A Study to Test Whether Spesolimab Helps People With a Skin Disease Called Netherton Syndrome

Inclusion Criteria: Male or female patients, aged 12 years and older (weight minimum is 35kg). Confirmed diagnosis of Netherton syndrome (NS) (causative SPINK5 mutations) at baseline (Visit 2). At least moderate severity of erythema at baseline (visit 2) (Ichthyosis Area Severity Index (IASI) score ≥ 16 and IASI-Erythema (E) score ≥8) and ≥ 3 on Investigator Global Assessment (IGA) score. Signed and dated written informed consent and assent in accordance with International Council on Harmonisation-Good Clinical Practice (ICH-GCP) and local legislation prior to admission in the trial 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. A list of contraception methods meeting these criteria is provided in the clinical trial protocol (CTP) as well as in the patient, parent(s) (or patient's legal guardian) information. Exclusion Criteria: Patients who have used topical corticosteroids (medium to high, US class I-V), topical retinoids, topical calcineurin inhibitors or keratolytics within 1 week prior to randomisation Patients who have used emollient on the area to be biopsied in the previous 24 hours Patients who have used systemic retinoids, other systemic immunosuppressants, systemic corticosteroids or phototherapy within 4 weeks prior to randomisation Patients who have used systemic antibiotics within 2 weeks prior to randomisation Patients who have received live vaccines within 4 weeks prior to randomisation Patients who have received investigational products, biologics or immunoglobulins within 4 weeks or 5 half-lives (whichever is longer) prior to randomisation Severe, progressive, or uncontrolled hepatic disease, defined as >3-fold Upper Limit of Normal (ULN) elevation in Aspartate Aminotransferase (AST) or Alanine Aminotransferase (ALT) or alkaline phosphatase, or >2-fold ULN elevation in total bilirubin Patients who have any prior exposure to BI 655130 or another interleukin 36 receptor (IL-36R) inhibitor biologics Further exclusion criteria apply