Izokibep Sustains PsA Efficacy at 52 Weeks, With Philip Mease, MD

Izokibep 160 mg, a novel small-protein IL-17A inhibitor, demonstrated durable efficacy across joint, skin, and functional outcomes through 52 weeks in patients with active psoriatic arthritis (PsA), according to results from a randomized, double-blind, placebo-controlled phase 2b/3 study presented at the European Alliance of Associations for Rheumatology (EULAR), held June 3-6 in London, United Kingdom.

Philip Mease, MD, Director of Rheumatology Research at Providence Swedish Medical Center and Clinical Professor of Medicine at the University of Washington School of Medicine, Seattle, presented the data and sat down with RheumatologyLive to discuss its importance. The trial (NCT05623345) enrolled 343 adults with active PsA (duration ≥6 months, ≥3 tender/swollen joints) who had an inadequate response, intolerance, or contraindication to an NSAID, csDMARD, and/or TNF inhibitor. Patients were randomized 1:1:1 to izokibep 160 mg every 2 weeks (Q2W; n = 113), izokibep 160 mg every week (QW; n = 112), or placebo QW (n = 118), with placebo patients crossing over to izokibep 160 mg QW at week 16.

Baseline characteristics were broadly similar across groups. Mean (SD) age was 49.5 (13.3), 51.8 (12.2), and 52.6 (11.7) years; BMI was 30.5 (6.6), 29.1 (5.9), and 29.7 (6.0) kg/m²; and time since diagnosis was 6.2 (6.8), 6.9 (8.0), and 7.1 (6.9) years for Q2W, QW, and placebo→QW groups, respectively.

Both izokibep arms showed continued improvement beyond week 16, and patients crossing over from placebo demonstrated rapid improvement following the switch. By week 52, approximately half of patients in each group achieved ACR50 (Q2W, 50%; QW, 57%; placebo→QW, 51%). ACR70 response rates were 36%, 42%, and 42%, respectively. Among patients with baseline psoriasis body surface area ≥3%, PASI90 was achieved by 63%, 69%, and 65%, and PASI100 by 55%, 64%, and 58%. Minimal disease activity (MDA) was reached by 47%, 52%, and 47%.

Improvements in physical function and patient-reported burden were also sustained. HAQ-DI least squares mean change from baseline was −0.41, −0.43, and −0.37 for Q2W, QW, and placebo→QW groups, respectively, at week 52. PsAID-9 scores improved comparably, with mean changes of −0.41 (Q2W), not separately reported at week 52 in this abstract (week 16: −0.30 Q2W, −0.31 QW), and −0.37 (placebo→QW). More than half of patients with baseline enthesitis (Leeds Enthesitis Index >0) achieved resolution (LEI = 0) by week 52 (Q2W, 57%; QW, 50%; placebo→QW, 59%).

Treatment-emergent adverse events (TEAEs) occurred in 81%, 88%, and 82% of patients in the Q2W, QW, and placebo→QW groups, respectively. The most common TEAEs were injection-site erythema, injection-site pruritus, and nasopharyngitis. The majority were mild to moderate in severity; serious TEAEs were reported at low rates (7%, 4%, and 4%). Rates of ulcerative colitis (0%, 1%, 0%) and oral candidiasis (1%, 1%, 0%) were low across groups. There were no deaths or reports of suicidal ideation.

"The IL-17 class of medicines is a good part [of the treatment armamentarium] because of the relative safety of the medication.. we don't see a high infection signal, we don't see a malignancy signal, we don't see a cardiovascular or thrombosis signal," Mease said.

Mease’s disclosures include AbbVie, Amgen, Eli Lilly, Johnson & Johnson, and UCB Pharma.

References

1. Mease PJ, Behrens F, Kivitz A, et al. Efficacy and safety of izokibep, a novel IL-17A inhibitor, in patients with active psoriatic arthritis: week 52 results from a randomised, double-blind, placebo-controlled, multicentre, phase 2b/3 study [abstract OP073]. Ann Rheum Dis. 2026. doi:10.1136/annrheumdis-2026-eular.B.1289
2. Positive 52-week Phase 2b/3 Data of Izokibep in Psoriatic Arthritis to be Presented at EULAR 2026. Affibody. News release. May 21, 2026. https://www.affibody.se/press/positive-52-week-phase-2b-3-data-of-izokibep-in-psoriatic-arthritis-to-be-presented-at-eular-2026/