Protein-based drugs are big business, worth more than $17 billion a year. Genetically engineered bacteria and yeast efficiently churn out many protein pharmaceuticals, but as the proteins get more complex, the simple microbes sometimes fail. Drugmakers must then turn to increasingly expensive systems to make the proteins, which drives prices through the roof. Pittsboro, NC-based Biolex may have found an alternative: genetically engineer duckweed, a flowering pond plant, to secrete human proteins. The tiny plants grow very rapidly in a simple nutrient solution-doubling in population every 36 hours-and contain exceptionally large amounts of proteins. Biolex has proved the plants can do the work by using them to make complex therapeutic proteins such as interferons, which are used to treat some forms of cancer and hepatitis. The company is tweaking the system to increase efficiency and says that duckweed-produced drugs could be ready for testing in two to four years.