Overview

This is an open-label, dose escalation study to evaluate the safety, toxicity, and pharmacokinetics (PK) as well as preliminary efficacy of BTX-A51 capsules in participants with relapsed or refractory acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS).

The study will be done in three parts. Part 1a (Monotherapy Dose Escalation) of this study is designed to determine the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of orally administered BTX-A51 in up to 35 participants who are evaluable for toxicity. Once the MTD is determined, it is planned that an additional 15 participants will be enrolled in Part 1b (Monotherapy Cohort Expansion) of this study for additional experience with safety and efficacy, and to determine the recommended Phase 2 dose (RP2D) which may or may not be different from the MTD. After determination of MTD and RP2D from Part 1a, Part 1c (Azacitidine Combination Dose Escalation) will enroll up to 30 participants.

Continued treatment will be available under this study protocol for up to eight 28-day cycles (Continued Treatment Phase) if the Investigator judges the benefit outweighs the risk.

Once BTX-A51 treatment has completed, participants will be contacted by telephone every 3 months for up to 2 years after their last treatment for survival status and anticancer therapy (Overall Survival Follow-up).

Eligibility

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