* FDA: Pfizer pancreatic drug showed uncertain benefits
* FDA staff also question Novartis cancer drug data
* Panel set to review both drugs on Tuesday
* US budget impasse could derail Tuesday meeting
* Pfizer shares up 0.6 pct, Novartis down 0.5 pct (Adds details on Pfizer drug results, possible disruption from U.S. budget dispute)
By Esha Dey and Lisa Richwine
WASHINGTON, April 8 (Reuters) - U.S. regulators questioned data from Pfizer Inc (PFE.N) and Novartis AG NOVN.VX on two potential drugs 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, a type of cancer that has afflicted Apple Inc (AAPL.O) 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. Sutent commands more than $1 billion in annual sales with approval for advanced kidney cancer and gastrointestinal stromal tumors. Its use for pancreatic cancer addresses a much smaller market.
Agency reviewers also questioned Novartis’ findings on the benefits of its drug, Afinitor, with an estimated potential for $1.3 billion in annual sales in 2015, according to a Thomson Reuters consensus forecast. The company said it narrowed the drug’s proposed uses in response to FDA feedback.
Unless derailed by a looming U.S. government shutdown, an FDA advisory panel is due to meet Tuesday to decide if the issues raised by agency reviewers cast enough doubt to recommend against approval of the new use. Some experts expect the need for new therapies for an unusual cancer could offer a stronger case in favor of the medicines.
“Given the lack of other treatment options (Pfizer and Novartis) go into this panel with a stronger likelihood of approval,” Morningstar analyst Damien Conover said.
An FDA official said all advisory committee meetings will be canceled if the federal government is shut down. [ID:nN08144565]
Pancreatic neuroendocrine tumors are rare, occurring at a rate of about 0.32 cases per 100,000 people. They usually grow slower than other pancreatic cancers that kill within months of diagnosis. Both types have few treatment options.
The advisory panel will weigh data from Pfizer and Novartis before voting on whether to recommend approval of the new uses. The FDA usually follows panel recommendations and will make final rulings in the coming months.
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.
FDA reviewers said Pfizer’s Sutent study was terminated well before a scheduled interim analysis that required 130 events of patients living without their disease progressing.
The trial showed early evidence of improved progression-free survival at the time it was stopped, but did not meet a previously 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 overstate the magnitude of the observed treatment effect and, in Sutent’s case, the benefit in pancreatic cancer looks uncertain, the agency staff said.
They also cited 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, also known as sunitinib. It failed in breast and prostate cancer and faced a setback in liver cancer last year.
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.
Sutent patients lived a median period of 11.4 months without their cancer spreading versus 5.5 months with a placebo, Pfizer said.
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.
Novartis said in a statement it was amending its application on Afinitor to seek approval only for advanced pancreatic neuroendocrine tumors. The company originally was asking for clearance for other neuroendocrine tumors as well.
Pfizer shares rose 0.6 percent to close at $20.46 and Novartis shares finished down 0.5 percent at $55.30, both on the New York Stock Exchange. (Reporting by Esha Dey and Lisa Richwine; editing by Michele Gershberg, Steve Orlofsky, John Wallace and Andre Grenon)