A Phase 1/2 Open-label Study to Investigate the Safety and Tolerability, Efficacy, Pharmacokinetics, and Immunogenicity of Modakafusp Alfa (TAK-573) as a Single Agent in Patients With Relapsed Refractory Multiple Myeloma

⁃ For Parts 1 and 2:

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

• In need of additional myeloma therapy as determined by the investigator.

• Has previously received at least 3 lines of myeloma therapy (for example, containing an Immunomodulatory imide drug \[IMiD\], a proteasome inhibitor \[PI\], an alkylating agent, and/or an anti-CD38 as single agents or in combination).

• Is either refractory to or intolerant of at least 1 PI and a least 1 IMiD.

⁃ For Part 3:

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

∙ In need of additional myeloma therapy as determined by the investigator.

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

‣ Is refractory to at least 1 IMiD (ie, lenalidomide or pomalidomide \[thalidomide excluded\]), at least 1 PI (ie, bortezomib, ixazomib, or carfilzomib), and refractory to at least 1 anti-CD38 antibody (ie, daratumumab or isatuximab) and has demonstrated disease progression with the last therapy. Participants who are primary refractory, meaning they never achieved at least a MR with any previous treatment line, are not eligible.

⁃ For participants in Part 2 and 3 only: Measurable disease is defined as :

• Serum M-protein ≥500 mg/dL (≥5 g/L)

∙ Urine M-protein ≥200 mg/24 hours.

∙ Serum free light chain (FLC) assay, with involved FLC level ≥10 mg/dL (≥100 mg/L) provided serum FLC ratio is abnormal.

⁃ During Part 1 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.

⁃ Eastern Cooperative Oncology Group (ECOG) performance status of ≤2.