Cadazolid: A new hope in the treatment of Clostridium difficile infection

Antibiotic resistant bacteria: current situation and treatment options to accelerate the development of a new antimicrobial arsenal

INTRODUCTION

Antibiotic resistance is one of the biggest public health threats worldwide. Currently, antibiotic-resistant bacteria kill 700,000 people every year. These data represent the near future in which we find ourselves, a "post-antibiotic era" where the identification and development of new treatments are key. This review is focused on the current and emerging antimicrobial therapies which can solve this global threat.

AREAS COVERED

Through a literature search using databases such as Medline and Web of Science, and search engines such as Google Scholar, different antimicrobial therapies were analyzed, including pathogen-oriented therapy, phagotherapy, microbiota and antivirulent therapy. Additionally, the development pathways of new antibiotics were described, emphasizing on the potential advantages that the combination of a drug repurposing strategy with the application of mathematical prediction models could bring to solve the problem of AMRs.

EXPERT OPINION

This review offers several starting points to solve a single problem: reducing the number of AMR. The data suggest that the strategies described could provide many benefits to improve antimicrobial treatments. However, the development of new antimicrobials remains necessary. Drug repurposing, with the application of mathematical prediction models, is considered to be of interest due to its rapid and effective potential to increase the current therapeutic arsenal.

Discovery and Development of Antibacterial Agents: Fortuitous and Designed

Today, antibacterial drug resistance has turned into a significant public health issue. Repeated intake, suboptimal and/or unnecessary use of antibiotics, and, additionally, the transfer of resistance genes are the critical elements that make microorganisms resistant to conventional antibiotics. A substantial number of antibacterials that were successfully utilized earlier for prophylaxis and therapeutic purposes have been rendered inadequate due to this phenomenon. Therefore, the exploration of new molecules has become a continuous endeavour. Many such molecules are at various stages of investigation. A surprisingly high number of new molecules are currently in the stage of phase 3 clinical trials. A few new agents have been commercialized in the last decade. These include solithromycin, plazomicin, lefamulin, omadacycline, eravacycline, delafloxacin, zabofloxacin, finafloxacin, nemonoxacin, gepotidacin, zoliflodacin, cefiderocol, BAL30072, avycaz, zerbaxa, vabomere, relebactam, tedizolid, cadazolid, sutezolid, triclosan and afabiacin. This article aims to review the investigational and recently approved antibacterials with a focus on their structure, mechanisms of action/resistance, and spectrum of activity. Delving deep, their success or otherwise in various phases of clinical trials is also discussed while attributing the same to various causal factors.

In Vitro and In Vivo Activities, Absorption, Tissue Distribution, and Excretion of OBP-4, a Potential Anti-Clostridioides difficile Agent

Clostridioides difficile infection (CDI) is considered a major concern of the health care system globally, with an increasing need for alternative therapies. OBP-4, a new oxazolidinone-fluoroquinolone hybrid with excellent in vitro activities and good safety, shows promising features as an antibacterial agent. Here, we further evaluated the in vitro and in vivo activities of OBP-4 against C. difficile and its absorption (A), distribution (D), and excretion (E) profiles in rats. In vitro assays indicated that OBP-4 was active against all tested C. difficile strains, with MICs ranging from 0.25 to 1 mg/liter. In addition, OBP-4 showed complete inhibition of spore formation at 0.5× MIC. In the mouse model of CDI, 5-day oral treatment with OBP-4 provided complete protection from death and CDI recurrence in infected mice. However, cadazolid (CZD) and vancomycin (VAN) showed less protection of infected mice than did OBP-4 in terms of diarrhea and weight loss, especially VAN. Subsequently, ADE investigations of OBP-4 with a reliable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method showed extremely low systemic exposure and predominantly fecal excretion, resulting in a high local concentration of OBP-4 in the intestinal tract-the site of CDI. These results demonstrated that OBP-4 possesses good activity against C. difficile and favorable ADE characteristics for oral treatment of CDI, which support further development of OBP-4 as a potential anti-CDI agent.

