A Study of BTX-A51 in People With Relapsed or Refractory Acute Myeloid Leukemia or High-Risk Myelodysplastic Syndrome

Inclusion Criteria:

Demonstration of understanding and voluntarily signing of an informed consent form
Age ≥ 18 years
Diagnosis of acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) according to the World Health Organization classification and, with respect to MDS, that is high risk; participants must have refractory or relapsed disease and be ineligible for or have exhausted standard therapeutic options that would otherwise be likely to provide clinical benefit
Eastern Cooperative Oncology Group performance status ≤ 2 and life expectancy of ≥ 6 weeks
Adequate organ function (Grade 1 serum creatinine; Grade 1 total bilirubin; aspartate aminotransferase and/or alanine transaminase ≤ 2 × ULN)
Females of childbearing age must not be pregnant at time of Screening/beginning of treatment and agree to either abstain from sexual intercourse or use highly effective methods of contraception (for up to 3 months after last dose of study drug)
Males sexually active with a woman of childbearing age must agree to use barrier method of birth control during and after the study (up to 3 months after last dose of study drug)

Exclusion Criteria:

Diagnosis of acute promyelocytic leukemia
White blood cell count > 20 x 10^9/L
Receipt of cancer chemotherapy (other than hydroxyurea) within 2 weeks prior to the start of study drug
In participants who have undergone autologous or allogeneic stem cell transplantation: transplantation within the 3 months prior to Screening; active graft-versus-host disease requiring anything other than topical corticosteroids and budesonide; treatment with systemic immunosuppressive medications including high-dose steroids (≥ 20 mg prednisolone or equivalent per day), or calcineurin inhibitors (e.g., cyclosporine, tacrolimus) for at least 1 week prior to Screening, and sirolimus, mycophenylate mofetil, azathioprine, or ruxolitinib for at least 2 weeks prior to Screening
Immediate life-threatening severe complications of leukemia such as uncontrolled bleeding, pneumonia with hypoxia or shock, and/or disseminated intravascular coagulation
Persistent toxicities from prior treatment of Grade 2 or higher
Active uncontrolled systemic fungal, bacterial, mycobacterial, or viral infection
Clinically significant cardiac disease
Known dysphagia, short-gut syndrome, gastroparesis, or other conditions that limit the ingestion or gastrointestinal absorption of drugs administered orally
Any other concurrent medical condition or disease that is likely to interfere with study procedures or results, or that, in the opinion of the Investigator, would constitute a hazard for participating in this study
If female, pregnant or breastfeeding