Form 10-Q - Quarterly report [Sections 13 or 15(d)]

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

________________________________

FORM 10-Q

________________________________


☒			QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2024


☐			TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

Commission File Number: 001-33958

SELLAS Life Sciences Group, Inc.

(Exact name of registrant as specified in its charter)


Delaware						20-8099512
(State of incorporation)						(I.R.S. Employer Identification No.)

7 Times Square, Suite 2503, New York, NY 10036

(646) 200-5278

(Address, including zip code, and telephone number, including

area code, of registrant's principal executive offices)

Securities registered pursuant to Section 12(b) of the Act:


Title of each class	Trading symbol(s)	Name of each exchange on which registered
Common Stock, $0.0001 par value per share	SLS	The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter time that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act:

Large accelerated filer

☐

Accelerated filer

☐

Non-accelerated filer

☒

Smaller reporting company

☒

Emerging growth company

☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act): ☐ Yes ☒ No

As of May 13, 2024, SELLAS Life Sciences Group, Inc. had outstanding 57,754,928 shares of common stock.

SELLAS LIFE SCIENCES GROUP, INC.

FORM 10-Q - Quarterly Report

For the Quarter Ended March 31, 2024

TABLE OF CONTENTS


		Page
	PART I - FINANCIAL INFORMATION
Item 1	Financial Statements	4
	Unaudited Consolidated Balance Sheets as of March 31, 2024 and December 31, 2023	4
	Unaudited Consolidated Statements of Operations for the Three Months Ended March 31, 2024 and 2023	5
	Unaudited Consolidated Statements of Stockholders' Equity (Deficit) for the Three Months Ended March 31, 2024 and 2023	6
	Unaudited Consolidated Statements of Cash Flows for the Three Months Ended March 31, 2024 and 2023	7
	Unaudited Notes to Consolidated Financial Statements	8
Item 2	Management’s Discussion and Analysis of Financial Condition and Results of Operations	19
Item 3	Quantitative and Qualitative Disclosures About Market Risk	27
Item 4	Controls and Procedures	27
	PART II - OTHER INFORMATION
Item 1	Legal Proceedings	29
Item 1A	Risk Factors	29
Item 2	Unregistered Sales of Equity Securities and Use of Proceeds	29
Item 3	Defaults Upon Senior Securities	29
Item 4	Mine Safety Disclosures	29
Item 5	Other Information	29
Item 6	Exhibits	29

	Signatures

The names “SELLAS Life Sciences Group, Inc.,” “SELLAS,” the SELLAS logo, and other trademarks or service marks of SELLAS Life Sciences Group, Inc. appearing in this Quarterly Report on Form 10-Q are the property of SELLAS Life Sciences Group, Inc. Other trademarks, service marks or trade names appearing in this Quarterly Report on Form 10-Q are the property of their respective owners. We do not intend the use or display of other companies’ trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of or by either of, these other companies.

Unless the context otherwise indicates, references in these notes to the “Company,” “we,” “us” or “our” refer to SELLAS Life Sciences Group, Inc. and its wholly owned subsidiaries.

SPECIAL NOTE REGARDING FORWARD LOOKING STATEMENTS

This Quarterly Report on Form 10-Q includes forward-looking statements that reflect our current views with respect to our development programs, business strategy, business plan, financial performance and other future events. These statements include forward-looking statements both with respect to us, specifically, and our industry, in general. Such forward-looking statements include the words "expect," "intend,” "plan," "believe," "project," "estimate,” "may,” "should," "anticipate," "will" and similar statements of a future or forward-looking nature identify forward-looking statements and include, without limitation, statements regarding:

•our future financial and business performance;

•strategic plans for our business and product candidates;

•our ability to develop or commercialize products;

•the expected results and timing of clinical trials and nonclinical studies;

•our ability to comply with the terms of our license agreements;

•developments and projections relating to our competitors and industry;

•our expectations regarding our ability to obtain, develop and maintain intellectual property protection and not infringe on the rights of others;

•our ability to retain and attract highly-skilled executive officers and employees;

•our future capital requirements and the timing of those requirements and sources and uses of cash;

•our ability to obtain funding for our operations; and

•changes in applicable laws or regulations.

These statements are subject to known and unknown risks, uncertainties and assumptions that could cause actual results to differ materially from those projected or otherwise implied by the forward-looking statements, including the following:

•risks associated with preclinical or clinical development and trials;

•changes in the assumptions underlying our expectations regarding our future business or business model;

•our ability to develop, manufacture and commercialize product candidates;

•general economic, financial, legal, political and business conditions and changes in domestic and foreign markets;

•changes in applicable laws or regulations;

•the impact of natural disasters, including climate change, and the impact of health epidemics on our business;

•the size and growth potential of the markets for our products, and our ability to serve those markets;

•market acceptance of our planned products;

•our ability to raise capital;

•the possibility that we may be adversely affected by other economic, business, and/or competitive factors; and

•other risks and uncertainties set forth in this report in the section entitled “Risk Factors.”

Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based only on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, projections, anticipated events and trends, the economy and other future conditions. Forward-looking statements are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict and many of which are outside of our control. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. We undertake no obligation to publicly update or review any forward-looking statement, whether as a result of new information, future developments or otherwise, except as required by law. There are or will be important factors that could cause actual results to differ materially from those indicated in these statements. These factors include, but are not limited to, those factors set forth in the sections captioned "Business – Overview,” “Risk Factors,” “Legal Proceedings,” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” in this Quarterly Report on Form 10-Q, in our Annual Report on Form 10-K for the year ended December 31, 2023 as filed with the Securities and Exchange Commission ("SEC") on March 28, 2024 ("2023 Annual Report") and in our other public filings with the SEC, all of which you should review carefully. We undertake no obligation to publicly update or review any forward-looking statement, whether as a result of new information, future developments or otherwise, except as required by law.

PART I FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

SELLAS LIFE SCIENCES GROUP, INC.

CONSOLIDATED BALANCE SHEETS

(Amounts in thousands, except share and per share data)

(Unaudited)


	March 31, 2024		December 31, 2023

ASSETS
Current assets:
Cash and cash equivalents	$	18,415	$	2,530
Restricted cash and cash equivalents	100		100
Prepaid expenses and other current assets	2,986		542
Total current assets	21,501		3,172
Operating lease right-of-use assets	747		858
Goodwill	1,914		1,914
Deposits and other assets	272		275
Total assets	$	24,434	$	6,219
LIABILITIES AND STOCKHOLDERS' EQUITY (DEFICIT)
Current liabilities:
Accounts payable	$	7,407	$	5,639
Accrued expenses and other current liabilities	6,542		7,650
Operating lease liabilities	488		446
Total current liabilities	14,437		13,735
Operating lease liabilities, non-current	313		460
Total liabilities	14,750		14,195
Commitments and contingencies (Note 7)
Stockholders’ (deficit) 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, 2024 and December 31, 2023	—		—
Common stock, $0.0001 par value; 350,000,000 shares authorized, 56,267,670 and 32,132,890 shares issued and outstanding at March 31, 2024 and December 31, 2023, respectively	5		3
Additional paid-in capital	236,489		209,265
Accumulated deficit	(226,810)		(217,244)
Total stockholders’ equity (deficit)	9,684		(7,976)
Total liabilities and stockholders’ equity (deficit)	$	24,434	$	6,219

See accompanying notes to these unaudited consolidated financial statements.

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SELLAS LIFE SCIENCES GROUP, INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

(Amounts in thousands, except share and per share data)

(Unaudited)


	Three Months Ended March 31,
		2024		2023

Operating expenses:

Research and development		$	5,111	$	7,174
General and administrative		4,534		4,107
Total operating expenses		9,645		11,281
Loss from operations		(9,645)		(11,281)
Non-operating income:
Change in fair value of warrant liability		—		2
Interest income		79		182
Total non-operating income		79		184
Net loss		$	(9,566)	$	(11,097)

Per share information:
Net loss per common share, basic and diluted		$	(0.21)	$	(0.47)
Weighted-average common shares outstanding, basic and diluted		44,812,996		23,547,562

See accompanying notes to these unaudited consolidated financial statements.

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SELLAS LIFE SCIENCES GROUP, INC.

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT)

(Amounts in thousands, except share amounts)

(Unaudited)













	Three Months Ended March 31, 2024
	Common Stock			Additional Paid-In Capital		Accumulated Deficit		Total Stockholders' Equity (Deficit)
	Shares	Amount
Balance at December 31, 2023	32,132,890	$	3	$	209,265	$	(217,244)	$	(7,976)
Issuance of common stock and common stock warrants, net of issuance costs	21,130,000	2		26,648		—		26,650
Issuance of common stock upon the exercise of pre-funded warrants	2,884,658	—		—		—		—
Issuance of common stock upon the exercise of warrants	65,750	—		49		—		49
Issuance of common stock under employee stock purchase plan	54,372	—		51		—		51
Stock-based compensation	—	—		476		—		476
Net loss	—	—		—		(9,566)		(9,566)
Balance at March 31, 2024	56,267,670	$	5	$	236,489	$	(226,810)	$	9,684














	Three Months Ended March 31, 2023
	Common Stock			Additional Paid-In Capital		Accumulated Deficit		Total Stockholders' Equity
	Shares	Amount
Balance at December 31, 2022	21,005,405	$	2	$	184,753	$	(179,904)	$	4,851
Issuance of common stock and common stock warrants, net of issuance costs	7,220,217	1		18,553		—		18,554
Issuance of common stock, net of issuance costs	76,882			268				268
Issuance of common stock under employee stock purchase plan	45,416	—		53		—		53
Stock-based compensation	—	—		540		—		540
Net loss	—	—		—		(11,097)		(11,097)
Balance at March 31, 2023	28,347,920	$	3	$	204,167	$	(191,001)	$	13,169

See accompanying notes to these unaudited consolidated financial statements.

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SELLAS LIFE SCIENCES GROUP, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(Amounts in thousands)

(Unaudited)


	Three Months Ended March 31,
	2024		2023
Cash flows from operating activities:
Net loss	$	(9,566)	$	(11,097)
Adjustment to reconcile net loss to net cash used in operating activities:
Non-cash stock-based compensation	476		540
Non-cash lease expense	138		87
Change in fair value of common stock warrants	—		(2)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,441)		(1,474)
Accounts payable	1,806		(284)
Accrued expenses and other current liabilities	(1,042)		196
Operating lease liabilities	(132)		(93)
Net cash used in operating activities	(10,761)		(12,127)



Cash flows from financing activities:
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	26,546		18,583
Proceeds from issuance of common stock, net of issuance costs	—		268
Proceeds from the exercise of common stock warrants	49		—
Proceeds from employee stock purchases	51		53
Net cash provided by financing activities	26,646		18,904
Net increase in cash, cash equivalents, restricted cash, and restricted cash equivalents	15,885		6,777
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the beginning of period	2,630		17,225
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the end of period	$	18,515	$	24,002

Supplemental disclosure of cash flow information:
Cash received during the period for interest	$	79	$	182
Supplemental disclosure of non-cash investing and financing activities:
Non-cash acquisition of in-process research and development	$	—	$	5,500

Offering expenses included in accounts payable and accrued expenses and other current liabilities	$	104	$	29
Warrant modifications recorded in stockholders' equity (deficit)	$	725	$	252

See accompanying notes to these unaudited consolidated financial statements.

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SELLAS LIFE SCIENCES GROUP, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

1. Description of Business

Overview

SELLAS Life Sciences Group, Inc. is a late-stage clinical biopharmaceutical company focused on novel therapeutics 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 an array of tumor types. 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 is SLS009 (formerly GFH009), a small molecule, highly selective cyclin-dependent kinase 9 ("CDK9") inhibitor, which the Company licensed from GenFleet Therapeutics (Shanghai), Inc. ("GenFleet"), for all therapeutic and diagnostic uses in the world outside of mainland China, Hong Kong, Macau and Taiwan ("SLS009 Territory").

