Regeneron Pharmaceuticals Inc said U.S. health regulators extended the review of its experimental eye drug by three months, sending its shares down 6 percent in extended trade.

Regeneron said the U.S. Food and Drug Administration extended the review date to November 18 as it needed more time to review the recently submitted data by the company.

Regeneron had submitted new data to address FDA's questions about the chemistry, manufacturing, and controls section of the marketing application.

In June, the FDA advisory panel unanimously recommended the approval of the drug Eylea as a treatment for the most serious form of macular degeneration.

The FDA usually follows the advice of its advisory panels.

Regeneron is developing the drug along with Bayer AG.

Shares of Regeneron were down 6 percent at $53.96 in after-market trade. They closed at $57.42 on Tuesday on Nasdaq.