Efficacy and safety evaluation of gilvetmab in dogs with melanoma and mast cell tumor.

BACKGROUND

Immune checkpoint inhibitors (ICIs) have transformed oncology in human medicine, providing clinical benefit in a broad spectrum of cancers. Widely available ICIs for dogs are lacking.

HYPOTHESIS/

OBJECTIVES

Evaluate efficacy and safety of gilvetmab, a caninized anti-PD-1 monoclonal antibody.

ANIMALS: Fifty-one client-owned dogs were evaluated, 25 with stages II-III melanoma and 26 with stages I-III mast cell tumor (MCT). Fifteen dogs with stages III-V lymphoma were also evaluated.

METHODS

Multi-institutional, open-label study. Enrolled dogs were treated with gilvetmab IV at 6 mg/kg q28d or 10 mg/kg q14d; 8 dogs receiving the lower dosage underwent dose escalation with their owners' consent. Safety was evaluated by physical examinations, laboratory testing, and clinical observations made by veterinarians or the dogs' owners. Efficacy was assessed by objective response rate (ORR) and time to progression (TTP) using cRECIST v1.0 and lymphoma response criteria.

RESULTS

For melanoma, the ORR was 20% (95% confidence interval [CI], 7%-41%) and median TTP was 56 days. For MCT, the ORR was 46% (95% CI, 27%-67%) and median TTP was not reached. No objective responses were observed in dogs with lymphoma. Serious adverse events of anaphylaxis, hypotension, or tumor hemorrhage occurred in 3 dogs (3/51, 5.9%). Tumor enlargement before regression, consistent with possible pseudoprogression, was observed in 2 dogs with melanoma.

CONCLUSIONS AND CLINICAL

IMPORTANCE

Gilvetmab has a reasonable expectation of efficacy and an acceptable preliminary safety profile in dogs with MCT stages I-III and melanoma stages II and III.