Alopecia areata (AA) is a chronic relapsing autoimmune disease characterized by nonscarring hair loss affecting children, adolescents, and adults across all ages, races, and genders. AA primarily affects the scalp; however, it also can affect nails, eyelashes, eyebrows, and other hair follicles on the patient's body. The 3 main types of AA are:

• Patchy alopecia (PA), as seen in 90% of clinical diagnoses
• Alopecia totalis (AT), that affects all scalp hair
• Alopecia universalis (AU), involving all scalp, face, and body hair Dermatologist preferences for utility and order of skin-directed therapies to treat AA vary widely, with treatment choices based on various factors such as patients' age, disease duration and severity (Meah et al., 2020).

Ritlecitinib is a bioavailable small molecule that irreversibly binds to Janus kinase-3 (JAK3) and Tyrosine kinase Expressed in the hepatocellular Carcinoma kinase family (TEC). Ritlecitinib 50 mg once daily was approved by the FDA 23 June 2023 and EMA 20 July 2023 for the treatment of severe alopecia areata in adults and adolescents 12 years of age and older. In Japan, ritlecitinib was approved on 26 June 2023 for the treatment of alopecia areata (limited to intractable cases involving widespread hair loss). Additional countries have since approved ritlecitinib. Those approvals are based on the results of the ritlecitinib pivotal phase 2b/3 study (ALLEGRO 2b/3) which examined efficacy and safety of ritlecitinib in AA patients globally.

Despite positive results from the ALLEGRO program, there is still lack of evidence on ritlecitinib patients' characteristics and clinical outcomes in routine clinical practice. The investigators will evaluate patient and disease characteristics, treatment patterns, and clinical and patient-reported outcomes among patients with AA who are receiving ritlecitinib.

The aim of this study is to measure effectiveness of ritlecitinib in a real-world setting. Ritlecitinib will be prescribed to patients according to the approved product label. Treatment will be guided by clinical judgement of the treating physician ie, study investigators, according to standard of care, independently of this study.

Inclusion Criteria:

1. Male and female patients aged >12 years at baseline.
2. Patients with diagnosis of alopecia areata confirmed by a certified dermatologist, who are prescribed ritlecitinib as per the product label independently of the decision to enroll a patient in this study.
3. Evidence of a personally signed and dated informed consent document indicating that the patient (or a legally acceptable representative) has been informed of all pertinent aspects of the study. Following receipt of oral and written information about the trial, the adolescent (depending on local institutional review board/independent ethics committee requirements) must provide assent, and one or both (according to local regulations) parents or guardians of the child must provide signed informed consent before any study-related activity is carried out.
4. Patients, who in the opinion of the investigator, are willing and able to comply with regular clinic visits as per standard practice at the site and agree to complete PRO questionnaires and other patient completed questions.

Exclusion Criteria:

1. Diagnosed with other types of alopecia or other diseases that can cause hair loss (including, but not limited to known androgenetic alopecia, traction and scarring alopecia, telogen effluvium).
2. Diagnosed with other scalp diseases that may impact AA assessment (e.g., scalp psoriasis, dermatitis, etc.) or other active systemic diseases that may cause hair loss (e.g., lupus erythematosus, thyroiditis, systemic sclerosis, lichen planus, etc.). that could interfere with assessment of hair loss/regrowth.
3. Patients previously treated with ritlecitinib or other JAK inhibitors.
4. Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family.

The study population eligible for enrollment includes any adult and adolescent patients aged ≥12 years diagnosed with AA who receive at least one dose of ritlecitinib and satisfy the inclusion and exclusion criteria. The study will be open for enrollment for approximately 12 months after the first patient has been enrolled. Depending on the observed enrollment rate, the enrollment period and number of sites may be reassessed and revised during the study. It will be allowed to enroll patients with previous use of topical JAK inhibitors only if there was at least a 4-week wash-out period prior to Baseline Visit

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.