Rational design of a new antibiotic class for drug-resistant infections.

The development of new antibiotics to treat infections caused by drug-resistant Gram-negative pathogens is of paramount importance as antibiotic resistance continues to increase worldwide1. Here we describe a strategy for the rational design of diazabicyclooctane inhibitors of penicillin-binding proteins from Gram-negative bacteria to overcome multiple mechanisms of resistance, including ß-lactamase enzymes, stringent response and outer membrane permeation. Diazabicyclooctane inhibitors retain activity in the presence of ß-lactamases, the primary resistance mechanism associated with ß-lactam therapy in Gram-negative bacteria2,3. Although the target spectrum of an initial lead was successfully re-engineered to gain in vivo efficacy, its ability to permeate across bacterial outer membranes was insufficient for further development. Notably, the features that enhanced target potency were found to preclude compound uptake. An improved optimization strategy leveraged porin permeation properties concomitant with biochemical potency in the lead-optimization stage. This resulted in ETX0462, which has potent in vitro and in vivo activity against Pseudomonas aeruginosa plus all other Gram-negative ESKAPE pathogens, Stenotrophomonas maltophilia and biothreat pathogens. These attributes, along with a favourable preclinical safety profile, hold promise for the successful clinical development of the first novel Gram-negative chemotype to treat life-threatening antibiotic-resistant infections in more than 25 years.

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024.

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Thorough QT/QTc study to evaluate the effect of a single supratherapeutic dose of islatravir on QTc interval prolongation in healthy adults.

Islatravir is a deoxynucleoside analog being developed for the treatment of HIV-1 infection. Clinical studies are being conducted to evaluate islatravir, administered in combination with other antiretroviral therapies, at doses of 0.25 mg once daily and 2 mg once weekly. In multiple previous clinical studies, islatravir was generally well tolerated, with no clear trend in cardiac adverse events. A trial was conducted to evaluate the effect of islatravir on cardiac repolarization. A randomized, double-blind, active- and placebo-controlled phase 1 trial was conducted, in which a single dose of islatravir 0.75 mg, islatravir 240 mg (supratherapeutic dose), moxifloxacin 400 mg (active control), or placebo was administered. Continuous 12-lead electrocardiogram monitoring was performed before dosing through 24 hours after dosing. QT interval measurements were collected, and safety and pharmacokinetics were evaluated. Sixty-three participants were enrolled, and 59 completed the study. Fridericia's QT correction for heart rate was inadequate; therefore, a population-specific correction was applied (QTcP). The placebo-corrected change from baseline in QTcP (ΔΔQTcP) interval at the observed geometric mean maximum plasma concentration associated with islatravir 0.75 mg and islatravir 240 mg was <10 ms at all time points. Assay sensitivity was confirmed because the use of moxifloxacin 400 mg led to a ΔΔQTcP >10 ms. The pharmacokinetic profile of islatravir was consistent with that of previous studies, and islatravir was generally well tolerated. Results from the current trial suggest that single doses of islatravir as high as 240 mg do not lead to QTc interval prolongation.

Molecular design and evaluation of aza-polycyclic carbamoyl pyridones as HIV-1 integrase strand transfer inhibitors.

Integrase strand transfer inhibitors (INSTIs) are the most prescribed anchor drug in antiretroviral therapy. Today, there is an increasing need for long-acting treatment of HIV-1 infection. Improving drug pharmacokinetics and anti-HIV-1 activity are key to developing more robust inhibitors suitable for long-acting formulations, but 2nd-generation INSTIs have chiral centers, making it difficult to conduct further exploration. In this study, we designed aza-tricyclic and aza-bicyclic carbamoyl pyridone scaffolds which are devoid of the problematic hemiaminal stereocenter present in dolutegravir (DTG). This scaffold hopping made it easy to introduce several substituents, and evolving structure-activity studies using these scaffolds resulted in several leads with promising properties.

Azacoumarin-based "turn-on" fluorescent probe for the detection and imaging of hydrogen peroxide in living cells.

