The saturated carbocyclic derivatives pyrazoles M and M and
The saturated carbocyclic derivatives, pyrazoles (2.5μM and 5.2μM) and (9.0μM and 2.5μM), provided little improvement in potency when compared to the linear alkyl derivatives, whereas the C5-phenyl derivative (0.31μM and 0.43μM) showed promise as a scaffold for further structural modifications. In this regard, a positional scan of a variety of functional groups on the phenyl ring system of exposed a tight binding pocket within this region of the molecule. It was discovered that phenyl rings bearing small alkyl groups or halogens were tolerated in this locale. As illustrated in , the methyl substituted ring systems (11μM and 16μM) and (4.2μM and 7.7μM) showed modest affinity for the receptor across both species, while halogen substitution about the phenyl ring showed improved in vitro potency. In particular, the placement of either a fluoro or chloro group in the 3-position of the phenyl ring as in (0.14μM and 0.29μM) and (0.08μM and 0.14μM) resulted in a significant improvement in potency. Whereas, substitution of a chloro group in either the 2 or 4-position as in (3.1μM and 1.9μM) and (4.0μM and 5.0μM) or a fluoro group as in (0.34μM and 0.41μM) and (1.7μM and 2.7μM) provided only a marginal improvement in potency. Amongst the disubstituted derivatives, the 3,5-fluoro derivative (0.7μM and 0.7μM) demonstrated improved affinity over the 2,4-difluoro derivative (1.6μM and 2.4μM), 2,5-derivative (0.85μM and 0.76μM) 3,4-derivative (0.52μM and 0.61μM) and 2,3-derivative (0.09μM and 0.14μM). Further fluoro substitution, as in enantiomer of the 2,3,5-trifluoro derivative proved to be the most potent IKK-16 hydrochloride mg in the C5-aryl-series. In order to set the stage for in vivo analysis, mouse pharmacokinetics (mPK) of lead candidates were investigated (). In the alkyl series, -propyl derivative showed a lower clearance (30mL/kg/min), longer half life (2.9h), and an improved bioavailability (51%). when compared with niacin. In contrast, compound , with better in vitro affinity than , demonstrated an inferior mPK profile when compared with . Within the aryl series of molecules, the fluoro-derivative showed improved mPK with good bioavailability (57%), lower clearance (47mL/kg/min) and a longer half-life (1.8h) when compared with niacin. Similarly, the 2,3,5-trifluoro-derivative showed a longer half-life (2.4h) and lower clearance (27mL/kg/min) with a modest bioavailability (10%). With a promising group of GPR109a agonists in hand, we were eager to investigate this new series of C5-substituted pyrazole–tetrazoles in an in vivo setting. In this effort, we chose to explore the pharmacology of in our mouse pFFA and mouse vasodilation assay. As illustrated in , six male C57 B1/6 mice were each dosed at 10mpk for 15min with and compared to mice dosed 100mpk with niacin for an effect on plasma free-fatty acids. In the case of compound , we observed a characteristic 24% reduction in plasma free fatty acid levels, while niacin, dosed at 100mpk, showed a characteristic 58% reduction of plasma free fatty acids. Having demonstrated the ability of agonist to effectively lower plasma free fatty acids in our mouse pharmacodynamics model, we proceeded to measure the cutaneous vasodilation effect of on male C57 B1/6 mice, as a surrogate for the flushing side effect experienced with niacin treatment. In this effort, compound , administered to 8 mice at 30mpk for 15min monitored with a laser doppler imager, showed no evidence of cutaneous flushing (). While nicotinic acid (NA), administered in 10 mice at 30mpk showed, on average, a characteristic 80% change in perfusion, typical of a flushing response in the mouse. In summary, we have identified a new class of C5-alkyl and aryl-pyrazole–tetrazoles that act as agonists of GPR109a. We proceeded to show that selected members of this family of compounds have improved mouse pharmacokinetic profiles when compared to niacin. Most notably, as part of an effort to identify and develop a flush-free niacin-like agonist of GPR109a, we have shown that agonist effectively reduces plasma free-fatty acids without eliciting a niacin-like flush in our mouse model. Current efforts are focused on further pre-clinical validation of the pyrazole–tetrazole series of GPR109a agonists.