German pharmaceutical firm Bayer is preparing an offer to buy its Norwegian partner Algeta , according to a German newspaper on Tuesday, in a report published by Reuters.

According to the German paper Frankfurter Rundschau, it obtained internal documents saying Bayer would offer NOK306 (USD49.9) per share of Algeta. The Norwegian company, which is listed in the stock market, was referred to in the said document as "Aviator." The newspaper believed this company is Algeta, the report said.

Algeta is Bayer's partner for its prostate cancer drug Xofigo. Both companies are co-promoting the drug in the US. Xofigo is also called Radium-223 dichloride. This drug is made for bone metastases from prostate cancer, the kind that cannot be treated by the usual hormone therapy. According to Bayer, this drug could become a "blockbuster" product with at least EUR1 billion in annual sales, the report explained.

Bayer and Algeta have yet to comment on the acquisition bid, Reuters reported.