The Strategies of Pathogen-Oriented Therapy on Circumventing Antimicrobial Resistance

The emerging antimicrobial resistance (AMR) poses serious threats to the global public health. Conventional antibiotics have been eclipsed in combating with drug-resistant bacteria. Moreover, the developing and deploying of novel antimicrobial drugs have trudged, as few new antibiotics are being developed over time and even fewer of them can hit the market. Alternative therapeutic strategies to resolve the AMR crisis are urgently required. Pathogen-oriented therapy (POT) springs up as a promising approach in circumventing antibiotic resistance. The tactic underling POT is applying antibacterial compounds or materials directly to infected regions to treat specific bacteria species or strains with goals of improving the drug efficacy and reducing nontargeting and the development of drug resistance. This review exemplifies recent trends in the development of POTs for circumventing AMR, including the adoption of antibiotic-antibiotic conjugates, antimicrobial peptides, therapeutic monoclonal antibodies, nanotechnologies, CRISPR-Cas systems, and microbiota modulations. Employing these alternative approaches alone or in combination shows promising advantages for addressing the growing clinical embarrassment of antibiotics in fighting drug-resistant bacteria.

Cadazolid vs Vancomycin for the Treatment of Clostridioides difficile Infection: Systematic Review with Meta-analysis

Background

Current guidelines recommend the use of vancomycin for the initial treatment of Clostridioides difficile Infection (CDI). Cadazolid, an experimental drug, has been utilized and compared in several studies with varying results.

Methods

A systematic literature search was performed using electronic databases [Medline, Google Scholar and Cochrane] for eligible studies. Randomized Controlled Trials (RCTs) comparing cadazolid with vancomycin for CDI treatment were included. Demographic variables and outcomes (CDI resolution, CDI recurrence, and adverse events) were collected. The primary outcome was clinical cure rate defined as the resolution of CDI at the end of a 10-day course.

Results

Two studies with three RCTs met the inclusion criteria with a total of 1283 patients with CDI who received either cadazolid 250 mg twice daily (624 patients) or vancomycin 125 mg four times daily (659 patients). Clinical cure rate at the end of the treatment was not statistically significant (pooled OR= 0.82; 95% CI = 0.61 to 1.11; p=0.20; I²= 0%). Sustained clinical response at clinical follow-up was also not significantly different (pooled OR = 1.14; 95% CI = 0.91 to 1.43; p=0.27; I² = 0%). Cadazolid had a lower recurrence rate than vancomycin (pooled OR = 0.71; 95% CI = 0.52 to 0.98; p=0.04; I² = 13%).

Conclusion

Cadazolid is non-inferior to vancomycin and offers a promising alternative for the treatment of CDI. More studies including RCTs and longitudinal studies with large and diverse patient population are needed to further confirm this. Furthermore, cadazolid should also be compared with fidaxomicin in a head-to-head trial to evaluate their efficacy for CDI.

High 30-day readmission rates associated with Clostridiumdifficile infection

BACKGROUND

Clostridium difficile infection (CDI) is a leading cause of community-onset and healthcare-associated infection, with high recurrence rates, and associated high morbidity and mortality. We report national rates, leading causes, and predictors of hospital readmission for CDI.

METHODS

Retrospective study of data from the 2013 Nationwide Readmissions Database of patients with a primary diagnosis of CDI and re-hospitalization within 30-days. A multivariate regression model was used to identify predictors of readmission.

RESULTS

Of 38,409 patients admitted with a primary diagnosis of CDI, 21% were readmitted within 30-days, and 27% of those patients were readmitted with a primary diagnosis of CDI. Infections accounted for 47% of all readmissions. Female sex, anemia/coagulation defects, renal failure/electrolyte abnormalities and discharge to home (versus facility) were 12%, 13%, 15%, 36%, respectively, more likely to be readmitted with CDI.

CONCLUSIONS

We found that 1-in-5 patients hospitalized with CDI were readmitted to the hospital within 30-days. Infection comprised nearly half of these readmissions, with CDI being the most common etiology. Predictors of readmission with CDI include female sex, history of renal failure/electrolyte imbalances, anemia/coagulation defects, and being discharged home. CDI is associated with a high readmission risk, with evidence of several predictive risks for readmission.

