Objective: Evaluate the safety of guselkumab (monoclonal antibody targeting interleukin [IL]-23p19) in patients with psoriatic arthritis (PsA) through 1 year (1Y) of the phase III DISCOVER-1 and DISCOVER-2 trials.

Methods: Patients with active PsA (n = 1120; biologic-naïve except 118 patients treated with tumor necrosis factor inhibitors in DISCOVER-1) were randomized to subcutaneous guselkumab 100 mg every 4 weeks (Q4W) or at Week 0, Week 4, then every 8 weeks (Q8W); or placebo. At Week 24, patients in the placebo group switched to guselkumab 100 mg Q4W. Treatment continued through 1Y and 2 years for DISCOVER-1 and DISCOVER-2, respectively. In this pooled analysis, patients with ≥ 1 adverse event (AE) through 1Y were standardized for 100 patient-years [100 PYs] of follow-up.

Results: Through Week 24, adverse events (AEs) were consistent between patients treated with placebo and guselkumab (Q4W + Q8W). AEs were 142.8/100 PYs and 150.6/100 PYs, serious AEs were 7.1/100 PYs and 4.4/100 PYs, and AEs leading to study agent discontinuation were 4.1/100 PYs and 3.8/100 PYs, respectively. Through 1Y in patients treated with guselkumab, no uveitis, active tuberculosis, opportunistic infections, or inflammatory bowel disease were observed, and low rates of malignancy and major adverse cardiovascular (CV) events were observed. Injection-site reactions occurred in 1.7%, and antibodies to guselkumab in 4.5% of patients treated with guselkumab through 1Y; the vast majority of antibodies to guselkumab were nonneutralizing. Serum hepatic transaminase elevations (more common with Q4W than Q8W dosing) and decreased neutrophil counts were generally mild, transient, and did not require treatment discontinuation, with minimal change from Week 24 to 1Y.

Conclusion: Guselkumab 100 mg Q4W and Q8W were well tolerated in patients with PsA, with no new safety concerns through 1Y of the phase III DISCOVER trials. Guselkumab safety through 1Y in patients with PsA is consistent with that established in patients with psoriasis who were treated with guselkumab.