Biotech drug sales in the US have increased an average of 20% over the last five years and reached a total of $39.92 billion in 2006. Growth factors, primarily erythropoietins and colony-stimulating factors, represented 35.4% of the market in 2006. Monoclonal antibodies, mostly for oncology, and autoimmune and inflammation disorders, made up 28.5% of the market. Hormones are the third highest-selling biotech drugs, accounting for 13.5% of sales in 2006. Within the hormone category, insulins made up 72% of sales and human growth hormones made up 15%. Cytokines, driven by sales of interferons, made up 8.6% of sales in the biotech drug industry despite an average sales growth rate of 7% over the last two years. The biotech drug industry has benefited in general from high prices, but the recent refusal of a number of health insurance organizations to pay for new biotech drugs and the development of biogenerics are likely to bring about a change in pricing strategy. Source: Nature Biotechnology