2. Liquidity

Since inception, the Company has incurred recurring losses and negative cash flows from operations and, as of March 31, 2024, has an accumulated deficit of $226.8 million. During the three months ended March 31, 2024, the Company incurred a net loss of $9.6 million, and used $10.8 million of cash in operations. The Company expects to continue to generate operating losses and negative cash flows from operations 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 March 19, 2024, the Company consummated the March 2024 Registered Direct Offering priced at-the-market under Nasdaq rules, in which it entered into a Securities Purchase Agreement with two institutional investors pursuant to which the Company agreed to issue and sell 11,000,000 shares of its common stock and 2,029,316 pre-funded warrants exercisable for shares of common stock. Each share of common stock was sold at a purchase price of $1.535 and each pre-funded warrant was sold at a purchase price of $1.5349. The net proceeds to the Company from the March 2024 Registered Direct Offering were approximately $18.5 million, after deducting the placement agent's fees and related offering expenses. In a concurrent private placement, the Company agreed to issue to the two institutional investors exercisable for up to an aggregate of 13,029,316 shares of common stock warrants at an exercise price of $1.41 per share. Subsequent to the closing of the March 2024 Registered Direct Offering, all of the pre-funded warrants have been exercised for shares of common stock.

On January 8, 2024, the Company consummated the January 2024 Offering on a "reasonable best efforts" basis, issuing 10,130,000 shares of common stock and an aggregate of 1,870,000 pre-funded warrants exercisable for shares of common stock, together with accompanying warrants to purchase an aggregate of 12,000,000 shares of common stock. Each share of common stock and accompanying common warrant were sold together at a combined offering price of $0.75, and each pre-funded warrant and accompanying common warrant were sold together at a combined offering price of $0.7499. The net proceeds to the Company from the January 2024 Offering were approximately $8.2 million, after deducting placement agents' fees and related offering expenses. Subsequent to the closing of the January 2024 Offering, all of the pre-funded warrants have been exercised for shares of common stock.

In December 2020, the Company, together with its wholly-owned subsidiary, SLSG Limited, LLC, entered into an Exclusive License Agreement (the “3D Medicines Agreement”) with 3D Medicines Inc. ("3D Medicines"), pursuant to which the Company granted 3D Medicines 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 product candidates for all therapeutic and other diagnostic uses in mainland China, Hong Kong, Macau and Taiwan ("3DMed Territory"). As of March 31, 2024, the Company has received an aggregate of $10.5 million in upfront payments and certain technology transfer and regulatory milestones. There is a total of $191.5 million in potential future development, regulatory, and sales milestones, not including future royalties, that remains under the 3D Medicines Agreement, which milestones are all variable in nature and not under the Company's control.

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SELLAS LIFE SCIENCES GROUP, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - Continued

(Unaudited)

As of March 31, 2024, the Company had cash and cash equivalents of approximately $18.4 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 will not be sufficient to fund its current planned operations for at least the next twelve months from the date of issuance of these consolidated financial statements.

The Company will require substantial additional financing to commercially develop any current or future product candidates. If the Company is unable to obtain additional funding on a timely basis, it will be required to scale back its plans and place certain activities on hold. The Company currently does not have any commitments to obtain additional funds. The Company's management continues to evaluate different strategies to obtain the required funding for future operations. These strategies may include public and private placements of equity and/or debt securities, as well as payments from potential strategic research and development collaborations or licensing and/or marketing arrangements with pharmaceutical companies. Additionally, the Company continues to pursue discussions with global and regional pharmaceutical companies for licensing and/or co-development rights to the Company's product candidates. There can be no assurance that these future funding efforts will be successful.

3. 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 2023 Annual Report. The significant accounting policies summarized and included in the 2023 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 ASC and Accounting Standards Updates ("ASUs") 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, SELLAS Life Sciences Group, Ltd., a privately held Bermuda exempted company, 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 2023 Annual Report. The accompanying consolidated financial statements as of March 31, 2024 and for the three months ended March 31, 2024 and 2023, 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, 2023 have been derived from the audited financial statements as of that date.

Net Loss Per Share

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SELLAS LIFE SCIENCES GROUP, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - Continued

(Unaudited)

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,
	2024	2023
Common stock warrants	41,802	12,361
Stock options	2,155	1,661
Restricted stock units ("RSUs")	738	444
	44,695	14,466

Recent Accounting Standards Adopted

In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities to disclose significant segment expenses regularly provided to the chief operating decision-maker. Public entities with a single reporting segment have to provide all disclosures required by ASC 280, including the significant segment expense disclosures. ASU No. 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods in fiscal years beginning after December 15, 2024. This ASU became effective for the Company on January 1, 2024 and did not have a material impact on the consolidated financial statements.

Recent Accounting Standards Not Yet Adopted

In December 2023, the FASB issued ASU No. 2023-09, Improvements to Income Tax Disclosures, which amends the guidance in ASC 740, Income Taxes. The ASU is intended to improve the transparency of income tax disclosures by prescribing standard categories and greater disaggregation of information in the effective tax rate reconciliation, disclosure of income taxes paid disaggregated by jurisdiction, and modifies other income tax-related disclosures. ASU No. 2023-09 is effective for fiscal years beginning after December 15, 2024 and allows for adoption either prospectively or retrospectively. Early adoption is permitted. The Company is currently evaluating the impact of the ASU on the income tax disclosures within the consolidated financial statements but does not expect a material impact upon adoption.

4. Fair Value Measurements

The following tables present information about the Company's assets measured at fair value on a recurring basis in the consolidated balance sheets (in thousands):


Description	March 31, 2024		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	18,247	$	18,247	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	18,347	$	18,347	$	—	$	—

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SELLAS LIFE SCIENCES GROUP, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - Continued

(Unaudited)


Description	December 31, 2023		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,314	$	2,314	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	2,414	$	2,414	$	—	$	—

The Company did not transfer any financial instruments into or out of Level 3 classification during the three months ended March 31, 2024 or during the year ended December 31, 2023.

5. Acquired In-Process Research and Development

Exclusive License Agreement with GenFleet Therapeutics (Shanghai) Inc.

On March 31, 2022, the Company entered into an exclusive license agreement with GenFleet pursuant to which GenFleet granted to the Company a sublicensable royalty-bearing license under certain of its intellectual property, to develop, manufacture, and commercialize SLS009 for the treatment, diagnosis or prevention of disease in humans and animals in the SLS009 Territory.

In consideration for the exclusive license, the Company agreed to pay to GenFleet (i) an upfront and technology transfer fee of $10.0 million, all of which has been paid, (ii) development and regulatory milestone payments for up to three indications totaling up to $48.0 million in the aggregate upon the achievement of such milestones, and (iii) sales milestone payments totaling up to $92.0 million in the aggregate upon the achievement of certain net sales thresholds in a given calendar year. The Company also agreed to pay GenFleet single-digit tiered royalties based upon a percentage of annual net sales, with the royalty rate escalating based on the level of annual net sales of SLS009 in the SLS009 Territory ranging from the low to high single digits.

6. Balance Sheet Accounts

Prepaid expenses and other current assets consist of the following (in thousands):


	March 31, 2024		December 31, 2023
Insurance	$	1,092	$	87
Clinical trial costs	1,690		399
Professional fees	115		56
Other	89		—
Prepaid expenses and other current assets	$	2,986	$	542

Accrued expenses and other current liabilities consist of the following (in thousands):


	March 31, 2024		December 31, 2023
Clinical trial costs	$	4,186	$	5,672
Compensation and related benefits	1,590		1,493
Professional fees	714		443
Other	52		42
Accrued expenses and other current liabilities	$	6,542	$	7,650

7. Commitments and Contingencies

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SELLAS LIFE SCIENCES GROUP, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - Continued

(Unaudited)

Leases

The Company has 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, was amended in February 2022 to add additional space, and has a term through September 2025. The Company assessed the lease amendment for the additional space and determined it should be accounted for as a separate contract.

The weighted average discount rate of the Company's operating leases under FASB Topic ASC 842, Leases ("ASC 842") is approximately 13%. As of March 31, 2024, the leases have a remaining term of 1.50 years.

Rent expense related to the Company's operating leases was approximately $0.1 million for each of the three months ended March 31, 2024 and 2023.

The Company made cash payments related to its operating leases of approximately $0.1 million for each of the three months ended March 31, 2024 and 2023.

Future minimum lease payments are as follows as of March 31, 2024 (in thousands):


Future minimum lease payments:
2024 (remaining)	$	401
2025	477
Total future minimum lease payments	878
Less: imputed interest	(77)
Current and non-current operating lease liabilities	$	801

Legal Proceedings

From time to time, the Company may be 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.

On December 20, 2023, the Company commenced a binding arbitration proceeding against 3D Medicines, administered by the Hong Kong International Arbitration Centre and governed by New York State law in accordance with the dispute resolution provisions in the 3D Medicines Agreement. The arbitration proceeding involves, among other things, the trigger and payment of the relevant milestone payments due to the Company as well as 3D Medicines’ failure to use commercially reasonable best efforts to develop GPS in the 3DMed Territory, and particularly in mainland China. See Part II, Item 1. Legal Proceedings. Except for this arbitration proceeding, as of March 31, 2024, there was no pending or threatened litigation.

8. Stockholders’ Equity (Deficit)

Preferred Stock

The Company has authorized up to 5,000,000 shares of preferred stock, $0.0001 par value per share, for issuance. There were no preferred shares outstanding as of March 31, 2024 and December 31, 2023.

Common Stock

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(Unaudited)

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, 2024, the Company has shares of common stock reserved for future issuance as follows (in thousands):


Warrants outstanding			41,802
Stock options outstanding			2,155
RSUs outstanding			738
Shares reserved for future issuance under the 2023 Amended and Restated Equity Incentive Plan			3,003
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan			129
Total common stock reserved for future issuance			47,827

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(Unaudited)

9. 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, 2024 (in thousands except per share data):


Warrant Issuance	Outstanding, December 31, 2023	Granted	Exercised	Expired	Outstanding, March 31, 2024	Exercise Price per Share		Expiration
Warrants classified as equity:
March 2024 Registered Direct Offering	—	13,029	—	—	13,029	$	1.41	September 2029
March 2024 Registered Direct Offering Pre-Funded Warrants	—	2,029	(1,015)	—	1,014	$	—	n/a
January 2024 Offering	—	12,000	(60)	—	11,940	$	0.75	January 2029
January 2024 Offering Pre-Funded Warrants	—	1,870	(1,870)	—	—	$	—	n/a
November 2023 Registered Direct Offering	3,652	—	—	—	3,652	$	0.75	January 2029

February 2023 Offering	7,206	—	(5)	—	7,201	$	0.75	February 2028
April 2022 Offering	766	—	—	—	766	$	5.40	April 2027
April 2022 Offering - Modified Warrants	3,864	—	—	—	3,864	$	0.75	January 2029
January 2020 Offering	309	—	—	—	309	$	3.93	July 2025
July 2020 PIPE Offering	25	—	—	—	25	$	3.30	August 2025
Other	32	—	—	(30)	2	$	7.50	June 2024
	15,854	28,928	(2,950)	(30)	41,802

Subsequent to March 31, 2024, the remaining 1,014,658 pre-funded warrants issued in the March 2024 Registered Direct Offering were exercised into shares of common stock.

Warrants Classified as Equity

The warrants to acquire shares of common stock issued during the February 2023 Offering were recorded as equity upon issuance. During its evaluation of equity classification of these warrants, 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 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.

In connection with the closing of the January 2024 Offering at a combined offering price of $0.75, the Company agreed to (i) reduce the exercise price of an aggregate of 3,863,851 warrants that were issued to certain purchasers in an underwritten public offering that closed on April 5, 2022 (the "April 2022 Offering") to $0.75, (ii) reduce the exercise price of an aggregate of 3,652,300 warrants that were issued in the November 2023 Registered Direct Offering to $0.75, and (iii) extend the termination date of the April 2022 Offering warrants and the November 2023 Registered Direct Offering warrants to January 8, 2029. Concurrent with the closing of the January 2024 Offering, the exercise price of an aggregate of 7,220,217 warrants issued in the February 2023 Offering were also reduced to an exercise price of $0.75 per share. The Company accounted for these amendments as a cost to issue equity with the incremental fair value of approximately $0.7 million recognized as an offset to the proceeds received.

