MBX-500, a hybrid antibiotic with in vitro and in vivo efficacy against toxigenic Clostridium difficile

Comparison between Symptomatic and Asymptomatic Mice after Clostridioides difficile Infection Reveals Novel Inflammatory Pathways and Contributing Microbiota

Clostridioides difficile causes the highest number of nosocomial infections. Currently, treatment options for C. difficile infection (CDI) are very limited, resulting in poor treatment outcomes and high recurrence rates. Although the disease caused by CDI is inflammatory in nature, the role of inflammation in the development of CDI symptoms is contradictory and not completely understood. Hence, the use of anti-inflammatory medication is debatable in CDI. In the current study, we evaluated the genetic and microbiome profiles of mice after infection with C. difficile. These mice were categorized based on the severity of CDI and the results were viewed accordingly. Our results indicate that certain genes are upregulated in severe CDI more than in the moderate case. These include oncostatin-M (OSM), matrix metalloprotease 8 (MMP8), triggering receptor expressed on myeloid cells 1 (Trem-1), and dual oxidase 2 (Duox2). We also investigated the microbiome composition of CDI mice before and after infecting with C. difficile. The results show that C. difficile abundance is not indicative of diseases severity. Certain bacterial species (e.g., Citrobacter) were enriched while others (e.g., Turicibacter) were absent in severe CDI. This study identifies novel inflammatory pathways and bacterial species with a potential role in determining the severity of CDI.

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.

Improving therapy of severe infections through drug repurposing of synergistic combinations

Infections from multidrug resistant (MDR) pathogens and emerging viruses present challenges for effective clinical treatments. Drug repurposing and combination screens may provide therapies at a fraction of the time and cost of traditional methods of drug development. Synergistic combinations of two or three known compounds can increase therapeutic efficacy and reduce concentrations required for individual drugs, in turn, reducing the risk of drug toxicity. Using libraries of approved drugs, traditionally non-antibiotic compounds identified in repurposing screens can quickly move into clinical trials, since safety profiles have been previously established. Herein we summarize recent advances in identifying synergistic drug combinations and the use of drug screens for personalized medicine treatments of infections caused by MDR pathogens and emerging viruses.

Discovery and development of DNA polymerase IIIC inhibitors to treat Gram-positive infections

Despite the growing global crisis caused by antimicrobial drug resistance among pathogenic bacteria, the number of new antibiotics, especially new chemical class of antibiotics under development is insufficient to tackle the problem. Our review focuses on an emerging class of antibacterial therapeutic agents that holds a completely novel mechanism of action, namely, inhibition of bacterial DNA polymerase IIIC. The recent entry of this new class into human trials may herald the introduction of novel drugs whose novel molecular target precludes cross-resistance with existing antibiotic classes. This review therefore examines the evolution of DNA pol IIIC inhibitors from the discovery of 6-(p-hydroxyphenylazo)uracil (HPUra) in the 1960s to the development of current first-in-class N7-substituted guanine drug candidate ACX-362E, now under clinical development for the treatment of Clostridioides difficile infection.

Management of adult Clostridium difficile digestive contaminations: a literature review

Clostridium difficile infections (CDI) dramatically increased during the last decade and cause a major public health problem. Current treatments are limited by the high disease recurrence rate, severity of clinical forms, disruption of the gut microbiota, and colonization by vancomycin-resistant enterococci (VRE). In this review, we resumed current treatment options from official recommendation to promising alternatives available in the management of adult CDI, with regard to severity and recurring or non-recurring character of the infection. Vancomycin remains the first-line antibiotic in the management of mild to severe CDI. The use of metronidazole is discussed following the latest US recommendations that replaced it by fidaxomicin as first-line treatment of an initial episode of non-severe CDI. Fidaxomicin, the most recent antibiotic approved for CDI in adults, has several advantages compared to vancomycin and metronidazole, but its efficacy seems limited in cases of multiple recurrences. Innovative therapies such as fecal microbiota transplantation (FMT) and antitoxin antibodies were developed to limit the occurrence of recurrence of CDI. Research is therefore very active, and new antibiotics are being studied as surotomycin, cadazolid, and rinidazole.

