A novel bicyclic 2,4-diaminopyrimidine inhibitor of Streptococcus suis dihydrofolate reductase

Abstract

Streptococcus suis is a Gram-positive bacterial pathogen of pigs and an emerging zoonotic pathogen. It has become increasingly resistant to multiple classes of antibiotics. New drug candidates and knowledge of their targets are needed to combat antibiotic-resistant S. suis. In this study, the open-source Pathogen Box compound library was screened. Thirty hits that effectively inhibited S. suis growth at 10 µM were identified. Among the most potent hits, MMV675968 (a diaminoquinazoline analog) was shown to target S. suis dihydrofolate reductase (SsDHFR) via (1) growth inhibition of an E. coli surrogate whose growth is dependent on exogenously expressed SsDHFR and (2) inhibition of in vitro SsDHFR activity. Thymidine supplement is able to reverse growth inhibition by MMV675968 in both E. coli surrogate and S. suis, indicating that a thymidine-related pathway is a major target of MMV675968. Comparison of MMV675968 with seven DHFR inhibitors representing different core structures revealed that bicyclic 2,4-diaminopyrimidines with long and flexible side chains are highly effective in inhibiting SsDHFR and S. suis growth. MMV675968 and related compounds thus may serve as starting points for developing antibiotics against drug resistant S. suis.

Screening the MMV Pathogen Box reveals the mitochondrialbc1-complex as a drug target in matureToxoplasma gondiibradyzoites

“…Highly polar drugs such as fosmidomycin have previously been associated with poor efficacy against T. gondii due to a lack of parasite plasma membrane permeability (Nair et al 2012; Baumeister et al 2011). MMV675968 is a dually active T. gondii compound and has been shown to be a potent inhibitor of the dihydrofolate reductase (DHFR) in a range of pathogens (Songsungthong et al 2019, 2021; Kim et al 2021; Borba-Santos, Vila, and Rozental 2020; Nugraha et al 2019; Rollin-Pinheiro et al 2021; Vila and Lopez-Ribot 2017; Cantillon et al 2022). Although its target in T. gondii remains to be identified, pyrimethamine, which inhibits the dihydrofolate reductase-thymidylate synthetase in T. gondii is inactive against both in vitro and brain-resident bradyzoites (Christiansen et al 2022; Montazeri et al 2018).…”

Fighting Antibiotic Resistance: New Pyrimidine-Clubbed Benzimidazole Derivatives as Potential DHFR Inhibitors

“…This is accomplished by catalyzing the reduction of dihydrofolate to tetrahydrofolate via the use of NADPH in the process [ 10 ]. Inhibitors of DHFR are employed extensively in the treatment of fungal infections, bacterial diseases, and mycobacterial diseases, as well as in the fight against malaria [ 11 , 12 , 13 ]. When it comes to finding novel and effective inhibitors for this enzyme, the traditional drug-discovery methods only depend on the rational drug design-based elaboration of core scaffolds.…”

Reconstitution and functional characterization of efflux pumps from Escherichia coli

“…e) The sulphonamide family (Walzer et al, 1988) and diaminopyrimidines (Songsungthong et al, 2021), often in combination, inhibit the folate synthesis, which involves two enzymes in bacteria, dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR).…”