Background: Patients with relapse/refractory (r/r) AML have poor outcomes. Allogeneic stem cell transplantation (allo-SCT) can potentially cure some patients with r/r AML who achieve second CR (CR2). However, barriers to transplantation such as advanced age, poor functional status/comorbidities or lack of donor exist and not all patients are able to proceed to allo-SCT. Therefore, novel strategies to decrease relapse risk in these patients are urgently needed. A National Cancer Institute consensus study on prioritization of cancer antigens ranked the Wilms tumor 1 (WT1) protein as the top immunotherapy target in cancer. WT1 has emerged as an encouraging vaccine target in AML due to its overexpression in leukemic blasts. Maintenance therapy with Galinpepimut-S (GPS), a multivalent heteroclitic WT1 peptide vaccine, has shown promising activity in patients with AML by inducing a strong innate immune response (CD4+/CD8+) against the WT1 antigen and across a broad range of HLA types. Methods: This is an open-label, multicenter, randomized, phase III study of GPS vs. BAT in patients with AML in CR2/CRp2 (CR2 with incomplete platelet recovery). BAT may include observation, low dose cytarabine and hypomethylating agents +/- venetoclax. The primary endpoint of the study is overall survival (OS). Secondary endpoints include safety and tolerability of GPS and leukemia-free survival. Exploratory endpoints include WT1-specific immune response dynamics in blood and bone marrow. Approximately 125 - 140 patients will enroll, in a 1:1 ratio, to provide at least 90% power under an assumed hazard ratio of 0.52, based on median OS of 8.0 m (BAT) and 15.4m (GPS). Randomization will be stratified by duration of CR1 ( < 12m vs. ≥12m), Cytogenetics (poor-risk vs. all other), CR2 vs. CRp2 and measurable residual disease (MRD) after CR2 (MRD- vs. MRD+). Inclusion criteria consists of willing subjects ≥18y with AML within 6m of achieving CR2/CRp2, ineligible for allo-SCT due to any reason, with ≥300 lymphocytes/ul and with adequate renal and hepatic function. Subjects with central nervous involvement, having received a live vaccine 30d prior to first dose of study drug, having a diagnosis of immunodeficiency, receiving ≥10mg daily of prednisone equivalent (or any other systemic immunosuppressant) for any indication 7d prior to first dose of study drug, hypersensitivity to study agent and with a history of solid organ transplant would be excluded. The clinical trial is actively enrolling, and the registry number is NCT04229979. Clinical trial information: NCT04229979.