SELLAS Life Sciences Group, Inc.

1. Organization and 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. SELLAS' second product candidate is SLS009 (tambiciclib), 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"). Each of GPS and SLS009 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.

2. Liquidity

On October 24, 2025, the Company entered into a Warrant Inducement Agreement (the "October 2025 Inducement") with an institutional investor and holder of certain existing warrants to cash exercise (i) warrants to purchase 6,514,658 shares of common stock at an exercise price of $1.535 per share, previously issued in March 2024 (the "March 2024 Warrants"), and (ii) warrants to purchase 15,849,056 shares of common stock at an exercise price of $1.325 per share, previously issued in August 2024 (the "August 2024 Warrants"). The March 2024 Warrants and the August 2024 Warrants were exercised at their original issuance exercise price plus $0.125 per share of common stock in accordance with Nasdaq rules. In consideration of the investor's agreement to exercise the March 2024 Warrants and the August 2024 Warrants, the Company agreed to issue new warrants to the investor to purchase up to 22,363,714 shares of common stock at an exercise price of $2.00 per share (the "October 2025 Warrants"), which are exercisable immediately and will expire on thefive year anniversary of issuance. The net proceeds to the Company from the October 2025 Inducement were approximately $29.1 million, after deducting financial advisory fees and related transaction expenses.

On September 10, 2025, the Company entered into a Warrant Inducement Agreement (the “September 2025 Inducement”) with an institutional investor and holder of certain existing warrants to cash exercise warrants to purchase 19,685,040 shares of common stock, previously issued in January 2025 (the "January 2025 Warrants"), at the original issuance exercise price of $1.20 per share. In consideration of the investor’s agreement to exercise the January 2025 Warrants, the Company agreed to issue new warrants to the Investor to purchase up to 19,685,040 shares of common stock at an exercise price of $1.88 per share (the “September 2025 Warrants”), which are exercisable immediately and will expire on the five and one half anniversary of issuance. The net proceeds to the Company from the September 2025 Inducement were approximately $22.0 million, after deducting financial advisory fees and related transaction expenses.

On January 29, 2025, the Company consummated a registered direct offering (the "January 2025 Registered Direct Offering") with an institutional investor priced at-the-market under Nasdaq rules, pursuant to which the Company agreed to issue and sell 8,200,000 shares of common stock and 11,485,040 pre-funded warrants exercisable for shares of common stock, together with accompanying warrants to purchase up to 19,685,040 shares of common stock. Each share of common stock and accompanying common warrant were sold together at a combined offering price of $1.27, and each pre-funded warrant and accompanying common warrant were sold together at a combined offering price of $1.2699. The common warrants have an exercise price of $1.20 per share. The net proceeds to the Company from the January 2025 Registered Direct Offering were approximately $23.1 million, after deducting the placement agents' fees and related offering expenses.

During the nine months ended September 30, 2025,11.6 million warrants issued in connection with previous equity financings between 2022 and 2024 were exercised at an exercise price of $0.75 per share for aggregate proceeds of approximately $8.7 million.

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 September 30, 2025, 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. In December 2023, the Company commenced a binding arbitration proceeding against 3D Medicines, which involves, among other things, the trigger and payment of certain milestone payments due to the Company. See Note 5. Legal Proceedings.

As of September 30, 2025, the Company had cash and cash equivalents of approximately $44.3 million and restricted cash and cash equivalents of $0.1 million. In accordance with Accounting Standards Codification ("ASC") 205-40, Presentation of Financial Statements - Going Concern, the Company evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the consolidated financial statements are issued. The Company expects its cash and cash equivalents, together with the approximately $29.1 million in net proceeds from the October 2025 Inducement, will 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, although the Company may pursue additional capital resources through public or private equity or debt financings or by entering into additional license agreements or collaborations with other companies.

