ML352

The neurotransmitter acetylcholine (ACh) plays a critical role in autonomic function, motor control, attention, learning, and memory, and reward. The high-affinity choline transporter (CHT) is the ratelimiting determinant of ACh synthesis, yet the transporter remains a largely undeveloped target for the detection and manipulation of synaptic cholinergic signaling. ML352 is a novel, noncompetitive inhibitor of the presynaptic choline transporter.

In vitro: At concentrations fully antagonized CHT in transfected cells and nerve terminal preparations, ML352 exhibited no inhibition of acetylcholinesterase or cholineacetyltransferase and also lacked activity at dopamine, serotonin, and norepinephrine transporters, as well as many receptors and ion channels. ML352 exhibited noncompetitive choline uptake inhibition in intact cells and reduced the apparent density of hemicholinium-3 binding sites in membrane assays, indicating allosteric transporter interactions [1].

In vivo: DMPK studies revealed a high intravenous plasma clearance, a combination of the oral bioavailability and total brain concentrations indicate ML352 to be a suitable probe for studies of altered in vivo ACh signaling and behavioral effects in rodents [2].

Clinical trial: Up to now, ML352 is still in the preclinical development stage.

Reference:
[1] Ennis EA, Wright J, Retzlaff CL, McManus OB, Lin Z, Huang X, Wu M, Li M, Daniels JS, Lindsley CW, Hopkins CR, Blakely RD.  Identification and characterization of ML352: a novel, noncompetitive inhibitor of the presynaptic choline transporter. ACS Chem Neurosci. 2015 Mar 18;6(3):417-27.
[2] Elizabeth Ennis Miss, Jane Wright, James Tarr, Charles Locuson, Corey Hopkins, J Daniels, Craig Lindsley and Randy Blakely.  A Novel Approach to Cholinergic Signaling Modulation: Development and Characterization of ML352, a Novel, Noncompetitive Inhibitor of the Presynaptic Choline Transporter. The FASEB Journal vol. 29 no. 1 Supplement 932.6


Optimization of the choline transporter (CHT) inhibitor ML352: Development of VU6001221, an improved in vivo tool compound.[Pubmed:27575469]

Bioorg Med Chem Lett. 2016 Oct 1;26(19):4637-4640.

This Letter describes the further lead optimization of the CHT inhibitor probe, ML352 (VU0476201), and the development of VU6001221, an improved in vivo tool. A multi-dimensional optimization effort encountered steep SAR, and ultimately, subtle tuning of the electronics of the central phenyl core provided VU6001221, a CHT inhibitor with comparable potency for choline uptake inhibition as ML352, yet improved PK and CNS penetration. Moreover, VU6001221 enabled evaluation, for the first time, of a CHT inhibitor in a standard preclinical rodent cognition model, novel object recognition (NOR). We observed VU6001221 to elicit a dose-responsive increase in NOR, raising the possibility of agonism of synaptic alpha7 nicotinic ACh receptors by elevated extracellular choline, that if confirmed would represent a novel molecular strategy to enhance cognition.

Identification and characterization of ML352: a novel, noncompetitive inhibitor of the presynaptic choline transporter.[Pubmed:25560927]

ACS Chem Neurosci. 2015 Mar 18;6(3):417-27.

The high-affinity choline transporter (CHT) is the rate-limiting determinant of acetylcholine (ACh) synthesis, yet the transporter remains a largely undeveloped target for the detection and manipulation of synaptic cholinergic signaling. To expand CHT pharmacology, we pursued a high-throughput screen for novel CHT-targeted small molecules based on the electrogenic properties of transporter-mediated choline transport. In this effort, we identified five novel, structural classes of CHT-specific inhibitors. Chemical diversification and functional analysis of one of these classes identified ML352 as a high-affinity (Ki = 92 nM) and selective CHT inhibitor. At concentrations that fully antagonized CHT in transfected cells and nerve terminal preparations, ML352 exhibited no inhibition of acetylcholinesterase (AChE) or cholineacetyltransferase (ChAT) and also lacked activity at dopamine, serotonin, and norepinephrine transporters, as well as many receptors and ion channels. ML352 exhibited noncompetitive choline uptake inhibition in intact cells and synaptosomes and reduced the apparent density of hemicholinium-3 (HC-3) binding sites in membrane assays, suggesting allosteric transporter interactions. Pharmacokinetic studies revealed limited in vitro metabolism and significant CNS penetration, with features predicting rapid clearance. ML352 represents a novel, potent, and specific tool for the manipulation of CHT, providing a possible platform for the development of cholinergic imaging and therapeutic agents.