Alopecia Areata Study

The purpose of the study is to learn about the safety and effects of the study medicine (called ritlecitinib) for the treatment of alopecia areata. Alopecia areata is a disease that causes hair loss on the scalp, face, and areas of the body. Ritlecitinib is approved in many countries at a dose of 50 mg (milligram) taken by mouth once a day for the treatment of patients 12 years and older with severe alopecia areata. This study will look at both the 50 mg dose and a 100 mg dose.