Subjects are enrolled in this study following completion or early discontinuation from a Poseida sponsored or supported study of P-BCMA-101 T cells and will be followed for a total of 15 years post treatment from the last P-BCMA-101 treatment. Subjects will be monitored for safety and efficacy to assess the risk of delayed adverse events (AEs) and assess long-term efficacy, and PK and quantification of P-BCMA-101 T cells. Rimiducid may be administered as indicated.

Per Health Authorities guidelines for gene therapy medicinal products that utilize integrating vectors (FDA, 2006; Guidance for Industry, Gene Therapy Clinical Trials-Observing Subjects for Delayed Adverse Events), long term safety and efficacy follow up of treated subjects is required. Subjects are enrolled in this study following completion or early discontinuation from a Poseida sponsored or supported study of P-BCMA-101 T cells and will be followed for a total of 15 years post treatment from the last P-BCMA-101 treatment. Subjects will be monitored for safety and efficacy to assess the risk of delayed adverse events (AEs) and assess long-term efficacy, and PK and quantification of P-BCMA-101 T cells. Rimiducid may be administered as indicated.

Study visits Subjects will only enter this protocol after completing or discontinuing from their primary P-BCMA-101 protocol.

Once enrolled in this protocol a subject will return for regular follow-up depending on when they last received P-BCMA-101 on their primary protocol:

• Every 3 months until the end of the first year after P-BCMA-101 treatment
• Every 6 months until the end of the third year after P-BCMA-101 treatment
• Then yearly until the end of the 15th year after P-BCMA-101 treatment (ie. if a subject discontinues from their primary protocol 2 years after receiving P-BCMA-101, they will be entering this study at the beginning of the 3rd year, and will remain on this study for 13 years).

Subjects will undergo serial assessment of safety, chemistry, hematology, and disease response as specified in the Schedule of Events. Subjects will further undergo a physical exam and medical history, and anti-myeloma medications, related AEs, new malignancies, new or exacerbated clinically significant neurologic, hematologic, rheumatologic or other autoimmune disorders will be recorded. After progressive disease (PD) has been confirmed for a subject after P-BCMA-101 administration, visits may be performed remotely (AEs collected by telephone and laboratory studies completed at a local facility).

Inclusion Criteria:

• Subjects who have received P-BCMA-101 and completed or discontinued early from a Poseida sponsored treatment protocol.
• Subject has provided informed consent.

Exclusion Criteria:

• None