Azacoumarins are a relatively unexplored group of coumarin fluorophores, despite their excellent light-emitting properties. In this report, we detail the creation and production of a fluorescent probe (PYCB) based on azacoumarin for detecting H2O2. The probe utilizes a carboxy benzyl boronic pinacol ester as the recognition unit and displays a turn-on fluorescence response at 460 nm upon exposure to H2O2. The probe shows excellent sensitivity and selectivity to H2O2, with a detection limit of 0.385 µM. PYCB also exhibited strong pH stability and selectivity for H2O2 over other reactive oxygen species (ROS). Additionally, MTT assay results demonstrated the excellent biocompatibility of PYCB in MCF-7 cell lines. Fluorescence imaging of PYCB-treated MCF-7 cells revealed enhanced blue fluorescence corresponding to varying concentrations of exogenous H2O2.

Coumarin-azasugar-benzyl conjugates as non-neurotoxic dual inhibitors of butyrylcholinesterase and cancer cell growth.

We have applied the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction to prepare a library of ten coumarin-azasugar-benzyl conjugates and two phthalimide-azasugar-benzyl conjugates with potential anti-Alzheimer and anti-cancer properties. The compounds were evaluated as cholinesterase inhibitors, demonstrating a general preference, of up to 676-fold, for the inhibition of butyrylcholinesterase (BuChE) over acetylcholinesterase (AChE). Nine of the compounds behaved as stronger BuChE inhibitors than galantamine, one of the few drugs in clinical use against Alzheimer's disease. The most potent BuChE inhibitor (IC50 = 74 nM) was found to exhibit dual activities, as it also showed high activity (GI50 = 5.6 ± 1.1 µM) for inhibiting the growth of WiDr (colon cancer cells). In vitro studies on this dual-activity compound on Cerebellar Granule Neurons (CGNs) demonstrated that it displays no neurotoxicity.

Fluorescent probes for formaldehyde based on formaldehyde-promoted C-N cleavage of azanyl carbamates.

Formaldehyde (FA) is an endogenous one-carbon metabolite and an environmental pollutant and carcinogen. Elevated FA levels are associated with many diseases. Methods for the convenient and in situ detection of FA levels are of great significance for understanding FA's biofunctions and signalling pathways. Herein, the NAP-FAP2 series of fluorescent probes for FA detection were developed based on FA-promoted C-N cleavage of 3-nitrophenylazanyl N-arylcarbamate via FA-induced intramolecularity, where the aryl group is the fluorophore 1,8-naphthalimide-4-yl. The 3-nitrophenylazanyl containing reactive group also functions as a fluorescence quenching group via a photo-induced electron transfer mechanism to generate turn-on fluorescence response upon reaction with FA. The probes were applied to explore FA level changes in erastin-induced ferroptosis, and it was found that the FA level increases intracellularly, but not in the endoplasmic reticulum, suggesting that the FA level increases in ferroptosis are not derived from lipid peroxidation.

BF2-Bridged Azafulvene Dimer-Based 1064 nm Laser-Driven Superior Photothermal Agent for Deep-Seated Tumor Therapy.

Small organic photothermal agents (PTAs) with absorption bands located in the second near-infrared (NIR-II, 1000-1700 nm) window are highly desirable for effectively combating deep-seated tumors. However, the rarely reported NIR-II absorbing PTAs still suffer from a low molar extinction coefficient (MEC, ϵ), inadequate chemostability and photostability, as well as the high light power density required during the therapeutic process. Herein, we developed a series of boron difluoride bridged azafulvene dimer acceptor-integrated small organic PTAs. The B-N coordination bonds in the π-conjugated azafulvene dimer backbone endow it the strong electron-withdrawing ability, facilitating the vigorous donor-acceptor-donor (D-A-D) structure PTAs with NIR-II absorption. Notably, the PTA namely OTTBF shows high MEC (7.21×104 M-1 cm-1), ultrahigh chemo- and photo-stability. After encapsulated into water-dispersible nanoparticles, OTTBF NPs can achieve remarkable photothermal conversion effect under 1064 nm irradiation with a light density as low as 0.7 W cm-2, which is the lowest reported NIR-II light power used in PTT process as we know. Furthermore, OTTBF NPs have been successfully applied for in vitro and in vivo deep-seated cancer treatments under 1064 nm laser. This study provides an insight into the future exploration of versatile D-A-D structured NIR-II absorption organic PTAs for biomedical applications.

