On 13 July, 2015 the US Food and Drug Administration (FDA) approved gefitinib (Iressa) for the first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumours harbor specific types of epidermal growth factor receptor (EGFR) gene mutations, as detected by an FDA-approved test.
Lung cancer is the leading cause of cancer-related death among men and women in the US and, though more common in men, the number of deaths from lung cancer in women is increasing. NSCLC is the most common type of lung cancer. Mutations in the EGFR gene are present in about 10% of NSCLC tumours.
Iressa is a kinase inhibitor that blocks proteins that promote the development of cancerous cells with certain EGFR mutations. It is intended for the treatment of patients whose tumours express the most common types of EGFR mutations in NSCLC (exon 19 deletions or exon 21 L858R substitution gene mutations). The therascreen EGFR RGQ PCR Kit was approved as a companion diagnostic test to identify patients with tumours having the EGFR gene mutations in order to determine which patients would be appropriate for treatment with Iressa.
“Iressa offers another effective first-line therapy option for selected lung cancer patients. This approval provides further support for a highly targeted approach to treating cancer,” said Dr Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research.
Orphan product designation for the treatment of EGFR mutation-positive metastatic NSCLC
The FDA granted Iressa orphan product designation for the treatment of EGFR mutation-positive metastatic NSCLC. Orphan product designation is given to drugs intended to treat rare diseases, which provides financial incentives – like tax credits, user fee waivers, and eligibility for market exclusivity – to promote their development.
“The approval of the therascreen EGFR RGQ PCR Kit will allow physicians to identify non-small cell lung cancer patients who are candidates for receiving Iressa as first-line therapy,” said Alberto Gutierrez, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health. “Companion diagnostics provide information that is essential for the safe and effective use of important medications.”
Efficacy and safety
The efficacy and safety of Iressa for this use was demonstrated in a multi-center, single-arm clinical trial of 106 patients with previously untreated, EGFR mutation-positive metastatic NSCLC. The study’s primary endpoint was objective response rate, or the percentage of patients who experienced complete and partial shrinkage or disappearance of the tumours after treatment. Participants received Iressa 250 mg once daily. Results showed that tumours shrank in about 50% of patients after treatment and this effect lasted an average of six months. The response rates were similar in patients whether their tumours had EGFR exon 19 deletions or exon 21 L858R substitution mutations.
These results were supported by a retrospective analysis of another clinical trial, which identified a subgroup of 186 patients with EGFR mutation-positive metastatic NSCLC receiving first-line treatment. Patients were randomised to receive Iressa or up to six cycles of carboplatin/paclitaxel. The results from this subgroup suggested an improvement in progression-free survival with Iressa compared to carboplatin/paclitaxel.
Iressa may cause serious side effects including interstitial lung disease, liver damage, gastrointestinal perforation, severe diarrhoea and ocular disorders. The most common side effects of Iressa are diarrhoea and skin reactions (including rash, acne, dry skin and pruritus, or itching).
History of gefitinib’s approval for NSCLC
Iressa originally received accelerated approval in 2003 for the treatment of patients with advanced NSCLC after progression on platinum doublet chemotherapy and docetaxel. Iressa was voluntarily withdrawn from the market after subsequent confirmatory trials failed to verify clinical benefit. This current approval is for a different patient population (EGFR mutation-positive, previously untreated) than the 2003 approval.
Iressa is marketed by Wilmington, Delaware-based AstraZeneca Pharmaceuticals. The therascreen EGR RGQ PCR Kit is manufactured by QIAGEN Manchester Ltd., based in the United Kingdom.