Alkyl-guanidine Compounds as Potent Broad-Spectrum Antibacterial Agents: Chemical Library Extension and Biological Characterization

An insight into the last 5-year patents on porphyromonas gingivalis and streptococcus mutans, the pivotal pathogens in the oral cavity

INTRODUCTION

The oral cavity harbors an extensive array of over 700 microorganisms, forming the most complex biome of the entire human body, with bacterial species being the most abundant. Oral diseases, e.g. periodontitis and caries, are strictly associated with bacterial dysbiosis. Porphyromonas gingivalis and Streptococcus mutans stand out among bacteria colonizing the oral cavity.

AREAS COVERED

After a brief overview of the bacterial populations in the oral cavity and their roles in regulating (flora) oral cavity or causing diseases like periodontal and cariogenic pathogens, we focused our attention on P. gingivalis and S. mutans, searching for the last-5-year patents dealing with the proposal of new strategies to fight their infections. Following the PRISMA protocol, we filtered the results and analyzed over 100 applied/granted patents, to provide an in-depth insight into this R&D scenario.

EXPERT OPINION

Several antibacterial proposals have been patented in this period, from both chemical - peptides and small molecules - and biological - probiotics and antibodies - sources, along with natural extracts, polymers, and drug delivery systems. Most of the inventors are from China and Korea and their studies also investigated anti-inflammatory and antioxidant effects, being beneficial to oral health through a prophylactic, protective, or curative effect.

An update on antibacterial AlkylGuanidino Ureas: Design of new derivatives, synergism with colistin and data analysis of the whole library

Antimicrobial resistance (AMR) represents one of the most challenging global Public Health issues, with an alarmingly increasing rate of attributable mortality. This scenario highlights the urgent need for innovative medicinal strategies showing activity on resistant isolates (especially, carbapenem-resistant Gram-negative bacteria, methicillin-resistant S. aureus, and vancomycin-resistant enterococci) yielding new approaches for the treatment of bacterial infections. We previously reported AlkylGuanidino Ureas (AGUs) with broad-spectrum antibacterial activity and a putative membrane-based mechanism of action. Herein, new tetra- and mono-guanidino derivatives were designed and synthesized to expand the structure-activity relationships (SARs) and, thereby, tested on the same panel of Gram-positive and Gram-negative bacteria. The membrane-active mechanism of selected compounds was then investigated through molecular dynamics (MD) on simulated bacterial membranes. In the end, the newly synthesized series, along with the whole library of compounds (more than 70) developed in the last decade, was tested in combination with subinhibitory concentrations of the last resort antibiotic colistin to assess putative synergistic or additive effects. Moreover, all the AGUs were subjected to cheminformatic and machine learning analyses to gain a deeper knowledge of the key features required for bioactivity.

Development of Novel Membrane Disrupting Lipoguanidine Compounds Sensitizing Gram-Negative Bacteria to Antibiotics

A new class of amphiphilic molecules, the lipoguanidines, designed as hybrids of guanidine and fatty acid compounds, has been synthesized and developed. The new molecules present both a guanidine polar head and a lipophilic tail that allow them to disrupt bacterial membranes and to sensitize Gram-negative bacteria to the action of the narrow-spectrum antibiotics rifampicin and novobiocin. The lipoguanidine 5g sensitizes Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli to rifampicin, thereby reducing the antibiotic minimum inhibitory concentrations (MIC) up to 256-fold. Similarly, 5g is able to potentiate novobiocin up to 64-fold, thereby showing a broad spectrum of antibiotic potentiating activity. Toxicity and mechanism studies revealed the potential of 5g to work synergistically with rifampicin through the disruption of bacterial membranes without affecting eukaryotic cells.

