Percutaneous Intratumoral Immunoadjuvant Gel Increases The Abscopal Effect of Cryoablation for Checkpoint Inhibitor Resistant Cancer.

Percutaneous cryoablation is a common clinical therapy for metastatic and primary cancer. There are rare clinical reports of cryoablation inducing regression of distant metastases, known as the "abscopal" effect. Intratumoral immunoadjuvants may be able to augment the abscopal rate of cryoablation, but existing intratumoral therapies suffer from the need for frequent injections and inability to confirm target delivery, leading to poor clinical trial outcomes. To address these shortcomings, we have developed an injectable thermoresponsive gel-based controlled release formulation for the FDA-approved TLR7 agonist imiquimod ("Imigel") that forms a tumor-resident depot upon injection and contains a contrast agent for visualization under CT. The PLGA-PEG-PLGA-based amphiphilic copolymer gel's underlying micellar nature enables high drug concentration and a logarithmic release profile that is additive with the neo-antigen release from cryoablation, requiring only a single injection. Rheological testing demonstrated the thermoresponsive increase in viscosity at body temperature and radio-opacity via microCT. We demonstrated its ability to significantly augment the abscopal rate of cryoablation in otherwise immunotherapy resistant metastatic tumors in two aggressive colorectal and breast cancer dual tumor models with an all or nothing response, responders generally demonstrating complete regression of bilateral tumors in 90-day survival studies. This article is protected by copyright. All rights reserved.