Galinpepimut-S Versus Investigator's Choice of Best Available Therapy for Maintenance in AML CR2/CRp2

This is an open-label, multicenter, randomized, parallel groups study of galinpepimut-S (GPS) vs. best available treatment (BAT) in patients with AML in second complete remission (CR2) or in second complete remission with incomplete platelet recovery (CRp2). All patients will have their historical bone marrow samples and/or peripheral blood drawn during screening stained for WT1 via IHC and/or analyzed via PCR by central pathology review. The primary goal of the study will be to demonstrate an advantage for GPS in overall survival in these patient populations. The study will enroll approximately 140 patients and will be conducted at about 110 investigational sites. Patients will be randomized 1:1 to GPS or BAT stratified by whether they are in CR2 or CRp2, their cytogenetic risk at diagnosis (poor vs all other), whether they harbor minimal residual disease (MRD), and the duration of CR1 of less than one year or one year or more. Patients on the BAT arm may be treated with 1. observation (whereby palliative management with hydroxyurea is allowed), 2. a hypomethylating agent (decitabine or azacitidine), 3. venetoclax and/or 4. low-dose ara-C. Patients whose remission in CR2 can be maintained with molecularly targeted agents (e.g. FLT-3 or IDH inhibitors) per investigator's determination will not be eligible. However, there are no restrictions on prior use of any agents in the CR1 setting. Patients cannot receive GPS as an adjunct therapy to any other agents. Patients on the GPS arm will receive 70 μg of sargramostim (GM-CSF) on Day -2 and Day 1 before each injection of GPS. The first two administrations of GM-CSF will take place at the same anatomical site as the planned administration of GPS within each treatment cycle. GPS will be administered as an immunization induction every 2 weeks for 6 administrations (Weeks 0 - 10); this will be followed by a 4-week period of no treatment. Treatment will then resume for 6 administrations as an initial booster phase every 4 weeks (Weeks 14 - 34) which will again be followed by a period of no treatment lasting 6 weeks. GPS will be resumed after this period as a second booster phase and will be administered every 6 weeks (Weeks 40 - 52). Patients who remain in remission after 52 weeks will receive treatment every 2 months (Q2M) in the second year of treatment. Patients who remain in remission after 2 years will be treated every 3 months (Q3M) until disease relapse. Following each administration of GM-CSF or GPS, patients will be observed for approximately 30 minutes. An End of Treatment visit will be conducted 30 days following the last dose of GPS. Patients will then enter the long-term follow-up portion of the trial where they will be followed for recurrence of leukemia and overall survival. To ensure a comparable level of observation, patients randomized to the BAT arm will be seen every 4 weeks through Week 52. All patients will undergo bone marrow aspirates and biopsies at screening, Week 12, Week 52, and end of treatment or relapse. Bone marrow examinations will then be repeated as clinically indicated. Patients will be assessed for safety at each clinic encounter. The primary endpoint will be overall survival.