We conducted a focused and systematic structure-activity relationship study¹ on the 4-chloro-2-(2-phenoxyacetamido)benzoic acid scaffold, shared by known inhibitors of TRPM4, which is a Ca²⁺-activated, voltage-dependent monovalent cation channel associated with various diseases². Our series of synthetic compounds revealed valuable SAR trends and ultimately led to the discovery of PBA, which exhibited increased potency, ligand efficiency, aqueous solubility, and lipophilic ligand efficiency, as well as lower cytotoxicity than reference inhibitor NBA. In addition, PBA inhibited both mouse and human TRPM4, but had no effect on hTRPM5, a closely related Ca²⁺-activated, voltage-dependent monovalent cation channel. Building on these insights from the SAR study, our next goal is to develop chemical probes for the spatiotemporal control of TRPM4 using light. Azobenzene-functionalized compounds have so far demonstrated efficient photoswitchable behaviour, long thermal relaxation times and promising biological activity. Additionally, single-crystal X-ray diffraction structures of our 4-chloro-2-(2-phenoxyacetamido)benzoic acid-based compounds revealed strong bifurcated intramolecular hydrogen bonds stabilizing a “bent” and completely flat conformation. Through a synthetic structure-property relationship study combining X-ray, melting points, NMR, and solubility measurements, we discovered that these hydrogen bonds are retained in solution and probably decrease aqueous solubility due to π-π-stacking. We believe that the bent conformation is important for these inhibitors’ mode of action. Currently, we are working to increase the solubility of PBA by breaking the molecular planarity of the compounds.

[1] C. E. Gerber, B. S. Augustynek, P. Grossenbacher, B. Hauert, S. A. Singer, C. Peinelt, M. Lochner, Journal of Medicinal Chemistry, 2026, 69, 8763-8789
[2] B. Preti, J.-S. Rougier, I. Papapostolou, F. Bochen, C. E. Gerber, H. Abriel, M. Lochner, C. Peinelt, CHIMIA, 2022, 76, 1039–1044