Multiple Injections of Electroporated Autologous T Cells Expressing a Chimeric Antigen Receptor Mediate Regression of Human Disseminated Tumor

TLDR

Gene transfer can redirect T‑cell antigen specificity to generate tumor‑reactive lymphocytes, but viral vector safety limits clinical use, whereas RNA electroporation offers a non‑integrating alternative. The study aims to develop a safe, RNA‑based platform for adoptive T‑cell therapy by optimizing transcription vectors and demonstrating that repeated injections of RNA‑engineered T cells can serve as a flexible, non‑viral alternative for cancer treatment. The authors optimized the RNA in vitro transcription vector backbone to achieve high‑level transgene expression in electroporated T cells. RNA‑CAR‑electroporated T cells expressed functional CAR for up to a week and, upon multiple injections, induced regression of large vascularized mesothelioma tumors in immunodeficient mice and dramatic reduction of long‑standing intraperitoneal human tumors, demonstrating that autologous patient T cells can be engineered to treat disseminated cancer in a robust preclinical model and potentially increase therapeutic index without viral vector safety concerns.

Abstract

Redirecting T lymphocyte antigen specificity by gene transfer can provide large numbers of tumor-reactive T lymphocytes for adoptive immunotherapy. However, safety concerns associated with viral vector production have limited clinical application of T cells expressing chimeric antigen receptors (CAR). T lymphocytes can be gene modified by RNA electroporation without integration-associated safety concerns. To establish a safe platform for adoptive immunotherapy, we first optimized the vector backbone for RNA in vitro transcription to achieve high-level transgene expression. CAR expression and function of RNA-electroporated T cells could be detected up to a week after electroporation. Multiple injections of RNA CAR-electroporated T cells mediated regression of large vascularized flank mesothelioma tumors in NOD/scid/γc(-/-) mice. Dramatic tumor reduction also occurred when the preexisting intraperitoneal human-derived tumors, which had been growing in vivo for >50 days, were treated by multiple injections of autologous human T cells electroporated with anti-mesothelin CAR mRNA. This is the first report using matched patient tumor and lymphocytes showing that autologous T cells from cancer patients can be engineered to provide an effective therapy for a disseminated tumor in a robust preclinical model. Multiple injections of RNA-engineered T cells are a novel approach for adoptive cell transfer, providing flexible platform for the treatment of cancer that may complement the use of retroviral and lentiviral engineered T cells. This approach may increase the therapeutic index of T cells engineered to express powerful activation domains without the associated safety concerns of integrating viral vectors.