Eligibility requires ECOG 0-1, HER2-expressing tumors (IHC3+/2+), measurable lesions (RECIST 1.1), and adequate organ function. Key exclusions include prior HER2-targeted therapy with grade &ge;3 toxicity, uncontrolled CNS metastases, major surgery <28 days, active HBV/HCV/syphilis infection, NYHA II-IV heart failure, interstitial lung disease, or pregnancy. Recent anti-tumor therapies (<28 days) or radiopharmaceuticals (<8 weeks) are prohibited, with investigator discretion for other compromising conditions.

The study defines dose-limiting toxicity (DLT) as grade 5 toxicity, grade 4 hepatotoxicity (ALT/AST >5xULN with bilirubin elevation), prolonged grade 4 hematologic toxicities (>7 days), febrile neutropenia, or any grade ≥3 non-hematologic toxicity. The maximum tolerated dose (MTD) is identified as the highest dose where DLTs occur in ≤1/6 subjects within the 3-week evaluation period.

Pharmacokinetic analysis monitors Cmax per 3-week cycle up to 18 weeks, while immunogenicity tracks ADA/NAb levels throughout treatment (cycles 1-18 weekly, then every 4 cycles up to 1 year). Efficacy endpoints include ORR (CR+PR rates at 18 weeks and overall), DoR (response duration until progression/death), DCR (CR+PR+SD), PFS (time to progression/death), and OS (time to death from any cause) over a 2-year average follow-up.

Eligible patients must be &ge;18 years with ECOG 0-1, HER2-positive tumors (IHC3+/2+ &plusmn; FISH), measurable lesions (RECIST 1.1), and adequate organ function. Key exclusions: prior HER2-targeted therapy with grade &ge;3 toxicity/LVEF <50%, uncontrolled CNS metastases, major surgery (<28 days), active infections (HBV/HCV/syphilis), NYHA II-IV cardiac dysfunction, or interstitial lung disease. Prohibited concurrent therapies include recent anti-tumor treatments (<28 days), radiopharmaceuticals (<8 weeks), and pregnancy/lactation, with investigator discretion for other high-risk conditions affecting compliance.

Safety assessments include monitoring dose-limiting toxicities (DLT) during the first 21-day cycle, tracking abnormal vital signs (including blood pressure, pulse, temperature), physical examinations, adverse events (AEs) from first dose until 28 days post-treatment or new therapy initiation, and clinical lab abnormalities (hematology, biochemistry) over 1 year, alongside efficacy metrics like duration of response (DOR) and disease control rate (DCR) tracking tumor response stability and shrinkage.

Pharmacokinetic profiling evaluates Cmax, Tmax, clearance rate (CL), and half-life (T1/2) at multiple timepoints across cycles 1-6 and end-of-treatment (17 cycles of 2 weeks each). Immunogenicity testing measures anti-drug antibodies (ADA) and neutralizing antibodies (NAb) at cycle starts (cycles 1-3, 5-6) and EOT to assess drug exposure and immune response patterns over the treatment trajectory.