This is a prospective, phase 2, open-label, multi-center, single arm, single agent study, in unfit adult patients with AML or HR MDS who failed or relapsed following first-line therapy.~The study consists of three periods:~Screening: Up to 28 days Treatment: Recurrent 6 days treatment courses with BST-236 Follow-up: The period of time from last day of BST-236 treatment to completion of one year (365 days ±7 days) from the first day of BST-236 treatment~Post-study Follow-up: The period of time from last day of BST-236 treatment to completion of one year (365 days ±7 days) from the first day of BST-236 treatment~Follow-up: One-Year follow-up of survival, starting at the end of study visit~Treatment period: After signing the Informed Consent Form (ICF), meeting all eligibility criteria, and undergoing screening assessments for up to four weeks, eligible patients will receive the first induction course with BST-236, 4.5 g/m2/d administered IV over 1 hour for 6 consecutive days. The first day of the induction is defined as Study Day 1. Following the first treatment course:~AML patients in complete remission (CR) or CR with incomplete count recovery (CRi) or CR with partial hematologic recovery (CRh), and HR MDS patients with CR will receive between 2 to 4 maintenance courses of 6-day treatment with BST-236, every 4-6 weeks. The BST-236 dose in these subsequent treatment courses will be 2.3g /m2/d or 4.5 g/m2/d. The reduced dose must be used in case of previous courses toxicity and is allowed in certain cases according to physician discretion following consultation with the study medical monitor. The interval between treatment courses may be extended to up to 12 weeks to allow resolution of toxicities per investigator discretion and in consultation with principal investigators.~Patients with stable disease defined as failure to achieve at least PR, but with no evidence of disease progression or patients in partial response (PR) will receive a second 6-day course with BST-236, at a dose of 4.5 g/m2/d. Following which:~AML patients in PR or CR, (including CR, CRh or CRi) and HR MDS patients in PR or CR will be treated with maintenance courses as detailed above Patients in stable disease or disease progression may receive alternative treatment outside of the protocol and will be followed for overall survival (OS) until the completion of 1 year of participation in the study (365 days±7 days from the first day of BST-236 treatment). Additional 1 year of post study follow-up will be implemented for these patients in order to follow up on their survival status and their current AML/MDS treatments.~Patients that have a disease progression while treated in the maintenance courses, will not receive any additional BST-236 treatment and will be followed until the completion of 1 year of participation in the study. These patients may also receive alternative treatment outside of the protocol, in such case, they will be followed in regular intervals for progression free survival, OS and development of new malignancies.~Follow-up period: All patients will be followed by periodic in person in-clinic visits, until the completion of 1 year of participation in the study (365 days±7 days from the first BST-236 treatment day).~End of Study (EOS) visits: will be performed on the last day of participation in the study for all patients.~Scheduled in-clinic visits to assess safety and efficacy outcomes will be conducted during the study periods as specified in the Schedule of Activities.~Unscheduled visits may be conducted at any time for safety reasons or for any other reason.~Post study follow-up: All patients will be followed for survival for an additional 1 year from the EOS~QT Evaluation with Pharmacokinetics (PK) sub-study: Up to 20 patients participating in the main study in pre-selected sites, will be asked to participate in a QT evaluation with PK sub-study to assess the effect of BST-236 on the cardiac electrophysiology. In this study, up to 14 blood samples for PK analysis will be taken from each patient during the first induction course and a continuous electrocardiogram (ECG) recording by a Holter monitor will be done in the first 24 hours of BST-236 administration. Patients participating in this study will be asked to sign an additional ICF for the collection of the PK blood samples and ECG recording.
To assess the efficacy, and safety of BST-236 in patients unfit for intensive chemotherapy with AML or HR MDS that failed or relapsed following first line therapy