A Single-Center Retrospective Analysis of Periprocedural Variables Affecting Local Tumor Progression after Radiofrequency Ablation of Colorectal Cancer Liver Metastases.

Background Local tumor progression (LTP) is associated with poorer survival in patients undergoing radiofrequency ablation (RFA) for colorectal liver metastasis (CLM). An algorithmic strategy to predict LTP may help in selection of patients who would benefit most from RFA for CLM. Purpose To estimate local tumor progression-free survival (LTPFS) following RFA of CLM and develop an algorithmic strategy based on clinical variables. Materials and Methods In this retrospective study, between March 2000 and December 2014, patients who underwent percutaneous RFA for CLM were randomly split into development (60%) and internal validation (40%) data sets. Kaplan-Meier method was used to estimate LTPFS and overall survival (OS) rates. Independent factors affecting LTPFS in the development data set were investigated by using multivariable Cox proportional hazard regression analysis. Risk scores were assigned to the risk factors and applied to the validation data set. Results A total of 365 patients (mean age, 60 years ± 11 [standard deviation]; 259 men) with 512 CLMs were evaluated. LTPFS and OS rates were 85% and 92% at 1 year, 73% and 41% at 5 years, 72% and 30% at 10 years, and 72% and 28% at 15 years, respectively. Independent risk factors for LTP included tumor size of 2 cm or greater (hazard ratio [HR], 3.8; 95% CI: 2.3, 6.2; P < .001), subcapsular tumor location (HR, 1.9; 95% CI: 1.1, 3.1; P = .02), and minimal ablative margin of 5 mm or less (HR, 11.7; 95% CI: 4.7, 29.2; P < .001). A prediction model that used the risk factors had areas under the curve of 0.89, 0.92, and 0.90 at 1, 5, and 10 years, respectively, and it showed significantly better areas under the curve when compared with the model using the minimal ablative margin of 5 mm or less alone. Conclusion Radiofrequency ablation provided long-term control of colorectal liver metastases. Although minimal ablative margin of 5 mm or less was the most dominant factor, the multifactorial approach including tumor size and subcapsular location better predicted local tumor progression-free survival. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Soulen and Sofocleous in this issue.

Discovery of Oxazol-2-amine Derivatives as Potent Novel FLT3 Inhibitors.

Internal tandem duplication (ITD) of FMS-like tyrosine kinase 3 (FLT3) is the most common mutation in patients with acute myeloid leukemia (AML). FLT3-ITD+ induces constitutive activation of FLT3, causing an abnormally rapid proliferation of cancer cells. In this study, we identified novel FLT3 inhibitors and investigated 5-(4-fluorophenyl)-N-phenyloxazol-2-amine (compound 7; 7c) as candidates for the treatment of AML. The results showed that 7c inhibited the activities of FLT3 and mutated FLT3 in a cell-free kinase assay and Molm-13 and MV4-11 cells, as well as the proliferation of FLT3-ITD+ AML cells, increasing apoptosis. The anti-leukemic activity of 7c was confirmed by in vivo tumor growth inhibition in MV4-11 xenograft mice. Besides, 7c suppressed the expression of DNA damage repair genes. Combination treatment with 7c and olaparib (a poly (ADP-ribose) polymerase [PARP] inhibitor) synergistically inhibited cell proliferation in Molm-13 and MV4-11 cells. Our findings demonstrated that 7c is a therapeutic candidate targeting FLT3 for AML treatment and suggested that combination treatment with 7c and a PARP inhibitor may be an effective therapy regimen for FLT3-mutated AML.

A Small Compound KJ-28d Enhances the Sensitivity of Non-Small Cell Lung Cancer to Radio- and Chemotherapy.