Management's expectations with respect to its ability to fund current planned operations is based on estimates that are subject to risks and uncertainties. If actual results are different from management's estimates, the Company may need to seek additional strategic or financing opportunities sooner than would otherwise be expected. There is no guarantee that any of these strategic or financing opportunities will be executed or executed on favorable terms, and some could be dilutive to existing stockholders. If the Company is unable to obtain additional funding on a timely basis, it may be forced to significantly curtail, delay, or discontinue one or more of its planned research and development programs or be unable to expand its operations or otherwise prepare for the potential regulatory approval and commercialization of its product candidates, assuming positive data.

Since inception, the Company has incurred recurring losses and negative cash flows from operations and, as of September 30, 2025, has an accumulated deficit of $267.3 million. During the nine months ended September 30, 2025, the Company incurred a net loss of $19.2 million, and used $23.5 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.

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 2024 Annual Report. The significant accounting policies summarized and included in the 2024 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, and Sellas Life Sciences Limited. 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 2024 Annual Report. The accompanying consolidated financial statements as of September 30, 2025 and for the three and nine months ended September 30, 2025 and 2024, 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, 2024 have been derived from the audited financial statements as of that date.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company's chief operating decision maker ("CODM") is the President & Chief Executive Officer.

The Company views its operations and manages its business asone operating segment, which includes all activities related to the development of novel therapeutics for a broad range of cancer indications. The determination of a single reportable segment is consistent with the consolidated financial information provided to the CODM. The CODM does not evaluate discrete financial information for each of the Company's clinical product candidates, and views and manages the Company's clinical programs as one consolidated segment for which all operations are centralized.

Segment profit or loss is measured as the Company's net loss as reported on the consolidated statement of operations. As the Company does not currently generate revenues, the CODM evaluates Company performance through the achievement of clinical development goals. The CODM also monitors the Company's cash and cash equivalents as reported on the consolidated balance sheet, net cash used in operations as reported on the consolidated statement of cash flows, and segment expense information in order to make operational decisions, allocate resources, and plan for future activities.

Segment expenses consist of the Company's functional expenses, research and development expenses and general and administrative expenses, as reported in the consolidated statement of operations. Other segment items included in the measure of segment net loss include non-operating income, which primarily relates to interest income. The measure of total segment assets is reported on the consolidated balance sheet as total assets.

The accounting policies of the Company's single reportable segment are the same as those for the consolidated financial statements described in this Note 3.

Fair Value of Financial Instruments

The Company measures certain financial assets and liabilities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value:

Level 1—Quoted prices in active markets for identical assets or liabilities.

Level 2—Inputs other than quoted prices included within Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

As of September 30, 2025 and December 31, 2024, the carrying amounts of the Company’s financial instruments, including cash equivalents and accounts payable, approximate fair value due to the short-term nature of those instruments and were categorized as Level 1. The Company did not transfer any financial instruments into or out of Level 3 classification during the nine months ended September 30, 2025 or 2024.

Net Loss Per Share

Net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during each period. The weighted average number of shares of common stock outstanding also includes pre-funded warrants and shares held in abeyance because their exercise requires only nominal consideration for the delivery of the shares. 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):

Income Taxes

On July 4, 2025, the U.S. enacted a budget reconciliation package commonly referred to as the One Big Beautiful Bill Act of 2025 ("OBBBA"), which contains a broad range of tax reform provisions affecting businesses, including the permanent reinstatement of bonus depreciation on qualified property and full expensing of domestic research and experimental expenditures. The Company is currently evaluating the impact of the legislation on our 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.

In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures, which requires disclosure of disaggregated information about certain income statement expense line items in the notes to the financial statements on an interim and annual basis. ASU 2024-03 will be effective for the annual reporting periods in fiscal years beginning after December 15, 2026, with early adoption permitted. The Company is currently evaluating the impact that the adoption of ASU 2024-03 will have on the consolidated financial statements, but does not expect a material impact upon adoption.

4. Balance Sheet Accounts

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

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

5. Commitments and Contingencies

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. The lease began on June 5, 2020, was amended in February 2022 to add additional space, and was set to expire on September 30, 2026 as of September 30, 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 September 30, 2025, the leases have a remaining term of 1.0 year.