Cationic biaryl 1,2,3-triazolyl peptidomimetic amphiphiles targeting Clostridioides (Clostridium) difficile: Synthesis, antibacterial evaluation and an in vivo C. difficile infection model

Clostridioides (formerly Clostridium) difficile is a Gram-positive anaerobic bacterial pathogen that causes severe gastrointestinal infection in humans. The current chemotherapeutic options are vastly inadequate, expensive and limited; this results in an exorbitant medical and financial burden. New, inexpensive chemotherapeutic treatments for C. difficile infection with improved efficacy are urgently needed. A streamlined synthetic pathway was developed to allow access to 38 novel mono- and di-cationic biaryl 1,2,3-triazolyl peptidomimetics with increased synthetic efficiency, aqueous solubility and enhanced antibacterial efficacy. The monocationic arginine derivative 28 was identified as a potent, Gram-positive selective antibacterial with MIC values of 4 μg/mL against methicillin-resistant Staphylococcus aureus and 8 μg/mL against C. difficile. Furthermore, the dicationic bis-triazole analogue 50 was found to exhibit broad-spectrum activity with substantial Gram-negative efficacy against Acinetobacter baumannii (8 μg/mL), Pseudomonas aeruginosa (8 μg/mL) and Klebsiella pneumoniae (16 μg/mL); additionally, compound 50 displayed reduced haemolytic activity (<13%) in an in vitro haemolysis assay. Membrane-disruption assays were conducted on selected derivatives to confirm the membrane-active mechanism of action inherent to the synthesized amphiphilic compounds. A comparative solubility assay was developed and utilized to optimize the aqueous solubility of the compounds for in vivo studies. The biaryl peptidomimetics 28 and 67 were found to exhibit significant efficacy in an in vivo murine model of C. difficile infection by reducing the severity and slowing the onset of disease.

Clostridium difficile infection in oncology patients: epidemiology, pathophysiology, risk factors, diagnosis, and treatment

Clostridium difficile infection (CDI) is one of the most common healthcare-associated infections in the United States. Its incidence has been increasing in the recent years despite preventative measures. CDI increases annual expenses by 1.5 billion dollars. Cancer patients are at higher risk to acquire CDI, as explained by their frequent exposure to risk factors. CDI in cancer patients is associated with higher mortality rates and prolonged hospitalization. Furthermore, CDI affects the course of the disease by delaying treatments such as chemotherapy. Chemotherapeutics drugs are considered independent risk factors for CDI. This review discusses Clostridium difficile infection in cancer patients, including those who are receiving chemotherapy. Herein, we summarize recent data regarding the epidemiology, risk factors, including chemotherapy regimens, pathogenesis, diagnostic techniques and treatment options, including newer agents. Method: A literature search was performed using the PubMed and Google Scholar databases. The MeSH terms utilized in different combinations were 'clostridium difficile', 'neoplasia/cancer/oncology', 'chemotherapy', 'diagnosis', and 'treatment', in addition to looking up each treatment option individually to generate a comprehensive search. The articles were initially screened by title alone, followed by screening through abstracts. Full texts of pertinent articles (including letters to editors, case reports, case series, cohort studies, and clinical trials) were included in this review.

New and emerging therapies in treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) represents one of the most serious nosocomial infections that have grown dramatically over the past decade. Vancomycin and metronidazole are currently used as a standard therapy for CDI. Metronidazole is recommended as a first-line therapy for mild-to-moderate infections and vancomycin is mainly used for severe and/or refractory cases. However, studies have demonstrated that there are quite high CDI relapse rates with both of these medications, which represents a challenge for clinicians. Over the last decade, a number of newer and novel therapeutic options have emerged as promising alternatives to these standard CDI therapies. The following review provides the updated summaries of these newer therapeutic agents and their status in the treatment of CDI.