We previously reported on a poly (ADP-ribose) polymerase (PARP) 1/2 inhibitor N-(3-(hydroxycarbamoyl)phenyl)carboxamide (designated KJ-28d), which increased the death of human ovarian cancer BRCA1-deficient SNU-251 cells. In the present study, we further investigated the antitumor activities of KJ-28d in BRCA-proficient non-small cell lung cancer (NSCLC) cells to expand the use of PARP inhibitors. KJ-28d significantly inhibited the growth of NSCLC cells in vitro and in vivo, and induced DNA damage and reactive oxygen species in A549 and H1299 cells. Combined treatment with KJ-28d and ionizing radiation led to increased DNA damage responses in A549 and H1299 cells compared to KJ-28d or ionizing radiation alone, resulting in apoptotic cell death. Moreover, the combination of KJ-28d plus a DNA-damaging therapeutic agent (carboplatin, cisplatin, paclitaxel, or doxorubicin) synergistically inhibited cell proliferation, compared to either drug alone. Taken together, the findings demonstrate the potential of KJ-28d as an effective anti-cancer therapeutic agent for BRCA-deficient and -proficient cancer cells. KJ-28d might have potential as an adjuvant when used in combination with radiotherapy or DNA-damaging agents, pending further investigations.

Antitumor Activity of a Novel Tyrosine Kinase Inhibitor AIU2001 Due to Abrogation of the DNA Damage Repair in Non-Small Cell Lung Cancer Cells.

Class III receptor tyrosine kinase (RTK) inhibitors targeting mainly FLT3 or c-KIT have not been well studied in lung cancer. To identify a small molecule potentially targeting class III RTK, we synthesized novel small molecule compounds and identified 5-(4-bromophenyl)-N-(naphthalen-1-yl) oxazol-2-amine (AIU2001) as a novel class III RKT inhibitor. In an in vitro kinase profiling assay, AIU2001 inhibited the activities of FLT3, mutated FLT3, FLT4, and c-KIT of class III RTK, and the proliferation of NSCLC cells in vitro and in vivo. AIU2001 induced DNA damage, reactive oxygen species (ROS) generation, and cell cycle arrest in the G2/M phase. Furthermore, AIU2001 suppressed the DNA damage repair genes, resulting in the 'BRCAness'/'DNA-PKness' phenotype. The mRNA expression level of STAT5 was downregulated by AIU2001 treatment and knockdown of STAT5 inhibited the DNA repair genes. Our results show that compared to either drug alone, the combination of AIU2001 with a poly (ADP-ribose) polymerase (PARP) inhibitor olaparib or irradiation showed synergistic efficacy in H1299 and A549 cells. Hence, our findings demonstrate that AIU2001 is a candidate therapeutic agent for NSCLC and combination therapies with AIU2001 and a PARP inhibitor or radiotherapy may be used to increase the therapeutic efficacy of AIU2001 due to inhibition of DNA damage repair.

Validated high-performance liquid chromatography method for the determination of the inhibitor of cancer cell invasion (E)-N-benzyl-6-[2-(3, 4-dihydroxy benzylidene)hydrazinyl]-N-methylpyridine-3-sulfonamide in rat plasma and its application to pharmacokinetic study.

In this study, a reliable method for the quantitation of (E)-N-benzyl-6-[2-(3, 4-dihydroxy benzylidene)hydrazinyl]-N-methylpyridine-3-sulfonamide (JW-55) in rat plasma was developed and validated using high-performance liquid chromatography. Plasma samples were deproteinized; sildenafil was used as an internal standard. Chromatographic separation was achieved using a reversed-phase C18 column. The mobile phase, 0.02 m ammonium acetate buffer:acetonitrile (48:52, v/v), was run at a flow rate of 1.0 mL/min at room temperature, and the column eluent was monitored using an ultraviolet detector at 280 nm. The retention times of JW-55 and sildenafil were ~5.9 and 7.7 min, respectively. The detection limit of JW-55 in rat plasma was 0.03 µg/mL. Pharmacokinetic parameters of JW-55 were evaluated after intravenous and oral administration of JW-55 (10 mg/kg) in rats. After oral administration, the F value was approximately 73.7%.

