SELLAS Life Sciences Provides Update on Pivotal Phase 3 REGAL Trial of Galinpepimut-S (GPS) in Acute Myeloid Leukemia (AML)

Rhea-AI Summary

SELLAS Life Sciences (NASDAQ: SLS) provided an update on the pivotal Phase 3 REGAL trial of galinpepimut-S (GPS) in acute myeloid leukemia (AML) on Dec 29, 2025. The contract research organization reported 72 pooled events (deaths) as of Dec 26, 2025; the trial requires 80 events to trigger the event-driven final overall survival analysis. SELLAS remains fully blinded to efficacy and survival data and says this aggregate update does not affect planned statistical analyses. The company will announce when the 80th event occurs.

Additional context: the Independent Data Monitoring Committee previously recommended continuing the trial without modification.

Positive

• 72 of 80 events recorded as of Dec 26, 2025
• IDMC recommended continuing the REGAL trial in Aug 2025
• Study remains fully blinded, preserving analysis integrity

Negative

• 80th event has not occurred, delaying final analysis timing
• Longer-than-expected survival may extend time to final overall survival readout

Key Figures

Events occurred 72 deaths REGAL Phase 3 GPS AML trial as of Dec 26, 2025

Final analysis trigger 80 deaths Pre-specified overall survival endpoint in REGAL Phase 3 trial

Expected median OS around eight months Typical outcome for non-transplant AML patients on hypomethylating agent and/or BCL-2 inhibitor

REGAL enrollment 126 patients Completed enrollment in April 2024 per prior IDMC update

Share price $2.87 Price before REGAL event-count update, up 1.06% over 24h

52-week range $0.8505 – $3.01 Shares trade 4.65% below 52-week high, well above low

Cash & equivalents $44.3M Balance as of Sept 30, 2025 from Q3 10-Q

Net loss Q3 2025 $6.8M Quarter ended Sept 30, 2025 per 10-Q filing

Market Reality Check

$2.87 Last Close

Volume Volume 4,342,344 shares is below the 20-day average of 6,192,871, with relative volume at 0.7. normal

Technical Shares trade above the 200-day MA, with price at $2.87 versus MA(200) at $1.69.

Peers on Argus

SLS is up 1.06% while close biotech peers show mixed action, with several (e.g., TLSA, CGTX, TRDA) down and TNYA modestly up, pointing to a stock-specific move rather than a broad sector trend.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Dec 07	Phase 2 data update	Positive	+4.6%	Reported favorable SLS009 Phase 2 efficacy and survival data in AML-MR.
Nov 12	Earnings and pipeline	Neutral	-1.3%	Q3 2025 results alongside REGAL timeline and SLS009 development plans.
Nov 03	Clinical presentation notice	Neutral	-1.6%	Announcement of upcoming SLS009 Phase 2 data presentation at ASH 2025.
Oct 27	Warrant inducement deal	Negative	-2.5%	Existing warrants exercised with new warrants issued, increasing potential share supply.
Oct 22	Conference participation	Positive	+2.1%	Participation in the J.P. Morgan U.S. Opportunities Forum with investor meetings.

Pattern Detected

Clinical and corporate updates have produced mixed but often modest price reactions, with generally aligned direction when news is clearly positive or negative.

Recent Company History

Over the last few months, SELLAS has advanced both GPS and SLS009 in AML. A positive Phase 2 SLS009 update on Dec 7, 2025 coincided with a 4.6% gain, while prior SLS009 data announcements and conference disclosures had small negative or modest positive moves. Financing via warrant exercises in late October led to a -2.51% reaction, and Q3 results plus pipeline updates on Nov 12 saw a slight decline. Today’s REGAL event-count update fits into this sequence of incremental, trial-driven milestones.

Regulatory & Risk Context

Active S-3 Shelf Registration 2025-10-10

An effective Form S-3 shelf filed on Oct 10, 2025 registers specific blocks of common stock and warrant-related shares for resale. The shelf has already supported at least one usage via a 424B5 prospectus supplement on Oct 27, 2025, indicating an established pathway for secondary share resales that can affect tradable supply over time.

Market Pulse Summary

The stock is surging +12.2% following this news. A strong positive reaction aligns with the pattern of modestly favorable responses to prior clinical updates, where average moves around similar news were about 2.71%. The REGAL update signals progress toward the pre-planned 80-event overall survival readout without changing trial design. However, investors have also absorbed recent financing and warrant activity and an effective S-3 shelf that allows registered resales, factors that can temper or later reverse sharp upside moves.

