A Phase 1/2 Study of Bleximenib in Participants With Acute Leukemia

Inclusion Criteria

Phase 1:

• Relapsed or refractory (R/R) acute leukemia and has exhausted, or is ineligible for, available therapeutic options
• Participants greater than or equal (>=)12 and less than (<) 18 years of age are only eligible for the Phase 1 adolescent cohort
• Acute leukemia harboring histone-lysine N-methyltransferase 2A (KMT2A), nucleophosmin 1 gene (NPM1) or nucleoporin 98 gene or nucleoporin 214 gene (NUP98 or NUP214) alterations

Phase: 2

• Participants greater than 18 years are eligible
• Must have had an initial diagnosis of acute myeloid leukemia (AML) per the WHO 2022 classification criteria and have relapsed/refractory disease
• AML harboring KMT2A-r (gene rearrangement/translocation) or NPM1 mutations only

For Both Phase 1 and 2:

• Pretreatment clinical laboratory values meeting the following criteria: (a) Hematology: white blood cell (WBC) count less than or equal to (<=) 20*10^9/liter (L) and (b) renal function; Estimated or measured glomerular filtration rate greater than or equal to (>=) 50 milliliter per minute (mL/min) per four variable modified diet in renal disease (MDRD) equation
• Eastern Cooperative Oncology Group (ECOG) performance status grade of 0, 1 or 2. Adolescent participants only: Performance status >=70 by Lansky scale (for participants less than [<]16 years of age) or >=70 Karnofsky scale (for participants >=16 years of age)
• A female of childbearing potential must have a negative highly sensitive serum beta-human chorionic gonadotropin at screening and within 48 hours prior to the first dose of study treatment
• Participant must agree to all protocol required contraception requirements and avoid sperm or egg donations or freezing for future reproductive use while on study and for 90 days (males) or 6 months (females) after the last dose of study treatment

Exclusion Criteria

• Acute promyelocytic leukemia, diagnosis of Down syndrome associated leukemia or juvenile myelomonocytic leukemia according to World Health Organization (WHO) 2016 criteria
• Active central nervous system (CNS) disease
• Prior solid organ transplantation
• QTc according to Fridericia's formula (QTcF) for males >= 450 millisecond (msec) or for females >= 470 msec. Participants with a family history of Long QT syndrome are excluded
• Exclusion criteria related to stem cell transplant: a. Received prior treatment with allogenic bone marrow or stem cell transplant <=3 months before the first dose of study treatment; b. Has evidence of graft versus host disease; c. Received donor lymphocyte infusion <=1 month before the first dose of study treatment; d. Requires immunosuppressant therapy (exception: daily doses <=10 milligrams (mg) prednisone or equivalent are allowed for adrenal replacement)
• Prior cancer immunotherapy within 4 weeks prior to enrollment or blinatumomab within 2 weeks prior to enrollment. Additional prior cancer therapies must not be given within 4 weeks prior to enrollment or 5 half-lives of the agent (whichever is shorter)