The Efficacy, Tolerability, and Joint Safety of Fasinumab in Osteoarthritis Pain: A Phase IIb/III Double-Blind, Placebo-Controlled, Randomized Clinical Trial

Objective: To prospectively assess the efficacy, general safety, and joint safety of fasinumab, an anti-nerve growth factor monoclonal antibody, in osteoarthritis (OA) hip and/or knee pain.

Methods: Patients with moderate-to-severe OA pain (knee or hip) and history of inadequate response or intolerance to analgesics were randomized to receive fasinumab (at 1 mg, 3 mg, 6 mg, or 9 mg) or placebo every 4 weeks over 16 weeks and were followed up to week 36. Efficacy end points were the change from baseline to week 16 in the pain and physical function subscale scores of the Western Ontario and McMaster Universities OA Index (WOMAC), and patient global assessment (PGA) of OA. Joints were monitored at scheduled assessments (by plain film radiography and magnetic resonance imaging) during treatment and follow-up, and if prompted, at the time of active joint symptoms.

Results: Of the 421 patients randomized, 342 completed the 36-week study. All doses of fasinumab yielded statistically significant and clinically important reductions in pain compared to placebo (least squares mean difference in WOMAC pain subscale scores at week 16 ranging -0.78 to -1.40), without any clear dose dependence. Physical function and PGA scores improved in parallel. Treatment-emergent adverse event rates were 17% with fasinumab and 10% with placebo, and 4% and 1% of patients, respectively, discontinued treatment. Arthropathies (25 in total, 7% of fasinumab-treated patients and 1% of placebo-treated patients) occurred in a dose-dependent manner, with 2 occurring in patients receiving the lowest dose of fasinumab and 10 in patients receiving the highest dose. Most of the arthropathies (16 of 25) were discovered with scheduled radiographs and not based on symptoms. Destructive arthropathy (in 1 of 337 treated patients) occurred in 1 patient who was receiving 6 mg fasimumab.

Conclusion: Fasinumab provided improvements in OA pain and function, even in those benefitting little from previous analgesics. The observed benefit-to-risk relationship favors further clinical development to explore the lowest doses of fasinumab in patients with knee or hip OA.