Gefitinib (Iressa™, ZD1839) and tyrosine kinase inhibitors -: The wave of the future in cancer therapy

Targeted therapies are one of the latest innovative trends in cancer therapy. The epidermal growth factor receptor (EGFR) is a target found in high concentrations in several solid tumors including lung, breast, colorectal, and brain. Tyrosine kinase inhibitors, such as gefitinib (Iressa (TM), ZD1 839), block the EGFR. As a result, there is inhibition of cellular proliferation, promotion of apoptosis, and inhibition of anti-angiogenesis. Gefitinib has demonstrated significant efficacy in non-small-cell lung cancer (NSCLC) leading to FDA approval for treatment of this refractory disease. Phase 2 trials with gefitinib for platinum refractory NSCLC reported disease response and symptom improvement. Early results of phase 2 studies of gefitinib, combined with standard chemotherapy in colorectal cancer, showed a 75% response rate compared with 55% with standard therapy alone. Gefitinib, combined with flutamide, produced an additive growth inhibition in prostate cancer. A phase 2 trial of gefitinib in first-relapse glioblastoma multiforme demonstrated median overall survival from treatment start of 39.4 weeks compared with 40 weeks with standard chemotherapy. Gefitinib is an oral agent with a mild toxicity profile, and thus, may be an optimal addition to chemotherapeutic regimens for some solid tumors. Gefitinib is potentially a vital and useful weapon in the arsenal of cancer therapies.