FRANKFURT Buyout groups Bain Capital and Cinven have so far collected 9.56 percent of Stada (STAGn.DE) shares, the German drugmaker said on Thursday.
The tender offer for the agreed 5.3 billion euro (£4.6 billion) deal runs through June 8 and is conditional on securing 75 percent of Stada's shares.
Investors typically tender shortly before the deadline.
People close to the deal have said that passing the set threshold may prove a challenge given the large number of shares held by retail investors, who are more likely to forget to tender than institutional stockholders, as well as by index tracking funds that cannot tender for technical reasons.
About 20 percent of Stada's shares are held be retail investors and about 10 percent by index trackers.
Few Stada shareholders are seen holding out for a pricier rival bid after a consortium comprising buyout groups Advent and Permira as well as Shanghai Pharmaceuticals (601607.SS) has decided to stay on the sidelines of the deal.
(Reporting by Arno Schuetze; Editing by Maria Sheahan)