A pilot study of lymphodepletion intensity for PBMC-derived, neoantigen-specific CD8+ T cells (Neo-Ts) therapy in patients with advanced solid tumors.

Abstract

2545 Background: Adoptive T cell therapy (ACT) using neoantigen-specific CD8+ T cells (Neo-Ts) derived from patient PBMC was recently developed aiming to target individual patient’s unique tumor mutations and increase treatment efficacy. But the optimal lymphodepletion intensity for Neo-T therapy has yet to be determined. Methods: In this phase I clinical trial (NCT02959905), we generated Neo-Ts from patients with locally advanced or metastatic melanoma or colon cancers that were refractory to standard therapies, and evaluated the effects of lymphodepletion at various dosages (high: 2x500 mg/m2 cyclophosphamide and 2x25 mg/ m2 fludarabine; low: 1x500 mg/m2 cyclophosphamide and 2x25 mg/ m2 fludarabine; and no lymphodepletion) during Neo-T therapy. The primary end point was safety and the secondary end point was objective response rate (ORR). Results: We showed that Neo-T therapy was safe with lymphodepletion at dosages from no lymphodepletion to high intensity. The median PFS was 7.1 months (95% CI:3.7-9.8), and median overall survival (OS) was 16.8 months (95% CI: 11.9-31.7). The ORR was 33.3% (3/9) among all groups. Three patients achieved PR, two of them were in the group without lymphodepletion. One of the PR patients refractory to prior anti-PD-1 therapy also responded to Neo-T therapy. Neoantigen specific TCRs were examined in two responding patients and showed expansion and persistence after treatment. Conclusions: Neo-T therapy with low intensity lymphodepletion or no lymphodepletion could be a safe and promising regimen for advanced solid tumors. Clinical trial information: NCT02959905 .