AML Drug Trial Delay Sparks Cautious Hope for Longer Patient Survival

NEW YORK, NY – December 29, 2025 – In a development that has captured the attention of oncologists and investors, SELLAS Life Sciences Group announced today that its pivotal Phase 3 REGAL trial for a novel Acute Myeloid Leukemia (AML) therapy has not yet reached its conclusion, as patients in the study appear to be surviving longer than originally anticipated.

The company remains blinded to the specific outcomes, but the delay itself is being interpreted by some as a potentially positive signal in the fight against a notoriously aggressive blood cancer.

The Waiting Game in the REGAL Trial

SELLAS confirmed that its contract research organization reported 72 “events”—the clinical term for patient deaths in this study—as of December 26, 2025. The final analysis of the trial is event-driven and is designed to be triggered only after 80 events have occurred among the study participants. The company and its Independent Data Monitoring Committee (IDMC) had previously projected that this threshold would be met before the end of the year.

The REGAL trial is evaluating galinpepimut-S (GPS), a novel cancer immunotherapy, as a maintenance treatment for AML patients who have achieved a second complete remission (CR2). For these patients, the cancer has returned once and been beaten back a second time, leaving them in a precarious state with a high risk of relapse and historically poor long-term survival rates. The trial's primary goal is to determine if GPS can extend overall survival compared to the physician’s choice of best available therapy.

“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. He emphasized that the company remains fully blinded to which patients are receiving GPS versus the control treatment. This blinding is a critical component of unbiased clinical research, ensuring that the final results are scientifically valid.

Because no formal analysis was performed, this update on the aggregate number of events does not impact the statistical integrity of the trial. SELLAS has committed to announcing when the 80th event occurs, which will officially initiate the final data analysis.

A Paradox of Hope: Why Slower Could Mean Better

While a delay in a clinical trial can often be a source of frustration for a company and its stakeholders, in an overall survival study, it can be a harbinger of good news. The statistical plan for the REGAL trial was based on historical data for AML patients in CR2, who face a grim prognosis. The fact that fewer patients than expected have passed away within the projected timeframe suggests that the overall survival in the trial—across both the GPS and control groups combined—is better than the historical benchmark.

Dr. Stergiou alluded to this possibility, stating, “While the 80th 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.”

The ultimate success of GPS hinges on demonstrating a statistically significant survival benefit over the control arm. If patients in the control group are also faring better than expected, the bar for GPS to show a superior outcome becomes higher. However, the more likely and hopeful interpretation is that an effective therapy in the investigational arm is substantially extending lives, thereby slowing the rate at which events accumulate.

The Unmet Need and the Promise of a Novel Immunotherapy

Acute Myeloid Leukemia is a fast-progressing cancer of the blood and bone marrow. While initial treatments can lead to remission, relapse is common. For patients who achieve a second complete remission, options are severely limited. Many are not eligible for a potentially curative stem cell transplant due to age, comorbidities, or lack of a suitable donor.

“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,” explained Dr. Yair Levy, a member of the REGAL Steering Committee and Director of Hematologic Malignancies Research at Texas Oncology Baylor University Medical Center. This stark reality underscores the desperate need for new maintenance therapies that can prolong remission and extend life.

Galinpepimut-S represents a fundamentally different approach. Licensed from Memorial Sloan Kettering Cancer Center, it is a cancer vaccine that targets the Wilms Tumor 1 (WT1) protein. WT1 is a protein that is rarely found in healthy adult tissues but is overexpressed in a wide range of cancers, including AML. By targeting WT1, GPS is designed to stimulate the patient’s own immune system to identify and destroy any residual cancer cells that could lead to a relapse. “We hope to see an extended survival benefit, with a tolerable safety profile, as observed in previous GPS studies,” Dr. Levy added.

This immunotherapeutic mechanism offers a potential advantage over traditional chemotherapy, which can be highly toxic. As a maintenance therapy, a well-tolerated agent that can be administered over the long term is ideal. The final data from REGAL will be critical in determining if GPS fulfills this promise.

As the new year approaches, the wait for the final eight events continues. The medical community, patients, and SELLAS Life Sciences are in a state of watchful anticipation, holding onto the cautious optimism that this unexpected delay signals a meaningful step forward in the treatment of AML.