Neuromuscular therapeutics by RNA-targeted suppression of ACHE gene expression

RNA-targeted therapeutics offers inherent advantages over small molecule drugs wherever one out of several splice variant enzymes should be inhibited. Here, we report the use of Monarsen, a 20-mer acetylcholinesterase-targeted antisense agent with three 3′-2′o-methylprotected nucleotides, for selectively attenuating the stress-induced accumulation of the normally rare, soluble "readthrough" acetylcholinesterase variant AChE-R. Acetylcholine hydrolysis by AChE-R may cause muscle fatigue and moreover, limit the cholinergic anti-inflammatory blockade, yielding inflammation-associated pathology. Specific AChE-R targeting by Monarsen was achieved in cultured cells, experimental animals, and patient volunteers. In rats with experimental autoimmune myasthenia gravis, oral delivery of Monarsen improved muscle action potential in a lower dose regimen (nanomolar versus micromolar), rapid and prolonged manner (up to 72 h versus 2-4 h) as compared with the currently used small molecule anticholinesterases. In central nervous system neurons of both rats and cynomolgus monkeys, systematic Monarsen treatment further suppressed the levels of the proinflammatory cytokines interleukin-1 (IL-1) and IL-6. Toxicology testing and ongoing clinical trials support the notion that Monarsen treatment would offer considerable advantages over conventional cholinesterase inhibitors with respect to dosing, specificity, side effects profile, and duration of efficacy, while raising some open questions regarding its detailed mechanism of action.