SELLAS Life Sciences Group, Inc.

Previous wording

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. 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. 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. The next and 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.

Current wording

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. 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. 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. The next and final analysis will be conducted once 80 events (deaths) are reached. In December 2025, we announced that our contract research organization informed us that the pooled number of events was 72 as of December 26, 2025. We remain blinded to all efficacy and survival data outcomes and, as no outcomes analyses were performed and no statistical penalty has been incurred, this one-time update on the aggregate number of events does not impact future statistical analyses. 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. We will announce the 80th event when it occurs.

Previous wording

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 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 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 our license agreement with 3D Medicines, or 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.

Current wording

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 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 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 December 31, 2025, we have received an aggregate of $10.5 million in upfront and milestone payments under our license agreement with 3D Medicines, or 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 Item 3. Legal Proceedings.

Previous wording

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.

Current wording

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 or 30 mg twice weekly for AML and 100 mg once weekly for lymphomas.

Previous wording

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, overall survival, and pharmacokinetic and pharmacodynamic assessments.

Current wording

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 December 2024, we announced positive data from the first 3 cohorts in the Phase 2a trial.

Previous wording

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. We expect to report relevant data from the program in the first half of 2025.

Current wording

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

Previous wording

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

Current wording

Non-operating income consists of interest income. Interest income primarily reflects interest earned from our cash and cash equivalents.

Previous wording

Research and development expenses were $19.1 million for the year ended December 31, 2024 compared to $24.0 million for the year ended December 31, 2023. The following table summarizes our research and development expenses for the years ended December 31, 2024 and 2023 (amounts in thousands):

Current wording

Research and development expenses were $16.0 million for the year ended December 31, 2025 compared to $19.1 million for the year ended December 31, 2024. The following table summarizes our research and development expenses for the years ended December 31, 2025 and 2024 (amounts in thousands):

Previous wording

The decrease in research and development expenses of approximately $4.9 million was primarily attributable to the following:

Current wording

The decrease in research and development expenses of approximately $3.1 million was primarily attributable to the following:

Previous wording

•$1.5 million of decreased manufacturing costs and clinical drug supply purchases primarily driven by the completion of enrollment in the REGAL study in the first quarter of 2024;

Current wording

•$2.4 million of decreased external clinical trial expenses related to GPS primarily driven by the completion of enrollment in the REGAL study in the first quarter of 2024;

Previous wording

•$0.6 million of decreased external clinical trial expenses primarily driven by the completion of enrollment in REGAL.

Current wording

•$1.0 million of decreased external clinical trial expenses related to SLS009 primarily driven by the completion of enrollment in our Phase 2a trial in the current period;

Previous wording

•$2.2 million of decreased clinical and regulatory consultant costs primarily driven by the completion of enrollment in the REGAL study in the first quarter of 2024;

Current wording

•$0.5 million of decreased clinical consulting costs driven by the completion of enrollment in the REGAL study in the first quarter of 2024; partially offset by

Previous wording

We anticipate that our research and development expenses will increase in the future as we continue to advance the development of GPS and SLS009.

Current wording

We anticipate that our research and development expenses will increase in the future as we continue to prepare for a potential BLA filing for GPS following the upcoming final analysis of the REGAL study and proceed into a randomized Phase 2 clinical trial to include newly diagnosed, front-line AML patients for SLS009.

Previous wording

General and administrative expenses were $12.4 million for the year ended December 31, 2024 compared to $13.9 million for the year ended December 31, 2023. The $1.5 million decrease was primarily attributable to a $1.5 million decrease in employee related expenses, including a $0.5 million decrease in non-cash stock-based compensation, primarily due to a decrease in headcount, a $0.7 million decrease in outside services and public company costs, and a $0.6 million decrease in insurance premiums, which were partially offset by the initial recognition of a $1.1 million one-time severance charge during the current period and a $0.2 million increase in legal fees.

Current wording

General and administrative expenses were $12.3 million for the year ended December 31, 2025 compared to $12.4 million for the year ended December 31, 2024. The $0.1 million decrease was primarily attributable to a $0.8 million decrease in employee related expenses which was driven by the recognition of a $1.1 million one-time severance charge in the prior period partially offset by a $0.3 million increase in non-cash stock-based compensation and a $0.7 million increase in legal fees.

Previous wording

On January 29, 2025, we consummated a registered direct offering with an institutional investor priced at-the-market under Nasdaq rules, or the January 2025 Registered Direct Offering, pursuant to which we 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 us from the January 2025 Registered Direct Offering were approximately $23.1 million, after deducting the placement agents' fees and related offering expenses.