Synthesis and antimicrobial properties of guanidine-functionalized labdane type diterpenoids

The occurrence of increased antibiotic resistance has reduced the availability of drugs effective in the control of infectious diseases, especially those caused by various combinations of bacteria and/or fungi that are often associated with poorer patient outcomes. In the hunt for novel antibiotics of interest to treat polymicrobial diseases, molecules bearing guanidine moieties have recently come to the fore in designing and optimizing antimicrobial agents. Due to their remarkable antibacterial and antifungal activities, labdane diterpenes are also attracting increasing interest in antimicrobial drug discovery. In this study, six different guanidines prenylated with labdanic fragments were synthesized and evaluated for their antimicrobial properties. Assays were carried out against both non-resistant and antibiotic-resistant bacteria strains, while their possible antifungal activities have been tested on the yeast Candida albicans. Two of the synthesized compounds, namely labdan-8,13(R)-epoxy-15-oyl guanidine and labdan-8,13(S)-epoxy-15-oyl guanidine, were finally selected as the best candidates for further developments in drug discovery, due to their antimicrobial effects on both Gram-negative and Gram-positive bacterial strains, their fungicide action, and their moderate toxicity in vivo on zebrafish embryos. The study also provides insights into the structure-activity relationships of the guanidine-functionalized labdane-type diterpenoids.

Amidine-Based Cationic Conjugated Oligoelectrolytes with Antimicrobial Activity against Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium that can cause high-morbidity infections. Due to its robust, flexible genome and ability to form biofilms, it can evade and rapidly develop resistance to antibiotics. Cationic conjugated oligoelectrolytes (COEs) have emerged as a promising class of antimicrobials. Herein, we report a series of amidine-containing COEs with high selectivity for bacteria. From this series, we identified 1b as the most active compound against P. aeruginosa (minimum inhibitory concentration (MIC) = 2 μg/mL) with low cytotoxicity (IC50 (HepG2) = 1024 μg/mL). The activity of 1b was not affected by known drug-resistant phenotypes of 100 diverse P. aeruginosa isolates. Moreover, 1b is bactericidal with a low propensity for P. aeruginosa to develop resistance. Furthermore, 1b is also able to inhibit biofilm formation at subinhibitory concentrations and kills P. aeruginosa in established biofilms. The in vivo efficacy of 1b was demonstrated in biofilm-associated murine wound infection models.

Synthetic and natural guanidine derivatives as antitumor and antimicrobial agents: A review

Guanidines are fascinating small nitrogen-rich organic compounds, which have been frequently associated with a wide range of biological activities. This is mainly due to their interesting chemical features. For these reasons, for the past decades, researchers have been synthesizing and evaluating guanidine derivatives. In fact, there are currently on the market several guanidine-bearing drugs. Given the broad panoply of pharmacological activities displayed by guanidine compounds, in this review, we chose to focus on antitumor, antibacterial, antiviral, antifungal, and antiprotozoal activities presented by several natural and synthetic guanidine derivatives, which are undergoing preclinical and clinical studies from January 2010 to January 2023. Moreover, we also present guanidine-containing drugs currently in the market for the treatment of cancer and several infectious diseases. In the preclinical and clinical setting, most of the synthesized and natural guanidine derivatives are being evaluated as antitumor and antibacterial agents. Even though DNA is the most known target of this type of compounds, their cytotoxicity also involves several other different mechanisms, such as interference with bacterial cell membranes, reactive oxygen species (ROS) formation, mitochondrial-mediated apoptosis, mediated-Rac1 inhibition, among others. As for the compounds already used as pharmacological drugs, their main application is in the treatment of different types of cancer, such as breast, lung, prostate, and leukemia. Guanidine-containing drugs are also being used for the treatment of bacterial, antiprotozoal, antiviral infections and, recently, have been proposed for the treatment of COVID-19. To conclude, the guanidine group is a privileged scaffold in drug design. Its remarkable cytotoxic activities, especially in the field of oncology, still make it suitable for a deeper investigation to afford more efficient and target-specific drugs.

