Roland Bürli

A comparative study of fragment screening methods on the p38α kinase: new methods, new insights

The stress-activated kinase p38α was used to evaluate a fragment-based drug discovery approach using the BioFocus fragment library. Compounds were screened by surface plasmon resonance (SPR) on a Biacore™ T100 against p38α and two selectivity targets. A sub-set of our library was the focus of detailed follow-up analyses that included hit confirmation, affinity determination on 24 confirmed, selective hits and competition assays of these hits with respect to a known ATP binding site inhibitor. In addition, functional activity against p38α was assessed in a biochemical assay using a mobility shift platform (LC3000, Caliper LifeSciences). A selection of fragments was also evaluated using fluorescence lifetime (FLEXYTE™) and microscale thermophoresis (Nanotemper) technologies. A good correlation between the data for the different assays was found. Crystal structures were solved for four of the small molecules complexed to p38α. Interestingly, as determined both by X-ray analysis and SPR competition experiments, three of the complexes involved the fragment at the ATP binding site, while the fourth compound bound in a distal site that may offer potential as a novel drug target site. A first round of optimization around the remotely bound fragment has led to the identification of a series of triazole-containing compounds. This approach could form the basis for developing novel and active p38α inhibitors. More broadly, it illustrates the power of combining a range of biophysical and biochemical techniques to the discovery of fragments that facilitate the development of novel modulators of kinase and other drug targets.

A small molecule mitigates hearing loss in a mouse model of Usher syndrome III

Usher syndrome type III (USH3) characterized by progressive deafness, variable balance disorder, and blindness is caused by destabilizing mutations in the gene encoding the clarin-1 protein (CLRN1). Here we report a novel strategy to mitigate hearing loss associated with a common USH3 mutation CLRN1N48K that involved a cell-based high-throughput screening of small molecules capable of stabilizing CLRN1N48K, a secondary screening to eliminate general proteasome inhibitors, and finally an iterative process to optimize structure activity relationships. This resulted in the identification of BF844. To test the efficacy of BF844, a mouse model was developed that mimicked the progressive hearing loss of USH3. BF844 effectively attenuated progressive hearing loss and prevented deafness in this model. Because the human CLRN1N48K mutation causes both hearing and vision loss, BF844 could in principle prevent both sensory deficiencies in USH3. Moreover, the strategy described here could help identify drugs for other protein-destabilizing monogenic disorders.

Towards Small Molecules as Therapies for Alzheimer’s Disease and Other Neurodegenerative Disorders

Abstract Neurodegenerative diseases caused by hereditary or idiosyncratic neuronal dysfunction share some phenotypic commonalities. Intracellular aggregation of proteins, metal dyshomeostasis, generic loss of synaptic connectivity all lead to gradual decline of cognitive or motor neuronal function as patients descend into a clinically symptomatic state. Though significant progress has been made in our understanding of neurological disorders in the past decade, it has yet to translate into therapeutic advancements in disease treatment. We have chosen to focus this review on Alzheimer’s disease (AD) to highlight the main disease modifying mechanisms shared in common with the Huntington’s (HD) and Parkinson’s disease (PD) phenotypes, specifically, the aggregation of amyloid-β (Aβ) phospho-tau (p-tau), mutant huntingtin (mHtt) and α -synuclein (α-syn) proteins, respectively. We highlight a number of approaches used in pre-clinical drug discovery to identify clinical tools. In addition, we describe a number of less explored alternative hypotheses which have demonstrated good (pre)clinical evidence for a potential therapeutic intervention. In particular, for AD, we will review the main concepts which have driven drug discovery research in the recent past and for each molecular target, we summarize a rationale and available validation data with commentary on relevant chemical matter and structural biology, then discuss advanced pre-clinical and clinical compounds.