This study tests D-2570, an investigational drug, in people with non-segmental vitiligo to check its safety and effect on skin discoloration.

Eligible participants will take D-2570, or a placebo, once daily for 24 weeks in a double-blind setting. Most will then continue into a 24-week extension phase, where those on 27 mg or placebo will switch to one of the lower doses.

All participants will have a 4-week safety follow-up after treatment ends, with regular check-ups and blood tests throughout the study.

This is a Phase 2, multicenter, randomized, double-blind, placebo-controlled, parallel-group study designed to evaluate the safety and efficacy of D-2570 in subjects with non-segmental vitiligo. The study consists of three periods: a screening period (up to 4 weeks), a 24-week double-blind treatment period, and a 24-week extension treatment period, followed by a 4-week safety follow-up period.

During the screening period, written informed consent will be obtained from each subject, and eligibility will be assessed based on predefined inclusion and exclusion criteria. Subjects who meet all eligibility criteria will be stratified according to baseline vitiligo severity (T-VASI <15 or ≥15) and disease activity (active or stable), then randomized in a 1:1:1:1 ratio to one of four treatment groups: D-2570 9 mg QD (Group A), D-2570 18 mg QD (Group B), D-2570 27 mg QD (Group C), or placebo.

During the 24-week double-blind treatment period, subjects will receive once-daily oral study medication. Subjects in Groups A and B will continue the same dose in the subsequent 24-week extension period. Subjects in Group C and the placebo group will be re-randomized in a 1:1 ratio to either D-2570 9 mg QD or 18 mg QD for the extension period, maintaining the blind.

All subjects will attend study visits at protocol-specified time points, including assessments of efficacy (including T-VASI), safety (including adverse events, clinical laboratory tests, vital signs, and physical examinations), and pharmacokinetic evaluations via blood sampling. The study will conclude with an end-of-study (EOS) visit at Week 52, 4 weeks after the last dose of study medication, to collect final safety data. All subjects, investigators, and study site personnel will remain blinded to treatment assignments throughout the study.

Inclusion Criteria:

• Voluntarily signs informed consent and complies with study procedures.
• Age 18-65 years, male or female.
• Clinical diagnosis of non-segmental vitiligo at screening.
• F-VASI ≥0.25 and T-VASI ≥5 at screening and baseline, with either active or stable vitiligo.
• Women of childbearing potential have negative pregnancy tests at screening and baseline. All eligible subjects agree to effective contraception from consent through 30 days after last study drug dose.

Exclusion Criteria:

• - Segmental, mixed vitiligo or other concurrent pigmentary/active skin disorders interfering with study assessment.
• Over 33% facial or total vitiligo lesions with leukotrichia.
• Pregnant or breastfeeding females.
• Active, latent or inadequately treated tuberculosis infection.
• Positive HIV, active HBV/HCV infection, or untreated syphilis.
• Current or history of severe herpes infection.
• Severe systemic infection requiring recent inpatient, intravenous or oral anti-infective treatment.
• Congenital or acquired immune deficiency, opportunistic infection history, or conditions requiring systemic immunosuppression during the study.
• Uncontrolled thyroid disease, severe cardiovascular/cerebrovascular disease or other unstable severe systemic disorders.
• Severe psychiatric disease, suicidal ideation, or alcohol/drug abuse within 6 months.
• Malignancy history within 5 years (excluding cured non-melanoma skin cancer and cervical intraepithelial neoplasia).
• Gastrointestinal disease affecting drug absorption or major surgery within 8 weeks prior to dosing.
• Clinically significant abnormal lab results: elevated liver/renal indices, decreased hemoglobin, WBC, platelet, lymphocyte or neutrophil counts.
• History of severe drug hypersensitivity or drug-related toxicity.
• Any condition that may impair protocol compliance or study participation per investigator judgment.

All participants, care providers, investigators, and outcomes assessors are blinded to treatment assignment throughout the study