A Study of Modakafusp Alfa Together With Daratumumab Adults With Relapsed or Refractory Multiple Myeloma

The drug being tested in this study is called modakafusp alfa (TAK-573). Modakafusp alfa is being tested to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy in combination with daratumumab in participants with relapsed or refractory multiple myeloma (RRMM). The study will consist of 2 phases: Phase 1 Dose Escalation and a Phase 2a Dose Finding. The study will enroll approximately 58 patients. Approximately 18 participants will be enrolled in the Phase 1 Dose Escalation/De-escalation and two dose levels of modakafusp alfa in combination with daratumumab SC will be selected to be further explored in the randomized Phase 2a Dose Finding part of the study wherein, approximately 40 participants will be randomly assigned by chance (like flipping a coin) to one of the two treatment groups: * Phase 2a Dose Finding: Modakafusp Alfa (DL1) + Daratumumab * Phase 2a Dose Finding: Modakafusp Alfa (DL2) + Daratumumab This multi-center trial will be conducted worldwide. The overall time to participate in this study is approximately 60 months. Participants who discontinue study drug treatment for reasons other than progressive disease will continue progression-free survival (PFS) follow-up every 4 weeks from the end of treatment (EOT) visit until the occurrence of progressive disease, death, the start of subsequent systemic antineoplastic therapy, study termination, whichever occurs first.