Virtual Screening Approach and Investigation of Structure-Activity Relationships To Discover Novel Bacterial Topoisomerase Inhibitors Targeting Gram-Positive and Gram-Negative Pathogens

Bacterial resistance is increasing rapidly, requiring urgent identification of new antibacterial drugs that are effective against multidrug-resistant pathogens. Novel bacterial topoisomerase inhibitors (NBTIs) provide a new strategy for investigating the well-validated DNA gyrase and topoisomerase IV targets while preventing cross-resistance issues. On this basis, starting from a virtual screening campaign and subsequent structure-based hit optimization guided by X-ray studies, a novel class of piperazine-like NBTIs with outstanding enzymatic activity against Staphylococcus aureus and Escherichia coli DNA gyrase and topoisomerase IV was identified. Notably, compounds (±)-33, (±)-35, and (±)-36 with potent and balanced multitarget enzymatic profiles exhibited excellent efficacy against selected Gram-positive and Gram-negative pathogens, as well as clinically relevant resistant strains. Overall, the new NBTI chemotype described herein, owing to the broad-spectrum antibacterial activity and favorable in vitro safety profile, might serve as a basis for the development of novel treatments against serious infections.

Targeting Serotonin 2A and Adrenergic α1 Receptors for Ocular Antihypertensive Agents: Discovery of 3,4-Dihydropyrazino[1,2-b]indazol-1(2H)-one Derivatives

Glaucoma affects millions of people worldwide and causes optic nerve damage and blindness. The elevation of the intraocular pressure (IOP) is the main risk factor associated with this pathology, and decreasing IOP is the key therapeutic target of current pharmacological treatments. As potential ocular hypotensive agents, we studied compounds that act on two receptors (serotonin 2A and adrenergic α₁ ) linked to the regulation of aqueous humour dynamics. Herein we describe the design, synthesis, and pharmacological profiling of a series of novel bicyclic and tricyclic N2-alkyl-indazole-amide derivatives. This study identified a 3,4-dihydropyrazino[1,2-b]indazol-1(2H)-one derivative with potent serotonin 2A receptor antagonism, >100-fold selectivity over other serotonin subtype receptors, and high affinity for the α₁ receptor. Moreover, upon local administration, this compound showed superior ocular hypotensive action in vivo relative to the clinically used reference compound timolol.

Hit Optimization of 5-Substituted-N-(piperidin-4-ylmethyl)-1H-indazole-3-carboxamides: Potent Glycogen Synthase Kinase-3 (GSK-3) Inhibitors with in Vivo Activity in Model of Mood Disorders

Novel treatments for bipolar disorder with improved efficacy and broader spectrum of activity are urgently needed. Glycogen synthase kinase 3β (GSK-3β) has been suggested to be a key player in the pathophysiology of bipolar disorder. A series of novel GSK-3β inhibitors having the common N-[(1-alkylpiperidin-4-yl)methyl]-1H-indazole-3-carboxamide scaffold were prepared taking advantage of an X-ray cocrystal structure of compound 5 with GSK-3β. We probed different substitutions at the indazole 5-position and at the piperidine-nitrogen to obtain potent ATP-competitive GSK-3β inhibitors with good cell activity. Among the compounds assessed in the in vivo PK experiments, 14i showed, after i.p. dosing, encouraging plasma PK profile and brain exposure, as well as efficacy in a mouse model of mania. Compound 14i was selected for further in vitro/in vivo pharmacological evaluation, in order to elucidate the use of ATP-competitive GSK-3β inhibitors as new tools in the development of new treatments for mood disorders.