The FTSE 100 drugmaker has been eyeing the California-based firm for around six months and is looking very closely at making a formal approach, according to sources cited by The Sunday Times.
AstraZeneca remained tight-lipped about a possible deal, but Medivation would fit the British firm's plans to boost its oncology business. Last year boss Pascal Soriot paid $4bn for a 55 per cent stake in Acerta Pharma, which is developing a blood cancer treatment.
However AstraZeneca is not the only firm that has set its sights on Medivation, which bankers say could have a price tag in excess of $10bn. Last week it emerged that Medivation had rebuffed an offer from France's Sanofi.
Gilead Sciences and Celegene are also thought to be interested, as well as Swiss healthcare company Roche.
Medivation declined to comment.
JP Morgan is reportedly advising Medivation on its takeover offers. The US bank declined to comment.