The Evolving Landscape of Fecal Microbial Transplantation

The human gastrointestinal tract houses an enormous microbial ecosystem. Recent studies have shown that the gut microbiota plays significant physiological roles and maintains immune homeostasis in the human body. Dysbiosis, an imbalanced gut microbiome, can be associated with various disease states, as observed in infectious diseases, inflammatory diseases, autoimmune diseases, and cancer. Modulation of the gut microbiome has become a therapeutic target in treating these disorders. Fecal microbiota transplantation (FMT) from a healthy donor restores the normal gut microbiota homeostasis in the diseased host. Ample evidence has demonstrated the efficacy of FMT in recurrent Clostridioides difficile infection (rCDI). The application of FMT in other human diseases is gaining attention. This review aims to increase our understanding of the mechanisms of FMT and its efficacies in human diseases. We discuss the application, route of administration, limitations, safety, efficacies, and suggested mechanisms of FMT in rCDI, autoimmune diseases, and cancer. Finally, we address the future perspectives of FMT in human medicine.

Preparation of 3-Substituted Isoindolin-1-one, Cinnoline, and 1,2,4-[e]-Benzotriazine Derivatives

Herein, we report a new approach to synthesize a series of 1,2,4-[e]-benzotriazine and cinnoline derivatives from 3-substituted isoindolin-1-one. All the reported products are obtained through an economical two-step synthetic procedure resulting in fair-to-high yields. Cinnolines (a) and 1,2,4-[e]-benzotriazines (b) result from an intramolecular cyclization of the corresponding 3-substituted isoindolin-1-ones, which, in turn, are prepared by an addition reaction from 2-cyanobenzaldehyde and 2-(2-nitrophenyl) acetonitrile (a) or 2-nitroaniline derivatives (b). A proposed mechanism for this transformation is presented.

Autoimmunity affecting the biliary tract fuels the immunosurveillance of cholangiocarcinoma

Cholangiocarcinoma (CCA) results from the malignant transformation of cholangiocytes. Primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC) are chronic diseases in which cholangiocytes are primarily damaged. Although PSC is an inflammatory condition predisposing to CCA, CCA is almost never found in the autoimmune context of PBC. Here, we hypothesized that PBC might favor CCA immunosurveillance. In preclinical murine models of cholangitis challenged with syngeneic CCA, PBC (but not PSC) reduced the frequency of CCA development and delayed tumor growth kinetics. This PBC-related effect appeared specific to CCA as it was not observed against other cancers, including hepatocellular carcinoma. The protective effect of PBC was relying on type 1 and type 2 T cell responses and, to a lesser extent, on B cells. Single-cell TCR/RNA sequencing revealed the existence of TCR clonotypes shared between the liver and CCA tumor of a PBC host. Altogether, these results evidence a mechanistic overlapping between autoimmunity and cancer immunosurveillance in the biliary tract.

Heterocycles as a Peptidomimetic Scaffold: Solid-Phase Synthesis Strategies

Peptidomimetics are a privileged class of pharmacophores that exhibit improved physicochemical and biological properties. Solid-phase synthesis is a powerful tool for gaining rapid access to libraries of molecules from small molecules to biopolymers and also is widely used for the synthesis of peptidomimetics. Small molecules including heterocycles serve as a core for hundreds of drugs, including peptidomimetic molecules. This review covers solid-phase synthesis strategies for peptidomimetics molecules based on heterocycles.

Davis-Beirut Reaction Inspired Nitroso Diels-Alder Reaction

A Davis-Beirut reaction inspired nitroso Diels-Alder protocol is reported. The starting material for the procedure is a nitrophenyl moiety with the para position appropriately substituted with a 2°-amine (see 5) or 2°-alcohol (see 6). Deprotonation at the benzylic position followed by concomitant oxidation of the benzylic position and reduction of the nitro moiety delivers a nitrosophenyl intermediate, which subsequently undergoes a nitroso Diels-Alder reaction. This one-pot procedure delivers aryldihydro-1,2-oxazines in moderate yields.

1-BENZYLSPIRO[PIPERIDINE-4,1'-PYRIDO[3,4-b]indole] 'co-potentiators' for minimal function CFTR mutants

We previously identified a spiro [piperidine-4,1-pyrido [3,4-b]indole] class of co-potentiators that function in synergy with existing CFTR potentiators such as VX-770 or GLGP1837 to restore channel activity of a defined subset of minimal function cystic fibrosis transmembrane conductance regulator (CFTR) mutants. Here, structure-activity studies were conducted to improve their potency over the previously identified compound, 20 (originally termed CP-A01). Targeted synthesis of 37 spiro [piperidine-4,1-pyrido [3,4-b]indoles] was generally accomplished using versatile two or three step reaction protocols with each step having high efficiency. Structure-activity relationship studies established that analog 2i, with 6'-methoxyindole and 2,4,5-trifluorobenzyl substituents, had the greatest potency for activation of N1303K-CFTR, with EC50 ∼600 nM representing an ∼17-fold improvement over the original compound identified in a small molecule screen.

