The goal of this study was to compare the reactions of alpha-acetoxy-N-nitrosopyrrolidine (alpha-acetoxyNPYR) and alpha-acetoxy-N-nitrosopiperidine (alpha-acetoxyNPIP) with deoxyguanosine (dG). alpha-AcetoxyNPYR and alpha-acetoxyNPIP are stable precursors to the alpha-hydroxynitrosamines which are formed metabolically from NPYR and NPIP. These alpha-hydroxynitrosamines are believed to be the proximate carcinogens of NPYR and NPIP. NPYR and NPIP, although structurally similar, have remarkably different carcinogenic properties, and a comparison of the reactions of their metabolically activated forms with dG and ultimately DNA could provide insights on their mechanisms of carcinogenicity. Reactions of alpha-acetoxyNPYR and alpha-acetoxyNPIP with dG were carried out at 37 degrees C and pH 7.0. The products were analyzed by HPLC and characterized by their spectral properties and by comparison to standards. In each reaction, one of the major products was a new type of dG adduct: N2-(tetrahydrofuran-2- yl)dG (THF-dG) from alpha-acetoxyNPYR and N2-(3,4,5,6-tetrahydro-2H-pyran-2-yl)dG (THP-dG) from alpha-acetoxyNPIP. THF-dG was synthesized independently by reaction of either 2-chlorotetrahydrofuran or 2,3-dihydrofuran with dG. Similarly, THP-dG was prepared by reaction of 2-chloro-3,4,5,6-tetrahydro-2H-pyran with dG. The structures of THF-dG and THP-dG were established by their UV and 1H-NMR spectra. THF-dG was less stable than THP-dG, but could be readily converted to a stable derivative, N2-(4-hydroxybutyl)dG, by reaction with NaBH4. THF-dG and THP-dG were converted to dG and 2-hydroxytetrahydrofuran or 2-hydroxy-3,4,5,6-tetrahydro-2H-pyran, respectively, upon neutral thermal or acid hydrolysis. This reaction was found to be reversible, with the adducts being produced in substantial amounts by reaction of 2-hydroxytetrahydrofuran or 2-hydroxy-3,4,5,6-tetrahydro-2H-pyran with dG. The latter reaction accounts for part of the THF-dG and THP-dG produced from the alpha-acetoxynitrosamines; stable oxonium ion-derived electrophiles may also be involved in the formation of THF-dG and THP-dG. Comparisons of the yields of various adducts in the reaction of alpha-acetoxyNPYR and alpha-acetoxyNPIP with dG showed some major differences. Whereas yields of THF-dG and THP-dG were similar, adducts formed from open chain diazonium ion or related intermediates were formed more extensively from alpha-acetoxyNPYR than from alpha-acetoxyNPIP. Adducts formed from enal products of the two nitrosamines were also different. Adduct formation as characterized in this study may account for some of the contrasting carcinogenic properties of NPYR and NPIP.

Leukocyte recruitment of sites of inflammation and tissue injury involves leukocyte rolling along the endothelial wall, followed by firm adherence of the leukocyte, and finally transmigration of the leukocyte across cell junctions into the underlying tissue. The initial rolling step is mediated by the interaction of leukocyte glycoproteins containing active moieties such as sialyl Lewisx (sLex) with P-selectin expressed on endothelial cells. Consequently, inhibition of this interaction by means of a small molecule P-selectin antagonist is an attractive strategy for the treatment of inflammatory diseases such as arthritis. High-throughput screening of the Wyeth chemical library identified the quinoline salicylic acid class of compounds (1) as antagonists of P-selectin, with potency in in vitro and cell-based assays far superior to that of sLex. Through iterative medicinal chemistry, we identified analogues with improved P-selectin activity, decreased inhibition of dihydrooratate dehydrogenase, and acceptable CYP profiles. Lead compound 36 was efficacious in the rat AIA model of rheumatoid arthritis.

