Inclusion Criteria:
Cohort 1 :
* Voluntarily participate in this study with signed informed consent form (ICF) and demonstrated good compliance.
* Age ≥18 years (calculated from the date of ICF signing); no gender restrictions; Eastern Cooperative Oncology Group (ECOG) performance status 0-1.
* Clinically stable condition with WHO bleeding scale score 0-1, and investigator assessment indicates no need for emergency treatment within the next 2 weeks.
* No increase in the type, dosage, or frequency of concomitant ITP medications compared to the TQB3473-III-01 study regimen.
* Previous participation in the TQB3473-III-01 study with either: Sustained platelet count \<30×10⁹/L during the 12-week pre-randomization period (\<50×10⁹/L if emergency treatment was received), or completion of 24-week double-blind treatment with investigator-confirmed benefit-risk assessment favoring continued therapy.
* Adequate major organ function as defined by protocol criteria.
* For women of childbearing potential: Must agree to use highly effective contraception from screening through 6 months after treatment completion and refrain from oocyte donation for reproductive purposes during this period; must not be breastfeeding with negative serum/urine pregnancy test within 7 days prior to enrollment. For male participants with fertile partners: Must agree to use effective contraception during the study and for 6 months thereafter.
Cohort 2 ：
* Subjects voluntarily participate in this study upon signing the Informed Consent Form (ICF) with demonstrated compliance.
* Age ≥ 18 years (calculated from signing date of ICF); No gender restrictions; ECOG performance status score 0-1.
* Confirmed diagnosis of primary ITP \>3 months prior to enrollment.
* Clinically stable condition with WHO bleeding score 0-1, no major bleeding episodes within 4 weeks pre-randomization, and investigators confirm no anticipated need for emergency treatment within 2 weeks.
* Meeting all platelet criteria: Mean platelet count \<30×10⁹/L (no single value \>35×10⁹/L) from ≥2 independent measurements (≥3 days apart) within 7 days pre-enrollment Confirmed platelet count \<30×10⁹/L within 24 hours before enrollment.
* Documented failure or relapse after ≥1 prior standard ITP therapy.
* Adequate function of major organs per protocol definitions.
* Permitted ≤1 concurrent ITP treatment (any class), provided: Stable dose maintained for ≥4 weeks prior to enrollment (≥2 weeks for corticosteroids)
* For women of childbearing potential: Must agree to use highly effective contraception from screening through 6 months after treatment completion and refrain from oocyte donation for reproductive purposes during this period; must not be breastfeeding with negative serum/urine pregnancy test within 7 days prior to enrollment. For male participants with fertile partners: Must agree to use effective contraception during the study and for 6 months thereafter.
Exclusion Criteria:
* Cohort 1 :
1. Due to reasons other than lack of efficacy, receiving TQB3473-III-01 study treatment for less than 12 weeks.
2. Hepatitis B Virus (HBV) DNA or Hepatitis C Virus (HCV) RNA detection values exceeding the upper limit of normal or decompensated cirrhosis
3. Previous intracranial hemorrhage or severe bleeding of other important organs (≥ CTC AE grade 3), or symptomatic gastrointestinal bleeding (such as vomiting blood, black stool, etc., except for asymptomatic and asymptomatic "occult blood test positive" and hemorrhoids) within the 6 months before enrollment.
4. Suffering from major cardiovascular and cerebrovascular diseases.
5. There are multiple factors that can affect oral medication, such as inability to swallow, chronic diarrhea, and intestinal obstruction.
6. Those who have received major surgical treatment, significant traumatic injury, or are expected to undergo major elective surgery during the study treatment period within the 4 weeks prior to enrollment
7. Uncontrolled significant active infections (such as sepsis, pneumonia, or abscess), or severe infections within the 12 weeks prior to enrollment (resulting in hospitalization or requiring antibiotic treatment).
8. Vaccination was administered within 8 weeks prior to enrollment, or planned during the study period.
9. Received blood transfusions or blood products within 2 weeks prior to enrollment (excluding IVIg used for emergency treatment).
10. Take strong CYP3A inhibitors or inducers (3 weeks for Forsythia suspensa) for 2 weeks or 5 half lives (whichever is longer) before enrollment.
11. Long term/continuous treatment with drugs that affect platelet function (including but not limited to aspirin, clopidogrel, ticagrelor, NSAIDs, etc.) or anticoagulant therapy is required.
12. Allergic constitution or history of severe allergies, or known allergies to the components of the investigational drug excipients.
