Assessment of the In Vivo Activity of SPR741 in Combination with Azithromycin against Multidrug-Resistant Enterobacteriaceae Isolates in the Neutropenic Murine Thigh Infection Model.

SPR741 is a novel agent with structural similarity to polymyxins that is capable of potentiating the activities of various classes of antibiotics. Previously published studies indicated that although Enterobacteriaceae isolates had minimal susceptibilities to azithromycin (AZM), the in vitro antimicrobial activity of AZM against Enterobacteriaceae was enhanced when it was combined with SPR741. The current study evaluated the in vivo activity of human-simulated regimens (HSR) of AZM equivalent to clinical doses of 500 mg given intravenously (i.v.) every 24 h (q24h) and SPR741 equivalent to clinical doses of 400 mg q8h i.v. (1-h infusion), alone and in combination, against multidrug-resistant (MDR) Enterobacteriaceae We studied 30 MDR Enterobacteriaceae isolates expressing a wide spectrum of ß-lactamases (ESBL, NDM, VIM, and KPC), including a subset of isolates positive for genes conferring macrolide resistance (mphA, mphE, ermB, and msr). In vivo activity was assessed as the change in log10 CFU per thigh at 24 h compared with 0 h. Treatment with AZM alone was associated with net growth of 2.60 ± 0.83 log10 CFU/thigh. Among isolates with AZM MICs of ≤16 mg/liter, treatment with AZM-SPR741was associated with an average reduction in bacterial burden of -0.53 ± 0.82 log10 CFU/thigh, and stasis to 1-log kill was observed in 9/11 isolates (81.8%). Combination therapy with an AZM-SPR741 HSR showed promising in vivo activity against MDR Enterobacteriaceae isolates with AZM MICs of ≤16 mg/liter, including those producing a variety of ß-lactamases. These data support a potential role for AZM-SPR741 in the treatment of infections due to MDR Enterobacteriaceae.

Combating multidrug-resistant Gram-negative bacteria with structurally nanoengineered antimicrobial peptide polymers.

With the recent emergence of reports on resistant Gram-negative 'superbugs', infections caused by multidrug-resistant (MDR) Gram-negative bacteria have been named as one of the most urgent global health threats due to the lack of effective and biocompatible drugs. Here, we show that a class of antimicrobial agents, termed 'structurally nanoengineered antimicrobial peptide polymers' (SNAPPs) exhibit sub-µM activity against all Gram-negative bacteria tested, including ESKAPE and colistin-resistant and MDR (CMDR) pathogens, while demonstrating low toxicity. SNAPPs are highly effective in combating CMDR Acinetobacter baumannii infections in vivo, the first example of a synthetic antimicrobial polymer with CMDR Gram-negative pathogen efficacy. Furthermore, we did not observe any resistance acquisition by A. baumannii (including the CMDR strain) to SNAPPs. Comprehensive analyses using a range of microscopy and (bio)assay techniques revealed that the antimicrobial activity of SNAPPs proceeds via a multimodal mechanism of bacterial cell death by outer membrane destabilization, unregulated ion movement across the cytoplasmic membrane and induction of the apoptotic-like death pathway, possibly accounting for why we did not observe resistance to SNAPPs in CMDR bacteria. Overall, SNAPPs show great promise as low-cost and effective antimicrobial agents and may represent a weapon in combating the growing threat of MDR Gram-negative bacteria.

Peptide Therapeutics and the Pharmaceutical Industry: Barriers Encountered Translating from the Laboratory to Patients.

Peptides are receiving increasing interest as clinical therapeutics. These highly tunable molecules can be tailored to achieve desirable biocompatibility and biodegradability with simultaneously selective and potent therapeutic effects. Despite challenges regarding up-scaling and licensing of peptide products, their vast clinical potential is reflected in the 60 plus peptide-based therapeutics already on the market, and the further 500 derivatives currently in developmental stages. Peptides are proving effective for a multitude of disease states including: type 2 diabetes (controlled using the licensed glucagon-like peptide-1 receptor liraglutide); irritable bowel syndrome managed with linaclotide (currently at approval stages); acromegaly (treated with octapeptide somatostatin analogues lanreotide and octreotide); selective or broad spectrum microbicidal agents such as the Gram-positive selective PTP-7 and antifungal heliomicin; anticancer agents including goserelin used as either adjuvant or monotherapy for prostate and breast cancer, and the first marketed peptide derived vaccine against prostate cancer, sipuleucel-T. Research is also focusing on improving the biostability of peptides. This is achieved through a number of mechanisms ranging from replacement of naturally occurring L-amino acid enantiomers with D-amino acid forms, lipidation, peptidomimetics, N-methylation, cyclization and exploitation of carrier systems. The development of self-assembling peptides are paving the way for sustained release peptide formulations and already two such licensed examples exist, lanreotide and octreotide. The versatility and tunability of peptide-based products is resulting in increased translation of peptide therapies, however significant challenges remain with regard to their wider implementation. This review highlights some of the notable peptide therapeutics discovered to date and the difficulties encountered by the pharmaceutical industry in translating these molecules to the clinical setting for patient benefit, providing some possible solutions to the most challenging barriers.