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(Unaudited)

However, there was no net impact to the consolidated statements of stockholders' equity (deficit) because the warrants are equity classified.

10. Licensing Revenue

Exclusive License Agreement with 3D Medicines Inc.

In December 2020, the Company entered into the 3D Medicines Agreement pursuant to which the Company granted 3D Medicines 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 (referred to as GPS Plus) product candidates ("GPS Licensed Products") for all therapeutic and other diagnostic uses in the 3DMed Territory. In partial consideration for the rights granted by the Company, 3D Medicines 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. 3D Medicines 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.

Revenue Recognition

At inception, the Company evaluated the 3D Medicines Agreement under ASC 606 and recognized an initial transaction price of $9.5 million, which included the $7.5 million upfront fee as well as $2.0 million in development milestones that were assessed to be probable of being achieved, while the remaining milestones were variable consideration subject to constraint at inception. In the first quarter of 2022, an additional $1.0 million in licensing revenue was recognized upon approval by China’s National Medical Products Administration (“NMPA”) for a small Phase 1 clinical trial investigating safety of GPS in China.

There is $191.5 million in potential future development, regulatory, and sales milestones, not including future royalties, remaining under the 3D Medicines Agreement as of March 31, 2024, which milestones are variable in nature and not under the Company's control. At the end of each reporting period, the Company reevaluates 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.

There was no licensing revenue recognized during each of the three months ended March 31, 2024 and 2023. There was no cost of licensing revenue recognized during each of the three months ended March 31, 2024 and 2023.

11. 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 currently allows for issuance of up to approximately 22,000 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.

2023 Amended and Restated Equity Incentive Plan

On September 10, 2019, the 2019 Equity Incentive Plan ("2019 Equity Plan") was approved by the stockholders of the Company. On June 20, 2023, an amendment to the 2019 Equity Plan was approved by the

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(Unaudited)

stockholders of the Company, which amended and restated the 2019 Equity Plan (as amended and restated, the "2023 Amended and Restated Equity Incentive Plan") to increase the number of shares of common stock authorized for issuance under the 2019 Equity Plan by 3,000,000 shares.

The 2023 Amended and Restated Equity Incentive Plan currently allows for issuance of up to approximately 6,036,000 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.

As of March 31, 2024, approximately 3,003,000 shares of common stock were reserved for future grants under the 2023 Amended and Restated Equity Incentive Plan.

The following table summarizes the components of stock-based compensation expense in the consolidated statements of operations for the three months ended March 31, 2024 and 2023, respectively (in thousands):


	Three Months Ended March 31,
		2024		2023
Research and development		$	85	$	96
General and administrative		391		444
Total stock-based compensation		$	476	$	540

Options to Purchase Shares of Common Stock

The following table summarizes stock option activity of the Company for the three months ended March 31, 2024:


	Total Number of Shares (In Thousands)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value (In Thousands)
Outstanding at December 31, 2023	1,607	$	5.92		$	—
Granted	671	0.53

Canceled	(123)	3.44
Outstanding at March 31, 2024	2,155	$	4.38	8.44	$	308
Options exercisable at March 31, 2024	883	$	7.38	7.43	$	—

The aggregate intrinsic values of outstanding and exercisable stock options at March 31, 2024 were calculated based on the closing price of the Company’s common stock as reported on the Nasdaq Capital Market on March 28, 2024 of $1.01 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 Company uses the Black-Scholes option-pricing model to determine the fair value of all its stock options granted. The weighted average assumptions used during the three months ended March 31, 2024 and 2023, respectively, were as follows:

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(Unaudited)


	Three Months Ended March 31,
	2024		2023
Risk free interest rate	4.01	%	3.79	%
Volatility	130.41	%	127.68	%
Expected lives (years)	6.19		6.20
Expected dividend yield	—	%	—	%

The weighted-average grant date fair value of options granted during the three months ended March 31, 2024 and 2023 was $0.48 and $2.95, 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, 2024, 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 2.3 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, 2024:


	Shares (In Thousands)	Weighted Average Grant Date Fair Value
Unvested at December 31, 2023	338	$	2.99
Granted	429	$	0.52
Canceled	(29)	$	1.39
Unvested at March 31, 2024	738	$	1.62

As of March 31, 2024, there was $1.1 million of unrecognized compensation cost related to outstanding RSUs that is expected to be recognized as a component of the Company's operating expenses over a weighted-average period of 2.1 years. No RSUs vested during the three months ended March 31, 2024.

2021 Employee Stock Purchase Plan

On April 22, 2021, the Board of Directors adopted the 2021 Employee Stock Purchase Plan ("2021 ESPP") which was approved by the Company's stockholders on June 8, 2021 and authorized the issuance of up to 300,000 shares of common stock pursuant to the 2021 ESPP. The 2021 ESPP allows employees to contribute up to 20% of their cash earnings, subject to a maximum of $25,000 per year under Internal Revenue Service rules, to be used to purchase shares of the Company’s common stock on semi-annual purchase dates. The 2021 ESPP allows eligible employees to purchase shares of common stock at a price per share equal to 85% of the lower of the fair market value of the common stock at the beginning or end of each six-month offering period during the term of the 2021 ESPP.

During the three months ended March 31, 2024, 54,372 shares of common stock were purchased by employees under the 2021 ESPP for proceeds of approximately $0.1 million. There are currently 129,085 shares of common stock reserved for issuance under the 2021 ESPP as of March 31, 2024.

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12. Subsequent Events

The Company evaluated all events or transactions that occurred after March 31, 2024 up through the date these consolidated 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.

ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

This management’s discussion and analysis of financial condition as of March 31, 2024 and results of operations for the three months ended March 31, 2024 and 2023, respectively, should be read in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations included in our Annual Report on Form 10-K for the year ended December 31, 2023, as filed with the Securities and Exchange Commission, or SEC, on March 28, 2024, or our 2023 Annual Report, and our other public reports filed with the SEC.

Overview

We are a late-stage clinical biopharmaceutical company focused on the development of novel therapeutics for a broad range of cancer indications. Our product candidates currently include galinpepimut-S, or GPS, a peptide immunotherapy directed against the Wilms tumor 1, or WT1, antigen, and SLS009 (formerly GFH009), a highly selective small molecule cyclin-dependent kinase 9, or CDK9, inhibitor.

Galinpepimut-S, or GPS: Highly Novel and Engineered Immunotherapy Targeting the WT1 Antigen

Our lead product candidate, GPS, is a cancer immunotherapeutic agent licensed from Memorial Sloan Kettering Cancer Center, or MSK, that targets the 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.

In January 2020, we commenced in the United States an open label randomized Phase 3 clinical trial, the REGAL study, for GPS monotherapy in patients with acute myeloid leukemia, or AML, in the maintenance setting after achievement of second complete remission, or CR2, following successful completion of second-line antileukemic therapy. Patients are randomized to receive either GPS or best available treatment, or BAT. We expect this study will be used as the basis for submission of a Biologics License Application, or BLA, subject to a statistically significant and clinically meaningful data outcome and agreement with the U.S. Food and Drug Administration, or the FDA. The primary endpoint of the REGAL study is overall survival. We planned to enroll approximately 125 to 140 patients at approximately 95 clinical sites in North America, Europe and Asia with a planned interim safety, efficacy and futility analysis after 60 events (deaths). In March 2024, we announced the completion of enrollment. Under our current assumptions with respect to enrollment and the estimated survival times for both the treated and control groups in the study, we believe, after discussions with our external statisticians and experts, that the planned interim analysis after 60 events (deaths) per the protocol may occur in the second quarter of 2024 and the final analysis after 80 events may occur by the end of 2024. Because these analyses are event driven, they are difficult to predict with any certainty and may occur at a different time than currently expected.

In December 2020, we entered into an exclusive license agreement, or 3D Medicines Agreement, with 3D Medicines Inc., or 3D Medicines, a China-based biopharmaceutical company developing next-generation immuno-oncology drugs, for the development and commercialization of GPS, as well as the Company’s next generation heptavalent immunotherapeutic GPS+, which is at preclinical stage, across all therapeutic and diagnostic uses in mainland China, Hong Kong, Macau and Taiwan, which we collectively refer to as Greater China, or the 3DMed Territory. We have retained sole rights to GPS and GPS+ outside of Greater China. In November 2022, we announced that we had agreed with 3D Medicines for 3D Medicines to participate in the REGAL study through the inclusion of approximately 20 patients from mainland China. In December 2022, we entered into a Side Letter Agreement with 3D Medicines, or Side Letter, which, together with the 3D Medicines Agreement, details the terms and conditions of 3D Medicines' participation in the REGAL study. Although the REGAL study has completed enrollment as announced in March 2024, in accordance with the predetermined statistical analysis plan, 3D Medicines may still enroll patients in mainland China. The timing of such participation and patient enrollment by 3D Medicines, if at all, cannot be predicted with certainty. As of March 31, 2024, we have received an aggregate of $10.5 million in upfront and milestone payments under the 3D Medicines Agreement and a total of $191.5 million in potential future development, regulatory and sales milestones, not including future royalties, remains under the license agreement, which milestones are variable in nature and not under our control. In December 2023, we

commenced an arbitration proceeding against 3D Medicines regarding, among other things, the trigger and payment of $13.0 million in milestone payments due to us. See Part II, Item 1. Legal Proceedings.

In February 2020, a Phase 1 open-label investigator-sponsored clinical trial of GPS, in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, nivolumab (Opdivo®), in patients with malignant pleural mesothelioma, or MPM, who harbor relapsed or refractory disease after having received frontline standard of care multimodality therapy was commenced at MSK. Enrollment of a target total of 10 evaluable patients was completed at the end of 2022. We reported positive topline safety and efficacy data from this study in June 2023 and positive follow-up immune response and survival data in December 2023. We plan to present final data from this study at a medical conference in the second quarter of 2024.

GPS was granted Orphan Drug Product Designations, or ODD, from the FDA, as well as orphan medicines designations from the European Medicines Agency, or EMA, for GPS in AML, MPM, and multiple myeloma, or MM, as well as Fast Track designation for AML, MPM, and MM from the FDA.

SLS009: Highly Selective Next Generation CDK9 Inhibitor

On March 31, 2022, we entered into an exclusive license agreement, or the GenFleet Agreement, with GenFleet Therapeutics (Shanghai), Inc., or GenFleet, a clinical-stage biotechnology company developing cutting-edge therapeutics in oncology and immunology, that grants rights to us for the development and commercialization of SLS009, a highly selective small molecule CDK9 inhibitor, across all therapeutic and diagnostic uses worldwide, except for Greater China.

CDK9 activity has been shown to correlate negatively with overall survival in a number of cancer types, including hematologic cancers, such as AML and lymphomas, as well as solid cancers, such as osteosarcoma, pediatric soft tissue sarcomas, melanoma, endometrial, lung, prostate, breast and ovarian. As demonstrated in preclinical and clinical data, to date, SLS009’s high selectivity has the potential to reduce toxicity as compared to older CDK9 inhibitors and other next-generation CDK9 inhibitors currently in clinical development and to potentially be more efficacious.

We completed a Phase 1 dose-escalating clinical trial in the United States and China for SLS009 in mid-2023 and reported positive safety and efficacy data for both patient cohorts, that is relapsed and/or refractory AML and refractory lymphoma. We also established in the trial a recommended Phase 2 dose, or RP2D, of 60 mg for AML and 100 mg for lymphomas.

In the second quarter of 2023, we commenced an open label, single arm, multi-center Phase 2a clinical trial with SLS009 in combination with venetoclax and azacitidine, or aza/ven, in patients with AML who failed or did not respond to treatment with venetoclax-based therapies. The trial is evaluating safety, tolerability, and efficacy at two dose levels of SLS009, 45 mg once weekly, and 60 mg once weekly or 30 mg twice a week, in combination with aza/ven. In addition to safety and tolerability of SLS009 in combination with aza/ven, the primary endpoints are complete response composite rate and duration of response. Additional endpoints include event free survival, overall survival, and pharmacokinetic and pharmacodynamic assessments.

