Activist investor Elliott has built an 8.7 percent stake in Stada, the generic drugmaker which has backed a takeover offer from buyout groups Bain and Cinven said on Wednesday.
Elliott declined to comment its intentions.
According to people close to the matter the investor has not yet signaled to Bain and Cinven whether it will tender its shares.
The private equity firms announced a sweetened bid on Monday, after their prior offer fell through.
Stada said that Elliott founder Paul Singer had 6.71 percent of Stada plus 1.98 percent in options as of July 4.