AstraZeneca's Iressa Works, but Will It Satistfy the FDA?

AstraZeneca's (AZN Quote) experimental drug, Iressa, has proven effective in shrinking tumors in 10% of patients with advanced lung cancer, according to test results released Saturday at the annual meeting of the American Society of Clinical Oncology.

Iressa is the first of a new class of targeted cancer drugs, and is currently under review by the Food and Drug Administration. A decision on its approvability is expected in the second half of the year. AstraZeneca is asking the FDA to base its decision on the test results released Saturday, coupled with data from a similar clinical trial concluded late last year.

The drug has performed well in these clinical trials, but some observers worry that AstraZeneca still hasn't done enough to satisfy increasingly conservative U.S. drug regulators, which could force a delay. ...