Inspired by a phase 2 trial of topical ruxolitinib, a targeted kinase inhibitor, for chronic cutaneous graft-versus-host disease. This complication of stem cell transplantation occurs when donor immune cells attack the recipient’s tissues, causing skin symptoms such as rashes, lesions and changes in pigmentation. In the trial, patients acted as their own controls: ruxolitinib cream was applied to one side of the body or face, and a placebo to the other. The affected skin area decreased from 14.3% to 6.2% with ruxolitinib, compared with 14.5% to 10.4% with placebo (p=0.0030).