A 14-day repeat dose oral gavage range-finding study of a first-in-class CDI investigational antibiotic, in rats
Abstract: Drug resistant bacteria are winning the fight over antibiotics with some bacteria not responding to any antibiotics, threatening modern medicine as we know it. The development of new, effective and safe antibiotics is critical for addressing this issue. Ramizol, a first-in-class styrylbenzene based antibiotic, is an investigational drug indicated for Clostridium difficile infections (CDI). The objective of this range-finding study was to evaluate the potential general toxicity (based on toxicological endpoints selected) and toxicokinetics of Ramizol in male and female rats that may arise from repeated exposure via oral gavage over a test period of at least 14 days at doses of 50 mg/kg, 500 mg/kg and 1500 mg/kg. There were no mortalities in this study and no Ramizol-related clinical observations. Additionally, there were no changes in mean body weight, body weight gain, food consumption or food efficiency for male and female rats attributable to Ramizol administration. The observed pharmacokinetic behavior showed the presence of Ramizol in plasma at 24 hours post-dosing combined with increasing AUC(0–24) values during the course of this study in groups administered 1500 mg/kg/day, which suggests that at least some dosing groups will show accumulation of compound during repeated dose studies. These toxicology results have shown Ramizol is well-tolerated at very high concentrations in rats and support the further drug development of Ramizol as a first-in-class antibiotic for the treatment of CDI.
- ‘A 14-day repeat dose oral gavage range-finding study of a first-in-class CDI investigational antibiotic, in rats’, K. Sibley, J. Chen, L. Koetzner, O. Mendes, A. Kimzey, J. Lansita and R. A. Boulos, Scientific Reports, 2019, 9, Article number: 158.
Comparison of the in vitro antibacterial activity of Ramizol, fidaxomicin, vancomycin and metronidazole against 100 clinical isolates of Clostridium difficile by broth microdilution
Abstract: Antibiotic drug development remains a major challenge with few candidates in clinical development. Ramizol, a first-in-class styrylbenzene antibiotic, is under development for the treatment of Clostridium difficile associated disease. Here, we investigate the in vitro antibacterial activity of Ramizol in comparison to fidaxomicin, vancomycin and metronidazole against 100 clinical isolates of C. difficile by the broth microdilution method. We show there is no apparent impact of ribotype, toxin-production, or resistance to fidaxomicin, vancomycin or metronidazole on the activity of Ramizol. Moreover, we show Ramizol has a narrower MIC range translating to potentially better control over the therapeutic dose. Together, these results support the further development of Ramizol for the treatment of C. difficile associated disease.
- ‘Comparison of the in vitro antibacterial activity of Ramizol, fidaxomicin, vancomycin and metronidazole against 100 clinical isolates of Clostridium difficile by broth microdilution’, C. Wolfe, P. Pagano, C. M. Pillar, D. L. Shinabarger and R. A. Boulos, Diagnostic Microbiology and Infectious Disease, 2018, doi: 10.1016/j.diagmicrobio.2018.06.002.
Ramizol® encapsulation into extended release PLGA micro- and nanoparticle systems for subcutaneous and intramuscular administration: in vitro and in vivo evaluation
Objective: Novel antibiotic Ramizol® is advancing to clinical trials for the treatment of gastrointestinal Clostridium difficile associated disease. Despite this, previous studies have shown a rapid plasma clearance upon intravenous administration and low oral bioavailability indicating pure drug is unsuitable for systemic infection treatment following oral dosing. The current study aims to investigate the development of poly-lactic-(co-glycolic) acid (PLGA) particles to overcome this limitation and increase the systemic half-life following subcutaneous and intramuscular dosing.
Significance: The development of new antibiotic treatments will help in combatting the rising incidence of antimicrobial resistance.
Methods: Ramizol® was encapsulated into PLGA nano and microparticles using nanoprecipitation and emulsification solvent evaporation techniques. Formulations were analyzed for particle size, loading level and encapsulation efficiency as well as in vitro drug release profiles. Final formulation was advanced to in vivo pharmacokinetic studies in Sprague–Dawley rats.
Results: Formulation technique showed major influence on particle size and loading levels with optimal loading of 9.4% and encapsulation efficiency of 92.06%, observed using emulsification solvent evaporation. Differences in formulation technique were also linked with subsequent differences in release profiles. Pharmacokinetic studies in Sprague–Dawley rats confirmed extended absorption and enhanced bioavailability following subcutaneous and intramuscular dosing with up to an 8-fold increase in Tmax and T1/2 when compared to the oral and IV routes.
