An in vitro glucuronidation assay was used to optimize a series of @entity36174 -containing @entity1437 inhibitors for metabolic stability. The glucuronidation of these compounds in @entity5434 microsomes followed Michaelis-Menten kinetics allowing calculation of V(max) and K(M). The V(max) values ranged from 0.02 to 7.9 nmol/min/mg microsomal protein, a 400-fold difference, whereas K(M) ranged from 204 to 2500 microM, only a 12-fold difference. In vitro intrinsic clearance values (CL(int) were calculated for 18 compounds tested in the kinetic assay and compared with the in vivo plasma clearance (CL(p)) calculated from intravenous studies done in @entity5434 . These initial results suggested a relationship between the in vitro CL(int) and in vivo duration as defined by CL(p). A more rapid in vitro assay was developed in a 96-well format using a single concentration of substrate (100 microM) from which a glucuronidation rate was calculated. The results from this assay for 40 compounds correlated with in vivo plasma clearance (r = 0.57). This more efficient assay was used to test more than 100 compounds and develop structure-metabolism relationships based on metabolic stability and improved duration. The culmination of this effort contributed to the discovery of @entity70339 , a @entity1437 inhibitor with in vivo duration in monkey improved 40-fold over thefirst generation inhibitor. Further studies performed in @entity1 liver microsomes demonstrated a similar trend that was corroborated by the 8-fold increase in duration after oral dosing in @entity1 observed with @entity70339 .

Improving the in vivo duration of XXXX inhibitors: application of an in vitro glucuronosyltransferase assay.

@entity1 :: ('9606', 'Species') :: ['humans', 'human'] @entity1437 :: ('240', 'Gene') :: ['5-lipoxygenase'] @entity70339 :: ('MESH:C096921', 'Chemical') :: ['ABT-761'] @entity5434 :: ('9541', 'Species') :: ['cynomolgus monkey', 'cynomolgus monkeys'] @entity36174 :: ('CHEBI:44423', 'Chemical') :: ['N-hydroxyurea']
@entity1437 :: (240,Gene) :: ['5-lipoxygenase']
