1:Universidad Alfonso X El Sabio; 2:Hospital Clínico Veterinario - UAX; 3:Instituto de Salud Carlos III

The use of oncolytic viruses is an innovative approach that produces the lysis of tumor cells and induces antitumor immune responses. The intratumoral therapy with oncolytic virus received the approval from the FDA and EMA with Imlygic for human melanoma patients. Our goal is to determine safety and efficacy of the oncolytic canine adenovirus (Ad) ICOCAV15 in canine patients.

Eight dogs diagnosed with carcinoma and adenocarcinoma were intratumorally treated with ICOCAV15. To evaluate the safety of the treatment, blood count, biochemistry and coagulation test were determined during follow-up. RECIST criteria were used. Neutralizing antibodies against virus were assessed. Immune infiltration, vascularization and viral presence in the tumor were determined by CD3, CD4, CD20, CD31 and Ad using immunohistochemistry. The compassionate use of ICOCAV15 was approved by the Ethics Evaluation Committee of the Official College of Veterinarians of Madrid (COLVEMA).

All dogs maintained good quality of life during follow-up, and some of them increased the median survival time (MST) compared to dogs treated with chemotherapy. No side effects were detected. Two patients showed partial response (PR), and the rest showed stable disease (SD) at different times during the study. ICOCAV15 was detected during follow-up inside the tumor, and antiviral antibodies were detected in all patients. Tumor immune infiltration increased after viral administration.

Therefore, we suggest that ICOCAV15 intratumorally administrated, should be proposed as a new tool to the treatment of carcinoma because of its safety, it is well tolerated by dogs and shows promising results.