BOSTON—Early results from a phase 1 trial suggest the chimeric antigen receptor (CAR) T-cell therapy P-BCMA-101 can produce responses in patients with relapsed/refractory multiple myeloma (MM).
All 11 patients treated have experienced some clinical response, with 8 patients achieving a partial response (PR) or better.
The most common adverse events were neutropenia and thrombocytopenia. One patient was suspected to have cytokine release syndrome, but the condition resolved without use of tociluzimab or steroids.
These results were presented at the 2018 CAR-TCR Summit by Eric Ostertag, MD, PhD, chief executive officer of Poseida Therapeutics Inc., the company developing P-BCMA-101.
Dr. Ostertag presented data on 11 patients with heavily pretreated MM. They had a median of six prior therapies. Their median age was 60, and 73% were considered high risk.
Prior to receiving P-BCMA-101, patients received conditioning with fludarabine (30 mg/m2) and cyclophosphamide (300 mg/m2) for 3 days.
Patients were then treated across three dose groups with average CAR T-cell doses of 51×106 (n=3), 152×106 (n=7), and 430×106 (n=1).
As of August 10, 2018, all 11 patients were still on study.
There were no dose-limiting toxicities. Eight patients developed neutropenia, and 5 had thrombocytopenia.
Researchers suspected cytokine release syndrome in one patient, but the condition resolved without tociluzimab or steroid treatment. There was no neurotoxicity reported, and none of the patients required admission to an intensive care unit.
All patients showed improvement in biomarkers following treatment.
Ten patients were evaluable for response by International Myeloma Working Group criteria. Seven of these patients achieved at least a PR, including very good partial responses (VGPRs) and stringent complete response (CR).
The eleventh patient also responded to treatment, but this patient has oligosecretory disease and was only evaluable by PET. The patient had a near-CR by PET.
Poseida Therapeutics would not disclose additional details regarding how many patients achieved a PR, VGPR, or CR, but the company plans to release more information on response at an upcoming meeting.
“The latest data results show that P-BCMA-101 induces deep responses in a heavily pretreated population with relapsed/refractory multiple myeloma, with some patients reaching VGPR and even stringent CR at early efficacy assessments,” Dr. Ostertag said.
“We believe our advantages of a purified product, where all cells express the CAR molecule, and a product with high levels of stem cell memory T cells, producing a more gradual and prolonged immune response against tumor cells, provide a significantly better therapeutic index when compared with other CAR-T therapeutics. We are also encouraged that P-BCMA-101 is demonstrating significant efficacy even at doses that have been ineffective for other anti-BCMA CAR-T therapies and that our response rates continue to improve as the dose increases.”
This study (NCT03288493) is funded by the California Institute for Regenerative Medicine and Poseida Therapeutics.