A Study to Test Whether Spesolimab Helps People With Generalized Pustular Psoriasis (GPP) Who Need Treatment for Repeated Flares

This study is open to adults with a serious skin disease called generalized pustular psoriasis (GPP) who have repeated flares of GPP. The purpose of this study is to find out whether a medicine called spesolimab helps people with repeated flares of GPP. Participants are given a single dose of spesolimab as an infusion into a vein on the first day of an outbreak of GPP. They may be given a second dose 1 week later if doctors think it is helpful. They are also treated for additional GPP flares. During the time of the study, doctors regularly examine participants' skin for signs of GPP to see how well the treatment works and take blood samples. The doctors also regularly check participants' health and take note of any unwanted effects.

Inclusion Criteria: * Patients with a Generalized Pustular Psoriasis Physician Global Assessment (GPPGA) pustulation sub-score of 0 or 1 and a known and documented history of Generalized Pustular Psoriasis (GPP) (per European Rare And Severe Psoriasis Expert Network - ERASPEN - criteria), regardless of Interleukin 36 Receptor Antagonist (IL-36RN) gene mutation status or Patients with a GPP flare and a known and documented history of GPP (per ERASPEN criteria) regardless of IL-36RN gene mutation status. * Patients must have a history of frequent GPP flares in the past * Male or female patients, aged ≥18 years (if local legislation for age of consent differs, then local legislation will be followed) at screening * Signed and dated written informed consent prior to admission to the trial in accordance with International Conference on Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior to start of any screening procedures * Women of childbearing potential (WOCBP) must be ready and able to use highly effective methods of birth control per ICH M3 (R2) that result in a low failure rate of less than 1% per year when used consistently and correctly Exclusion Criteria: * Drug-triggered Acute Generalized Exanthematous Pustulosis (AGEP) * Patients with primary plaque psoriasis vulgaris without presence of pustules or with pustules that are restricted to psoriatic plaques * Patients with primary erythrodermic psoriasis vulgaris * Patients with SAPHO (Synovitis-acne-pustulosis-hyperostosis-osteitis) syndrome * Immediate life-threatening flare of GPP or requiring intensive care treatment, according to the investigator's judgement. Life-threatening complications mainly include, but are not limited to, cardiovascular/cytokine driven shock, pulmonary distress syndrome, or acute renal failure * Severe, progressive, or uncontrolled hepatic disease, defined as \>3-fold upper limit normal (ULN) elevation in Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) or alkaline phosphatase, or \>2-fold ULN elevation in total bilirubin * Presence of acute demyelinating neuropathy * Treatment with any drug considered likely to interfere with the safe conduct of the trial, as assessed by the investigator * Further exclusion criteria apply.