CYP2C9 and 3A4 play opposing roles in bioactivation and detoxification of diphenylamine NSAIDs.

Diphenylamine NSAIDs are taken frequently for chronic pain conditions, yet their use may potentiate hepatotoxicity risks through poorly characterized metabolic mechanisms. Our previous work revealed that seven marketed or withdrawn diphenylamine NSAIDs undergo bioactivation into quinone-species metabolites, whose reaction specificities depended on halogenation and the type of acidic group on the diphenylamine. Herein, we identified cytochromes P450 responsible for those bioactivations, determined reaction specificities, and estimated relative contributions of enzymes to overall hepatic bioactivations and detoxifications. A qualitative activity screen revealed CYP2C8, 2C9, 2C19, and 3A4 played roles in drug bioactivation. Subsequent steady-state studies with recombinant CYPs recapitulated the importance of halogenation and acidic group type on bioactivations but importantly, showed patterns unique to each CYP. CYP2C9, 2C19 and 3A4 bioactivated all NSAIDs with CYP2C9 dominating all possible bioactivation pathways. For each CYP, specificities for overall oxidative metabolism were not impacted significantly by differences in NSAID structures but the values themselves differed among the enzymes such that CYP2C9 and 3A4 were more efficient than others. When considering hepatic CYP abundance, CYP2C9 almost exclusively accounted for diphenylamine NSAID bioactivations, whereas CYP3A4 provided a critical counterbalance favoring their overall detoxification. Preference for either outcome would depend on molecular structures favoring metabolism by the CYPs as well as the influence of clinical factors altering their expression and/or activity. While focused on NSAIDs, these findings have broader implications on bioactivation risks given the expansion of the diphenylamine scaffold to other drug classes such as targeted cancer therapeutics.

Impacts of diphenylamine NSAID halogenation on bioactivation risks.

Diphenylamine NSAIDs are highly prescribed therapeutics for chronic pain despite causing symptomatic hepatotoxicity through mitochondrial damage in five percent of patients taking them. Differences in toxicity are attributed to structural modifications to the diphenylamine scaffold rather than its inherent toxicity. We hypothesize that marketed diphenylamine NSAID substituents affect preference and efficiency of bioactivation pathways and clearance. We parsed the FDA DILIrank hepatotoxicity database and modeled marketed drug bioactivation into quinone-species metabolites to identify a family of seven clinically relevant diphenylamine NSAIDs. These drugs fell into two subgroups, i.e., acetic acid and propionic acid diphenylamines, varying in hepatotoxicity risks and modeled bioactivation propensities. We carried out steady-state kinetic studies to assess bioactivation pathways by trapping quinone-species metabolites with dansyl glutathione. Analysis of the glutathione adducts by mass spectrometry characterized structures while dansyl fluorescence provided quantitative yields for their formation. Resulting kinetics identified four possible bioactivation pathways among the drugs, but reaction preference and efficiency depended upon structural modifications to the diphenylamine scaffold. Strikingly, diphenylamine dihalogenation promotes formation of quinone metabolites through four distinct metabolic pathways with high efficiency, whereas those without aromatic halogen atoms were metabolized less efficiently through two or fewer metabolic pathways. Overall metabolism of the drugs was comparable with bioactivation accounting for 4-13% of clearance. Lastly, we calculated daily bioload exposure of quinone-species metabolites based on bioactivation efficiency, bioavailability, and maximal daily dose. The results revealed stratification into the two subgroups; propionic acid diphenylamines had an average four-fold greater daily bioload compared to acetic acid diphenylamines. However, the lack of sufficient study on the hepatotoxicity for all drugs prevents further correlative analyses. These findings provide critical insights on the impact of diphenylamine bioactivation as a precursor to hepatotoxicity and thus, provide a foundation for better risk assessment in drug discovery and development.

Towards the next generation of dual Bcl-2/Bcl-xL inhibitors.

Structural modifications of the left-hand side of compound 1 were identified which retained or improved potent binding to Bcl-2 and Bcl-xL in in vitro biochemical assays and had strong activity in an RS4;11 apoptotic cellular assay. For example, sulfoxide diastereomer 13 maintained good binding affinity and comparable cellular potency to 1 while improving aqueous solubility. The corresponding diastereomer (14) was significantly less potent in the cell, and docking studies suggest that this is due to a stereochemical preference for the RS versus SS sulfoxide. Appending a dimethylaminoethoxy side chain (27) adjacent to the benzylic position of the biphenyl moiety of 1 improved cellular activity by approximately three-fold, and this activity was corroborated in cell lines overexpressing Bcl-2 and Bcl-xL.

Will disruptive mood dysregulation disorder reduce false diagnosis of bipolar disorder in children?

OBJECTIVES: The frequency of diagnosis of bipolar disorder has risen dramatically in children and adolescents. The DSM-V Work Group has suggested a new diagnosis termed disruptive mood dysregulation disorder (DMDD) (formerly temper dysregulation disorder with dysphoria) to reduce the rate of false diagnosis of bipolar disorder in young people. We sought to determine if the application of the proposed diagnostic criteria for DMDD would reduce the rate of diagnosis of bipolar disorder in children. PATIENTS AND METHODS: Eighty-two consecutively hospitalized children, ages 5 to 12 years, on a children's inpatient unit were rigorously diagnosed using admission interviews of the parents and the child, rating scales, and observation over the course of hospitalization. RESULTS: Overall, 30.5% of inpatient children met criteria for DMDD by parent report, and 15.9% by inpatient unit observation. Fifty-six percent of inpatient children had parent-reported manic symptoms. Of those, 45.7% met criteria for DMDD by parent-report, though only 17.4% did when observed on the inpatient unit. CONCLUSION: Although DMDD does decrease the rate of diagnosis of bipolar disorder in children, how much depends on whether history or observation is used.

In vitro and in vivo evaluation of O-alkyl derivatives of tramadol.

Tramadol is a centrally acting opioid analgesic structurally related to codeine and morphine. O-Alkyl, N-desmethyl, and non-phenol containing derivatives of tramadol were synthesized to probe their effect on metabolic stability and both in vitro and in vivo potency.

First application of tunable alkyl or aryl sulfinamides to the stereoselective synthesis of a chiral amine: asymmetric synthesis of (R)-didesmethylsibutramine ((R)-DDMS) using (R)-triethylmethylsulfinamide ((R)-TESA).

A highly diastereoselective addition of i-BuLi to a triethylmethylsulfinamide derived aldimine was used as the key step in the first asymmetric synthesis of (R)-didesmethylsibutramine, a metabolite of sibutramine for the potential treatment of CNS disorders. [reaction: see text]

Properly designed modular asymmetric synthesis for enantiopure sulfinamide auxiliaries from N-sulfonyl-1,2,3-oxathiazolidine-2-oxide agents.

Simple and practical asymmetric synthesis of functionally differentiated aminoindanol based endo-N-sulfonyl 1,2,3-oxathiazolidine-2-oxide as sulfinyl transfer agents are developed. The importance of these new and unique sulfinyl transfer reagents are exemplified by the expedient production of several sulfinamide ligands, including either enantiomer of (R)-tert-butanesulfinamide in excellent yields and enantiopurities.