"GILD +4% today because ABBV expects 2018 HCV stability in pricing (in all geographies) and near-stability in US HCV patient volume."
Might be reason (more than 5% EOD), but others are possible, including (1) Wells Fargo report indicating GILD likely to beat on HCV and HIV revenue, (2) overall strength of market (BIIB up >10%), or (my favorite) (3) ABBV estimated tax rate for '18 of <10% which should be true for GILD (and others). Again, it is likely that all the reasons are part of it, though HCV issues still do seem to drive GILD share price. One of the reasons that I will not be buying short term calls before GILD earnings, when it is likely that there will be very low '18 HCV sales guidance.