I read somewhere that there is a 3 percent fee if GILD backs out of the deal. So I guess it might cost GILD about 330 million. Of course, not backing out could cost them several billion if PSI-7977 does not live up to the hype.
The November 21 Reuters article (see Vertex news headlines on Yahoo Finance on 11/21/11) states that a source said there is a "standard break-up fee" of about 3 percent of the total deal value. I agree that is highly unusual to see such a discrepancy between the acquisition price and the current price of VRUS. Maybe GILD is having second thoughts. Maybe they are wondering about why the genotype 1 Hep C patients need to be "interferon intolerant" to benefit from the PSI-7977 miracle drug.