In-Class Cross-Reactivity among Hospitalized Patients with Hypersensitivity Reactions to Fluoroquinolones.

Results from this large, multicenter study suggest that patients with a confirmed ciprofloxacin, moxifloxacin, or levofloxacin hypersensitivity reaction are likely to tolerate other fluoroquinolones. Avoiding different fluoroquinolones in patients labeled with a ciprofloxacin, moxifloxacin, or levofloxacin allergy may not always be mandatory. This was a study of patients with a ciprofloxacin, moxifloxacin, or levofloxacin hypersensitivity reaction and a documented electronic medical record administration of a different fluoroquinolone. Numerically, the most common reaction risk occurred with a challenge to moxifloxacin (2/19; 9.5%), followed by ciprofloxacin (6/89; 6.3%), and levofloxacin (1/44; 2.2%).

Consecutive action of two BAHD acyltransferases promotes tetracoumaroyl spermine accumulation in chicory.

Fully substituted phenolamide accumulation in the pollen coat of Eudicotyledons is a conserved evolutionary chemical trait. Interestingly, spermidine derivatives are replaced by spermine derivatives as the main phenolamide accumulated in the Asteraceae family. Here, we show that the full substitution of spermine in chicory (Cichorium intybus) requires the successive action of two enzymes, that is spermidine hydroxycinnamoyl transferase-like proteins 1 and 2 (CiSHT1 and CiSHT2), two members of the BAHD enzyme family. Deletion of these genes in chicory using CRISPR/Cas9 gene editing technology evidenced that CiSHT2 catalyzes the first N-acylation steps, whereas CiSHT1 fulfills the substitution to give rise to tetracoumaroyl spermine. Additional experiments using Nicotiana benthamiana confirmed these findings. Expression of CiSHT2 alone promoted partially substituted spermine accumulation, and coexpression of CiSHT2 and CiSHT1 promoted synthesis and accumulation of the fully substituted spermine. Structural characterization of the main product of CiSHT2 using nuclear magnetic resonance revealed that CiSHT2 preferentially catalyzed N-acylation of secondary amines to form N5,N10-dicoumaroyl spermine, whereas CiSHT1 used this substrate to synthesize tetracoumaroyl spermine. We showed that spermine availability may be a key determinant toward preferential accumulation of spermine derivatives over spermidine derivatives in chicory. Our results reveal a subfunctionalization among the spermidine hydroxycinnamoyl transferase that was accompanied by a modification of free polyamine metabolism that has resulted in the accumulation of this new phenolamide in chicory and most probably in all Asteraceae. Finally, genetically engineered yeast (Saccharomyces cerevisiae) was shown to be a promising host platform to produce these compounds.

HNODThia: A Promising Chelator for the Development of 64Cu Radiopharmaceuticals.

