Inclusion Criteria:
1. Age: 18-75 years (inclusive), voluntary participation with signed informed consent and commitment to protocol-defined visits.
2. Body Weight: ≥40 kg.
3. Diagnosis: Histopathologically/cytopathologically confirmed malignant solid tumors or lymphoma.
4. Phase Ia: Platelet (PLT) \& Treatment Status:
<!-- -->
1. PLT \<75×10⁹/L during prior chemotherapy cycle;
2. Receiving mono/combination chemotherapy (may include targeted/immunotherapy). 5.Phase Ib: Stratified Requirements:
* Group A (1st-line CIT prophylaxis/therapy):
<!-- -->
1. PLT \<50×10⁹/L, or
2. PLT 50-75×10⁹/L. • Group B (2nd-line CIT therapy/refractory cases): Second-line CIT treatment for refractory or treated CIT patients who failed first-line therapy (rhTPO/IL-11) with platelet count \<50×10⁹/L 6.Refractory/Treated CIT Definition:
* Platelet count remains \<50×10⁹/L or increases by \<20×10⁹/L within 14 days after completing first-line CIT therapy (e.g., rhTPO or rhIL-11), with baseline PLT \<50×10⁹/L at enrollment.
7.Toxicity Resolution: Prior anti-tumor toxicity ≤ Grade 2 (CTCAE v5.0) at enrollment (alopecia/vitiligo/subjective symptoms excluded).
8.ECOG PS: 0-2. 9.Life Expectancy: ≥3 months (investigator-assessed). 10.Baseline Laboratory (Pre-dose):
* a) Creatinine ≤1.5×ULN; CrCl \>40 mL/min;
* b) PT/APTT/INR 80-120% of normal range;
* c) ANC ≥1.5×10⁹/L;
* d) Hemoglobin ≥70 g/L;
* e) Albumin ≥25 g/L. 11.Liver Function:
* a) ALT/AST ≤3×ULN (≤5×ULN if liver metastasis);
* b) Total bilirubin ≤2.0×ULN (Gilbert's syndrome/asymptomatic cholelithiasis exempted).
12.Contraception:
* Fertile subjects must use ≥1 method:
o Absolute abstinence;
* Double-barrier (condom + spermicidal diaphragm);
* IUD/hormonal contraceptives (oral/implant/patch/injection);
* Hysterectomy/bilateral salpingectomy/tubal ligation (females or partners);
* Vasectomy/azoospermia (males or partners).
* Females: Negative serum β-HCG within 28 days;
* Males: No sperm donation from first dose to 180 days post-last dose.
Exclusion Criteria:
1. Pregnancy/Lactation: Pregnant or breastfeeding females.
2. Hypersensitivity: Known allergy to protein-based drugs (e.g., recombinant proteins, mAbs) or excipients of the investigational product.
3. Active Infection: Acute infection requiring IV antibiotics without clinical control.
4. Prior Thrombopoietic Agents:
• Group A: Use within specified windows pre-SCB-219M:
o Trilaciclib: ≤3 weeks
o Romiplostim: ≤2 weeks
o TPO-RAs (e.g., eltrombopag), rhTPO, IL-11, or platelet transfusion: ≤10 days
• Group B: Use within:
o Romiplostim/rhTPO/IL-11: ≤7 days
o TPO-RAs/platelet transfusion: ≤3 days
5. Anticoagulant Use: Anticoagulants/antiplatelet drugs ≤5 half-lives pre-dose or needed during study (aspirin washout ≥7 days).
6. Non-Chemotherapy Thrombocytopenia (within 6 months/unresolved):
1\) Clinically significant non-chemotherapy-induced thrombocytopenia (e.g., EDTA-dependent pseudothrombocytopenia) 2) Hematologic malignancies (excluding lymphoma; e.g., leukemia) 3) Multiple myeloma 7.Bleeding Events (within 2 weeks pre-screening):
• Group A: ≥Grade 2 (WHO Bleeding Scale)
* Group B: ≥Grade 3 (WHO Bleeding Scale) 8.Non-CIT Thrombocytopenia Etiologies: 1) Primary immune thrombocytopenia (pITP) 2) Bone marrow failure (e.g., aplastic anemia, Fanconi anemia) 3) Myeloproliferative disorders/MDS 4) Hypersplenism secondary to hematologic/autoimmune diseases 9.Splenectomy/Splenic Effects: Splenic metastasis affecting hematopoiesis; splenectomy/splenic artery embolization ≤12 weeks pre-enrollment.
10.Uncontrolled Cardiovascular Disease:
* NYHA Class III/IV heart failure
* Pro-thrombotic conditions (e.g., atrial fibrillation, unstable angina)
* QTc \>470 ms (\>480 ms with bundle branch block)
* Myocardial infarction ≤6 months (Note: Pacemaker/ICD users with normal function eligible) 11.Thrombotic/Coagulation Disorders:
* Coagulopathies
* Arterial/venous thrombosis ≤3 months (excluding PICC-related thrombosis)
* Transient ischemic attack ≤3 months 12.Major Procedures/Radiotherapy: Major surgery/radiotherapy ≤4 weeks pre-dose (except toxicity ≤Grade 2 \[CTCAE v5.0\], alopecia/vitiligo permitted).
13.CNS Metastases: Active/untreated CNS or leptomeningeal metastases (asymptomatic brain metastases allowed).
14.Uncontrolled Hypertension: Resting SBP ≥160 mmHg and/or DBP ≥100 mmHg (two measurements, 2h apart).
15.Active Infections:
* HIV seropositivity
* Active HBV (HBsAg+ andHBV DNA \>LLOQ)
* Active HCV (anti-HCV+ andHCV RNA \>LLOQ) 16.Live Vaccines: Live attenuated vaccines ≤4 weeks pre-dose (COVID-19 vaccines permitted except Ad5-vectored type \[requires investigator assessment\]).
17.Concurrent Clinical Trials: Participation in other drug/device trials ≤4 weeks pre-dose or planned during study.
18.Investigator's Discretion: Poor compliance or other factors deemed unsuitable for the study.
