Efficacy and Safety of Relfovetmab Administered Every Three Months for the Treatment of Pain Associated with Osteoarthritis in Client-Owned Cats.

Relfovetmab, a felinized anti-nerve growth factor monoclonal antibody, was evaluated for the control of osteoarthritis-(OA) related pain in a prospective, randomized, multicenter, placebo-controlled, double-masked, parallel-group field trial in 307 client-owned cats (median age, 11.0 years) with OA. Cats were randomized (1:1) to relfovetmab (0.5-1.25mg/kg; n = 153;) or placebo (saline, n = 154), administered subcutaneously (SC) every three months for three doses. Day 90 treatment success (Client-Specific Outcome Measures total score reduction ≥ 2 vs Day 0), the primary endpoint, was achieved in 73.0% of cats treated with relfovetmab and 46.8% of placebo cats (odds ratio: 3.08; 95% CI: 1.68-5.63; p<0.001). Significant differences (p<0.05) favoring relfovetmab over placebo in treatment success were seen throughout the study (Days 3-270). Significant differences (p<0.05) favoring relfovetmab over placebo were also seen on the owner overall assessment, change in quality of life, temperament and happiness, and veterinary categorical pain assessment throughout the nine months study duration. Immunogenicity was rare (n=3; 1.97%), transient, and did not affect safety. Adverse events occurred at a similar frequency in both treatment groups (relfovetmab, 44.4%; placebo, 39.6%), except for pain on injection which occurred at a numerically higher frequency in the relfovetmab group versus placebo (relfovetmab, 7.2%; placebo, 1.3%). Relfovetmab (0.5-1.25mg/kg) administered to cats by SC injection every three months was safe and effective for the management of pain associated with OA, with a rapid onset of efficacy as early as three days after the first dose.