Novel Antimicrobials for the Treatment of Clostridium difficile Infection

The current picture of Clostridium difficile infection (CDI) is alarming with a mortality rate ranging between 3% and 15% and a CDI recurrence rate ranging from 12% to 40%. Despite the great efforts made over the past 10 years to face the CDI burden, there are still gray areas in our knowledge on CDI management. The traditional anti-CDI antimicrobials are not always adequate in addressing the current needs in CDI management. The aim of our review is to give an update on novel antimicrobials for the treatment of CDI, considering the currently available evidences on their efficacy, safety, molecular mechanism of action, and their probability to be successfully introduced into the clinical practice in the near future. We identified, through a PubMed search, 16 novel antimicrobial molecules under study for CDI treatment: cadazolid, surotomycin, ridinilazole, LFF571, ramoplanin, CRS3123, fusidic acid, nitazoxanide, rifampin, rifaximin, tigecycline, auranofin, NVB302, thuricin CD, lacticin 3147, and acyldepsipeptide antimicrobials. In comparison with the traditional anti-CDI antimicrobial treatment, some of the novel antimicrobials reviewed in this study offer several advantages, i.e., the favorable pharmacokinetic and pharmacodynamic profile, the narrow-spectrum activity against CD that implicates a low impact on the gut microbiota composition, the inhibitory activity on CD sporulation and toxins production. Among these novel antimicrobials, the most active compounds in reducing spore production are cadazolid, ridinilazole, CRS3123, ramoplanin and, potentially, the acyldepsipeptide antimicrobials. These antimicrobials may potentially reduce CD environment spread and persistence, thus reducing CDI healthcare-associated acquisition. However, some of them, i.e., surotomycin, fusidic acid, etc., will not be available due to lack of superiority versus standard of treatment. The most CD narrow-spectrum novel antimicrobials that allow to preserve microbiota integrity are cadazolid, ridinilazole, auranofin, and thuricin CD. In conclusion, the novel antimicrobial molecules under development for CDI have promising key features and advancements in comparison to the traditional anti-CDI antimicrobials. In the near future, some of these new molecules might be effective alternatives to fight CDI.

Advances in the diagnosis and treatment of Clostridium difficile infections

Clostridium difficile is a leading cause of antibiotic-associated diarrhea worldwide. The diagnosis of C. difficile infection (CDI) requires both clinical manifestations and a positive laboratory test for C. difficile and/or its toxins. While antibiotic therapy is the treatment of choice for CDI, there are relatively few classes of effective antibiotics currently available. Therefore, the development of novel antibiotics and/or alternative treatment strategies for CDI has received a great deal of attention in recent years. A number of emerging agents such as cadazolid, surotomycin, ridinilazole, and bezlotoxumab have demonstrated activity against C. difficile; some of these have been approved for limited clinical use and some are in clinical trials. In addition, other approaches such as early and accurate diagnosis of CDI as well as disease prevention are important for clinical management. While the toxigenic culture and the cell cytotoxicity neutralization assay are still recognized as the gold standard for the diagnosis of CDI, new diagnostic approaches such as nucleic acid amplification methods have become available. In this review, we will discuss both current and emerging diagnostic and therapeutic modalities for CDI.

Evidence-Based Practice in the Treatment for Antibiotic-Associated Diarrhea in the Intensive Care Unit

Unit nurses provide care to patients with serious health conditions. Often antibiotics are recommended to fight infections. Sometimes patients are on proton pump inhibitors (PPI). Antibiotics and PPIs may lead to diarrhea, causing the patient more discomfort, and possibly leading to a more serious infection. One serious infection is caused by Clostridium difficile, which causes death in some cases. About 75% of patients on antibiotics may not need antibiotics. Several studies showed less diarrhea in patients on probiotics. However, probiotics cause harm to some patients, which needs to be considered. Nurses need to ensure that antibiotic stewardship is followed.

