Objectives Tanezumab, a monoclonal antibody, inhibits nerve growth factor and reduces chronic pain. This randomised, double-blind, controlled multicentre study was conducted to evaluate the efficacy and safety of tanezumab added to oral diclofenac sustained release (DSR) in patients with hip or knee osteoarthritis (OA) pain.

Methods Patients (N=604) with moderate to severe knee or hip OA tolerating stable DSR were randomised and treated with DSR 75 mg twice daily combined with intravenous tanezumab 10, 5 or 2.5 mg or placebo at weeks 0, 8 and 16. Co-primary efficacy endpoints (Western Ontario and McMaster Universities OA Index (WOMAC) Pain and Physical Function subscales and patient's global assessment of OA) were assessed at week 16.

Results All co-primary endpoints were significantly improved for all tanezumab+DSR groups versus placebo+DSR (p≤0.039). The incidence of adverse events of abnormal peripheral sensation was lower than in previous tanezumab trials. No new safety signals emerged. Overall incidence of adverse events was higher with tanezumab+DSR (45.2%–49.7%) than with placebo+DSR (34.9%); serious adverse event rates were similar across treatments (5.3%–7.6%). Osteonecrosis was reported in six of 452 patients with tanezumab+DSR (1.3%), but an external adjudication committee did not confirm osteonecrosis in any patient.

Conclusions Addition of tanezumab to DSR resulted in significant improvements in pain, function and global assessments in patients with OA. Although no new safety signals were observed, the higher incidence of adverse events in the tanezumab+diclofenac group suggests that combination therapy is unfavourable. Further investigations of tanezumab monotherapy for OA pain treatment are required.

Clinical trial registration number NCT00864097