Effect of the Synthetic Bile Salt Analog CamSA on the Hamster Model of Clostridium difficile Infection

Clostridium difficile infection (CDI) is the leading cause of antibiotic-associated diarrhea and has gained worldwide notoriety due to emerging hypervirulent strains and the high incidence of recurrence. We previously reported protection of mice from CDI using the antigerminant bile salt analog CamSA. Here we describe the effects of CamSA in the hamster model of CDI. CamSA treatment of hamsters showed no toxicity and did not affect the richness or diversity of gut microbiota; however, minor changes in community composition were observed. Treatment of C. difficile-challenged hamsters with CamSA doubled the mean time to death, compared to control hamsters. However, CamSA alone was insufficient to prevent CDI in hamsters. CamSA in conjunction with suboptimal concentrations of vancomycin led to complete protection from CDI in 70% of animals. Protected animals remained disease-free at least 30 days postchallenge and showed no signs of colonic tissue damage. In a delayed-treatment model of hamster CDI, CamSA was unable to prevent infection signs and death. These data support a putative model in which CamSA reduces the number of germinating C. difficile spores but does not keep all of the spores from germinating. Vancomycin halts division of any vegetative cells that are able to grow from spores that escape CamSA.

DNA replication proteins as potential targets for antimicrobials in drug-resistant bacterial pathogens

With the impending crisis of antimicrobial resistance, there is an urgent need to develop novel antimicrobials to combat difficult infections and MDR pathogenic microorganisms. DNA replication is essential for cell viability and is therefore an attractive target for antimicrobials. Although several antimicrobials targeting DNA replication proteins have been developed to date, gyrase/topoisomerase inhibitors are the only class widely used in the clinic. Given the numerous essential proteins in the bacterial replisome that may serve as a potential target for inhibitors and the relative paucity of suitable compounds, it is evident that antimicrobials targeting the replisome are underdeveloped so far. In this review, we report on the diversity of antimicrobial compounds targeting DNA replication and highlight some of the challenges in developing new drugs that target this process.

A Review of Experimental and Off-Label Therapies for Clostridium difficile Infection

In spite of increased awareness and the efforts taken to optimize Clostridium difficile infection (CDI) management, with the limited number of currently available antibiotics for C. difficile the halt of this increasing epidemic remains out of reach. There are, however, close to 80 alternative treatment methods with controversial anti-clostridial efficacy or in experimental phase today. Indeed, some of these therapies are expected to become acknowledged members of the recommended anti-CDI arsenal within the next few years. None of these alternative treatment methods can respond in itself to all the major challenges of CDI management, which are primary prophylaxis in the susceptible population, clinical cure of severe cases, prevention of recurrences, and forestallment of asymptomatic C. difficile carriage and in-hospital spread. Yet, the greater the variety of treatment choices on hand, the better combination strategies can be developed to reach these goals in the future. The aim of this article is to provide a comprehensive summary of these experimental and currently off-label therapeutic options.

Intravenous adenovirus expressing a multi-specific, single-domain antibody neutralizing TcdA and TcdB protects mice from Clostridium difficile infection

Clostridium difficile infection (CDI) is the most common cause of antibiotic-associated diarrhea and colitis in developed countries. The disease is mainly mediated via two major exotoxins TcdA and TcdB secreted by the bacterium. We have previously developed a novel, potently neutralizing, tetravalent and bispecific heavy-chain-only single domain (VHH) antibody to both TcdA and TcdB (designated as ABA) that reverses fulminant CDI in mice. Since ABA has a short serum half-life, in this study a replication-deficient recombinant adenovirus expressing ABA was generated and the long-lasting expression of functional ABA was demonstrated in vitro and in vivo Mice transduced with one dose of the adenovirus displayed high levels of serum ABA for more than1 month and were fully protected against systemic toxin challenges. More importantly, the ABA delivered by the adenovirus protected mice from both primary and recurrent CDI. Thus, replication-deficient adenoviral vector may be used to deliver neutralizing antibodies against the toxins in order to prevent CDI and recurrence.

One for All? Hitting Multiple Alzheimer's Disease Targets with One Drug

HIGHLIGHTS Many AD target combinations are being explored for multi-target drug design.New databases and models increase the potential of computational drug designLiraglutide and other antidiabetics are strong candidates for repurposing to AD.Donecopride a dual 5-HT/AChE inhibitor shows promise in pre-clinical studies Alzheimer's Disease is a complex and multifactorial disease for which the mechanism is still not fully understood. As new insights into disease progression are discovered, new drugs must be designed to target those aspects of the disease that cause neuronal damage rather than just the symptoms currently addressed by single target drugs. It is becoming possible to target several aspects of the disease pathology at once using multi-target drugs (MTDs). Intended as an introduction for non-experts, this review describes the key MTD design approaches, namely structure-based, in silico, and data-mining, to evaluate what is preventing compounds progressing through the clinic to the market. Repurposing current drugs using their off-target effects reduces the cost of development, time to launch, and the uncertainty associated with safety and pharmacokinetics. The most promising drugs currently being investigated for repurposing to Alzheimer's Disease are rasagiline, originally developed for the treatment of Parkinson's Disease, and liraglutide, an antidiabetic. Rational drug design can combine pharmacophores of multiple drugs, systematically change functional groups, and rank them by virtual screening. Hits confirmed experimentally are rationally modified to generate an effective multi-potent lead compound. Examples from this approach are ASS234 with properties similar to rasagiline, and donecopride, a hybrid of an acetylcholinesterase inhibitor and a 5-HT4 receptor agonist with pro-cognitive effects. Exploiting these interdisciplinary approaches, public-private collaborative lead factories promise faster delivery of new drugs to the clinic.

