**Core Concept**
The Her-1 (also known as EGFR) and Her-2 (also known as HER2/neu) receptors are members of the epidermal growth factor receptor (EGFR) family, which play a crucial role in cell proliferation, differentiation, and survival. These receptors are transmembrane tyrosine kinases that, upon ligand binding, undergo autophosphorylation and activate downstream signaling pathways, including the MAPK and PI3K/AKT pathways.

**Why the Correct Answer is Right**
Trastuzumab is a monoclonal antibody that targets the extracellular domain of the Her-2 receptor, preventing its dimerization and subsequent activation. Although primarily known for its action on Her-2, trastuzumab also has a high affinity for Her-1, making it a dual-HER receptor inhibitor. This dual activity is thought to contribute to its efficacy in treating HER2-positive breast cancer. The mechanism of action involves binding to the ligand-binding domain of the Her-2 receptor, preventing its activation and downstream signaling.

**Why Each Wrong Option is Incorrect**
**Option A:** Lapatinib is a dual inhibitor of Her-1 and Her-2, but it acts through a different mechanism, inhibiting the tyrosine kinase activity of both receptors.
**Option B:** Pertuzumab is a monoclonal antibody that targets the dimerization domain of the Her-2 receptor, preventing its heterodimerization with Her-1, but it does not act on Her-1 itself.
**Option C:** Neratinib is a potent inhibitor of Her-1 and Her-2 tyrosine kinase activity, but it is primarily used in the context of Her-2-positive breast cancer and does not have a high affinity for Her-1.
**Option D:** Docetaxel is a taxane chemotherapy agent that inhibits microtubule dynamics, but it does not have a direct action on Her-1 or Her-2 receptors.

**Clinical Pearl / High-Yield Fact**
Trastuzumab is a key treatment option for HER2-positive breast cancer, and its dual-HER receptor inhibition is thought to contribute to its efficacy. It is essential to recognize the unique mechanisms of action of different HER receptor inhibitors to optimize treatment strategies.

**Correct Answer: B. Pertuzumab is a monoclonal antibody that targets the dimerization domain of the Her-2 receptor, preventing its heterodimerization with Her-1, but it does not act on Her-1 itself.