Journal of Chromatography B, 796 (2003) 181–188 Liquid-chromatographic determination of erlotinib (OSI-774), an epidermal growth factor receptor tyrosine kinase inhibitor Erin R. Lepper, Sandra M. Swain, Antoinette R. Tan, William D. Figg ∗ , Alex Sparreboom Clinical Pharmacology Research Core, Medical Oncology Clinical Research Unit, and Cancer Therapeutics Branch, National Cancer Institute, 9000 Rockville Pike, Building 10, Room 5A01, Bethesda, MD 20892, USA Received 29 April 2003; received in revised form 7 August 2003; accepted 12 August 2003 Abstract A high-performance liquid-chromatographic (HPLC) assay with UV detection has been developed for the quantitative deter- mination of erlotinib (OSI-774) in human plasma. Quantitative extraction was achieved by a single-solvent extraction involving a mixture of acetonitrile and n-butyl chloride (1:4, v/v). Erlotinib and the internal standard hydrochloride salt (OSI-597) were separated on a column packed with Nova-Pak C18 material and a mobile phase composed of acetonitrile and water, pH 2.0 (60:40, v/v). The column effluent was monitored with dual UV detection at wavelengths of 348 nm (erlotinib) and 383 nm (OSI-597). The calibration graph was linear in the range of 100–4500 ng/ml, with values for accuracy and precision ranging from 87.9 to 96.2% and 2.13 to 5.10%, respectively, for three different sets of quality control samples. The developed method was successfully applied to study the pharmacokinetics of erlotinib in a cancer patient at the recommended daily dose of 150 mg. © 2003 Elsevier B.V. All rights reserved. Keywords: Pharmacokinetics; Erlotinib; OSI-774 1. Introduction Phosphorylation of tyrosine residues on the epider- mal growth factor receptor (EGFR) is an important early event in signal transduction, leading to cell replication for major human carcinomas [1]. This receptor is widely expressed in advanced cancers, in- cluding glioma, breast, ovarian, renal, head and neck, and colon carcinoma, and higher levels of EGFR are inversely related to survival in cancer patients [2]. ∗ Corresponding author. Tel.: +1-301-402-3623; fax: +1-301-402-8606. E-mail address: wdfigg@helix.nih.gov (W.D. Figg). There is preclinical evidence that EGFR-mediated signaling plays a critical role in processes affecting tumor growth, including cell adhesion, cell motility, angiogenesis, and apoptosis [3]. Therefore, interrup- tion of this growth signal represents a potential target for anticancer treatment. Over the last several years, at least two general strategies have been used to block the EGFR signaling: (i) by preventing ligand binding with anti-EGFR monoclonal antibodies (e.g. cetuximab) and (ii) by inhibiting its intrinsic tyrosine kinase with small molecules [3]. Among numerous EGFR tyrosine kinase inhibitors synthesized, two agents, viz. gefitinib (ZD1839, Iressa ® ) [4] and er- lotinib hydrochloride (OSI-774, Tarceva ® , formerly 1570-0232/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jchromb.2003.08.015