FRANKFURT, July 4 (Reuters) - German generic drugmaker Stada said on Tuesday both its chief executive and its finance chief had resigned from their posts with immediate effect, ahead of a possible fresh takeover bid by buyout groups Bain Capital and Cinven.

Chief Executive Matthias Wiedenfels will be replaced by former Boehringer Ingelheim board member Engelbert Tjeenk Willink and CFO Helmut Kraft by Bernhard Duettmann, formerly finance chief at Beiersdorf and then Lanxess .

Both managers are appointed until the end of 2017, Stada said in a statement. (Reporting by Maria Sheahan; Editing by Victoria Bryan)