Editorial: Peptidomimetics: Synthetic Tools for Drug Discovery and Development

Non-traditional approaches for control of antibiotic resistance

INTRODUCTION

The drying up of antibiotic pipeline has necessitated the development of alternative therapeutic strategies to control the problem of antimicrobial resistance (AMR) that is expected to kill 10-million people annually by 2050. Newer therapeutic approaches address the shortcomings of traditional small-molecule antibiotics - the lack of specificity, evolvability, and susceptibility to mutation-based resistance. These 'non-traditional' molecules are biologicals having a complex structure and mode(s) of action that makes them resilient to resistance.

AREAS COVERED

This review aims to provide information about the non-traditional drug development approaches to tackle the problem of antimicrobial resistance, from the pre-antibiotic era to the latest developments. We have covered the molecules under development in the clinic with literature sourced from reviewed scholarly articles, official company websites involved in innovation of concerned therapeutics, press releases from the regulatory bodies, and clinical trial databases.

EXPERT OPINION

Formal introduction of non-traditional therapies in general practice can be quick and feasible only if supported with companion diagnostics and used in conjunction with established therapies. Owing to relatively higher development costs, non-traditional therapeutics require more funding as well as well as clarity in regulatory and clinical path. We are hopeful these issues are adequately addressed before AMR develops into a pandemic.

An integrated computational approach to infer therapeutic targets from Campylobacter concisus and peptidomimetic based inhibition of its pyrimidine metabolism pathway

Campylobacter concisus is a commensal of the human oral flora that has been allied with persistent diarrhea and inflammatory bowel disease (IBD). In children under the age of two, Campylobacter infections are common in the developing countries and have frequently been associated with mortality. They are becoming a prevalent cause of bacterial diarrhea in early adulthood in developed countries as well. The need for identifying new therapeutic targets and drugs is crucial for curbing such infections. Therefore, we identified 18 cytoplasmic potential therapeutic candidates against the type strain of C. concisus and deoxycytidine triphosphate deaminase (dCTP deaminase), involved in pyrimidine synthesis was selected for screening of peptidomimetic inhibitors (n > 30,000 peptidomimetics) against it. To the best of our knowledge, this target has not been studied for Campylobacter spp. Three potent inhibitors of this enzyme were prioritized i.e. peptidomimetic 27, 64, and 150. Dynamics simulation of 100 ns was carried out to validate findings for top-scored inhibitors along with physiology-based pharmacokinetics to estimate behavior in human body and predict dosing parameters. This verification demonstrates a first-in-human pharmacokinetic simulation for these peptidomimetics and can help enhance confidence in these peptide-like structures. Moiety 27 (IUPAC name: 5-[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-N-{[2-(2-methoxyethyl)-1-oxo-1H,2H,3H,4H-pyrrolo[1,2-a]pyrazin-3-yl]methyl}furan-2-carboxamide), 64 (IUPAC name: 3-(2-methylpropyl)-1-{3-[5-(5-oxo-1-phenylpyrrolidin-3-yl)-1,2,4-oxadiazol-3-yl]phenyl}urea), and 150 (IUPAC name: N-(3-methoxypropyl)-1-[6-(4-methylphenyl)-4H,6H,7H-[1,2,3]triazolo[4,3-c][1,4]oxazine-3-carbonyl]piperidine-4-carboxamide) were identified as potent inhibitors of C. concisus.Communicated by Ramaswamy H. Sarma.

Computational and in vitro analyses to identify the anticoagulant regions of Echicetin, a snake venom anticoagulant C-type lectin (snaclec): possibility to develop anticoagulant peptide therapeutics?

Snake venom C-type lectins (Snaclecs) display anticoagulant and platelet-modulating activities; however, their interaction with the critical components of blood coagulation factors was unknown. Computational analysis revealed that Echicetin (Snaclec from Echis carinatus venom) interacted with heavy chain of thrombin, and heavy and light chains of factor Xa (FXa). Based on FXa and thrombin binding regions of Echicetin, the two synthetic peptides (1A and 1B) were designed. The in silico binding studies of the peptides with thrombin and FXa showed that peptide 1B interacted with both heavy and light chains of thrombin and, peptide 1A interacted with only heavy chain of thrombin. Similarly, peptide 1B interacted with both heavy and light chains of FXa; however, peptide 1A interacted only with heavy chain of FXa. Alanine screening predicted the hot-spots residues for peptide 1A (Aspartic acid6, Valine8, Valine9, and Tyrosine17 with FXa, and Isoleucine14, Lysine15 with thrombin) and peptide 1B (Valine16 with FXa). Spectrofluorometric interaction study showed a lower Kd value for peptide 1B binding with both FXa and thrombin than peptide 1A, indicating higher binding strength of the former peptide. The circular dichroism spectroscopy also established the interaction between thrombin and the custom peptides. The in vitro study demonstrated higher anticoagulant activity of peptide 1B than peptide 1A due to higher inhibition of thrombin and FXa. Inhibition of anticoagulant activity of the peptides by respective anti-peptide antibodies corroborates our hypothesis that peptides 1A and 1B represent the anticoagulant regions of Echicetin and may be developed as antithrombotic peptide drug prototypes.Communicated by Ramaswamy H. Sarma.

The Use of Antibody-Antibiotic Conjugates to Fight Bacterial Infections

The emergence of antimicrobial resistance (AMR) is rapidly increasing and it is one of the significant twenty-first century’s healthcare challenges. Unfortunately, the development of effective antimicrobial agents is a much slower and complex process compared to the spread of AMR. Consequently, the current options in the treatment of AMR are limited. One of the main alternatives to conventional antibiotics is the use of antibody-antibiotic conjugates (AACs). These innovative bioengineered agents take advantage of the selectivity, favorable pharmacokinetic (PK), and safety of antibodies, allowing the administration of more potent antibiotics with less off-target effects. Although AACs’ development is challenging due to the complexity of the three components, namely, the antibody, the antibiotic, and the linker, some successful examples are currently under clinical studies.