A Study to Investigate the Safety, Tolerability, Efficacy, Pharmacokinetics, and Immunogenicity of TAK-573 in Participants With Refractory Multiple Myeloma

The drug being tested in this study is called TAK-573. TAK-573 is being tested to treat
participants who have refractory MM. The study consists of 2 Phases, 1 and 2a. The study will
enroll approximately 51 and 18 participants in Phase 1 and 2a respectively. Participants will
be randomly assigned to one of the following treatment groups in each Phase:

- Phase 1 Schedule A: TAK-573 0.001 to 14 mg/kg

- Phase 1 Schedule B: TAK-573 TBD

- Phase 1 Schedule C: TAK-573 TBD

- Phase 1 Schedule D: TAK-573 TBD

- Phase 2: TAK-573 TBD

The Phase 1 portion of the study will follow a 3+3 dose escalation design to evaluate
once-weekly up to 4 different schedules of administration of TAK-573 starting at 0.001 mg/kg
for DLT evaluation and to determine the maximum tolerated dose (MTD) or an optimal biological
dose (OBD) for assessments in Phase 2a.

This multi-center trial will be conducted in the United States. The maximum treatment
duration in this study is up to 12 months and overall time to participate in the study is
approximately up to 40 months. Participants will make 33 visits to the clinic, and will be
contacted every 12 weeks for post treatment follow-up. Participants will be followed up for
survival until death, lost to follow-up, consent withdrawal, or study termination by the
sponsor, whichever occurs first.

Inclusion Criteria:

1. Has MM defined by the IMWG criteria with evidence of disease progression and:

- Is in need of additional myeloma therapy as determined by the investigator.

- Has previously received at least 3 lines of myeloma therapy.

- Is either refractory to or intolerant of at least one proteasome inhibitor and a
least one immunomodulatory drug.

In addition, after the MTD/OBD is defined, must also be either refractory to of at
least one anti-CD38 monoclonal antibody.

2. For participants in MTD/OBD cohort expansion and Phase 2 only: participant has
measurable disease.

3. During dose escalation only, participants not meeting the above criteria for
measurable disease should, at least, have measurable bone marrow plasmacytosis
(greater than or equal to [>=] 10 percent [%]) and/or plasmacytoma (>=1 centimeter
[cm] in diameter) detected by physical examination or imaging.

4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.

Exclusion Criteria:

1. Has polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes
(POEMS) syndrome, monoclonal gammopathy of unknown significance, smoldering myeloma,
solitary plasmacytoma, amyloidosis, Waldenstrom macroglobinemia or immunoglobulin M
(IgM) myeloma, or lymphoplasmacytic lymphoma (LPL).

2. Has sensory or motor neuropathy of National Cancer Institute Common Terminology
Criteria for AEs (NCI CTCAE) >=Grade 3.

3. Who have received autologous stem cell transplant (SCT) 60 days before first infusion
of TAK-573 or participants who have received allogeneic SCT 6 months before first
infusion. Graft-versus-host disease that is active or requires ongoing systemic
immunosuppression.

4. Has not recovered from adverse reactions to prior myeloma treatment or procedures
(chemotherapy, immunotherapy, radiation therapy) to NCI CTCAE less than or equal to
(<=) Grade 1 or baseline, except for sensory or motor neuropathy which should have
recovered to <=Grade 2 or baseline.

5. Has clinical signs of central nervous system (CNS) involvement of MM.