A method to screen a wide variety of drug candidates without laborious purification steps could advance the fight against drug-resistant bacteria.
Shutterstock/Saiful52
Efforts to combat the increasing threat of drug-resistant bacteria are being assisted by a new approach for streamlining the search for antimicrobial drug candidates, pioneered by researchers at Hokkaido University, led by Assistant Professor Kazuki Yamamoto and Professor Satoshi Ichikawa of the Faculty of Pharmaceutical Sciences. Their methods, developed together with researchers elsewhere in Japan and in the USA, are discussed in an article in the journal Nature Communications.
Antimicrobial resistance (AMR) in bacteria poses a major and ever-increasing challenge to healthcare worldwide, leaving clinicians struggling to treat a wide range of serious and potentially fatal infections.
One promising target for new drugs against a variety of AMR bacteria is an enzyme embedded in bacterial cell membranes called phospho-N-acetylmuramoyl-pentapeptide-transferase (MraY). This enzyme catalyzes formation of a specific lipid molecule, called lipid I, that is essential for bacteria to survive. Several inhibitors of MraY activity are already known, but improved versions are urgently required.
"In this study, we used four known classes of MraY inhibitors that are used as antibiotics," explains Yamamoto. "We developed a drug discovery platform (in situ build-up library method) that combines a comprehensive synthesis method for natural product derivatives and direct biological activity evaluation."
The team split known inhibitors into MraY binding regions (cores) and activity modulating regions (accessories). From 7 cores and 98 accessories, they generated a library of 686 MraY inhibitor analogs. These analogs were tested against MraY, and eight analogs possessing strong MraY inhibitory and antibacterial activity were identified.
"After splitting the natural products, we attached aldehyde groups to the cores and hydrazine groups to the accessories. These groups react with each other to produce a hydrazone bond-allowing us to create the analog library in a straightforward manner," Yamamoto elaborates.
Preparation of the MraY inhibitor analog library. (Photo: Kazuki Yamamoto)
The eight analogs were resynthesized in stable forms and their effectiveness was verified. Analog 2 had the highest effectiveness against drug-resistant strains followed by analogs 3 and 6. Additionally, analog 2 was effective in mouse infection models-a very promising feature, as demonstrating efficacy in live animals is a key step towards developing successful new drugs.
Early indications also suggest the candidate drugs currently identified have low toxicity against cells other than the targeted bacteria, raising hopes that they could lead to a range of antimicrobials that could safely be used in patients.
"We have also demonstrated the wider potential of our drug discovery approach by applying it to identifying useful activity in the tubulin-binding natural products epothilone B, paclitaxel, and vinblastine (anti-cancer drugs)," adds Ichikawa. "We were able to construct a library of 588 analogs within just one month."
By showing that their method can be applied to other classes of medication, the researchers have opened a significantly more general new avenue in drug development.
Original Article:
Kazuki Yamamoto, et al. Development of a natural product optimization strategy for inhibitors against MraY, a promising antibacterial target. Nature Communications. June 14, 2024.
DOI: 10.1038/s41467-024-49484-7
Funding:
This research was supported in part by Japan Society for the Promotion of Science (JSPS) KAKENHI Grant-in-Aid for Scientific Research (B) (22H02738, 19H03345, 21H03622), Grant-in Aid for Scientific Research on Innovative Areas "Frontier Research on Chemical Communications" (18H04599, 20H04757), Grant-in-Aid for Research for Young Scientist (JP19K16648), Grant-in-Aid for Research Activity Start-up (22K20704); Takeda Foundation; The Tokyo Biomedical Research Foundation; Hokkaido University, Global Facility Centre (GFC), Pharma Science Open Unit (PSOU), funded by MEXT under "Support Program for Implementation of New Equipment Sharing System"; the Japan Agency for Medical Research and Development (AMED) under Platform Project for Supporting Drug Discovery and Life Science Research (Basis for Supporting Innovative Drug Discovery and Life Science Research (BINDS); JP18am0101093j0002, JP22ama121039), AMED-CREST (JP23gm1610012, JP23gm1610013), AMED (JP19ak0101118h0001, 21ak0101118h9903), Japan Science and Technology Agency (JST) START Program (ST211004JO); Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) from the Ministry of Education, Culture, Sport, Science, and Technology in Japan, MEXT for the Joint Research Program of the Research Centre for Zoonosis Control, Hokkaido University; and the Duke Science Technology Scholar Fund.
