Do CHT Inhibitors Constitute a Possible Therapeutic Strategy for Dystonia? Studies with the Novel CHT Inhibitor ML352

Dystonias are a group of disorders characterized by abnormal involuntary contracting of musculature that causes twisting and turning of a patient's body. Though the etiology of each type of dystonia varies, many forms are treated with anticholinergic medications ranging from the use of botulinum toxin to muscarinic receptor antagonists. Although the efficacy of cholinergic treatments is limited by side effects, mechanistic evidence for cholinergic dysfunction along with efficacy of current cholinergic treatments encouraged us to pursue the development of inhibitors of the high affinity choline transporter (CHT, SLC5A7) as a potential treatment of dystonia. CHT transports choline at cholinergic presynaptic terminals, is the rate‐limiting determinate of acetylcholine synthesis, and is subject to activity‐dependent regulation. In vitro brain slice studies demonstrate efficacy of CHT inhibition by the competitive, but highly toxic agent, hemicholinium‐3, in reversing maladaptive plasticities in dystonic mice (Martella et al, 2009; Sciamanna et al, 2012). Through a high‐throughput screen and subsequent chemical diversification effort (Ennis et al, 2015), we identified ML352 as a potent and, specific noncompetitive inhibitor of CHT. Our in vivo studies with CHT heterozygous knock out and overexpressing CHT BAC mice demonstrate that ML352 lethality is dependent on CHT gene dosage, consistent with the transporter as a major site of drug action in vivo. Ongoing studies using microdialysis and behavioral experiments seek to elucidate further in vivo effects of ML352 and its analogs in wild‐type and dystonia mouse models. ML352 provides a novel opportunity to evaluate CHT as a treatment for hypercholinergic disorders.Support or Funding InformationSupported by the Dystonia Medical Research Foundation and the National Institute of Neurological Disorders and Stroke (5R01NS077730 to W.T. Dauer).