Who can participate?

Inclusion Criteria:

• Male or female participant aged ≥30 days.
• Not eligible for participation in an ongoing clinical study and have no approved treatment options.
• Participant or participant's health care proxy is able and willing to provide written informed consent and able to follow study instructions.
• Relapsed or refractory (R/R) acute leukemia, as defined by standardized criteria, after standard of care therapy, including but not limited to 1 or 2 cycles of intensive chemotherapy, or venetoclax combinations:

1. R/R leukemia is defined by the presence of ≥5% blasts in the bone marrow and/or persistence or reappearance of peripheral blasts.
2. Participants with persistent leukemia after initial therapy or recurrence of leukemia at any time after achieving a response during or after the course of treatment (including allogeneic hematopoietic stem cell transplant [HSCT]) are eligible.
3. Participants with isolated extra medullary disease are allowed if extramedullary disease was confirmed with biopsy.
4. Participants previously treated on a revumenib clinical trial who are entering the expanded access program for post-transplant maintenance because they are not eligible to receive revumenib on trial or because the trial is closed are not required to meet the relapse/refractory status. Participants who underwent HSCT and are eligible to resume treatment with revumenib will be dosed with the last revumenib tolerated dose prior to transplant.

• Acute leukemia harboring a lysine (K) methyltransferase 2A gene rearrangement (KMT2Ar), nucleoporin 98 rearrangement, nucleophosmin 1 mutation (or mutated) mutation or any other genetic alteration with overexpression of HOXA genes predicted to potentially respond to menin inhibitors.
• Adequate liver, renal, and cardiac function.
• Adequate methods of contraception are required during childbearing age from the time of enrollment through 120 days following the last study drug dose. Barrier contraception in males and double barrier in females or other highly effective methods of contraception.

For participants currently being treated with revumenib in a Syndax-sponsored clinical study or Syndax investigator-sponsored trial, the following criteria must be met:

• In the opinion of the Investigator, participant demonstrated acceptable benefit from and tolerability of the study drug.
• Participant is considered compliant with study drug and procedures.
• Participant does not meet any criteria for study drug discontinuation.
• Investigator and participant agree to continue study drug treatment.

Exclusion Criteria:

• Evidence of uncontrolled infection.
• Pregnant or nursing women.
• Cardiac or gastrointestinal disease.
• Graft-Versus-Host Disease (GVHD): Signs or symptoms of acute or chronic GVHD >Grade 1 within 4 weeks of enrollment. All transplant participants must have been off all systemic immunosuppressive therapy for at least 1 week prior to enrollment and calcineurin inhibitors for at least 1 week, with the exception of steroids.
• History of or any concurrent condition, therapy, laboratory abnormality, or allergy to excipients that, in the Investigator's opinion, either may interfere with the participant's participation or results in the conclusion that it is not in the best interest of the participant to participate.