The purpose of this study is to learn about the safety and effects of the study medicine ritlecitinib for the possible treatment of nonsegmental vitiligo. Vitiligo causes white patches on your skin when the cells that give your skin color are destroyed. Nonsegmental means that it can affect both sides of the body such as both knees and both hands.
Ritlecitinib has been tested in earlier clinical studies and has a favorable safety profile. At present there are no approved medications taken by mouth to treat nonsegmental vitiligo.
This study is seeking participants who:
* Are 18 years of age or older.
* are confirmed to have nonsegmental vitiligo for at least 3 months.
* Are willing to stop all other treatments that they may be taking for vitiligo.
In this study participants will be chosen by chance, like drawing names out of a hat to receive 1 of 3 treatments:
•Part I where two different amounts of ritlecitinib (50 mg and 100 mg) are taken once daily. It will be compared to placebo. Placebo is a dummy capsule. It doesn't have any medicine used in the study.
Participants receiving placebo who have not responded to treatment after 52 weeks will be given 100 milligrams or 50 milligrams of ritlecitinib for the remaining 52 weeks of the study.
• In Part II, participants will only receive 100 milligrams of ritlecitinib. About 1000 participants will take part in Part I and around 450 in Part II globally. The study will compare the experiences of people receiving ritlecitinib to those of the people who do not. This will help see if ritlecitinib is safe and effective.
People in Part I will be in this study for about 26 months and people in Part II will be in this study for about 14 months. During the study, participants in part I will need to visit the study site at least 17 times. In part II, participants will visit at least 11 times.
Participants will undergo various tests and procedures such as:
* vitiligo rating,
* physical examinations,
* hearing tests,
* blood tests,
* photographs of areas with vitiligo. Participants will be asked to complete questionnaires about their vitiligo.