The AMP-activated protein kinase (AMPK) is a potential therapeutic target for metabolic diseases based on its reported actions in the liver and skeletal muscle. We evaluated two distinct direct activators of AMPK: a non-selective activator of all AMPK complexes, PF-739, and an activator selective for AMPK β1-containing complexes, PF-249. In cells and animals, both compounds were effective at activating AMPK in hepatocytes, but only PF-739 was capable of activating AMPK in skeletal muscle. In diabetic mice, PF-739, but not PF-249, caused a rapid lowering of plasma glucose levels that was diminished in the absence of skeletal muscle, but not liver, AMPK heterotrimers and was the result of an increase in systemic glucose disposal with no impact on hepatic glucose production. Studies of PF-739 in cynomolgus monkeys confirmed translation of the glucose lowering and established activation of AMPK in skeletal muscle as a potential therapeutic approach to treat diabetic patients.

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1 Pentamidine, an antiprotozoal agent, has been traditionally known to cause QT prolongation and arrhythmias; however, its ionic mechanism has not been illustrated. 2 In a stable HEK-293 cell line, we observed a concentration-dependent inhibition of the hERG current with an IC 50 of 252 mM. 3 In freshly isolated guinea-pig ventricular myocytes, pentamidine showed no effect on the L-type calcium current at concentrations up to 300 mM, with a slight prolongation of the action potential duration at this concentration. 4 Since the effective concentrations of pentamidine on the hERG channel and APD were much higher than clinically relevant exposures (B1 mM free or lower), we speculated that this drug might not prolong the QT interval through direct inhibition of I Kr channel. We therefore incubated hERG-HEK cells in 1 and 10 mM pentamidine-containing media (supplemented with 10% serum) for 48 h, and examined the hERG current densities in the vehicle control and pentamidine-treated cells. 5 In all, 36 and 85% reductions of the current densities were caused by 1-and 10-mM pentamidine treatment (Po0.001 vs control), respectively. A similar level of reduction of the hERG polypeptides and a reduced intensity of the hERG protein on the surface membrane in treated cells were observed by Western blot analysis and laser-scanning confocal microscopy, respectively. 6 Taken together, our data imply that chronic administration of pentamidine at clinically relevant exposure reduces the membrane expression of the hERG channel, which may most likely be the major mechanism of QT prolongation and torsade de pointes reported in man.

It is hypothesized that selective muscarinic M1 subtype activation could be a strategy to provide cognitive benefits to schizophrenia and Alzheimer's disease patients while minimizing the cholinergic side effects observed with nonselective muscarinic orthosteric agonists. Selective activation of M1 with a positive allosteric modulator (PAM) has emerged as a new approach to achieve selective M1 activation. This manuscript describes the development of a series of M1-selective pyridone and pyridine amides and their key pharmacophores. Compound 38 (PF-06767832) is a high quality M1 selective PAM that has well-aligned physicochemical properties, good brain penetration and pharmacokinetic properties. Extensive safety profiling suggested that despite being devoid of mAChR M2/M3 subtype activity, compound 38 still carries gastrointestinal and cardiovascular side effects. These data provide strong evidence that M1 activation contributes to the cholinergic liabilities that were previously attributed to activation of the M2 and M3 receptors.

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