Abstract CT002: CTX130 Allogeneic CRISPR-Cas9-engineered Chimeric Antigen Receptor (CAR) T Cells in Patients with Advanced Clear Cell Renal Cell Carcinoma: Long-term Follow-Up and Translational Data from the Phase 1 COBALT-RCC Study

Abstract Background: The mainstay of therapy for clear cell renal cell carcinoma (ccRCC), the most prevalent subtype of kidney cancer, includes checkpoint inhibitors (CPIs) and tyrosine kinase inhibitors (TKIs). However, once patients progress on these drug classes, outcomes are poor. Here, we report durable response and stability observed in a Phase 1 dose-escalation study of CTX130™, a CD70-targeting allogeneic CAR T cell therapy in patients with ccRCC. Methods: In this phase I study, patients were recruited from sites in the United States, Europe and Australia. Key eligibility included advanced ccRCC with prior receipt of at least one CPI and TKI. After receipt of standard lymphodepletion with fludarabine and cyclophosphamide for 3 days (dosed at 30 mg/m2 and 500 mg/m2, respectively), patients received infusion of CTX130. Results: Among the 16 patients enrolled and treated in dose escalation, the median age was 63 (range, 53-77) and all were stage IV at the time of enrollment. Patients had received a median of 3 prior lines of therapy (range, 1-6). Doses ranging from 3 × 107 to 9 × 108 CAR T cells were administered, and no dose-limiting toxicities were encountered. Cytokine release syndrome (CRS) was observed in 8 patients (50%); all events were grade 1 or 2. Infections were observed in 4 patients (25%), all deemed to be unrelated to CTX130. No hemophagocytic lymphohistiocytosis, graft-versus host disease or treatment-related neurotoxicity was observed. As of Oct 9, 2023, 1 patient (6.3%) achieved a complete response (CR) (now extending over 36+ months) and 12 additional patients (75%) achieved stable disease (SD) (1 patient in excess of 18 months), reflecting a disease control rate (CR/partial response/SD) of 81.3%. Immunohistochemical staining of baseline and archival tissues show an initial median CD70 expression level of 100% (range, 1-100%), with no substantial antigenic loss at sequential biopsies performed at day 42. Using digital droplet PCR assays of the CAR construct, we assessed expansion. CTX130 was detected in 20 minutes after infusion, declined to a nadir 2-3 days later, followed by rapid expansion between days 7 and 15. In general, expansion increased at each dose level. Conclusions: Updated results from the COBALT-RCC study reinforce both the encouraging antitumor activity and exceptional safety profile of CTX130. The durable CR, now in excess of 3 years, reflects the first and longest seen with allogeneic CAR T cell therapy in refractory solid tumors. A study of CTX131™ (building on CTX130 with CRISPR edits to enhance potency and persistence) is ongoing. Citation Format: Sumanta Kumar Pal, Ben Tran, John B. Haanen, Michael Hurwitz, Adrian Sacher, Neeraj Agarwal, Nizar Tannir, Elizabeth Budde, Simon Harrison, Sebastian Klobuch, Sagar S. Patel, Mary-Lee Dequeant, Qiuling Ally He, Alissa Keegan, Henia Dar, Anna Ma, PK Morrow, Samer A. Srour. CTX130 allogeneic CRISPR-Cas9-engineered chimeric antigen receptor (CAR) T cells in patients with advanced clear cell renal cell carcinoma: Long-term follow-up and translational data from the phase 1 COBALT-RCC study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT002.