(Bloomberg) -- Shionogi & Co. slumped the most in more than a decade after the drugmaker said animal studies showed its experimental Covid drug disturbed fetal development. 

The stock fell as much as 15% in early Tokyo trading Wednesday, the biggest intraday decline since March 2011. The stock had been down 8.4% this year until yesterday.

The drug will not likely be recommended for pregnant women, Kyodo News reported Tuesday without attribution. Shionogi’s experimental antiviral pill has been in a regulatory review process since February. 

The drug has the potential to generate $2 billion in annual sales, Shionogi Chief Executive Officer Isao Teshirogi said in October. The company partnered with the AIDS Clinical Trial Group in March to run studies needed to get U.S. approval.

Read more: Covid Pill Sales Could Hit $2 Billion, Japan’s Shionogi Says

Shionogi previously said it would have enough medicine for 1 million people by end of March. It plans to eventually produce sufficient supplies for 10 million people every year. Japan’s government agreed to buy 1 million courses of the antiviral drug immediately after approval in March.

©2022 Bloomberg L.P.