As of December 22, 2022, 46 pts received PHE885 at the following doses: 2.5e6 (n=4), 5e6 (n=13), 10e6 (n=20), 14.3e6 (n=1), and 20e6 (n=8) CAR T cells. PHE885 was manufactured for 61% of pts at a single academic institution; these pts proceeded from apheresis to LD in a median of 16 days. Median age at enrollment was 65 y (range [R] 45-81), median prior lines of tx was 4 (R 2-10). 37% of pts had extramedullary disease; 96% were triple refractory. Despite aggressive disease, only 28% of pts required bridging chemotherapy, predominantly influenced by quick production time. 96% of pts experienced any gr cytokine release syndrome (CRS); 11% had gr 3 CRS. Median time to CRS onset was 8 (R 2-16) days and median duration was 4 (R 1-19) days. Immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 22% of pts; 7% had gr 3 ICANS. Dose limiting toxicities were experienced by 13% of pts and included gr 4 neutropenia, gr 4 lipase increase, gr 3 serum amylase increase, gr 3 neurotoxicity, gr 3 transaminitis, and gr 3 ejection fraction reduction. The most common tx-related gr ≥3 AEs included anemia (54%), neutropenia (50%), and thrombocytopenia (37%). Geo-mean peak PHE885 expansion (Cmax) was 276,000 copies/µg by qPCR and 70.6% of CD3+ T cells by flow cytometry (n=41). The PHE885 transgene was detected in 13/14 (93%) pts at 6 mo and 5/7 (71%) at 12 mo post infusion. T cells with early memory phenotype were preserved in the final product and persisted in pts post infusion. In 43 efficacy-evaluable pts, the ORR was 98%. At 10e6 dose (n=19), ORR was 100% and CRR was 42% (median follow-up of 4.9 mo [R 1.4-11.8]); 60% of 10 evaluable pts were MRD negative at 10-5 by NGS. Initial efficacy data at 20e6 and longer follow-up at active doses will also be presented.

PHE885, an investigational, autologous BCMA-directed CAR-T cell therapy developed using the T-Charge platform, demonstrated promising results in patients with relapsed or refractory multiple myeloma in a first-in-human Phase I, multicenter, dose-escalation study. Fifteen patients were evaluated for efficacy and safety and the fixed doses received were 2.5×106 (n=4), 5×106 (n=10) and 14.3×106 CAR-T cells (n=1). Although the follow-up period was brief, PHE885 shows encouraging initial clinical activity with a best overall response of 100% for patients receiving the 5×106 or 14.3×106 CAR-T cell dose, with responses deepening over time. With a median follow-up of 3.5 months, eight of 15 patients had ongoing responses at the time of data cutoff. Of the evaluable patients at three months post administration, 34% (2/6) were MRD-negative by next-generation sequencing (NGS) at 10-6; 43% (3/7) were MRD-negative at 10-5.

All patients experienced CRS with two patients experiencing grade ≥3 CRS. No patients experienced grade 4 or 5 CRS. All neurotoxicity events (n=4) were nonserious, grade 1-2, reversible, and temporally associated with CRS.