Efficacy and Safety of Imsidolimab for Generalized Pustular Psoriasis

BACKGROUND: Generalized pustular psoriasis (GPP) is a rare, life-threatening disease attributed to aberrant interleukin-36 (IL-36) activity, often due to variants in the IL-36 receptor antagonist gene. Imsidolimab is a novel, humanized, affinity-matured immunoglobulin G4 monoclonal antibody that binds the IL-36 receptor and antagonizes IL-36 signaling. METHODS: Two phase 3 trials were conducted at 26 clinical sites within 11 countries investigating imsidolimab treatment for GPP. GEMINI-1 was a double-blind, placebo-controlled trial that randomly assigned 45 patients (18-80 years of age) with a GPP flare to receive either a single intravenous dose of 300 mg of imsidolimab, 750 mg of imsidolimab, or placebo. The primary endpoint was GPP Physician Global Assessment (GPPPGA) scores of clear (0) or almost clear (1) at week 4 (range: 0 clear to 4 severe; minimally clinically important difference, 1.4). GEMINI-2 was a follow-on relapse prevention trial with a primary objective of evaluating the safety of imsidolimab up to 104 weeks. Patients who improved with treatment in GEMINI-1 were randomly assigned to receive either 200 mg of subcutaneous imsidolimab or placebo monthly, whereas partial responders received open-label 200 mg of subcutaneous imsidolimab monthly. RESULTS: In GEMINI-1, 53% of patients in the groups that received either 300 mg (n=8/15) or 750 mg (n=8/15) of imsidolimab had GPPPGA scores of 0 or 1 at week 4, compared to 13% in the placebo group (n=2/15) (P=0.023 for both the 300 mg vs. placebo comparison and 750 mg vs. placebo comparison). In GEMINI-2, no serious adverse events led to imsidolimab discontinuation. CONCLUSIONS: Compared with placebo, a significantly higher proportion of patients with GPP randomly assigned to receive a single intravenous dose of imsidolimab were clear or almost clear of the disease after 4 weeks based on the GPPPGA. There were no serious adverse events that led to treatment discontinuation with imsidolimab up to 104 weeks of treatment. (Funded by AnaptysBio; ClinicalTrials.gov number, NCT05352893 for GEMINI-1 and NCT05366855 for GEMINI-2.).