Upping its commitment to gene therapy, Pfizer says it will invest $500 million in its manufacturing facility in Sanford, North Carolina. The time and cost of making the quadrillions of viruses used to deliver DNA have been major holdups for the entire gene-therapy field. Manufacturing is particularly important for Pfizer, which is focused on treating relatively common conditions like hemophilia B and muscular dystrophy. Commercialization of such therapies will require an unprecedented production scale-up. Pfizer has 650 employees in Sanford and is adding about 300 more.