Current wording

On January 29, 2025, we consummated a registered direct offering, or the January 2025 Registered Direct Offering, with an institutional investor priced at-the-market under Nasdaq rules, pursuant to which we 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 us from the January 2025 Registered Direct Offering were approximately $23.1 million, after deducting the placement agents' fees and related offering expenses.

Previous wording

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 December 31, 2024, which milestones are all variable in nature and not under our control. In December 2023, we commenced a binding arbitration proceeding against 3D Medicines, which involves, among other things, the trigger and payment of certain milestone payments due to us. See Part I, Item 3. Legal Proceedings.

Current wording

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. As of December 31, 2025, 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 December 31, 2025, which milestones are all variable in nature and not under our control. In December 2023, we commenced a binding arbitration proceeding against 3D Medicines, which involves, among other things, the trigger and payment of certain milestone payments due to us. See Part I, Item 3. Legal Proceedings.

Previous wording

As of December 31, 2024, we had an accumulated deficit of $248.1 million, cash and cash equivalents of $13.9 million and restricted cash and cash equivalents of $0.1 million. In addition, we had current liabilities of $9.5 million as of December 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.

Current wording

As of December 31, 2025, we had an accumulated deficit of $275.0 million, cash and cash equivalents of $71.8 million and restricted cash and cash equivalents of $0.1 million. In addition, we had current liabilities of $7.0 million as of December 31, 2025. We expect that our cash and cash equivalents, together with the $42.6 million in proceeds from warrant exercises received subsequent to December 31, 2025, will be sufficient to fund our current planned operations for at least the next twelve months from the date of issuance of these financial statements, although we 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.

Previous wording

Net cash used in operating activities of $31.4 million during the year ended December 31, 2023 was primarily attributable to our net loss of $37.3 million, and partially offset by a change in our operating assets and liabilities of $3.3 million and various net non-cash charges of $2.6 million. The net change in our operating assets and liabilities is due to an increase in accounts payable of $2.3 million, an increase in accrued expenses and other current liabilities of $1.4 million, and a decrease in prepaid expenses and other assets of $0.1 million, which was partially offset by a decrease in operating lease liabilities of $0.5 million. Net non-cash charges were driven by $2.1 million in non-cash stock compensation expense and $0.5 million in non-cash lease expense.

Current wording

Net cash used in operating activities of $28.4 million during the year ended December 31, 2025 was primarily attributable to our net loss of $26.9 million and a $4.1 million change in our operating assets and liabilities, partially offset by non-cash charges of $2.6 million. The net change in our operating assets and liabilities is due to a decrease in accounts payable and accrued expenses and other current liabilities of approximately $2.5 million, an increase in prepaid expenses and other assets of approximately $1.0 million, and a decrease in operating lease liabilities of approximately $0.6 million. Non-cash charges were driven by approximately $2.0 million in non-cash stock-based compensation expense and $0.6 million in non-cash lease expense.

Previous wording

We generated $22.3 million of net cash from financing activities during the year ended December 31, 2023, which was due to $21.9 million in aggregate net proceeds received from the February 2023 Offering, $0.3 million in aggregate net proceeds received from the issuance of common stock under a Controlled Equity Offering SM Sales Agreement with Cantor Fitzgerald & Co., or the Sales Agreement, and $0.1 million in aggregate net proceeds received from the issuance of common stock under our employee stock purchase plan. In January 2024, we mutually agreed with Cantor Fitzgerald & Co. to terminate the Sales Agreement.

Current wording

We generated $86.3 million of net cash from financing activities for the year ended December 31, 2025, which was due to $51.0 million in aggregate net proceeds received from the September 2025 Warrant Inducement and October 2025 Warrant Inducement, $23.1 million in net proceeds received from the January 2025 Registered Direct Offering, $12.6 million in proceeds received from the exercise of warrants, and $0.1 million in proceeds received from the issuance of common stock under our employee stock purchase plan, partially offset by $0.5 million to satisfy tax withholding on vesting of restricted stock units.

Previous wording

We base our expenses related to clinical trials on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple research institutions and CROs that conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or prepaid accordingly. Although we do not expect its estimates to be materially different from amounts actually incurred, our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in reporting amounts that are too high or too low in any particular period. To date, we have not made any material adjustments to our prior estimates of accrued research and development expenses.

Current wording

We base our expenses related to clinical trials on our estimates of the services received and efforts expended pursuant to quotes and contracts with multiple research institutions and CROs that conduct and manage preclinical studies and clinical trials on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, we adjust the accrual or prepaid accordingly.