Safety and tolerability study of aptiganel hydrochloride in patients with an acute ischemic stroke

Aptiganel (CNS 1102) is a selective, noncompetitive antagonist that acts on the ion channel associated with the N-methyl-D-aspartate (NMDA) receptor and is neuroprotective in experimental focal cerebral ischemia models at a plasma concentration of 10 ng/mL. In human volunteers, dose-limiting effects of aptiganel are blood pressure increases and central nervous system (CNS) excitation or depression. This study assessed the safety and tolerability of non-weight-adjusted doses of aptiganel in patients with acute ischemic stroke.

This was a double-blind, randomized, placebo-controlled multicenter study in patients presenting within 24 hours of acute ischemic stroke. Ascending single intravenous bolus doses of aptiganel (3, 4.5, 6, and 7.5 mg) were assessed in 21 patients with a 3:1 active drug:placebo randomization schedule. In 15 subsequent patients, selected bolus doses were followed by constant intravenous infusion for 6 to 12 hours (6 mg plus 1 mg/h, n=10; then 4.5 mg plus 0.75 mg/h, n=15) in a 4:1 randomization schedule. Prospectively collected pharmacokinetic data guided selection of infusion rates. Neurological and functional status were recorded at entry and after 1 week, although the study was not designed to test efficacy.

Forty-six patients were randomized from 4 centers (3 in the United States and 1 in the United Kingdom): 36 received aptiganel HCl, and 10 were given placebo. Hypertension and CNS events were commonly reported after a bolus dose of 7.5 mg and after a 6-mg bolus followed by an infusion of 1 mg/h. The lower regimen of 4.5-mg bolus followed by infusion of 0.75 mg/h achieved plasma aptiganel concentrations of >10 ng/mL and was well tolerated by patients but still raised systolic blood pressure by approximately 30 mm Hg over baseline.

A 4.5-mg intravenous bolus of aptiganel HCl followed by infusion of 0.75 mg/h for 12 hours is a tolerable dose that can produce plasma drug concentrations shown to be neuroprotective in animal models. However, increases in systolic blood pressure and an excess of CNS effects were both observed at this dose.