Phase III Study on HMPL-523 for Treatment of ITP

Inclusion Criteria:

1. Voluntary signature of written informed consent form;

2. Male or female aged 18~75 years;

3. Performance Status score [Eastern Cooperative Oncology Group (ECOG) score] 0~1;

4. Having been diagnosed as ITP prior to randomization, and duration of disease is morethan 6 months;

5. Intolerance or insufficient response, or recurrence after at least one anti-ITPstandard drug therapy;

6. Patients must have a history of response to previous ITP therapy;

7. One combined anti-ITP therapy is allowed in this study, however, the followingcriteria need to be met:

8. The dose of glucocorticoid has been stable for 4 weeks prior to randomization (<20 mg Prednisone equivalent);

9. The dose of Danazol has been stable for 3 months prior to randomization;

10. The dose of immunosuppressant (only including Azathioprine, Ciclosporin A,Mycophenolate mofetil) has been stable for 3 months prior to randomization.

11. The condition is relatively stable; WHO bleeding scale grade is 0-1; no emergencytreatment is expected within 2 weeks as judged by investigators.

12. The laboratory examinations need to meet the following conditions (no treatment forthis abnormal variable is given within one week prior to blood collection):

13. Average platelet count <30×10^9 /L (and none > 35×10^9 /L unless as a result ofrescue therapy) from at least 3 qualifying counts;

14. Hemoglobin ≥100 g/L, neutrophil count >1.5×10^9/L;

15. Total bilirubin (TBIL), alanine aminotransferase (ALT) and aspartateaminotransferase (AST) ≤1.5×upper limit of normal (ULN);

16. Serum creatinine concentration ≤1.5×ULN and creatinine clearance ≥50 mL/min;

17. Serum amylase and lipase ≤1.5×ULN;

18. International normalized ratio (INR), activated partial thromboplastin time (APTT) not exceeding 20% of normal range.

19. Male or female patients of childbearing potential must agree to use effectivecontraceptive methods during the study and within 90 days after last dose of studydrug, e.g., double barrier contraceptive method, condom, oral or injectablecontraceptives, intrauterine device, etc. Postmenopausal women (>50 years old and nomenses for >1 year) and surgically sterilized women are not subject to thiscondition.

Exclusion Criteria:

1. Evidence on the presence of secondary causes of immune thrombocytopenia;

2. Clinically serious hemorrhage requiring immediate adjustment of platelet (e.g.,hypermenorrhea with significantly decreased hemoglobin);

3. Clinically symptomatic gastrointestinal hemorrhage within 6 months prior toscreening visit (e.g., haematemesis, tarry stool, however, the positive occult bloodtest without any sign or symptom of gastrointestinal hemorrhage will not beconsidered as "clinically symptomatic", or hemorrhoids hemorrhage is one exception);

4. known history of vital organ transplantation or hematopoietic stem cell / bonemarrow transplantation;

5. Has received live vaccine within 8 weeks prior to Day 1 (baseline visit); or planfor immunization with live vaccine during the study;

6. Splenectomy within 12 weeks prior to randomization;

7. Major surgery within 4 weeks prior to the randomization, or plan for major electivesurgery during the study;

8. Previous history of malignant tumors (except for the basal cell carcinoma of skin orcervical carcinoma in situ that have been cured);

9. History of important arterial / venous embolic disease;

10. Intracranial hemorrhage within 6 months before screening visit;

11. History of serious cardiovascular disease (e.g., grade III/IV congestive heartfailure, arrhythmia or angina pectoris requiring drug therapy, unstable anginapectoris, intracoronary stent implantation, angioplasty or coronary artery bypassgrafting, or QTc ≥450 ms);

12. Hypertension that can not be controlled with drugs (systolic blood pressure ≥140mmHg or diastolic blood pressure ≥90 mmHg);

13. Previous history of serious gastrointestinal disease, such as dysphagia, activegastric ulcer, inability to take drugs orally or absorption disorder for oral drugs;

14. Human immunodeficiency virus (HIV) infection, or hepatitis B (in case of positiveHBsAg or HBcAb, positive HBV DNA needs to be determined), or hepatitis C (positiveHCV RNA), or liver cirrhosis;

15. Significant active infection that is not controlled clinically (e.g., sepsis,pneumonia or abscess), or serious infection within 6 weeks prior to randomization (leading to hospitalization or requiring treatment with antibiotic injections);

16. Has received rescue therapy for ITP within 2 weeks prior to randomization; Hasreceived the treatment for the objective of increasing platelet within 4 weeks priorto randomization (including but not limited to glucocorticoid, thrombopoietin,thrombopoietin receptor agonist, Cyclosporine A, Mycophenolate mofetil, etc.),except those meeting the inclusion criterion 7;

17. Having received Rituximab within 14 weeks prior to randomization;

18. Having received traditional Chinese medicine within 1 week prior to randomization;

19. Requiring long-term/continuous use of the drugs that may affect platelet function [including but not limited to aspirin, Clopidogrel, ticagrelor, NSAIDs, etc.], oranticoagulants;

20. Intake of potent CYP3A inhibitor or inducer, as well as sensitive or narrowtherapeutic window substrates of CYP3A, CYP1A2 or CYP2B6 two weeks (three weeks forHypericum perforatum) or 5 half-lives prior to randomization (whichever is longer);

21. Having participated in the clinical study for drugs or invasive medical device 4weeks prior to randomization (or within 5 half-lives of the study drug prior torandomization, whichever is longer);

22. Having received spleen tyrosine kinase Syk inhibitor (e.g., Fostamatinib)previously;

23. Known allergy to the active ingredient or excipient of study drug;

24. Presence of serious psychological or mental disorder;

25. Alcoholic or drug abuser;

26. Female patients in pregnancy or breast feeding;

27. Being unsuitable to participate in this study, as considered by investigators.