Rent expense related to the Company's operating leases was approximately $0.1 million for each of the three months ended September 30, 2025 and 2024, and $0.4 million for each of the nine months ended September 30, 2025 and 2024.

The Company made cash payments related to its operating leases of approximately $0.2 million and $0.1 million for the three months ended September 30, 2025 and 2024, respectively, and $0.5 million and $0.4 million for the nine months ended September 30, 2025 and 2024, respectively.

Future minimum lease payments are as follows as of September 30, 2025 (in thousands):

On October 1, 2025, the Company entered into an amendment to its operating leases which provides for the extension of the expiration date byone year from September 30, 2026 to September 30, 2027 and approximately $0.6 million in additional future minimum lease payments.

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.

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 September 30, 2025, there was no pending or threatened litigation.

6. Stockholders’ Equity

Preferred Stock

The Company has authorized up to 5,000,000 shares of preferred stock, $0.0001 par value per share, for issuance. There wereno preferred shares outstanding as of September 30, 2025 and December 31, 2024.

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 September 30, 2025, the Company has shares of common stock reserved for future issuance as follows (in thousands):

7. 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 nine months ended September 30, 2025 (in thousands except per share data):

Upon closing of the October 2025 Warrant Inducement, the Company issued 13,363,714 shares of common stock to the holder, while the remaining shares were not issued and were held in abeyance until the Company receives notice from the holder that the remaining shares may be issued in compliance with the beneficial ownership limitation set forth in the October 2025 Warrant Inducement. Since the exercise price has been paid, the shares held in abeyance effectively become a "pre-funded warrant" until the holder notifies the Company that the issuance may occur without violation of the beneficial ownership limitation. In November 2025, the Company issued 4,000,000 shares of common stock to the holder that were held in abeyance at closing.

Warrants Classified as Equity

The warrants to acquire shares of common stock issued during the January 2025 Registered Direct 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.

The Company accounted for the September 2025 Inducement as an exercise of the January 2025 Warrants in exchange for the issuance of the September 2025 Warrants, which is a free-standing financial instrument recorded in stockholders' equity. Since the September 2025 Warrants were issued to incentivize the exercise of the January 2025 Warrants, incremental fair value of approximately $14.7 million as a result of the inducement was accounted for as a non-cash equity issuance cost recognized in stockholders' equity. The incremental value was obtained from the revaluation of the January 2025 Warrants pre and post inducement exchange using a Black-Scholes option pricing model. However, there is no net impact to the consolidated statements of stockholders' equity because the warrants are equity classified.

The fair value of the September 2025 Warrants was estimated at approximately $30.4 million using a Black-Scholes option pricing model which takes into account the estimated remaining term of the warrants of five and one half years, the historical volatility of the Company's common stock commensurate with the expected term estimated at 114.20%, a risk-free interest rate of 3.67% based on the U.S. Treasury yield commensurate with the expected term, andno future dividends based on the Company's history and expectations.

8. 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 Topic 606, Revenue From Contracts with Customers, 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 September 30, 2025, 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 wasno licensing revenue recognized during the three and nine months ended September 30, 2025 and 2024. There wasno cost of licensing revenue recognized during the three and nine months ended September 30, 2025 and 2024.

9. 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 17,000 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 Equity Incentive Plan ("2019 Equity 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 Plan was approved by the stockholders of the Company. On June 20, 2023, an amendment to the 2019 Equity Plan was approved by the 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 September 30, 2025, approximately 1,356,000 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 and nine months ended September 30, 2025 and 2024, respectively (in thousands):

Options to Purchase Shares of Common Stock

The following table summarizes stock option activity of the Company for the nine months ended September 30, 2025:

The aggregate intrinsic values of outstanding and exercisable stock options at September 30, 2025 were calculated based on the closing price of the Company’s common stock as reported on The Nasdaq Capital Market on September 30, 2025 of $1.61 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 and nine months ended September 30, 2025 and 2024, respectively, were as follows:

There wereno options granted during each of the three months ended September 30, 2025 and 2024. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2025 and 2024 was $0.85 and $0.48, 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 term assumptions for employee grants were based upon the simplified method, which averages the contractual term of the Company’s options often years with the average vesting term offour years for an average of approximatelysix years. The expected life assumptions for non-employees were based upon the contractual term of the option. The dividend yield assumption iszero 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 September 30, 2025, there was $1.2 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 2.1 years.