Synthesis and Biological Evaluation of Piperazine Hybridized Coumarin Indolylcyanoenones with Antibacterial Potential

A class of piperazine hybridized coumarin indolylcyanoenones was exploited as new structural antibacterial frameworks to combat intractable bacterial resistance. Bioactive assessment discovered that 4-chlorobenzyl derivative 11f showed a prominent inhibition on Pseudomonas aeruginosa ATCC 27853 with a low MIC of 1 μg/mL, which was four-fold more effective than norfloxacin. Importantly, the highly active 11f with inconspicuous hemolysis towards human red blood cells displayed quite low proneness to trigger bacterial resistance. Preliminary explorations on its antibacterial behavior disclosed that 11f possessed the ability to destroy bacterial cell membrane, leading to increased permeability of inner and outer membranes, the depolarization and fracture of membrane, and the effusion of intracellular components. Furthermore, bacterial oxidative stress and metabolic turbulence aroused by 11f also accelerated bacterial apoptosis. In particular, 11f could not only effectively inset into DNA, but also bind with DNA gyrase through forming supramolecular complex, thereby affecting the biological function of DNA. The above findings of new piperazine hybridized coumarin indolylcyanoenones provided an inspired possibility for the treatment of resistant bacterial infections.

Leishmanicidal Activity of Guanidine Derivatives against Leishmania infantum

Leishmaniasis is a neglected tropical infectious disease with thousands of cases annually; it is of great concern to global health, particularly the most severe form, visceral leishmaniasis. Visceral leishmaniasis treatments are minimal and have severe adverse effects. As guanidine-bearing compounds have shown antimicrobial activity, we analyzed the cytotoxic effects of several guanidine-bearing compounds on Leishmania infantum in their promastigote and amastigote forms in vitro, their cytotoxicity in human cells, and their impact on reactive nitrogen species production. LQOFG-2, LQOFG-6, and LQOFG-7 had IC50 values of 12.7, 24.4, and 23.6 µM, respectively, in promastigotes. These compounds exhibited cytotoxicity in axenic amastigotes at 26.1, 21.1, and 18.6 µM, respectively. The compounds showed no apparent cytotoxicity in cells from healthy donors. To identify mechanisms of action, we evaluated cell death processes by annexin V and propidium iodide staining and nitrite production. Guanidine-containing compounds caused a significant percentage of death by apoptosis in amastigotes. Independent of L. infantum infection, LQOFG-7 increased nitrite production in peripheral blood mononuclear cells, which suggests a potential mechanism of action for this compound. Therefore, these data suggest that guanidine derivatives are potential anti-microbial molecules, and further research is needed to fully understand their mechanism of action, especially in anti-leishmanial studies.

The impact of counterions in biological activity: case study of antibacterial alkylguanidino ureas

Abstract

Trifluoroacetic acid (TFA), due to its strong acidity and low boiling point, is extensively used in protecting groups-based synthetic strategies. Indeed, synthetic compounds bearing basic functions, such as amines or guanidines (commonly found in peptido or peptidomimetic derivatives), developed in the frame of drug discovery programmes, are often isolated as trifluoroacetate (TF-Acetate) salts and their biological activity is assessed as such in in vitro, ex vivo, or in vivo experiments. However, the presence of residual amounts of TFA was reported to potentially affect the accuracy and reproducibility of a broad range of cellular assays (e. g. antimicrobial susceptibility testing, and cytotoxicity assays) limiting the further development of these derivatives. Furthermore, the impact of the counterion on biological activity, including TF-Acetate, is still controversial. Herein, we present a focused case study aiming to evaluate the activity of an antibacterial AlkylGuanidino Urea (AGU) compound obtained as TF-Acetate (1a) and hydrochloride (1b) salt forms to highlight the role of counterions in affecting the biological activity. We also prepared and tested the corresponding free base (1c). The exchange of the counterions applied to polyguanidino compounds represents an unexplored and challenging field, which required significant efforts for the successful optimization of reliable methods of preparation, also reported in this work. In the end, the biological evaluation revealed a quite similar biological profile for the salt derivatives 1a and 1b and a lower potency was found for the free base 1c.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11030-022-10505-6.

