017 Equity Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance (in shares)				24,204
2019 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance (in shares)	1,191,000
Shares of common stock reserved for issuance (in shares)		495,000
Option term	4 years
Increase in number of shares available for future issuance under stock based awards (as a percent)	5.00%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning balance (in shares)	208
Granted (in shares)	278
Options outstanding, ending balance (in shares)	486	208
Options exercisable (in shares)	76
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, beginning balance (in dollars per share)	$ 13.38
Weighted average exercise price, granted (in dollars per share)	8
Weighted average exercise price, ending balance (in dollars per share)	10.30	$ 13.38
Weighted average exercise price, exercisable (in dollars per share)	$ 23.83
Weighted average remaining contractual term, outstanding (in years)	9 years 5 months 15 days	9 years 29 days
Weighted average remaining contractual term, options exercisable (in years)	8 years 8 months 23 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Aggregate Intrinsic Value [Roll Forward]
Aggregate intrinsic value, beginning balance	$ 733
Aggregate intrinsic value, ending balance	1,390	$ 733
Aggregate intrinsic value, options exercisable	$ 416

Stock-Based Compensation - Allo

Stock-Based Compensation - Allocated Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 184	$ 145
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	14	1
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 170	$ 144

Stock-Based Compensation - Assu

Stock-Based Compensation - Assumptions for Option Grants Issued (Details)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Risk free interest rate	1.03%	0.63%
Volatility	121.20%	106.09%
Expected lives (years)	6 years 2 months 1 day	6 years 1 month 17 days
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of RSU Activity (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 6.98	$ 1.54
RSUs
Shares (In Thousands)
Beginning balance (in shares)	170
Granted (in shares)	40
Vested (in shares)	0
Ending balance (in shares)	210
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 1.89
Granted (in dollars per share)	8
Vested (in dollars per share)	0
Ending balance (in dollars per share)	$ 3.06