A Study of JNJ-79635322 in Participants With Relapsed or Refractory Multiple Myeloma or Previously Treated Amyloid Light-chain (AL) Amyloidosis

The primary purpose of this study is to identify the recommended phase 2 dose (RP2D\[s\]) and schedule(s) to be safe for JNJ-79635322 in Part 1 (dose escalation), and to characterize the safety and tolerability of JNJ-79635322 at the RP2D(s) selected and in disease subgroups in Part 2 (dose expansion).

Inclusion Criteria: For participants with relapsed or refractory multiple myeloma: * Have a documented initial diagnosis of multiple myeloma according to International Myeloma Working Group (IMWG) diagnostic criteria * Part 1: Have relapsed or refractory disease, have been treated with a proteasome inhibitor, immunomodulatory drug (IMiD) agent, and an anti-CD38-based therapy for the treatment of multiple myeloma (MM),and should have been treated with at least 3 prior lines of therapy, or are refractory to proteosome inhibitor, IMiD agent, and an anti-CD38-based therapy regardless of prior lines of therapy, Part 2: Have relapsed or refractory disease, have been treated with a PI, IMiD and an anti-CD38 based therapy * Must have an Eastern Cooperative Oncology Group (ECOG) status of 0 or 1 * Have measurable disease at screening as defined by at least 1 of the following: a) Serum M-protein level greater than or equal to (\>=) 0.5 grams per deciliter (g/dL); or b) Urine M-protein level \>=200 milligrams (mg)/24 hours; or c) Light chain multiple myeloma: Serum immunoglobulin (Ig) free light chain (FLC) \>=10 milligrams per deciliter (mg/dL) and abnormal serum Ig kappa lambda FLC ratio; d) For participants without measurable disease in the serum, urine, or involved FLC, presence of 1 or more focus of extramedullary disease (EMD) which meets the following criteria: extramedullary plasmacytoma not contiguous with a bone lesion, at least 1 lesion \>=2 centimeter \[cm\] (at its greatest dimension) diameter on whole body Positron Emission Tomography and Computed Tomography (PET-CT) Scans (or whole body magnetic resonance imaging \[MRI\] approved by sponsor), and not previously radiated (Part 2C participants are not required to have measurable disease) For participants with previously treated AL amyloidosis: * Initial histopathological diagnosis of amyloidosis * Participant who is not a candidate for available AL amyloidosis therapy with established clinical benefit and should have received at least 3 cycles of 1 prior line of therapy or a total of at least 2 cycles of 2 or more prior lines of therapy for AL amyloidosis * Measurable disease at screening defined by at least 1 of the following: serum involved free light chain (iFLC) \>=50 mg/L or difference between involved and uninvolved free light chains (dFLC) \>=50 mg/L, or serum m-protein \>= 0.5 g/dL * One or more organs impacted by systemic AL amyloidosis * Left ventricular ejection fraction (LVEF) \>=45% Exclusion Criteria: For participants with relapsed or refractory multiple myeloma: * Central Nervous System (CNS) involvement or clinical signs of meningeal involvement of multiple myeloma. If either is suspected, brain magnetic resonance imaging (MRI) and lumbar cytology are required * Active plasma cell leukemia, Waldenstrom's macroglobulinemia, POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes), or primary light chain amyloidosis * Received a cumulative dose of corticosteroids equivalent to greater than (\>) 140 mg of prednisone within the 14-day period before the start of study treatment administration * Prior antitumor therapy as follows, in the specified time frame prior to the first dose of study treatment: (proteasome inhibitor \[PI\] therapy or radiotherapy within 14 days, immunomodulatory drug (IMiD) agent therapy within 7 days, gene-modified adoptive cell therapy within 90 days \[not applicable for Part 2C participants\], or CD3-redirecting therapy within 21 days\[not applicable for Part 2B or 2C participants\]) * Prior allogeneic transplant within 6 months before the start of study treatment administration or autologous transplant within 12 weeks before the start of study treatment administration * Live, attenuated vaccine within 4 weeks before the first dose of study treatment * Non-hematologic toxicity from prior anticancer therapy that has not resolved to baseline levels or to Grade less than or equal to (\