Targeting the epidermal growth factor receptor: prognostic and clinical implications

Overview of the tolerability of gefitinib (IRESSA) monotherapy : clinical experience in non-small-cell lung cancer

Cytotoxic chemotherapy treatment options for patients with non-small-cell lung cancer (NSCLC) have limited efficacy and are often associated with significant toxicity. Therefore, there is an unmet need for novel drugs that are not only effective in treating this disease but are also well tolerated. Gefitinib is an orally active epidermal growth factor receptor tyrosine kinase inhibitor that blocks the signal transduction pathways implicated in cancer cell growth and survival. It has recently been approved for the treatment of advanced/refractory NSCLC. This review presents the tolerability data from phase I and II gefitinib monotherapy trials, along with data from the worldwide 'Expanded Access Programme' and post-marketing use of gefitinib. Gefitinib was found to be generally well tolerated at the approved dosage of 250 mg/day; the most commonly reported adverse drug reactions (ADRs) were mild to moderate skin rash and diarrhoea, which were manageable and non-cumulative. Other ADRs observed with the use of gefitinib included: dry skin, pruritus, acne, nausea, vomiting, anorexia, asthenia and asymptomatic elevations in liver transaminase levels. Well recognised adverse effects seen with cytotoxic chemotherapy (such as bone marrow depression, neurotoxicity and nephrotoxicity) were not observed. Although the frequency and severity of ADRs increased with the dosage across the range studied (50-1000 mg/day), few patients required dosage reductions or the withdrawal of treatment, and those who did usually received gefitinib >or=600 mg/day.Thus, the available data indicate that gefitinib is well tolerated in patients with a range of solid tumours, including locally advanced or metastatic NSCLC.

Development of the novel biologically targeted anticancer agent gefitinib: determining the optimum dose for clinical efficacy

The emergence of novel, biologically targeted anticancer agents such as gefitinib ('Iressa', ZD1839) has raised the question of how the dose for later-stage clinical development and clinical use is best determined. For cytotoxic drugs, because toxic effects and antitumor activity often fall within the same dose range and are dose dependent, the clinically used dose will depend on the therapeutic window. Therefore, the maximum tolerated dose identified in Phase I trials is typically used to determine the dose level for Phase II and III trials. However, because biologically targeted agents are expected to provide clinical benefits that are not predicted by surrogate end points of toxicity to normal replicating tissue, new Phase I trials have been designed to determine the optimum biological dose for use in further studies. A large, multifaceted Phase I program was designed to evaluate the pharmacokinetics, safety, efficacy, and targeted biological activity of a once-daily oral dose of gefitinib. The maximum tolerated dose was >or=700 mg/day, although doses as low as 150 mg/day provided (a). plasma concentrations sufficient for pharmacological activity, (b). evidence of targeted biological effect, and (c). antitumor activity. From these observations, two large Phase II trials ('Iressa' Dose Evaluation in Advanced Lung Cancer 1 and 2) evaluated 250- and 500-mg/day doses of gefitinib in patients with advanced non-small cell lung cancer (NSCLC). As predicted from the Phase I trials, doses >250 mg/day provided no additional efficacy benefit, whereas adverse effects increased in a dose-dependent manner. Consequently, the recommended dose of gefitinib in NSCLC is 250 mg/day. The early clinical trial development of gefitinib provides a model for the development of novel, noncytotoxic anticancer agents.

Spotlight on Gefitinib in Non-Small-Cell Lung Cancer1

Gefitinib (Iressa), the first commercially available epidermal growth factor receptor-tyrosine kinase (EGFR-TK) inhibitor, is indicated in the management of patients with locally advanced or metastatic non-small-cell lung cancer (NSCLC). However, approved uses differ between countries; in most markets, gefitinib is approved for third-line use only (e.g. the US, Canada and Switzerland), although in some it is approved for both second- and third-line use (e.g. Japan and Australia) and, additionally, in patients considered unsuitable for chemotherapy (e.g. Indonesia and the Philippines). Few third-line treatment options exist for patients with inoperable advanced NSCLC who have failed both docetaxel and platinum-based chemotherapy regimens. Gefitinib represents a significant advance in the treatment of this population; a once-daily oral dosage of 250 mg/day was well tolerated, produced objective tumour responses and disease stabilization, and improved disease-related symptoms and quality of life. It also produced overall survival outcomes that compared favorably with historical outcomes in a similar group of patients treated with three or four different chemotherapy regimens. These findings have been supported by observations from a global compassionate-use program. Ongoing or planned clinical trials are designed to confirm and/or further define the role of the drug in the above and other clinical settings. Preliminary data demonstrate the presence of activating mutations in EGFR-TK among patients whose disease was highly responsive to treatment with gefitinib, although such mutations have not been correlated to all patients who benefit from the drug. Further studies are needed to fully elucidate the clinical implications of EGFR mutations and to identify patients likely to benefit from EGFR-targeted therapy.

Tolerability of gefitinib in patients receiving treatment in everyday clinical practice

Gefitinib ("Iressa", ZD1839), an epidermal growth factor receptor tyrosine kinase inhibitor, has recently been approved in several countries for use in advanced or metastatic non-small-cell lung cancer (NSCLC). In contrast to chemotherapies, which are generally used at or near their maximum-tolerated dose (MTD), gefitinib is used at an optimal biological dose (250 mg day(-1)), which is substantially below its MTD, minimising the risk of adverse events without compromising efficacy. Tolerability data from the compassionate use of gefitinib in the "Iressa" Expanded Access Programme support the favourable safety profile of the agent reported in Phase I and II trials. In both settings, the majority of adverse drug reactions were mild/moderate and consisted mainly of grade 1/2 diarrhoea and skin rash. Although skin rash has been suggested to predict response to gefitinib, available data do not support this hypothesis. Overall, these tolerability data demonstrate that gefitinib has a relatively benign side-effect profile and is a well-tolerated treatment option for patients with previously treated NCSLC, who currently have few alternatives.