Viagra-maker Pfizer is to acquire cancer drug company Medivation in a deal valued at about 14 billion US dollars (£10.6 billion).

Medivation is best known for cancer treatment Xtandi, which it jointly markets with Japanese drug maker Astellas Pharma.

Pfizer will pay 81.50 US dollars per Medivation share, which is a 21% premium on the biotech firm's closing price of 67.19 US dollars. The boards of both companies have approved the deal, which is expected to close in the third or fourth quarter.

Pfizer's Forfar-born chairman, Ian Read, said: "The proposed acquisition of Medivation is expected to immediately accelerate revenue growth and drive overall earnings growth potential for Pfizer.

"This transaction is another example of how we are effectively deploying our capital to generate attractive returns and create shareholder value."

Pfizer added that Medivation also has a promising pipeline of cancer drugs in late-stage clinical development, including the potential breast cancer treatment talazoparib and a lymphoma drug.

The deal comes last month after Medivation rejected a 9.3 billion US dollar takeover bid from the French drug maker Sanofi, saying that offer, worth 52.50 US dollars per share, undervalued the company.