The main protease (Mpro) of SARS-CoV-2 is an essential enzyme that plays a critical part in the virus’s life cycle, making it a significant target for developing antiviral drugs. The inhibition of SARS-CoV-2 Mpro has emerged as a promising approach for developing therapeutic agents to treat COVID-19. This review explores the structure of the Mpro protein and analyzes the progress made in understanding protein–ligand interactions of Mpro inhibitors. It focuses on binding kinetics, origin, and the chemical structure of these inhibitors. The review provides an in-depth analysis of recent clinical trials involving covalent and non-covalent inhibitors and emerging dual inhibitors targeting SARS-CoV-2 Mpro. By integrating findings from the literature and ongoing clinical trials, this review captures the current state of research into Mpro inhibitors, offering a comprehensive understanding of challenges and directions in their future development as anti-coronavirus agents. This information provides new insights and inspiration for medicinal chemists, paving the way for developing more effective Mpro inhibitors as novel COVID-19 therapies.

Background: The phosphodiesterase 10 (PDE10) family, identified in 1999, is mainly expressed in the brain, particularly in the striatum, within the medium spiny neurons, nucleus accumbens, and olfactory tubercle. Inhibitors of PDE10 (PDE10-Is) are a conceptually rational subject for medicinal chemistry with potential use in the treatment of psychiatric and neurodegenerative diseases. Objective: This review is based on peer-reviewed published articles, and summarizes the cellular and molecular biology of PDE10 as a rational target for psychiatric and neurodegenerative drug discovery. Here, we present the classification of PDE10-Is from a medicinal chemistry point of view across a wide range of different, drug-like chemotypes starting from theophylline and caffeine analogs, papaverine and dimethoxy catechol type PDE10-Is, TP-10, MP-10, MP-10/papaverine/quinazoline series inhibitors, and ending with the newest inhibitors obtained from fragment-based lead discovery (FBLD). The authors have collated recent research on inhibition of PDE10A as a promising therapeutic strategy for psychiatric and neurodegenerative diseases, based on its efficacy in animal models of schizophrenia, Parkinson’s, Huntington’s, and Alzheimer’s diseases. This review also presents pharmacological data on PDE10-Is as possible therapeutics for the treatment of cognitive deficits, obesity and depression. Moreover, it summarizes the current strategies for PDE10-Is drug discovery based on the results of clinical trials. The authors also present the latest studies on crystal structures of PDE10 complexes with novel inhibitors.

The present study aimed to design and synthesize a new series of hybrid compounds with pyrrolidine-2,5-dione and thiophene rings in the structure as potential anticonvulsant and antinociceptive agents. For this purpose, we obtained a series of new compounds and evaluated their anticonvulsant activity in animal models of epilepsy (maximal electroshock (MES), psychomotor (6 Hz), and subcutaneous pentylenetetrazole (scPTZ) seizure tests). To determine the mechanism of action of the most active anticonvulsant compounds (3, 4, 6, 9), their influence on the voltage-gated sodium and calcium channels as well as GABA transporter (GAT) was assessed. The most promising compound 3-(3-methylthiophen-2-yl)-1-(3-morpholinopropyl)pyrrolidine-2,5-dione hydrochloride (4) showed higher ED₅₀ value than those of the reference drugs: valproic acid (VPA) and ethosuximide (ETX) (62.14 mg/kg vs. 252.7 mg/kg (VPA) in the MES test, and 75.59 mg/kg vs. 130.6 mg/kg (VPA) and 221.7 mg/kg (ETX) in the 6 Hz test, respectively). Moreover, in vitro studies of compound 4 showed moderate but balanced inhibition of the neuronal voltage-sensitive sodium (site 2) and L-type calcium channels. Additionally, the antinociceptive activity of the most active compounds (3, 4, 6, 9) was also evaluated in the hot plate test and writhing tests, and their hepatotoxic properties in HepG2 cells were also investigated. To determine the possible mechanism of the analgesic effect of compounds 3, 6, and 9, the affinity for the TRPV1 receptor was investigated.