GEN3018

The drug that will be investigated in the trial is an antibody, GEN3018. Since this is the first trial of GEN3018 in humans, the main purpose is to evaluate safety. In addition to safety, the trial will determine the recommended GEN3018 dose(s) to be tested in a larger group of participants and assess preliminary anti-tumor activity of GEN3018. GEN3018 will be studied in refractory (resistant to treatment) or relapsed (disease has returned) acute myeloid leukemia (also known as R/R AML) and refractory or relapsed higher-risk myelodysplastic syndrome (also known as R/R HR-MDS). The trial consists of 2 parts: 1. Part 1 Dose Escalation will test increasing doses of GEN3018 to identify a safe dose level to be tested in the next part 2. Part 2 Dose Refinement will further test the GEN3018 dose(s) determined from the Dose Escalation. Up to 78 participants may be treated in this trial (up to 60 participants in Part 1; up to 18 participants in Part 2). For an individual participant in the trial, the estimated treatment duration will be up to 1 year. Participation in the trial will require regular scheduled visits to the site. At site visits, there will be various tests (such as blood draws) to monitor whether the treatment is safe and effective. Participants will also be contacted every 3 months after treatment ends to monitor how they are doing. All participants in the trial will receive active drug (ie, GEN3018); no one will be given placebo.