The use of oncolytic adenovirus (Ads) to treat intracranial tumors has shown promising results. The prognosis of canine glioma is poor with survival time of 60 days with palliative treatment. The biological features and genetic similarity to humans makes canine gliomas a valuable preclinical model. We propose to determine the safety and the efficacy of a canine Ad (ICOCAV15) for high-grade gliomas.

Twelve dogs with spontaneous rostro-tentorial high-grade gliomas were enrolled in the study. They were intratumorally inoculated with 10⁵-10⁷v.p. of ICOCAV15 by craniectomy (n=8), or submitted to a surgical excision (control group, n=4). The safety was analyzed during follow-up (up to 1044 days after-treatment) by blood test. Tumor samples (pre-treatment and post-mortem) were obtained to detect CD3, IBA1 and Calprotectin by immunohistochemistry. Follow-up by MRI was performed, and response determined by RAVNO criteria. This study was approved by the COLVEMA ethics and research committee. 

The ICOCAV15-treated group showed 62.5% of clinical responses (25% of complete remission and 37.5% of stabilization disease) after two months without side effects. Median survival time was 176 days in ICOCAV15-treated patients (versus 62.5 days in control group). The one-year survival rate for the treated group was 25% and the two-year survival was 12.5%. An increase of CD3, IBA1 and Calprotectin was observed in ICOCAV15-treated tumors. 

Treatment with ICOCAV15 does not have any side effects, produces a good clinical response with an increase in immune infiltration. In sum, ICOCAV15 need to be more investigated and could be proposed as a new tool in veterinary neuro-oncology.