A multicentre Phase I clinical trial demonstrates manufacturing feasibility, safety and activity of novel humanized BCMA-directed CAR-T cell therapy.

Abstract Background: BCMA directed CAR-T cell therapies have shown durable responses and improved outcomes in relapsed/refractory multiple myeloma (RRMM). We designed and developed novel humanized BCMA-directed CAR-T cell therapy (hBCMA) with robust activity and low toxicities in preclinical settings (Khan et al., ASH 2024). Here, we report the manufacturing feasibility and Phase I clinical study to evaluate the safety and activity of hBCMA in RRMM in India (CTRI/2025/01/079364). Methods: Phase I trial with primary aim to assess safety by determining the incidence of adverse events and dose-limiting toxicities (DLTs) was initiated on 24/01/2025 upon obtaining regulatory approvals in India. Patients aged 18 and above with RRMM who have received at least two prior lines of therapy or are double refractory to IMiD and PI combination, with measurable disease were enrolled in the study. Prior exposure to BCMA-targeted therapy, ongoing immunosuppressants, history of allogeneic bone marrow transplantation, significant cardiac or CNS issues, and active infections were the exclusion criteria. Dose escalation study was planned at three dose levels (DL): 0.5-2x106 (DL1), 2-5x106 (DL2), 5-10x106 (DL3) CAR-T cells/kg. Leukapheresis was performed with a target collection of 2 × 10⁹ ALC and transported to a centralized manufacturing facility within 24 hours at 2–8 °C. T cells were enriched and activated using magnetic beads, followed by viral transduction and product harvest upon achieving the target CAR-T cell dose using semi-automated process. Patients were subjected to a lymphodepleting regimen with Cy (300 mg/m2, d-5 to d-3) and Flu (30 mg/m2, d-5 to d-3) prior to the CAR-T cells infusion (d0). The toxicity was graded by ASCT guidelines and CTCAE 5.0 and efficacy was assessed by the IMWG Uniform Response Criteria for Multiple Myeloma. Results: As of 31st July 2025, six patients were consented and underwent leukapheresis (DL1 n=4; DL2 n=2) for hBCMA CAR-T cells manufacturing. The median age of the cohort was 57(43-65) years with median lines of therapy of 5(3-7). Leukapheresis yielded sufficient cells, with a median of 2.5 × 10⁹ CD3⁺ cells collected per run. The required dose was achieved by 6-8 days with median CAR expression of 42% (range 19-52) from all patients (100% manufacturing success rate). The final product showed effective distribution of less differentiated T cells (median Naïve (CD45RA+CCR7+): 22%, range 5-24 and Central memory (CD45RA-CCR7+): 21%, range 14-22) suggestive of superior quality immunophenotype of CAR-T cells. One patient was withdrawn post leukapheresis due to deterioration in performance status prior to infusion. Three patients received infusion of hBCMA CAR-T cells at DL1 and one patient received at DL2. The median vein-to-vein time was 26 days(range 19-36). Bridging therapy was given to 50% (3/6) patients. The patients with DL1 were evaluable for safety and early efficacy. DL2 cohort was under evaluation and updated data will be presented at the meeting. Cytopenia was most common toxicity with incidence of Grade 3-4(G3-4) thrombocytopenia (n=2/3), neutropenia (n= 3/3), and anaemia (n=2/3). Cytokine release syndrome (CRS) was reported in 67% (2/3) patients. None of the patients developed G3/4 CRS and ICANS of any grade. At one month post infusion, responses were sCR (n=2) and PR (n=1). The patients maintained response at last follow up (median follow up: 62 days (28-90)). No dose limiting toxicity or treatment related deaths were reported. In vivo CAR expansion was evaluated by qPCR at Day 7, Day 14 and Day 28 until date cut off. Peak expansion was observed on Day 14 (median: 2.6 X 104 CAR copy number/µg gDNA) and maintained CAR persistence at Day 28 (median: 1.4 X 104 CAR copy number/µg gDNA). Conclusion: Early results from the Phase I study demonstrates that low doses of hBCMA CAR-T cells are safe, active, with rapid in vivo expansion in patients with RRMM. The study also indicates the manufacturing feasibility of CAR-T cells from heavily pretreated RRMM patients.