Glatt S, et al. - In patients with rheumatoid arthritis (RA) and inadequate response (IR) to certolizumab pegol, researchers examined the efficacy and safety of dual neutralisation of interleukin (IL)-17A and IL-17F with bimekizumab, a monoclonal IgG1 antibody, in addition to certolizumab pegol (CZP). During this phase 2a, double-blind, proof-of-concept (PoC) study (NCT02430909), they administered open-label CZP 400 mg at Weeks 0, 2 and 4, and 200 mg at Week 6 to patients with moderate-to-severe RA. They randomized patients with IR at Week 8 (Disease Activity Score 28-joint count C-reactive protein (DAS28(CRP))>3.2) 2:1 to CZP (200 mg every 2 weeks (Q2W)) plus bimekizumab (240 mg loading dose then 120 mg Q2W) or CZP plus placebo. Results revealed a rapid decrease in disease activity with 12 weeks of CZP plus bimekizumab confirming the PoC. In patients with RA concomitantly treated with CZP, they identified no unexpected or new safety signals when neutralising IL-17A and IL-17F, but with dual inhibition, a higher rate of treatment-emergent adverse events was noted.