Herein, we present the synthesis and coordination chemistry of copper(II) and zinc(II) complexes of two novel heterocyclic triazacyclononane (tacn)-based chelators (HNODThia and NODThia-AcNHEt). The chelator HNODThia was further derivatized to obtain a novel PSMA-based bioconjugate (NODThia-PSMA) and a bifunctional photoactivatable azamacrocyclic analogue, NODThia-PEG3-ArN3, for the development of copper-64 radiopharmaceuticals. 64Cu radiolabeling experiments were performed on the different metal-binding chelates, whereby quantitative radiochemical conversion (RCC) was obtained in less than 10 min at room temperature. The in vitro stability of NODThia-PSMA in human plasma was assessed by ligand-challenge and copper-exchange experiments. Next, we investigated the viability of the photoactivatable analog (NODThia-PEG3-ArN3) for the light-induced photoradiosynthesis of radiolabeled proteins. One-pot photoconjugation reactions to human serum albumin (HSA) as a model protein and the clinically relevant monoclonal antibody formulation MetMAb were performed. [64Cu]Cu-7-azepin-HSA and [64Cu]Cu-7-azepin-onartuzumab were prepared in less than 15 min by irradiation at 395 nm, with radiochemical purities (RCP) of >95% and radiochemical yields (RCYs) of 42.7 ± 5.3 and 49.6%, respectively. Together, the results obtained here open the way for the development of highly stable 64Cu-radiopharmaceuticals by using aza-heterocyclic tacn-based chelators, and the method can easily be extended to the development of 67Cu radiopharmaceuticals for future applications in molecularly targeted radio(immuno)therapy.

Synthesis, Characterization, Antimicrobial and Antimalarial Activities of Azines Based Schiff Bases and their Pd(II) Complexes.

Herein, we report synthesis, characterization, antimicrobial and antimalarial activities of azines Schiff base ligands (L1 -L4 ) and their palladium (II) complexes (C1 -C4 ) of [Pd(L)(OAc)2 ] type. The azine ligands (L1 -L4 ) were prepared by condensation of carbonyl compounds with hydrazine hydrate and their complexes by the reaction of palladium acetate with L1 -L4 ligands in 1 : 1 molar ratio. The prepared ligands and their complexes were characterized by spectral characterization using 1 H &13 C-NMR, FT-IR and mass spectral studies, which revealed that the ligands coordinates via azomethine nitrogen and heteroatom or aryl carbon with palladium. Moreover, Schiff bases and their palladium (II) complexes have been screened for their antibacterial (S. aureus, B. subtillis, and S. typhi, P. aeruginosa), antifungal (C. albicans, A. niger, and A. clavatus) and antimalarial (P. falciparum) activities. The Schiff base L4 showed good results for antibacterial against S. aureus (MIC, 50 µg/mL) and antimalarial against P. falciparum (IC50 , 0.83 µg/mL). The complex C1 showed best antibacterial activity (MIC, 62.5 µg/mL) against S. typhi and the complex C4 exhibited remarkable antimalarial activity (IC50 , 0.42 µg/mL) among the tested compounds. Thus, azines based ligands and their Pd complexes can be good antimicrobial and antimalarial agents if explored further.

Highly sensitive and rapid detection of resorcinol by forming fluorescent azamonardine with dopamine.

We propose a sensitive, selective, and rapid fluorescent assay for detecting resorcinol (RC) based on its specific chemical reaction with dopamine. Under alkaline condition, RC would react with dopamine to yield fluorescent azamonardine, which emits strong blue fluorescence and has a superior excitation wavelength at 416 nm and an emission wavelength at 461 nm. The azamonardine with a molecular weight of 258.1 confirmed by ICP-MS has a quantum yield of 71.3%. The reaction is completed within 1 min showing great potential for point-of-care testing. This assay showed high sensitivity and had a good relationship between fluorescent intensity at 461 nm and RC concentration (I461 = 106.4 + 93.6*CRC; R2 = 0.9904) over the range of 0-40 µM. More importantly, the assay showed a prominent anti-interference from various substances and even can distinguish RC from its isomers, o-dihydroxybenzene and p-dihydroxybenzene. Finally, our assay successfully quantified RC contents in wheat powder and hair dyes with high accuracy.

N1/N4 1,4-Cycloaddition of 1,2,4,5-Tetrazines with Enamines Promoted by the Lewis Acid ZnCl2.

