Updated from 7:04 a.m. EDTGilead Sciences ( GILD) reported results Thursday from a phase III study showing its experimental drug darusentan successfully treated patients with high blood pressure that was not controlled by other medicines. Investors reacted well to the initial look at the darusentan results, pushing Gilead shares higher almost 6% to $47.30 in Thursday's after-market trading session. Shares were rising 3.9% to $46.42 Friday afternoon. The Foster City, Calif.-based company is best known for its market-leading HIV drug franchise, but more recently Gilead has sought to diversify into other disease areas, including cardiovascular disease. Investors have been somewhat wary of this effort, so they were waiting for results from this first phase III study of darusentan to assess the new push outside of HIV. That includes Gilead's decision last month to acquire CV Therapeutics ( CVTX) and its chronic angina drug for $1 billion. Darusentan, a once a day pill, is being developed as a treatment for resistant hypertension, defined as high blood pressure that is not alleviated by treatment with a stable of other drugs. The number of Americans currently diagnosed with resistant hypertension ranges widely from 2 million to 5 million, and analysts believe darusentan, if approved, could generate sales for Gilead in the range of $500 million to $1 billion. In the phase III study announced by Gilead, all three doses of darusentan tested were able to reduce systolic and diastolic blood pressure compared to placebo after 14 weeks of treatment. The results were statistically significant, achieving the co-primary endpoints of the study. Moreover, more than half the darusentan-treated patients achieved their stated blood-pressure reduction goal compared to one-quarter of patients treated with a placebo, Gilead said.