Erlotinib: A Targeted Anticancer Drug

Background: Over expression of epidermal growth factor receptor (EGFR) has been found to play a vital role in cancer of lung and pancreas. Therapies that target EGFR-mediated signalling are the latest keystone for treating these two types of cancer. Methodology: Erlotinib is an EGFR tyrosine kinase inhibitor, a promising anticancer agent either alone or as combination therapy for the treatment of both lung and pancreatic cancers especially in EGFR mutated patients. It acts by blocking the action of an EGFR, which helps the cancer cells to grow and divide. Erlotinib solubility is pH dependent; which decreases with the increasing pH. It is a quinazolinamine derivative and exists as hydrochloride in the market which on oral administration has absorption of ~ 60% in plasma and also found to achieve appropriate therapeutic concentrations in Cerebrospinal fluid (CSF) required for intracranial responses. With adverse reactions like diarrhea and skin rashes that occur most commonly, erlotinib is usually a welltolerated therapy. It is associated with several kinds of drug interactions, generally associated with smoking, the enzyme inhibiting drugs, enzyme inducing drugs, etc. leading to alteration in the pharmacokinetic profile of erlotinib. Conclusion: In nonclinical toxicology studies, the drug has not shown any results of fertility impairment, carcinogenesis or mutagenesis. Though the EGFR-TKIs have shown great clinical significance, the development of drug resistance has also been reported by the patients. The resistance for EGFR-TKIs can occur through any of the several mechanisms involved like secondary mutation (T790M), ATP binding cassette transporter effusion, alteration of the downstream pathways, etc. This article reviews the safety and efficacy of erlotinib along with chemistry, mechanism, pharmacokinetics, drug interactions and resistance to the drug.