Abstract 2115: Results of CONTROL, a Phase 2, Multicenter, Randomized, Double-blind, Placebo-controlled, Parallel Study of the Effects of Tetrahydrobiopterin on Blood Pressure in Subjects with Poorly Controlled Hypertension
BACKGROUND: Tetrahydrobiopterin (6R-BH4) is a cofactor for nitric oxide (NO) synthesis. Reduced BH4 bioavailability uncouples NO synthase, decreases NO production, increases superoxide production, and may contribute to hypertension. 6R-BH4 administration has been shown to lower blood pressure (BP) and improve endothelial function in animal models and in two small, open-label clinical studies. A randomized, placebo-controlled, multicenter, parallel study was designed (‘CONTROL’) to evaluate the antihypertensive effects of 6R-BH4 in patients with treated, but poorly controlled, hypertension.
METHODS: A total of 116 subjects with hypertension (SBP/DBP> 135/85) despite a stable regimen of at least two antihypertensive drugs were randomized 2:1 to oral 6R-BH4 (n=77) or placebo (n=39) and stratified by presence or absence of type 2 diabetes. Subjects received a daily dose of 10 mg/kg 6R-BH4 for 8 weeks. Endpoints were change from baseline in SBP and DBP over 8 weeks of treatment. Other measures of efficacy included change in insulin sensitivity, proteinuria, and biochemical markers of oxidative stress and NO production.
RESULTS: 6R-BH4-treated subjects had a 4.4-mm Hg drop in SBP (baseline mean, 145 mm Hg) compared with a 6.4-mm Hg drop in placebo-treated subjects (baseline mean, 143 mm Hg; p=0.428). 6R-BH4-treated subjects had a 5.0-mm Hg drop in DBP (baseline mean, 90 mm Hg) compared with a 4.8-mm Hg drop in placebo-treated subjects (baseline mean, 93 mm Hg; p=0.907). No statistically significant differences in either endpoint were seen in subgroup analyses of subjects with or without diabetes, or in other measures of efficacy or safety. Post-hoc analyses in subjects with higher SBP at baseline (>150 mm Hg) showed a better SBP response to 6R-BH4 (−14.1 mm Hg) than to placebo (−5.9 mm Hg) however too few subjects with higher SBP were enrolled to reach statistical significance (6R-BH4, n=19; placebo, n=7: p=0.149).
CONCLUSIONS: Oral 6R-BH4 at a dose of 10 mg/kg/day showed no anti-hypertensive effect in subjects already on a stable regimen of at least two antihypertensive drugs.