Inhibition of cancer cell invasion by new ((3,4-dihydroxy benzylidene)hydrazinyl)pyridine-3-sulfonamide analogs.

Rab GTPases regulate various types of intracellular membrane trafficking in all eukaryotes. Since Rab27a and its multiple effectors are involved in exocytosis of lysosome-related organelles and play a major role in malignancy, compounds targeting Rab27a could be likely used to inhibit invasive growth and tumor metastasis. Thus, we designed and synthesized several compounds based on the previously reported Rab27a-targeting synthetic compounds identified by virtual screening, and investigated their anti-metastatic effects in MDA-MB231 and A375 cells. Among the synthesized compounds, (E)-N-(3-chlorophenyl)-6-(2-(3,4-dihydroxy benzylidene)hydrazinyl)pyridine-3-sulfonamide (3d) and (E)-N-benzyl-6-(2-(3,4-dihydroxy benzylidene)hydrazinyl)-N-methylpyridine-3-sulfonamide (3f) significantly inhibited the invasiveness of both tumor cell lines. Compounds 3d and 3f also decreased the levels of signature extracellular matrix marker proteins (fibronectin, collagen, and α-smooth muscle actin) and representative mesenchymal cell markers (N-cadherin and vimentin). Taken together, our results suggest that novel sulfonamide analogs have anti-metastatic activity in breast and melanoma cancer cell lines and may be used as therapeutic agents to treat malignant cancer.

Transarterial chemoembolization vs. radiofrequency ablation for the treatment of single hepatocellular carcinoma 2 cm or smaller.

OBJECTIVES: To compare the effectiveness of transarterial chemoembolization (TACE) and radiofrequency ablation (RFA) for treating small (≤2 cm) hepatocellular carcinomas (HCCs). METHODS: This retrospective study consisted of 287 patients (mean age, 57.1 years; age range, 29-84 years; 221 men, 66 women; 73.5% with HBV; 100% with liver cirrhosis) with Barcelona Clinic Liver Cancer very early-stage HCC (≤2 cm single HCC) who were initially treated with TACE (n=122) or RFA (n=165). The primary study end point was overall patient survival. Secondary study end points were time to progression and tumor response. RESULTS: The RFA and TACE groups were well balanced in terms of baseline variables. The two groups did not differ significantly in overall survival (P=0.079) or major complication (P>0.999) rates. The respective cumulative survival rates at 1, 3, 5, and 8 years were 97.6, 86.7, 74.5, and 60.0% for RFA and 93.4, 75.4, 63.1, and 51.1% for TACE. Their objective tumor regression (complete or partial response) rates were 100% (165/165) and 95.9% (117/122), respectively (P=0.013). The median times to progression for RFA and TACE were 27.0±3.8 (95% confidence intervals (CIs): 19.6-34.4) and 18.0±2.9 (95% CIs: 12.2-23.8) months, respectively. RFA yielded a significantly longer time to progression (P=0.034). CONCLUSIONS: TACE may be a viable alternative treatment for ≤2 cm HCCs when RFA is not feasible.

Real-time Visualization of Transcribed mRNA via Click Chemistry in a Liposomal Space.

We present a CuAAC (Copper-Catalyzed Azide-Alkyne Cycloaddition) reaction protocol designed for the visualization of mRNA. To achieve this, we synthesized stable mRNA molecules incorporating the modified nucleoside analog, EU, a crucial element for fluorophore attachment. Leveraging this modified mRNA, we successfully executed the CuAAC reaction, wherein the pro-fluorophore, coumarin, was conjugated to EU on the mRNA through our meticulously designed CuAAC process. This innovative approach resulted in the emission of fluorescence, enabling both precise quantification and visual observation of mRNA. Furthermore, we demonstrated the feasibility of concurrent mRNA synthesis and visualization by seamlessly integrating the CuAAC reaction mix into the mRNA transcription process. Additionally, our novel methodology opens avenues for prospective real-time monitoring of mRNA transcription within artificial cells. These advancements hold significant promise for expanding our comprehension of fundamental cellular processes and finding applications across diverse biological contexts in the future.

