A Study of MT-0169 in Participants With Relapsed or Refractory Multiple Myeloma

The drug being tested in this study is called MT-0169. The study will evaluate the safety, tolerability, preliminary efficacy, PK, pharmacodynamics, and immunogenicity of MT-0169 monotherapy in participants with RRMM. The study will enroll up to 54 total participants. The purpose of this study is to evaluate the safety and tolerability of MT-0169 in subjects with relapsed or refractory multiple myeloma (RRMM) and to estimate the maximum tolerated dose (MTD) or the recommended Phase 2 dose (RP2D). MT-0169 will be given as an intravenous (IV) infusion over 60 minutes on the same day every week (i.e., days 1, 8, 15 and 22) or every 2 weeks (i.e., days 1 and 15) of each cycle. A cycle is defined as 28 days. A subject may participate for the following three (3) periods: Screening Period - up to 28 days before first dose of MT-0169 Treatment Period - active period where a subject will receive doses of MT-0169 over a 28-day treatment period Follow-up Period - up to 12 months after the last patient in the study to receive the last dose of MT-0169. Participants can receive MT-0169 until the cancer worsens, side effects prevent further study treatment, or until the participant leaves the study for other reasons decided by the participant, the study doctor, or the sponsor of the study. After treatment has finished, participants will have a check-up of their disease status every 12 weeks. This multi-center trial will be conducted in the United States. The overall duration of the study will vary for each participant because they will receive study treatment until unacceptable toxicity, withdrawal of consent, death, termination of the study by the sponsor, or fulfillment of another discontinuation criterion. Participants will be followed up for 30 days after the last dose of study drug for a follow-up assessment for any side effects. Participants will then be followed every 12 weeks to check for the status of their disease up to 12 months after the last subject on the trial has the last dose of study drug, or the sponsor discontinues the study, whichever occurs first.