Discovery of 9-Cyclopropylethynyl-2-((S)-1-[1,4]dioxan-2-ylmethoxy)-6,7-dihydropyrimido[6,1-a]isoquinolin-4-one (GLPG1205), a Unique GPR84 Negative Allosteric Modulator Undergoing Evaluation in a Phase II Clinical Trial.

GPR84 is a medium chain free fatty acid-binding G-protein-coupled receptor associated with inflammatory and fibrotic diseases. As the only reported antagonist of GPR84 (PBI-4050) that displays relatively low potency and selectivity, a clear need exists for an improved modulator. Structural optimization of GPR84 antagonist hit 1, identified through high-throughput screening, led to the identification of potent and selective GPR84 inhibitor GLPG1205 (36). Compared with the initial hit, 36 showed improved potency in a guanosine 5'-O-[γ-thio]triphosphate assay, exhibited metabolic stability, and lacked activity against phosphodiesterase-4. This novel pharmacological tool allowed investigation of the therapeutic potential of GPR84 inhibition. At once-daily doses of 3 and 10 mg/kg, GLPG1205 reduced disease activity index score and neutrophil infiltration in a mouse dextran sodium sulfate-induced chronic inflammatory bowel disease model, with efficacy similar to positive-control compound sulfasalazine. The drug discovery steps leading to GLPG1205 identification, currently under phase II clinical investigation, are described herein.

Arrayed adenoviral expression libraries for functional screening.

With the publication of the sequence of the human genome, we are challenged to identify the functions of an estimated 70,000 human genes and the much larger number of proteins encoded by these genes. Of particular interest is the identification of gene products that play a role in human disease pathways, as these proteins include potential new targets that may lead to improved therapeutic strategies. This requires the direct measurement of gene function on a genomic scale in cell-based, functional assays. We have constructed and validated an individually arrayed, replication-defective adenoviral library harboring human cDNAs, termed PhenoSelect library. The adenoviral vector guarantees efficient transduction of diverse cell types, including primary cells. The arrayed format allows screening of this library in a variety of cellular assays in search for gene(s) that, by overexpression, induce a particular disease-related phenotype. The great majority of phenotypic assays, including morphological assays, can be screened with arrayed libraries. In contrast, pooled-library approaches often rely on phenotype-based isolation or selection of single cells by employing a flow cytometer or screening for cell survival. An arrayed placental PhenoSelect library was screened in cellular assays aimed at identifying regulators of osteogenesis, metastasis, and angiogenesis. This resulted in the identification of known regulators, as well as novel sequences that encode proteins hitherto not known to play a role in these pathways. These results establish the value of the PhenoSelect platform, in combination with cellular screens, for gene function discovery.