Prevalence and factors associated with neck and jaw muscle modulation of tinnitus.

Forceful contractions of neck and jaw muscles have consistently been shown to modulate tinnitus and can be used to screen patients who are responsive to somatic stimulation and, therefore, optimal candidates for somatosensory-based treatment. To identify the factors associated with somatic modulation of tinnitus, 163 patients underwent 19 neck and jaw maneuvers after an extensive physiological and audiological profile was compiled. Overall, tinnitus was modulated in 57.1% of ears tested. Unilateral tinnitus showed greater prevalence of modulation. Neck maneuvers generally decreased tinnitus loudness, whereas jaw maneuvers increased loudness. Female gender and buzzing tinnitus were associated with a high prevalence of modulation and a decrease in tinnitus loudness. Loud tinnitus and low-pitched tonal tinnitus were associated with exacerbation of the condition as a result of somatic testing. Use of these characteristics to select optimal candidates for somatosensory-based tinnitus therapies may be essential for the development of an effective approach for tinnitus treatment.

Clonazepam quiets tinnitus: a randomised crossover study with Ginkgo biloba.

OBJECTIVE: To assess the effect of Ginkgo biloba and clonazepam, a γ-aminobutyric acid (GABA)-receptor agonist, upon tinnitus. METHODS: This was an open-label, randomised, crossover study. 27 men and 11 women (aged 16-80 (mean 58)) with tinnitus for more than 2 months were enrolled. Participants were randomised to either clonazepam or G biloba for the first 3 weeks. For the next 2 weeks of washout no medication was taken. For the final 3 weeks, subjects were given the other drug. The initial dose of clonazepam and G biloba was one tablet daily (clonazepam 0.5 mg; G biloba 40 mg). Subjects were instructed to increase the dose by one tablet every 3 days to a maximum of four tablets daily until they perceived a satisfactory decrease in tinnitus loudness or intolerable side effects. Tinnitus was assessed with pitch and loudness matching, tinnitus handicap inventory, and visual analogue scales of loudness, duration and annoyance. RESULTS: Comparing before and after each drug, clonazepam significantly improved tinnitus loudness (74% of subjects), duration (63%), annoyance (79%), and tinnitus handicap inventory score (61%), whereas the G biloba showed no significant differences on any of these measures. CONCLUSION: Clonazepam is effective in treating tinnitus; G biloba is ineffective.

An iron-chelating sulfonamide identified from Drosophila-based screening for antipathogenic discovery.

We exploited bacterial infection assays using the fruit fly Drosophila melanogaster to identify anti-infective compounds that abrogate the pathological consequences in the infected hosts. Here, we demonstrated that a pyridine-3-N-sulfonylpiperidine derivative (4a) protects Drosophila from the acute infections caused by bacterial pathogens including Pseudomonas aeruginosa. 4a did not inhibit the growth of P. aeruginosa in vitro, but inhibited the production of secreted toxins such as pyocyanin and hydrogen cyanide, while enhancing the production of pyoverdine and pyochelin, indicative of iron deprivation. Based on its catechol moiety, 4a displayed iron-chelating activity in vitro toward both iron (II) and iron (III), more efficiently than the approved iron-chelating drugs such as deferoxamine and deferiprone, concomitant with more potent antibacterial efficacy in Drosophila infections and unique transcriptome profile. Taken together, these results delineate a Drosophila-based strategy to screen for antipathogenic compounds, which interfere with iron uptake crucial for bacterial virulence and survival in host tissues.

Ceramide NPs derived from natural oils of Korean traditional plants enhance skin barrier functions and stimulate expressions of genes for epidermal homeostasis.

