Therapeutic potential of lefamulin in the treatment of community-acquired pneumonia

Antibiotics with novel mode of action as new weapons to fight antimicrobial resistance

Antimicrobial resistance (AMR) is a major public health issue, causing 5 million deaths per year. Without any action plan, AMR will be in a near future the leading cause of death ahead of cancer. AMR comes from the ability of bacteria to rapidly develop and share resistance mechanisms towards current antibiotics, rendering them less effective. To circumvent this issue and avoid the phenomenon of cross-resistance, new antibiotics acting on novel targets or with new modes of action are required. Today, the pipeline of potential new treatments with these characteristics includes promising compounds such as gepotidacin, zoliflodacin, ibezapolstat, MGB-BP-3, CRS-3123, afabicin and TXA-709, which are currently in clinical trials, and lefamulin, which has been recently approved by FDA and EMA. In this review, we report the chemical synthesis, mode of action, structure-activity relationships, in vitro and in vivo activities as well as clinical data of these eight small molecules listed above.

Lefamulin: a New Hope in the Field of Community-Acquired Bacterial Pneumonia

Purpose of Review

Community-acquired bacterial pneumonia (CABP) continues to be a worldwide health concern since it is the major cause of mortality and hospitalisation worldwide. Increased macrolide resistance among Streptococcus pneumoniae and other infections has resulted in a significantly larger illness burden, which has been exacerbated by evolving demography and a higher prevalence of comorbid disorders. Owing to such circumstances, the creation of new antibiotic classes is critical.

Recent Findings

Lefamulin, also referred to as BC-3781, is the primary pleuromutilin antibiotic which has been permitted for both intravenous and oral use in humans for the remedy of bacterial infections. It has shown activity against gram-positive bacteria including methicillin-resistant strains as well as atypical organisms which as often implicated in CABP. It has a completely unique mechanism of action that inhibits protein synthesis via way of means of stopping the binding of tRNA for peptide transfer. The C(14) side chain is responsible for its pharmacodynamic and antimicrobial properties, together with supporting in overcoming bacterial ribosomal resistance and mutations improvement amplifying the number of hydrogen bonds to the target site.

Summary

This review aims to highlight the pre-existing treatment options and specific purposes to shed some light upon the development of a new drug lefamulin and its specifications and explore this novel drug’s superior efficacy to already existing treatment strategies.

Synthesis, biological activities and docking studies of pleuromutilin derivatives with piperazinyl urea linkage

Antibiotics resistance is becoming increasingly common, involving almost all antibiotics on the market. Diseases caused by drug resistant bacteria, such as MRSA, have high mortality and negatively affect public health. The development of new drugs would be an effective means of solving this problem. Modifications based on bioactive natural products could greatly shorten drug development time and improve success rate. Pleuromutilin, a natural product from the basidiomycete bacterial species, is a promising antibiotic candidate. In this study, a series of novel pleuromutilin derivatives possessing piperazinyl urea linkage were efficiently synthesised, and their antibacterial activities and bactericidal properties were evaluated via MIC, MBC and Time-kill kinetics assays. The results showed that all compounds exhibited potent activities against tested strains, especially MRSA strains with MIC values as low as 0.125 μg/mL; 8 times lower than that of marketed antibiotic Tiamulin. Docking studies indicate substituted piperazinyl urea derivatives could provide hydrogen bonds and initiate π-π stacking between molecules and surrounding residues.

Clinical Pharmacokinetics and Pharmacodynamics of Lefamulin

Lefamulin (Xenleta) has been approved by the US FDA for the treatment of community-acquired bacterial pneumonia (CABP). It may be taken intravenously or orally and has activity against a broad range of pulmonary pathogens, including Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydophila pneumonia, as well as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. Lefamulin has an adverse effect profile that is similar to other antimicrobial agents commonly used to treat CABP. Despite these promising features, the use of lefamulin remains limited in clinical practice. However, given the rise of antibiotic-resistant organisms, this may soon change. This review examines what is known about the pharmacokinetics and pharmacodynamics of lefamulin and looks ahead to its potential applications in clinical practice, including the treatment of sexually transmitted infections such as multidrug-resistant Mycoplasma genitalium, as well as its role as a synergistic agent used in combination with other antimicrobials in the treatment of drug-resistant organisms.

A history of antimicrobial drugs in animals: Evolution and revolution

The evolutionary process of antimicrobial drug (AMD) uses in animals over a mere eight decades (1940-2020) has led to a revolutionary outcome, and both evolution and revolution are ongoing, with reports on a range of uses, misuses and abuses escalating logarithmically. As well as veterinary therapeutic perspectives (efficacy, safety, host toxicity, residues, selection of drug, determination of dose and measurement of outcome in treating animal diseases), there are also broader, nontherapeutic uses, some of which have been abandoned, whilst others hopefully will soon be discontinued, at least in more developed countries. Although AMD uses for treatment of animal diseases will continue, it must: (a) be sustainable within the One Health paradigm; and (b) devolve into more prudent, rationally based therapeutic uses. As this review on AMDs is published in a Journal of Pharmacology and Therapeutics, its scope has been made broader than most recent reviews in this field. Many reviews have focused on negative aspects of AMD actions and uses, especially on the question of antimicrobial resistance. This review recognizes these concerns but also emphasizes the many positive aspects deriving from the use of AMDs, including the major research-based advances underlying both the prudent and rational use of AMDs. It is structured in seven sections: (1) Introduction; (2) Sulfonamide history; (3) Nontherapeutic and empirical uses of AMDs (roles of agronomists and veterinarians); (4) Rational uses of AMDs (roles of pharmacologists, clinicians, industry and regulatory controls); (5) Prudent use (residue monitoring, antimicrobial resistance); (6) International and inter-disciplinary actions; and (7) Conclusions.

