erlotinib

Erlotinib is an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor used in cancer therapy. It binds reversibly to the ATP-binding site of EGFR, inhibiting phosphorylation and downstream signaling that promote tumor cell proliferation and survival. The drug is marketed under the brand name Tarceva.

Erlotinib is approved for the treatment of adults with certain cancers, most notably metastatic non-small cell lung cancer (NSCLC) and advanced pancreatic cancer in combination with gemcitabine. It is used in tumors that express activating EGFR mutations or as later-line therapy in other EGFR contexts, depending on regional guidelines and regulatory approvals.

Administration typically involves a once-daily dose, commonly 150 mg for NSCLC and 100 mg daily when used with gemcitabine for pancreatic cancer. The medication is taken by mouth on an empty stomach; food increases absorption and may raise toxicity. Gastric acid–suppressing medications can reduce erlotinib exposure, so they are generally avoided or their administration is separated from erlotinib by several hours.

Pharmacokinetics: erlotinib is absorbed orally and extensively metabolized in the liver, mainly by CYP3A4 (with contribution from CYP1A1/2). It has a terminal half-life of about 36 hours, supporting once-daily dosing. Dose adjustments may be needed in hepatic impairment and in the context of drug interactions.

Adverse effects include rash and acneiform dermatitis, diarrhea, anorexia, and fatigue. Serious but less common effects include interstitial lung disease, hepatotoxicity, and ocular disorders. Smoking reduces erlotinib exposure and may decrease efficacy; strong CYP3A4 inducers or inhibitors can markedly alter drug levels.