The cellular enzyme inhibition for 1, 13 and setileuton are diminished relative to the isolated-enzyme inhibitor values. This result, along with other analogues failing to display high potency, could indicate poor permeability, plasma protein binding, nonspecific interactions or metabolism of the inhibitors by the cell. The Reversine Aurora Kinase inhibitor determination that the reductive phenylenediamine core was the key potency component and that the addition of large functionalities to either side of the phenylenediamine core was well tolerated led us to consider the similarity between the phenylenediamine chemotype and ketoconazole. Ketoconazole is a CYP51 inhibitor with an azole moiety that targets the active site heme and is a potent antifungal medication. In addition, ketoconazole was previously determined to inhibit 5-LOX and have anti-inflammatory properties, although weakly. Considering the similarity of ketoconazole to our chemotype, we hypothesized that by adding the phenylenediamine core to ketoconazole, we could improve its 5-LOX potency by making it a reductive inhibitor and thus increasing its anti-inflammatory properties. We subsequently modified the structure of ketoconazole to include a phenylenediamine core to generate a novel compound, ketaminazole and found that its potency against 5- LOX increased over 70-fold compared to ketoconazole and that it was a reductive inhibitor, as seen by its activity in the pseudoperoxidase assay. The selectivity of the ketaminazole was also investigated and found to preferentially inhibit 5-LOX over 100 times Bortezomib purchase better than that of 12-LOX, 15-LOX-1, 15-LOX-2, COX-1 and COX-2. This is most likely due to the large active site of 5-LOX compared to the other human LOX isozymes. Ketaminazole was also tested in whole human blood and shown to display cellular activity. Like the smaller phenylenediamine inhibitors, ketaminazole��s cellular potency is lower relative to its in vitro potency, displaying an approximately 20-fold reduction. The magnitude of the potency in whole blood is not consistent between all the phenylenediamine inhibitors tested. This indicates that the structural differences between the phenylenediamine inhibitors have an effect on their cellular potency, supporting the hypothesis that cellular factors, other than the phenylenediamine core, are important. Gratifyingly, ketaminazole displayed a better potency against 5-LOX in whole blood relative to ketoconazole, however, the magnitude of this difference was not as great as their in vitro difference. This is surprising since their only structural difference is the substitution of an amine for the ether linkage. It could be that the polarity change of the inhibitors changes their cellular uptake or that the reductive state of the ketaminazole is being compromised in the cell.