Absolute Bioavailability of 2′-O-(2-Methoxyethyl)-Modified Antisense Oligonucleotides following Intraduodenal Instillation in Rats

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 296; no. 3; p. 898
• Main Authors: Richard S. Geary, Oleg Khatsenko, Keith Bunker, Rosanne Crooke, Max Moore, Todd Burckin, LoAnne Truong, Henri Sasmor, Arthur A. Levin
• Format: Journal Article
• Language: English
• Published: American Society for Pharmacology and Experimental Therapeutics 01.03.2001
• ISSN: 0022-3565; 1521-0103

Three modified 20-mer antisense oligonucleotides targeted to human intercellular adhesion molecule-1 mRNA were characterized for their presystemic stability and oral bioavailability compared with a first-generation phosphorothioate oligodeoxynucleotide (PS ODN), ISIS 2302. The three modified oligonucleotides contained 2′- O -(2-methoxyethyl) (2′- O -MOE) ribose sugar modifications on a portion, or on all of the nucleotides in the antisense sequence. In vitro metabolism studies conducted in various gastrointestinal and digestive tissue preparations indicated substantial improvement in stability of 2′- O -MOE-modified oligonucleotides. In addition, in vivo presystemic stability of these oligonucleotides was monitored in rats following intraduodenal administration. By 8 h after administration, only chain-shortened metabolites of the PS ODN were recovered in the gastrointestinal contents. In contrast, approximately 50% of the 2′- O -MOE ribose-modified (partial) compound remained intact (20-mer) by 8 h following administration. Both of the fully modified compounds (2′- O -MOE PO and PS) were completely stable with no measurable metabolites observed within 8 h of administration. The rank order of bioavailability was ISIS 11159 (full PS, full MOE) < ISIS 2302 (PS ODN) < ISIS 16952 (full PO, full MOE) < ISIS 14725 (full PS, partial MOE); the absolute plasma concentration bioavailability was measured in reference to intravenous dosing in the rat and was estimated at 0.3, 1.2, 2.1, and 5.5%, respectively. The optimal oligonucleotide chemistry for improved permeability and resulting bioavailability was the partially modified 3′ hemimer 2′- O -MOE phosphorothioate oligonucleotide (ISIS 14725). Improved presystemic stability coupled with improved permeability were likely responsible for the remarkable improvement in the oral bioavailability of this compound.