The second example of selective N1/N4 1,4-cycloaddition (vs C3/C6 1,4-cycloaddition) of 1,2,4,5-tetrazines with preformed or in situ generated enamines now promoted by the Lewis acid ZnCl2 and with an expanded scope is described. The reaction constitutes a formal [4 + 2] cycloaddition across two nitrogen atoms (N1/N4 vs C3/C6) of a 1,2,4,5-tetrazine followed by retro [4 + 2] cycloaddition loss of a nitrile and aromatization to provide 1,2,4-triazines. Optimization of reaction parameters, simplification of its implementation through in situ enamine generation from ketones, definition of the enamine reaction scope for 3,6-bis(thiomethyl)-1,2,4,5-tetrazine, exploration of the 1,2,4,5-tetrazine scope, and representative applications of the product 1,2,4-triazines are detailed. The work establishes and further extends a powerful method for efficient one-step regioselective synthesis of 1,2,4-triazines under mild reaction conditions directly now from easily accessible ketones. It extends the substrate scope of a solvent (hexafluoroisopropanol) hydrogen bonding-promoted reaction that we recently reported with aryl-conjugated enamines, permitting the use of simple ketone-derived enamines and expanding the generality of the remarkable reaction. The reaction is regioselective with respect to the site of reaction with unsymmetrical ketones and provides exclusively a single 1,2,4-triazine regioisomer consistent with our previously established stepwise mechanism of formal N1/N4 1,4-cycloaddition, overcoming the challenges observed in conventional approaches to 1,2,4-triazines.

Design, synthesis, and antitumor study of a series of novel 1-Oxa-4-azaspironenone derivatives.

A series of 1-oxa-4-azaspiro[4,5]deca-6,9-diene-3,8-dione derivatives containing structural fragments of conjugated dienone have been synthesized previously by our group, however the Michael addition reaction between conjugated dienone and nucleophilic groups in the body may generate harmful and adverse effects. To reduce harmful side effects, the authors started with p-aminophenol to make 1-oxo-4- azaspirodecanedione derivatives, then utilized the Michael addition and cyclopropanation to eliminate α, ß unsaturated olefinic bond and lower the Michael reactivity of the compounds in vivo for optimization. At the same time, heteroatoms are put into the molecules in order to improve the hydrophilicity of the molecules and the binding sites of the molecules and the target molecules, establishing the groundwork for improved antitumor activity. The majority of the compounds had moderate to potent activity against A549 human lung cancer cells, MDA-MB-231 breast cancer cells, and Hela human cervical cancer cells. Among them, the compound 6d showed the strongest effect on A549 cell line with IC50 of 0.26 µM; the compound 8d showed the strongest cytotoxicity on MDA-MB-231 cell line with IC50 of 0.10 µM; and the compound 6b showed the strongest activity on Hela cell line with IC50 of 0.18 µM.

Palladium-catalyzed annulative π-extension of o-halobiphenyls with o-chloropyridinecarboxylic acids to access azatriphenylenes.

A palladium-catalyzed bay-region annulative π-extension reaction of o-halobiphenyls with o-chloropyridinecarboxylic acids was developed. The reaction was carried out with a 1 : 1 ratio of substrates. A variety of azatriphenylene derivatives could be synthesized by this approach. This transformation could be applied to the synthesis of ionic liquid-crystalline molecules.

Recent developments in the utility of saturated azaheterocycles in peptidomimetics.

To a large extent, the physical and chemical properties of peptidomimetic molecules are dictated by the integrated heterocyclic scaffolds they contain. Heterocyclic moieties are introduced into a majority of peptide-mimicking molecules to modulate conformational flexibility, improve bioavailability, and fine-tune electronics, and in order to achieve potency similar to or better than that of the natural peptide ligand. This mini-review delineates recent developments, limited to the past five years, in the utility of selected saturated 3- to 6-membered heterocyclic moieties in peptidomimetic design. Also discussed is the chemistry involved in the synthesis of the azaheterocyclic scaffolds and the structural implications of the introduction of these azaheterocycles in peptide backbones as well as side chains of the peptide mimics.

Discovery of novel 2,8-diazaspiro[4.5]decan-1-one derivatives as potent RIPK1 kinase inhibitors.

