Background: CAVATAK, an oncolytic immunotherapy, is a bio-selected oncolytic strain of Coxsackievirus A21 (CVA21). Following intratumoral (IT) injection, CVA21 preferentially infects ICAM-1 expressing tumor cells, resulting in viral replication, cell lysis, and a systemic anti-tumor immune response. The Phase II CALM study investigated the efficacy and safety of IT CVA21 in pts with advanced melanoma with durable responses being observed in both injected and non-injected melanoma metastases, suggesting the generation of significant host anti-tumor responses. Pre-clinical studies in an immune-competent mouse model of melanoma revealed that combinations of intratumoral CAVATAK and anti-PD-1 or anti-CTLA-4 mAbs mediated significantly greater antitumor activity and compared to use of either agent alone. Here we report on an extension study aimed at understanding the impact of CVA21 on immune cell infiltrates and immune checkpoint molecules within treated lesions of advanced melanoma patients.

Methods: In the CALM extension study a cohort of 13 advanced melanoma patients received up to 3 × 108 TCID50 CVA21 IT on study days 1,3,5 and 8 and then every three weeks for a further 6 injections. Sequential tumor biopsies of injected lesions (study days 1 and 8) were monitored for evidence of viral-induced changes immune cell infiltrates (Multi-spectral imaging) and immune checkpoint molecules (NanoString® PanCancer Immune profiling panel). Serial serum samples were monitored for viral loads, anti-CVA21 neutralizing antibody (nAb) and levels of immune-inflammatory cytokines.

Results: Intratumoral CVA21 administration in a number of cases induced significant increases in immune cell infiltrates within the tumor microenvironment, in particular CD8+ cells (p = 0.044) and increased expression of PD-L1+ cells (p = 0.041) as assessed by multi-spectral imaging. Analysis of a number of pre- and post-treatment biopsy samples by NanoString® digital RNA counting identified notable increases in the levels of immune checkpoint molecules including PD-1, PD-L1, CTLA-4, TIM-3 and LAG-3 and sizable up-regulation of a number of immune modulation elements, including Th1-gene shifts, with increases in interferon-induced genes. Of particular interest was the reconstitution of immune cell infiltrates in a number of CVA21 treated lesions from patients failing previous immune-checkpoint blockade or other immunotherapies.

Conclusions: Intratumoral administration of CVA21 can notably influence the dynamics of the tumor micro-environment as evidenced by increases in both immune cell infiltrates and levels of immune-checkpoint genes. Such CVA21 induced immune-changes appear to be beneficial in combination immunotherapy, with preliminary overall response rates in a Phase 1b study CVA21 and anti-CTLA-4 blockade (ipilimumab) in advanced melanoma patients being higher than published response rates for either agent used alone. The use of CVA21 to reconstitute immune cell infiltrates in lesions resistant to immune-checkpoint blockade prior to re-commencing such treatment is an exciting novel therapeutic option.

Citation Format: Robert Andtbacka, Brendan Curti, Sigrun Hallmeyer, Zipei Peng, Christopher Paustian, Carlo Bifulco, Bernard Fox, Mark Grose, Darren R. Shafren. Intratumoral coxsackievirus A21 increases immune-cell infiltrates and upregulates immune-checkpoint molecules in the tumor microenvironment of advanced melanoma patients: phase II CALM extension study. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT053.