In the fourth quarter of 2023, we completed enrollment in the 45 mg (safety) dose cohort in the Phase 2a study and reported positive initial topline data. We also commenced enrollment in the 60 mg dose cohort with patients randomized to one of two groups, 60 mg fixed dose once weekly or 30 mg fixed twice weekly. Each group will enroll five to 10 patients.

In March 2024, we announced positive topline data from the Phase 2a clinical trial of SLS009 in combination with aza/ven in r/r/ AML. A total of 21 patients were enrolled in the study as of March 15, 2024: 10 in the 45 mg safety cohort and 11 in the 60 mg cohort (30 mg twice a week or 60 mg once a week). Response rates observed in the three cohorts were 10% in the 45 mg once a week safety dose cohort (dose level below the RP2D), 20% in the 60 mg once a week dose cohort, and 50% in the 30 mg twice a week dose cohort. Additionally, we observed strong anti-leukemic activity, which is defined as 50% or more bone marrow blast reduction in 67% of patients across all dose levels. Median OS has not been reached in any of the cohorts and the first patient enrolled in the study who achieved a CR continues on the study and remains leukemia-free 9 months after enrollment.

During the trial, we identified potential biomarkers currently undergoing testing as predictive markers in the most recent portion of the study. In May 2024, we announced additional preliminary data from the Phase 2a trial of SLS009 in r/r AML and successful filing of a provisional patent application around the ASXL1 mutation and SLS009, including all CDK9 inhibitor drugs. ASXL1 mutations are associated with poor prognosis in all myeloid diseases, owing to the reduced response to the current treatment options. We observed a high rate of responses in patients with myelodysplasia-related molecular mutations, as defined by the World Health Organization and patients with the ASXL1 gene mutation accounted for the most responders across all dose cohorts. As of April 19, 2024, a 100% response rate had been achieved in r/r AML patients with ASXL1 truncating mutations at the optimal dose level (30 mg twice a week), and a 57% response rate in r/r AML patients with ASXL1 truncating mutations across all dose levels. Furthermore, we have clarified the proposed biological basis and mechanism of action for SLS009 activity in patients with these biomarkers. The relevant biomarkers are present in multiple hematologic and solid cancer indications, with a substantial proportion of patients exhibiting them in additional indications, ranging up to ~50% of patients in some indications. We also announced that we have expanded the ongoing study to include two additional cohorts, one with ASXL1 mutated AML patients and one with patients with myelodysplasia-related molecular abnormalities other than ASXL1. Additional topline data updates are expected in the second and third quarters of 2024.

Our partner, GenFleet, is focusing on lymphoma indications with SLS009 in its Greater China market. In October 2023, we announced that GenFleet dosed the first patient in a Phase Ib/II trial evaluating SLS009 in patients with relapsed/refractory, or r/r, peripheral T-cell lymphoma, or PTCL. In March 2024, GenFleet announced that it entered into a collaboration and supply agreement with BeiGene Switzerland GmbH to initiate a study of SLS009 in combination with Zanubrutinib (Brukinsa®), a BTK inhibitor, in r/r diffuse large B-cell lymphoma, or DLBCL, and the first patient was dosed in the trial. Both studies are funded and sponsored by GenFleet and are being conducted in China. We expect to report initial topline outcomes data in the second and/or third quarter of 2024.

SLS009 is also currently being evaluated in pediatric solid tumors and leukemia models through the NCI Pediatric Preclinical in Vivo Testing, or PIVOT, program. Studies are supported through cooperative agreement grants from the NCI to the PIVOT research centers performing the testing in pediatric tumor models and a centralized coordinating center. We expect to report relevant data from the program in the second half of 2024.

For SLS009, the FDA granted Orphan Drug Product designations in AML and PTCL and Fast Track designations for r/r AML and r/r PTCL.

Components of Results of Operations

Research and Development

Research and development expense consists of expenses incurred in connection with the discovery and development of our product candidates. We expense research and development costs as incurred. These expenses include:

•expenses incurred under agreements with CROs, as well as investigative sites and consultants that conduct our preclinical studies and clinical trials;

•manufacturing and clinical drug supply expenses;

•outsourced professional scientific development services;

•employee-related expenses, which include salaries, benefits and stock-based compensation;

•payments made under our license agreements, under which we acquired certain intellectual property;

•expenses relating to certain regulatory activities, including filing fees paid to regulatory agencies;

•laboratory materials and supplies used to support our research activities; and

•allocated expenses, utilities, and other facility-related costs.

The successful development of our current and future product candidates is highly uncertain. At this time, we cannot reasonably estimate or know the nature, timing and costs of the efforts that will be necessary to complete the remainder of the development of, or when, if ever, material net cash inflows may commence from, any current or future product candidates. This uncertainty is due to the numerous risks and uncertainties associated with the duration and cost of our clinical trials, which vary significantly over the life of a project as a result of many factors, including:

•the number and geographical location of clinical sites included in the trials;

•the length of time required to enroll suitable patients;

•the number and geographical location of patients that ultimately participate in the trials;

•the number of doses patients receive;

•the duration of patient follow-up;

•the results of clinical trials;

•the expenses associated with manufacturing and clinical drug supply;

•the receipt of marketing approvals; and

•the commercialization of current and future product candidates.

Research and development activities are central to our business model. Oncology product candidates in the later stages of clinical development generally have higher development costs than those in the earlier stages of clinical development, primarily due to the increased size and duration of the later-stage clinical trials. We expect our research and development expenses to increase for the foreseeable future as we conduct and complete our ongoing early and late-stage clinical trials and initiate additional clinical trials.

Our expenditures are subject to additional uncertainties, including the terms and timing of regulatory approvals. We may never succeed in achieving regulatory approval for any of our current or future product candidates. We may obtain unexpected results from our clinical trials. We may elect to discontinue, delay or modify clinical trials of some product candidates or target indications or focus on others. A change in the outcome of any of these variables with respect to the development of a product candidate could mean a significant change in the costs and timing associated with the development of that product candidate. For example, if the FDA or other regulatory authorities were to require us to conduct clinical trials beyond those that we currently anticipate, or if we experience significant delays in enrollment in any of our clinical trials, we could be required to expend significant additional financial resources and time on the completion of clinical development.

General and Administrative

General and administrative expenses consist principally of salaries and related costs for personnel in executive, administrative, finance and legal functions, including stock-based compensation, travel expenses and recruiting expenses, fees for outside legal counsel, amortization of contract acquisition costs (commissions), and director and officer insurance premiums. Other general and administrative expenses include facility related costs, patent filing and prosecution costs, professional fees for business development, accounting, consulting, legal and tax-related services associated with maintaining compliance with our Nasdaq listing and SEC reporting requirements, investor relations costs, and other expenses associated with being a public company.

If and when we believe that regulatory approval of a product candidate appears likely, we anticipate that an increase in general and administrative expenses will occur as a result of our preparation for commercial operations, particularly as it relates to the sales and marketing of such product candidate. Oncology product commercialization may take several years and millions of dollars in development costs.

Non-Operating Income

Non-operating income consists of changes in fair value of our warrant liability, and interest income. Interest income primarily reflects interest earned from our cash and cash equivalents.

Critical Accounting Policies and Estimates

In the 2023 Annual Report, we disclosed our critical accounting policies and estimates upon which our consolidated financial statements are derived. There have been no material changes to these policies and estimates since December 31, 2023 that are not included in Note 3 of the accompanying consolidated financial statements for the three months ended March 31, 2024. Readers are encouraged to read the 2023 Annual Report in conjunction with this Quarterly Report on Form 10-Q.

Results of Operations for the Three Months Ended March 31, 2024 and 2023

The following table summarizes our results of operations for the three months ended March 31, 2024 and 2023 (in thousands):


	Three Months Ended March 31,
	2024		2023		Change

Operating expenses:

Research and development	5,111		7,174		(2,063)
General and administrative	4,534		4,107		427
Total operating expenses	9,645		11,281		(1,636)
Loss from operations	(9,645)		(11,281)		1,636
Non-operating income	79		184		(105)
Net loss	$	(9,566)	$	(11,097)	$	1,531

Further analysis of the changes and trends in our operating results are discussed below.

Research and Development

Research and development expenses were $5.1 million for the three months ended March 31, 2024 compared to $7.2 million for the three months ended March 31, 2023. The $2.1 million decrease was primarily attributable to a $1.0 million decrease due to the timing of a clinical drug supply purchase in the prior period, a $0.8 million decrease in clinical and regulatory consultants, a $0.2 million decrease in personnel related expenses due to changes in headcount, and a $0.1 million decrease in licensing fees. We anticipate that our research and development expenses will increase in the future as we continue to advance the development of GPS and SLS009.

General and Administrative

General and administrative expenses were $4.5 million for the three months ended March 31, 2024 compared to $4.1 million for the three months ended March 31, 2023. The $0.4 million increase was primarily attributable to the initial recognition of a $1.1 million one-time severance charge during the three months ended March 31, 2024, partially offset by a $0.5 million decrease in outside services and public company costs and a $0.2 million decrease in other personnel related expenses.

Non-Operating Income

Non-operating income for the three months ended March 31, 2024 and 2023 was as follows (in thousands):


	Three Months Ended March 31,
		2024		2023		Change
Change in fair value of warrant liability		$	—	$	2	$	(2)
Interest income		79		182		(103)
Total non-operating income		$	79	$	184	$	(105)

Non-operating income of $0.1 million and $0.2 million during the three months ended March 31, 2024 and 2023, respectively, was related to interest income earned from our cash and cash equivalents.

Liquidity and Capital Resources

We did not generate any revenue from product sales during the three months ended March 31, 2024 and 2023. Through March 31, 2024, we have only generated licensing revenue from the 3DMed License Agreement. Since inception, we have incurred net losses, used net cash in our operations, and have funded substantially all of our operations through proceeds of the sale of equity securities and convertible notes.

Sources of Liquidity

On March 19, 2024, we entered into a Securities Purchase Agreement with two institutional investors pursuant to which we agreed to issue and sell in a registered direct offering priced at-the-market under Nasdaq rules, or the March 2024 Registered Direct Offering, 11,000,000 shares of our common stock and 2,029,316 pre-funded warrants exercisable for shares of common stock. Each share of common stock was sold at a purchase price of $1.535 and each pre-funded warrant was sold at a purchase price of $1.5349. The net proceeds to the Company from the March 2024 Registered Direct Offering were approximately $18.5 million, after deducting the placement agents' fees and related offering expenses. In a concurrent private placement, we agreed to issue to the two institutional investors exercisable for up to an aggregate of 13,029,316 shares of common stock warrants at an exercise price of $1.41 per share. Subsequent to the closing of the March 2024 Registered Direct Offering, all of the pre-funded warrants have been exercised for shares of common stock.

On January 8, 2024, we consummated a public offering on a "reasonable best efforts" basis, or the January 2024 Offering, pursuant to which we issued 10,130,000 shares of common stock and an aggregate of 1,870,000 pre-funded warrants exercisable for shares of common stock, together with accompanying warrants to purchase an aggregate of 12,000,000 shares of common stock. Each share of common stock and accompanying common warrant were sold together at a combined offering price of $0.75, and each pre-funded warrant and accompanying common warrant were sold together at a combined offering price of $0.7499. The net proceeds to us from the January 2024 Offering were approximately $8.2 million, after deducting the placement agents' fees and related offering expenses. Subsequent to the closing of the January 2024 Offering, all of the pre-funded warrants have been exercised for shares of common stock.

In December 2020, together with our wholly-owned subsidiary, SLSG Limited, LLC, we entered into the 3D Medicines Agreement pursuant to which we granted 3D Medicines a sublicensable royalty-bearing license under certain intellectual property owned or controlled by us, to develop, manufacture and have manufactured, and commercialize GPS and heptavalent GPS product candidates for all therapeutic and other diagnostic uses in the 3DMed Territory. To date, we have received $10.5 million in upfront payments and certain technology transfer and regulatory milestones. A total of $191.5 million in potential future development, regulatory, and sales milestones, not including future royalties, remains under the 3D Medicines Agreement as of March 31, 2024, which milestones are all variable in nature and not under our control.

