This is a prospective, randomized, controlled trial. ITP patients who failed prior full-does TPO-RA monotheray for 14 days. Patients are randomly assigned at a 1:1 ratio to receive baricitinib plus TPO-RA or TPO-RA alone. Patients are randomly assigned at a 1:1 ratio to receive baricitinib plus TPO-RA or TPO-RA alone. The primary endpoint was the 14-day overall response rate without any rescue therapy.

This is a prospective, randomized, controlled trial.Eligible patients were at least 18 years old, had a diagnosis of primary ITP and did not respond after receiving TPO-RA (hetrombopag or eltrombopag) at the full dose (hetrombopag 7.5mg per day or eltrombopag 75 mg per day) for 14 days (platelet count below 30×10^9/L or a value less than a 2-fold increase from their baseline platelet count). Patients are randomly assigned at a 1:1 ratio to receive baricitinib plus TPO-RA or TPO-RA alone. Both groups will continue their prior full-dose TPO-RA therapy for 14 days (day 1-14), while baricitinib was given orally at a dose of 2 mg twice daily concomitantly in the combination group for 14 days (day 1-14). The primary endpoint was the 14-day overall response rate without bleeding and any rescue therapy. The secondary endpoints included the 28-day overall response rate, 14-day complete response rate, the 28-day complete response rate, time to response, WHO bleeding scores, health-related quality of life, and adverse events.

Inclusion Criteria:

1. ≥18 years old;
2. Patients diagnosed with primary ITP who failed to achieve a response after 14 days of full-dose TPO-RA therapy;
3. Patients with baseline platelet count less than 30×10⁹/L, or those with baseline platelet count ranging from 30×10⁹/L to 50×10⁹/L accompanied by clinically significant bleeding (WHO bleeding score ≥2).

Exclusion Criteria:

• Pregnant or lactating women, and who were possibly pregnant, planning to become pregnant, or who had partners planning to become pregnant;
• With active malignancy or a history of malignant tumor;
• Having experienced severe bacterial, viral, fungal or parasitic infection within the past 4 weeks;
• With a history of symptomatic herpes zoster infection within 12 weeks prior to screening;
• Active or chronic HBV, HCV or HIV infection;
• Evidence of active tuberculosis; or previous evidence of active tuberculosis without appropriate and documented treatment; or household contact with patients with active tuberculosis without appropriate and documented tuberculosis prophylaxis;
• Receipt of live vaccines within the past 12 weeks, or planned live vaccination during the study period;
• Prior baricitinib therapy;
• History of solid organ transplant or planned surgery;
• Myelodysplastic syndrome, aplastic anemia or myelofibrosis;
• Patients with other diseases were undergoing treatment with immunosuppressants;
• Clinically significant thromboembolic events within the past 24 weeks, or ongoing anticoagulant treatment, who are deemed ineligible for the study by the investigator;
• History or presence of myocardial infarction, unstable ischemic heart disease, stroke, or NYHA Class IV heart failure;
• History or active manifestations of severe or unstable cardiovascular, respiratory, hepatic, gastrointestinal, endocrine, neurological, neuropsychiatric, or other medical conditions that, in the investigator's judgment, could confer unacceptable safety risks with the investigational product or confound the interpretation of study data;
• AST > 2 times the upper limit of normal (ULN), ALT > 2×ULN, TBIL ≥ 1.5×ULN;
• eGFR < 50 mL/min/1.73m²;
• Other patients deemed unsuitable for enrollment in this study by the investigator.