Development of Dicationic Bisguanidine-Arylfuran Derivatives as Potent Agents against Gram-Negative Bacteria

Antibiotic resistance among bacteria is a growing global challenge. A major reason for this is the limited progress in developing new classes of antibiotics active against Gram-negative bacteria. Here, we investigate the antibacterial activity of a dicationic bisguanidine-arylfuran, originally developed as an antitrypanosomal agent, and new derivatives thereof. The compounds showed good activity (EC₅₀ 2–20 µM) against antibiotic-resistant isolates of the Gram-negative members of the ESKAPE group (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) and Escherichia coli with different antibiotic susceptibility patterns, including ESBL isolates. Cytotoxicity was moderate, and several of the new derivatives were less cytotoxic than the lead molecule, offering better selectivity indices (40–80 for several ESKAPE isolates). The molecular mechanism for the antibacterial activity of these molecules is unknown, but sensitivity profiling against human ESKAPE isolates and E. coli collections with known susceptibility patterns against established antibiotics indicates that it is distinct from lactam and quinolone antibiotics.

Synthesis and Exploitation of the Biological Profile of Novel Guanidino Xylofuranose Derivatives

The synthesis and biological evaluation of novel guanidino sugars as isonucleoside analogs is described. 5-Guanidino xylofuranoses containing 3- O -saturated/unsaturated hydrocarbon or aromatic-containing moieties were accessed from 5-azido xylofuranoses via reduction followed by guanidinylation with N , N '-bis( tert -butoxycarbonyl)- N ''-triflylguanidine. Molecules comprising novel types of isonucleosidic structures including 5-guanidino 3- O -methyl-branched N -benzyltriazole isonucleosides and a guanidinomethyltriazole 3'- O -dodecyl xylofuranos-5'-yl isonucleoside were accessed. The guanidinomethyltriazole derivative and a 3- O -dodecyl ( N -Boc)guanidino xylofuranose were revealed as selective inhibitors of acetylcholinesterase ( K i = 22.87 and 7.49 µM, respectively). The latter also showed moderate antiproliferative effects in chronic myeloid leukemia (K562) and breast cancer (MCF-7) cells. An aminomethyltriazole 5'-isonucleoside was the most potent molecule with low micromolar GI 50 values in both cells (GI 50 = 6.33 μM, 8.45 μM), similar to that of the drug 5-fluorouracil in MCF-7 cells. Moreover, the most bioactive compounds showed low toxicity in human fibroblasts, further indicating their interest as promising lead molecules.

Focused library of phenyl-fused macrocyclic amidinoureas as antifungal agents

The rise of antimicrobial-resistant phenotypes and the spread of the global pandemic of COVID-19 are worsening the outcomes of hospitalized patients for invasive fungal infections. Among them, candidiases are seriously worrying, especially since the currently available drug armamentarium is extremely limited. We recently reported a new class of macrocyclic amidinoureas bearing a guanidino tail as promising antifungal agents. Herein, we present the design and synthesis of a focused library of seven derivatives of macrocyclic amidinoureas, bearing a second phenyl ring fused with the core. Biological activity evaluation shows an interesting antifungal profile for some compounds, resulting to be active on a large panel of Candida spp. and C. neoformans. PAMPA experiments for representative compounds of the series revealed a low passive diffusion, suggesting a membrane-based mechanism of action or the involvement of active transport systems. Also, compounds were found not toxic at high concentrations, as assessed through MTT assays.