Necroptosis, a key form of programmed lytic cell death, has gained recognition as an important driver in various inflammatory diseases. Inhibition of kinase activity of receptor interaction protein kinase 1 (RIPK1), which block the activation of the necroptosis pathway has shown therapeutic potential in many human diseases. In order to find new chemotypes of RIPK1 inhibitors, a virtual screening workflow was performed and led to the discovery of 8-benzoyl-3-benzyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (compound 8) as a hit compound. Further structural optimization identified a series of 2,8-diazaspiro[4.5]decan-1-one derivatives as potent RIPK1 inhibitors. Among them, compound 41 exhibited prominent inhibitory activity against RIPK1 with an IC50 value of 92 nM. Meanwhile, compound 41 showed a significant anti-necroptotic effect in a necroptosis model in U937 cells. Therefore, compound 41 could be employed as a lead compound of RIPK1 inhibitors for further structural optimization.

Two-photon absorption and triplet excited state quenching of near-IR region aza-BODIPY photosensitizers via a triphenylamine moiety despite heavy bromine atoms.

Aza-BODIPY compounds with methoxy groups at -3 and -5 and triphenylamine moieties at -1 and -7 positions with and without heavy bromine atoms at -2 and -6 positions have been designed and synthesized. The chemical structures of the novel compounds were fully characterized using 1H NMR, 13C NMR, FTIR, and HRMS-TOF-ESI techniques. Steady-state absorption and emission features were investigated to analyze ground-state interactions. The effects of triphenylamine moieties and bromine atoms on charge transfer dynamics and two-photon absorption (TPA) properties were investigated using femtosecond transient absorption spectroscopy measurements and open-aperture (OA) Z-scan experiments, respectively. Contrary to popular belief, the compound containing heavy bromine atoms and triphenylamine moieties did not demonstrate any triplet transition. Since the triphenylamine moiety has high electron-donating properties and a long conjugation length, it exhibited intramolecular charge transfer (ICT) features from electron-donating moieties to the aza-BODIPY core. Additionally, it is concluded that the excited-state lifetime is shortened in the presence of a bromine atom with triphenylamine moieties. This result is rather interesting since the triplet excited state is quenched by the triphenylamine moiety despite the presence of a heavy bromine atom. The performed OA Z-scan experiments revealed that the aza-BODIPY compound containing bromine atoms has a higher TPA cross-section value (116 GM) due to efficient intramolecular charge transfer compared to that without bromine atoms (89 GM). Additionally, in the theoretical calculations, it was found that the charge transfer percentage (CT%) was the strongest in compounds containing bromine atoms.

Regioselectivity in inhibition of peptide deformylase from Haemophilus influenzae by 4- vs 5-azaindole hydroxamic acid derivatives: Biochemical, structural and antimicrobial studies.

Ribosome assisted protein synthesis in all prokaryotes begins with a formylated methionine. Deformylation and demethionylation of these newly synthesized proteins are critical co-translational events carried out by peptide deformylase (PDF) and methionine aminopeptidase (MetAP) in all living cells. Since the mechanism of N-terminal modification is common between the infectious microbes and the host human cells, it is a challenge to identify selective inhibitors. Given that both MetAP and PDF are metalloenzymes, and have strong affinity for hydroxamic acids, we reasoned that the azaindole-based hydroxamic acids could inhibit the PDF enzymes. In the present study we describe the screening of a 17-compound library with 4- and 5- substituted azaindole hydroxamic acid derivatives against PDF enzyme from H. influenzae (HiPDF), M. tuberculosis (MtPDF) and human PDF (HsPDF). Several of these molecules showed nanomolar inhibition against HiPDF enzyme, best at 21 nM (15). On the other hand, none of these compounds inhibited the human enzyme while only two molecules showed moderate inhibition against Mtb enzyme. Surprisingly only 5-substituted azaindole derivatives inhibited the PDF enzymes. Some of the 5-substituted azaindole compounds inhibited the growth of different microbes indicating their potential application in antimicrobial therapy. Crystallographic and modeling studies provided the mechanistic view of regioselective inhibition.