U.S. regulators are moving quickly with Roche’s application for targeted melanoma drug vemurafenib, which could receive approval as early as this week, according to a source familiar with the situation. A pivotal trial found that advanced melanoma patients taking the experimental pill, being developed in partnership with Daiichi Sankyo, were 63 percent less likely to die from the disease than patients given chemotherapy. Vemurafenib, whose brand name is Zelboraf, is designed for patients with tumors that have a mutation in a gene known as BRAF that allows melanoma cells to grow. About half of all melanomas, the deadliest form of skin cancer, have the genetic aberration.