A phase 1/2, open-label, multicenter, dose escalation and cohort expansion study of the safety and efficacy of anti-CD70 allogeneic CRISPR-Cas9–engineered T cells (CTX131) in adult patients with relapsed or refractory solid tumors.

TPS2676 Background: CD70, a type II transmembrane protein and member of the tumor necrosis factor (TNF) receptor family, demonstrates high expression across multiple malignancies making it an attractive target for chimeric antigen receptor (CAR) T cell therapy. CD70 is expressed in 80% of clear cell renal cell carcinoma (ccRCC) and in 40-60% of cervical carcinoma (CC), esophageal carcinoma (EC), pancreatic adenocarcinoma (PAC), and pleural mesothelioma (PM) (1). CTX131 is a CD70-directed allogeneic CAR T cell investigational product manufactured ex vivo from healthy donor T cells using CRISPR/Cas9 technology. Genetic modifications in CTX131 include targeted insertion of a CD70-directed CAR construct, and targeted disruption of 5 loci: TRAC (to reduce risk of GvHD), B2M (to improve persistence in the allogeneic setting), CD70 (to reduce fratricide and improve anti-tumor function), TGFBR2 (to reduce immunosuppressive effect of TGFB in the tumor microenvironment), and Regnase-1 (to improve functional persistence) (2). Preclinical studies show the combination of TGFBR2 and Regnase-1 disruption in CTX131 works synergistically to enhance anti-tumor activity, inhibit tumor growth in xenograft mouse models, prolong survival, and increase central memory T cell populations (3). Methods: We are conducting a phase 1/2 study in patients (pts) with unresectable or metastatic ccRCC, CC, EC, PAC, and PM. Part 1 is a dose escalation with two separate cohorts, one for ccRCC pts and another for CC, EC, PAC, and PM pts. Part 1 ccRCC cohort began recruiting in 2023. Part 2 is a single-arm expansion of disease-specific cohorts. Key eligibility criteria include at least one prior line of standard treatment, ECOG status 0-1, evaluable disease per RECIST v1.1 (or modified RECIST1.1 for PM), adequate hematologic and organ function, and availability of tumor tissue for CD70 IHC. Key exclusion criteria include prior treatment with CD70-targeting agents and active CNS metastasis. Pts will receive standard lymphodepleting chemotherapy with fludarabine 30 mg/m 2 and cyclophosphamide 500 mg/m 2 daily x 3 days followed by CTX131 IV infusion at doses ranging from 30-900 million cells in 4 dose level cohorts. Redosing with CTX131 is permitted. For Part 1, the primary endpoint is DLTs with secondary endpoints including ORR, DOR, PFS, and OS. For Phase 2 the primary endpoint is ORR by IRC assessment. The trial is currently open with enrollment ongoing. 1. Flieswasser et. al. 2019. 2. Mai et. al. 2023. 3. Terrett 2023. Clinical trial information: NCT05795595 .