TalquetamabA Study to Evaluate Preventive Treatments for GPRC5D-related Oral Events

Participants with relapsed or refractory multiple myeloma (RRMM) who are triple-class exposed (previously exposed to at least 1 proteasome inhibitor \[PI\], 1 immunomodulatory drug(s) \[IMiD\]), and an anti-CD38 monoclonal antibody \[mAb\]) will be treated with talquetamab subcutaneously until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of talquetamab, or end of study, whichever occurs first.

Participants with RRMM who are triple-class exposed (previously exposed to at least 1 PI, 1 IMiD, and an anti-CD38 mAb) will receive prophylaxis A along with talquetamab therapy. Participants will start the assigned prophylaxis 7 days before starting talquetamab treatment. After step-up dosing of talquetamab therapy, participants will be treated with talquetamab with prophylaxes for up to 12 months during prophylaxis treatment phase (if there are clinical benefits prophylaxis treatment can continue beyond 12 months, at the treating physician's discretion, after consultation with sponsor). The Talquetamab treatment phase will continue from Cycle 1 Day 1 (C1D1) until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of talquetamab, or end of study, whichever occurs first.

Participants with RRMM who are triple-class exposed (previously exposed to at least 1 PI, 1 IMiD, and an anti-CD38 mAb) will receive prophylaxis B along with talquetamab therapy. Participants will start the assigned prophylaxis 7 days before starting talquetamab treatment. After step-up dosing of talquetamab therapy, participants will be treated with talquetamab with prophylaxes for up to 12 months during prophylaxis treatment phase (if there are clinical benefits prophylaxis treatment can continue beyond 12 months, at the treating physician's discretion, after consultation with sponsor). The Talquetamab treatment phase will continue from C1D1 until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of talquetamab, or end of study, whichever occurs first.

Participants with RRMM who are triple-class exposed (previously exposed to at least 1 PI, 1 IMiD, and an anti-CD38 mAb) will receive prophylaxis C along with talquetamab therapy. Participants will start the assigned prophylaxis 7 days before starting talquetamab treatment. After step-up dosing of talquetamab therapy, participants will be treated with talquetamab with prophylaxes for up to 12 months during prophylaxis treatment phase (if there are clinical benefits prophylaxis treatment can continue beyond 12 months, at the treating physician's discretion, after consultation with sponsor). The Talquetamab treatment phase will continue from C1D1 until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of talquetamab, or end of study, whichever occurs first.

Participants with RRMM who are triple-class exposed (previously exposed to at least 1 PI, 1 IMiD, and an anti-CD38 mAb) will receive prophylaxis D along with talquetamab therapy. Participants will start the assigned prophylaxis 1 day before starting talquetamab treatment. After step-up dosing of talquetamab therapy, participants will be treated with talquetamab with prophylaxes for up to 12 months during prophylaxis treatment phase (if there are clinical benefits prophylaxis treatment can continue beyond 12 months, at the treating physician's discretion, after consultation with sponsor). The Talquetamab treatment phase will continue from C1D1 until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of talquetamab, or end of study, whichever occurs first.

Participants with RRMM who are triple-class exposed (previously exposed to at least 1 PI, 1 IMiD, and an anti-CD38 mAb) will receive single step-up dose of ramantamig subcutaneously followed by the treatment dose until disease progression, death, unacceptable toxicity, withdrawal of consent, discontinuation of ramantamig, or end of study, whichever occurs first.

Talquetamab will be administered subcutaneously.

Prophylaxis A will be administered orally.

Prophylaxis B will be administered orally.

Prophylaxis C will be administered orally.

Prophylaxis D will be administered topically.

Ramantamig will be administered subcutaneously.