Insights could provide new angles for scientists as they work to find answers in managing neurodegenerative diseases, such as Alzheimer's disease.
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In the nervous system, Wnt signalling is important for neuronal differentiation, development, and stem cell maintenance. Overall, neuronal Wnt signalling tends to decrease with ageing. At the same time, the Wnt inhibiting molecules, such as Notum, may increase, resulting in a reduction of neurogenesis and contributing to neurodegenerative diseases, such as Alzheimer's disease.
Notum has recently been identified as a negative regulator of Wnt signalling through the removal of an essential palmitoleate group from Wnt proteins, thus deactivating Wnts. Notum inhibitors could make more active Wnt protein available for signalling, thus offering therapeutic benefits for Wnt insufficient pathological states, such as Alzheimer's disease. However, some previously discovered Notum inhibitors cannot penetrate the blood-brain barrier, so researchers are engaged in crystallographic fragment screening for novel Notum inhibitors.
They carried out these experiments at Diamond's XChem platform. Built around MX beamline I04-1, XChem specialises in screening fragments directly in crystals by X-ray crystallography, using synthesis-aligned fragment libraries. With the sample preparation laboratory lab34 co-located with the beamline, it offers a highly streamlined process allowing up to 1,000 compounds to be screened individually in less than a week, including ~24 hours of unattended beamtime. The process covers soaking, harvesting, automatic data collection, and data analysis, and tailored software and automated systems enable researchers to record and track data seamlessly from initial crystal cultivation to data analysis.
Fragment screening has become increasingly popular over the last decade as it promises a step-change in early drug discovery process. It provides valuable and cost-effective insights for rational drug design, enabling scientists to identify high-quality lead candidates in the early stages of discovery. Rather than focusing on a few large complex compounds, it explores a larger part of the existing chemical space from the drug targets of interest, providing new entry routes for developing lead compounds.
This research involved soaking over a thousand compounds into Notum crystals and collecting X-ray diffraction data. After analysing 768 datasets, they found 59 compounds that bind to the Notum enzyme pocket with different potencies. Six hits were chosen for further development, and one (1-phenyl-1,2,3-triazole) has shown promising properties and the capability to penetrate the brain.
The lead compound, 1-phenyl-1,2,3-triazole, is now being used to assess when and in which tissues blocking the action of Notum could have beneficial effects by re-balancing the level of Wnt signalling.
Willis, NJ. et al. Design of a potent, selective, and brain-penetrant inhibitor of Wnt-deactivating enzyme Notum by optimization of a crystallographic fragment hit. Journal of Medicinal Chemistry 65, 7212-7230 (2022). DOI: 10.1021/acs.jmedchem.2c00162.
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