Drugmaker Wyeth tried to discredit a Food and Drug Administration scientist who linked the company's withdrawn heartworm treatment to the deaths of hundreds of dogs, a U.S. Republican senator charged on Thursday.

Senate Finance Committee Chairman Charles Grassley said the FDA employee, Victoria Hampshire, approached his staff "because she was scared and felt unfairly targeted by Wyeth and her agency for simply doing her job."

Wyeth staff met with then-FDA Commissioner Lester Crawford a year ago and alleged that Hampshire had "personal and financial conflicts of interest" related to her review of the heartworm drug Proheart 6, Grassley said in a Senate floor speech.

The Iowa Republican said Wyeth "succeeded in having Dr. Hampshire removed from reviewing its drug."

The FDA launched a criminal investigation of Hampshire but took no action and eventually rewarded her for her work on the drug, Grassley said, adding that agency staff had briefed his committee on the matter.

A Wyeth spokesman had no immediate comment, and an FDA spokeswoman did not immediately respond to a request for a response to Grassley's charges.

Hampshire did not reply to an e-mail asking for comment, and she could not be reached by phone.

Grassley said he sent Wyeth a letter on Thursday asking the company for information and documents related to its investigation of Hampshire and comments by a Wyeth salesperson who "attempted to discredit Dr. Hampshire in the veterinary community."

Wyeth voluntarily pulled Proheart 6 from the U.S. market in September 2004, after thousands of reports of serious side effects, and the death of 600 dogs.

Grassley has been a vocal critic of the FDA and its relationship with the pharmaceutical industry. His committee has investigated the agency's oversight of several medicines, including Merck & Co. Inc.'s withdrawn arthritis pill Vioxx.

He said the Wyeth case is another example of a company "that appears too cozy with the FDA."