Behçet's syndrome (BS) is a systemic autoimmune vasculitis that can affect multiple organs, including the skin, eyes, and vascular system. Refractory BS poses significant treatment challenges, necessitating novel therapeutic approaches. Upadacitinib, a selective JAK1 inhibitor within the JAK-STAT pathway, has shown promise in modulating immune responses. This study aims to evaluate the efficacy and safety of upadacitinib in patients with refractory BS.

This multicenter, single-arm study investigates the efficacy and safety of upadacitinib (15 mg once daily) in refractory Behçet's syndrome (BS) patients. Adult patients had active BS with inadequate response to glucocorticoids and at least two conventional immunosuppressants or biologics over six months. Prior biologics were discontinued, and upadacitinib was added to ongoing glucocorticoids and immunosuppressants for 48 weeks. Clinical symptoms (oral/genital ulcers, skin lesions, uveitis), inflammatory markers (CRP, ESR), and medication usage were monitored. Adverse events were recorded to assess safety.

Inclusion Criteria:

• • Male or female aged 18-70 years at time of screening.

  • Diagnosis of Behcet's syndrome (according to the International Criteria for Behçet's Disease) for ≥3 months before screening.
  • Active Behcet's syndrome at time of screening (BDCAF≥2).
  • Resistant to glucocorticoids, at least two traditional immunosuppressants (one of which must have been cyclophosphamide or mycophenolate mofetil) or biological agents (one of which must have been a TNF-α inhibitor or a JAK inhibitor) for at least 6 months.
  • Given their written informed consent to participate in the trial and expected to be able to adhere to the study visit schedule and other protocol requirements.

Exclusion Criteria:

• High-dose glucocorticoid (>1mg/kg/d) usage within 1 month.
• Severe comorbidities: including heart failure (≥ grade III NYHA), renal insufficiency (creatinine clearance ≤30 ml/min), hepatic insufficiency (serum ALT or AST >3 times the ULN, or total bilirubin >ULN for the central laboratory conducting the test). Other severe, progressive or uncontrolled hematologic, gastrointestinal, endocrine, pulmonary, cardiac, neurologic, or cerebral disease (including demyelinating diseases such as multiple sclerosis).
• Known allergies, hypersensitivity, or intolerance to Baricitinib or its excipients.
• Had a severe infection (including, but not limited to hepatitis, pneumonia, sepsis, or pyelonephritis); had been hospitalized for an infection; or had been treated with IV antibiotics for an infection, within 2 months prior to the first administration of study agent.
• Chest radiograph within 3 months prior to the first administration of study agent that showed an abnormality suggestive of a malignancy or current active infection, including tuberculosis.
• Infected with HIV (positive serology for HIV antibody) or hepatitis C (positive serology for Hep C antibody). If seropositive, consultation with a physician with expertise in the treatment of HIV or hepatitis C virus infection was recommended.
• Infected with hepatitis B virus. For patients who were not eligible for this study due to hepatitis B virus test results, consultation with a physician with expertise in the treatment of hepatitis B virus infection was recommended.
• Had any known malignancy or has a history of malignancy within the previous 5 years (with the exception of a nonmelanoma skin cancer that had been treated with no evidence of recurrence for ≥3 months before the first study agent administration or cervical neoplasia with surgical cure).
• Had uncontrolled psychiatric or emotional disorder, including a history of drug and alcohol abuse within the past 3 years that might prevent the successful completion of the study.
• Received, or was expected to receive, any live virus or bacterial vaccination within 3 months before the first administration of study agent, during the study, or within 4 months after the last administration of study agent. Had a BCG vaccination within 12 months of screening.
• Pregnancy, lactation or women of child-bearing potential (WCBP) unwilling to use medically approved contraception whilst receiving treatment and for 12 months after treatment has finished.
• Men whose partners are of child-bearing potential but who are unwilling to use appropriate medically approved contraception whilst receiving treatment and for 12 months after treatment has finished.