Cryo-immune vaccination (CIV):A nontoxic locoregional multicomponent immunotherapeutic approach that can systemically eradicate disseminated metastatic cancers

A major challenge in developing combination immune checkpoint therapy (ICT) is the inherent toxicity of higher-order combinations likely needed to eradicate metastatic disease. Recently, a new general approach to address this challenge termed cryo-immune vaccination (CIV) is being studied. Briefly, CIV involves cycles of local cryolysis of a solid tumor in a metastatic patient, creating a personalized neoantigen vaccine, followed by infusion of the cryo-lysed tumor with a low-dose multi-API formulation. A recent Phase I clinical study of SYNC-T therapy, the first clinical iteration of CIV to be tested, has demonstrated striking safety and efficacy in the systemic responses it can achieve, including most notably at untreated tumors. As trials proceed, we have modeled CIV in mice using the orthotopic 4T1 model of metastatic breast cancer to help illuminate mechanistic foundations. Briefly, after occult pulmonary metastases have seeded we treat the primary tumor by cryoablation followed by infusion of the thawed cyroablated lesion with a multidrug ICT cocktail or control IgG. The starting cocktails were the proprietary SYNC-T combination therapies under study in the LEGION-100 trial of mCRPC (Syncromune, Inc.), including murine-reactive antibodies against CTLA4, PD-1 or OX40 (agonist), CD40 (agonist), plus CpG oligonucleotide. Our work to date has generated several observations concerning CIV efficacy. First, while a single cycle of therapy is ineffective in WT hosts, it is curative in ~25% of Ido1-/- hosts and in early testing >90% of Ido1-/- Ido2-/- hosts. Second, in drug omission experiments the CD40 antibody was less important, with Lag3 antibody substitution improving relative efficacy. Third, CD8+ T cells harvested from cured subjects were sufficient to confer survival in naive 4T1-bearing recipients. Lastly, mice cured of metastatic 4T1 tumors were not only resistant to re-challenge with 4T1 but also to new challenge by EMT6, a different breast cancer model, or CT-26, a colon cancer model, suggesting robust antigen spreading and the generation of large numbers of metastasis-fighting T cell clones unleashed by CIV therapy (as observed clinically with SYNC-T therapy). T cell clonal analysis is being pursued to explore this striking multi-tumor resistance, which may help explain why CIV is effective at eradicating untreated metastases.