Abstract
Adoptive T cell therapy (ACT) with expanded tumor-infiltrating lymphocytes (TIL) can induce durable responses in cancer patients from multiple histologies, with response rates of up to 50%. Antibodies blocking the engagement of the inhibitory receptor programmed cell death protein 1 (PD-1) have been successful across a variety of cancer diagnoses. We hypothesized that these approaches could be combined by using CRISPR-Cas9 gene editing to knock out PD-1 in TILs from metastatic melanoma and head-and-neck, thyroid, and colorectal cancer. Non-viral, non-plasmid-based PD-1 knockout was carried out immediately prior to the traditional 14-day TIL-based ACT rapid-expansion protocol. A median 87.53% reduction in cell surface PD-1 expression was observed post-expansion and confirmed at the genomic level. No off-target editing was detected, and PD-1 knockout had no effect on final fold expansion. Edited cells exhibited few phenotypic differences and matched control functionality. Pre-clinical-scale results were confirmed at a clinical scale by generating a PD-1-deficient TIL product using the good manufacturing practice facilities, equipment, procedures, and starting material used for standard patient treatment. Our results demonstrate that simple, non-viral, non-plasmid-based CRISPR-Cas9 methods can be feasibly adopted into a TIL-based ACT protocol to produce treatment products deficient in molecules such as PD-1, without any evident negative effects.