MS‐Based Screening of 5‐Substituted Nipecotic Acid Derived Hydrazone Libraries as Ligands of the GABA Transporter 1

Abstract

A screening of compound libraries based on nipecotic acid derivatives with lipophilic residues attached to the scarcely explored 5‐position of the core structure was used for the search of new inhibitors of the γ‐aminobutyric acid (GABA) transporter 1 (mGAT1). The generated compound libraries, which were based on hydrazone chemistry commonly used in dynamic combinatorial chemistry but rendered pseudostatic, were screened for their binding affinities toward mGAT1 by means of MS Binding Assays. With nipecotic acid derived hydrazone rac‐16 h [rac‐(3R,5S)‐{5‐[(E)‐2‐{[5‐(2‐phenylethynyl)thiophen‐2‐yl]methylidene}hydrazin‐1‐yl]piperidine‐3‐carboxylic acid}‐sodium chloride (1/2)], one hit was found and evaluated displaying sub‐micromolar potency (pKi=6.62±0.04) and a noncompetitive interaction mode at mGAT1. By bearing a 5‐(2‐phenylethynyl)thiophen‐2‐yl residue attached to the 5‐position of nipecotic acid via a three‐atom spacer, compound rac‐16 h contains a structural moiety so far unprecedented for these kinds of bioactive molecules, and complements novel 5‐substituted nipecotic acid derived ligands of mGAT1 revealed in a recently published screening campaign. This new class of ligands, with an inhibition mode distinct from that of benchmark mGAT1 inhibitors, could serve as research tools for investigations of mGAT1‐mediated GABA transport.

Protein-Directed Dynamic Combinatorial Chemistry: An Efficient Strategy in Drug Design

“…Recently, the use of a MS-based screening applied to the discovery GABA uptake inhibitors was reported by Hauke et al 11 The gamma-aminobutyric acid transporter 1 (GAT1) removes GABA, which is an important inhibitory neurotransmitter in the central nervous system. This approach enabled the screening of a vast diversity of lipophilic residues in a nicopetic acid derivative hydrazine library.…”