Gilead Sciences is an American biotechnology company which discovers, develops and commercializes therapeutics. For many years since the company was founded, the company concentrated primarily on antiviral drugs to treat patients infected with HIV, hepatitis B, or influenza. In 1990, Gilead entered into a collaborative research agreement with Glaxo for the research and development of genetic code blockers, also known as antisense. This collaboration was terminated in 1998, and Gilead's antisense intellectual property portfolio was sold to Isis Pharmaceuticals. The company's primary therapeutic focus in antiviral medicines, a field that interested Riordan because he contracted dengue fever, an untreatable viral disease, while working in malnutrition clinics as a Henry Luce Scholar in the Philippines. Gilead acquired two companies that were developing drugs to treat patients with pulmonary diseases. In 2006, Gilead completed two acquisitions that allowed the company to branch out from its historical antiviral franchise into the cardiovascular and respiratory therapeutic arenas. In 2009 the company received the award for one of the Fastest Growing Companies by Fortune. In the same year they were also named as one America's Top Companies to work for by Forbes.