A novel multivalent, single-domain antibody targeting TcdA and TcdB prevents fulminant Clostridium difficile infection in mice

The incidence of Clostridium difficile infection (CDI) and associated mortality have increased rapidly worldwide in recent years. Therefore, it is critical to develop new therapies for CDI. In this study, we generated a novel, potently neutralizing, tetravalent, and bispecific antibody composed of 2 heavy-chain-only VH (VHH) binding domains against both TcdA and TcdB (designated "ABA") that reverses fulminant CDI in mice infected with an epidemic 027 strain after a single injection of the antibody. We demonstrated that ABA bound to both toxins simultaneously and displayed a significantly enhanced neutralizing activity both in vitro and in vivo. Additionally, ABA was able to broadly neutralize toxins from clinical C. difficile isolates that express both TcdA and TcdB but failed to neutralize the toxin from TcdA(-)TcdB(+) C. difficile strains. This study thus provides a rationale for the development of multivalent VHHs that target both toxins and are broadly neutralizing for treating severe CDI.

Progress in the discovery of treatments for C. difficile infection: A clinical and medicinal chemistry review

Clostridium difficile is an anaerobic, Gram-positive pathogen that causes C. difficile infection, which results in significant morbidity and mortality. The incidence of C. difficile infection in developed countries has become increasingly high due to the emergence of newer epidemic strains, a growing elderly population, extensive use of broad spectrum antibiotics, and limited therapies for this diarrheal disease. Because treatment options currently available for C. difficile infection have some drawbacks, including cost, promotion of resistance, and selectivity problems, new agents are urgently needed to address these challenges. This review article focuses on two parts: the first part summarizes current clinical treatment strategies and agents under clinical development for C. difficile infection; the second part reviews newly reported anti-difficile agents that have been evaluated or reevaluated in the last five years and are in the early stages of drug discovery and development. Antibiotics are divided into natural product inspired and synthetic small molecule compounds that may have the potential to be more efficacious than currently approved treatments. This includes potency, selectivity, reduced cytotoxicity, and novel modes of action to prevent resistance.

Sensitivity to antibiotics of Clostridium difficile toxigenic nosocomial strains

Clostridium difficile is the etiological agent of diarrhoea and colitis, especially in elderly patients. The incidence of these diseases has increased during the last 10 years. Emergence of so-called hypervirulent strains is considered as one of the main factors responsible for the more severe disease and changed profile of sensitivity to antimicrobial agents. The aim of this work was to determine the sensitivity profile of toxigenic strains of C. difficile in the Czech Republic in 2011-2012 to selected antibiotics. The antibiotics clindamycin, metronidazole, vancomycin and amoxicillin with clavulanic acid were used for this purpose. Isolates cultured on Brazier's C. difficile selective agar were analysed for the presence of toxin genes using Xpert detection system. Xpert analysis revealed that 33 strains carried the genes for toxins tcdB, cdt and tcdCΔ117, thus showing characteristics typical for the hypervirulent ribotype 027/PFGE type NAP1/REA type B1. The remaining 29 strains carried only the gene for toxin B (tcdB) and not cdt and tcdCΔ117. Our results indicate the higher susceptibility of C. difficile hypertoxigenic strains to three out of four tested antibiotics (except vancomycin) than it is for the other toxigenic strains. We found that only 10.34% of other toxigenic strains were resistant to clindamycin, and no resistance was found in all other cases. All the isolates were sensitive to amoxicillin/clavulanic acid in vitro. However, its use is not recommended for therapy of infections caused by C. difficile.

MBX-500 is effective for treatment of Clostridium difficile infection in gnotobiotic piglets

The novel antibiotic MBX-500, dosed at 100, 200, or 400 mg/kg twice daily for 7 days, was evaluated for the treatment of Clostridium difficile infection (CDI) in the gnotobiotic pig model. MBX-500 increased survival at all doses and at high doses improved clinical signs and reduced lesion severity, similar to vancomycin. Our results show that MBX-500 is an effective antibiotic for the treatment of diarrhea associated with CDI and prevents severe systemic disease.