Single-arm, open-label, single-center study to evaluate the efficacy and safety of baricitinib for the treatment of adults with steroid-resistant/relapse immune thrombocytopenia (ITP).

The investigators are undertaking a prospective trial of 20 adults with ITP in China. Baricitinib is administered as 4 mg po. daily. Safety outcomes and efficacy outcomes are assessed on scheduled study visits (primary endpoint defined as durable response at 6-month follow-up).

Inclusion Criteria:

1. Primary immune thrombocytopenia (ITP) confirmed by excluding other supervened causes of thrombocytopenia
2. Patients with chronic low platelet count (<30,000/μL) for 6 months who have failed at least one treatment for chronic low platelet count
3. Patients who did not achieve a sustained response to treatment with full-dose corticosteroids for a minimum duration of 4 weeks or who relapsed during steroid-tapering or after its discontinuation
4. Patients with a platelet count <30,000/μL or a platelet count <50,000/μL with clinically significant bleeding symptoms at the enrollment
5. Over 18 years old
6. Willing and able to provide written informed consent, and agreeable to the schedule of assessment

Exclusion Criteria:

1. Secondary immune thrombocytopenia (e.g. patients with HIV, HCV, Helicobacter pylori infection or patients with confirmed autoimmune disease)
2. Active or a history of malignancy
3. Pregnancy or lactation
4. Current or recent (<4 weeks prior to screening) clinically serious viral, bacterial, fungal, or parasitic infection
5. A history of symptomatic herpes zoster infection within 12 weeks prior to screening
6. Active or chronic viral infection from hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV)
7. Have evidence of active tuberculosis (TB), or have previously had evidence of active TB and did not receive appropriate and documented treatment, or have had household contact with a person with active TB and did not receive appropriate and documented prophylaxis for TB
8. Have experienced a clinically significant thrombotic event within 24 weeks of screening or are on anticoagulants and in the opinion of the investigator are not well controlled
9. Myocardial infarction (MI), unstable ischemic heart disease, stroke, or New York Heart Association Stage IV heart failure
10. A history or presence of cardiovascular, respiratory, hepatic, gastrointestinal, endocrine, neurological, or neuropsychiatric disorders or any other serious and/or unstable illness that, in the opinion of the investigator, could constitute an unacceptable risk when taking investigational product or interfere with the interpretation of data
11. Any of the following specific abnormalities on screening laboratory tests:

1) ALT or AST >2 x ULN, or total bilirubin ≥1.5 x ULN 2) hemoglobin <9 g/dL, or total white blood cell (WBC) count <2,500/µL, or neutropenia (absolute neutrophil count <1,200/µL), or lymphopenia (lymphocyte count <750/µL) 3) eGFR <50 mL/min/1.73 m^2