A Study to Test Whether Spesolimab Helps People With a Skin Condition Called Pyoderma Gangrenosum

The purpose of this study is to find out whether a medicine called spesolimab helps people with pyoderma gangrenosum (PG). The main aim is to see whether spesolimab leads to closure of PG ulcers. This study is open to adults with ulcerative PG with at least 1 ulcer that measures between 5 cm\^2 to 80 cm\^2 in size. This study has 2 parts. In Part 1, participants are put into groups randomly, which means by chance. 1 group gets spesolimab and the other group gets placebo. Placebo infusions look like spesolimab infusions, but do not contain any medicine. Every participant has a 2 in 3 chance of getting spesolimab. For the first 8 weeks, participants also take corticosteroid medicine by mouth. In Part 2, participants are put into groups again. Participants without open ulcers have an equal chance of getting spesolimab or placebo. Participants with open skin ulcers will get spesolimab. In both parts, participants receive spesolimab or placebo as an infusion into a vein every 4 weeks. Participants are in the study for about 1.5 years. During this time, they visit the study site 20 times. At study visits, doctors check the participant's skin for signs of PG. The doctors also regularly check participants' health and take note of any unwanted effects. The results of the groups are compared to see whether the treatment works.