MAGNATE-S: Paclitaxel Polymer Micelles Combo in Advanced Sarcoma

Inclusion Criteria: * Informed Consent: The subject has signed the informed consent form after receiving and understanding full explanation regarding the trial's purpose, procedures, anticipated efficacy, pharmacological actions, and risks. * Target Population: 1. Histologically confirmed advanced/metastatic bone or soft tissue sarcoma. (If recurrence or metastasis is not definitive, a biopsy with frozen section is recommended. Enrollment may proceed if frozen pathology suggests recurrence/metastasis.) 2. At least one measurable lesion per RECIST 1.1 criteria. 3. Disease progression after prior first-line standard chemotherapy; ECOG performance status 0-2. 4. Life expectancy ≥ 3 months. 5. Willing and able to comply with study procedures, treatment, and follow-up. 6. No contraindications to paclitaxel polymer micelles, gemcitabine, or small-molecule anti-angiogenic targeted agents. * Physical Examination and Laboratory Results: 1. Adequate hematologic function: i) Absolute neutrophil count (ANC) ≥ 1.8 × 10⁹/L; ii) Platelet count ≥ 100 × 10⁹/L; iii) Hemoglobin ≥ 90 g/L. (If transfusions are given during screening, a repeat test after 1 week must meet these criteria.) 2. Adequate hepatic function: i) Total bilirubin ≤ 1.5 × upper limit of normal (ULN); ii) AST and ALT ≤ 2.5 × ULN (≤ 5 × ULN if liver metastases are present); Alkaline phosphatase (ALP) ≤ 5 × ULN (liver mets) or ≤ 10 × ULN (bone mets). 3. Adequate renal function: Serum creatinine ≤ 1.5 × ULN or calculated creatinine clearance ≥ 50 mL/min. 4. Adequate coagulation: INR ≤ 1.5 × ULN and PT/aPTT ≤ 1.5 × ULN, unless on stable anticoagulant therapy. * Hepatitis B: Subjects positive for HBsAg are eligible if, in the investigator's judgment, their chronic hepatitis B is stable and does not increase the subject's risk. * Cardiac Function: No symptomatic cardiac insufficiency at baseline (NYHA class ≤ II) and no clinically significant ECG abnormalities. * Age and Reproductive Status: 1. Aged 12-70 years (male and female). 2. Subjects of childbearing potential must agree to use effective contraception during the trial. A negative serum or urine pregnancy test within 24 hours before chemotherapy is required for women of childbearing potential. 3. Female subjects must not be breastfeeding. Exclusion Criteria: * Known allergy or intolerance to any component or excipient of the investigational products. * Primary brain tumor or central nervous system (CNS) metastases (including leptomeningeal metastases), except for a single, well-controlled, asymptomatic brain metastasis. CNS tumors still presenting with increased intracranial pressure or neuropsychiatric symptoms after treatment. * Uncontrolled acute or chronic infections, or other severe concurrent medical conditions. * History of other malignancies within the past 5 years, except for cured basal cell carcinoma of the skin or carcinoma in situ of the cervix. * Active hepatitis or hepatic tumor burden exceeding 50% of the total liver volume. * Uncontrolled third-space fluid accumulation not manageable by drainage (e.g., moderate to large pleural effusion, pericardial effusion, or ascites). Minimal asymptomatic fluid not requiring intervention may be allowed upon strict review. * Psychiatric illness or cognitive impairment leading to poor compliance or inability to cooperate and report treatment responses. * Severe organic disease or major organ failure (e.g., decompensated heart or lung failure) precluding tolerance to chemotherapy. * Coagulopathy (INR \>1.5, APTT \>1.5 × ULN), bleeding tendency (e.g., active gastric ulcer, stool occult blood \[++\], hematemesis and/or melena within the past 3 months, hemoptysis), or tumor proximity to major blood vessels. * Coronary artery disease above grade I, arrhythmia (including QTc interval \>450 ms for males, \>470 ms for females), use of antiarrhythmic medication, or relevant underlying cardiac disease/cardiac insufficiency. * Renal insufficiency, history of renal disease, or proteinuria (urine protein ≥2+ or 24-hour urine protein \>1.0 g). * History of organ transplantation. * History of substance abuse, chronic alcoholism, or infectious diseases such as AIDS. * Long-term use of corticosteroids or immunosuppressants. * Vaccination with live or attenuated vaccines (e.g., measles, mumps, rubella, varicella, yellow fever, rabies, BCG, oral typhoid) within 4 weeks prior to enrollment, or planned vaccination during the study. COVID-19 vaccination is permitted. * Active hepatitis B (HBV DNA ≥1×10⁴ copies/mL or ≥2000 IU/mL) or hepatitis C (HCV RNA ≥15 IU/mL) infection; positive HIV antibody (unless clinically indicated); or positive syphilis antibody (TPPA). * Any other condition deemed by the investigator to prevent completion of the trial or render the subject unsuitable (e.g., tumors like GIST or ALK-mutant inflammatory myofibroblastic tumor unsuitable for this chemotherapy regimen).