Phase I Study of SHR-2173 Injection in Patients With Primary Immune Thrombocytopenia

Inclusion Criteria:

1. Participants must fully understand the trial content, procedures, and potentialadverse reactions, and voluntarily sign a written informed consent form (ICF).

2. Age at signing the ICF must be ≥ 18 years (including the boundary value), regardlessof gender.

3. Confirmed diagnosis of primary ITP for at least 3 months at screening.

4. Previous treatment with corticosteroids.

5. At the last ITP treatment, participants experienced loss of remission, no remission,relapse after remission, or intolerance.

6. Platelet count <30×10⁹/L at screening with clinical assessment indicating treatmentnecessity

7. Participants must have adequate organ function

8. Clinically stable condition with World Health Organization (WHO) bleeding scalegrade 0-1

9. Female participants of childbearing potential or male participants with fertilepartners must refrain from sperm/ova donation from ICF signing until 12 weeks afterlast dose and agree to protocol-specified contraceptive measures

Exclusion Criteria:

1. Diagnosis of secondary thrombocytopenia or concomitant autoimmune hemolytic anemia

2. Received platelet transfusion, whole blood transfusion, plasma exchange, or anyother emergency treatment drugs within 14 days prior to the first infusion ofSHR-2173

3. Received immunosuppressants (other than corticosteroids) such as Janus kinase [JAK]inhibitors or Bruton tyrosine kinase [BTK] inhibitors within either 5 times the drugelimination half-life or 14 days prior to the first infusion of SHR-2173 (whicheveris longer)

4. Previous treatment with SHR-2173

5. Screening prothrombin time or activated partial thromboplastin time outside thenormal range; concurrent coagulation disorders and/or receiving antiplatelet oranticoagulant medications (e.g., warfarin, clopidogrel, novel oral anticoagulants),except for low-dose acetylsalicylic acid

6. History of any thrombotic or embolic events within 12 months prior to the firstadministration, or clinical symptoms and history suggesting thrombophilia

7. Current life-threatening bleeding (related to thrombocytopenia) or expected torequire emergency treatment within one week after randomization

8. Active viral, bacterial, or other infections (including tuberculosis [TB]) requiringsystemic treatment at screening, or SARS-CoV-2 infection during screening, orhistory of clinically significant recurrent infections

9. Received live or attenuated live vaccines within 8 weeks prior to the firstadministration of SHR-2173, or planned to receive live/attenuated vaccinationsduring the trial

10. Received live or attenuated live vaccines within 8 weeks prior to the firstadministration of SHR-2173, or planned to receive live/attenuated vaccinationsduring the trial

11. Diagnosis of myelodysplastic syndrome; history of or current malignancy within 5years prior to screening (except for cured non-melanoma skin cancer, in situcarcinoma [e.g., cervical, breast, bladder, prostate cancer], and cancers incomplete remission for at least 5 years with no evidence of recurrence)

12. Previous splenectomy

13. Previous allogeneic stem cell or organ transplantation (except for cornealtransplantation ≥ 3 months prior to screening); known or suspected history ofimmunosuppression

14. Planned surgery during the dosing period

15. Any severe and/or unstable pre-existing medical, psychiatric, or other conditionsthat the investigator judges may interfere with patient safety, obtaining informedconsent, or compliance with study procedures

16. Allergic constitution (e.g., allergies to two or more drugs, foods, or pollens) orknown hypersensitivity (immediate or delayed) or atopic reactions to the study drug (including excipients, monoclonal antibodies)

17. Concurrent participation in other investigational studies within either 30 daysprior to enrollment or 5 half-lives of the investigational drug (whichever islonger)

18. Females who are lactating or pregnant (positive serum or urine β-human chorionicgonadotropin [hCG]) at screening or on Day 1 of Week 1 prior to administration