Time-vested RSUs and RSUs with Performance Conditions

The following table summarizes RSU activity of the Company for the nine months ended September 30, 2025:

As of September 30, 2025, there was $1.2 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 nine months ended September 30, 2025.

Amended and Restated 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 eachsix-month offering period during the term of the 2021 ESPP.

On June 17, 2025, an amendment to the 2021 ESPP was approved by the stockholders of the Company, which amended and restated the 2021 ESPP (as amended and restated, the "Amended and Restated 2021 ESPP") to increase the number of shares of common stock available for sale under the 2021 ESPP by 800,000.

During the nine months ended September 30, 2025,115,449 shares of common stock were purchased by employees under the Amended and Restated 2021 ESPP for proceeds of approximately $0.1 million. There are currently 764,155 shares of common stock reserved for issuance under the Amended and Restated 2021 ESPP as of September 30, 2025.

10. Subsequent Events

The Company evaluated all events or transactions that occurred after September 30, 2025 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.

This management’s discussion and analysis of financial condition as of September 30, 2025 and results of operations for the three and nine months ended September 30, 2025 and 2024, 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, 2024, as filed with the Securities and Exchange Commission, or SEC, on March 20, 2025, or our 2024 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 (tambiciclib), 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.

We have an ongoing 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 trial outcome and agreement with the U.S. Food and Drug Administration, or the FDA. The primary endpoint of the REGAL study is overall survival, or OS. In March 2024, we announced the completion of enrollment of 126 patients at clinical sites in the U.S., Europe, and Asia with a planned interim safety, efficacy and futility analysis after 60 events (deaths). Study sites in the U.S. and Europe account for approximately 75% of patients enrolled, with the U.S.-based sites representing the highest enrolling country. In December 2024, we announced that the pre-specified threshold of 60 events (deaths) per the protocol had been reached, triggering the interim analysis to be conducted by the Independent Data Monitoring Committee, or IDMC. In January 2025, we announced that the IDMC had completed pre-specified interim analysis of the REGAL study and had recommended that the study continue without modifications. In August 2025, we announced the completion of a periodic review by the IDMC and positive recommendation to continue the REGAL study without modification. The final analysis will be conducted once 80 events (deaths) are reached. We anticipate that 80 events will be reached this year. Because the final analysis is event driven, it is difficult to predict with any certainty and it may occur at a different time than currently expected.

In December 2020, we entered into an exclusive license agreement, or the 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 our 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 refer to as Greater China. 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 15, 2025, 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 announced that we had commenced a binding arbitration proceeding against 3D Medicines to resolve a dispute regarding, among other things, the trigger and payment of relevant milestone payments due to us under the 3D Medicines Agreement. See Part II, Item 1., Legal Proceedings.

GPS was granted Orphan Drug Designations, or ODD, from the FDA, as well as orphan medicines designations from the European Medicines Agency, or EMA, in AML, malignant pleural mesothelioma, or MPM, and multiple myeloma, or MM, as well as Fast Track designations for AML, MPM, and MM from the FDA. In October 2024, the FDA granted Rare Pediatric Disease, or RPD, designation to GPS for the treatment of pediatric AML.

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 OS 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 once weekly for AML and 100 mg once weekly 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 efficacy endpoints are complete response composite rate and duration of response. Additional endpoints include event free survival, OS, 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. At that time, 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 was planned to enroll five to 10 patients. During the trial we identified 30 mg fixed twice weekly as our optimal dose level.