A Redox Isomerization Strategy for Accessing Modular Azobenzene Photoswitches with Near Quantitative Bidirectional Photoconversion

Photoswitches capable of accessing two geometric states are highly desirable, especially if their design is modular and incorporates a pharmacophore tethering site. We describe a redox isomerization strategy for synthesizing p-formylazobenzenes from p-nitrobenzyl alcohol. The resulting azo-aldehydes can be readily converted to photoswitchable compounds with excellent photophysical properties using simple hydrazide click chemistry. As a proof of principle, we synthesized a photoswitchable surfactant enabling the photocontrol of an emulsion with exceptionally high spatiotemporal precision.

Davis-Beirut Reaction: Diverse Chemistries of Highly Reactive Nitroso Intermediates in Heterocycle Synthesis

Indazoles are an important class of nitrogen heterocycles because of their excellent performance in biologically relevant applications, such as in chemical biology and medicinal chemistry. In these applications, convenient synthesis using commercially available and diverse building blocks is highly desirable. Within this broad class, 2H-indazoles are relatively underexploited when compared to 1H-indazole, perhaps because of regioselectivity issues associated with the synthesis of 2H-indazoles. This Account describes our unfolding of the synthetic utility of the Davis-Beirut reaction (DBR) for the construction of 2H-indazoles and their derivatives; parallel unfoldings of mechanistic models for these interrelated N-N bond forming reactions are also summarized. The Davis-Beirut reaction is a robust method that exploits the diverse chemistries of a key nitroso imine or nitroso benzaldehyde intermediate generated in situ under redox neutral conditions. The resulting N-N bond-forming heterocyclization between nucleophilic and electrophilic nitrogens can be leveraged for the synthesis of multiple classes of indazoles and their derivatives, such as simple or fused indazolones, thiazolo-indazoles, 3-alkoxy-2H-indazoles, 2H-indazole N-oxides, and 2H-indazoles with various substitutions on the ring system or the nitrogens. These diverse products can all be synthesized under alkaline conditions and the various strategies for accessing these heterocycles are discussed. Alternatively, we have also developed methods involving mild photochemical conditions for the nitrobenzyl → aci-nitro → nitroso imine sequence. Solvent consideration is especially important for modulating the chemistry of the reactive intermediates in these reactions; the presence of water is critically important in some cases, but water's beneficial effect has a ceiling because of the alternative reaction pathways it enables. Fused 2H-indazoles readily undergo ring opening reactions to give indazolones when treated with nucleophiles or electrophiles. Furthermore, palladium-catalyzed cross coupling, the Sonagashira reaction, EDC amide coupling, 1,3-dipolar cycloadditions with nitrile oxides, copper-catalyzed alkyne-azide cycloadditions (click reaction), as well as copper-free click reactions, can all be used late-stage to modify 2H-indazoles and indazolones. The continued development and applications of the Davis-Beirut reaction has provided many insights for taming the reactivity of highly reactive nitro and nitroso groups, which still has a plethora of underexplored chemistries and challenges. For example, there is currently a limited number of nonfused 2H-indazole examples containing an aryl substitution at nitrogen. This is caused by relatively slow N-N bond formation between N-aryl imine and nitroso reactants, which allows water to add to the key nitroso imine intermediate causing imine bond cleavage to be a competitive reaction pathway rather than proceeding through the desired N-N bond-forming heterocyclization.

Davis-Beirut Reaction: A Photochemical Brønsted Acid Catalyzed Route to N-Aryl 2H-Indazoles

The Davis-Beirut reaction provides access to 2H-indazoles from aromatic nitro compounds. However, N-aryl targets have been traditionally challenging to access due to competitive alternate reaction pathways. Previously, the key nitroso imine intermediate was generated under alkaline conditions, but as reported here, the photochemistry of o-nitrobenzyl alcohols empowered Brønsted acid catalyzed conditions for accessing N-aryl targets. Anilines and alkyl amines give different outcomes under optimized conditions; the proposed mechanism was studied using quantum chemical calculations.

