Discovery of a Bromodomain and Extraterminal Inhibitor with a Low Predicted Human Dose through Synergistic Use of Encoded Library Technology and Fragment Screening.

The bromodomain and extraterminal (BET) family of bromodomain-containing proteins are important regulators of the epigenome through their ability to recognize N-acetyl lysine (KAc) post-translational modifications on histone tails. These interactions have been implicated in various disease states and, consequently, disruption of BET-KAc binding has emerged as an attractive therapeutic strategy with a number of small molecule inhibitors now under investigation in the clinic. However, until the utility of these advanced candidates is fully assessed by these trials, there remains scope for the discovery of inhibitors from new chemotypes with alternative physicochemical, pharmacokinetic, and pharmacodynamic profiles. Herein, we describe the discovery of a candidate-quality dimethylpyridone benzimidazole compound which originated from the hybridization of a dimethylphenol benzimidazole series, identified using encoded library technology, with an N-methyl pyridone series identified through fragment screening. Optimization via structure- and property-based design led to I-BET469, which possesses favorable oral pharmacokinetic properties, displays activity in vivo, and is projected to have a low human efficacious dose.

In vitro and in vivo characterization of the novel GABAB receptor positive allosteric modulator, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE).

There is preclinical evidence supporting the finding that the GABA(B) receptor orthosteric agonist, baclofen, has significant effects on eating behavior suggesting the potential therapeutic application of this compound for the treatment of eating related disorders. However, the wide clinical use of baclofen might be limited by the appearance of sedative and motor impairment effects. The identification of positive allosteric modulators (PAMs) of GABA(B) receptors represents a novel therapeutic approach to reduce the centrally-mediated adverse effects typical of the GABA(B) receptor orthosteric agonist. In the present work, we report the in vitro profile of a novel chemical structure, 2-{1-[2-(4-chlorophenyl)-5-methylpyrazolo[1,5-a]pyrimidin-7-yl]-2-piperidinyl}ethanol (CMPPE) identified by screening the GSK compound collection. CMPPE potentiates GABA-stimulated [(35)S]GTPγS binding to membranes of human recombinant cell line and of rat brain cortex. GABA concentration-response curves (CRC) in the presence of fixed concentrations of CMPPE, in rat native tissue, revealed an increase of both the potency and maximal efficacy of GABA. A similar modulatory effect was observed in GABA(B) receptor-mediated activation of inwardly rectifying potassium channels in hippocampal neurons. CMPPE (30-100 mg/kg) and GS39783 (100 mg/kg) significantly decreased food consumption in rat without impairment on the animal locomotor activity. On the contrary, baclofen (2.5 mg/kg) decreased both food intake and motor performance. All together these findings confirm the role of GABA(B) system in controlling animal food intake and for the first time demonstrate that GABA(B) receptor PAMs may represent a novel pharmacological approach to treat eating disorders without unwanted sedative effects.

Differential expansion of zinc-finger transcription factor loci in homologous human and mouse gene clusters.

Mammalian genomes carry hundreds of Krüppel-type zinc finger (ZNF) genes, most of which reside in familial clusters. ZNF genes encoding Krüppel-associated box (KRAB) motifs are especially prone to this type of tandem organization. Despite their prevalence, little is known about the functions or evolutionary histories of these clustered gene families. Here we describe a homologous pair of human and mouse KRAB-ZNF gene clusters containing 21 human and 10 mouse genes, respectively. Evolutionary analysis uncovered only three pairs of putative orthologs and two cases where a single gene in one species is related to multiple genes in the other; several human genes have no obvious homolog in mouse. We deduce that duplication and loss of ancestral cluster members occurred independently in the primate and rodent lineages after divergence, yielding substantially different ZNF gene repertoires in humans and mice. Differences in expression patterns and sequence divergence within the DNA binding regions of predicted proteins suggest that the duplicated genes have acquired novel functions over evolutionary time. Since KRAB-ZNF proteins are predicted to function as transcriptional regulators, the elaboration of new lineage-specific genes in this and other clustered ZNF families is likely to have had a significant impact on species-specific aspects of biology.