A Study to Assess the Safety, Tolerability, and Antileukemic Activity of Debio 1562M in Participants With Acute Myeloid Leukemia (AML)

Inclusion Criteria:

• For Phase 1-Dose escalation: Relapsed/refractory (R/R) AML (excluding acutepromyelocytic leukemia) based on World Health Organization (WHO) Classification 2022and relapsed/refractory higher-risk myelodysplastic syndrome (R/R HR -MDS) (includeshigh- and very high-risk MDS) as confirmed by the Revised International PrognosticScoring System (IPSS-R) for whom no standard therapy of proven benefit is available.

• For Phase1-Dose optimization and Phase 2: R/R AML (excluding acute promyelocyticleukemia) based on world health organization (WHO) classification 2022 for whom nostandard therapy of proven benefit is available.

• Eastern Cooperative Oncology Group performance (ECOG PS) status ≤2.

• Previous treatment-related toxicities must be resolved to ≤Grade 1 (excludingalopecia).

• Individuals with prior autologous or allogeneic bone marrow (BM) transplant areeligible.

• Prior allogeneic transplant must meet the following conditions: the transplant musthave been performed more than 120 days before the first administration of Debio 1562M, the participant must not have ≥Grade 1 active graft versus host disease (GvHD) at the time of trial treatment start and must be off all immunosuppressionfor at least 2 weeks prior to starting treatment with Debio 1562M. Steroid use [equivalent to ≤20 milligrams (mg) prednisone] before and during the trial isallowed as long as this is not being used as post-transplant immunosuppression orgraft versus host disease (GVHD) directed therapy.

• Adequate renal and hepatic function defined as:

1. Estimated glomerular filtration rate (eGFR) ≥60 milliliter per minute (mL/min)based on the chronic kidney disease-Epidemiology Collaboration based oncreatinine (CKD-EPIcr) 2021 equation.

2. Aspartate transaminase (AST) and alanine aminotransferase (ALT) ≤3 × upperlimit of normal (ULN).

3. Serum total bilirubin level ≤1.5× ULN (for participants with Gilbert's syndromeor chronic blood transfusions, total bilirubin ≤3.0× ULN).

Exclusion criteria:

• Any prior exposure to cluster of differentiation (CD) 37 targeting agents.

• Clinically active infection including known active hepatitis B or C, humanimmunodeficiency virus infection, or cytomegalovirus or any other known concurrentinfectious disease that, in the judgment of the Investigator, would make aparticipant inappropriate for enrollment into this trial (retesting not required).

• Clinically significant cardiac dysfunction within 6 months before enrollmentincluding New York Heart Association Class III or IV heart failure, uncontrolledangina, myocardial infraction, severe uncontrolled ventricular arrhythmias, QTinterval corrected for HR according to Fridericia's formula (QTcF) >470 ms.

• Clinically significant and active cardiopulmonary disease.

• Other malignancies, except of:

1. Hematologic malignancies other than those being investigated for whichindividuals are not on active antineoplastic therapy

2. Nonhematologic malignancies in remission and for which individuals must havecompleted all antineoplastic therapy at least 6 months before trial treatmentstart and all treatment-related toxicities must have resolved to ≤Grade 1.

• Evidence for active central nervous system (CNS) leukemia involvement. If theparticipant has a prior history of CNS AML, the participant must have at least 2negative cerebrospinal fluid (CSF) analyses and either a magnetic resonance imaging (MRI) or computed tomography (CT) (if MRI is not feasible) of the braindemonstrating no evidence of CNS disease.

• Evidence of peripheral neuropathy Grade ≥2.

• History of hypersensitivity to Debio 1562M (including its components), or any of itsexcipients.

• Treatment with any antileukemic therapy including chemotherapy, immunotherapy,radiotherapy, hormonal, biologic, or any investigational agent within 14 days orwithin 5 half-lives of the investigational treatment prior to first dose of trialtreatment, whichever is shorter. Hydroxyurea may be given prior to and after trialtreatment start for control of leukocytosis.

• Major surgery within 4 weeks prior to the start of treatment, or participant whohave not recovered from side effects of the surgery.

• Pregnancy or breastfeeding.

Note: Other Inclusion/Exclusion criteria may apply.