German generic drugmaker Stada reported better than expected quarterly adjusted earnings as it eked an increase in revenues from the embattled market for bulk purchase agreements with German medical insurers.

The beat gives management firepower against an activist investor seeking to replace Stada's chairman and four other supervisory board members at a shareholder meeting on June 9.

Stada will likely face questions about Active Ownership's investment and speculation that the investor could force a sale or break-up of the company in conference calls later on Thursday.

The speculation has driven the share price higher, but a source told Reuters earlier this month the shareholder has no plans to push for a sale.

Adjusted net income was up 6 percent at 40 million euros ($46 million) in the first quarter, Stada said on Thursday, compared with average analyst expectations for 37 million euros in a Reuters poll.

Stada said profits were driven by the generic drugs business in Germany, where sales rose 8 percent to 76 million euros.

Stada, which also makes branded non-prescription treatments and diagnostic kits, said it was still forecasting a slight gain for 2016 in adjusted earnings before interest, taxes, depreciation and amortization (EBITDA) and adjusted net income.

Shares in Stada were up 0.8 percent at 0830 GMT, outperforming a 0.5 percent weaker MDAX.

(Reporting by Ludwig Burger and Victoria Bryan; Editing by Georgina Prodhan and Maria Sheahan)