Phase 3 Trial to Test GPS Vaccine as Maintenance Therapy in High-risk Acute Myeloid Leukemia Patients

Phase 3 Trial to Test GPS Vaccine as Maintenance Therapy in High-risk Acute Myeloid Leukemia Patients

SELLAS Life Sciences announced plans for a newly streamlined Phase 3 trial to evaluate its investigational vaccine galinpepimut-S (GPS) as maintenance therapy for high-risk acute myeloid leukemia (AML) patients.

If trial data warrants, the company will request regulatory approval of the GPS vaccine for these patients. Its decision follows a meeting with the U.S. Food and Drug Administration (FDA) to discuss clinical and regulatory strategy.

The open-label trial is expected to enroll about 116 AML patients in complete remission after a second-line treatment, who are not eligible for bone marrow transplant. The trial will be conducted in some 50 clinical sites in the United States and Europe.

“We are excited to begin this late-stage Phase 3 program with GPS in AML,” Hagop M. Kantarjian, MD, principal investigator of the Phase 3 AML clinical development program, said in a press release.

“We are hopeful that this new immunotherapeutic vaccine approach will improve outcomes in this patient population, which is at a very high risk of leukemic relapse,” added Kantarjian, chair of the leukemia department at the University of Texas MD Anderson Cancer Center. Earlier plans were for a larger and longer Phase 3 study in AML patients in complete remission after a first-line therapy.

GPS is an investigational anti-cancer vaccine composed four small man-made proteins derived from the Wilms tumor (WT1) protein. WT1 is found at high levels in several cancers and is considered the No. 1 target for cancer immunotherapy by the National Cancer Institute.

Licensed by SELLAS from Memorial Sloan Kettering Cancer Center, the immunotherapy is designed to have a broad application, with the ability to induce a strong immune response to any cancer cell positive for the WT1 protein.

Phase 2a trial (NCT01266083) found that GPS maintenance therapy is safe and extends the lives of patients who achieved a complete response to second-line treatment — a median overall survival of 16.3 months in those treated compared to 5.4 months in a similar group of patients who were not part of this open-label study.

The Phase 3 trial will randomly assign patients to the GPS vaccine or physician’s choice of best available treatment; its main goal is how significantly GSP prolongs overall survival compared to standard of care approaches.

Secondary measures include length of time patients go without signs of leukemia, T-cell responses against the WT-1 protein, and the proportion of patients negative for minimal residual disease, defined as small numbers of cancer cells that remain in circulation or in the bone marrow after treatment.

An interim analysis assessing the treatment’s safety and preliminary signs of efficacy is planned after 80 reports of disease progression or other events.

“The new design is expected to streamline sample size, time to accrual completion, primary endpoint readout and potential time to market, as well as costs. We believe this new study design provides SELLAS with a quicker path to approval, provided the study is positive,” said Angelos M. Stergiou, MD, SELLAS’ president and CEO.

The GPS vaccine has been designed an orphan drug, and place on fast track development, by the FDA and named an orphan medicinal product by the European Medicines Agency (EMA) as a potential treatment of AML, malignant plural mesothelioma, and multiple myeloma.

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