Conclusions: Subcutaneous and intramuscular dosing of PLGA particles successfully increased systemic half-life and bioavailability of Ramizol®. This formulation will allow further development of Ramizol® for systemic infection eradication.
- ‘Ramizol® encapsulation into extended release PLGA micro- and nanoparticle systems for subcutaneous and intramuscular administration: in vitro and in vivo evaluation‘, L. Wright, S. Rao, N. Thomas, R. A. Boulos and C. A. Prestidge, Drug Developent and Industial Pharmacy, 2018, DOI 10.1080 /03639045.2018.1459676.
Preclinical development of Ramizol, an antibiotic belonging to a new class, for the treatment of Clostridium difficile colitis
Abstract: Antibiotic-resistant bacteria is a major threat to human health and is predicted to become the leading cause of death from disease by 2050. Despite the recent resurgence of research and development in the area, few antibiotics have reached the market, with most of the recently approved antibiotics corresponding to new uses for old antibiotics, or structurally similar derivatives thereof. We have recently reported an in silico approach that led to the design of an entirely new class of antibiotics for the bacteria-specific mechanosensitive ion channel of large conductance: MscL. Here, we present the preclinical development of one such antibiotic, Ramizol, a first generation antibiotic belonging to that class. We present the lack of interaction between Ramizol and other mammalian channels adding credibility to its MscL selectivity. We determine the pharmacokinetic profile in a rat model and show <0.1% of Ramizol is absorbed systemically. We show this non-systemic nature of the antibiotic translates to over 70% survival of hamsters in a Clostridium difficile colitis model. Lastly, initial in vitro data indicate that resistance to Ramizol occurs at a low frequency. In conclusion, we establish the potential of Ramizol as an effective new treatment for C. difficile associated disease.
- ‘Preclinical development of Ramizol, an antibiotic belonging to a new class, for the treatment of Clostridium difficile colitis’, S. Rao, C. A. Prestidge, L. Miesel, D. Sweeney, D. L. Shinabarger, and R. A. Boulos, Journal of Antibiotics, 2016, doi: 10.1038/ja.2016.45.
Zolav®: a new antibiotic for the treatment of acne
Background: Acne is a prominent skin condition affecting >80% of teenagers and young adults and ~650 million people globally. Isotretinoin, a vitamin A derivative, is currently the standard of care for treatment. However, it has a well-established teratogenic activity, a reason for the development of novel and low-risk treatment options for acne.
Objective: To investigate the effectiveness of Zolav®, a novel antibiotic as a treatment for acne vulgaris.
Materials and methods: Minimum inhibitory concentration of Zolav® against Propionibacterium acnes was determined by following a standard protocol using Mueller-Hinton broth and serial dilutions in a 96-well plate. Cytotoxicity effects on human umbilical vein endothelial cells and lung cells in the presence of Zolav® were investigated by determining the growth inhibition (GI50) concentration, total growth inhibition concentration, and the lethal concentration of 50% (LC50). The tryptophan auxotrophic mutant of Escherichia coli strain, WP2 uvrA (ATCC 49979), was used for the AMES assay with the addition of Zolav® tested for its ability to reverse the mutation and induce bacterial growth. The in vivo effectiveness of Zolav® was tested in a P. acnes mouse intradermal model where the skin at the infection site was removed, homogenized, and subjected to colony-forming unit (CFU) counts.
Results: Susceptibility testing of Zolav® against P. acnes showed a minimum inhibitory concentration of 2 µg/mL against three strains with no cytotoxicity and no mutagenicity observed at the highest concentrations tested, 30 µM and 1,500 µg/plate, respectively. The use of Zolav® at a concentration of 50 µg/mL (q8h) elicited a two-log difference in CFU/g between the treatment group and the control.
Conclusion: This study demonstrates the potential of Zolav® as a novel treatment for acne vulgaris.
- ‘Zolav®: a new antibiotic for the treatment of acne’, A. Dinant, and R. A. Boulos, Drug Design, Development and Therapy, 2016, 10, 1235-1242.
A new antibiotic with potent activity targets MscL
Abstract: The growing problem of antibiotic-resistant bacteria is a major threat to human health. Paradoxically, new antibiotic discovery is declining, with most of the recently approved antibiotics corresponding to new uses for old antibiotics or structurally similar derivatives of known antibiotics. We used an in silico approach to design a new class of non-toxic antimicrobials for the bacteria-sepcific mechanosensitive ion channel of large conductance, MscL. One antimicrobial of this class, compound 10, is effective against methicillin-resistant Staphylococcus aureus with no cytotoxicity in human cell lines at the therapeutic concentrations. As predicted from in silico modelling, we show that the mechanism of action of compound 10 is at least partly dependent on interactions with MscL. Moreover we show that compound 10 cured a methicillin-resistant Staphylococcus aureus infection in the model nematode Caenorhabditis elegans. Our work shows that compound 10, and other drugs that target MscL, are potentially important therapeutics against antibiotic-resistant bacterial infections.
