Effect of sodium caprate on the intestinal absorption of two modified antisense oligonucleotides in pigs

Sodium caprate, a medium chain fatty acid, is known to enhance the transport of drugs across the intestinal mucosa in cell culture systems and small animal species. The aim of the present study was to evaluate the effect of this enhancer on the oral absorption of two chemically modified antisense oligonucleotides ISIS 2503 (phosphorothioate) and ISIS 104838 (methoxyethyl modified phosphorothioate) using an intra-intestinal catheterised pig model. Sodium caprate at doses 25, 50 and 100 mg/kg was effective in enhancing systemic delivery of both antisense chemistries. At all enhancer doses, the absorption of both chemistries was rapid (T(max) 10 min) and short lived (plasma levels fell below detection by 2 h following administration). The pharmacokinetic parameters (AUC, C(max), T(max)) of both chemistries were unchanged with the increase in the permeation enhancer dose. The oral bioavailability with methoxyethyl modified phosphorothioate (ISIS 104838) was higher relative to unmodified phosphorothioate. Sodium caprate was rapidly absorbed following intra-intestinal administration (T(max) approximately 7 min regardless of the dose) and its pharmacokinetics were linear with dose. All tested formulations were well tolerated by the animals and no abnormal histopathological findings were observed following histological evaluation of intestinal tissues from pigs exposed to multi-dose administration of sodium caprate. It is concluded that sodium caprate can improve the oral delivery of antisense oligonucleotides in pigs and that its membrane-permeation effect is rapid, short-lived and dose independent.