Funding Requirements

As of March 31, 2024, we had an accumulated deficit of $226.8 million, cash and cash equivalents of $18.4 million and restricted cash and cash equivalents of $0.1 million. In addition, we had current liabilities of $14.4 million as of March 31, 2024. We expect that our cash and cash equivalents will not be sufficient to fund our current planned operations for at least the next twelve months from the date of issuance of these financial statements. These conditions give rise to a substantial doubt over our ability to continue as a going concern. This going concern assumption is based on management’s assessment of the sufficiency of our current and future sources of liquidity and whether it is probable we will be able to meet our obligations as they become due for at least one year from the date our consolidated financial statements are available to be issued, and if not, whether our liquidation is imminent.

Our consolidated financial statements do not include any adjustments related to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. We anticipate incurring additional losses until such time, if ever, that we can generate significant sales of any current or future product candidates in development.

We will require substantial additional financing to develop any current or future product candidates. If we are unable to obtain additional funding on a timely basis, we will be required to scale back our plans and place certain activities on hold. We currently do not have any commitments to obtain additional funds. Our management continues to evaluate different strategies to obtain the required funding for future operations. These strategies may include public and private placements of equity and/or debt securities, as well as payments from potential strategic research and development collaborations or licensing and/or marketing arrangements with pharmaceutical companies. Additionally, we continue to pursue discussions with global and regional pharmaceutical companies for licensing and/or co-development rights to our product candidates. There can be no assurance that these future funding efforts will be successful.

Our future operations are highly dependent on a combination of factors, including (i) the timely and successful completion of any additional financings, (ii) our ability to complete revenue-generating partnerships with pharmaceutical and biotechnology companies, (iii) the success of our research and development activities, (iv) the development of competitive therapies by other biotechnology and pharmaceutical companies, and, ultimately, (v) regulatory approval and market acceptance of our product candidates.

Cash Flows

The following table summarizes our cash flows from operating, investing, and financing activities for the three months ended March 31, 2024 and 2023 (in thousands):


	Three Months Ended March 31,
	2024		2023
Net cash (used in) provided by:
Operating activities	$	(10,761)	$	(12,127)
Financing activities	26,646		18,904
Net increase in cash, cash equivalents, restricted cash, and restricted cash equivalents	$	15,885	$	6,777

Net Cash Used in Operating Activities

Net cash used in operating activities of $10.8 million during the three months ended March 31, 2024 was primarily attributable to our net loss of $9.6 million and a net change in our operating assets and liabilities of approximately $1.8 million, which were partially offset by net non-cash charges of approximately $0.6 million. The net change in our operating assets and liabilities is primarily attributable to an increase in prepaid expenses and other assets of approximately $2.4 million, a decrease in accrued expenses and other current liabilities of approximately $1.1 million, and a decrease in operating lease liabilities of approximately $0.1 million, which were partially offset by an increase in accounts payable of $1.8 million. Net non-cash charges were driven by $0.5 million in non-cash stock-based compensation expense and $0.1 million in non-cash lease expense.

Net cash used in operating activities of $12.1 million during the three months ended March 31, 2023 was primarily attributable to our net loss of $11.1 million and the net change in our operating assets and liabilities of approximately $1.6 million, which were partially offset by various net non-cash charges of $0.6 million. The net change in our operating assets and liabilities of $1.6 million is primarily attributable to an increase in prepaid expenses and other current assets of approximately $1.5 million, and a decrease in operating lease liabilities of approximately $0.1 million. Net non-cash charges were driven by $0.5 million in non-cash stock compensation expense and $0.1 million in non-cash lease expense.

Net Cash Provided by Financing Activities

We generated $26.6 million in net cash from financing activities during the three months ended March 31, 2024, which was due to approximately $26.5 million in net proceeds from the January 2024 Offering and March 2024 Registered Direct Offering, and $0.1 million from the purchase of shares of common stock by employees under the 2021 Employee Stock Purchase Plan.

We generated $18.9 million in net cash from financing activities during the three months ended March 31, 2023, which was due to approximately $18.5 million in net proceeds from the February 2023 Offering, $0.3 million in net proceeds under a Controlled Equity OfferingSM Sales Agreement with Cantor Fitzgerald & Co., and $0.1 million from the purchase of shares of common stock by employees under the Company's 2021 Employee Stock Purchase Plan.

Off-Balance Sheet Arrangements

We have not entered into any off-balance sheet financing arrangements as of March 31, 2024.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK.

Not applicable.

ITEM 4. CONTROLS AND PROCEDURES

Evaluation of Disclosure Controls and Procedures

As of the end of the period covered by this Quarterly Report on Form 10-Q, our principal executive officer and our principal financial officer (the “Certifying Officers”), evaluated the effectiveness of our disclosure controls and procedures. Disclosure controls and procedures are controls and procedures designed to reasonably assure that information required to be disclosed in our reports filed under the Securities Exchange Act of 1934 (the “Exchange Act”), such as this Quarterly Report on Form 10-Q, is recorded, processed, summarized and reported within the time periods specified in the SEC rules and forms. Disclosure controls and procedures are also designed to reasonably assure that such information is accumulated and communicated to our management, including the Certifying Officers, as appropriate to allow timely decisions regarding required disclosure. Based on these evaluations, the Certifying Officers have concluded, that, as of the end of the period covered by this Quarterly Report on Form 10-Q:

(a)our disclosure controls and procedures were effective to provide reasonable assurance that information required to be disclosed by us in the reports we file or submit under the Exchange Act was recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms; and

(b)our disclosure controls and procedures were effective to provide reasonable assurance that material information required to be disclosed by us in the reports we file or submit under the Exchange Act was accumulated and communicated to our management, including the Certifying Officers, as appropriate to allow timely decisions regarding required disclosure.

Changes in Internal Control over Financial Reporting

There has been no change in our internal control over financial reporting (as defined in Rule 13a-15(f) and 15d-15(f) under the Exchange Act) that occurred during the quarter ended March 31, 2024 that has materially affected, or is reasonably likely to materially affect, our internal control over financial reporting.

PART II - OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

In December 2020, we entered into 3D Medicines Agreement. In November 2022, we announced that we had agreed with 3D Medicines for 3D Medicines to participate in the REGAL study through the inclusion of approximately 20 patients from mainland China.

In accordance with the terms of the 3D Medicines Agreement and the Side Letter, we had expected that 3D Medicines would begin enrolling patients in mainland China in the REGAL study in the second half of 2023 and subsequently make two development milestone payments totaling $13.0 million. Patients were enrolled in the REGAL study in Taiwan, which is part of the 3DMed Territory, prior to the second half of 2023.

On December 20, 2023, we commenced a binding arbitration proceeding against 3D Medicines, administered by the Hong Kong International Arbitration Centre and governed by New York State law as per the 3D Medicines Agreement. The arbitration proceeding involves, among other things, the trigger and payment of the relevant milestone payments due to us as well as 3D Medicines’ failure to use commercially reasonable best efforts to develop GPS in the 3DMed Territory, and particularly in mainland China.

We have engaged an international law firm with expertise in mainland China to assist us with the arbitration proceeding. While we are unable at this time to predict with certainty the outcome of the arbitration proceeding, or the timing of the receipt of any milestone payments and other damages it is seeking in the arbitration proceeding, if at all, we believe that our claims are meritorious.

ITEM 1A. RISK FACTORS

Please refer to our note on forward-looking statements on page 2 of this Quarterly Report on Form 10-Q, which is incorporated into this item by reference.

In addition to the other information set forth in this report, you should carefully consider the risk factors discussed in our 2023 Annual Report. The risks described in such 2023 Annual Report are not the only risks we face. Additional risks and uncertainties not currently known to us or that we currently deem to be immaterial also may materially and adversely affect our business, financial condition, operating results and stock price.

ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS

None.

ITEM 3. DEFAULTS UPON SENIOR SECURITIES

None.

ITEM 4. MINE SAFETY DISCLOSURES

Not applicable.

ITEM 5. OTHER INFORMATION

None of our directors or officers have adopted, modified, or terminated any trading plans under Rule10b5-1 of the Exchange Act or any similar arrangements during the first quarter of 2024.

ITEM 6. EXHIBITS

Exhibit
#

Description

Form

Exhibit

Filing Date

3.1

Composite Amended and Restated Certificate of Incorporation of the Registrant (formerly, Galena Biopharma, Inc.) amended as of December 27, 2017

10-K

3.1

April 13, 2018

3.2

Amended and Restated By-Laws of the Registrant

8-K

3.3

January 5, 2018

4.1

Form of Common Warrant issued in connection with January 2024 Offering

8-K

4.2

January 8, 2024

4.2

Form of Pre-Funded Warrant issued in connection with January 2024 Offering

8-K

4.1

January 8, 2024

4.3

Form of Common Warrant issued in connection with March 2024 Registered Direct Offering

8-K

4.2

March 15, 2024

4.4

Form of Pre-Funded Warrant issued in connection with March 2024 Registered Direct Offering

8-K

4.1

March 15, 2024

10.1

Form of Placement Agency Agreement entered into in connection with January 2024 Offering

8-K

1.1

January 8, 2024

10.2

Form of Securities Purchase Agreement, dated as of January 8, 2024, by and among SELLAS Life Sciences Group, Inc. and the purchasers party hereto.

8-K

10.1

January 8, 2024

10.3

Form of Placement Agency Agreement entered into in connection with March 2024 Registered Direct Offering

8-K

1.1

March 15, 2024

10.4

Form of Securities Purchase Agreement, dated as of March 15, 2024, by and among SELLAS Life Sciences Group, Inc. and the purchasers party hereto.

8-K

10.1

March 15, 2024

31.1

Certification of Principal Executive Officer pursuant to Rule13a-14(a) and Rule 15d-14(a) of the Securities and Exchange Act, as amended.**

31.2

Certification of Principal Financial Officer pursuant to Rule13a-14(a) and Rule 15d-14(a) of the Securities and Exchange Act, as amended.**

32.1

Certification of Principal Executive Officer pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. ***

32.2

Certification of Principal Financial Officer pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002. ***

101.INS

XBRL Instance Document.*

101.SCH

XBRL Taxonomy Extension Schema.*

101.CAL

XBRL Taxonomy Extension Calculation Linkbase.*

101.DEF

XBRL Taxonomy Extension Definition Linkbase.*

101.LAB

XBRL Taxonomy Extension Label Linkbase.*

101.PRE

XBRL Taxonomy Extension Presentation Linkbase.*


*			Indicates management contract or compensatory plans or arrangements.
**			Filed herewith
***			The certifications attached as Exhibit 32.1 and Exhibit 32.2 accompany this Quarterly Report on Form 10-Q pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, and shall not be deemed “filed” by the Company for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liability of that section, nor shall they be deemed incorporated by reference into any filing of the registrant under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, whether made before or after the date hereof, regardless of any general incorporation language in such filing.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.


			SELLAS Life Sciences Group, Inc.

			By:						/s/ Angelos M. Stergiou

									Angelos M. Stergiou, MD, ScD h.c.
									President and Chief Executive Officer
									(Principal Executive Officer)

									Date: May 14, 2024

			By:						/s/ John T. Burns

									John T. Burns, CPA
									Chief Financial Officer
									(Principal Financial and Principal Accounting Officer)

									Date: May 14, 2024

Exhibit 31.1

CERTIFICATION OF PRINCIPAL EXECUTIVE OFFICER

PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Angelos M. Stergiou, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of SELLAS Life Sciences Group, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Dated: May 14, 2024


			/s/ Angelos M. Stergiou

			Angelos M. Stergiou, MD, ScD h.c.
			President and Chief Executive Officer (Principal Executive Officer)

Exhibit 31.2

CERTIFICATION OF PRINCIPAL FINANCIAL OFFICER

PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, John T. Burns, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of SELLAS Life Sciences Group, Inc.;

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Dated: May 14, 2024


			/s/ John T. Burns

			John T. Burns, CPA
			Chief Financial Officer (Principal Financial and Principal Accounting Officer)

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the accompanying Quarterly Report of SELLAS Life Sciences Group, Inc., (the “Company”) on Form 10-Q for the period ended March 31, 2024 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), the undersigned officer of the Company certifies, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that to his knowledge:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the Company’s financial condition and results of operations.