BACKGROUND: New ceramide (CER) NPs were prepared by linking fatty acids derived from oils of Korean traditional plants to phytosphingosine (PHS). The oils of Korean traditional plants were extracted from the seeds of Panax ginseng, Camellia sinensis, Glycine max napjakong, Glycine max seoritae, and Camellia japonica as sources of diverse fatty acids. AIMS: The aim of this study was to investigate signaling bioactivities of HP-C. sinensis ceramide NP that was column purified to remove any residual PHS and to evaluate the skin barrier functions of the HP-C. sinensis ceramide NP in human skin. METHODS: The expressions of genes related to epidermal differentiation were analyzed in vitro by qPCR. Human studies were also performed to determine the skin barrier functions with respect to TEWL and SC cohesion. RESULTS: The HP-C. sinensis CER NP significantly enhanced the expressions of FLG, CASP14, and INV indicates that the signaling biological activities of oil-derived ceramide NPs could be different depend on the natural oils. The control ceramide, C18-CER NP, had no effect on the expression of the three genes. HP-C. sinensis CER NP was selected for the in vivo human studies. Application of 0.5% HP-C. sinensis CER NP cream stimulated significantly faster recovery of a disrupted skin barrier than that of the control C18-CER NP. A significant enhancement of SC cohesion of the skin treated with 0.5% HP-C. sinensis CER NP was also observed. CONCLUSION: Taken all together, our results clearly demonstrate that HP-C. sinensis CER NP, P. ginseng CER NP, and other oil-derived CER NP could be a better choice for developing moisturizers to improve skin barrier function as they more closely mimic the endogenous CER composition of the actual human skin barrier.

BHMPS Inhibits Breast Cancer Migration and Invasion by Disrupting Rab27a-Mediated EGFR and Fibronectin Secretion.

Our previous work demonstrated that (E)-N-benzyl-6-(2-(3, 4-dihydroxybenzylidene) hydrazinyl)-N-methylpyridine-3-sulfonamide (BHMPS), a novel synthetic inhibitor of Rab27aSlp(s) interaction, suppresses tumor cell invasion and metastasis. Here, we aimed to further investigate the mechanisms of action and biological significance of BHMPS. BHMPS decreased the expression of epithelial-mesenchymal transition transcription factors through inhibition of focal adhesion kinase and c-Jun N-terminal kinase activation, thereby reducing the migration and invasion of breast cancer. Additionally, knockdown of Rab27a inhibited tumor migration, with changes in related signaling molecules, whereas overexpression of Rab27a reversed this phenomenon. BHMPS effectively prevented the interaction of Rab27a and its effector Slp4, which was verified by co-localization, immunoprecipitation, and in situ proximity ligation assays. BHMPS decreased the secretion of epidermal growth factor receptor and fibronectin by interfering with vesicle trafficking, as indicated by increased perinuclear accumulation of CD63-positive vesicles. Moreover, administration of BHMPS suppressed tumor growth in Rab27a-overexpressing MDA-MB-231 xenograft mice. These findings suggest that BHMPS may be a promising candidate for attenuating tumor migration and invasion by blocking Rab27a-mediated exocytosis.

Cholesterol inhibits M-type K+ channels via protein kinase C-dependent phosphorylation in sympathetic neurons.

M-type (KCNQ) potassium channels play an important role in regulating the action potential firing in neurons. Here, we investigated the effect of cholesterol on M current in superior cervical ganglion (SCG) sympathetic neurons, using the patch clamp technique. M current was inhibited in a dose-dependent manner by cholesterol loading with a methyl-beta-cyclodextrin-cholesterol complex. This effect was prevented when membrane cholesterol level was restored by including empty methyl-beta-cyclodextrin in the pipette solution. Dialysis of cells with AMP-PNP instead of ATP prevented cholesterol action on M currents. Protein kinase C (PKC) inhibitor, calphostin C, abolished cholesterol-induced inhibition whereas the PKC activator, PDBu, mimicked the inhibition of M currents by cholesterol. The in vitro kinase assay showed that KCNQ2 subunits of M channel can be phosphorylated by PKC. A KCNQ2 mutant that is defective in phosphorylation by PKC failed to show current inhibition not only by PDBu but also by cholesterol. These results indicate that cholesterol-induced inhibition of M currents is mediated by PKC phosphorylation. The inhibition of M currents by PDBu and cholesterol was completely blocked by PIP(2) loading, indicating that the decrease in PIP(2)-channel interaction underlies M channel inhibition by PKC-mediated phosphorylation. We conclude that cholesterol specifically regulates M currents in SCG neurons via PKC activation.