Colon-Targeted Delivery of IgY Against Clostridium difficile Toxin A and B by Encapsulation in Chitosan-Ca Pectinate Microbeads

This study investigated the use of a newly developed chitosan-Ca pectinate microbead formulation for the colon-targeted delivery of anti-A/B toxin immunoglobulin of egg yolk (IgY) to inhibit toxin binding to colon mucosa cells. The effect of the three components (pectinate, calcium chloride, and chitosan) used for the microbead production was examined with the aim of identifying the optimal levels to improve drug encapsulation efficiency, swelling ratio, and cumulative IgY release rate. The optimized IgY-loaded bead component was pectin 5% (w/v), CaCl₂ 3% (w/v), and chitosan 0.5% (w/v). Formulated beads were spherical with 1.2-mm diameter, and the drug loading was 45%. An in vitro release study revealed that chitosan-Ca pectinate microbeads inhibited IgY release in the upper gastrointestinal tract and significantly improved the site-specific release of IgY in the colon. An in vivo rat study demonstrated that 72.6% of biologically active IgY was released specifically in the colon. These results demonstrated that anti-A/B toxin IgY-loaded chitosan-Ca pectinate oral microbeads improved IgY release behavior in vivo, which could be used as an effective oral delivery platform for the biological treatment of Clostridium difficile infection (CDI).

Update on Antimicrobial Resistance in Clostridium difficile: Resistance Mechanisms and Antimicrobial Susceptibility Testing

Oral antibiotics such as metronidazole, vancomycin and fidaxomicin are therapies of choice for Clostridium difficile infection. Several important mechanisms for C. difficile antibiotic resistance have been described, including the acquisition of antibiotic resistance genes via the transfer of mobile genetic elements, selective pressure in vivo resulting in gene mutations, altered expression of redox-active proteins, iron metabolism, and DNA repair, as well as via biofilm formation. This update summarizes new information published since 2010 on phenotypic and genotypic resistance mechanisms in C. difficile and addresses susceptibility test methods and other strategies to counter antibiotic resistance of C. difficile.

Novel antibiotics in development to treat Clostridium difficile infection

PURPOSE OF REVIEW

Clostridium difficile infections (CDI) remain a challenge to treat clinically due primarily to limited number of antibiotics available and unacceptably high recurrence rates. Because of this, there has been significant demand for creating innovative therapeutics, which has resulted in the development of several novel antibiotics.

RECENT FINDINGS

This review updates seven different antibiotics that are currently in development to treat CDI including fidaxomicin, surotomycin, ridinilazole, ramoplanin, cadazolid, LFF571, and CRS3123. Available preclinical and clinical data are compared between these antibiotics.

SUMMARY

Many of these new antibiotics display almost ideal properties for antibiotics directed against CDI. Despite these properties, not all clinical development of these compounds has been successful. These studies have provided key insights into the pathogenesis of CDI and will continue to inform future drug development. Successful phase III clinical trials should result in several new and novel antibiotics to treat CDI.

Antimicrobial Peptides Targeting Gram-Positive Bacteria

Antimicrobial peptides (AMPs) have remarkably different structures as well as biological activity profiles, whereupon most of these peptides are supposed to kill bacteria via membrane damage. In order to understand their molecular mechanism and target cell specificity for Gram-positive bacteria, it is essential to consider the architecture of their cell envelopes. Before AMPs can interact with the cytoplasmic membrane of Gram-positive bacteria, they have to traverse the cell wall composed of wall- and lipoteichoic acids and peptidoglycan. While interaction of AMPs with peptidoglycan might rather facilitate penetration, interaction with anionic teichoic acids may act as either a trap for AMPs or a ladder for a route to the cytoplasmic membrane. Interaction with the cytoplasmic membrane frequently leads to lipid segregation affecting membrane domain organization, which affects membrane permeability, inhibits cell division processes or leads to delocalization of essential peripheral membrane proteins. Further, precursors of cell wall components, especially the highly conserved lipid II, are directly targeted by AMPs. Thereby, the peptides do not inhibit peptidoglycan synthesis via binding to proteins like common antibiotics, but form a complex with the precursor molecule, which in addition can promote pore formation and membrane disruption. Thus, the multifaceted mode of actions will make AMPs superior to antibiotics that act only on one specific target.

Challenges in management of recurrent and refractory Clostridium difficile infection

Clostridium difficile infection (CDI) is the most common nosocomial infection in the United States and is associated with a high mortality. One quarter of patients treated for CDI have at least one recurrence. Spore persistence, impaired host immune response and alteration in the gastrointestinal microbiome due to antibiotic use are factors in recurrent disease. We review the etiology of recurrent CDI and best approaches to management including fecal microbiota transplantation.