			By:						/s/ Angelos M. Stergiou

									Angelos M. Stergiou, MD, ScD h.c.
									President and Chief Executive Officer (Principal Executive Officer)

									Date: May 14, 2024

A signed original of this written statement required by Rule 13a-14(b) of the Securities Exchange Act of 1934, as amended, and 18 U.S.C. Section 1350 has been provided to the Registrant and will be retained by the Registrant and furnished to the Securities and Exchange Commission or its staff upon request.

This certification accompanies the Form 10-Q to which it relates, is not deemed filed with the Securities and Exchange Commission and is not to be incorporated by reference into any filing of the Registrant under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, (whether made before or after the date of the Report), irrespective of any general incorporation language contained in such filing.

Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the Company’s financial condition and results of operations.


			By:						/s/ John T. Burns

									John T. Burns, CPA
									Chief Financial Officer (Principal Financial and Principal Accounting Officer)

									Date: May 14, 2024

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2024	May 13, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
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		57,754,928
Entity Central Index Key	0001390478
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 18,415	$ 2,530
Restricted cash and cash equivalents	100	100
Prepaid expenses and other current assets	2,986	542
Total current assets	21,501	3,172
Operating lease right-of-use assets	747	858
Goodwill	1,914	1,914
Deposits and other assets	272	275
Total assets	24,434	6,219
Current liabilities:
Accounts payable	7,407	5,639
Accrued expenses and other current liabilities	6,542	7,650
Operating lease liabilities	488	446
Total current liabilities	14,437	13,735
Operating lease liabilities, non-current	313	460
Total liabilities	14,750	14,195
Commitments and contingencies (Note 7)
Stockholders’ (deficit) 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, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value; 350,000,000 shares authorized, 56,267,670 and 32,132,890 shares issued and outstanding at March 31, 2024 and December 31, 2023, respectively	5	3
Additional paid-in capital	236,489	209,265
Accumulated deficit	(226,810)	(217,244)
Total stockholders’ equity (deficit)	9,684	(7,976)
Total liabilities and stockholders’ equity (deficit)	$ 24,434	$ 6,219

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
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)	56,267,670	32,132,890
Common stock, shares outstanding (in shares)	56,267,670	32,132,890
Series A Preferred Stock
Preferred stock, shares authorized (in shares)	17,500	17,500

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating expenses:
Research and development	$ 5,111	$ 7,174
General and administrative	4,534	4,107
Total operating expenses	9,645	11,281
Loss from operations	(9,645)	(11,281)
Non-operating income:
Change in fair value of warrant liability	0	2
Interest income	79	182
Total non-operating income	79	184
Net loss	$ (9,566)	$ (11,097)
Per share information:
Net loss per common share, basic (in dollars per share)	$ (0.21)	$ (0.47)
Net loss per common share, diluted (in dollars per share)	$ (0.21)	$ (0.47)
Weighted-average common shares outstanding, basic (in shares)	44,812,996	23,547,562
Weighted-average common shares outstanding, diluted (in shares)	44,812,996	23,547,562

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Common Stock Pre-Funded Warrants	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2022		21,005,405
Beginning balance at Dec. 31, 2022	$ 4,851	$ 2		$ 184,753	$ (179,904)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		7,220,217
Issuance of common stock and common stock warrants, net of issuance costs	18,554	$ 1		18,553
Issuance of common stock, net of issuance costs (in shares)		76,882
Issuance of common stock, net of issuance costs	268			268
Issuance of common stock under employee stock purchase plan (in shares)		45,416
Issuance of common stock under employee stock purchase plan	53			53
Stock-based compensation	540			540
Net loss	(11,097)				(11,097)
Ending balance (in shares) at Mar. 31, 2023		28,347,920
Ending balance at Mar. 31, 2023	$ 13,169	$ 3		204,167	(191,001)
Beginning balance (in shares) at Dec. 31, 2023	32,132,890	32,132,890
Beginning balance at Dec. 31, 2023	$ (7,976)	$ 3		209,265	(217,244)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock and common stock warrants, net of issuance costs (in shares)		21,130,000
Issuance of common stock and common stock warrants, net of issuance costs	26,650	$ 2		26,648
Issuance of common stock upon the exercise of pre-funded warrants (in shares)		65,750	2,884,658
Issuance of common stock upon the exercise of pre-funded warrants	49			49
Issuance of common stock under employee stock purchase plan (in shares)		54,372
Issuance of common stock under employee stock purchase plan	51			51
Stock-based compensation	476			476
Net loss	$ (9,566)				(9,566)
Ending balance (in shares) at Mar. 31, 2024	56,267,670	56,267,670
Ending balance at Mar. 31, 2024	$ 9,684	$ 5		$ 236,489	$ (226,810)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (9,566)	$ (11,097)
Adjustment to reconcile net loss to net cash used in operating activities:
Non-cash stock-based compensation	476	540
Non-cash lease expense	138	87
Change in fair value of common stock warrants	0	(2)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,441)	(1,474)
Accounts payable	1,806	(284)
Accrued expenses and other current liabilities	(1,042)	196
Operating lease liabilities	(132)	(93)
Net cash used in operating activities	(10,761)	(12,127)
Cash flows from financing activities:
Proceeds from issuance of common stock and common stock warrants, net of issuance costs	26,546	18,583
Proceeds from issuance of common stock, net of issuance costs	0	268
Proceeds from the exercise of common stock warrants	49	0
Proceeds from employee stock purchases	51	53
Net cash provided by financing activities	26,646	18,904
Net increase in cash, cash equivalents, restricted cash, and restricted cash equivalents	15,885	6,777
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the beginning of period	2,630	17,225
Cash, cash equivalents, restricted cash, and restricted cash equivalents at the end of period	18,515	24,002
Supplemental disclosure of cash flow information:
Cash received during the period for interest	79	182
Supplemental disclosure of non-cash investing and financing activities:
Non-cash acquisition of in-process research and development	0	5,500
Offering expenses included in accounts payable and accrued expenses and other current liabilities	104	29
Warrant modifications recorded in stockholders' equity (deficit)	$ 725	$ 252

Description of Business	3 Months Ended
Description of Business	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Overview SELLAS Life Sciences Group, Inc. is a late-stage clinical biopharmaceutical company focused on novel therapeutics 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 an array of tumor types. 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 is SLS009 (formerly GFH009), a small molecule, highly selective cyclin-dependent kinase 9 ("CDK9") inhibitor, which the Company licensed from GenFleet Therapeutics (Shanghai), Inc. ("GenFleet"), for all therapeutic and diagnostic uses in the world outside of mainland China, Hong Kong, Macau and Taiwan ("SLS009 Territory").

Liquidity	3 Months Ended
Liquidity	Mar. 31, 2024
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, 2024, has an accumulated deficit of $226.8 million. During the three months ended March 31, 2024, the Company incurred a net loss of $9.6 million, and used $10.8 million of cash in operations. The Company expects to continue to generate operating losses and negative cash flows from operations 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 March 19, 2024, the Company consummated the March 2024 Registered Direct Offering priced at-the-market under Nasdaq rules, in which it entered into a Securities Purchase Agreement with two institutional investors pursuant to which the Company agreed to issue and sell 11,000,000 shares of its common stock and 2,029,316 pre-funded warrants exercisable for shares of common stock. Each share of common stock was sold at a purchase price of $1.535 and each pre-funded warrant was sold at a purchase price of $1.5349. The net proceeds to the Company from the March 2024 Registered Direct Offering were approximately $18.5 million, after deducting the placement agent's fees and related offering expenses. In a concurrent private placement, the Company agreed to issue to the two institutional investors exercisable for up to an aggregate of 13,029,316 shares of common stock warrants at an exercise price of $1.41 per share. Subsequent to the closing of the March 2024 Registered Direct Offering, all of the pre-funded warrants have been exercised for shares of common stock. On January 8, 2024, the Company consummated the January 2024 Offering on a "reasonable best efforts" basis, issuing 10,130,000 shares of common stock and an aggregate of 1,870,000 pre-funded warrants exercisable for shares of common stock, together with accompanying warrants to purchase an aggregate of 12,000,000 shares of common stock. Each share of common stock and accompanying common warrant were sold together at a combined offering price of $0.75, and each pre-funded warrant and accompanying common warrant were sold together at a combined offering price of $0.7499. The net proceeds to the Company from the January 2024 Offering were approximately $8.2 million, after deducting placement agents' fees and related offering expenses. Subsequent to the closing of the January 2024 Offering, all of the pre-funded warrants have been exercised for shares of common stock. In December 2020, the Company, together with its wholly-owned subsidiary, SLSG Limited, LLC, entered into an Exclusive License Agreement (the “3D Medicines Agreement”) with 3D Medicines Inc. ("3D Medicines"), pursuant to which the Company granted 3D Medicines 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 product candidates for all therapeutic and other diagnostic uses in mainland China, Hong Kong, Macau and Taiwan ("3DMed Territory"). As of March 31, 2024, the Company has received an aggregate of $10.5 million in upfront payments and certain technology transfer and regulatory milestones. There is a total of $191.5 million in potential future development, regulatory, and sales milestones, not including future royalties, that remains under the 3D Medicines Agreement, which milestones are all variable in nature and not under the Company's control. As of March 31, 2024, the Company had cash and cash equivalents of approximately $18.4 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 will not be sufficient to fund its current planned operations for at least the next twelve months from the date of issuance of these consolidated financial statements. The Company will require substantial additional financing to commercially develop any current or future product candidates. If the Company is unable to obtain additional funding on a timely basis, it will be required to scale back its plans and place certain activities on hold. The Company currently does not have any commitments to obtain additional funds. The Company's management continues to evaluate different strategies to obtain the required funding for future operations. These strategies may include public and private placements of equity and/or debt securities, as well as payments from potential strategic research and development collaborations or licensing and/or marketing arrangements with pharmaceutical companies. Additionally, the Company continues to pursue discussions with global and regional pharmaceutical companies for licensing and/or co-development rights to the Company's product candidates. There can be no assurance that these future funding efforts will be successful.

Basis of Presentation and Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Basis of Presentation and Significant Accounting Policies

Basis of Presentation

Principles of Consolidation

Unaudited Interim Results

Net Loss Per Share

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,
	2024	2023
Common stock warrants	41,802	12,361
Stock options	2,155	1,661
Restricted stock units ("RSUs")	738	444
	44,695	14,466

Recent Accounting Standards Adopted

Recent Accounting Standards Not Yet Adopted

Fair Value Measurements

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

The following tables present information about the Company's assets measured at fair value on a recurring basis in the consolidated balance sheets (in thousands):


Description	March 31, 2024		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	18,247	$	18,247	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	18,347	$	18,347	$	—	$	—


Description	December 31, 2023		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,314	$	2,314	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	2,414	$	2,414	$	—	$	—

The Company did not transfer any financial instruments into or out of Level 3 classification during the three months ended March 31, 2024 or during the year ended December 31, 2023.

Acquired In-Process Research and Development	3 Months Ended
Acquired In-Process Research and Development	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Acquired In-Process Research and Development	Acquired In-Process Research and Development Exclusive License Agreement with GenFleet Therapeutics (Shanghai) Inc. On March 31, 2022, the Company entered into an exclusive license agreement with GenFleet pursuant to which GenFleet granted to the Company a sublicensable royalty-bearing license under certain of its intellectual property, to develop, manufacture, and commercialize SLS009 for the treatment, diagnosis or prevention of disease in humans and animals in the SLS009 Territory. In consideration for the exclusive license, the Company agreed to pay to GenFleet (i) an upfront and technology transfer fee of $10.0 million, all of which has been paid, (ii) development and regulatory milestone payments for up to three indications totaling up to $48.0 million in the aggregate upon the achievement of such milestones, and (iii) sales milestone payments totaling up to $92.0 million in the aggregate upon the achievement of certain net sales thresholds in a given calendar year. The Company also agreed to pay GenFleet single-digit tiered royalties based upon a percentage of annual net sales, with the royalty rate escalating based on the level of annual net sales of SLS009 in the SLS009 Territory ranging from the low to high single digits.