Lefamulin: A Novel Oral and Intravenous Pleuromutilin for the Treatment of Community-Acquired Bacterial Pneumonia

Lefamulin is a novel oral and intravenous (IV) pleuromutilin developed as a twice-daily treatment for community-acquired bacterial pneumonia (CABP). It is a semi-synthetic pleuromutilin with a chemical structure that contains a tricyclic core of five-, six-, and eight-membered rings and a 2-(4-amino-2-hydroxycyclohexyl)sulfanylacetate side chain extending from C14 of the tricyclic core. Lefamulin inhibits bacterial protein synthesis by binding to the 50S bacterial ribosomal subunit in the peptidyl transferase center (PTC). The pleuromutilin tricyclic core binds to a pocket close to the A site, while the C14 side chain extends to the P site causing a tightening of the rotational movement in the binding pocket referred to as an induced-fit mechanism. Lefamulin displays broad-spectrum antibacterial activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria as well as against atypical bacteria that commonly cause CABP. Pleuromutilin antibiotics exhibit low rates of resistance development and lack cross-resistance to other antimicrobial classes due to their unique mechanism of action. However, pleuromutilin activity is affected by mutations in 23S rRNA, 50S ribosomal subunit proteins rplC and rplD, ATP-binding cassette (ABC)-F transporter proteins such as vga(A), and the methyltransferase cfr. The pharmacokinetic properties of lefamulin include: volume of distribution (V_d) ranging from 82.9 to 202.8 L, total clearance (CL_T) of 19.5 to 21.4 L/h, and terminal elimination half-life (t_1/2) of 6.9-13.2 h; protein binding of lefamulin is high and non-linear. The oral bioavailability of lefamulin has been estimated as 24% in fasted subjects and 19% in fed subjects. A single oral dose of lefamulin 600 mg administered in fasted patients achieved a maximum plasma concentration (C_max) of 1.2-1.5 mg/L with a time of maximum concentration (T_max) ranging from 0.8 to 1.8 h, and an area under the plasma concentration-time curve from 0 to infinity (AUC_0-∞) of 8.5-8.8 mg h/L. The pharmacodynamic parameter predictive of lefamulin efficacy is the free plasma area under the concentration-time curve divided by the minimum inhibitory concentration (fAUC_24h/MIC). Lefamulin efficacy has been demonstrated using various animal models including neutropenic murine thigh infection, pneumonia, lung infection, and bacteremia. Lefamulin clinical safety and efficacy was investigated through a Phase II clinical trial of acute bacterial skin and skin structure infection (ABSSSI), as well as two Phase III clinical trials of CABP. The Phase III trials, LEAP 1 and LEAP 2 established non-inferiority of lefamulin to moxifloxacin in both oral and IV formulations in the treatment of CABP. The United States Food and Drug Administration (FDA), European Medicines Agency (EMA), and Health Canada have each approved lefamulin for the treatment of CABP. A Phase II clinical trial has been completed for the treatment of ABSSSI, while the pediatric program is in Phase I. The most common adverse effects of lefamulin include mild-to-moderate gastrointestinal-related events such as nausea and diarrhea. Lefamulin represents a safe and effective option for treating CABP in cases of antimicrobial resistance to first-line therapies, clinical failure, or intolerance/adverse effects to currently used agents. Clinical experience and ongoing clinical investigation will allow clinicians and antimicrobial stewardship programs to optimally use lefamulin in the treatment of CABP.

Synthesis, biological activities, and docking study of novel chalcone-pleuromutilin derivatives

The issue of antibiotic resistance is becoming progressively serious these days, and the feasible solution to address it is to develop and discover novel antibiotics. The diterpene natural pleuromutilin is a prominent candidate for its special mode of action by inhibiting protein synthesis. In this study, a series of novel pleuromutilin derivatives with chalcone moiety was designed and synthesized, and their antibacterial activities were assessed in vitro. As suggested from the results, most of compounds exhibited potent activities against two methicillin-resistant Staphylococcus aureus (MRSA) ATCC 33591 and 43300. The further modification of the chalcone structure, aza-cyclic derivatives were afforded and then assessed, and potent activities against the tested strains were reported. The preliminary docking studies were conducted to explore the interactions between target molecules and binding site.

An overview of lefamulin for the treatment of community acquired bacterial pneumonia

INTRODUCTION

Lefamulin is a novel antibiotic that belongs to the pleuromutilin class with excellent activity against all microorganisms, including atypical pathogens, that cause community-acquired pneumonia (CAP).

AREAS COVERED

This article reviews the spectrum of activity, the main pharmacokinetic and pharmacodynamic characteristics of lefamulin as well as its clinical efficacy and safety in the treatment of CAP in adult patients.

EXPERT OPINION

The clinical efficacy of lefamulin in patients with non severe CAP has been demonstrated in 2 randomized clinical trials. Precisely one of the limitations of the phase 3 trials is that the proportion of severe CAP cases is very low. Its particular mechanism of action, affecting ribosomal protein synthesis, provides a low probability of cross-resistance to other commonly used antibiotics in CAP. These findings, together with the antimicrobial activity of lefamulin, its pharmacokinetic parameters and safety profile make it a good alternative for outpatient treatment of CAP. In patients hospitalized with CAP, lefamulin can be used as a potential oral step-down agent after an intravenous regimen with beta-lactams, or as a therapeutic alternative in patients with β-lactam allergies.