Key Terms

overall survival medical

"The REGAL trial is an overall survival study, and per the statistical analysis plan"

Overall survival is the average or median length of time patients remain alive after starting a treatment or entering a clinical study, measured regardless of cause of death. Investors care because it is a clear, hard measure of a therapy’s real-world benefit — like timing how long a new battery actually runs — and strong improvements in overall survival can drive regulatory approval, market adoption and revenue potential.

independent data monitoring committee medical

"Following the Independent Data Monitoring Committee (IDMC) recommendation in August 2025"

A panel of independent medical, statistical and ethical experts who review ongoing clinical trial data to judge participant safety, study integrity and whether the trial should continue, change or stop. Like impartial referees or safety inspectors, their decisions can speed, delay or halt a drug’s development and therefore materially affect a company’s timelines, regulatory chances and investment risk.

contract research organization technical

"Contract Research Organization for the REGAL trial has informed the Company"

A contract research organization (CRO) is an outside company hired to run medical and scientific work for drug, device or biotech developers—like an experienced project manager and lab team that companies rent instead of building in-house. Investors care because CROs influence development speed, quality and cost: delays or successes in trials affect client spending, regulatory risk and ultimately revenues for both the sponsor and the CRO.

bcl-2 inhibitor medical

"a combination of hypomethylating agents and/or a BCL-2 inhibitor, with an expected median"

A Bcl-2 inhibitor is a drug that blocks the Bcl-2 protein, which acts like a survival switch inside cells and helps certain cancer cells avoid natural self-destruction. For investors, these drugs matter because successful inhibitors can shrink tumors and become valuable treatments, but they also carry binary risks—trial results, safety issues, and regulatory approval determine commercial value and competitive positioning much like a single safety test deciding whether a new product reaches market.

median overall survival medical

"with an expected median overall survival of around eight months."

Median overall survival is the middle point of how long patients live after starting treatment, meaning half live longer and half live shorter. It helps doctors understand how effective a treatment is and gives patients an idea of what to expect about their future.

phase 3 medical

"update on the ongoing Phase 3 REGAL trial evaluating GPS as a potential maintenance"

Phase 3 is the late-stage clinical testing step for a new drug or medical treatment, where the product is given to large groups of patients to confirm effectiveness, monitor side effects, and compare it to standard care. Successful Phase 3 results are often the final scientific hurdle before regulators decide on approval and market launch—like passing a final exam before graduation—and can sharply change a company's valuation and future revenue prospects.

maintenance therapy medical

"evaluating GPS as a potential maintenance therapy in patients with AML after second"

Treatment given after an initial successful response to control a chronic or recurring disease and prevent it from returning or worsening; it often involves lower-intensity, ongoing medication or interventions rather than aggressive cures. For investors, maintenance therapy matters because it can create steady, long-term demand for drugs or services, similar to a subscription that generates predictable revenue and extends a product’s commercial life beyond the initial treatment period.

AI-generated analysis. Not financial advice.

• Contract Research Organization for the REGAL trial has informed the Company that 72 events have occurred in the trial as of December 26, 2025; SELLAS remains blinded to trial outcomes
  
• Timing of the final analysis is event-driven, and SELLAS will announce the occurrence of the 80^th event
  

NEW YORK, Dec. 29, 2025 (GLOBE NEWSWIRE) -- SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) (“SELLAS’’ or the “Company”), a late-stage clinical biopharmaceutical company focused on the development of novel therapies for a broad range of cancer indications, today provided an update on the ongoing Phase 3 REGAL trial evaluating GPS as a potential maintenance therapy in patients with AML after second complete remission (CR2).

Following the Independent Data Monitoring Committee (IDMC) recommendation in August 2025 that the Phase 3 REGAL trial continue without modification, it was expected that the 80^th event (death) required to trigger the final analysis would occur before year-end. The REGAL trial is an overall survival study, and per the statistical analysis plan, the final analysis will be triggered once 80 events (deaths) have occurred.

SELLAS was informed by its contract research organization managing the REGAL trial that the pooled number of events was 72 as of December 26, 2025. SELLAS remains 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, and the timing of studies with overall survival as an endpoint can vary, SELLAS will announce the 80^th event when it occurs.

“We appreciate the continued dedication of the patients, families, and investigators participating in the pivotal Phase 3 REGAL trial where survival times, fortunately for patients and caregivers, appear longer than expected,” said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. “While the 80^th event has not yet occurred, and we remain fully blinded, every passing month may increase the probability of a successful study as highlighted by key opinion leaders in our recent R&D event. Conclusive data will follow the unblinding and analyses of the study results. We remain steadfast in our commitment to advancing breakthrough therapies, such as GPS, that possess the potential to significantly improve the lives of patients with AML.”

