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

The purpose of this study is to determine the recommended Phase 2 dose(s) (RP2D\[s\]) of bleximenib in phase 1 (Part 1 \[Dose Escalation\] and to determine the safety and tolerability at RP2D in Phase 1 Part 2 (Dose expansion). The purpose of the Phase 2 part of the study is to evaluate the efficacy of bleximenib at the RP2D.


Eligibility Criteria:
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)