Discovery of Novel, Orally Bioavailable Pyrimidine Ether-Based Inhibitors of ELOVL1.

In our efforts to identify novel small molecule inhibitors for the treatment of adrenoleukodystrophy (ALD), we conducted a high-throughput radiometric screen for inhibitors of elongation of very long chain fatty acid 1 (ELOVL1) enzyme. We developed a series of highly potent, central nervous system (CNS)-penetrant pyrimidine ether-based compounds with favorable pharmacokinetics culminating in compound 22. Compound 22 is a selective inhibitor of ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts and lymphocytes in vitro. Compound 22 reduced C26:0 lysophosphatidyl choline (LPC), a subtype of VLCFA, in the blood of ATP binding cassette transporter D1 (ABCD1) KO mice, a murine model of ALD to near wild-type levels. Compound 22 is a low-molecular-weight, potent ELOVL1 inhibitor that may serve as a useful tool for exploring therapeutic approaches to the treatment of ALD.

Discovery and Optimization of Pyrazole Amides as Inhibitors of ELOVL1.

Accumulation of very long chain fatty acids (VLCFAs) due to defects in ATP binding cassette protein D1 (ABCD1) is thought to underlie the pathologies observed in adrenoleukodystrophy (ALD). Pursuing a substrate reduction approach based on the inhibition of elongation of very long chain fatty acid 1 enzyme (ELOVL1), we explored a series of thiazole amides that evolved into compound 27─a highly potent, central nervous system (CNS)-penetrant compound with favorable in vivo pharmacokinetics. Compound 27 selectively inhibits ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts, lymphocytes, and microglia. In mouse models of ALD, compound 27 treatment reduced C26:0 VLCFA concentrations to near-wild-type levels in blood and up to 65% in the brain, a disease-relevant tissue. Preclinical safety findings in the skin, eye, and CNS precluded progression; the origin and relevance of these findings require further study. ELOVL1 inhibition is an effective approach for normalizing VLCFAs in models of ALD.

Discovery and Characterization of a Water-Soluble Prodrug of a Dual Inhibitor of Bacterial DNA Gyrase and Topoisomerase IV.

Benzimidazole 1 is the lead compound resulting from an antibacterial program targeting dual inhibitors of bacterial DNA gyrase and topoisomerase IV. With the goal of improving key drug-like properties, namely, the solubility and the formulability of 1, an effort to identify prodrugs was undertaken. This has led to the discovery of a phosphate ester prodrug 2. This prodrug is rapidly cleaved to the parent drug molecule upon both oral and intravenous administration. The prodrug achieved equivalent exposure of 1 compared to dosing the parent in multiple species. The prodrug 2 has improved aqueous solubility, simplifying both intravenous and oral formulation.

Potent inhibitors of LpxC for the treatment of Gram-negative infections.

In this paper, we present the synthesis and SAR as well as selectivity, pharmacokinetic, and infection model data for representative analogues of a novel series of potent antibacterial LpxC inhibitors represented by hydroxamic acid.

Pyridone methylsulfone hydroxamate LpxC inhibitors for the treatment of serious gram-negative infections.

The synthesis and biological activity of a new series of LpxC inhibitors represented by pyridone methylsulfone hydroxamate 2a is presented. Members of this series have improved solubility and free fraction when compared to compounds in the previously described biphenyl methylsulfone hydroxamate series, and they maintain superior Gram-negative antibacterial activity to comparator agents.

Differentiation of arrhythmia risk of the antibacterials moxifloxacin, erythromycin, and telithromycin based on analysis of monophasic action potential duration alternans and cardiac instability.

Antibacterial drugs are known to have varying degrees of cardiovascular liability associated with QT prolongation that can lead to the ventricular arrhythmia torsade de pointes. The purpose of these studies was to compare the assessment for the arrhythmogenic risk of moxifloxacin, erythromycin, and telithromycin. Each drug caused dose-dependent inhibition of the rapidly activating delayed rectifier potassium current encoded by the human ether-á-go-go-related gene (hERG) with IC20 concentrations of 31 microM (moxifloxacin), 21 microM (erythromycin), and 11 microM (telithromycin). These drugs were also evaluated in an anesthetized guinea pig model to measure changes in monophasic action potential duration (MAPD) and to quantify beat-to-beat alternations in MAPD during rapid ventricular pacing. Moxifloxacin dose dependently increased MAPD and caused a rate-dependent increase in alternans at the highest achieved free drug concentration (41 microM). Erythromycin also increased MAPD at its highest free drug concentration (58 microM), but alternans occurred at a relatively lower therapeutic multiple (13.9 microM), and the magnitude of alternans at higher concentrations was independent of pacing rate. Further analysis of the data showed that the beat-to-beat pattern of alternans with erythromycin was less stable than that with moxifloxacin and suggestive of greater arrhythmogenic liability. In contrast to erythromycin and moxifloxacin, telithromycin decreased both MAPD and alternans at the highest achievable drug concentration (7.9 microM). The relative risk at therapeutic concentrations is erythromycin>moxifloxacin>telithromycin and appears to be consistent with clinical observations of torsade de pointes in patients.

Altered AZT (3'-azido-3'-deoxythymidine) glucuronidation kinetics in liver microsomes as an explanation for underprediction of in vivo clearance: comparison to hepatocytes and effect of incubation environment.

Human liver microsomes are a reagent commonly used to predict human hepatic clearance of new chemical entities via phase 1 metabolism. Another common metabolic pathway, glucuronidation, can also be observed in human liver microsomes, although the scalability of this process has not been validated. In fact, several groups have demonstrated that clearance estimated from liver microsomes with UDP-glucuronic acid typically underpredicts the actual in vivo clearance more than 10-fold for compounds that are predominantly glucuronidated. In contrast, clearance predicted using human hepatocytes, for these same compounds, provides a more accurate assessment of in vivo clearance. We sought to characterize the kinetics of glucuronidation of the selective UGT2B7 substrate AZT (3'-azido-3'-deoxythymidine), a selective UGT2B7 substrate, in human liver microsomes (HLMs), recombinant UGT2B7, and human hepatocytes. Apparent Km values in these three preparations were 760, 490, and 87 microM with apparent Vmax values highest in hepatocytes. The IC50 for ibuprofen against AZT glucuronidation, when run at its Km concentration in HLMs and hepatocytes, was 975 and 170 microM respectively. Since incubation conditions have been shown to modulate glucuronidation rates, AZT glucuronidation was performed in various physiological and nonphysiological buffer systems, namely Tris, phosphate, sulfate, carbonate, acetate, human plasma, deproteinized human liver cytosol, and Williams E medium. The data showed that carbonate and Williams E medium, more physiologically relevant buffers, yielded the highest rates of AZT glucuronidation. Km observed in HLM/carbonate was 240 microM closer to that found in hepatocytes, suggesting that matrix differences might cause the kinetic differences observed between liver preparations. Caution should be exercised when extrapolating metabolic lability via glucuronidation or inhibition of UGT enzymes from human liver microsomes, since this system appears to underpredict the degree of lability or inhibition, respectively, due in part to an apparent decrease in substrate affinity.