This study focuses on PIK3CA-Related Overgrowth Spectrum (PROS), a condition that causes abnormal tissue growth in various parts of the body. The research examines the effectiveness and safety of a medication called alpelisib (also known as BYL719) in both children and adults with this condition. The medication comes in the form of film-coated tablets and granules that are taken by mouth.
The purpose of this study is to determine if alpelisib can help reduce the size of tissue overgrowth in people with PROS. During the study, participants will receive either alpelisib or placebo. The medication will be given daily for 16 weeks, with the possibility of continued treatment. The study will measure changes in the size of affected tissue areas using Magnetic Resonance Imaging (MRI) scans.
The treatment will be evaluated based on whether it can reduce the size of abnormal tissue growths by at least 20%. Participants will be monitored throughout the study to check how well the medication works and to watch for any side effects. The study includes both adults aged 18 and older, and children between 6 and 17 years old.



France
Germany
Italy
Norway
Spain
The Netherlands