Enhancing monoamine oxidase B inhibitory activity via chiral fluorination: Structure-activity relationship, biological evaluation, and molecular docking study

Design and development of pyrazol-5-ylbenzamide derivatives containing chiral oxazoline moiety as fungicides based on molecular docking

BACKGROUND

Development of novel chiral antifungal agents for effective control of plant pathogens is urgently needed. In this study, a series of pyrazol-5-yl-benzamide derivatives containing chiral oxazoline moiety were rationally designed and developed based on molecular docking.

RESULTS

The in vitro antifungal assay results indicated that compounds (rac)-4h (R1 = Et), (S)-4 h (R1 = S-Et) and (R)-4 h (R1 = R-Et) exhibited remarkable antifungal activities against Valsa mali with median effective concentration (EC50) values of 0.24, 0.06 and 1.08 mg/L, respectively. Preliminary structure-activity relationships (SARs) revealed that the modification of the chiral substituent group at the oxazoline moiety significantly affected the antifungal activities of the target compounds. Furthermore, compounds (S)-4h (87.5%) and (R)-4h (84.3%) exhibited in vivo protective activities comparable to tebuconazole (87.5%) against V. mali. Subsequent molecular docking analysis, succinate dehydrogenase (SDH) enzyme inhibition assays and molecular dynamic (MD) simulations verified that the potential target enzyme of this class of derivatives could be SDH and helped to explain the large difference in antifungal activities of compounds (S)-4h and (R)-4h. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) observations confirmed that these two compounds severely disrupted the mycelial morphology of V. mali. Theoretical calculation studies provided some insight into the subsequent modification of such pyrazol-5-yl-benzamide derivatives. Resistance frequency studies showed that (S)-4h and (R)-4h treatments were less likely to produce resistant fungal strains than tebuconazole. Meanwhile, compounds (S)-4h and (R)-4h exhibited no apparent toxicity to the Apis mellifera L.

POPULATION

CONCLUSION

Therefore, these derivatives are potential candidates for the development of novel chiral fungicides for crop protection. © 2025 Society of Chemical Industry.

Proline Analogues in Drug Design: Current Trends and Future Prospects

Proline analogues are versatile chemical building blocks that enable modular construction of small-molecule drugs and pharmaceutical peptides. Over the past 15 years, the FDA has approved over 15 drugs containing proline analogues in their structures, five in the last three years alone (daridorexant, trofinetide, nirmatrelvir, rezafungin, danicopan). This perspective offers an analysis of the most common types of proline analogues currently trending in drug design. We focus on examples of fluoroprolines, α-methylproline, bicyclic proline analogues, and aminoprolines, while also highlighting proline analogues that remain underrepresented. We supplement our analysis with physicochemical information regarding the specific molecular properties of these moieties. Additionally, we discuss several intriguing cases where nonproline residues were replaced with proline analogues as a strategy to eliminate unwanted hydrogen bond donor sites. In conclusion, we present some suggestions for the future exploration of this promising class of molecular entities in drug discovery.

Recent progress in therapeutic applications of fluorinated five-membered heterocycles and their benzo-fused systems

Heterocyclic derivatives grafted with fluorine atom(s) have attracted the attention of scientists due to the unique physicochemical properties of the C-F bond. The inclusion of fluorine atom(s) into organic compounds often increases their lipophilicity and metabolic stability, enhancing their bioavailability and affinity for target proteins. Therefore, it is not surprising to find that more than 20% of the medications on the market contain fluorine, and nearly 300 fluorine-containing drugs have been officially approved for use as medicines. In this review article, we are interested in classifying and describing the reports comprising varied therapeutic activities of the directly fluorinated five-membered heterocycles and their fused systems during the last two decades. These therapeutic activities included antiviral, anti-inflammatory, enzymatic inhibitory, antimalarial, anticoagulant, antipsychotic, antioxidant, antiprotozoal, histamine-H3 receptor, serotonin receptor, chemokine receptor, prostaglandin-D2 receptor, and PBR inhibition activities. In many cases, the activities of fluorinated azoles were almost equal to or exceeded the potency of reference drugs.

