Phase I Pharmacokinetic Study of the Safety and Tolerability of Lapatinib (GW572016) in Combination with Oxaliplatin/Fluorouracil/Leucovorin (FOLFOX4) in Patients with Solid Tumors

Abstract

Purpose: This phase I study was designed to determine the optimally tolerated regimen (OTR), safety, and clinical activity of lapatinib in combination with FOLFOX4 [oxaliplatin/leucovorin/ 5-fluorouracil (5-FU)] in patients with solid tumors. Furthermore, the pharmacokinetics of lapatinib, oxaliplatin, and 5-FU when given alone and in combination were evaluated. Experimental Design:This study was conducted in two parts. Part1was designed to determine the OTR and part 2 was the pharmacokinetic part of the study. Lapatinib was administered once daily for the entire duration of the study. Leucovorin and oxaliplatin were given concurrently over 2 h as an i.v. infusion, after which 5-FU was given as a bolus followed by continuous infusion over 22 h on day 1. 5-FU and leucovorin administration were repeated in an identical manner on day 2. Cycles were repeated every 2 weeks. Once the OTR was determined, it was to become the dose level for patients included in the pharmacokinetic part of the study. Results: A total of 34 patients was treated in this study. No dose-limiting toxicities were observed and the OTR was established at 1,500 mg/d lapatinib in combination with the standard FOLFOX4 regimen. Nonhematologic toxicities consisted mainly of nausea, diarrhea, vomiting, fatigue, neuropathy, and mucositis. The most important hematologic toxicity was neutropenia. No drug-drug interactions between lapatinib and the FOLFOX4 regimen were observed. Conclusion: Lapatinib can be safely administered in combination with the standard FOLFOX4 regimen. Further studies are warranted to explore the potential additive antitumor effect of lapatinib in combination with the FOLFOX4 regimen.Molecular target-specific therapeutics have the potential to improve antitumor activity while minimizing toxicity to normal host cells. ErbB1 (epidermal growth factor receptor) and ErbB2 overexpression can promote tumor growth in a variety of epithelial tumors. In some tumors, such overexpression correlates with a poor clinical outcome, making these receptors attractive therapeutic targets (1 -4). Kinase activation of the ErbB1 and ErbB2 receptors leads to interaction with other signal transduction molecules, initiating an intracellular signaling cascade, which promotes proliferation [mitogen-activated protein kinase (extracellular signal-regulated kinase 1/2) pathway] and survival (phosphatidylinositol 3-kinase pathway) of these tumors (5). Therapeutic monoclonal antibodies and small-molecule tyrosine kinase inhibitors targeting ErbB1 and/or ErbB2 have been developed. Monoclonal antibodies target the extracellular domain of the tyrosine kinase receptor, and small molecules compete with ATP for the ATP-binding pocket in the cytoplasmic domain of the receptor (6).Lapatinib (GW572016) is an orally active small molecule that reversibly inhibits the phosphorylation of ErbB1 and ErbB2 tyrosine kinases. IC 50 values against ErbB1 and ErbB2 are 10.2 and 9.8 nmol/L, respectively (7). Because ErbB2-containing heterodimers exert potent mitogenic signals...

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