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

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.