Venetoclax in Addition to Sequential Conditioning With Fludarabine / Amsacrine / Ara-C (FLAMSA) + Treosulfan for Allogeneic Blood Stem Cell Transplantation in Patients With MDS, CMML or sAML

This trial is studying whether adding venetoclax (a targeted cancer drug) to an intensive conditioning regimen before a stem cell transplant improves outcomes for patients with certain blood cancers: MDS (a bone marrow disorder), CMML (a rare blood cancer), or secondary AML (leukemia that developed from another blood condition). **You may be eligible if...** - You have been diagnosed with MDS, CMML, or secondary AML according to WHO criteria with high-risk features (blast count above 5% or certain dangerous gene mutations) - A stem cell transplant from a donor has been planned as part of your treatment - You are in acceptable overall health for transplant - You have signed informed consent **You may NOT be eligible if...** - You have a different type of leukemia or blood cancer not listed - You are too unwell to undergo stem cell transplantation - You have received certain prior treatments that conflict with the study protocol Talk to your doctor to see if this trial is right for you.