Gilead Sciences has presented a mixed set of late-stage data on its investigational antihypertensive darusentan.

The data from the 379-patient DAR-311 Phase III trial, which was unveiled at the American Society of Hypertension meeting in San Francisco, show that darusentan significantly reduced blood pressure in patients with resistant hypertension, compared with placebo. Also more than half the darusentan-treated patients achieved their stated blood-pressure reduction goal compared to one-quarter of the patients on placebo.

However Gilead also noted that five patients treated with darusentan reported cardiovascular events. Specifically, two of them suffered myocardial infarctions, while three others experienced episodes of heart failure, though the latter group “responded rapidly to diuretic therapy”. In the placebo arm of the study, one patient suffered a fatal heart attack.

Gilead noted that the two heart-attack patients had a prior history of coronary artery disease and one of the heart failure cases was recurrent. Michael Weber, professor of medicine at the SUNY Downstate Medical College of Medicine in New York and lead study author, said these data are important “because they showed meaningful reductions in blood pressure when darusentan was added to existing antihypertensive regimens in a very difficult-to-treat patient population”.

Prof Weber told TheStreet.com that darusentan is “a very beneficial intervention that is reducing, not adding to, the risk of cardiovascular events". As the two patients who suffered non-fatal heart attacks had existing heart disease, the outcome was not surprising, he added, and the patient who had heart failure entering the study should not have been allowed to enroll.

Analysts are concerned, however, and Michael Aberman at Credit Suisse issued a note saying that “we are not certain how these cases of heart failure impact will impact the regulatory and commercial outlook for darusentan”. He believes the drug will be approved for resistant hypertension, but “the commercial potential is limited given its side effect profile and the genericised market”.