This is a long-term extension study of HSK44459-202 in eligible participants who have completed the Week 12 visit of the originating Study HSK44459-202. The total duration of this study will be up to 56 weeks which will include a 52-week treatment period, and a 4-week safety follow-up period after the last study intervention administration. Safety will be assessed by the incidence and severity of adverse events during the study.

Inclusion Criteria:

- Have previously participated in clinical studies on the treatment of Bechet's disease with HSK44459 tablets and completed the specified treatment in accordance with the protocol;

Exclusion Criteria:

1. Active involvement of major organs related to Behçet's disease - pulmonary (eg, pulmonary artery aneurysms), vascular (eg, thrombophlebitis), gastrointestinal (eg, gastrointestinal ulcers), and central nervous system (eg, meningoencephalitis) manifestations, and ocular lesions (eg, uveitis) requiring immunosuppressive treatment.
2. Subjects who experienced treatment-emergent serious adverse events (SAEs) related to the investigational product in previous HSK44459 studies, and in the investigator's judgment, are not suitable for continuing treatment with HSK44459 tablets.
3. Currently has hepatitis B surface antigen (HBsAg) or hepatitis C antibody (anti-HCV) positive, or has other clinically active liver disease, or tests positive for HBsAg or anti-HCV
4. Subjects whom the investigator deems to have any other factors that make them unsuitable for participating in this clinical study.