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

The main aims of this 3-part study are as follows:

Part 1: To determine any side effects from modakafusp alfa single treatment and how often
they occur. The dose of modakafusp alfa will be increased a little at a time until the
highest dose that does not cause harmful side effects is found.

Part 2: To assess clinical activity of one or more dosing schedules of modakafusp alfa alone
in participants with relapsed/refractory multiple myeloma. Dexamethasone standard dose will
be administered with one or more selected dose of modakafusp alfa in selected group of
participants.

Part 3: To find the optimal dose with the more favorable risk-benefit profile of modakafusp
alfa.

Participants will receive modakafusp alfa at one of two doses which will be given through a
vein.

Inclusion Criteria:

For Parts 1 and 2:

1. 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:

1. 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.

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

1. Serum M-protein ≥500 mg/dL (≥5 g/L)

2. Urine M-protein ≥200 mg/24 hours.

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

3. 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.

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

Exclusion Criteria:

For Parts 1 and 2:

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

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

3. 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.

4. Has clinical signs of central nervous system involvement of MM.

For Part 3:

- Hepatitis B virus (HBV) or hepatitis C virus (HCV) infection. Seropositive for
hepatitis B (defined by a positive test for hepatitis B surface antigen [HBsAg].
Participants with resolved infection (that is, participants who are HBsAg negative but
positive for antibodies to hepatitis B core antigen [anti-HBc] and/or antibodies to
hepatitis B surface antigen [anti-HBs]) must be screened using real-time polymerase
chain reaction (PCR) measurement of HBV DNA levels. Those who are PCR positive will be
excluded.

- In addition to the above criteria, participants must not have plasma cell leukemia or
have had primary refractory MM, current central nervous system involvement of MM,
myelodysplastic syndrome, myeloproliferative syndrome, or have had a second malignancy
within the previous 3 years, except treated basal cell or localized squamous skin
carcinomas, localized prostate cancer, cervical carcinoma in situ, resected colorectal
adenomatous polyps, breast cancer in situ, or other malignancy for which the
participant is not on active anticancer therapy.