He notes that many companies went after IGF-1 just because of its similarity to EGFR.
All three drugs target the epidermal growth factor receptor (EGFR), a protein that is over-expressed in cancer cells.
Patients who had the EGFR mutations saw the risk of their tumors growing cut in half compared with chemotherapy.
With the EGFR drugs, however, studies have not shown conclusively that it makes any difference whether EGFR is present.
It was hoped that by hitting EGFR, the out-of-control cell division that marks cancer cells could be stopped--making chemotherapy more effective.
The next step was to conduct a study in Japanese patients where genetic samples were taken from their tumors to look for EGFR mutations.
For example, lung patients with the bad EGFR mutation might be able to use the drug after surgery to prevent a reoccurrence of the disease.
The molecule - epidermal growth factor receptor (EGFR) - relays instructions to cells to grow and divide, and to ignore signals telling them to die.
Overall, the researchers identified gene mutations in 13 of the 14 responders, while no EGFR mutations were found in the 11 patients whose tumors progressed on the drug.
Such variability could be due to environmental factors, but Dr Gibson suspected it might actually be due to minor variations in the healthy copy of the Egfr gene.
Some rivals argue AstraZeneca should have done a better job narrowing the field of trial patients by first testing tumors for EGFR levels and admitting only those with elevated levels of the protein.
Working independently, Meyerson's team at Dana-Farber and a group of researchers at Massachusetts General Hospital led by cancer geneticist Daniel Haber analyzed tumor samples from lung cancer patients who'd taken Iressa, and searched for mutations in the EGFR gene.
In May 2004, Daniel Haber and Thomas Lynch, both of the Massachusetts General Hospital in Boston, published a paper in The New England Journal of Medicine showing that the tumors of eight of nine patients who had responded to Iressa had mutations in the genes for the EGFR protein.
That caused investors to lose faith in the entire class: Shares in OSI Pharmaceuticals (nasdaq: OSIP - news - people ), which is developing a third EGFR inhibitor called Tarceva with Genentech (nyse: DNA - news - people ), are down 55% since the AstraZeneca announcement.
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