Bis-Thiourea Quaternary Ammonium Salts as Potential Agents against Bacterial Strains from Food and Environmental Matrices

In recent years, the phenomenon of antibiotic resistance in hospitals, communities and the environment has increasingly grown, so antibiotic resistance has become an urgent problem that requires a decisive and global intervention. Incorrect/unnecessary use of antibiotics contributes to increase the ability of microorganisms to develop resistance faster and faster. Research efforts must, therefore, be made to ensure a future in which antibiotic drugs will still be useful in combating infectious diseases. The search for new antibacterial compounds is fundamental. In this study, the antimicrobial activity of the compounds was evaluated against selected bacterial strains from food and environmental matrices by using the Agar Well Diffusion Assay. A total of thirty-six Gram-positive and Gram-negative bacteria were employed to determine the action spectrum and the antimicrobial effectiveness of a small series of thiourea derivatives. Results showed that the highest activities were found for compounds 1 and 4. The important role of the alkyl chain length and/or guanidine moiety in the width of action spectrum was evidenced. Further studies will allow evaluating the efficacy of the inhibiting action and the molecular mechanisms underlying this activity in order to identify compounds capable of counteracting the phenomenon of antibiotic resistance and to identify possible future applications of these newly synthesized compounds that have shown a high bactericidal action potential.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Development of a Promising Method for Producing Oligomeric Mixture of Branched Alkylene Guanidines to Improve Substance Quality and Evaluate Their Antiviral Activity against SARS-CoV-2

This paper reports the synthesis of branched alkylene guanidines using microfluidic technologies. We describe the preparation of guanidine derivatives at lower temperatures, and with significantly less time than that required in the previously applicable method. Furthermore, the use of microfluidics allows the attainment of high-purity products with a low residual monomer content, which can expand the range of applications of this class of compounds. For all the samples obtained, the molecular-weight characteristics are calculated, based on which the optimal condensation conditions are established. Additionally, in this work, the antiviral activity of the alkylene guanidine salt against the SARS-CoV-2 virus is confirmed.

Synthesis of antibacterial polyether biguanide curing agent and its cured antibacterial epoxy resin

At present, bacteria continue to threaten human health, and the resistance of bacteria to antibiotics continues to increase, so the development of new antibacterial agents and antibacterial materials is increasingly important to ensure human health. In this paper, three polyether biguanide compounds with high antibacterial properties were synthesized by reacting polyetheramine T403 with o-tolylbiguanide, m-tolylbiguanide and p-tolylbiguanide (o-TTB, m-TTB and p-TTB), respectively. The antimicrobial performance of polyether biguanide against E. coli and S. aureus was evaluated using a minimum inhibitory concentration method, and the results showed that the synthesized polyether biguanide exhibited efficient and broad-spectrum antimicrobial effects. Among them, o-tolyl biguanide derivative o-TTB showed the best antimicrobial performance, with minimum inhibitory concentrations of 20 and 15 μg/mL against E. coli and S. aureus, respectively. Then, epoxy resin E51 was cured using the obtained TTB as a curing agent to prepare an epoxy resin with antibacterial properties. The inhibition of the growth of S. aureus by the cured o-TTB/E51 resin was investigated by incubating the cured epoxy resin with bacteria, and the results showed that the cured resin had a significant inhibitory effect on the growth of bacteria. The non-isothermal curing kinetics of the o-TTB/E51 system were investigated by differential scanning calorimetry (DSC) to determine the optimized curing reaction temperature, curing kinetic parameters and curing kinetics equation.

Antimicrobial drugs bearing guanidine moieties: A review

Compounds incorporating guanidine moieties constitute a versatile class of biologically interesting molecules with a wide array of applications. As such, guanidines have been exploited as privileged structural motifs in designing novel drugs for the treatment of various infectious and non-infectious diseases. In designing anti-infective agents, this moiety carries great appeal by virtue of attributes such as hydrogen-bonding capability and protonatability at physiological pH in the context of interaction with biological targets. This review provides an overview of recent advances in hit-to-lead development studies of antimicrobial guanidine-containing compounds with the aim to highlight their structural diversity and the pharmacological relevance of the moiety to drug activity, insofar as possible. In so doing, emphasis is put on chemical and microbiological properties of such compounds in relation to antibacterial, antifungal and antimalarial activities.