Synthesis and evaluation of tetrahydropyrazolopyridine inhibitors of anion exchange protein SLC26A4 (pendrin)

Pendrin is a transmembrane chloride/anion antiporter that is strongly upregulated in the airways in rhinoviral infection, asthma, cystic fibrosis and chronic rhinosinusitis. Based on its role in the regulation of airway surface liquid depth, pendrin inhibitors have potential indications for treatment of inflammatory airways diseases. Here, a completely regioselective route to tetrahydro-pyrazolopyridine pendrin inhibitors based on 1,3-diketone and substituted hydrazine condensation was been developed. Structure-activity relationships at the tetrahydropyridyl nitrogen were investigated using a focused library, establishing the privileged nature of N-phenyl ureas and improving inhibitor potency by greater than 2-fold.

Abstract 4797: A novel Diiminoquinone targets colorectal cancer stem cells

5-Fluorouracil (5-Fu) remains the standard chemotherapy for metastatic colorectal cancer, but drug resistance and unpredictable cardiotoxicity limit its effectiveness. The high recurrence rates and common resistance are thought to be due to a population of self-renewing cancer stem cells (CSCs). In this study, we synthesized four novel heterocyclic compounds that are similar in structure with quinones and tested their anticancer activity against HCT116 human colon cancer cells in 2D monolayer and 3D sphere cultures. In 2D, all compounds caused significant inhibition of colon cancer cell viability at concentrations non-cytotoxic to normal human FHs74Int intestinal cell lines. In 3D cultures, these heterocycles eradicated the self-renewal ability of the highly resistant cancer stem cells and inhibited colon sphere formation in first generation (G1), as well as subsequent generations. This study represents the first documentation of the activity of these novel heterocyclic compounds, particularly compound 6a, abbreviated as DIQ-3, which we propose to be an effective treatment strategy to prevent colon cancer recurrence by targeting colorectal CSCs. Our findings provide the basis for suggesting these non-toxic and stable compounds for additional testing against cancer.

Citation Format: Alissar Monzer, Nayri Jabotian, Jie S. Zhu, Mark J. Kurth, Wassim Abou Kheir, Makhlouf Haddadin, Hala Gali-Muhtasib. A novel Diiminoquinone targets colorectal cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4797.

Accessing Multiple Classes of 2 H-Indazoles: Mechanistic Implications for the Cadogan and Davis-Beirut Reactions

The Cadogan cyclization is a robust but harsh method for the synthesis of 2 H-indazoles, a valuable class of nitrogen heterocycles. Although nitrene generation by exhaustive deoxygenation is widely accepted as the operating mechanism in the reductive cyclization of nitroaromatics, non-nitrene pathways have only been theorized previously. Here, 2 H-indazole N-oxides were synthesized through an interrupted Cadogan/Davis-Beirut reaction and are presented as direct evidence of competent oxygenated intermediates; mechanistic implications for both reactions are discussed. Isolation and characterization of these N-oxides enabled a formal Cadogan cyclization at room temperature for 2 H-indazole synthesis.

Novel 2-(5-Imino-5H-isoquinolones[3,4-b]quinoxalin-7-ylmethyl)-benzonitrile () and Other Related Derivatives Targeting Colon Cancer Cells: Syntheses and in Vitro Models

Chemotherapy has been shown to be effective in reducing the progression and development of cancer in metastatic patients. However, drug selectivity is still a major issue for most chemotherapeutics. In this study, we synthesized four novel heterocyclic compounds having similarity in structure with quinone systems whereby nitrogen atoms replace the oxygen atoms. The anticancer activity of these compounds (DIQ3-6) was tested against HCT116 human colon cancer cells. We showed that all four heterocycles caused significant reduction in colon cancer cell viability at doses as low as 4 μM, a concentration that was not cytotoxic to normal human FHs74Int intestinal cell lines. Interestingly, these heterocycles inhibited colon sphere formation in 3D cultures at first generation (G₁), mainly because of inhibition of proliferation as evidenced by Ki67 staining. Thus, DIQ3 causes sufficient eradication of the self-renewal ability of the highly resistant cancer stem cells. This study represents the first documentation of the activity of these novel heterocyclic compounds, particularly compound DIQ3, and their potential therapeutic use in targeting colon cancer self-renewal capacity. Our findings provide the basis for proposing these nontoxic and stable compounds for additional testing against cancer.

