Lapatinib

Lapatinib is a small-molecule tyrosine kinase inhibitor used in cancer therapy. It targets the intracellular kinase domains of EGFR (HER1) and HER2 (ERBB2), inhibiting ATP binding and receptor signaling. By blocking these pathways, it aims to reduce tumor cell growth, particularly in HER2-overexpressing cancers.

In the United States, lapatinib (brand Tykerb) is approved for advanced or metastatic HER2-positive breast cancer in combination with capecitabine after progression on prior therapy. Regional approvals vary, and the drug has been studied in other regimens, including combinations with hormonal therapy.

Administration: Lapatinib is taken orally, 1,250 mg once daily on an empty stomach (at least one hour before or two hours after a meal). Absorption decreases with acid-reducing agents; if needed, separate dosing.

Common adverse effects include diarrhea, rash, fatigue, and nausea. Hepatic toxicity can occur and requires liver-function monitoring. Cardiac effects, such as reduced left ventricular function, have been reported, especially with concurrent trastuzumab. Rare serious skin reactions occur.

Pharmacology and interactions: Lapatinib is metabolized mainly by CYP3A4 and glucuronidation. CYP3A4 inhibitors raise exposure; inducers lower it. Monitor liver and cardiac function during treatment. It is pregnancy category D; contraception is advised during therapy.