SELLAS Life Sciences Group announced on Wednesday, October 28, 2026, that its Phase 3 REGAL study evaluating galinpepimut-S (GPS) in patients with acute myeloid leukemia (AML) has reached its pre-specified 80th event. In the context of this survival-driven study, an event refers to a patient death across the combined treatment groups. Reaching this numerical threshold automatically triggers the final analysis of the trial, moving the New York-based biopharmaceutical company toward a major data readout expected later in the fourth quarter of 2026.

With the 80th event recorded, the company will immediately begin the procedural steps required to evaluate how the experimental therapy performed, according to a GlobeNewswire release. These steps include locking the study database, unblinding the patient records, and conducting a formal statistical analysis of the primary endpoint data. While the announcement marks the conclusion of event tracking, it does not yet reveal whether the drug succeeded in extending patients' lives.

What the 80th Event Means for the REGAL Study

In oncology research, late-stage trials like the REGAL study (NCT04229979) are frequently designed around event-driven timelines rather than fixed calendar dates. Because the primary goal of the study is to measure overall survival, researchers must wait until a specific number of deaths have occurred across both the experimental and control arms to gather enough statistical power to compare the two groups accurately.

According to coverage from Yahoo Finance, SELLAS President and Chief Executive Officer Angelos Stergiou, MD, ScD h.c., noted that reaching the 80th event represents a critical milestone for the study. He stated that AML remains an area of significant unmet medical need, particularly for patients in their second complete remission who face limited options to keep the blood cancer from returning.

The pace of these events has been closely tracked by market observers and patient advocates alike. While the company's official release announced that the 80th death had triggered the final review, Stocktwits reported that the latest previously disclosed count stood at 78 events as of May 11, 2026, and emphasized that the company remained completely blinded to efficacy and survival outcomes prior to this final unblinding phase. Because the data remains locked until the verification process finishes, reaching the 80th event is strictly a measure of data maturity rather than an early indicator of positive or negative outcomes.

Targeting Acute Myeloid Leukemia in Remission

Acute myeloid leukemia is an aggressive cancer of the blood and bone marrow. While many patients achieve an initial remission through chemotherapy or targeted drugs, the disease frequently relapses. Patients who undergo salvage therapy and manage to achieve a second complete remission (CR2) often face a poor prognosis,especially if they are ineligible for a stem cell transplant.

The Phase 3 REGAL study is a randomized, registrational trial evaluating GPS as a maintenance therapy specifically for AML patients in this precarious CR2 stage, as detailed by Investing.com. Maintenance therapy is given to patients whose cancer is currently undetectable, with the goal of preventing or delaying a relapse. In the trial, GPS is compared against an investigator's choice of best available therapy. Alongside the primary measure of overall survival, researchers are also tracking secondary endpoints, including leukemia-free survival and broader safety outcomes.

Licensed from Memorial Sloan Kettering Cancer Center, GPS is an immunotherapy designed to target the Wilms tumor 1 (WT1) protein. This specific protein is present in a wide variety of tumor types and plays a role in cancer cell growth. By training the patient's own immune system to recognize and attack cells expressing the WT1 antigen, researchers hope the treatment can eliminate lingering microscopic disease before it causes a full relapse.

Market Context and Pipeline Developments

The approaching readout has generated considerable financial and regulatory discussion. According to Stocktwits, institutional interest became visible on Tuesday when asset manager BlackRock disclosed in a filing that it owned 15.87 million shares of SELLAS as of September 30, 2026—representing a 7.9% stake and a roughly 31% increase from its March-end holdings of 12.14 million shares. Following that disclosure, the company's stock closed Tuesday up 7% at $12.17.

At the same time, European health planning documents have sparked debate among retail investors regarding potential regulatory timelines. An Austrian health-technology assessment pipeline appendix listed November 1, 2027, as a projected European Commission approval date for GPS, while a Dutch Medicines Horizon Scan entry listed April 2027 for expected registration. However, the Austrian report explicitly cautions that changes in regulatory timelines and development status contribute to inherent uncertainty. Such horizon-scanning documents are routinely used by European healthcare systems for advance budget and logistical planning, and they do not reflect insider knowledge of unblinded study data.

Beyond GPS, SELLAS is also testing a second experimental drug known as SLS009, or tambiciclib, which acts as a selective CDK9 inhibitor. In August 2026, the company reported that 28 patients had enrolled in an 80-patient randomized Phase 2 study evaluating SLS009 in newly diagnosed AML patients who are unlikely to benefit from standard treatments like azacitidine and venetoclax, or who show early resistance after two cycles. Topline findings from that separate Phase 2 study are also expected during the fourth quarter of 2026. The company additionally presented laboratory findings in September 2026 showing that SLS009 demonstrated activity in patient-derived pancreatic cancer models resistant to the RAS inhibitor daraxonrasib.

Key Questions Ahead of the Topline Readout

As patients, oncologists, and investors wait for the preliminary data later this quarter, several critical questions remain unanswered by the procedural milestone announcement.

What does the statistical analysis plan require for success?

While the company confirmed that the analysis will follow a pre-specified statistical analysis plan, the announcement did not disclose the exact survival improvement, hazard ratio, or p-value required for the study to be declared statistically significant. These metrics will determine whether the difference in survival between the GPS group and the control group is meaningful or due to chance.

What will the survival comparison and secondary data show?

The upcoming fourth-quarter announcement will need to clarify the median overall survival duration in both the treatment arm and the control arm. Observers will also look to see if SELLAS releases secondary endpoint figures—such as leukemia-free survival, subgroup performance, and detailed safety profiles—alongside the initial topline survival numbers, or saves those details for a future medical conference.

What are the next steps for regulatory submission?

In August 2026, Stergiou noted that a successful efficacy analysis could lead to a potential Biologics License Application (BLA) submission to the U.S. Food and Drug Administration (FDA). If the primary endpoint is met, the company will need to outline the timeline for regulatory discussions in both the United States and Europe. Conversely, if the trial fails to meet its primary survival goal, leadership will have to clarify what options, if any, remain for the GPS program.

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