Perry Disease: Current Outlook and Advances in Drug Discovery Approach to Symptomatic Treatment

Perry disease (PeD) is a rare, neurodegenerative, genetic disorder inherited in an autosomal dominant manner. The disease manifests as parkinsonism, with psychiatric symptoms on top, such as depression or sleep disorders, accompanied by unexpected weight loss, central hypoventilation, and aggregation of DNA-binding protein (TDP-43) in the brain. Due to the genetic cause, no causal treatment for PeD is currently available. The only way to improve the quality of life of patients is through symptomatic therapy. This work aims to review the latest data on potential PeD treatment, specifically from the medicinal chemistry and computer-aided drug design (CADD) points of view. We select proteins that might represent therapeutic targets for symptomatic treatment of the disease: monoamine oxidase B (MAO-B), serotonin transporter (SERT), dopamine D2 (D2R), and serotonin 5-HT1A (5-HT1AR) receptors. We report on compounds that may be potential hits to develop symptomatic therapies for PeD and related neurodegenerative diseases and relieve its symptoms. We use Phase pharmacophore modeling software (version 2023.08) implemented in Schrödinger Maestro as a ligand selection tool. For each of the chosen targets, based on the resolved protein-ligand structures deposited in the Protein Data Bank (PDB) database, pharmacophore models are proposed. We review novel, active compounds that might serve as either hits for further optimization or candidates for further phases of studies, leading to potential use in the treatment of PeD.

Design and Enantioselective Synthesis of Chiral Pyranone Fused Indole Derivatives with Antibacterial Activities against Xanthomonas oryzae pv oryzae for Protection of Rice

A new class of chiral pyranone fused indole derivatives were prepared by means of N-heterocyclic carbene (NHC) organocatalysis and demonstrated notable antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo). Bioassays showed that compounds (3S,4R)-5b, (3S,4R)-5d, and (3S,4R)-5l exhibited promising in vitro efficacy against Xoo, with EC50 values of 9.05, 9.71, and 5.84 mg/L, respectively, which were superior to that of the positive controls with commercial antibacterial agents, bismerthiazol (BT, EC50 = 27.8 mg/L) and thiodiazole copper (TC, EC50 = 70.1 mg/L). Furthermore, single enantiomer (3S,4R)-5l was identified as an optimal structure displaying 55.3% and 52.0% curative and protective activities against Xoo in vivo tests at a concentration of 200 mg/L, which slightly surpassed the positive control with TC (curative and protective activities of 47.2% and 48.8%, respectively). Mechanistic studies through molecular docking analysis revealed preliminary insights into the distinct anti-Xoo activity of the two single enantiomers (3S,4R)-5l and (3R,4S)-5l, wherein the (3S,4R)-configured stereoisomer could form a more stable interaction with XooDHPS (dihydropteroate synthase). These findings underscore the significant anti-Xoo potential of these chiral pyranone fused indole derivatives, and shall inspire further exploration as promising lead structures for a novel class of bactericides to combat bacterial infections and other plant diseases.

Safety, Tolerability, and Pharmacokinetics of the Monoamine Oxidase B Inhibitor, HEC122505, and its Major Metabolite After Single- and Multiple- Ascending Dose, and Food Effect Study in Healthy Chinese Subjects

BACKGROUND AND OBJECTIVES

HEC122505 is a potent and selectively monoamine oxidase B inhibitor that is safe and well-tolerated in preclinical models of Parkinson's disease. The objectives of single ascending dose and multiple dose pharmacokinetic trials of HEC122505 oral tablets were to determine the safety and tolerability of HEC122505, and to examine the food effect on the pharmacokinetic parameters of HEC122505 and its major metabolite HEC129870.

