A Clinical Trial to Evaluate the Safety, Efficacy, and Pharmacokinetics of MegaLT Injection for Treating Refractory Thrombocytopenia Following Radiotherapy, Chemotherapy, or Transplantation.

Inclusion Criteria: * Age between 4 and 75 years (inclusive) at screening; gender is not restricted; * Diagnosed with refractory thrombocytopenia following radiotherapy/chemotherapy or transplantation; * Adequate organ function：Alanine aminotransferase (ALT) or Aspartate aminotransferase (AST) \< 2.5\*upper limit of normal (ULN); Serum creatinine \< 1.5\* ULN; Total bilirubin level \< 1.5\* ULN; Coagulation function: International Normalized Ratio (INR) ≤ 1.5\* ULN, Activated Partial Thromboplastin Time (APTT) ≤ 1.5\*ULN; Hemoglobin ≥ 60 g/L, or hemoglobin maintained at this level after transfusion; Absolute neutrophil count (ANC) ≥ 1.0×10\^9/L; * Eastern Cooperative Oncology Group (ECOG) performance status of 0-2; * Voluntarily participating in the clinical trial, with full understanding of the trial details and having signed the informed consent form. Exclusion Criteria: * Patients with any malignant tumor relapse; * Pregnant or breastfeeding women; * Life expectancy less than 3 months; * Severe infections or severe concurrent conditions such as heart, liver, lung, kidney, neurological, or metabolic diseases; * History of severe thrombotic events or known thrombotic risk factors. Exceptions: Participants for whom the potential benefits of the study, as determined by the investigator, outweigh the potential risks of thromboembolic events; * Uncontrolled infectious or other serious diseases, including but not limited to infections (e.g., HIV positive), congestive heart failure, unstable angina, arrhythmias, psychiatric disorders, or conditions that limit the ability to meet study requirements or pose unpredictable risks as judged by the primary physician; * Active hepatitis B or C infection; * Refractory thrombocytopenia post-transplant with Grade III-IV acute graft-versus-host disease (GVHD) \[according to NIH standards\] or severe chronic GVHD (NIH 2014 standards); * History of organ transplantation or planned organ transplantation (excluding hematopoietic stem cell transplantation); * Participation in another clinical study within 30 days prior to the baseline visit, involving any investigational drug or device; observational studies are allowed; * Any other conditions deemed by the investigator to make the participant unsuitable for the clinical trial.