13. There are clear neurological or mental disorders, or serious psychological or mental abnormalities.
14. Alcoholic or drug abusers.
15. According to the researcher's perspective, other severe, acute, or chronic medical or mental illnesses or laboratory abnormalities that may increase the risks associated with participating in the study or interfere with the interpretation of the research results.
16. It is estimated that the patient's compliance in participating in this clinical study is insufficient.
Cohort 2：
* There is evidence to suggest the presence of secondary causes of ITP in the subjects, or immune cell depletion of two or more lineages, such as Evans syndrome;
* Past or current presence of myelofibrosis, myelodysplastic syndrome, aplastic anemia, lymphoproliferative disorders, or other malignant hematological diseases.
* Have had or currently have malignant tumors within the past 3 years. The following two situations can be included in the group: other malignant tumors treated with a single surgery, achieving continuous 5-year disease-free survival (DFS); Cured cervical carcinoma in situ, non melanoma skin cancer, and superficial bladder tumors \[Ta (non-invasive tumor), Tis (carcinoma in situ), and T1 (tumor infiltrating basement membrane)\].
* HBV DNA or HCV RNA detection values exceeding the upper limit of normal or decompensated cirrhosis.
* Previous intracranial hemorrhage or severe (≥ Common Terminology Criteria (CTC) AE grade 3) bleeding of other important organs, or symptomatic gastrointestinal bleeding (such as vomiting blood, black stool, etc., except for asymptomatic and asymptomatic "occult blood test positive" and hemorrhoids) within the 6 months before enrollment.
* Suffering from major cardiovascular and cerebrovascular diseases.
* There are multiple factors that can affect oral medication, such as inability to swallow, active gastric ulcers, major gastrointestinal surgeries, chronic diarrhea, and intestinal obstruction.
* ITP related symptoms and treatment:
* Received ITP emergency treatment within 2 weeks prior to enrollment;
* Received platelet transfusion within 2 weeks prior to enrollment;
* Received immunoglobulin or traditional Chinese medicine treatment within 2 weeks before enrollment;
* Used rituximab or other anti-Cluster of Differentiation 20 (CD20) drugs within 14 weeks prior to enrollment;
* Received splenectomy within 12 weeks prior to enrollment;
* Individuals who have received glucocorticoids within the 2 weeks prior to enrollment, or have received thrombopoietin drugs (rhTPO, eltrombopag, hetrombopag, avatrombopag, romiplostim), immunomodulators (azathioprine, cyclosporine A, mycophenolate mofetil), chemotherapy drugs (decitabine, vinblastine), danazol, etc. within the 4 weeks prior to enrollment, except for those who meet the inclusion criteria 8 and are allowed to undergo concomitant treatment.
* Adverse reactions from previous treatments that have not recovered to ≤ CTCAE grade 1, as well as non clinically significant and asymptomatic laboratory abnormalities that have been determined by researchers to pose no safety risks, are excluded.
* Patients who have received major surgical treatment, significant traumatic injury, or are expected to undergo major elective surgery during the study treatment period within the 4 weeks prior to enrollment (major surgery is defined as surgery at level 3 or above in the National Surgical Classification Catalogue 2022 edition).
* Vaccination was administered within 8 weeks prior to enrollment, or planned during the study period.
* Uncontrolled significant active infections (such as sepsis, pneumonia, or abscess), or severe infections within the 12 weeks prior to enrollment (resulting in hospitalization or requiring antibiotic treatment).
* Received blood transfusions or blood products within 2 weeks prior to enrollment (excluding intravenous immunoglobulin (IVIg) used for emergency treatment).
* Take strong Cytochrome P450 3A (CYP3A) inhibitors or inducers (3 weeks for Forsythia suspensa) for 2 weeks or 5 half lives (whichever is longer) before enrollment.
* Participants who have participated in and used other clinical trial drugs within 4 weeks prior to enrollment.
* Long term/continuous treatment with drugs that affect platelet function (including but not limited to aspirin, clopidogrel, ticagrelor, NSAIDs, etc.) or anticoagulant therapy is required.
* Allergic constitution or history of severe allergies, or known allergies to the components of the investigational drug excipients.
* History of important organ transplantation or hematopoietic stem cell/bone marrow transplantation.
* History of immunodeficiency, including HIV positivity or other congenital immunodeficiency diseases.
* Individuals with epilepsy who require treatment.
* There are clear neurological or mental disorders, or serious psychological or mental abnormalities.
* Alcoholic or drug abusers.
* According to the researcher's perspective, other severe, acute, or chronic medical or mental illnesses or laboratory abnormalities that may increase the risks associated with participating in the study or interfere with the interpretation of the research results.
* It is estimated that the patient's compliance in participating in this clinical study is insufficient.
