Phase II Study of Orelabrutinib in Combination With Romiplostim N01 in Patients With Primary Immune Thrombocytopenia (ITP) Who Have Received At Least One Prior Line of Therapy

This is a prospective, single-arm, open-label Phase II study, enrolling adult patients with chronic primary immune thrombocytopenia (ITP) who failed first-line therapy. The study evaluates the efficacy and safety of orelabrutinib combined with romiplostim N01, focusing on the treatment regimen as follows:

• Core Treatment Phase (Weeks 1-24) Patients receive orelabrutinib 50mg orally once daily (fixed dose) and romiplostim N01 subcutaneously. Romiplostim N01 starts at 250ug/week (≈3ug/Kg) and is titrated within 1-10ug/Kg/week to maintain platelet count (PLT) at 50-200×10⁹/L. Dose adjustments: increase by 1-3ug/Kg/week if PLT <50×10⁹/L; decrease by 1-3ug/Kg/week if PLT 200-400×10⁹/L; suspend if PLT >400×10⁹/L. Patients with PLT <50×10⁹/L after 28 days of maximum-dose romiplostim N01 withdraw.
• Romiplostim N01 Tapering Phase (Weeks 25-32) Patients with PLT ≥50×10⁹/L in the last two core phase visits discontinue orelabrutinib. Romiplostim N01 is tapered: doses >3ug/Kg/week are reduced to 2-3ug/Kg/week, then dosing intervals extended (weekly→every 10 days→every 2 weeks). Patients with two consecutive PLT <30×10⁹/L withdraw.
• Follow-up Phase (Weeks 33-56) Successfully tapered patients are followed up every 4 weeks to monitor PLT and adverse events (graded per NCI-CTC AE 5.0). Relevant events are reported to the sponsor's Pharmacovigilance Department.

Inclusion criteria

• Subjects voluntarily participate in this study and provide written informed consent；
• Age 18-80 years, inclusive, regardless of gender；
• ECOG score 0 to 2；
• Documented diagnosis of chronic primary Immune Thrombocytopenia (ITP) with a disease duration >12 months；
• Patients with an inadequate sustained response, relapse, intolerance, or insufficient response to first-line ITP therapy (corticosteroids and/or intravenous immunoglobulin). Prior receipt of other ITP treatments is allowed, with no limit on the number of prior lines；
• A history of response to prior standard ITP therapy (defined as achieving a platelet count ≥50×10⁹/L)；
• During or following the most recent ITP treatment, patients must have experienced either: treatment failure (platelet count <30×10⁹/L after treatment, or failure to double the baseline count, or occurrence of bleeding), relapse after initial response (platelet count decreased to <30×10⁹/L, or fell below twice the baseline, or bleeding symptoms recurred), treatment intolerance, or an inability to maintain response after treatment discontinuation；
• Subjects demonstrate adequate comprehension of and are able to comply with the study protocol requirements, and are willing to complete the study according to the schedule.

Exclusion criteria

• Subjects suffer from severe ITP at screening;
• Subjects have other diseases which mention in protocol;
• Subjects develop intracranial hemorrhage within 6 months prior to screening;
• Active and uncontrollable infection;

• Subjects have a history of coagulopathy other than ITP; 7. Subjects with a history of malignancies; 8. History of major organ transplantation or hematopoietic stem cell/bone marrow transplantation; 9. Subjects with a known history of hypersensitivity to the investigational drug as described in the Protocol, or any ingredients; 10. Subjects with a Medication history and surgical history which mention in protocol; 11. Subjects do not meet the criterion of the laboratory test in protocol.

Withdrawal Criteria:

• If, after 4 consecutive weeks of Romiplostim N01 administration at the maximum dose (10 µg/kg once weekly), the platelet count remains <50×10⁹/L and the investigator judges the investigational product to be ineffective for the subject, such that continued use is not in the subject's best interest；
• Subjects who are unable to successfully undergo treatment tapering or discontinuation；
• Subjects who, during the treatment period, require rescue therapy based on clinical assessment；
• Subjects who withdraw their informed consent.
• Occurrence of pregnancy during the trial period
• Poor subject compliance or a significant protocol violation；
• Loss to follow-up；
• The investigator decides that withdrawal is necessary for the subject's safety；
• Presence of other conditions, as determined by the investigator, that may affect the study results or lead to premature termination of the study；
• Study completion or early termination of the entire study.