A Dose-escalation Study to Evaluate the Safety and Clinical Activity of PBCAR269A, With or Without Nirogacestat, in Study Participants With Relapsed/Refractory Multiple Myeloma

This is a multicenter, nonrandomized, open-label, parallel assignment, single-dose, dose-escalation, and dose-expansion study to evaluate the safety and clinical activity of PBCAR269A, with or without nirogacestat, in adults with r/r MM. Before initiating the study treatment PBCAR269A, all study participants will be administered lymphodepletion chemotherapy. The initial lymphodepletion chemotherapy regimen will be composed of fludarabine and cyclophosphamide during the Screening Period. Study subjects in Cohort B will also receive nirogacestat. On Day 0 of the Treatment Period, study participants will receive a single intravenous (IV) infusion of PBCAR269A. All subjects are monitored during the treatment period through Day 28. All subjects who receive a dose of PBCAR269A, with or without nirogacestat, will be followed in a separate long-term follow-up (LTFU) study for 15 years after exiting this study.