Antimicrobial γ-AApeptides (WO2013112548): a patent evaluation.

The patent application WO2013112548 claims a new class of peptidomimetics - γ-AApeptides with potent and broad-spectrum antimicrobial activity. These γ-AApeptides are active against both Gram-positive and Gram-negative bacteria, including medicinally relevant drug-resistant pathogens. They are believed to exert bactericidal function by mimicking the membrane disruption mechanism of host-defense peptides. As such, they may provide an alternative approach for antimicrobial development combating antibiotic resistance.

Antimicrobial peptides: therapeutic potentials.

The increasing appearance of multidrug-resistant pathogens has created an urgent need for suitable alternatives to current antibiotics. Antimicrobial peptides (AMPs), which act as defensive weapons against microbes, have received great attention because of broad-spectrum activities, unique action mechanisms and rare antibiotic-resistant variants. Despite desirable characteristics, they have shown limitations in pharmaceutical development due to toxicity, stability and manufacturing costs. Because of these drawbacks, only a few AMPs have been tested in Phase III clinical trials and no AMPs have been approved by the US FDA yet. However, these obstacles could be overcome by well-known methods such as changing physicochemical characteristics and introducing nonnatural amino acids, acetylation or amidation, as well as modern techniques like molecular targeted AMPs, liposomal formulations and drug delivery systems. Thus, the current challenge in this field is to develop therapeutic AMPs at a reasonable cost as well as to overcome the limitations.

Immunotherapy for pulmonary TB: antimicrobial peptides and their inducers.

TB is an infectious disease that still has an enormous impact on public health worldwide. With the continuous increasing epidemic of multidrug-resistant TB, new drugs and vaccines are urgently needed. In the last decade there has been a broad advance in the knowledge of innate immunity in TB. Together with the growing research regarding immunomodulators, new promising insights have been developed that can contribute in the control of TB. This is the case of antimicrobial peptides, which can be potential therapeutic or adjuvant agents. The current high cost of antimicrobial peptide synthesis may be a current deterrent for treatment; antimicrobial peptide-inducers can be an alternative for low-cost treatment and/or adjuvants.

Assessment of antimicrobial peptide LL-37 as a post-exposure therapy to protect against respiratory tularemia in mice.

Early activation of the innate immune response is important for protection against infection with Francisella tularensis live vaccine strain (LVS) in mice. The human cathelicidin antimicrobial peptide LL-37 is known to have immunomodulatory properties, and therefore exogenously administered LL-37 may be suitable as an early post-exposure therapy to protect against LVS infection. LL-37 has been evaluated for immunostimulatory activity in uninfected mice and for activity against LVS in macrophage assays and protective efficacy when administered post-challenge in a mouse model of respiratory tularemia. Increased levels of pro-inflammatory cytokine IL-6, chemokines monocyte chemoattractant protein 1 (MCP-1) and CXCL1 with increased neutrophil influx into the lungs were observed in uninfected mice after intranasal administration of LL-37. Following LVS challenge, LL-37 administration resulted in increased IL-6, IL-12 p70, IFNγ and MCP-1 production, a slowing of LVS growth in the lung, and a significant extension of mean time to death compared to control mice. However, protection was transient, with the LL-37 treated mice eventually succumbing to infection. As this short course of nasally delivered LL-37 was moderately effective at overcoming the immunosuppressive effects of LVS infection this suggests that a more sustained treatment regimen may be an effective therapy against this pathogen.

A series of systematic reviews to inform a decision analysis for sampling and treating infected diabetic foot ulcers.

