Toroidal-spiral particles as a CAR-T cell delivery device for solid tumor immunotherapy.

Chimeric antigen receptor (CAR) T cell therapy has resulted in positive effects on patients with hematologic malignancy but shows limited efficacy in solid tumor treatments due to insufficient trafficking and tumor infiltration, intensive CAR-T-related toxicities, and antigen escape. In this work, we developed and investigated a biodegradable and biocompatible polymeric toroidal-spiral particle (TSP) as a in vivo cell incubator and delivery device that can be implanted near tumor through a minimally invasive procedure or injected near or into solid tumors by using a biopsy needle. The main matrix structure of the millimeter-sized TSP is made from crosslinking of gelatin methacrylamine (GelMA) and poly (ethylene glycol) diacrylate (PEGDA) with a tunable degradation rate from a few days to months, providing appropriate mechanical properties and sustained release of co-encapsulated drugs and/or stimulation compounds. The toroidal-spiral layer of the particles, presenting an internal void volume for high-capacity cell loading and flexibility of co-encapsulating small and large molecular compounds with individually manipulated release schedules, is filled with collagen and suspended T cells. The TSPs promote cell proliferation, activation, and migration in the tumor micro-environment in a prolonged and sustained manner. In this study, the efficacy of mesothelin (MSLN) CAR-T cells released from the TSPs was tested in preclinical mouse tumor models. Compared to systemic and intratumoral injection, peritumoral delivery of MSLN CAR-T cells using the TSPs resulted in a superior antitumor effect. The TSPs made of FDA approved materials as an in vivo reactor may provide an option for efficiently local delivery of CAR-T cells to solid tumors for higher efficacy and lower toxicity, with a minimally invasive administration procedure.