A Study to Evaluate the Efficacy and Safety of Hetrombopag Olamine Tablets Vs Placebo in Patients With Chemotherapy-Induced Thrombocytopenia (ExCIT)

Inclusion Criteria: 1. Male or female, age ≥ 18 years at screening. 2. Histologically or cytologically confirmed solid tumor (e.g., non-small-cell lung carcinoma \[NSCLC\], breast, ovarian, bladder, pancreatic, gastrointestinal, or colon/colorectal cancer). 3. Receiving platinum- and/or gemcitabine-containing chemotherapy regimens on 14- or 21-day treatment cycles. 4. Platelet count \< 85 x 109/L at enrollment. 5. For Part B, experiencing a chemotherapy delay of ≥ 7 days due to CIT. 6. At least 2 scheduled chemotherapy cycles of the same treatment regimen as was used prior to enrollment. 7. Eastern Cooperative Oncology Group performance status (ECOG PS) 0-2. 8. Life expectancy ≥6 months. 9. Signed ICF for voluntary participation in the study and good compliance. Exclusion Criteria: 1. WHO Grade ≥ 2 bleeding within 14 days prior to screening. 2. Hematopoietic diseases other than CIT (e.g., primary immune thrombocytopenia). 3. Hematologic malignancies. 4. Thrombocytopenia caused by reasons other than chemotherapy, including but not limited to chronic liver disease, hypersplenism, infection, and hemorrhage, within 6 months prior to Study Day 1. 5. Untreated brain metastases; or with leptomeningeal metastasis. 6. Conditions that require emergent treatment (e.g., superior vena cava syndrome, spinal cord compression). 7. Severe cardiovascular disorders or interventions within 6 months. 8. Have arterial/venous thrombosis with anticoagulation not tolerated for at least 6 weeks. 9. Known bleeding disorders, platelet dysfunction. 10. Severe haemorrhage during screening (e.g., gastrointestinal or intracranial hemorrhage) within 28 days prior to enrolment. 11. Previous treatment with thrombopoietin receptor agonists (TPO-RAs) within 14 days prior to enrolment. 12. Platelet transfusion within 72 hours prior to enrollment. 13. Acute or uncontrolled hepatitis B\&C infection. 14. Human immunodeficiency virus (HIV) infection.