DT-0111: a novel P2X3 receptor antagonist

Abstract

Extracellular adenosine 5'-triphosphate (ATP) acts as an autocrine and paracrine agent, the actions of which on affected cells are mediated by P2 receptors (P2R), which include trans cell-membrane cationic channels (P2XRs), and G protein coupled receptors (P2YRs). The mammalian P2X receptors form homotrimeric or heterotrimeric cationic channels, each of which contains three ATP-binding sites. There are seven homotrimeric P2X receptors (P2X1-7) and three heteromeric (P2X2/P2X3, P2X4/P2X6, P2X1/P2X5). In the lungs and airways, ATP activates P2X3 and P2X2/3 receptors (P2X3R, P2X2/3R, respectively) localized on vagal sensory nerve terminals resulting in bronchoconstriction, and cough, and probably also localized release of pro-inflammatory neuropeptides via the axon reflex. Currently, several P2X3R and P2X2/3R antagonists are being developed as drug-candidates for the treatment of chronic cough. This report presents the receptor affinity data of a novel water-soluble small molecule, DT-0111, that acts as a selective P2X3R antagonist.

Keywords: Adenosine 5’-triphosphate; Asthma; Bronchodilation; COPD; Cough; Vagus nerve.

Fig. 1

Molecular structure of DT-0111

Fig. 2

Dose response curves of DT-0111 and two agonists at P2Y1R site as determined by Ca.²⁺ influx. (SEM, n = 3–4; all figures)

Fig. 3

Dose response curves of DT-0111 and UTP P2Y2R site

Fig. 4

Dose response curve of DT-0111 at P2Y2R site

Fig. 5

Dose responses curves of DT-0111 and nor-epinephrine (300 nM) at α2_B adrenergic receptor

Fig. 6

Dose response curves of DT-0111 and substance P (300 nM) at the neurokinin 3 (NK3) receptor site

Fig. 7

A, B: Representative traces of P2X3R-current and P2X2/3R-current evoked by increasing concentrations of the reference agonist α,β-methylene ATP. C: Fitting of the average (mean ± SE) of the dose response curves of α,β-methylene ATP for P2X3R (LogEC₅₀ 6.13 ± 0.05, n = 28). D: Fitting of the average (mean ± SE) of the dose response curves of α,β-methylene ATP for P2X2/3R (LogEC₅₀ 5.11 ± 0.11, n = 36)

Fig. 8

A: Representative traces of P2X3R-current evoked by 1 µM α,β-methylene ATP in control (black line) and in the presence of increasing concentrations of reference compound AF353. B: Representative traces of P2X2/3R-current evoked by 1 µM α,β-methylene ATP in control (black line) and in the presence of increasing concentrations of reference compound AF353. C: Fitting of average (mean ± SE) of the dose response curves of AF353 on P2X3R peak currents (IC₅₀ 52.5 nM, n = 7). D: Fitting of average (mean ± SE) of the dose response curves of AF353 on both P2X2/3R-peak and sustained currents (IC₅₀ 59.9 and 68.6 nM, n = 10, respectively)

Fig. 9

A: Representative traces of P2X3R-current evoked by 1 µM α,β-methylene ATP in control (black line) and in the presence of increasing concentrations of compound DT-0111. B: Representative traces of P2X2/3R-current evoked by 8 µM α,β-methylene ATP in control (black line) and in the presence of increasing concentrations of compound DT-0111. C: Fitting of average (mean ± SE) of the dose response curves of compound DT-0111 (IC₅₀ 31.2 ± 2.15 nM, n = 6). D: Fitting of average (mean ± SE) of the dose response curves of compound DT-0111 (n = 5)