Intralesional administration of VAX014 facilitates in situ immunization and potentiates immune checkpoint blockade in immunologically cold tumors.

BACKGROUND: Immunologically cold tumors with an 'immune desert' phenotype lack tumor-infiltrating lymphocytes (TILs) and are typically impervious to systemic immune checkpoint blockade (ICB). Intratumoral treatment of tumors with immunomodulatory agents can promote local tumor inflammation leading to improved T cell responses in injected tumors. Addition of systemic ICB increases response frequency and immune-mediated clearance of injected and distal non-injected lesions, and this promising approach is being widely investigated clinically. In this work, we evaluate and characterize the local and systemic antitumor immunotherapeutic activity of VAX014, a novel non-viral targeted oncolytic agent based on recombinant bacterial minicells, following intratumoral administration and in combination with systemic ICB. METHODS: The immunotherapeutic activity of VAX014 following weekly intratumoral administration was investigated in multiple preclinical tumor models with B16F10 murine melanoma serving as the primary model for evaluation of immune desert tumors. Mice bearing a single intradermal tumor were used to evaluate tumor response and overall survival (OS), assess changes in immune cell populations, and explore global changes to immunotranscriptomes of injected tumors. Mice bearing bilateral intradermal tumors were then used to evaluate non-injected tumors for changes in TIL populations and phenotypes, compare immunotranscriptomes across treatment groups, and assess distal non-injected tumor response in the context of monotherapy or in combination with ICB. RESULTS: VAX014 demonstrated strong immune-mediated tumor clearance of injected tumors coinciding with significantly elevated CD8+ TILs and upregulation of multiple immune pathways essential for antitumor immune responses. Modest activity against distal non-injected immune desert tumors was observed despite elevated levels of systemic antitumor lymphocytes. Combination with systemic CTLA-4 blockade improved survival and elevated TILs but did not improve clearance rates of non-injected tumors. Immunotranscriptomes of non-injected tumors from this treatment combination group exhibited upregulation of multiple immune pathways but also identified upregulation of PD-1. Further addition of systemic PD-1 blockade led to rapid clearance of non-injected tumors, enhanced OS, and provided durable protective immunological memory. CONCLUSIONS: Intratumoral administration of VAX014 stimulates local immune activation and robust systemic antitumor lymphocytic responses. Combination with systemic ICB deepens systemic antitumor responses to mediate clearance of injected and distal non-injected tumors.

VAX014, an Oncolytic Therapy, Reduces Adenomas and Modifies Colon Microenvironment in Mouse Model of CRC.

Colorectal cancer (CRC) remains the third most common form of cancer and, despite its reduced mortality, results in over 50,000 deaths annually, highlighting the need for novel therapeutic approaches. VAX014 is a novel clinical-stage, oncolytic bacterial minicell-based therapy shown to elicit protective antitumor immune responses in cancer, but it has not been fully evaluated in CRC. Here, VAX014 was demonstrated to induce oncolysis in CRC cell lines in vitro and was evaluated in vivo, both as a prophylactic (before spontaneous development of adenomatous polyps) and as a neoadjuvant treatment using the Fabp-CreXApcfl468 preclinical animal model of colon cancer. As a prophylactic, VAX014 significantly reduced the size and number of adenomas without inducing long term changes in the gene expression of inflammatory, T helper 1 antitumor, and immunosuppression markers. In the presence of adenomas, a neoadjuvant VAX014 treatment reduced the number of tumors, induced the gene expression of antitumor TH1 immune markers in adenomas, and promoted the expansion of the probiotic bacterium Akkermansia muciniphila. The neoadjuvant VAX014 treatment was associated with decreased Ki67 proliferation in vivo, suggesting that VAX014 inhibits adenoma development through both oncolytic and immunotherapeutic effects. Combined, these data support the potential of VAX014 treatment in CRC and "at risk" polyp-bearing or early adenocarcinoma populations.