“The REGAL study represents a meaningful effort to evaluate GPS as a novel therapeutic approach in an AML population with significant unmet need,” said Dr. Yair Levy, Director of Hematologic Malignancies Research at Texas Oncology Baylor University Medical Center, and a member of the REGAL Steering Committee. “For patients who are unable to undergo transplant, as in the REGAL study, their treatment usually consists of a combination of hypomethylating agents and/or a BCL-2 inhibitor, with an expected median overall survival of around eight months. We hope to see an extended survival benefit, with a tolerable safety profile, as observed in previous GPS studies.”

SELLAS Life Sciences Virtual R&D Day – October 29, 2025: Advancing Novel Therapies in Acute Myeloid Leukemia (AML): An Overview of the Ongoing Phase 3 REGAL Trial of Galinpepimut-S (GPS) and SLS009 Program Update. To access a replay of the R&D Day, please click here.

About Phase 3 REGAL Trial

REGAL (NCT04229979) is a Phase 3 randomized registrational clinical trial for GPS in AML patients who have achieved complete remission following second-line salvage therapy (CR2 patients). The primary endpoint is overall survival. The IDMC is an independent group of medical, scientific, and biostatistics experts who are responsible for reviewing and evaluating patient safety and efficacy data for REGAL, and for monitoring quality and overall conduct to ensure the validity, scientific and clinical merits of the study. The IDMC charter provides for periodic reviews of safety, efficacy, and futility in addition to the interim and final analyses.

About SELLAS Life Sciences Group, Inc.

SELLAS is a late-stage clinical biopharmaceutical company focused on the development of novel therapeutics for a broad range of cancer indications. SELLAS’ lead product candidate, GPS, is licensed from Memorial Sloan Kettering Cancer Center and targets the WT1 protein, which is present in an array of tumor types. GPS has the potential as a monotherapy and combination with other therapies to address a broad spectrum of hematologic malignancies and solid tumor indications. The Company is also developing SLS009 (tambiciclib) - potentially the first and best-in-class differentiated small molecule CDK9 inhibitor with reduced toxicity and increased potency compared to other CDK9 inhibitors. Data suggests that SLS009 demonstrated a high response rate in AML patients with unfavorable prognostic factors including ASXL1 mutation, commonly associated with poor prognosis in various myeloid diseases. For more information on SELLAS, please visit www.sellaslifesciences.com.

Forward-Looking Statements

This press release contains forward-looking statements. All statements other than statements of historical facts are “forward-looking statements,” including those relating to future events. In some cases, forward-looking statements can be identified by terminology such as “plan,” “expect,” “anticipate,” “may,” “might,” “will,” “should,” “project,” “believe,” “estimate,” “predict,” “potential,” “intend,” or “continue” and other words or terms of similar meaning. These statements include, without limitation, statements related to the GPS clinical development program, including the REGAL study and the timing of future milestones related thereto. These forward-looking statements are based on current plans, objectives, estimates, expectations, and intentions, and inherently involve significant risks and uncertainties. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks and uncertainties with oncology product development and clinical success thereof, the uncertainty of regulatory approval, and other risks and uncertainties affecting SELLAS and its development programs as set forth under the caption “Risk Factors” in SELLAS’ Annual Report on Form 10-K filed on March 20, 2025 and in its other SEC filings. Other risks and uncertainties of which SELLAS is not currently aware may also affect SELLAS’ forward-looking statements and may cause actual results and the timing of events to differ materially from those anticipated. The forward-looking statements herein are made only as of the date hereof. SELLAS undertakes no obligation to update or supplement any forward-looking statements to reflect actual results, new information, future events, changes in its expectations, or other circumstances that exist after the date as of which the forward-looking statements were made.

Investor Contact

John Fraunces

Managing Director

LifeSci Advisors, LLC

jfraunces@lifesciadvisors.com

FAQ

How many events have occurred in the REGAL trial of GPS (SLS) as of Dec 26, 2025?

The contract research organization reported 72 pooled events as of Dec 26, 2025.

What event count will trigger the final analysis for SELLAS's REGAL trial (SLS)?

The final overall survival analysis is event-driven and will be triggered at 80 events (deaths).

Has SELLAS (SLS) unblinded REGAL trial efficacy or survival data on Dec 29, 2025?

No; SELLAS states it remains fully blinded to all efficacy and survival outcomes.

Did an independent committee recommend changes to the REGAL trial for SLS?

No; the Independent Data Monitoring Committee recommended in August 2025 that the trial continue without modification.

When will SELLAS (SLS) announce the REGAL final analysis date?

SELLAS will announce the occurrence of the 80th event, which triggers the final analysis, when it occurs.

What median overall survival did a REGAL steering committee member reference for non-transplant AML patients?

A committee member referenced an expected median overall survival of around eight months for non-transplant AML patients on standard therapy.