METHODS

The phase I study (NCT04625361) consisted of three arms: single ascending dose study (5, 20, 50, 100, 200, 300 or 400 mg HEC122505 tablets or placebo), multiple ascending dose study (20, 50 or 100 mg HEC122505 tablets or placebo once daily), and food effect (100 mg HEC122505 tablets single dose after a high-fat, high-calorie meal). All subjects completed all trial arms and were analyzed as planned.

RESULTS

Pharmacokinetic analysis showed that HEC122505 rapidly absorbed with the time to peak plasma concentration (Tmax) ranged from 0.5 to 1.75 h. In addition, maximum plasma drug concentration (Cmax) and area under the plasma concentration-time curve (AUC) increased in a dose proportional manner. Food effect study showed that a high-fat, high-calorie meal had no significant effect on the pharmacokinetics of HEC122505 and its major metabolite HEC129870, suggesting that HEC122505 could be administered in both fasted and fed state in clinical trials. The subsequent multiple-dose study evaluated doses from 20 to 100 mg dose once daily for up to 8 days. HEC122505 reached steady state after approximately 5 days with a once daily dose. In these studies, all dose of HEC122505 was generally safe and well tolerated. No grade ≥ 3 drug related adverse events (AEs) occurred.

CONCLUSION

HEC122505 was generally safe and well tolerated in the single ascending dose (ranging from 5 to 400 mg) and multiple ascending dose (50 to 200 mg once daily doses) studies. All the drug related adverse events (AEs) were Grade ≤ 2. There were no deaths, no subjects discontinued the trial due to AEs, and there were no other serious AEs. The safety and pharmacokinetic profile support once daily administration of HEC122505.

Design, synthesis and evaluation of novel monoamine oxidase B (MAO-B) inhibitors with improved pharmacokinetic properties for Parkinson's disease

A series of novel ((benzofuran-5-yl)methyl)pyrrolidine-2-carboxamide derivatives were designed, synthesized and evaluated as MAO-B inhibitors. SAR studies indicated that cyclizing benzyl ether into benzofuran ring resulted in the most potent MAO-B inhibitor (IC₅₀ = 0.037 μM), (2S,4S)-4-fluoro-1-((2-(4-fluorophenyl) benzofuran-5-yl)methyl)pyrrolidine-2-carboxamide (C14). PK properties of C14 in rats and mice were significantly improved compared to our previous candidate and safinamide, indicating that benzofuran moiety is essential for improving PK properties. Moreover, C14 displayed good metabolic stability and brain-blood barrier permeability, as well as favorable in vitro properties. Finally, C14 significantly inhibited MAO-B in the mouse brain. C14 exhibited a potential efficacy for DA deficits in the MPTP-induced mouse model and significantly increased DA concentration in the striatum. Thus, we identified that C14 may be a promising drug candidate for PD treatment.

Discovery of 3, 6-disubstituted isobenzofuran-1(3H)-ones as novel inhibitors of monoamine oxidases

Monoamine oxidases A and B (MAO-A and MAO-B) play important roles in biogenic amine metabolism, oxidative stress, and chronic inflammation. Particularly, MAO-B selective inhibitors are promising therapeutic choices for the treatment of neurodegenerative diseases, such as Pakinson's disease and Alzheimer's disease. Herein, novel 3,6-disubstituted isobenzofuran-1(3H)-ones were designed, synthesized and evaluated in vitro as inhibitors of monoamine oxidases A and B. Structure-activity relationships were investigated, and all of the compounds with (R)-3-hydroxy pyrrolidine moiety on the 6-position displayed preferable inhibition toward the MAO-B isoform. Among them, compounds 6c with a 4'-fluorobenzyl ring and 6m bearing a 3',4'-difluorobenzyl ring on the 3-position were the most potent MAO-B inhibitors with IC₅₀ values of 0.35 μM and 0.32 μM, respectively. The binding mode of compound 6m in MAO-B was predicted by CDOCKER program, revealing that (R)-3-hydroxypyrrolidine moiety is a critical structural feature for this series of MAO-B inhibitors. Compound 6m could serve as a new template structure for developing potent and selective MAO-B inhibitors.