Photochemical Preparation of 1,2-Dihydro-3 H-indazol-3-ones in Aqueous Solvent at Room Temperature

o-Nitrosobenzaldehyde is a reactive intermediate useful in the synthesis of nitrogen heterocycles. Previous strategies for using o-nitrosobenzaldehyde involve its isolation via chromatography and/or formation under harsh conditions. Herein, this intermediate was photochemically generated in situ from o-nitrobenzyl alcohols in a mild, efficient manner for the construction of 1,2-dihydro-3 H-indazol-3-ones using an aqueous solvent at room temperature. This convenient reaction offers several advantages over reported methods. The commercially available photoreactor employed 3 × 18 W bulbs outputting broad emission above 365 nm.

N-N Bond Formation between Primary Amines and Nitrosos: Direct Synthesis of 2-Substituted Indazolones with Mechanistic Insights

A concise, one-step route to indazolones from primary alkyl amines and o-nitrobenzyl alcohols is reported. The key step in this readily scalable indazolone forming process involves base-mediated in situ o-nitrobenzyl alcohol → o-nitrosobenzaldehyde conversion. Although this functional group interconversion is known to be useful for 2 H-indazole synthesis, its reactivity was modulated for indazolone formation.

Combination potentiator ('co-potentiator') therapy for CF caused by CFTR mutants, including N1303K, that are poorly responsive to single potentiators

BACKGROUND

Current modulator therapies for some cystic fibrosis-causing CFTR mutants, including N1303K, have limited efficacy. We provide evidence here to support combination potentiator (co-potentiator) therapy for mutant CFTRs that are poorly responsive to single potentiators.

METHODS

Functional synergy screens done on N1303K and W1282X CFTR, in which small molecules were tested with VX-770, identified arylsulfonamide-pyrrolopyridine, phenoxy-benzimidazole and flavone co-potentiators.

RESULTS

A previously identified arylsulfonamide-pyrrolopyridine co-potentiator (ASP-11) added with VX-770 increased N1303K-CFTR current 7-fold more than VX-770 alone. ASP-11 increased by ~65% of the current of G551D-CFTR compared to VX-770, was additive with VX-770 on F508del-CFTR, and activated wild-type CFTR in the absence of a cAMP agonist. ASP-11 efficacy with VX-770 was demonstrated in primary CF human airway cell cultures having N1303K, W1282X and G551D CFTR mutations. Structure-activity studies on 11 synthesized ASP-11 analogs produced compounds with EC₅₀ down to 0.5 μM.

CONCLUSIONS

These studies support combination potentiator therapy for CF caused by some CFTR mutations that are not effectively treated by single potentiators.

Davis-Beirut Reaction: Alkoxide versus Hydroxide Addition to the Key o-Nitrosoimine Intermediate

Reaction options, alkoxide vs hydroxide vs amine addition to the key intermediate (o-nitrosoimine) generated in the Davis-Beirut reaction of an o-nitrobenzylamine substrate, are reported to explain the nucleophilic addition selectivity of this one-pot indazole-forming process. The hydroxide addition/deprotection pathway as well as the fate of the resulting o-nitrosobenzaldehyde were both uncovered with several o-nitrobenzylamine substrates, and design elements required for an efficient double Davis-Beirut reaction, inspired by new mechanistic insights, were defined.

Heart-type fatty acid-binding protein (H-FABP) and highly sensitive troponin T (hsTnT) as markers of myocardial injury and cardiovascular events in elective percutaneous coronary intervention (PCI)

BACKGROUND/INTRODUCTION

Type 4a myocardial infarction (MI) occurs when myocardial injury is combined with either symptoms suggestive of myocardial ischaemia, new left bundle branch block, angiographic loss of patency of a major artery or imaging suggestive of new loss of myocardium. Myocardial injury is defined as a rise of >5 x 99th upper reference limit (URL) of 14 ng/l (i.e. >70 ng/l) for highly sensitive troponin T (hsTnT) at 6 h if hsTnT was normal at baseline or >20% rise from 0 to 6 h if hsTnT was >14 ng/l at baseline.

AIM

To assess the prognostic value of biomarkers of myocardial injury following elective percutaneous coronary intervention (PCI).

DESIGN

A cohort of 209 patients were included of whom 144 (68.9%) were male, mean age was 68.8 years, 28 (13.4%) were smokers, 31 (14.8%) were diabetic, 199 (95.2%) had hypercholesterolaemia and 138 (66.0%) had hypertension.

METHODS

We evaluated hsTnT, heart-type fatty acid-binding protein (H-FABP), troponin I (TnI), creatine kinase MB type (CKMB), myoglobin, glycogen phosphorylase BB (GPBB) and carbonic anhydrase III (CA III) at 0, 4, 6 and 24 h following elective PCI. Patients were followed up at 1 year to assess for major adverse clinical events (MACE).

