Based upon the data here: http://investor.anacor.com/releasedetail.cfm?ReleaseID=971005
A product with a peak sales of 2B has the company sold for almost 6B, a 3x rule of thumb applied to previously accepted sales figures for RSV of 5B yields future sales price based on market cap of 15B of at least $50.
Current market cap is 2.06B, price is 7.43
Future market cap is 15B, 7.28 times current price..
7.43 x 7.28 = $54.