Chronic cough relief by allosteric modulation of P2X3 without taste disturbance

Abstract

P2X receptors are cation channels that sense extracellular ATP. Many therapeutic candidates targeting P2X receptors have begun clinical trials or acquired approval for the treatment of refractory chronic cough (RCC) and other disorders. However, the present negative allosteric modulation of P2X receptors is primarily limited to the central pocket or the site below the left flipper domain. Here, we uncover a mechanism of allosteric regulation of P2X3 in the inner pocket of the head domain (IP-HD), and show that the antitussive effects of quercetin and PSFL2915 (our nM-affinity P2X3 inhibitor optimized based on quercetin) on male mice and guinea pigs were achieved by preventing allosteric changes of IP-HD in P2X3. While being therapeutically comparable to the newly licensed P2X3 RCC drug gefapixant, quercetin and PSFL2915 do not have an adverse effect on taste as gefapixant does. Thus, allosteric modulation of P2X3 via IP-HD may be a druggable strategy to alleviate RCC.

Druggable site near the upper vestibule determines the high affinity and P2X3 homotrimer selectivity of sivopixant/S‐600918 and its analogue DDTPA

“…This pocket differs from that of the marketed drug gefapixant/AF-219, which is formed by the left flipper, dorsal fin and upper body domains, as we have identified earlier (Wang et al, 2018). It is worth noting that as multiple allosteric changes induced by ATP binding were identified (R. Jiang et al, 2013), each of which will have one or more small molecule binding sites, preventing allosteric changes by small molecule binding is a viable solution for P2X drug design (Guo et al, 2023;Huang et al, 2014;R. Jiang et al, 2012).…”

“…Four potential extracellular sites were identified, including SI, the lower region of the body domain near the extracellular lumen (Guo et al, 2023); SII, above the ATP recognition site and near the head domain; SIII, the upper vestibule; SIV, outside the upper region of the upper vestibule. And then, DDTPA was docked in silico to these putative binding sites (see Methods and Figure 2b).…”

Discovery of Triazolopyrimidine Derivatives as Selective P2X3 Receptor Antagonists Binding to an Unprecedented Allosteric Site as Evidenced by Cryo-Electron Microscopy

“…In fact, intrathecal injection of P2X3R antisense oligonucleotide (ASO) induced P2X3R downregulation and exhibited antihyperalgesic and antiallodynic effects in rat neuropathic pain models. − Therefore, P2X3R has been investigated as a drug target for the treatment of chronic neuropathic pain modulating hyperalgesia and allodynia . More recently, chronic cough as another indication related with P2X3R has been explored and validated in several clinical studies, − since upregulated expression and increased activation of P2X3R were reported to be relevant for this inflammatory disease state in the respiratory tract. − …”