RESULTS

Myocardial injury was observed in 37 (17.7%) patients. Median hsTnT/H-FABP at 4 h were most predictive. MACE was noted in 6 (2.9%) patients, 3 had type 4a MI post PCI, P = 0.036.

DISCUSSION/CONCLUSIONS

Median 4 h hsTnT/H-FABP were most predictive of myocardial injury following PCI. H-FABP and hsTnT were predictive of MACE.

Diverting Reactive Intermediates Toward Unusual Chemistry: Unexpected Anthranil Products from Davis-Beirut Reaction

The discovery of a new variation on the Davis-Beirut reaction is described in which an atypical heterocyclic framework (the anthranil or benzo[c]isoxazole framework) is formed as the result of diversion of a key reactive intermediate away from its expected reactivity-a potentially general approach to reaction design and development. Experimental and computational support for the proposed mechanism and origins of altered reactivity are described.

The fingerprint of antimitochondrial antibodies and the etiology of primary biliary cholangitis

The identification of environmental factors that lead to loss of tolerance has been coined the holy grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein, we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177-252 (PDC-228) with a 62-residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 inner lipoyl domain (ILD). We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA-modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the immunoglobulin M isotype and more dominant in early-stage primary biliary cholangitis (PBC), suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition, we analyzed PPL, LA-PPL, and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by enzyme-linked immunosorbent assay, immunoblotting, and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid.

CONCLUSION

A molecular understanding of the conformation of xenobiotic-modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. (Hepatology 2017;65:1670-1682).

Phenylquinoxalinone CFTR activator as potential prosecretory therapy for constipation

Constipation is a common condition for which current treatments can have limited efficacy. By high-throughput screening, we recently identified a phenylquinoxalinone activator of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel that stimulated intestinal fluid secretion and normalized stool output in a mouse model of opioid-induced constipation. Here, we report phenylquinoxalinone structure-activity analysis, mechanism of action, animal efficacy data in acute and chronic models of constipation, and functional data in ex vivo primary cultured human enterocytes. Structure-activity analysis was done on 175 phenylquinoxalinone analogs, including 15 synthesized compounds. The most potent compound, CFTRact-J027, activated CFTR with EC50 ∼ 200 nM, with patch-clamp analysis showing a linear CFTR current-voltage relationship with direct CFTR activation. CFTRact-J027 corrected reduced stool output and hydration in a mouse model of acute constipation produced by scopolamine and in a chronically constipated mouse strain (C3H/HeJ). Direct comparison with the approved prosecretory drugs lubiprostone and linaclotide showed substantially greater intestinal fluid secretion with CFTRact-J027, as well as greater efficacy in a constipation model. As evidence to support efficacy in human constipation, CFTRact-J027 increased transepithelial fluid transport in enteroids generated from normal human small intestine. Also, CFTRact-J027 was rapidly metabolized in vitro in human hepatic microsomes, suggesting minimal systemic exposure upon oral administration. These data establish structure-activity and mechanistic data for phenylquinoxalinone CFTR activators, and support their potential efficacy in human constipation.

High-Potency Phenylquinoxalinone Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Activators

We previously identified phenylquinoxalinone CFTR_act-J027 (4) as a cystic fibrosis transmembrane conductance regulator (CFTR) activator with an EC₅₀ of ∼200 nM and demonstrated its therapeutic efficacy in mouse models of constipation. Here, structure-activity studies were done on 36 synthesized phenylquinoxalinone analogs to identify compounds with improved potency and altered metabolic stability. Synthesis of the phenylquinoxalinone core was generally accomplished by condensation of 1,2-phenylenediamines with substituted phenyloxoacetates. Structure-activity studies established, among other features, the privileged nature of a properly positioned nitro moiety on the 3-aryl group. Synthesized analogs showed improved CFTR activation potency compared to 4 with EC₅₀ down to 21 nM and with greater metabolic stability. CFTR activators have potential therapeutic indications in constipation, dry eye, cholestatic liver diseases, and inflammatory lung disorders.

One-Pot Synthesis of Benzo[4,5]imidazo[2,1-a]isoquinolines and Isoquinolino[3,4-b]quinoxalines via Tandem Cyclization Strategies

Two operationally simple one-pot protocols have been developed for the synthesis of amino-functionalized benzo[4,5]imidazo[2,1-a]isoquinolines and isoquinolino[3,4-b]quinoxalines. Optimization data and substrate scope for these atom-economical transformations, which engage commercially available o-phenylenediamines and o-cyanobenzaldehydes, are discussed.