The Food and Drug Administration (FDA) has approved Iressa (geftinib; AstraZeneca) tablets as first-line treatment for patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations as detected by an FDA-approved test. The FDA has concurrently approved the labeling expansion for the companion diagnostic test therascreen EGFR RGQ PCR Kit for patient selection.

The approval of Iressa was based on the results of a multicenter, single-arm, open-label clinical study (n=106) of treatment naive patients with metastatic EGFR mutation positive NSCLC who received Iressa 250mg daily until disease progression or intolerable toxicity. The study’s major efficacy outcome was objective response rate (ORR) according to RECIST v1.1 as evaluated by both a Blinded Independent Central Review (BICR) and investigators.

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Study results showed that the BICR ORR was 50% (95% CI: 41, 59) with a median duration of response of 6.0 months. The investigator-determined ORR was 70% (95% CI: 61, 78) with a median duration of response of 8.3 months.

Iressa is a tyrosine kinase inhibitor that reversibly inhibits the kinase activity of wild-type and certain activating mutations of EGFR, preventing autophosphorylation of tyrosine residues associated with the receptor, thereby inhibiting further downstream signaling and blocking EGFR-dependent proliferation.

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 Iressa was voluntarily withdrawn from the market after subsequent confirmatory trials failed to verify clinical benefit.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 will be available as 250mg strength tablets in 30-count bottles.

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