Poseida Provides Update on Phase 1 Study of P-BCMA-101 CAR-T Stem Cell Memory Product in Patients with Relapsed/Refractory Multiple Myeloma

Poseida Therapeutics Inc. – a clinical-stage biotechnology company translating best-in-class gene engineering technologies into lifesaving cell therapies – announced data results from the first eleven patients treated in its ongoing Phase 1 study of its P-BCMA-101 stem cell memory chimeric antigen receptor T-cell (CAR-T) product in relapsed/refractory multiple myeloma.

All eleven patients remain on study with seven of ten patients evaluable by International Myeloma Working Group (IMWG) criteria achieving at least a partial response. The remaining patient also demonstrated a robust response, but has oligosecretory disease and was only evaluable by PET. Importantly, unlike previous CAR-T therapies, P-BCMA-101 is demonstrating exceptional safety, with only one instance of suspected cytokine release syndrome (9%) that was minimal and short-lived. No patients demonstrated neurotoxicity and no patients required admission to an intensive care unit or treatment with tociluzimab or steroids, interventions typically required during episodes of CRS elicited by other CAR-T therapies. Enrollment continues in the higher dose cohorts.

P-BCMA-101 Clinical Data Presented as Late Breaker Today at CAR-TCR Summit

As of August 10th, 2018, eleven patients had been treated across three doses groups with average CAR-T cell doses of 51×106 (n=3), 152×106 (n=7), and 430×106 (n=1). These patients were heavily pretreated with a median of 6 prior therapies. The median age was 60, with 73% considered high-risk, including those with high-risk cytogenetics. Peak T-cell expansion was observed between days 14 and 21, which is more gradual than the 5-14 day peak expansion seen with other CAR-T therapies and was associated with less acute cytokine release and other adverse effects.

About P-BCMA-101

P-BCMA-101 is a CAR-T immunotherapy designed to supercharge a patient’s own T cells to safely and effectively eliminate tumor cells carrying B cell maturation antigen (BCMA), which is expressed on essentially all multiple myeloma tumor cells. P-BCMA-101 modifies a patient’s T cells using piggyBac™, which enables several desirable features, including:

  • T stem cell memory: P-BCMA-101 is comprised of a high level of stem cell memory T-cells (Tscm), resulting in unprecedented durability of response without re-administration of product in multiple preclinical studies.
  • Pure product: The addition of a human-derived positive selection gene results in a product that is composed almost entirely of modified CAR-T cells in contrast with lentivirus-based products, which are generally 5-30% pure. The higher purity of the product may also result in less toxicity.
  • Safety: piggyBac™ is non-oncogenic and has a safer integration profile than lentivirus. In addition, a human-derived safety switch is added such that P-BCMA-101 can be rapidly attenuated or eliminated if significant side effects occur.

For more details of the clinical trial click here.