Amy S. Paller reports serving as an investigator, consultant and/or data and safety monitoring board member for AbbVie, Abeona Therapeutics, Amryt Pharma, Azitra, BioCryst, BMS, Boehringer Ingelheim, Castle Creek Biosciences, Catawba Research, Dermavant, Eli Lilly, Galderma, InMed Pharmaceuticals, Incyte, Janssen, Krystal Biotech, LEO Pharma, Novartis, Regeneron Pharmaceuticals Inc., Sanofi, Seanergy, TWi Biotechnology and UCB. Andreas Pinter reports working for AbbVie, Almirall Hermal, Amgen, Biogen Idec, BioNTech, Boehringer Ingelheim, Celgene, Celltrion, Eli Lilly, Galderma, GSK, Hexal, Janssen, Klinge Pharma, LEO Pharma, MC2 Pharma, Medac, Merck-Serono, Mitsubishi Tanabe Pharma, MSD, Novartis, Pascoe, Pfizer, Tigercat Pharma, Regeneron Pharmaceuticals Inc., Roche, Sandoz, Sanofi, Schering-Plough and UCB Pharma. Lara Wine Lee reports acting as an advisory board member consultant, investigator and/or speaker for AbbVie, Amgen, Amryt Pharma, Arcutis Biotherapeutics, Avita, Castle Creek Biosciences, Celgene, Eli Lilly, Galderma, Incyte, Janssen, Kimberly Clark, Kiniksa Pharmaceuticals, Krystal Biotech, Mayne Pharma, MoonLake Immunotherapeutics, Novartis, Pfizer, Regeneron Pharmaceuticals Inc., Sanofi, Target Pharma, Timber Pharmaceuticals, Trevi Therapeutics and UCB. Roland Aschoff reports working for AbbVie, Almirall Hermal, Biofrontera, Boehringer Ingelheim, BMS, BSN medical, Galderma, Janssen-Cilag, LEO Pharma, Lilly, Novartis, Pfizer, Sanofi and UCB. Jacek Zdybski reports serving as an investigator for Almirall, Amgen, BMS, Galderma, Incyte, Innovaderm, Pfizer, Regeneron Pharmaceuticals Inc. and Syneos Health. Christina Schnopp reports serving as lecturer and/or consultant for AbbVie, Amgen, Beiersdorf, Benevi, Celgene, Fortbildungskolleg GmbH, GSK, Galderma, HiPP Organic, InfectoPharm, La Roche-Posay, LEO Pharma, Leti Pharma, Lilly, MSD, Nestlé, Novartis, Nutricia, Pierre Fabre, Sanofi and Unna-Akademie. Amy Praestgaard, Randy Prescilla, and Mike Bastian are employees of and may hold stock and/or stock options in Sanofi. Ashish Bansal and Brad Shumel are employees and shareholders of Regeneron Pharmaceuticals Inc.

The study (trial registration number NCT03346434) was conducted in accordance with the Declaration of Helsinki, the International Conference on Harmonisation Good Clinical Practice guideline and applicable regulatory requirements. An independent data and safety monitoring committee conducted blinded monitoring of patient safety data. The local institutional review board or ethics committee at each study centre oversaw trial conduct and documentation. The study was approved by the Copernicus Group ethics committee. All patients, or their parents/guardians, provided written informed consent before participating in the trial. Pediatric patients provided assent according to the ethics committee (institutional review board/independent ethics committee)-approved standard practice for pediatric patients at each participating centre.