With a panel of experts gathering on Thursday to review AstraZeneca's ($AZN) experimental thyroid cancer drug vandetanib, FDA staffers today unveiled their concerns about the risk of high levels of toxicity faced by prospective patients. The agency highlighted that "a substantial number of patients receiving vandetanib required a dose reduction and/or interruption" during a critical trial of the therapy. Close to a third of the patients taking the drug experienced significant side effects, compared to only 13 percent of the patients taking a placebo.
Once tapped as a top potential blockbuster in the AstraZeneca pipeline, investigators have significantly narrowed their work on the drug since it failed to extend the survival rate of lung cancer victims. The therapy may need to be restricted for now to advanced, inoperable cancer cases, which analysts say could cut its peak sales to $100 million.
"Given the substantial toxicity seen with vandetanib, should its indication be limited to patients with progressive, symptomatic medullary thyroid cancer?" FDA reviewers wrote in a summary. AstraZeneca, meanwhile, is pushing for an approval based on a "manageable" side effect profile and a shot at a "compelling benefit" for patients with no other options to turn to.