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

This study is open to people with a skin disease called Netherton syndrome (NS). People can join the study if they are 12 years or older. The purpose of this study is to find out whether a medicine called spesolimab helps people with NS. Participants are divided into a spesolimab and a placebo group. Placebo injections look like spesolimab injections but do not contain any medicine. Every participant has a 2 in 3 chance of being in the spesolimab group. In the beginning, participants get the study medicine as an injection into a vein. Afterwards, they get it as an injection under the skin every month. After 4 months, participants in the placebo group switch to spesolimab treatment. Participants are in the study for up to 3 years. During this time, they visit the study site up to 42 times. The doctors regularly check participants' NS symptoms. The results are compared between the groups to see whether spesolimab works. The doctors also regularly check participants' general health and take note of any unwanted effects.