Recent Advances in the Rational Design and Optimization of Antibacterial Agents

This review discusses next-generation antibacterial agents developed using rational, or targeted, drug design strategies. The focus of this review is on small-molecule compounds that have been designed to bypass developing bacterial resistance, improve the antibacterial spectrum of activity, and/or to optimize other properties, including physicochemical and pharmacokinetic properties. Agents are discussed that affect known antibacterial targets, such as the bacterial ribosome, nucleic acid binding proteins, and proteins involved in cell-wall biosynthesis; as well as some affecting novel bacterial targets which do not have currently marketed agents. The discussion of the agents focuses on the rational design strategies employed and the synthetic medicinal chemistry and structure-based design techniques utilized by the scientists involved in the discoveries, including such methods as ligand- and structure-based strategies, structure-activity relationship (SAR) expansion strategies, and novel synthetic organic chemistry methods. As such, the discussion is limited to small-molecule therapeutics that have confirmed macromolecular targets and encompasses only a fraction of all antibacterial agents recently approved or in late-stage clinical trials. The antibacterial agents selected have been recently approved for use on the U.S. or European markets or have shown promising results in phase 2 or phase 3 U.S.

CLINICAL TRIALS

Clostridium difficile infection: a review of current and emerging therapies

Clostridium difficile (C. difficile) infection (CDI) is the most common cause of ­healthcare-associated infections in US hospitals. The epidemic strain NAP1/BI/ribotype 027 accounts for outbreaks worldwide, with increasing mortality and severity. CDI is acquired from an endogenous source or from spores in the environment, most easily acquired during the hospital stay. The use of antimicrobials disrupts the intestinal microflora enabling C. difficile to proliferate in the colon and produce toxins. Clinical diagnosis in symptomatic patients requires toxin detection from stool specimens and rarely in combination with stool culture to increase sensitivity. However, stool culture is essential for epidemiological studies. Oral metronidazole is the recommended therapy for milder cases of CDI and oral vancomycin or fidaxomicin for more severe cases. Treatment of first recurrence involves the use of the same therapy used in the initial CDI. In the event of a second recurrence oral vancomycin often given in a tapered dose or intermittently, or fidaxomicin may be used. Fecal transplantation is playing an immense role in therapy of recurrent CDI with remarkable results. Fulminant colitis and toxic megacolon warrant surgical intervention. Novel approaches including new antibiotics and immunotherapy against CDI or its toxins appear to be of potential value.

Oxazolidinone antimicrobials: a patent review (2012-2015)

INTRODUCTION

Antimicrobial resistance in Gram-positive bacteria is a major health care issue. This review summarizes patent publications from 2012 to 2015 that divulged novel oxazolidinones as antibacterial agents.

AREAS COVERED

A total of 25 patents obtained from Espacenet, WIPO Patentscope and FreePatentsOnline, and AcclaimIP search engines were reviewed. The patents were scrutinized based on the novelty of the compounds, their antibacterial activity (MIC, µg/mL), and the process of preparation. The oxazolidinones with promising antibacterial activity were classified according to the following structural diversities, as biaryl heterocyclic, fused heteroaryl rings containing oxazolidinones, and others. The biaryl heterocyclic, fused heteroaryl, benzoxazine, and the 1H-pyrazol-1-yl containing oxazolidinone derivatives demonstrated potent antibacterial activities superior to linezolid against Gram-positive bacteria. Some derivatives were effective against standard strains of Gram-negative bacteria, namely Moraxella catarrhalis ATCC A894, and Escherichia coli ATCC 25922. In addition, a patent disclosed a structural isomer of linezolid with marginal activity against the aerobic Gram-negative bacteria MDR Stenotrophomonas (Xanthomonas) maltophilia, while linezolid and vancomycin did not inhibit growth. Finally, some derivatives showed activity against respiratory infectious diseases' causative agents, such as B. anthracis, B. mallei, Y. pestis, and M. pneumoniae.

EXPERT OPINION

Overall, there is limited in vivo data to support the potential clinical advancement of the currently reported novel derivatives.