On February 16, 2023 Bellicum Pharmaceuticals, Inc. (NASDAQ:BLCM), a leader in developing novel, controllable cellular immunotherapies for cancers, reported its early Phase 1 results for BPX-601 at the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Genitourinary Cancers Symposium (ASCO GU) in San Francisco and virtually (Press release, Bellicum Pharmaceuticals, FEB 16, 2023, View Source [SID1234627293]). The poster titled "Early Results from a Phase 1, Multicenter Trial of PSCA-Specific GoCAR T Cells (BPX-601) in Patients with Metastatic Castration-Resistant Prostate Cancer (mCRPC)" presents initial data from the first two cohorts (n=8) treated with BPX-601. These interim results demonstrated preliminary efficacy of BPX-601 PSCA-directed GoCAR-T cells in combination with rimiducid in heavily pre-treated patients.

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"We believe these encouraging initial clinical results in mCRPC support the potential of BPX-601 and the GoCAR-T platform," stated Rick Fair, President and Chief Executive Officer, Bellicum Pharmaceuticals. "We designed the GoCAR-T platform to enhance immune cell proliferation and persistence, resist exhaustion, and override key inhibitory factors in the solid tumor microenvironment. We are excited to share data supporting the clinical activity of the first GoCAR-T program early in dose escalation, and look forward to reporting additional results as we work to optimize the doses of BPX-601 cells and rimiducid."

Initial Results from Ongoing BPX-601 Phase 1 Trial

These initial data from 2 cohorts consisted of 8 patients who received lympodepleting chemotherapy (fludarabine + cyclophosphamide) followed by a single dose of 5×106 BPX-601 cells/kg and single (n=3) or weekly (n=5) doses of 0.4 mg/kg rimiducid beginning 7 days following the cell infusion. GoCAR-T cells are designed to function optimally with repeat dosing of rimiducid to induce the co-activation molecules MyD88 and CD40. The primary observations were:

Four of eight (50%) patients achieved a PSA50 response, three of whom achieved a PSA90 response.
Of the six patients with soft tissue (visceral and/or lymph node) disease, two achieved partial responses by RECIST v1.1, one of which was confirmed.
Of the two patients with bone-only disease, one patient achieved a PSA90 response with decreased enhancement of bone lesions observed on bone scan.
The most common grade 3+ adverse events were myelosuppression, characteristic of the lymphodepleting chemotherapies used in CAR-T studies. Two patients experienced Grade 3 cytokine release syndrome (CRS). One patient experienced Grade 4 immune effector cell neurotoxicity syndrome (ICANS) with concurrent hemophagocytic lymphohistiocytosis (HLH); while ICANS improved to grade 1 with standard of care treatment and withholding of subsequent doses of rimiducid, the patient died on study day 20 due to sepsis. Interpretation of immune-mediated adverse events in this patient is confounded by concurrent sepsis.
Consistent BPX-601 cell expansion across patients was observed, with persistence of BPX-601 cells detected in peripheral blood over 200 days.
Evidence of inducible MyD88/CD40 (iMC) activation was observed, with serum levels of pro-inflammatory T cell cytokines (including IFNγ, TNFα, IL-6 and IP-10) rising after administration of rimiducid and subsequently falling prior to subsequent doses.
BPX-601 cell infiltration in PSCA-positive tumor was observed.
The trial continues to enroll patients. The next cohorts in the Phase 1 trial will explore higher doses of rimiducid, which in non-clinical studies have been shown to increase GoCAR-T persistence, enhance pro-inflammatory cytokine production, and improve anti-tumor efficacy.

About BPX-601

BPX-601, the company’s first GoCAR-T product candidate, incorporates iMC, Bellicum’s inducible co-activation domain. iMC (inducible MyD88/CD40) is designed to provide a powerful boost to T cell proliferation and persistence, production of immunomodulatory cytokines and enable the CAR-T to override key immune inhibitory mechanisms, including PD-1 and TGF-beta. BPX-601 is being evaluated as a treatment for metastatic castration resistant prostate cancer (mCRPC) expressing prostate stem cell antigen (PSCA).