CTIM-41 - Oncolytic immunotherapy links immunoactivation to subject survival in phase I trial of recurrent glioblastoma

A “first-in-human” phase 1 trial of intralesional injection of CAN-3110, an immunotherapeutic oncolytic based on herpes simplex virus 1 (HSV1), was conducted in 41 subjects with recurrent high-grade glioma (rHGG). The impact of CAN-3110 on the tumor immune microenvironment was assessed using immunohistochemistry, multiplexed immunofluorescence, TCR-beta DNA sequencing, and bulk RNA sequencing of paired pre- and post-treatment samples. These analyses were combined with patient features to identify potential biomarkers of therapy response in rHGG. In IDH wild type recurrent glioblastoma (IDHwt rGBM) patients, post-treatment survival times were positively associated with positive pre-treatment HSV1 serology after controlling for additional covariates such as tumor volume, age, gender, CAN-3110 dose, etc. (HR = 0.16, p < 0.001, n = 32, CoxPH). Positive HSV1 serology was also significantly associated with clearance of CAN-3110 from injected tumors. Interestingly, increased intratumoral CD8 and CD4 T cell numbers following treatment were positively associated with prolonged survival in HSV1 seropositive patients (p = 0.017 and 0.026, respectively), but not when analyses were conducted including HSV1 seronegative patients. Likewise, post-treatment immune expression signatures (such as for antitumor cytokines, T cell traffic, etc.) were more strongly associated with prolonged survival for HSV1 seropositive patients than for seronegative patients, and most assessed immune signatures only became associated with survival after CAN-3110 treatment. Extended survival was also associated with increased TCR-beta diversity following therapy in both the tumor and in PBMCs. Combined with a lack of observed dose-limiting toxicities and a median post-treatment survival of 14.2 months (95% CI: 9.5-15.7) in IDHwt rGBM patients with positive HSV1 serology, these data provide evidence that intralesional CAN-3110 treatment can instigate immune activation in a traditionally immunologically cold tumor and that this immune activation may influence survival time—particularly when patients have had prior exposure to HSV1. (clinicaltrials.gov NCT03152318)