Biotech drug sales are growing at a faster pace than prescription drugs as a whole and now represent 13 percent of U.S. sales, according to an IMS Health report released today.

Complex therapies such as Enbrel and Rituxan from biotech giants Amgen and Genentech, respectively, helped grow biotech sales to $32.8 billion in 2005, up 17 percent from 2004.

2005 prescription drug sales increased 5.4 percent to $251.8 billion.

Major pharmaceutical companies such as Wyeth expect more of their future sales to come from biotech drugs. The company's research and development head told Reuters that this category could reach 40 percent of sales within a decade, up from 25 percent currently.

Seattle's Trubion Pharmaceuticals, like many young biotech companies, has benefited from this trend. It announced a deal last month with Wyeth centering on a technology platform that could improve biotech drug development. The deal could be worth $800 million or more if certain goals are met.