Imsidolimab

If approved, imsidolimab would be the second IL-36 receptor antibody for GPP after Spevigo, which was approved in September 2022 for flares and in March 2024 for flare prevention. The 2 have not been compared head to head. The GEMINI data cover both roles, a single dose for an active flare and monthly dosing to prevent the next one, so the practical questions for patients and dermatologists will be the maintenance route, dosing interval and cost once the label is known.

Generalized pustular psoriasis is driven by an overactive inflammation signal in the skin called the interleukin-36 pathway. Normally a protein called IL-36Ra keeps that pathway in check; in many people with GPP it is weak or missing, often because of a change in the IL36RN gene, and the pathway floods the skin with white blood cells that form pustules. Imsidolimab is an antibody that sits on the IL-36 receptor so the signal cannot be delivered, acting as a substitute for the missing brake. It is the same strategy used by Spevigo (spesolimab), the first drug approved for GPP, and Vanda reports that it produced a low rate of antibodies against the drug itself in the trials.

Vanda describes the safety profile in GEMINI-1 and GEMINI-2 as favorable with a low incidence of anti-drug antibodies, and the full results were published in NEJM Evidence in April 2026. The company's announcements do not list individual adverse event rates, and there is no US label yet. For context, Spevigo, which blocks the same receptor, carries warnings about serious infections, tuberculosis screening, allergic and infusion reactions, and avoiding live vaccines; similar precautions would be expected if imsidolimab is approved.

GEMINI-1 and GEMINI-2 were the pivotal efficacy studies, run in the United States, France, Spain, Poland, Turkey, Malaysia, Thailand, Georgia, Tunisia, Taiwan and Morocco. A single intravenous dose of imsidolimab led to rapid clearance, with 53% of patients reaching clear or almost clear skin on the GPP Physician Global Assessment (GPPPGA 0/1) at week 4 compared with 13% on placebo. Efficacy was maintained through an approximately 2-year maintenance period with monthly doses, and no flares occurred in the active treatment arm. Vanda has not published the number of patients enrolled in its announcements; the full data were published as Smieszek et al. in NEJM Evidence in 2026.

Imsidolimab was developed by AnaptysBio, which licensed exclusive global rights to Vanda Pharmaceuticals. Vanda submitted the biologics license application and announced on February 25, 2026 that the FDA had accepted it with a target action date of December 12, 2026. Vanda's August 5, 2026 quarterly report refers to the product by the proposed brand name Quimilza. Japan's health ministry granted orphan designation in May 2026, and in July 2026 the European Medicines Agency's orphan drug committee adopted a positive opinion recommending orphan designation.