Gilead Sciences Inc. posted a 34 per cent increase in fourth-quarter profit, trouncing Wall Street expectations, as sales of its blockbuster hepatitis C drugs soared in Japan and offset lower sales in the U.S. The maker of Harvoni, the first once-daily, single-pill regimen for hepatitis C, and predecessor drug Sovaldi, has been propelled by the lucrative franchise since Sovaldi was launched at the end of 2013. They're the main reason the company's revenue has tripled in just two years, a rare accomplishment in the industry.