The novel small-protein IL-17 inhibitor izokibep demonstrates durable efficacy and a favourable safety profile over 52 weeks in patients with active psoriatic arthritis (PsA), with sustained improvements in joint, skin, and quality-of-life outcomes in a phase IIB/III study.
At week 16, izokibep met the primary endpoint of ACR50*, as well as several secondary endpoints, including PASI90**, minimal disease activity (MDA), and quality-of-life measures. Week 52 results, reported at EULAR 2026, showed sustained improvement over time in patients randomly assigned to izokibep 160 mg every 2 weeks (Q2W) or every week (QW). Importantly, patients who crossed over from placebo to izokibep showed rapid improvement.
Izokibep was well-tolerated, with a favourable safety profile consistent with previous studies.
“These results underscore izokibep’s potential to offer patients meaningful long-term disease control,” said study investigator Dr Philip Mease, director of Rheumatology Research at Providence Swedish Medical Centre and Clinical Professor of Medicine at the University of Washington School of Medicine, Seattle, Washington, US.
Patients had partial response or were intolerant to previous Tx
Patients (n=343) with active adult-onset PsA (duration ≥6 months, ≥3 tender/swollen joints) who had an inadequate response to, or were intolerant of, prior therapies were randomly assigned to receive subcutaneous izokibep 160 mg Q2W (n=113), izokibep 160 mg QW (n=112), or placebo QW (n=118) for 16 weeks. After week 16, patients initially assigned to izokibep continued treatment, while those on placebo crossed over to izokibep 160 mg weekly. [EULAR 2026, abstract OP073]
Across groups, the mean age ranged from 49.5 to 52.6 years, the mean BMI from 29 to 31 kg/m², and the average disease duration from 6 to 7 years. Baseline disease characteristics were generally balanced across groups.
Outcomes through week 52 included measures of musculoskeletal and skin disease activity, quality of life, enthesitis resolution, and treatment-emergent adverse events (AEs).
Robust results persist over time
Patients who received izokibep maintained progressive clinical improvement beyond week 16, whereas those who crossed over from placebo to izokibep experienced rapid gains. By week 52, ACR50 responses were observed in 50 percent of patients receiving izokibep Q2W, 57 percent of those receiving izokibep QW, and 51 percent of those who switched from placebo. High-level clinical responses were also common, with ACR70 rates of 36 percent, 42 percent, and 42 percent, respectively.
Skin outcomes were similarly robust, with PASI90 reported in 63 percent, 69 percent, and 65 percent of patients. Complete skin clearance (PASI100) was achieved in 55 percent, 64 percent, and 58 percent, respectively. Approximately half of patients across the treatment groups reached minimal disease activity.
Improvements in enthesitis, physical function, and patient-reported disease burden continued to increase through week 52, with more than half of patients with baseline enthesitis achieving resolution.
Safety findings remained favourable over 52 weeks. Treatment-emergent adverse events (AEs) occurred in 81 percent of patients receiving izokibep Q2W, 88 percent of those on weekly dosing, and 82 percent of those who crossed over from placebo.
The most frequently reported AEs were injection-site erythema, injection-site pruritus, and nasopharyngitis. Most AEs were mild to moderate in severity, while serious AEs were infrequent, affecting 7 percent of patients in the Q2W group and 4 percent in each of the weekly dosing groups. Rates of ulcerative colitis and oral candidiasis were low, with no deaths or reports of suicidal ideation.
“The IL-17 class of medicines has a good safety profile. We don’t see a high signal for infection or malignancy. There was no CV or thrombosis signal either,” Mease reported.