Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (‘Iressa’), in combination with 5-fluorouracil (5-FU) and leucovorin (LV), in advanced colorectal cancer (ACRC)

Epidermal growth factor receptor tyrosine kinase inhibitors: present and future role in gastrointestinal cancer treatment: a review

BACKGROUND

Despite advances in conventional and targeted anticancer therapy, the prognosis remains poor for many patients with solid tumors. Ongoing research into the molecular basis of malignant disease, however, has yielded many novel agents with potential activity, including the epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs).

DESIGN

This review summarizes current clinical data for EGFR-TKIs as monotherapy or in combination with 5-fluorouracil/leucovorin, irinotecan, or oxaliplatin, focusing on the rapidly developing area of colorectal, gastroesophageal, and pancreatic cancers.

RESULTS

EGFR-TKIs have limited but valuable activity as monotherapy in non-small cell lung cancer patients who have received prior anticancer treatment. The potential for application as a single agent in colorectal, gastroesophageal, and pancreatic cancers has yet to be demonstrated conclusively and deserves further investigation, especially as second- or third-line therapy. In combination with oxaliplatin-based regimens and 5-fluorouracil/leucovorin-based regimens, TKIs have shown benefits, suggesting that there may be a synergistic effect with chemotherapy. However, combinations with irinotecan-based regimens have been limited by toxicities.

CONCLUSIONS

EGFR-TKIs show benefits when used in combination with chemotherapy, and the favorable toxicity profiles observed suggest that these may be of value in frail or elderly patients.

Novel therapeutics in colorectal cancer

Colorectal cancer is an excellent tumor model for evaluating novel therapeutic strategies. Development of a mechanistic understanding of how this cancer develops, spreads, and grows allows a tailored approach to all stages of treatment: prevention, adjuvant treatment, and therapy of advanced disease. We focus on therapy in the advanced disease setting, although progress in this area could lend itself to treatment of early or premalignant disease. In the last 20 years, information has been generated about the intracellular pathways of tumor formation, invasion, and metastasis. As a result, specific molecular processes have been targeted for therapeutic intervention, including cell surface growth factor receptors, proliferation signaling, cell cycling, apo-ptosis, angiogenesis, and matrix metalloproteinases. We review the scientific rationale for recently developed novel therapeutics in colorectal cancer, and the results of clinical trials to date. We also suggest appropriate clinical settings for specific targets and outline future directions of research.

Gefitinib, a novel, orally administered agent for the treatment of cancer

Traditional cytotoxic anticancer therapies do not differentiate between tumour and host cells, and research efforts have been focused on finding new agents that target tumour tissue. Gefitinib ('Iressa', ZD1839) is an orally active epidermal growth factor receptor tyrosine kinase inhibitor that blocks signal pathways implicated in solid tumour growth and metastasis. In phase II trials, gefitinib 250 mg/day demonstrated efficacy in the control of advanced non-small-cell lung cancer (NSCLC) in patients who had undergone prior chemotherapy. Response rates were 18.4 and 11.8%, and disease control rates were 54.4 and 42.2%, at 250 mg/day in two multicentre trials - IDEAL 1 and 2. Gefitinib also caused rapid relief from the symptoms of NSCLC in approximately 40% of patients, while displaying a generally good tolerability profile that most commonly included mild, reversible gastrointestinal and skin adverse events. Gefitinib 250 mg/day has been approved for use in advanced, previously treated NSCLC in several countries including the USA, Japan and Australia. As a monotherapy and combination therapy, it is being investigated for the treatment of several common tumour types in addition to NSCLC. The pharmacokinetics of gefitinib have shown it to be suitable for once daily dosing, with a terminal half-life of approximately 48 h in patients with cancer. Steady-state exposure is achieved after 10 days dosing, and exposure is dose proportional up to 250 mg/day. Gefitinib is cleared principally by the biliary route and in part by metabolism. This review summarizes relevant data from studies of gefitinib that inform its clinical administration.

Pharmacokinetic Evaluation of Gefitinib When Administered with Chemotherapy

Gefitinib is a small-molecule agent specifically targeted to inhibit the epidermal growth factor receptor-tyrosine kinase (EGFR-TK). Tumor responses have been achieved with gefitinib treatment in large, randomized monotherapy trials. In preclinical studies, gefitinib has shown additive and even supra-additive antitumor effects when combined with different cytotoxic agents. In phase I clinical trials, gefitinib was found to be well tolerated, with clinical efficacy observed well below the maximum tolerated dose. The pharmacokinetics of gefitinib allow it to be administered as a once-daily oral tablet. Several phase I studies have investigated the safety of gefitinib at daily doses of 250 mg or 500 mg in combination with chemotherapy agents for first-line treatment of a variety of common solid tumors. The potential for drug interactions between gefitinib and cytotoxic agents was evaluated through pharmacokinetic assessments. A randomized, crossover study investigated the interaction of gefitinib and carboplatin/paclitaxel in the treatment of advanced non-small-cell lung cancer (NSCLC). A second trial with an open-label design studied the combination of gefitinib with cisplatin/gemcitabine in patients with a variety of solid tumors, including NSCLC. In both pilot studies, the addition of gefitinib to chemotherapy did not increase the exposure of any of the chemotherapy agents tested. However, increased exposure to gefitinib was seen with the carboplatin/paclitaxel regimen. The addition of gefitinib to these chemotherapy regimens was generally well tolerated, and there was no apparent increase in higher-grade toxicity. Additional trials are evaluating gefitinib treatment in combination with chemotherapy.

ZD1839 (Iressa): for more than just non-small cell lung cancer

ZD1839 (Iressa) is an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor that blocks signal transduction pathways involved in cell proliferation. Preclinical studies demonstrated that ZD1839 is a promising agent for the treatment of a wide range of tumors and has additive-to-synergistic effects when combined with radiation or chemotherapy in various cell lines and xenografts. Phase I clinical trials have reported that ZD1839 has acceptable tolerability and antitumor activity. In addition to non-small cell lung cancer, phase II/III studies are currently investigating ZD1839 as monotherapy or in combination therapy against prostate, breast, head and neck, gastric, and colorectal tumors.