Balance Sheet Accounts

3 Months Ended

Mar. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Accounts

Prepaid expenses and other current assets consist of the following (in thousands):


	March 31, 2024		December 31, 2023
Insurance	$	1,092	$	87
Clinical trial costs	1,690		399
Professional fees	115		56
Other	89		—
Prepaid expenses and other current assets	$	2,986	$	542

Accrued expenses and other current liabilities consist of the following (in thousands):


	March 31, 2024		December 31, 2023
Clinical trial costs	$	4,186	$	5,672
Compensation and related benefits	1,590		1,493
Professional fees	714		443
Other	52		42
Accrued expenses and other current liabilities	$	6,542	$	7,650

Commitments and Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

Rent expense related to the Company's operating leases was approximately $0.1 million for each of the three months ended March 31, 2024 and 2023.

The Company made cash payments related to its operating leases of approximately $0.1 million for each of the three months ended March 31, 2024 and 2023.

Future minimum lease payments are as follows as of March 31, 2024 (in thousands):


Future minimum lease payments:
2024 (remaining)	$	401
2025	477
Total future minimum lease payments	878
Less: imputed interest	(77)
Current and non-current operating lease liabilities	$	801

Legal Proceedings

Stockholders’ Equity (Deficit)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Stockholders’ Equity (Deficit)

Preferred Stock

The Company has authorized up to 5,000,000 shares of preferred stock, $0.0001 par value per share, for issuance. There were no preferred shares outstanding as of March 31, 2024 and December 31, 2023.

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, 2024, the Company has shares of common stock reserved for future issuance as follows (in thousands):


Warrants outstanding			41,802
Stock options outstanding			2,155
RSUs outstanding			738
Shares reserved for future issuance under the 2023 Amended and Restated Equity Incentive Plan			3,003
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan			129
Total common stock reserved for future issuance			47,827

Warrants to Acquire Shares of Common Stock

3 Months Ended

Mar. 31, 2024

Warrants and Rights Note Disclosure [Abstract]

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, 2024 (in thousands except per share data):


Warrant Issuance	Outstanding, December 31, 2023	Granted	Exercised	Expired	Outstanding, March 31, 2024	Exercise Price per Share		Expiration
Warrants classified as equity:
March 2024 Registered Direct Offering	—	13,029	—	—	13,029	$	1.41	September 2029
March 2024 Registered Direct Offering Pre-Funded Warrants	—	2,029	(1,015)	—	1,014	$	—	n/a
January 2024 Offering	—	12,000	(60)	—	11,940	$	0.75	January 2029
January 2024 Offering Pre-Funded Warrants	—	1,870	(1,870)	—	—	$	—	n/a
November 2023 Registered Direct Offering	3,652	—	—	—	3,652	$	0.75	January 2029

February 2023 Offering	7,206	—	(5)	—	7,201	$	0.75	February 2028
April 2022 Offering	766	—	—	—	766	$	5.40	April 2027
April 2022 Offering - Modified Warrants	3,864	—	—	—	3,864	$	0.75	January 2029
January 2020 Offering	309	—	—	—	309	$	3.93	July 2025
July 2020 PIPE Offering	25	—	—	—	25	$	3.30	August 2025
Other	32	—	—	(30)	2	$	7.50	June 2024
	15,854	28,928	(2,950)	(30)	41,802

Subsequent to March 31, 2024, the remaining 1,014,658 pre-funded warrants issued in the March 2024 Registered Direct Offering were exercised into shares of common stock.

Warrants Classified as Equity

However, there was no net impact to the consolidated statements of stockholders' equity (deficit) because the warrants are equity classified.

Licensing Revenue	3 Months Ended
Licensing Revenue	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Licensing Revenue	Licensing Revenue Exclusive License Agreement with 3D Medicines Inc. In December 2020, the Company entered into the 3D Medicines Agreement pursuant to which the Company granted 3D Medicines 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 (referred to as GPS Plus) product candidates ("GPS Licensed Products") for all therapeutic and other diagnostic uses in the 3DMed Territory. In partial consideration for the rights granted by the Company, 3D Medicines 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. 3D Medicines 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. Revenue Recognition At inception, the Company evaluated the 3D Medicines Agreement under ASC 606 and recognized an initial transaction price of $9.5 million, which included the $7.5 million upfront fee as well as $2.0 million in development milestones that were assessed to be probable of being achieved, while the remaining milestones were variable consideration subject to constraint at inception. In the first quarter of 2022, an additional $1.0 million in licensing revenue was recognized upon approval by China’s National Medical Products Administration (“NMPA”) for a small Phase 1 clinical trial investigating safety of GPS in China. There is $191.5 million in potential future development, regulatory, and sales milestones, not including future royalties, remaining under the 3D Medicines Agreement as of March 31, 2024, which milestones are variable in nature and not under the Company's control. At the end of each reporting period, the Company reevaluates 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. There was no licensing revenue recognized during each of the three months ended March 31, 2024 and 2023. There was no cost of licensing revenue recognized during each of the three months ended March 31, 2024 and 2023.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

2017 Equity Incentive Plan

2023 Amended and Restated Equity Incentive Plan

On September 10, 2019, the 2019 Equity Incentive Plan ("2019 Equity Plan") was approved by the stockholders of the Company. On June 20, 2023, an amendment to the 2019 Equity Plan was approved by the

As of March 31, 2024, approximately 3,003,000 shares of common stock were reserved for future grants under the 2023 Amended and Restated Equity Incentive Plan.


	Three Months Ended March 31,
		2024		2023
Research and development		$	85	$	96
General and administrative		391		444
Total stock-based compensation		$	476	$	540

Options to Purchase Shares of Common Stock

The following table summarizes stock option activity of the Company for the three months ended March 31, 2024:


	Total Number of Shares (In Thousands)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value (In Thousands)
Outstanding at December 31, 2023	1,607	$	5.92		$	—
Granted	671	0.53

Canceled	(123)	3.44
Outstanding at March 31, 2024	2,155	$	4.38	8.44	$	308
Options exercisable at March 31, 2024	883	$	7.38	7.43	$	—


	Three Months Ended March 31,
	2024		2023
Risk free interest rate	4.01	%	3.79	%
Volatility	130.41	%	127.68	%
Expected lives (years)	6.19		6.20
Expected dividend yield	—	%	—	%

The weighted-average grant date fair value of options granted during the three months ended March 31, 2024 and 2023 was $0.48 and $2.95, respectively.

Time-vested RSUs and RSUs with Performance Conditions

The following table summarizes RSU activity of the Company for the three months ended March 31, 2024:


	Shares (In Thousands)	Weighted Average Grant Date Fair Value
Unvested at December 31, 2023	338	$	2.99
Granted	429	$	0.52
Canceled	(29)	$	1.39
Unvested at March 31, 2024	738	$	1.62

2021 Employee Stock Purchase Plan

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company evaluated all events or transactions that occurred after March 31, 2024 up through the date these consolidated 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.

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net loss	$ (9,566)	$ (11,097)

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Basis of Presentation and Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
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 ASC and Accounting Standards Updates ("ASUs") 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, SELLAS Life Sciences Group, Ltd., a privately held Bermuda exempted company, 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.
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 Standards Adopted and Recent Accounting Standards Not Yet Adopted	Recent Accounting Standards Adopted In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities to disclose significant segment expenses regularly provided to the chief operating decision-maker. Public entities with a single reporting segment have to provide all disclosures required by ASC 280, including the significant segment expense disclosures. ASU No. 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods in fiscal years beginning after December 15, 2024. This ASU became effective for the Company on January 1, 2024 and did not have a material impact on the consolidated financial statements. Recent Accounting Standards Not Yet Adopted In December 2023, the FASB issued ASU No. 2023-09, Improvements to Income Tax Disclosures, which amends the guidance in ASC 740, Income Taxes. The ASU is intended to improve the transparency of income tax disclosures by prescribing standard categories and greater disaggregation of information in the effective tax rate reconciliation, disclosure of income taxes paid disaggregated by jurisdiction, and modifies other income tax-related disclosures. ASU No. 2023-09 is effective for fiscal years beginning after December 15, 2024 and allows for adoption either prospectively or retrospectively. Early adoption is permitted. The Company is currently evaluating the impact of the ASU on the income tax disclosures within the consolidated financial statements but does not expect a material impact upon adoption.

Basis of Presentation and Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

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,
	2024	2023
Common stock warrants	41,802	12,361
Stock options	2,155	1,661
Restricted stock units ("RSUs")	738	444
	44,695	14,466

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measured at Fair Value

The following tables present information about the Company's assets measured at fair value on a recurring basis in the consolidated balance sheets (in thousands):


Description	March 31, 2024		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	18,247	$	18,247	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	18,347	$	18,347	$	—	$	—


Description	December 31, 2023		Quoted Prices In Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	2,314	$	2,314	$	—	$	—
Restricted cash equivalents	100		100		—		—
Total assets measured and recorded at fair value	$	2,414	$	2,414	$	—	$	—

Balance Sheet Accounts (Tables)

3 Months Ended

Mar. 31, 2024

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, 2024		December 31, 2023
Insurance	$	1,092	$	87
Clinical trial costs	1,690		399
Professional fees	115		56
Other	89		—
Prepaid expenses and other current assets	$	2,986	$	542

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following (in thousands):


	March 31, 2024		December 31, 2023
Clinical trial costs	$	4,186	$	5,672
Compensation and related benefits	1,590		1,493
Professional fees	714		443
Other	52		42
Accrued expenses and other current liabilities	$	6,542	$	7,650

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments

Future minimum lease payments are as follows as of March 31, 2024 (in thousands):


Future minimum lease payments:
2024 (remaining)	$	401
2025	477
Total future minimum lease payments	878
Less: imputed interest	(77)
Current and non-current operating lease liabilities	$	801

Stockholders’ Equity (Deficit) (Tables)

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

As of March 31, 2024, the Company has shares of common stock reserved for future issuance as follows (in thousands):


Warrants outstanding			41,802
Stock options outstanding			2,155
RSUs outstanding			738
Shares reserved for future issuance under the 2023 Amended and Restated Equity Incentive Plan			3,003
Shares reserved for future issuance under the 2021 Employee Stock Purchase Plan			129
Total common stock reserved for future issuance			47,827

Warrants to Acquire Shares of Common Stock (Tables)

3 Months Ended

Mar. 31, 2024

Warrants and Rights Note Disclosure [Abstract]

Schedule of Warrant Activity

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, 2024 (in thousands except per share data):


Warrant Issuance	Outstanding, December 31, 2023	Granted	Exercised	Expired	Outstanding, March 31, 2024	Exercise Price per Share		Expiration
Warrants classified as equity:
March 2024 Registered Direct Offering	—	13,029	—	—	13,029	$	1.41	September 2029
March 2024 Registered Direct Offering Pre-Funded Warrants	—	2,029	(1,015)	—	1,014	$	—	n/a
January 2024 Offering	—	12,000	(60)	—	11,940	$	0.75	January 2029
January 2024 Offering Pre-Funded Warrants	—	1,870	(1,870)	—	—	$	—	n/a
November 2023 Registered Direct Offering	3,652	—	—	—	3,652	$	0.75	January 2029

February 2023 Offering	7,206	—	(5)	—	7,201	$	0.75	February 2028
April 2022 Offering	766	—	—	—	766	$	5.40	April 2027
April 2022 Offering - Modified Warrants	3,864	—	—	—	3,864	$	0.75	January 2029
January 2020 Offering	309	—	—	—	309	$	3.93	July 2025
July 2020 PIPE Offering	25	—	—	—	25	$	3.30	August 2025
Other	32	—	—	(30)	2	$	7.50	June 2024
	15,854	28,928	(2,950)	(30)	41,802

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Allocated Stock-based Compensation Expense


	Three Months Ended March 31,
		2024		2023
Research and development		$	85	$	96
General and administrative		391		444
Total stock-based compensation		$	476	$	540

Schedule of Stock Option Activity

The following table summarizes stock option activity of the Company for the three months ended March 31, 2024:


	Total Number of Shares (In Thousands)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value (In Thousands)
Outstanding at December 31, 2023	1,607	$	5.92		$	—
Granted	671	0.53

