A Study of CBX-250 in Participants With Relapsed or Refractory Myeloid Leukemias

This study is testing a new experimental drug called CBX-250 for people with blood cancers — specifically acute myeloid leukemia (AML), high-risk myelodysplastic syndrome (MDS), or chronic myelomonocytic leukemia (CMML) — that have come back or stopped responding to previous treatments. **You may be eligible if...** - You are 18 or older (or as young as 12 in certain cases) with relapsed or treatment-resistant AML, MDS, or CMML - Your cancer has not responded to standard treatments, including stem cell transplant - You carry a specific genetic marker called HLA-A*02:01 - Your heart, liver, and kidneys are functioning well enough to handle treatment - You have recovered from most side effects of your last treatment **You may NOT be eligible if...** - You have active HIV, hepatitis B, or hepatitis C - You have active cancer in your brain or spinal fluid - You have serious heart problems (e.g., recent heart attack or severe heart failure) - You have active graft-versus-host disease requiring immune-suppressing medications - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.