Poseida Therapeutics Showcases CAR-T Reactivation in Relapsed Multiple Myeloma Case Study

Poseida Therapeutics, Inc., a biopharmaceutical company focused on allogeneic cell therapies and genetic medicines, has reported promising new data from a clinical trial involving their investigational therapy, P-BCMA-101. This therapy targets T stem cell memory (TSCM) cells and has shown significant potential in treating patients with relapsed multiple myeloma.

In a case study presented at the Society of Hematologic Oncology's Twelfth Annual Meeting, a 57-year-old female patient with relapsed multiple myeloma received the P-BCMA-101 therapy. TSCM cells, which are a key component of this therapy, demonstrate unique properties such as longevity, multipotency, and self-replication. These cells can engraft and differentiate, which is crucial for sustained therapeutic effects.

The patient's initial response to the treatment was a partial remission that eventually progressed to a stringent complete response, lasting nearly two years. However, after more than three years, the patient experienced a relapse. Subsequently, she received talquetamab, a T-cell engaging bispecific antibody. This treatment reactivated the CAR-T cells, leading to a phenomenon known as lymphocytosis, where high levels of P-BCMA-101 CAR-T cells were detected in the blood. This reactivation resulted in another complete remission, and the patient has now been off all anti-myeloma treatments and living in remission for over nine months following just one week of TCE therapy.

Thomas G. Martin, a Clinical Professor of Medicine and Director of Hematology at UCSF, commented on this outcome, emphasizing the unprecedented nature of CAR-T reactivation. He highlighted the potential of TSCM-based therapies to provide durable and long-term responses in treating myeloma.

Syed Rizvi, Chief Medical Officer of Poseida Therapeutics, echoed this sentiment, noting that the durable persistence and high TSCM content of P-BCMA-101 were key factors in its long-term efficacy. These attributes are consistent across Poseida's range of investigational CAR-T therapies, both autologous and allogeneic.

Poseida's P-BCMA-ALLO1, an allogeneic CAR-T therapy targeting BCMA, is also being evaluated for relapsed/refractory multiple myeloma. This therapy uses T cells derived from healthy donors rather than the patients themselves. The company plans to share new clinical data about P-BCMA-ALLO1 at the International Myeloma Society's Annual Meeting in Rio de Janeiro and has further updates scheduled for later in the year.

Poseida has transitioned its focus from autologous to allogeneic approaches in cell therapy, believing that this method offers a more scalable and accessible treatment option. Insights gained from their autologous programs have been instrumental in developing their allogeneic pipeline.

P-BCMA-ALLO1 has shown promising results in early-phase clinical trials and has received Orphan Drug Designation from the U.S. Food and Drug Administration for treating multiple myeloma. This designation underscores its potential to meet significant unmet medical needs.

Poseida Therapeutics continues to advance its pipeline of allogeneic CAR-T cell therapies, leveraging proprietary technologies such as the non-viral piggyBac DNA Delivery System and the Cas-CLOVER Site-Specific Gene Editing System. These innovations are designed to enhance the efficacy, safety, and manufacturability of their treatments.

In partnership with Roche and Astellas, Poseida aims to unlock the full potential of cell therapies for cancer and rare diseases, providing new hope for patients with high unmet medical needs.