The chemistry and biology of guanidine secondary metabolites

Covering: 2017-2019Guanidine natural products isolated from microorganisms, marine invertebrates and terrestrial plants, amphibians and spiders, represented by non-ribosomal peptides, guanidine-bearing polyketides, alkaloids, terpenoids and shikimic acid derived, are the subject of this review. The topics include the discovery of new metabolites, total synthesis of natural guanidine compounds, biological activity and mechanism-of-action, biosynthesis and ecological functions.

N-Terminal guanidine derivatives of teicoplanin antibiotics strongly active against glycopeptide resistant Enterococcus faecium

Antibiotic resistance is one of the major challenges in healthcare of our time. To meet this challenge, we designed and prepared guanidine and lipophilic guanidine derivatives of the glycopeptide antibiotic teicoplanin to armed them with activity against the most threatening nosocomial bacteria, multiresistant enterococci. From teicoplanin and its pseudoaglycone, a series of N-terminal guanidine derivatives have been prepared with free and amide C-terminal parts. Six aliphatic and aromatic lipophilic carbodiimides were prepared and used for the synthesis of lipophilic guanidine teicoplanin conjugates. All new N-terminal guanidine antibiotics showed high activity against a standard panel of Gram-positive bacteria. Four selected derivatives displayed excellent antibacterial activity against a series of nosocomial VanA Enterococcus faecium strains.

Unexpected Thiocyanate Adsorption onto Ferrihydrite Under Prebiotic Chemistry Conditions

The most crucial role played by minerals was in the preconcentration of biomolecules or precursors of biomolecules in prebiotic seas. If this step had not occurred, molecular evolution would not have occurred. Thiocyanate is an important molecule in the formation of biomolecules as well as a catalyst for prebiotic reactions. The adsorption of thiocyanate onto ferrihydrite was carried out under pH and ion composition conditions in seawater that resembled those of prebiotic Earth. The seawater used in this work had high Mg²⁺, Ca²⁺ and SO₄^2- concentrations. The most important result of this work was that ferrihydrite adsorbed thiocyanateata pH value (7.2 ± 0.2) that usually does not adsorb thiocyanate. The high adsorptivity of Mg²⁺, Ca²⁺ and SO₄^2-onto ferrihydrite showed that seawater ions can act as carriers of thiocyanate to the ferrihydrite surface, creating a huge outer-sphere complex. Kinetic adsorption and isotherm experiments showed the best fit for the pseudo-second-order model and an activation energy of 23.8 kJ mol^-1forthe Langmuir-Freundlich model, respectively. Thermodynamic data showed positive ΔG values, which apparently contradict the adsorption isotherm data and kinetic data that was obtained. The adsorption of thiocyanate onto ferrihydrite could be explained by coupling with the exergonic SO₄^2- adsorption onto ferrihydrite. The FTIR spectra showed no difference between the C≡N stretching peaks of adsorbed thiocyanate and free thiocyanate, corroborating the formation of an outer-sphere complex. All the results demonstrated the importance of the artificial seawater composition for the adsorption of thiocyanate and for understanding prebiotic chemistry.

