It was recently shown that targeting extracellular vimentin (eVim) is safe and effective in preclinical models. Here, we report the safety and efficacy in client-owned dogs with spontaneous bladder cancer of CVx1, an iBoost technology-based vaccine targeting eVim in combination with COX-2 inhibition. This was a single-arm prospective phase 1/2 study with CVx1 in 20 client-owned dogs with spontaneous UC which involved four subcutaneous vaccinations with CVx1 at 2-week intervals for induction of antibody titers, followed by maintenance vaccinations at 2-month intervals. Additionally, daily cyclooxygenase (COX)-2 inhibition with meloxicam was given. The response was assessed by antibody titers, physical condition, abdominal ultrasound and thorax X-ray. The primary endpoints were the development of antibody titers, as well as overall survival compared to a historical control group receiving carboplatin and COX-2 inhibition with piroxicam. Kaplan–Meier survival analysis was performed. All dogs developed antibodies against eVim. Titers were adequately maintained for the duration of this study. A median overall survival of 374 days was observed, which was 196 days for the historical control group (p < 0.01). Short-term grade 1–2 toxicity at the injection site and some related systemic symptoms peri-vaccination were observed. No toxicity was observed related to the induced antibody response. A limitation of this study is the single-arm prospective setting. CVx1 plus meloxicam consistently induced efficient antibody titers, was well tolerated and showed prolonged survival. The results obtained merit further development for human clinical care
