It is believed that pharmaceutical companies such as Pfizer Inc and Novartis AG might be planning to bid for Onyx Pharmaceuticals.

Onyx Pharmaceuticals might ensure a strong revenue stream through tis cancer drugs. Onyx focuses on biotechnology and has a market value of around $9.5 billion. The company management has decided to offer the stake following expression of interests from some companies, whose names were not disclosed.

The company had recently thrown out a $8.7 billion offer from larger biotech Amgen claiming that the value of the deal was too low. Amgen was offering $120-per-share offer in June as its first bid and the company had not indicated if it would increase the bid, but people closer to the matter believe that the company will participate in the auction process for Onyx.

Pfizer pays Onyx royalties on a promising experimental breast cancer drug, and Novartis has strong franchise of cancer medicines. Both the firms are interested in acquiring the biotechnology firm, according to the closer to the matter.

The shares of the company are now trading at around $86.82. Its shares rose 51.3 per cent to close at $131.33 on Nasdaq on Monday.