Discovery of N-(6-(5-fluoro-2-(piperidin-1-yl)phenyl)pyridazin-3-yl)-1-(tetrahydro-2H-pyran-4-yl)methanesulfonamide as a brain-permeable and metabolically stable kynurenine monooxygenase inhibitor.

Kynurenine monooxygenase (KMO) is expected to be a good drug target to treat Huntington's disease (HD). This study presents the structure-activity relationship of pyridazine derivatives to find novel KMO inhibitors. The most promising compound 14 resolved the problematic issues of lead compound 1, i.e., metabolic instability and reactive metabolite-derived side-effects. Compound 14 exhibited high brain permeability and a long-lasting pharmacokinetics profile in monkeys, and neuroprotective kynurenic acid was increased by a single administration of 14 in R6/2 mouse brain. These results demonstrated 14 may be a potential drug candidate to treat HD.

N-(6-phenylpyridazin-3-yl)benzenesulfonamides as highly potent, brain-permeable, and orally active kynurenine monooxygenase inhibitors.

Huntington's disease (HD) is one of the serious neurodegenerative diseases and no disease modifiers are available to date. The correction of unbalanced kynurenine pathway metabolites may be useful to treat disease progression and kynurenine monooxygenase (KMO) is considered an ideal drug target. A couple of KMO inhibitors have been reported, but their brain permeability was very poor. We found pyridazinylsulfonamide as a novel lead compound, and it was optimized to the brain-permeable and highly potent KMO inhibitor 12, which was equipotent with CHDI-340246 and superior to CHDI-340246 in terms of brain penetration. Compound 12 was effective in R6/2 mice (HD model mice), i.e. neuroprotective kynurenic acid was increased, whereas neurotoxic 3-hydroxykynurenine was suppressed. In addition, impaired cognitive function was improved. Therefore, the brain-permeable KMO inhibitor was considered to be a disease modifier for HD treatment.

Bioconversion of FR901459, a novel derivative of cyclosporin A, by Lentzea sp. 7887.

FR901459, a product of the fungus Stachybotrys chartarum No. 19392, is a derivative of cyclosporin A (CsA) and a powerful immunosuppressant that binds cyclophilin. Recently, it was reported that CsA was effective against hepatitis C virus (HCV). However, FR901459 lacks active moieties, which are essential for synthesizing more potent and safer derivatives of this anti-HCV agent. Here we identified an actinomycete strain (designated 7887) that was capable of efficient bioconversion of FR901459. Structural elucidation of the isolated bioconversion products (1-7) revealed that compounds 1-4 were mono-hydroxylated at the position of 1-MeBmt or 9-MeLeu, whereas compounds 5-7 were bis-hydroxylated at both positions. The results of morphological and chemical characterization, as well as phylogenetic analysis of 16S ribosomal DNA (rDNA), suggested that strain 7887 belonged to the genus Lentzea. Comparison of the FR901459 conversion activity of strain 7887 with several other Lentzea strains revealed that although all examined strains metabolized FR901459, strain 7887 had a characteristic profile with respect to bioconversion products. Taken together, these findings suggest that strain 7887 can be used to derivative FR901459 to produce a chemical template for further chemical modifications that may provide more effective and safer anti-HCV drugs.