Neoantigen-specific tumor-infiltrating lymphocytes in gastrointestinal cancers: a phase 2 trial

Adoptive transfer of unselected autologous tumor-infiltrating lymphocytes (TILs) has mediated meaningful clinical responses in patients with metastatic melanoma but not in cancers of gastrointestinal epithelial origin. In an evolving single-arm phase 2 trial design, TILs were derived from and administered to 91 patients with treatment-refractory mismatch repair proficient metastatic gastrointestinal cancers in a schema with lymphodepleting chemotherapy and high-dose interleukin-2 (three cohorts of an ongoing trial). The primary endpoint of this study was the objective response rate as measured using Response Evaluation Criteria in Solid Tumors 1.0; safety was a descriptive secondary endpoint. In the pilot phase, no clinical responses were observed in 18 patients to bulk, unselected TILs; however, when TILs were screened and selected for neoantigen recognition (SEL-TIL), three responses were seen in 39 patients (7.7% (95% confidence interval (CI): 2.7-20.3)). Based on the high levels of programmed cell death protein 1 in the infused TILs, pembrolizumab was added to the regimen (SEL-TIL + P), and eight objective responses were seen in 34 patients (23.5% (95% CI: 12.4-40.0)). All patients experienced transient severe hematologic toxicities from chemotherapy. Seven (10%) patients required critical care support. Exploratory analyses for laboratory and clinical correlates of response were performed for the SEL-TIL and SEL-TIL + P treatment arms. Response was associated with recognition of an increased number of targeted neoantigens and an increased number of administered CD4⁺ neoantigen-reactive TILs. The current strategy (SEL-TIL + P) exceeded the parameters of the trial design for patients with colorectal cancer, and an expansion phase is accruing. These results could potentially provide a cell-based treatment in a population not traditionally expected to respond to immunotherapy. ClinicalTrials.gov identifier: NCT01174121 .