Abstract 2746: Preclinical activity and manufacturing feasibility of genetically modified PDCD-1 knockout (KO) tumor-infiltrating lymphocyte (TIL) cell therapy

Background: Adoptive cell therapy with autologous TIL has demonstrated an objective response rate (ORR) of 36% in the post-immune checkpoint inhibitor (ICI) setting in patients (pts) with advanced/unresectable melanoma (Sarnaik JCO 2021), while in ICI-naïve pts who received early-line combination of TIL and pembrolizumab, the ORR was 60%, with a 30% CR rate (O’Malley SITC 2021). Although effective, anti-PD-1 therapy is limited by poor penetration into the tumor, internalization, and endocytic clearance, in contrast with TIL, which overcome this inherent limitation. PDCD-1 gene inactivation (PD-1 KO) may enhance TIL cell therapy efficacy in the post-ICI setting and abrogate the need for systemic anti-PD-1 therapy in ICI-naïve pts. In preclinical studies, PD-1 KO TIL maintain robust effector function and phenotypic markers indicative of functional TIL (Ritthipichai ESMO 2020). We describe preclinical activity, clinical-scale manufacturing process development, and characterization of IOV-4001, an autologous PD-1 KO TIL cell product. Methods: hIL-2 NOG mice engrafted with melanoma tumor cells received adoptive transfer of autologous PD-1 KO TIL (developed with TALEN® gene editing technology in collaboration with Cellectis), mock TIL (electroporation without TALEN), mock TIL + anti-PD-1 antibody, or no adoptive transfer (n=14 each). Tumor size was measured 2×/wk for 39 days. A 22-day clinical-scale manufacturing process was established, including pre-rapid expansion protocol (pre-REP), activation, electroporation, resting, and REP, for the generation of PD-1 KO TIL. Final PD-1 KO TIL product was characterized for total viable cells (TVC), purity (% viability), identity (% CD45+CD3+), and function (PD-1 KO efficiency). Results: Day 39 mean ± SEM tumor size (mm2) for mice treated with PD-1 KO TIL (6 ± 2.8) showed superior tumor control relative to mock TIL (26 ± 8.5, P