The Chromatin Remodeling Complex CHD1 Regulates the Primitive State of Mesenchymal Stromal Cells to Control Their Stem Cell Supporting Activity.

The primitive state (stemness) of mesenchymal stromal cells (MSCs) is responsible for supporting the function of tissue-specific stem cells to regenerate damaged tissues. However, molecular mechanisms regulating the stemness of MSCs remain unknown. In this study, we found that the primitive state of MSCs is hierarchically regulated by the expression levels of the chromatin remodeling complex, CHD1, with CHD1 expression levels higher in the undifferentiated state, and decreasing upon MSC differentiation. Consistently, CHD1 expression levels decrease during progressive loss of clonogenic progenitors (CFU-F) induced by passage cultures. Moreover, knockdown (KD) of CHD1 decreased CFU-F frequency, whereas CHD1 overexpression increased it. In addition, the expression of stem cell-specific genes was down- or upregulated upon KD or overexpression of CHD1, respectively, accompanied by associated changes in chromatin condensation. Importantly, altering CHD1 expression levels affected the ability of MSCs to support the self-renewing expansion of hematopoietic stem cells (HSCs). Furthermore, CHD1 levels were significantly decreased in MSCs from acute myeloid leukemia or aplastic anemia patients, where CFU-F and HSC-supporting activities are lost. Altogether, these findings show that chromatin remodeling by CHD1 is a molecular parameter that influences the primitive state of MSCs and their stem cell-supporting activity, which controls tissue regeneration.

An antipathogenic compound that targets the OxyR peroxide sensor in Pseudomonas aeruginosa.

Introduction. Antipathogenic or antivirulence strategy is to target a virulence pathway that is dispensable for growth, in the hope to mitigate the selection for drug resistance.Hypothesis/Gap Statment. Peroxide stress responses are one of the conserved virulence pathways in bacterial pathogens and thus good targets for antipathogenic strategy.Aim. This study aims to identify a new chemical compound that targets OxyR, the peroxide sensor required for the full virulence of the opportunistic human pathogen, Pseudomonas aeruginosa.Methodology. Computer-based virtual screening under consideration of the 'eNTRy' rules and molecular docking were conducted on the reduced form of the OxyR regulatory domain (RD). Selected hits were validated by their ability to phenocopy the oxyR null mutant and modulate the redox cycle of OxyR.Results. We first isolated three robust chemical hits that inhibit OxyR without affecting prototrophic growth or viability. One (compound 1) of those affected the redox cycle of OxyR in response to H2O2 treatment, in a way to impair its function. Compound 1 displayed selective antibacterial efficacy against P. aeruginosa in Drosophila infection model, without antibacterial activity against Staphylococcus aureus.Conclusion. These results suggest that compound 1 could be an antipathogenic hit inhibiting the P. aeruginosa OxyR. More importantly, our study provides an insight into the computer-based discovery of new-paradigm selective antibacterials to treat Gram-negative bacterial infections presumably with few concerns of drug resistance.

Anti-leukemic Activity of AIU2008 in FLT3-ITD-positive Acute Myeloid Leukemia.

