Gilead Sciences' Phase III Darusentan Data Show Significant Blood Pressure Reductions In Resistant Hypertension Patients

Main Category: Hypertension
Article Date: 11 May 2009 - 4:00 PDT

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Gilead Sciences, Inc. (Nasdaq:GILD) announced the presentation of data from DAR-311 (DORADO), a Phase III clinical trial evaluating the company's once-daily oral endothelin receptor antagonist (ERA) darusentan as an add-on treatment for resistant hypertension, defined as the failure to achieve goal blood pressure while adhering to full doses of an appropriate three-drug regimen that includes a diuretic. The data are being presented during an oral late-breaker session at the American Society of Hypertension, Inc. (ASH) Twenty-Fourth Annual Scientific Meeting and Exposition (ASH 2009) in San Francisco (Presentation #LB-OR-06).

DAR-311 is an international Phase III double-blind, placebo-controlled parallel group trial, in which 379 patients were randomized to receive once-daily doses of darusentan 50 mg (n=81), 100 mg (n=81), 300 mg (n=85) or placebo (n=132) for up to 14 weeks as an add-on to existing antihypertensive regimens. The co-primary efficacy endpoints were change from baseline to week 14 in trough sitting systolic blood pressure (SBP) and trough sitting diastolic blood pressure (DBP). Secondary endpoints included change from baseline in mean 24-hour SBP and DBP and percent of patients reaching SBP goal. Gilead announced topline results from the study in April.

"Because of the increased risk of a number of life-threatening cardiovascular conditions associated with failure to control blood pressure, including stroke and heart attack, it is essential that new therapeutic approaches be evaluated for treatment of resistant hypertension," said Michael A. Weber, MD, Professor of Medicine at the SUNY Downstate Medical College of Medicine, Brooklyn, New York and lead study author. "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."

DAR-311 Results

Baseline demographic and clinical characteristics were comparable across treatment groups. The mean patient age was 62 years old with 39 percent of patients over age 65. The mean body mass index (BMI) was 32 kg/m2, an indication of obesity. Forty percent of patients were diabetic and 25 percent of patients had chronic kidney disease (CKD).

In DAR-311, mean reductions in trough sitting SBP from baseline of 16.5 mmHg, 18.1 mmHg, 18.1 mmHg and 8.6 mmHg were observed for the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively, after 14 weeks of treatment. Mean reductions in trough sitting DBP from baseline of 10.1 mmHg, 9.9 mmHg, 10.7 mmHg and 5.3 mmHg were observed for the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively, after 14 weeks of treatment (p<0.001 for comparison of each darusentan group versus placebo).

Ambulatory blood pressure monitoring (ABPM) performed at week 14 revealed highly significant (p<0.001) reductions from baseline in 24-hour SBP and DBP in patients treated with darusentan. Reductions in mean 24-hour SBP of 9.0 mmHg, 9.8 mmHg, 9.5 mmHg and 1.1 mmHg were observed for the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively. For DBP, mean 24-hour reductions of 7.8 mmHg, 7.7 mmHg, 7.4 mmHg and 0.7 mmHg were observed for the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively. Reductions in ambulatory SBP were maintained throughout the 24-hour monitoring period and there were no significant changes in heart rate.

According to guidelines, SBP of less than 140 mmHg is recommended for patients with hypertension and no other serious conditions. For patients with diabetes and CKD, target SBP is more stringent, with a goal of less than 130 mmHg. In DAR-311, more than half of patients treated with darusentan achieved goal blood pressure, as compared to approximately one quarter of patients receiving placebo (53.1 percent, 53.1 percent, 48.2 percent and 27.3 percent in the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively; p<0.001 for comparison of each darusentan group versus placebo).

The most common adverse events were peripheral edema/edema, fluid retention, dizziness, headache and fatigue. Peripheral edema/edema was reported in 20 percent, 24 percent, 15 percent and 10 percent of patients in the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively. Fluid retention was reported in 5 percent, 11 percent, 11 percent and 5 percent of patients in the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively.

Liver function test results were comparable between treatment groups, with liver enzyme (aminotransferase) concentrations above three times the upper limit of normal (ULN) range being reported in three patients, one each in the placebo, 100 mg and 300 mg darusentan groups. There were small mean decreases in hemoglobin (0.9 g/dL, 0.9 g/dL, 1.1 g/dL and 0.2 g/dL in the darusentan 50 mg, 100 mg, 300 mg and placebo groups, respectively) and total protein concentrations (0.2 g/dL in each of the darusentan groups and 0.1 g/dL in the placebo group). No changes in white blood cell or platelet counts were observed.

One cardiac-related death occurred in a patient receiving placebo. There were cardiovascular events in five patients on darusentan: two had myocardial infarction (both with prior history of coronary artery disease), one had recurrence of heart failure that was present at baseline and two had heart failure with preserved ejection fractions (measurements of heart pumping capacity; 0.58 and 0.65) that responded rapidly to diuretic therapy.

Darusentan is an investigational compound and has not yet been determined safe or efficacious in humans.

About the Phase III DORADO Program

DAR-311 is one of two ongoing Phase III clinical trials evaluating the safety, efficacy and tolerability of darusentan as an add-on treatment for resistant hypertension. The second study, DAR-312 (DORADO-AC), is fully enrolled and is expected to be completed with data available by the end of 2009.

DAR-312 is an international Phase III double-blind, placebo- and active-controlled, parallel group trial, in which approximately 770 patients were randomized to receive darusentan (titrated to the optimal dose of 50, 100 or 300 mg once daily), an active comparator (guanfacine 1 mg once daily) or placebo. The co-primary endpoints of the trial are the changes from baseline to week 14 in trough sitting SBP and trough sitting DBP, as measured by sphygmomanometry.

For both studies, patients who complete the 14-week assessment period are eligible to enroll in long-term safety studies (DAR-311E and DAR-312E).

About Darusentan

Darusentan is an oral, once-daily propanoic-acid class endothelin receptor antagonist (ERA) being investigated in clinical trials as an add-on oral therapy for patients with resistant hypertension. Darusentan selectively blocks the endothelin type-A (ETA) receptor, which if activated by endothelin-1 (ET-1), leads to vasoconstriction (narrowing of blood vessels) and cell proliferation. Elevated ET-1 blood concentrations have been reported in some patients with hypertension, including several subgroups of hypertensive patients that have been historically difficult to treat.

About Resistant Hypertension

Resistant hypertension is defined as the failure to achieve goal blood pressure in patients who are adhering to full doses of an appropriate three-drug regimen that includes a diuretic. According to the Seventh Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), an SBP of less than 140 mmHg and a DBP of less than 90 mmHg are recommended for patients with hypertension and no other serious conditions. For patients with diabetes and chronic kidney disease, target systolic and diastolic blood pressures are more stringent - an SBP goal of less than 130 mmHg and a DBP goal of less than 80 mmHg.

Hypertension affects approximately one billion people worldwide. While the exact number of patients classified as resistant is unknown, estimates suggest a prevalence of anywhere between 2 percent and 5 percent of hypertensive patients in general practice settings in the United States, with significantly higher rates in specialty referral clinics. Failure to control hypertension elevates the risk of stroke, coronary artery disease, myocardial infarction, heart failure, kidney disease and cardiovascular mortality. Currently, there is no accepted standard of care for treatment of patients with resistant hypertension.

Source
Gilead Sciences

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