Dose Escalation Study of JNJ-64407564 in Participants With Relapsed or Refractory Multiple Myeloma

The study will be conducted in 2 parts, separately for intravenous (IV) and subcutaneous (SC)
administration: dose escalation and dose expansion. The study will evaluate safety,
tolerability, pharmacokinetics and preliminary antitumor activity of JNJ-64407564
administered to adult participants with relapsed or refractory multiple myeloma. The overall
safety of the study drug will be assessed by physical examinations, Eastern Cooperative
Oncology Group performance status, laboratory tests, vital signs, electrocardiograms, adverse
event monitoring, and concomitant medication usage. Disease evaluations will include
peripheral blood and bone marrow assessments at screening (performed within 28 days) and to
confirm stringent complete response (sCR), complete response (CR), or relapse from CR. The
end of study (study completion) is defined as the last study assessment for the last
participant in the study.

Inclusion Criteria:

- Documented initial diagnosis of multiple myeloma according to International Myeloma
Working Group (IMWG) diagnostic criteria

- Participants with measurable multiple myeloma who have progressed on, or could not
tolerate, all available established therapies

- Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1

- Women of childbearing potential must have a negative pregnancy test at screening and
prior to the first dose of study drug using a highly sensitive pregnancy test either
serum (Beta human chorionic gonadotropin [beta-hCG]) or urine

- Sign an informed consent form (ICF) indicating that he or she understands the purpose
of and procedures required for the study, and is willing to and able participate in
the study. Consent is to be obtained prior to the initiation of any study-related
tests or procedures that are not part of standard-of-care for the participant's
disease

Exclusion Criteria:

- Vaccinated with live, attenuated vaccine within 4 weeks or as recommended by the
product manufacturer prior to the first dose, during treatment, or within 100 days of
the last dose of JNJ-64407564

- Toxicities from previous anticancer therapies should have resolved to baseline levels
or to Grade 1 or less except for alopecia or peripheral neuropathy

- Received a cumulative dose of corticosteroids equivalent to greater than or equal to (
>=) 140 milligram (mg) of prednisone within the 14-day period before the first dose of
study drug

- An allogenic stem cell transplant within 6 months before first dose of study drug.
Participants who received an allogeneic transplant must be off all immunosuppressive
medications for 6 weeks without signs of graft-versus-host disease (GVHD); and/or an
autologous stem cell transplant less than or equal to (<=) 12 weeks before first dose
of study drug

- Documented history of central nervous system (CNS) involvement or exhibits clinical
signs of meningeal involvement of multiple myeloma. If either is suspected, whole body
magnetic resonance imaging (MRI) and lumbar cytology are required