- ‘A new antibiotic with potent activity targets MscL’, I. Iscla, R. Wray, P. Blount, J. Larkins-Ford, A. L. Conery, F. M. Ausubel, S. Ramu, A. Kavanagh, J. X. Huang, M. A. Blaskovich, M. A. Cooper, A. Obregon-Henao, I. Orme, E. S. Tjandra, U. H. Stroeher, M. H. Brown, C. Macardle, N. van Holst, C. L. Tong, A. D. Slattery, C. T. Gibson, C. L. Raston, and R. A. Boulos, Journal of Antibiotics, 2015, 68, 453-462.
Aqueous based synthesis of antimicrobial-decorated graphene
Abstract: Ramizol® (1,3,5-tris[(1E)-2’-(4’-benzoic acid)vinyl]benzene) is a potent amphiphilic anti-microbial agent. It is essentially a planar molecule and can interact with the surface of graphene via extended π-π interactions. Herein we demonstrate the utility of Ramizol® in potentially acting as a molecular ‘wedge’ to exfoliate graphene and stabilize it in water. The non-covalent attachment of Ramizol® on the graphene surface enables release of Ramizol® by altering the pH of the solution. Furthermore, the stabilized composite material demonstrates antibacterial activity against Staphylococcus aureus which leads to potential in biomedical applications with graphene acting as a drug carrier as well as enhancing the structural strength of the composite material.
- ‘Aqueous based synthesis of antimicrobial-decorated graphene’, M. H. Wahid, U. Stroeher, E. Eroglu, X. Chen, K. Vimalanathan, C. L. Raston, and R. A. Boulos, Journal of Colloid and Interface Science, 2015, 443, 88-96.
Inspiration from old dyes: New tris-stilbene compounds as potent Gram-positive anti-bacterial agents
Abstract: Herein we describe the preparation and structure-activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin-resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12-0.25 μg/mL and against Staphylococcus spp. with MICs ranging from 2-4 μg/mL. The derivative 17 showed increased activity with MICs of 0.06-0.25 μg/mL against M. catarrhalis and 0.12 μg/mL against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 μg/mL and clindamycin with MICs of ≤0.5 μg/mL. As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development.
- ‘Inspiration from old dyes: New tris-stilbene compounds as potent Gram-positive anti-bacterial agents’, R. A. Boulos, N. Y. T. Man, N. A. Lengkeek, K. A. Hammer, N. F. Foster, N. A. Stemberger, B. W. Skelton, P. Y. Wong, B. Martinac, T. V. Riley, A. J. McKinley, and S. G. Stewart, Chemistry European Journal, 2013, 19, 17980–17988.
A novel antimicrobial agent reduces oxidative stress in cells
Abstract: 1,3,5-Tris[(1E)-2′-(4′′-benzoic acid)vinyl]benzene] (Ramizol™) is a potent and non-toxic synthetic antimicrobial agent, and we now establish that it is also a potent inhibitor of reactive oxygen species (ROS) generation, with similar antioxidant activity to α-tocopherol (Vitamin E), which is a standard antioxidant drug. The results show that Ramizol™ decreases ROS to basal levels in PC12 cells and mouse and guinea pig myocytes, and demonstrate its protective nature from oxidative damage to the cells. The continuing challenge to discover antibiotics with no or few side effects makes Ramizol™ a very attractive candidate for the potential treatment of infections.
- ‘A novel antimicrobial agent reduces oxidative stress in cells’, E. James, H. Viola, L. Hool, P. K. Eggers, C. L. Raston and R. A. Boulos, RSC Advances, 2013, 3, 7277–7281.
The synthesis of fluorescent DNA intercalator precursors through efficient multiple heck reactions
Abstract: A highly efficient synthesis of p-carboethoxy-tristyryl and carboethoxy-terastyrenyl benzene derivatives through a multiple Heck cross coupling reaction is reported. This reaction provides an efficient route to DNA intercalator precursors containing a benzene core.
- ‘The synthesis of fluorescent DNA intercalator precursors through efficient multiple heck reactions’, N. A. Lengkeek, R. A. Boulos, A. J. McKinley, T. V. Riley, B. Martinac and S. G. Stewart, Australian Journal of Chemistry, 2011, 64, 316-323.