Synthesis and characterization of 11C-labeled fluoroclorgyline: a monoamine oxidase A specific inhibitor for positron emission tomography

Clorgyline Analogs Synergize with Azoles against Drug Efflux in Candida auris

Concern about the global emergence of multidrug-resistant fungal pathogens led us to explore the use of combination therapy to combat azole resistance in Candida auris. Clorgyline had previously been shown to be a multi-target inhibitor of Cdr1 and Mdr1 efflux pumps of Candida albicans and Candida glabrata. A screen for antifungal sensitizers among synthetic analogs of Clorgyline detected interactions with the C. auris efflux pump azole substrates Posaconazole and Voriconazole. Of six Clorgyline analogs, M19 and M25 were identified as potential sensitizers of azole resistance. M19 and M25 were found to act synergistically with azoles against resistant C. auris clade I isolates and recombinant Saccharomyces cerevisiae strains overexpressing C. auris efflux pumps. Nile Red assays with the recombinant strains showed M19 and M25 inhibited the activity of Cdr1 and Mdr1 efflux pumps that are known to play key roles in azole resistance in C. auris clades I, III, and IV. While Clorgyline, M19 and M25 uncoupled the Oligomycin-sensitive ATPase activity of Cdr1 from C. albicans and C. auris, their mode of action is yet to be fully elucidated. The experimental combinations described herein provides a starting point to combat azole resistance dominated by overexpression of CauCdr1 in C. auris clades I and IV and CauMdr1 in C. auris clade III.

Positron emission tomography quantification of [11C]-harmine binding to monoamine oxidase-A in the human brain

This article describes the kinetic modeling of [(11)C]-harmine binding to monoamine oxidase A (MAO-A) binding sites in the human brain using positron emission tomography (PET). Positron emission tomography studies were performed in healthy volunteers at placebo conditions and after treatment with clinical doses of moclobemide. In either condition, a two-tissue compartment model (2CM) provided better fits to the data than a one-tissue model. Estimates of k(3)/k(4) values from an unconstrained 2CM were highly variable. In contrast, estimates of the specifically bound radioligand distribution volume (DV(B)) from an unconstrained 2CM were exceptionally stable, correlated well with the known distribution of MAO-A in the brain (cerebellum <frontal cortex approximately putamen <temporal cortex approximately cingulate <thalamus) and thus provided reliable indices of MAO-A density. Total distribution volume (DV) values were also highly stable and not different from those estimated with the Logan approach. Fixing the DV of free and nonspecifically bound radiotracer (DV(F + NS)) or coupling DV(F + NS) between brain regions enabled more stable estimates of k(3)/k(4) as compared with an unconstrained 2CM. Moclobemide treatment leads to a 64% to 79% MAO-A blockade across brain regions, a result that supports the specificity of [(11)C]-harmine binding to MAO-A. The stability and reliability of DV(B) values obtained from an unconstrained 2CM, together with the computational simplicity associated with this method, support the use of DV(B) as an appropriate outcome measure for [(11)C]-harmine. These results indicate the suitability of using [(11)C]-harmine for quantitative evaluation of MAO-A densities using PET and should enable further studies of potential MAO-A dysregulation in several psychiatric and neurologic illnesses.