UPDATE 1-Gilead shares dip on heart drug safety concerns

* Five cardiovascular events for darusentan patients

* Shares down 2 percent

LOS ANGELES, May 8 (Reuters) - Gilead Sciences Inc (GILD.O: Quote, Profile, Research) reported on Friday clinical data for its experimental blood pressure drug that raised concerns about cardiovascular safety, sending the company's shares down as much as 3.8 percent.

The biotechnology company had announced last month that the drug, darusentan, met both primary goals of a late-stage study of patients whose high blood pressure is not controlled by other medicines.

Details of the study were released on Friday at a meeting of the American Society of Hypertension in San Francisco.

Darusentan was shown to be significantly more effective than placebo at all three doses tested in a 379-patient trial, but there were five cardiovascular events in patients treated with the Gilead drug: two heart attacks and three cases of heart failure.

One cardiac-related death occurred in a patient receiving a placebo.

The company said the two heart-attack patients had a prior history of coronary artery disease and one of the heart failure cases was recurrent.

"The goal of treating refractory hypertension is to prevent cardiovascular events ... When a drug for this indication is actually associated with an increased risk of cardiovascular events (potentially due to fluid retention), we do not see how the FDA (U.S. Food and Drug Administration) can approve it," FTN Equity Capital Markets analyst Joshua Schwimmer said in a research note.