OBJECTIVES: To review systematically the evidence on the performance of diagnostic tests used to identify infection in diabetic foot ulcers (DFUs) and of interventions to treat infected DFUs. To use estimates derived from the systematic reviews to create a decision analytic model in order to identify the most effective method of diagnosing and treating infection and to identify areas of research that would lead to large reductions in clinical uncertainty. DATA SOURCES: Electronic databases covering period from inception of the database to November 2002. REVIEW METHODS: Selected studies were assessed against validated criteria and described in a narrative review. The structure of a decision analytic model was derived for two groups of patients in whom diagnostic tests were likely to be used. RESULTS: Three studies that investigated the performance of diagnostic tests for infection on populations including people with DFUs found that there was no evidence that single items on a clinical examination checklist were reliable in identifying infection in DFUs, that wound swabs perform poorly against wound biopsies, and that semi-quantitative analysis of wound swabs may be a useful alternative to quantitative analysis. However, few people with DFUs were included, so it was not possible to tell whether diagnostic performance differs for DFUs relative to wounds of other aetiologies. Twenty-three studies investigated the effectiveness (n = 23) or cost-effectiveness (n = 2) of antimicrobial agents for DFUs. Eight studied intravenous antibiotics, five oral antibiotics, four different topical agents such as dressings, four subcutaneous granulocyte colony stimulating factor (G-CSF), one evaluated oral and topical Ayurvedic preparations and one compared topical sugar versus antibiotics versus standard care. The majority of trials were underpowered and were too dissimilar to be pooled. There was no strong evidence for recommending any particular antimicrobial agent for the prevention of amputation, resolution of infection or ulcer healing. Topical pexiganan cream may be as effective as oral antibiotic treatment with ofloxacin for the resolution of local infection. Ampicillin and sulbactam were less costly than imipenem and cilastatin, a growth factor (G-CSF) was less costly than standard care and cadexomer iodine dressings may be less costly than daily dressings. A decision analytic model was derived for two groups of people, those for whom diagnostic testing would inform treatment--people with ulcers which do not appear infected but whose ulcer is not progressing despite optimal concurrent treatment--and those in whom a first course of antibiotics (prescribed empirically) have failed. There was insufficient information from the systematic reviews or interviews with experts to populate the model with transition probabilities for the sensitivity and specificity of diagnosis of infection in DFUs. Similarly, there was insufficient information on the probabilities of healing, amputation or death in the intervention studies for the two populations of interest. Therefore, we were unable to run the model to inform the most effective diagnostic and treatment strategy. CONCLUSIONS: The available evidence is too weak to be able to draw reliable implications for practice. This means that, in terms of diagnosis, infection in DFUs cannot be reliably identified using clinical assessment. This has implications for determining which patients need formal diagnostic testing for infection, on whether empirical treatment with antibiotics (before the results of diagnostic tests are available) leads to better outcomes, and on identifying the optimal methods of diagnostic testing. With respect to treatment, it is not known whether treatment with systemic or local antibiotics leads to better outcomes or whether any particular agent is more effective. Limited evidence suggests that both G-CSF and cadexomer iodine dressings may be less expensive than 'standard' care, that ampicillin/sulbactam may be less costly than imipenem/cilastatin, and that an unlicensed cream (pexiganan) may be as effective as oral ofloxacin. Further research is needed to ascertain the characteristics of infection in people with DFUs that influence healing and amputation outcomes, to determine whether detecting infection prior to treatment offers any benefit over empirical therapy, and to establish the most effective and cost-effective methods for detecting infection, as well as the relative effectiveness and cost-effectiveness of antimicrobial interventions for DFU infection.

Are antimicrobial peptides an alternative for conventional antibiotics?

Antimicrobial peptides are widespread in living organisms and constitute an important component of innate immunity to microbial infections. By the early 1980s, more than 800 different antimicrobial peptides had been isolated from mammals, amphibians, fish, insects, plants and bacterial species. In humans, they are produced by granulocytes, macrophages and most epithelial and endothelial cells. Newly discovered antibiotics have antibacterial, antifungal, antiviral and even antiprotozoal activity. Occasionally, a single antibiotic may have a very wide spectrum of activity and may show activity towards various kinds of microorganisms. Although antimicrobial activity is the most typical function of peptides, they are also characterized by numerous other properties. They stimulate the immune system, have anti-neoplastic properties and participate in cell signalling and proliferation regulation. As antimicrobial peptides from higher eukaryotes differ structurally from conventional antibiotics produced by bacteria and fungi, they offer novel templates for pharmaceutical compounds, which could be used effectively against the increasing number of resistant microbes.

Recombinant antimicrobial peptides efficiently produced using novel cloning and purification processes.

Endogenous antimicrobial peptides are ubiquitous components of animal and plant host defences. These peptides, usually cationic and amphipathic, kill target cells rapidly and are efficacious against antibiotic-resistant and clinically relevant pathogens. A practical challenge in the development of cationic peptides as therapeutics is to meet the production requirements for large quantities of highly purified drug substance at competitive costs. While chemical peptide synthesis can be used to manufacture cationic peptides, we have developed cost-effective methods for recombinant production by expressing fusion proteins comprised of multiple copies of the peptides. The fusion proteins accumulate in Escherichia coli inclusion bodies and constitute over 50% of the total cellular proteins. Active antimicrobial peptides are released by chemical reagents and purified by chromatography, combining both standard and novel approaches. Challenges of industrial-scale manufacturing of therapeutics were considered in the development of this process.

Cationic antimicrobial peptides - an update.

Cationic antimicrobial peptides play a very important role in nature as a first line of defence against attack and damage. However, their application to the clinic has not been very encouraging to date. There are indications that the barriers to their success may now be eroding with companies developing peptides to be more stable, cost effective and targeted to specific indications. These include systemic infectious disease, acne, vaginitis, wound infection and inflammation. In addition, the use of such peptides as modulators of innate immunity in the treatment of infectious disease and inflammation has added a further dimension to the field.