David Festus Charles Moffat

Drug Targeting to Monocytes and Macrophages Using Esterase-Sensitive Chemical Motifs

The therapeutic and toxic effects of drugs are often generated through effects on distinct cell types in the body. Selective delivery of drugs to specific cells or cell lineages would, therefore, have major advantages, in particular, the potential to significantly improve the therapeutic window of an agent. Cells of the monocyte-macrophage lineage represent an important target for many therapeutic agents because of their central involvement in a wide range of diseases including inflammation, cancer, atherosclerosis, and diabetes. We have developed a versatile chemistry platform that is designed to enhance the potency and delivery of small-molecule drugs to intracellular molecular targets. One facet of the technology involves the selective delivery of drugs to cells of the monocyte-macrophage lineage, using the intracellular carboxylesterase, human carboxylesterase-1 (hCE-1), which is expressed predominantly in these cells. Here, we demonstrate selective delivery of many types of intracellularly targeted small molecules to monocytes and macrophages by attaching a small esterase-sensitive chemical motif (ESM) that is selectively hydrolyzed within these cells to a charged, pharmacologically active drug. ESM versions of histone deacetylase (HDAC) inhibitors, for example, are extremely potent anticytokine and antiarthritic agents with a wider therapeutic window than conventional HDAC inhibitors. In human blood, effects on monocytes (hCE-1-positive) are seen at concentrations 1000-fold lower than those that affect other cell types (hCE-1-negative). Chemical conjugates of this type, by limiting effects on other cells, could find widespread applicability in the treatment of human diseases where monocyte-macrophages play a key role in disease pathology.

Discovery of 2-(6-{[(6-Fluoroquinolin-2-yl)methyl]amino}bicyclo[3.1.0]hex-3-yl)-N-hydroxypyrimidine-5-carboxamide (CHR-3996), a Class I Selective Orally Active Histone Deacetylase Inhibitor

A novel series of HDAC inhibitors demonstrating class I subtype selectivity and good oral bioavailability is described. The compounds are potent enzyme inhibitors (IC₅₀ values less than 100 nM), and improved activity in cell proliferation assays was achieved by modulation of polar surface area (PSA) through the introduction of novel linking groups. Employing oral pharmacokinetic studies in mice, comparing drug levels in spleen to plasma, we selected compounds that were tested for efficacy in human tumor xenograft studies based on their potential to distribute into tumor. One compound, 21r (CHR-3996), showed good oral activity in these models, including dose-related activity in a LoVo xenograft. In addition 21r showed good activity in combination with other anticancer agents in in vitro studies. On the basis of these results, 21r was nominated for clinical development.

4-pyridin-5-yl-2-(3,4,5-trimethoxyphenylamino)pyrimidines : Potent and selective inhibitors of ZAP 70

Activation of the tyrosine kinase ZAP 70 has been shown to be crucial to the transduction of the T-cell receptor signalling pathway, which leads ultimately to proliferation, cytokine gene expression and T-cell effector functions. A series of 2-phenylaminopyrimidines have been identified as potent and selective inhibitors of ZAP 70.

Design and synthesis of novel pyrimidine hydroxamic acid inhibitors of histone deacetylases.

Inhibition of histone deacetylase activity represents a promising new modality in the treatment of a number of cancers. A novel HDAC series demonstrating inhibitory activity in cell proliferation assays is described. Optimisation based on the introduction of basic amine linkers to effect good drug distribution to tumour led to the identification of a compound with oral activity in a human colon cancer xenograft study associated with increased histone H3 acetylation in tumour tissue.

Monocyte and macrophage selective anti-inflammatory kinase inhibitors

Appending appropriate esters to anti-inflammatory compounds leads to monocyte/macrophage selectivity. This has been demonstrated in p38α MAP kinase in which we observe differential inhibition of phosphorylation of the substrate MAPKAPK2 in stimulated cells. This selectivity is due to differential expression of carboxylesterases within the cells, which cause the active form of the compounds to accumulate with the cells.