A Safety Study of SEA-CD70 in Patients With Myeloid Malignancies

This is a phase 1, open-label, multicenter, dose-finding, and dose expansion study designed to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of SEA-CD70 monotherapy and SEA-CD70 in combination with azacitidine in adults with myeloid malignancies. The study will be conducted in up to 6 parts. * Part A is a dose-escalation cohort designed to identify the MTD or recommended expansion dose of SEA-CD70 monotherapy in participants with relapsed/refractory (hypomethylating agent \[HMA\]-failure) MDS. * Part B is an expansion cohort designed to evaluate the safety and tolerability of SEA-CD70 monotherapy in participants with relapsed/refractory (HMA-failure) MDS. * Part C is an expansion cohort designed to evaluate the safety and tolerability of SEA-CD70 monotherapy in participants with relapsed/refractory AML. * Part D contains dose-finding/dose optimization cohorts designed to evaluate the safety/tolerability and identify the recommended expansion dose of SEA-CD70 in combination with azacitidine in participants with 1) relapsed/refractory (HMA-failure) MDS or MDS/AML, and 2) previously untreated higher-risk per IPSS-M (Moderate High, High or Very High) MDS or MDS/AML. * Part E is an expansion cohort designed to evaluate the safety and tolerability of SEA-CD70 in combination with azacitidine vs azacitidine in participants with previously untreated higher-risk per IPSS-M (Moderate High, High, or Very High) MDS or MDS/AML. * Part F is an expansion cohort designed to evaluate the safety and tolerability of SEA-CD70 in combination with azacitidine in participants with relapsed/refractory (HMA-failure) MDS or MDS/AML. * Part G will find out how much SEA-CD70 with azacitidine and with venetoclax should be given to participants with previously untreated AML who are unfit for standard of care induction chemotherapy