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, or AML MR, as defined by the World Health Organization, and among AML MR patients, patients with the ASXL1 gene mutation accounted for the most responders across all dose cohorts. We 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 at the optimal dose level of 30 mg fixed twice weekly. In December 2024, we announced positive data from the first 3 cohorts in the Phase 2a trial.

In July 2025, we announced that the Phase 2 trial of SLS009 in r/r AML met all primary endpoints and received FDA guidance to advance our first-line therapy study. The overall response rate, or ORR, in 54 evaluable patients was 33% across all cohorts and dose levels, 40% for the 30 mg BIW dose level, and 44% in the 30 mg BIW dose among AML MR patients, all exceeding the pre-specified ORR threshold of 20%. The highest efficacy was observed among patients with ASXL1 mutations, with an ORR of 50% (9/18) at 30 mg BIW dose levels, and AML

MR with Myelomonocytic/Myelomonoblastic, or M4/M5, patients with an ORR of 50% (6/12). The median overall survival, or mOS, reached 8.9 months in patients with AML MR and 8.8 months in patients r/r to venetoclax-based regimens at a 30 mg BIW dose level, surpassing the historical benchmark of ~2.4 months. SLS009 was well-tolerated with no new safety signals observed. No dose-limiting toxicities were observed across all dose levels.

In addition, following a productive end of Phase 2 meeting, the FDA recommended that we proceed into a trial to include newly diagnosed, first-line AML patients eligible for aza/ven therapy, where the FDA noted clinical benefit might be greatest. The randomized 80-patient trial is currently in preparation and expected to begin enrollment by the first quarter of 2026. The trial will include two groups: predictive biomarker cohort (newly diagnosed patients unlikely to benefit from standard aza/ven therapy based on molecular profiling) and early venetoclax resistance cohort (patients who initiate treatment with aza/ven, but demonstrate confirmed lack of any response after two treatment cycles).

In November 2024, we announced data from preclinical studies identifying ASXL1 mutation as key predictor of SLS009 in response to solid cancers. 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.

In May 2025, we announced data for pediatric acute lymphoblastic leukemia, or ALL, patients derived xenografts, or PDX. The experiment conducted and funded by the National Institute of Health, or NIH, through PIVOT program included 27 patient-derived ALL tumors from pediatric patients. Tumors were xenografted in mice in two groups, vehicle control arm and SLS009 arm. Mice were treated with a fractionated dose once per week for six consecutive weeks. Treatment was well tolerated. For all models, median survival was approximately tripled in the SLS009 arm, compared to vehicle control arm. SLS009 demonstrated delayed progression in 25/27 (93%) models and more than two times longer time to progression in 15/27 (56%) of ALL models. In addition, there were complete responses, or CR, in two models and in one of the two models CR was maintained after the treatment had been completed until the end of the study (four months). Among seven KMT2A rearranged models, time to progression was extended in all seven models, and in six out of seven (86%) time to progression was more than doubled.

For SLS009, the FDA granted ODD designations in AML and peripheral T-cell lymphoma, or PTCL, and Fast Track designations for r/r AML and r/r PTCL. The FDA granted RPD designation to SLS009 for the treatment of pediatric ALL in June 2024 and the FDA granted RPD designation to SLS009 for the treatment of pediatric AML in July 2024. Also, the EMA granted ODD for SLS009 in AML and in PTCL in June 2024 and July 2024, respectively.

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, 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. We expect professional fees to increase in the foreseeable future as we prepare for potential commercialization of our product candidates and continue to build our corporate infrastructure.

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 interest income. Interest income primarily reflects interest earned from our cash and cash equivalents.

Critical Accounting Policies and Estimates

In the 2024 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, 2024 that are not included in Note 3 of the accompanying consolidated financial statements for the three and nine months ended September 30, 2025. Readers are encouraged to read the 2024 Annual Report in conjunction with this Quarterly Report on Form 10-Q.