eligibility_summary
Adults 18–75 with pathology/cytology-confirmed breast cancer, progressed after trastuzumab in advanced disease or ≤12 months after (neo)adjuvant trastuzumab, prior taxane, progression/intolerance on last regimen, ≥1 RECIST 1.1 measurable lesion. Exclude prior A166 or HER2 ADCs with microtubule payload, severe mAb hypersensitivity or A166/T-DM1 allergy, trastuzumab stopped for toxicity, severe corneal disease/need contacts, spinal cord compression/active CNS mets, or investigator judgment.
trial_source
clinical_trials.gov from Dec 2, 2025
annotation_status
ai
ai_summary
Phase 3 randomized trial comparing two HER2-directed antibody-drug conjugates (ADCs) in HER2+ unresectable/metastatic breast cancer post trastuzumab+taxane. Interventions: A166 (IV q3w, 4.8 mg/kg) vs trastuzumab emtansine/T-DM1 (IV q3w, 3.6 mg/kg). Mechanisms: A166—HER2-targeted ADC that binds HER2 on tumor cells, is internalized, and releases a microtubule-inhibiting cytotoxic payload to cause mitotic arrest and apoptosis. T-DM1—HER2-targeted ADC linking trastuzumab to DM1 (maytansinoid microtubule inhibitor) with the same targeted delivery mechanism. Cells/pathways targeted: HER2-overexpressing breast cancer cells, HER2 receptor on tumor cells, disruption of intracellular microtubule dynamics/mitotic spindle leading to inhibition of proliferation and cell death.