SELLAS Life Sciences Reaches 80th Event in Phase 3 REGAL Trial of Galinpepimut-S (GPS) in Acute Myeloid Leukemia

Preliminary topline primary endpoint results are planned this quarter after database lock, unblinding and statistical analysis.

Rhea-AI Summary

SELLAS Life Sciences Group (NASDAQ: SLS) has reached the pre-specified 80th event in its Phase 3 REGAL trial, triggering final analysis.

REGAL evaluates galinpepimut-S (GPS) in patients with acute myeloid leukemia (AML). The study measures overall survival and is event-driven: the 80th event represents the 80th death counted toward its pre-specified analysis threshold. SELLAS will now proceed with database lock, which finalizes the study dataset, unblinding of the study data, and statistical analysis of the primary endpoint.

The company plans to announce preliminary topline primary endpoint results this quarter after completing the analysis, in accordance with the study’s pre-specified statistical analysis plan. The announcement marks the start of final analysis, rather than a report of the trial’s efficacy results.

2 points · 0 major

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0 major · 0 points

Hollow bars mark forward-looking points. How the balance works

Positive

• Moderate pointREGAL reached its pre-specified 80th event, triggering final analysis of the Phase 3 trial.
• Minor point. Forward-looking: it has not happened yet and may not happen.SELLAS plans to report preliminary topline primary endpoint results this quarter after completing the analysis.

Negative

• None.

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Key Figures

Final-analysis trigger: 80 events (deaths) Topline results timing: This quarter

Final-analysis trigger

80 events (deaths)

Phase 3 REGAL trial; trigger reached

Topline results timing

This quarter

Preliminary topline primary endpoint results

Previous Clinical trial Reports

2 past events · Latest: Dec 29

Same Type 2 events

1. Dec 29

   REGAL trial update

   24h Move

   +16.7%

   Reported 72 pooled death events; 80 were required to trigger final overall-survival analysis.

2. Aug 07

   Trial monitoring review

   24h Move

   +0.6%

   The monitoring committee recommended continuing the same Phase 3 REGAL trial without modification.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

overall survival, database lock, unblinding, primary endpoint, +1 more

5 terms

overall survival medical

"The REGAL trial is an event-driven overall survival study"

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.

database lock technical

"SELLAS will proceed with database lock, unblinding of the study data"

A database lock is the point in a clinical trial when the collected study data are finalized and no further changes or corrections are allowed, so analysts can run the official statistical tests. For investors this matters because it usually precedes public results or regulatory filings—think of it like sealing and signing off an exam before grading: once locked, the timing and content of the readout become clearer and uncertainty about last-minute data edits is reduced.

unblinding technical

"proceed with database lock, unblinding of the study data"

Unblinding is the process of revealing which study participants received the active treatment and which received placebo or comparator in a clinical trial. Like opening the answer key after a test, it converts blinded data into labeled results so researchers, regulators and sponsors can interpret safety and efficacy findings. For investors, unblinding matters because it can change how trial outcomes are viewed, affect regulatory decisions and influence company valuation and timelines.

primary endpoint medical

"the preliminary topline primary endpoint results from the trial"

The primary endpoint is the single main result a clinical study is designed to measure to decide if a treatment works, like the finish line in a race that tells you who won. Investors care because meeting or missing this goal drives regulatory decisions, future sales expectations and stock value — it turns trial data into a clear yes-or-no signal about a drug’s commercial prospects.

statistical analysis plan technical

"in accordance with the study’s pre-specified statistical analysis plan"

A statistical analysis plan is a detailed written blueprint that explains exactly how study data will be measured, compared and reported, including which outcomes will be examined, which calculations will be used, and how missing or messy data will be handled. For investors it matters because a clear, pre‑set plan reduces the risk of biased or surprising results—think of it as a recipe that ensures reported findings are reproducible and trustworthy for judging a drug or product’s prospects.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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- Reaching the Pre-Specified 80^th Event Triggers the Final Analysis of the Pivotal Phase 3 Trial -

- Company to Report Topline Primary Endpoint Results this Quarter -

NEW YORK, Oct. 28, 2026 (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 announced that the pivotal Phase 3 REGAL trial evaluating galinpepimut-S (GPS) in patients with acute myeloid leukemia (AML) has reached the pre-specified 80^th event (number of deaths), triggering the final analysis of the study.

The REGAL trial is an event-driven overall survival study, and with the occurrence of the 80^th event, SELLAS will proceed with database lock, unblinding of the study data, and statistical analysis of the primary endpoint data. Upon completion of this analysis, the Company will announce this quarter the preliminary topline primary endpoint results from the trial in accordance with the study’s pre-specified statistical analysis plan (SAP).

“Reaching the 80^th event represents a critical milestone in the REGAL trial,” said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. “AML remains an area of significant unmet need, particularly for patients in second complete remission with limited treatment options. With this pivotal study now advancing to final analysis, we look forward to evaluating the data, as positive results could position GPS as the first- and best-in-class novel immunotherapeutic option for these patients. On behalf of everyone at SELLAS, my sincerest appreciation goes out to all the physicians, nurses, study teams and, importantly, the participating patients and their families for their immense contributions in advancing the REGAL study. Our commitment to delivering hope to the AML community has never been stronger.”

About Phase 3 REGAL Trial

The Phase 3 REGAL trial (NCT04229979) is a randomized registrational clinical trial evaluating GPS as a potential maintenance therapy in AML patients who have achieved a second complete remission (CR2). The primary endpoint of the study is overall survival with secondary endpoints including leukemia-free survival and other clinical outcomes.

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 and SLS009 clinical development programs, 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 19, 2026 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

Media Contact

Joan Bosisio
VP, Scientific & Medical Communications
Simpson Healthcare
jbosisio@simpsonhealthcare.com

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does the 80th event mean for SELLAS’s Phase 3 REGAL trial?

The 80th event is the pre-specified number of deaths that triggers final analysis of REGAL, an overall survival study. SELLAS will proceed with database lock, unblinding of the study data, and statistical analysis of the primary endpoint.

When will SELLAS report Phase 3 REGAL trial results?

SELLAS plans to announce preliminary topline primary endpoint results this quarter, following completion of the analysis. The analysis will follow the study’s pre-specified statistical analysis plan.