Design, synthesis and evaluation of dihydrotriazine derivatives-bearing 5-aryloxypyrazole moieties as antibacterial agents

In the present investigation, a series of dihydrotriazine derivatives-bearing 5-aryloxypyrazole moieties were synthesized and their structures were confirmed by different spectral tools. The biological evaluation in vitro revealed that some of the target compounds exerted good antibacterial and antifungal activity in comparison with the reference drugs. Among these novel hybrids, compound 10d showed the most potent activity with minimum inhibitory concentration values (MIC) of 0.5 µg/mL against S. aureus 4220, MRSA 3506 and E. coli 1924 strain. The cytotoxic activity of the compounds 6d, 6m, 10d and 10g was assessed in MCF-7 and HeLa cells. Growth kinetics study showed significant inhibition of bacterial growth when treated with different conc. of 10d. In vitro enzyme study implied that compound 10d exerted its antibacterial activity through DHFR inhibition. Moreover, significant inhibition of biofilm formation was observed in bacterial cells treated with MIC conc. of 10d as visualized by SEM micrographs. Twenty-nine target compounds were designed, synthesized and evaluated in terms of their antibacterial and antifungal activities.

An on-demand nanoplatform for enhanced elimination of drug-resistant bacteria

We establish an “on-demand” nanoplatform based on acid-degradable scaffolds by conjugating glycomimetic-based galactose ligands to target a key lectin on P. aeruginosa and guanidine moieties.

In vitro characterization, ADME analysis, and histological and toxicological evaluation of BM1, a macrocyclic amidinourea active against azole-resistant Candida strains

BACKGROUND

Candida species are one of the most common causes of nosocomial bloodstream infections among the opportunistic fungi. Extensive use of antifungal agents, most of which were launched on the market more than 20 years ago, led to the selection of drug-resistant or even multidrug-resistant fungi. We recently described a novel class of antifungal macrocyclic compounds with an amidinourea moiety that is highly active against azole-resistant Candida strains.

OBJECTIVE

A compound from this family, BM1, was investigated in terms of in vitro activity against various Candida species, including C. auris isolates, interaction with the ABC transporter, CDR6, and in vivo distribution and safety.

METHODS

In vitro assays (CYP inhibition, microsomal stability, permeability, spot assays) were used to collect chemical and biological data; animal models (rat) paired with LC-MS analysis were utilised to evaluate in vivo toxicology, pharmacokinetics, and distribution.

RESULTS

The current research shows BM1 has a low in vivo toxicity profile, affinity for the renal system in rats, and good absorption, distribution, metabolism, and excretion (ADME). BM1 also has potent activity against azole-resistant fungal strains, including C. auris isolates and CDR6-overexpressing strains.

CONCLUSIONS

The results confirmed low minimum inhibitory concentrations (MICs) against several Candida species, including preliminary data vs. C. auris. BM1 has good ADME and biochemical characteristics, is suitable and safe for daily administration and is particularly indicated for renal infections. These data indicate BM1 and its derivatives form a novel, promising antifungal class.

A Guanidine-Based Synthetic Compound Suppresses Angiogenesis via Inhibition of Acid Ceramidase

Angiogenesis generates new blood vessels from pre-existing vessels. Tumors induce the formation of new blood vessels to ensure sufficient oxygen and nutrients for their growth. Normally, angiogenesis is induced by various pro-angiogenesis factors, including vascular endothelial growth factor (VEGF). Inhibition of VEGF is a promising approach to cancer treatment. A guanidine-based synthetic compound, E2, was identified as a potent hit from 68 guanidine-based derivatives by screening for angiogenesis inhibitors showing antiproliferative activity in human umbilical vein endothelial cells (HUVECs). To explore the mode of action of E2, target proteins were investigated using phage display biopanning, and acid ceramidase 1 (ASAH1) was identified as an E2-binding protein. Drug affinity responsive target stability (DARTS) and ASAH1 activity assays revealed the direct binding of E2 to ASAH1. Moreover, siRNA knockdown of ASAH1 demonstrated its role as an angiogenesis factor. Consequently, E2 inhibited chemoinvasion and tube formation of HUVECs in a dose-dependent manner. E2 also potently suppressed neo-vascularization of chorioallantoic membranes in vivo. Collectively, these data suggest that E2 is a novel angiogenesis inhibitor and ASAH1 is proposed to be a new antiangiogenesis target.