We speculated that oxidation of the electron

We speculated that oxidation of the electron-rich quinoline ring might contribute to the high rate of clearance, and compounds were prepared without the 7-methoxy group, and with a 7-F substituent in its place. Compounds without the 7-MeO substituent () showed reduced activity in both enzyme and cell. The two 7-F compounds (, ) did in fact show moderate in vivo clearance, but were also less potent. The 2,4-F example was only weakly active in our cell assay (4.2μM). The 2,3-Cl example was closer to the level of potency we felt was required (0.44μM in the cell), but still significantly less active than the corresponding 7-MeO Cholic acid sale . We had observed previously improved potency for 6-aminoquinolines when 7-MeO was replaced by 7-EtO. The 2,4-F analogue achieved both good in vitro activity, 0.23μM in the cell, and excellent in vivo PK. The 2,3-Cl compound had higher clearance in rats than the 2,4-F example, but was very potent in the cell assay (0.06μM). With a combination of good cell potency and encouraging PK, compounds and represented excellent advanced leads for further optimization of the series. We next explored a range of cyclic amines at the 6-position, with the goal of identifying compounds with the best overall balance of potency and PK, as determined by our mouse PD model. Sets of compounds were prepared with both 2,3-Cl aniline – (best in vitro potency) and 2,4-F aniline – (best physical properties and good PK). Data for these compounds is shown in . To assess the in vivo CSF-1R activity of the amidoquinolines, compounds were dosed orally in a mouse pharmacodynamic (PD) model. 3T3 cells were engineered to express human mutant full length CSF-1R (301–969) (3T3/CSF-1R in which the kinase activity was constitutively on. Female nude mice were implanted with 5×10 3T3/CSF-1R cells subcutaneously and grown in vivo until tumors were >250mm in size. Tumors were analyzed for pCSF-1R levels by ELISA 2 and 6h after dosing, and blood plasma samples were assessed for drug concentrations. Earlier compounds had been dosed at 50 or 100mpk, but the potency and other properties of these amidoquinolines allowed us to drop the screening dose to 25mpk. Compounds with 2,3-Cl aniline were typically ∼10-fold more potent in the cell assay than the 2,4-F aniline examples, but had higher levels of plasma protein binding, and higher rat in vivo clearance. The choice of amine at the 6-position had relatively little effect on cell potency, but a significant impact on physical properties and PK. Basic groups here typically resulted in compounds with a superior profile to those with neutral substituents such as morpholine (), or the piperazine amides (, ). Examples with both 2,3-Cl and 2,4-F anilines showed good PD activity out to 6h. Compounds were screened for their activity against the hERG channel, with the 2,3-Cl compounds more active here than the 2,4-F compounds. The homopiperazine examples (, , , ) showed increased hERG activity relative to the corresponding piperazines.