After drug pricing concerns weighed on Gilead Sciences' stock toward the end of December, the drugmaker has kicked off 2015 the same way it did the previous two years: by increasing prices on several products.

The biotech giant raised the prices of seven of its major products by as much as 9.9 percent on Jan. 1, according to research from Cowen, which suggested investor concerns over the drugmaker's pricing power "have been overblown."