A Study of JNJ-75276617 in Combination With Conventional Chemotherapy for Pediatric and Young Adult Participants With Relapsed/Refractory Acute Leukemias

Inclusion Criteria:

* Acute leukemia harboring histone-lysine N-methyltransferase 2A (KMT2A) or nucleophosmin 1 gene (NPM1) or nucleoporin (NUP98 or NUP214) alterations
* Performance status greater than or equal to (\>=) 50 by lansky scale (for participants less than \[\<\] 16 years of age) or \>=50 percent (%) karnofsky scale (for participants \>=16 years of age)
* Estimated or measured glomerular filtration rate \>= 60 milliliter per minute per 1.73 meter square (mL/min/1.73m\^2) based on the bed side schwartz formula

Exclusion Criteria:

* Received an allogeneic hematopoietic transplant within 60 days of screening
* Active acute graft-versus-host disease of any grade or chronic graft-versus-host which is not well-controlled
* Received immunosuppressive therapy post hematopoietic transplant within 30 days of enrollment
* Diagnosis of Down syndrome associated leukemia, acute promyelocytic leukemia, juvenile myelomonocytic leukemia
* Diagnosis of fanconi anemia, kostmann syndrome, shwachman diamond syndrome, or any other known bone marrow failure syndrome
* Prior exposure to menin-KMT2A inhibitors
* Prior cancer immunotherapy (ie \[that is\], Chimeric Antigen Receptor-T Cell Therapy \[CAR-T\], inotuzumab, gemtuzumab ozogamicin) 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)