Several classes of amyloid-directed compounds have been shown to inhibit a-syn aggregation and been investigated as potential new drugs, despite this, not a single molecule has reached the market [1, 2]. In recent years, the close cooperation between drug delivery/treatment and molecular imaging disciplines have moved towards relatively new classes of compounds known as theranostics. The term theranostic indicates the concomitant capability of a single molecule to act as therapeutic and diagnostic agent at the same time. Several examples of theranostic system have already been reported in literature for the treatment of cancer, atherosclerosis and gene delivery. In our previous work, we developed a new theranostic compound (denoted as G8) able to simultaneously detect and inhibit Ab and PrPSc plaques in in vitro study.
Scrapie infected cells, treated with G8 compound showed lower levels of scrapie deposits and the compound was able to stain the scrapie plaques in the same infected cells, confirming its in vitro capability to inhibit and at the same time to detect the accumulated deposits. Using a similar approach, as in our reported work, among several libraries received from our collaborators from University of Bologna and Siena we are screening molecules in order to identify lead compounds able to detect and disaggregate amyloid deposits typical of neurodegenerative diseases (Aβ plaques, PrPSc, and α-syn).
More recently, we decided to follow a new approach by combining 3D-QSAR model, derived from pharmacophore-based alignment, with molecular docking procedures and physico-chemical properties prediction. With this innovative procedure we have developed a virtual screening protocol to find novel chemicals able to prevent PrPC misfolding. We identified different hits characterized by low toxicity and able to inhibit PrPSc accumulation in vitro in prion-infected neuroblastoma cell lines (ScN2a). In this assay, the pyrroloquinoxaline hydrazone 96 showed the higest potency with an IC50 value of 1.6 μM. Pyrroloquinoxaline 96 was demonstrated also to bind PrPSc aggregates in infected ScN2a cells with a fluorescence pattern comparable to that found for Thioflavin-T. In consideration of its satisfactory physico-chemical properties, including predicted blood brain barrier permeability, 96 could represent an interesting prototypic hit for the development of diagnostic and therapeutic probes for prion diseases.
We look forward to further develop our methods into a novel pipeline for rapid drug discovery that can be applied to any target protein involved in neurodegenerative diseases.
1. Aulic, S., M.L. Bolognesi, and G. Legname, Small-molecule theranostic probes: a promising future in neurodegenerative diseases. Int J Cell Biol, 2013. 2013: p. 150952.
2. Latawiec, D., et al., Modulation of alpha-synuclein aggregation by dopamine analogs. PLoS One, 2010. 5(2): p. e9234
3. Zaccagnini L., et al., Identification of novel fluorescent probes preventing PrPSc replication in prion diseases, European Journal of Medicinal Chemistry, Volume 127, 2017, Pages 859-873, ISSN 0223-5234.
