Smriti Khanna

Isocytosine-based inhibitors of xanthine oxidase: Design, synthesis, SAR, PK and in vivo efficacy in rat model of hyperuricemia

Structure-activity relationship studies were carried out for lead generation following structure-guided design approach from an isocytosine scaffold identified earlier for xanthine oxidase inhibition. A 470-fold improvement in in vitro IC(50) was obtained in the process. Five most potent compounds with nanomolar IC(50) values were selected for pharmacokinetics and in vivo experiments. The best compound showed good in vivo activity when administered intraperitoneally but was not active by oral route. The results suggest that improvement in oral exposure could improve the in vivo efficacy of this series.

Identification of novel isocytosine derivatives as xanthine oxidase inhibitors from a set of virtual screening hits.

In recent years, xanthine oxidase has emerged as an important target not only for gout but also for cardiovascular and metabolic disorders involving hyperuricemia. Contrary to popular belief, recent clinical trials with uricosurics have demonstrated that enhanced excretion of uric acid is, by itself, not adequate to treat hyperuricemia; simultaneous inhibition of production of uric acid by inhibition of xanthine oxidase is also important. Virtual screening of in-house synthetic library followed by in vitro and in vivo testing led to the identification of a novel scaffold for xanthine oxidase inhibition. In vitro activity results corroborated the results from molecular docking studies of the virtual screening hits. The isocytosine scaffold maintains key hydrogen bonding and pi-stacking interactions in the deep end of the xanthine-binding pocket, which anchors it in an appropriate pose to inhibit binding of xanthine and shows promise for further lead optimization using structure-based drug design approach.

Regioselective aluminium chloride induced heteroarylation of pyrrolo[1,2-b]pyridazines: its scope and application☆

Abstract We describe a detailed study on the novel synthesis of 6,7-disubstituted pyrrolo[1,2-b]pyridazines through AlCl3 induced C–C bond formation reactions. A wide variety of 6-aryl substituted azolopyridazines was reacted with 3,6-dichloropyridazine to give 7-pyridazinyl substituted pyrrolopyridazines regioselectively in good to excellent yield. The mechanism and regiochemistry of the reaction along with applications of the methodology are discussed.

Lead optimization of isocytosine-derived xanthine oxidase inhibitors

We report our attempts at improving the oral efficacy of low-nanomolar inhibitors of xanthine oxidase from isocytosine series through chemical modifications. Our lead compound had earlier shown good in vivo efficacy when administered intraperitoneally but not orally. Several modifications are reported here which achieved more than twofold improvement in exposure. A compound with significant improvement in oral efficacy was also obtained.

Cyclopentyl-pyrimidine based analogues as novel and potent IGF-1R inhibitor

A series of novel 2-amino-4-pyrazolecyclopentylpyrimidines have been prepared and evaluated as IGF-1R tyrosin kinase inhibitors. The in vitro activity was found to depend strongly on the substitution pattern in the 2- amino ring, 4-pyrazolo moieties and size of fused saturated ring with the central pyrimidine core. A stepwise optimization by combination of active fragments led to discovery of compound 6f and 6k, two structures with IGF-1R IC50 of 20 nM and 10 nM, respectively. 6f was further profiled for its anti cancer activity across various cell lines and pharmacokinetic studies in Sprague Dawley rats.