The six-membered heterocyclic nitrosamine N-nitrosopiperidine (NPIP) is an esophageal carcinogen in the rat whereas its five-membered homologue N-nitrosopyrrolidine (NPYR) is a liver carcinogen. These contrasting organo-specificities may be due to differences between NPIP and NPYR in their metabolic activation to intermediates which bind to DNA. Previous studies have shown that the metabolic activation of NPYR to DNA binding products occurs through alpha-hydroxylation. DNA adducts of NPIP have not been characterized. Therefore, we began our studies by investigating the reaction of alpha-acetoxyNPIP with deoxyguanosine. A major adduct, detected by high-performance liquid chromatography with UV detection, was characterized by its UV, 1H-NMR, and MS as 7-(2-oxopropyl)-5,9-dihydro-9-oxo-3-beta-D-deoxyribofuranosylimidazo+ ++[1,2-a] purine. This 7-(2-oxopropyl)-substituted 1,N2-ethenodeoxyguanosine adduct was formed by reaction of 4-oxo-2-pentenal (3-acetylacrolein) with the 1 and N2 positions of deoxyguanosine. Since the formation of 4-oxo-2-pentenal from alpha-acetoxyNPIP was unexpected, we investigated the solvolysis of alpha-acetoxyNPIP in more detail. Major products formed in incubations of alpha-acetoxyNPIP for 7-24 h in phosphate buffer (pH 7.0) at 37 degrees C included 4-oxo-2-pentenal (11-21% yield), 4-hydroxypentanal (18-22%), and 5-hydroxypentanal (27-29%). The formation of 4-oxo-2-pentenal required O2. The results of this study demonstrate some unique features of the chemistry of alpha-acetoxyNPIP and the resulting deoxyguanosine adducts which may be related to the carcinogenic activity of NPIP.

We studied the reactions with DNA of alpha-acetoxy-N-nitrosopyrrolidine (alpha-acetoxyNPYR) and alpha-acetoxy-N-nitrosopiperidine (alpha-acetoxyNPIP) in order to obtain more information on adduct formation by metabolic activation via alpha-hydroxylation of two cyclic nitrosamines, N-nitrosopyrrolidine (NPYR) and N-nitrosopiperidine (NPIP). Enzyme hydrolysis and HPLC analysis of DNA that had been reacted with unlabeled, [14C]-, or [3H]alpha- acetoxyNPYR permitted the positive identification of N2-(tetrahydrofuran-2-yl)deoxyguanosine (THF-dG). It was identified by comparison of its UV spectrum and retention time to those of a standard, by conversion upon NaBH4 treatment to N2-(4-hydroxybutyl)deoxyguanosine, and by neutral thermal hydrolysis to 2-hydroxytetrahydrofuran (THF-OH). The levels of THF-dG in DNA exceeded that of other adducts of alpha-acetoxyNPYR. Reaction of alpha-acetoxyNPIP with DNA followed by enzyme hydrolysis and HPLC analysis resulted in the positive identification of two diastereomers of N2-(3,4,5,6-tetrahydro-2H-pyran-2-yl)deoxyguanosine (THP-dG) by comparison of their retention times and UV spectra to those of standards. The levels of THP-dG were similar to those of THF-dG formed from alpha-acetoxyNPYR. Neutral thermal hydrolysis of DNA that had been reacted with alpha-acetoxyNPIP produced 2-hydroxy-3,4,5,6-tetrahydro-2H-pyran (THP-OH). Studies on the mechanism of formation of THF-dG and THP-dG indicated that stable cyclic oxonium ion-derived electrophiles could be their major precursors. Our data provide the first evidence for the formation of cyclic oxonium ion-derived DNA adducts from cyclic nitrosamines and indicate some potential differences in DNA binding between alpha-acetoxyNPYR and alpha-acetoxyNPIP.(ABSTRACT TRUNCATED AT 250 WORDS)

Epacadostat (EPA, INCB024360) is a first-in-class, orally active, investigational drug targeting the enzyme indoleamine 2,3-dioxygenase 1 (IDO1). In Phase I studies, EPA has demonstrated promising clinical activity when used in combination with checkpoint modulators. When the metabolism of EPA was investigated in humans, three major, IDO1-inactive, circulating plasma metabolites were detected and characterized: M9, a direct O-glucuronide of EPA; M11, an amidine; and M12, N-dealkylated M11. Glucuronidation of EPA to form M9 is the dominant metabolic pathway, and in vitro, this metabolite is formed by UGT1A9. However, negligible quantities of M11 and M12 were detected when EPA was incubated with a panel of human microsomes from multiple tissues, hepatocytes, recombinant human cytochrome P450s (P450s), and non-P450 enzymatic systems. Given the reductive nature of M11 formation and the inability to define its source, the role of gut microbiota was investigated. Analysis of plasma from mice dosed with EPA following pretreatment with either antibiotic (ciprofloxacin) to inhibit gut bacteria or 1-aminobenzotriazole (ABT) to systemically inhibit P450s demonstrated that gut microbiota is responsible for the formation of M11. Incubations of EPA in human feces confirmed the role of gut bacteria in the formation of M11. Further, incubations of M11 with recombinant P450s showed that M12 is formed via N-dealkylation of M11 by CYP3A4, CYP2C19, and CYP1A2. Thus, in humans three major plasma metabolites of EPA were characterized: two primary metabolites, M9 and M11, formed directly from EPA via UGT1A9 and gut microbiota, respectively, and M12 formed as a secondary metabolite via P450s from M11.