Discovery and Profiling of New Multimodal Phenylglycinamide Derivatives as Potent Antiseizure and Antinociceptive Drug Candidates

We developed a focused series of original phenyl-glycinamide derivatives which showed potent activity across <i>in vivo</i> mouse seizure models, namely, maximal electroshock (MES) and 6 Hz (using both 32 and 44 mA current intensities) seizure models. Following intraperitoneal (<i>i.p</i>.) administration, compound <b>(</b><b><i>R</i></b><b>)-32</b>, which was identified as a lead molecule, demonstrated potent protection against all seizure models with ED₅₀ values of 73.9 mg/kg (MES test), 18.8 mg/kg (6 Hz, 32 mA test), and 26.5 mg/kg (6 Hz, 44 mA test). Furthermore, <b>(</b><b><i>R</i></b><b>)-32</b> demonstrated efficacy in both the PTZ-induced kindling paradigm and the <i>iv</i>PTZ seizure threshold test. The expression of neurotrophic factors, such as mature brain-derived neurotrophic factor (mBDNF) and nerve growth factor (NGF), in the hippocampus and/or cortex of mice, and the levels of glutamate and GABA were normalized after PTZ-induced kindling by <b>(<i>R</i>)-32</b>. Importantly, besides antiseizure activity, (<b><i>R</i></b>)<b>-32</b> demonstrated potent antinociceptive efficacy in formalin-induced pain, capsaicin-induced pain, as well as oxaliplatin- and streptozotocin-induced peripheral neuropathy in mice (<i>i.p</i>.). No influence on muscular strength and body temperature in mice was observed. Pharmacokinetic studies and <i>in vitro</i> ADME-Tox data (<i>i.e.</i>, high metabolic stability in human liver microsomes, a weak influence on CYPs, no hepatotoxicity, satisfactory passive transport, <i>etc.</i>) proved favorable drug-like properties of (<b><i>R</i></b>)<b>-32</b>. Thermal stability of (<b><i>R</i></b>)-<b>32</b> shown in thermogravimetry and differential scanning calorimetry gives the opportunity to develop innovative oral solid dosage forms loaded with this compound. The <i>in vitro</i> binding and functional assays indicated its multimodal mechanism of action. (<b><i>R</i></b>)<b>-32</b>, beyond TRPV1 antagonism, inhibited calcium and sodium currents at a concentration of 10 μM. Therefore, the data obtained in the current studies justify a more detailed preclinical development of (<b><i>R</i></b>)<b>-32</b> for epilepsy and pain indications.