Inclusion Criteria:
* Participants of any gender, age 18 years or older, at the time of informed consent at Screening
* Participants who are willing and able to adhere to the study visit schedule and comply with protocol requirements.
* Participant self-reports a history of at least 6 months of moderate-to-severe CA (FFA or CCCA). Diagnosis will be made clinically, and severity assessed with according to the FFASI32 ≥30 and/or CHLG ≥3.
* Participant has a negative Tuberculin purified protein derivative (PPD) or QuantiFERON TB-Gold test (QFT) at screening or within the last 12 months.
* A female participant is eligible to participate if she is not pregnant or breastfeeding, and at least one of the following conditions applies: Is not a woman of childbearing potential (WOCBP) OR Is a WOCBP (all female participants, regardless of whether or not they have experienced/reported menarche, are considered WOCBP unless they are permanently sterile or confirmed infertile). A WOCBP who is sexually active must use a contraceptive method that is highly effective, with a failure rate of \<1%, during the intervention period and for at least 28 days after the last dose of study intervention. And if a WOCBP, must have a negative highly sensitive serum pregnancy test at the screening visit and a negative urine pregnancy test at baseline performed before the first dose of study intervention.
* Participant is judged to be in otherwise good overall health following a detailed medical and medication history, physical examination, and laboratory testing.
Exclusion Criteria:
* Participant's cause of hair loss is indeterminable and/or they have concomitant causes of alopecia, such pregnancy-related, drug-induced, telogen effluvium, or advanced androgenetic alopecia.
* Participant has a history of CA for \> 5 years since the disease onset, severe fibrosing disease, or very rapid hair loss at screening.
* Participant has a history of moderate to severe keloids on the scalp, as determined by clinical examination at screening. Deucravacitinib in the Treatment of Cicatricial Alopecias October 23, 2025.
* Other scalp disease that may impact assessment (e.g., scalp psoriasis, dermatitis, etc.).
* Participant is pregnant or breastfeeding.
* Participation in other studies involving investigational drug(s) within 4 weeks or within 5 half-lives (if known), whichever is longer, prior to study entry and/or during study participation (de novo patients only).
* Active systemic diseases that may cause hair loss (e.g., systemic lupus erythematosus, thyroiditis, systemic sclerosis, etc.).
* Any Psychiatric condition in the opinion of the investigator precludes participation in the study.
* Current or recent history of clinically significant severe, progressive, or uncontrolled renal (including but not limited to active renal disease or recent kidney stones), hepatic, hematological, gastrointestinal, metabolic, endocrine (particularly thyroid disease which can be associated with hair loss), pulmonary, cardiovascular, psychiatric, immunologic/rheumatologic or neurologic disease; or have any other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration, or interfere with the interpretation of study results; or in the opinion of the investigator, the participant is inappropriate for entry into this study, or unwilling/unable to comply with STUDY PROCEDURES.
* History of thromboembolic events including DVT and PE or history of inherited coagulopathies.
* Any present malignancies or history of malignancies with the exception of adequately treated or excised non-metastatic basal cell or squamous cell cancer of the skin or cervical carcinoma in situ.
* History of any lymphoproliferative disorder such as Epstein Barr Virus (EBV) related lymphoproliferative disorder, history of lymphoma, history of leukemia, or signs and symptoms suggestive of current lymphatic or lymphoid disease.
* History (single episode) of disseminated herpes zoster or disseminated herpes simplex, or a recurrent (more than one episode of) localized, dermatomal herpes zoster.
* History of systemic infection requiring hospitalization, parenteral antimicrobial therapy, or as otherwise judged clinically significant by the investigator within 6 months prior to Day 0.
* Active acute or chronic infection requiring treatment with oral antibiotics, antivirals, antiparasitics, antiprotozoals, or antifungals within 4 weeks prior to Day 0 or superficial skin infection within 1 week prior to Day 0. Deucravacitinib in the Treatment of Cicatricial Alopecias October 23, 2025.
* Considered in imminent need for surgery or with elective surgery scheduled to occur during the study.
* Active hepatitis B, hepatitis C, human immunodeficiency virus (HIV), or positive HIV serology at the time of screening.
* Participant has any uncertain or clinically significant laboratory abnormalities that may affect interpretation of study data or endpoints, as determined by the PI.
* Have an active history of alcohol or substance abuse within 1 year prior to Day 0.
* Participant has received a live attenuated vaccine ≤ 6 weeks prior to study screening.
* History of adverse systemic or allergic reactions to components of study drug.
* Use of systemic immunosuppressive medications, including, but not limited to, cyclosporine, systemic corticosteroids, mycophenolate mofetil, azathioprine, methotrexate, within 8 weeks prior to baseline visit.
* Use of other non-biologic systemic agent for CA, including, 5α-reductase inhibitors, hydroxychloroquine, or retinoids, within 4 weeks prior to baseline visit.
* Use of an intralesional corticosteroids or oral JAK inhibitor (tofacitinib, ruxolitinib, or any JAK1/TYK2 product) within 4 weeks prior to the baseline visit.
* Any previous use of a TYK2 inhibitor.
* Participant has used topical corticosteroids, and/or tacrolimus, and/or pimecrolimus or cyclosporine within 1 week before the baseline visit.
* Participant has been previously treated with biological drugs in the last 12 weeks for other indications.
* Participants previously tested with a positive or indeterminable PPD or QFT result, including participants that completed standard tuberculosis therapy.
