Trastuzumab (Herceptin) is used in HER2-positive breast cancer. Its mechanism involves:

• A Competitive inhibition of the HER2 kinase ATP-binding domain intracellularly
• B Internalization and degradation of all ErbB family receptors via pan-HER inhibition
• C Downregulation of VEGF expression in HER2-positive tumors
• D Binding to the extracellular domain IV of HER2, blocking homodimerization and signaling; also mediating ADCC ✓

Explanation

Trastuzumab is a humanized monoclonal antibody that binds to subdomain IV (the juxtamembrane region) of the extracellular domain of the HER2 receptor (ErbB2). This prevents receptor homodimerization and signaling, and also recruits immune effector cells via Fc receptor binding (antibody-dependent cellular cytotoxicity, ADCC). Pertuzumab binds subdomain II (heterodimerization domain). Lapatinib is the small-molecule intracellular TKI targeting HER2. Cardiotoxicity (cardiomyopathy) is a serious adverse effect.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.