Pfizer drug's pancreatic benefit is unclear: FDA

WASHINGTON (Reuters) - Regulators questioned data from Pfizer Inc and Novartis AG on two potential therapies for a rare form of pancreatic cancer with limited treatment options, documents showed on Friday.

The companies are seeking approval to promote already approved cancer medicines for treating advanced pancreatic neuroendocrine tumors, an uncommon type of cancer that has afflicted Apple Inc Chief Executive Steve Jobs.

Food and Drug Administration staff, in a preliminary analysis, said Pfizer's decision to end a study of the drug Sutent early may have led to an overestimation of its effectiveness.

Agency reviewers also raised issues with Novartis' findings on the benefits of its drug, Afinitor. The company said it had narrowed the drug's proposed uses in response to FDA feedback.

Pfizer's Sutent study was terminated well before a scheduled interim analysis that required 130 events of patients living without their disease progressing, FDA reviewers said.

The trial showed early evidence of improved progression-free survival at the time it was stopped but did not meet a pre-specified efficacy goal, the FDA said. Progression-free survival is the time a patient lives without the cancer getting worse.

Stopping trials prematurely for efficacy can sometimes result in an overestimation of the magnitude of the observed treatment effect, the agency said.

Sutent's benefit in pancreatic cancer looks uncertain, the FDA staff said, when considering the possible overestimation of progression-free survival with the drug, as well as the fact that no significant improvement in overall survival was seen and there was an increased frequency of common side effects.

Pfizer has been trying to expand the uses of Sutent, which is currently approved to treat advanced kidney cancer and gastrointestinal stromal tumors.

The drug, also known as sunitinib, failed in breast and prostate cancer and faced a setback in liver cancer last year.

However, it is already a big seller, with worldwide sales of $1.07 billion in 2010.

Pfizer said the Sutent study was stopped early based on a recommendation from an independent data monitoring committee. The recommendation was based on prolonged progression-free survival reported in patients getting Sutent compared with a higher number of deaths and serious adverse events in those getting a placebo, the company said.

An FDA advisory panel is set to meet Tuesday to review data on Sutent and the Novartis drug. The FDA usually follows panel recommendations.

Since the drugs already are on the market, doctors are free to prescribe them for pancreatic cancers. But the manufacturers need FDA approval to promote the medicines for that use.

Pancreatic neuroendocrine tumors are rare and usually slower growing than other pancreatic cancers that kill within months after diagnosis. Both types have few treatment options.

With Afinitor, one study of pancreatic neuroendocrine tumors showed the drug extended the time before cancer worsened. A separate study of patients with similar tumors that occur at other sites beyond the pancreas missed its pre-defined statistical test for showing benefit.

Topics for panel discussion include "the inability of these two trials, in similar tumor types, to support each other," FDA reviewers said.

Novartis said in a statement it was amending its application on Afinitor to seek approval only for advanced pancreatic neuroendocrine tumors "based on feedback from the FDA." The company originally was asking for clearance for other neuroendocrine tumors as well.

Global Afinitor sales are expected to reach nearly $1.3 billion annually in 2015, according to a Thomson Reuters consensus forecast.

Pfizer shares rose 0.6 percent to $20.48 and Novartis shares were flat at $55.60, both on the New York Stock Exchange.

(Reporting by Esha Dey and Lisa Richwine; Editing by Steve Orlofsky and John Wallace)