Canceled	(123)	3.44
Outstanding at March 31, 2024	2,155	$	4.38	8.44	$	308
Options exercisable at March 31, 2024	883	$	7.38	7.43	$	—

Schedule of Assumptions for Option Grants Issued


	Three Months Ended March 31,
	2024		2023
Risk free interest rate	4.01	%	3.79	%
Volatility	130.41	%	127.68	%
Expected lives (years)	6.19		6.20
Expected dividend yield	—	%	—	%

Schedule of RSU Activity

The following table summarizes RSU activity of the Company for the three months ended March 31, 2024:


	Shares (In Thousands)	Weighted Average Grant Date Fair Value
Unvested at December 31, 2023	338	$	2.99
Granted	429	$	0.52
Canceled	(29)	$	1.39
Unvested at March 31, 2024	738	$	1.62

Liquidity (Details) $ / shares in Units, $ in Thousands				3 Months Ended
Liquidity (Details) $ / shares in Units, $ in Thousands	Mar. 31, 2024 USD ($)	Mar. 19, 2024 USD ($) investor $ / shares shares	Jan. 08, 2024 USD ($) $ / shares shares	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accumulated deficit	$ 226,810			$ 226,810		$ 217,244
Net loss				9,566	$ 11,097
Net cash used in operating activities				10,761	$ 12,127
Upfront fee and milestone payments				10,500
Potential milestone payments to be received	191,500			191,500
Cash and cash equivalents	18,415			18,415		2,530
Restricted cash and cash equivalents	$ 100			$ 100		$ 100
March 2024 Registered Direct Offering
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of institutional investors \| investor		2
Number of shares of stock (in shares) \| shares		11,000,000
Offering price (in dollars per share) \| $ / shares		$ 1.535
March 2024 Registered Direct Offering \| Pre-Funded Warrants
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants exercisable (in shares) \| shares		2,029,316
Offering price (in dollars per share) \| $ / shares		$ 1.5349
Net proceeds of common stock		$ 18,500
Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock to be called by warrants (in shares) \| shares		13,029,316
Warrant exercise price (in dollars per share) \| $ / shares		$ 1.41
Public Offering
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares of stock (in shares) \| shares			10,130,000
Offering price (in dollars per share) \| $ / shares			$ 0.75
Public Offering \| Pre-Funded Warrants
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares of stock (in shares) \| shares			12,000,000
Offering price (in dollars per share) \| $ / shares			$ 0.7499
Net proceeds of common stock			$ 8,200
Common stock to be called by warrants (in shares) \| shares			1,870,000

Basis of Presentation and Significant Accounting Policies (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	44,695	14,466
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	41,802	12,361
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	2,155	1,661
Restricted stock units ("RSUs")
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)	738	444

Fair Value Measurements (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets:
Cash equivalents	$ 18,247	$ 2,314
Restricted cash equivalents	100	100
Total assets measured and recorded at fair value	18,347	2,414
Quoted Prices In Active Markets (Level 1)
Assets:
Cash equivalents	18,247	2,314
Restricted cash equivalents	100	100
Total assets measured and recorded at fair value	18,347	2,414
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
Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Restricted cash equivalents	0	0
Total assets measured and recorded at fair value	$ 0	$ 0

Acquired In-Process Research and Development (Details) - GenFleet Therapeutics (Shanghai) Inc $ in Millions	Mar. 31, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront fee	$ 10.0
Eligible payment from collaboration for development and regulatory milestone achievement under collaborations agreement	48.0
Maximum amount eligible for milestones under collaborations agreement	$ 92.0

Balance Sheet Accounts - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Insurance	$ 1,092	$ 87
Clinical trial costs	1,690	399
Professional fees	115	56
Other	89	0
Prepaid expenses and other current assets	$ 2,986	$ 542

Balance Sheet Accounts - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Clinical trial costs	$ 4,186	$ 5,672
Compensation and related benefits	1,590	1,493
Professional fees	714	443
Other	52	42
Accrued expenses and other current liabilities	$ 6,542	$ 7,650

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Operating lease, discount rate (as a percent)	13.00%
Operating lease, remaining term	1 year 6 months
Rent expense	$ 0.1	$ 0.1
Cash payments related to operating lease	$ 0.1	$ 0.1

Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024 (remaining)	$ 401
2025	477
Total future minimum lease payments	878
Less: imputed interest	(77)
Current and non-current operating lease liabilities	$ 801

Stockholders’ Equity (Deficit) - Narrative (Details) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
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
Preferred stock, shares outstanding (in shares)	0	0
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 (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details) - shares shares in Thousands	Mar. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	41,802
Stock options outstanding (in shares)	2,155	1,607
Total common stock reserved for future issuance (in shares)	47,827
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)	3,003
2021 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance (in shares)	129
Restricted stock units ("RSUs")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)	738	338

Warrants to Acquire Shares of Common Stock - Schedule of Warrant Activity (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)
Outstanding, end of period (in shares)	41,802
Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	15,854
Granted (in shares)	28,928
Exercised (in shares)	(2,950)
Expired (in shares)	(30)
Outstanding, end of period (in shares)	41,802
March 2024 Registered Direct Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	0
Granted (in shares)	13,029
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	13,029
Exercise price (in dollars per share) \| $ / shares	$ 1.41
March 2024 Registered Direct Offering Pre-Funded Warrants \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	0
Granted (in shares)	2,029
Exercised (in shares)	(1,015)
Expired (in shares)	0
Outstanding, end of period (in shares)	1,014
Exercise price (in dollars per share) \| $ / shares	$ 0
January 2024 Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	0
Granted (in shares)	12,000
Exercised (in shares)	(60)
Expired (in shares)	0
Outstanding, end of period (in shares)	11,940
Exercise price (in dollars per share) \| $ / shares	$ 0.75
January 2024 Offering Pre-Funded Warrants \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	0
Granted (in shares)	1,870
Exercised (in shares)	(1,870)
Expired (in shares)	0
Outstanding, end of period (in shares)	0
Exercise price (in dollars per share) \| $ / shares	$ 0
November 2023 Registered Direct Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	3,652
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	3,652
Exercise price (in dollars per share) \| $ / shares	$ 0.75
February 2023 Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	7,206
Granted (in shares)	0
Exercised (in shares)	(5)
Expired (in shares)	0
Outstanding, end of period (in shares)	7,201
Exercise price (in dollars per share) \| $ / shares	$ 0.75
April 2022 Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	766
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	766
Exercise price (in dollars per share) \| $ / shares	$ 5.40
April 2022 Offering - Modified Warrants \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	3,864
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	3,864
Exercise price (in dollars per share) \| $ / shares	$ 0.75
January 2020 Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	309
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	309
Exercise price (in dollars per share) \| $ / shares	$ 3.93
July 2020 PIPE Offering \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	25
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	0
Outstanding, end of period (in shares)	25
Exercise price (in dollars per share) \| $ / shares	$ 3.30
Other \| Common stock warrants
Class of Warrant or Right, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	32
Granted (in shares)	0
Exercised (in shares)	0
Expired (in shares)	(30)
Outstanding, end of period (in shares)	2
Exercise price (in dollars per share) \| $ / shares	$ 7.50

Warrants to Acquire Shares of Common Stock - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	May 14, 2024	Mar. 31, 2024	Mar. 19, 2024
Common stock warrants
Class of Warrant or Right [Line Items]
Exercised (in shares)		2,950,000
January 2024 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Exercised (in shares)		60,000
Exercise price (in dollars per share)		$ 0.75
April 2022 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Exercised (in shares)		0
Exercise price (in dollars per share)		$ 5.40
February 2023 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Exercised (in shares)		5,000
Exercise price (in dollars per share)		$ 0.75
March 2024 Registered Direct Offering
Class of Warrant or Right [Line Items]
Offering price (in dollars per share)			$ 1.535
March 2024 Registered Direct Offering \| Pre-Funded Warrants
Class of Warrant or Right [Line Items]
Offering price (in dollars per share)			$ 1.5349
March 2024 Registered Direct Offering \| Subsequent Event \| Pre-Funded Warrants
Class of Warrant or Right [Line Items]
Exercised (in shares)	1,014,658
Underwriting Agreement \| January 2024 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Offering price (in dollars per share)		$ 0.75
Underwriting Agreement \| April 2022 Offering
Class of Warrant or Right [Line Items]
Warrants not settleable in cash, fair value disclosure		$ 0.7
Underwriting Agreement \| April 2022 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Common stock to be called by warrants (in shares)		3,863,851
Exercise price (in dollars per share)		$ 0.75
Underwriting Agreement \| November 2023 Registered Direct \| Common stock warrants
Class of Warrant or Right [Line Items]
Common stock to be called by warrants (in shares)		3,652,300
Exercise price (in dollars per share)		$ 0.75
Underwriting Agreement \| February 2023 Offering \| Common stock warrants
Class of Warrant or Right [Line Items]
Common stock to be called by warrants (in shares)		7,220,217
Exercise price (in dollars per share)		$ 0.75

Licensing Revenue (Details) - USD ($)		1 Months Ended	3 Months Ended
Licensing Revenue (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2020	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Revenue from Contract with Customer [Abstract]
Upfront cash payment received		$ 7,500,000
Future milestone payments received		194,500,000
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	$ 191,500,000		$ 191,500,000
Licensing revenue			0	$ 0
Cost of licensing revenue			$ 0	$ 0

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Jun. 20, 2023	Apr. 22, 2021	Mar. 31, 2024	Mar. 31, 2023	Sep. 10, 2019	Dec. 29, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)			47,827,000
Closing price of the Company's common stock (in dollars per share)			$ 1.01
Weighted average grant date fair value (in dollars per share)			$ 0.48	$ 2.95
Averages contractual term			10 years
Expected dividend yield (as a percent)			0.00%	0.00%
Unrecognized compensation cost, options			$ 2,500
Proceeds from employee stock purchases			$ 51	$ 53
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average recognition period			2 years 3 months 18 days
Restricted stock units ("RSUs")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in dollars per share)			$ 0.52
Weighted average recognition period			2 years 1 month 6 days
Unrecognized compensation cost			$ 1,100
RSUs vested (in shares)			0
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 Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance (in shares)						22,000
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance (in shares)					6,036,000
Increase in number of shares authorized (in shares)	3,000,000
Shares of common stock reserved for issuance (in shares)			3,003,000
2021 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for issuance (in shares)		300,000
2021 ESPP \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance (in shares)			129,085
Cash earnings contributed per year		20.00%
Purchase price of common stock		85.00%
Offering period		6 months
Shares purchased for award			54,372
Proceeds from employee stock purchases			$ 100

Stock-Based Compensation - Schedule of Allocated Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 476	$ 540
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	85	96
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 391	$ 444

Stock-Based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Total Number of Shares (In Thousands)
Outstanding, beginning balance (in shares)	1,607
Granted (in shares)	671
Canceled (in shares)	(123)
Outstanding, ending balance (in shares)	2,155
Options exercisable (in shares)	883
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 5.92
Granted (in dollars per share)	0.53
Canceled (in dollars per share)	3.44
Ending balance (in dollars per share)	4.38
Weighted Average Exercise Price, options exercisable (in dollars per share)	$ 7.38
Weighted Average Remaining Contractual Term, outstanding (in years)	8 years 5 months 8 days
Weighted Average Remaining Contractual Term, Options exercisable (in years)	7 years 5 months 4 days
Aggregate Intrinsic Value (In Thousands)
Outstanding	$ 308	$ 0
Aggregate Intrinsic Value, Options exercisable	$ 0

Stock-Based Compensation - Schedule of Assumptions for Option Grants Issued (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement [Abstract]
Risk free interest rate	4.01%	3.79%
Volatility	130.41%	127.68%
Expected lives (years)	6 years 2 months 8 days	6 years 2 months 12 days
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Schedule of RSU Activity (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 0.48	$ 2.95
Restricted stock units ("RSUs")
Shares
Beginning balance (in shares)	338
Granted (in shares)	429
Canceled (in shares)	(29)
Ending balance (in shares)	738
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 2.99
Granted (in dollars per share)	0.52
Canceled (in dollars per share)	1.39
Ending balance (in dollars per share)	$ 1.62