Iressa set to make it at second asking

The EMEA's CHMP has issued a positive opinion supporting the approval of AstraZeneca's targeted oral anticancer drug, Iressa (gefitinib), for the treatment of non-small cell lung cancer (NSCLC). Specifically, the CHMP has recommended approval of Iressa for adults with locally-advanced or metastatic NSCLC with activating mutations of EGFr-tyrosine kinase, in all lines of therapy. However, AstraZeneca will be required to conduct a follow-up measure study to generate further data in a Caucasian NSCLC patient population. The company is in discussion with the CHMP to finalise the study design and endpoints.

The opinion was based on a submission package including two pivotal Phase III studies, IPASS (IRESSA Pan-ASia Study) and INTEREST (IRESSA Non-small-cell lung cancer Trial Evaluating REsponse and Survival against Taxotere). The IPASS trial exceeded its primary objective, demonstrating superior progression-free survival (PFS), greater objective response rate (ORR), improved tolerability and significant quality-of-life benefits for Iressa, compared to carboplatin+paclitaxel doublet chemotherapy (CT) in clinically-selected first-line patients in Asia. However, the treatment effect was not constant over time, with the probability of being progression-free in favour of carboplatin+paclitaxel in the first six months and in favour of Iressa in the following 16 months. This was likely due to the different effect of Iressa in subgroups defined by EGFr tumour mutation status. PFS was significantly longer for Iressa than doublet CT in patients with EGFr mutation-positive tumours, and significantly longer for doublet CT than Iressa in patients with EGFr mutation-negative tumours.

The INTEREST study met its primary objective, demonstrating equivalent overall survival (OS) and significant quality-of-life benefits for Iressa, compared to standard CT (docetaxel) in the pretreated setting. Preplanned subgroup analyses showed a significant improvement in PFS and ORR for Iressa over docetaxel in patients with EGFr mutation-positive tumours.

In 2005, AstraZeneca withdrew its EU marketing authorisation application for Iressa following data from the Phase III ISEL (IRESSA Survival Evaluation in Lung cancer) study in pretreated patients not eligible for further CT. ISEL did not meet its primary objective of a statistically significant improvement in OS for Iressa compared to placebo, but did confirm a number of important clinical benefits, including tumour shrinkage and a significant improvement in time-to-treatment failure. The refractory nature of the ISEL population is the most likely explanation for the magnitude of the survival improvement with Iressa, compared to placebo, not reaching statistical significance.

But what sort of a comeback will Iressa be making? Only a day after the CHMP decision, Roche announced that it is collaborating on a trial to investigate Tarceva (erlotinib) in LC patients with genetic mutations in EGFr. The results from the EURTAC trial, if positive, will support a submission by Roche to the EMEA to seek an additional new indication for use of Tarceva, putting it in direct competition with Iressa. Tarceva is already approved, and unlike Iressa, has been shown to benefit all patients, whether or not they have a mutated version of EGFr. Based on this, it looks likely that Iressa will become a niche product. However, a launched product is better for AstraZeneca than one sat on the shelf.

Matthew Dennis - Editor, Cancer Drug News