Pfizer Inc. has been asked to go back to the drawing board on its application for a drug to treat a rare neurodegenerative disease commonly known at TTR-FAP.

Pfizer said after markets closed Monday that the U.S. Food and Drug Administration had asked the pharmaceutical company, which is based in New York City but has its largest worldwide research contingent in Groton, to complete a new study to “establish substantial evidence of effectiveness” before the agency would give its stamp of approval for the drug, called tafamidis meglumine.

The agency also asked for additional information about data the company already submitted regarding the drug’s effect on Transthyretin Familial Amyloid Polyneuropathy, Pfizer said.

“It is our intention to request a meeting as soon as possible with the agency in order to discuss a potential path forward,” said Yvonne Greenstreet, a Pfizer senior vice president and head of the company’s Medicines Development Group, in a statement.

The FDA’s decision came as something of a surprise, since it earlier had approved the experimental pill for a priority review because tafamidis offered some hope for a disease that otherwise gave patients few options for treatment. Tafamidis, in early experiments, showed promise of delaying neurological impairment.

Pfizer pointed out that the European Commission late last year approved tafamidis for adults in the early stage of treatment for TTR-FAP. Only about 8,000 people worldwide are affected by the disease, which is progressive and inevitably fatal.

Pfizer acquired tafamidis last year with the purchase of Massachusetts research company FoldRx Pharmaceuticals Inc.

“TTR-FAP is a relentless and debilitating disease,” Greenstreet said. “We understand the urgent need within the patient community and stand firmly behind this innovative medicine.”

l.howard@theday.com