BACKGROUND/AIM: FMS-like tyrosine kinase 3 (FLT3) is a class III receptor tyrosine kinase involved in signal transduction underlying survival, proliferation, and differentiation of hematopoietic cells. An internal tandem duplication (ITD) in FLT3 in the juxtamembrane domain is a common mutation causing human acute myeloid leukemia (AML) and activates constitutive signaling. MATERIALS AND METHODS: We evaluated the novel FLT3 inhibitor 5-(4-fluorophenyl)-N-(naphthalen-1-yl)oxazol-2-amine (AIU2008) for the treatment of AML. RESULTS: AIU2008 was designed by modifying FLT3 inhibitor 7c, and showed improved anti-leukemic efficacy in FLT3-ITD-positive AML cells. Specifically, AIU2008 inhibited cell growth and apoptotic death. In addition, AIU2008 down-regulated DNA repair genes involved in homologous recombination and non-homologous end joining. It contributed to the synergistic inhibition of AML cell growth in combination treatment with PARP inhibitors. CONCLUSION: AIU2008 is a promising FLT3 targeting agent, and may be used in combination with PARP inhibitors for the treatment of AML.

Cohesion establishment factor, Eco1 represses transcription via association with histone demethylase, LSD1.

Accurate chromosome segregation during cell division requires physical attachment of two sister chromatids from DNA replication until mitosis, a process known as sister chromatid cohesion. Sister chromatid cohesion is mediated by a four-subunit cohesin complex that connects sister chromatids by encircling them as molecular rings. Eco1 is an essential acetyltransferase required for the establishment of sister chromatid cohesion. Eco1 acetylates Smc3 and Mcd1 (Rad21) to establish cohesion during S phase and in response to DNA damage, respectively. Here, we show that Eco1 repress transcription in a dose-dependent manner. Mutations of zinc-finger domain or acetyltransferase domain did not significantly affect the transcriptional repression activity of Eco1. We observed that histone demethylase, Lsd1 interacts with Eco1 and is required for the transcriptional repression activity of Eco1. Chromatin immunoprecipitation (ChIP) experiments show that Eco1 facilitates the demethylation of lysine 4 of histone H3. Taken together, we provide the first evidence that Eco1 represses transcription by interacting with histone demethylase, LSD1 to convert chromatin to inactive state.

Recent advances in the development of ß-lactamase inhibitors.

ß-Lactam antibiotics are the most commonly prescribed antibiotics worldwide; however, antimicrobial resistance (AMR) is a global challenge. The ß-lactam resistance in Gram-negative bacteria is due to the production of ß-lactamases, including extended-spectrum ß-lactamases, metallo-ß-lactamases, and carbapenem-hydrolyzing class D ß-lactamases. To restore the efficacy of BLAs, the most successful strategy is to use them in combination with ß-lactamase inhibitors (BLI). Here we review the medically relevant ß-lactamase families and penicillins, diazabicyclooctanes, boronic acids, and novel chemical scaffold-based BLIs, in particular approved and under clinical development.

Non-vanillyl resiniferatoxin analogues as potent and metabolically stable transient receptor potential vanilloid 1 agonists.

A series of non-vanillyl resiniferatoxin analogues, having 4-methylsulfonylaminophenyl and fluorophenyl moieties as vanillyl surrogates, have been investigated as ligands for rat TRPV1 heterologously expressed in Chinese hamster ovary cells. Although lacking the metabolically problematic 4-hydroxy substituent on the A-region phenyl ring, the compounds retained substantial agonist potency. Indeed, the 3-methoxy-4-methylsulfonylaminophenyl analog (1) was modestly (2.5-fold) more potent than RTX, with an EC(50)=0.106 nM. Further, it resembled RTX in its kinetics and pattern of stimulation of the levels of intracellular calcium in individual cells, as revealed by imaging. Compound 1 displayed modestly enhanced in vitro stability in rat liver microsomes and in plasma, suggesting that it might be a pharmacokinetically more favorable surrogate of resiniferatoxin. Molecular modeling analyses with selected analogues provide evidence that the conformational differences could affect their binding affinities, especially for the ester versus amide at the B-region.