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Open AccessArticle

Design and Selection of Novel C1s Inhibitors by In Silico and In Vitro Approaches

1
Targetex Biosciences, Madách Imre utca 31/2., H-2120 Dunakeszi, Hungary
2
Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok Körútja 2., H-1117 Budapest, Hungary
3
Department of Organic Chemistry, Faculty of Pharmacy, Semmelweis University, Hőgyes Endre u. 7, H-1092 Budapest, Hungary
4
MTA TTK Lendület Artificial Transporter Research Group, Institute of Materials and Environmental Chemistry, Research Center for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok Körútja 2., H-1117 Budapest, Hungary
5
Faculty of Pharmacy, Institute of Pharmaceutical Chemistry, University of Szeged, Zrínyi u. 9., H-6720 Szeged, Hungary
*
Author to whom correspondence should be addressed.
Molecules 2019, 24(20), 3641; https://doi.org/10.3390/molecules24203641
Received: 11 September 2019 / Revised: 3 October 2019 / Accepted: 5 October 2019 / Published: 9 October 2019
The complement system is associated with various diseases such as inflammation or auto-immune diseases. Complement-targeted drugs could provide novel therapeutic intervention against the above diseases. C1s, a serine protease, plays an important role in the CS and could be an attractive target since it blocks the system at an early stage of the complement cascade. Designing C1 inhibitors is particularly challenging since known inhibitors are restricted to a narrow bioactive chemical space in addition selectivity over other serine proteases is an important requirement. The typical architecture of a small molecule inhibitor of C1s contains an amidine (or guanidine) residue, however, the discovery of non-amidine inhibitors might have high value, particularly if novel chemotypes and/or compounds displaying improved selectivity are identified. We applied various virtual screening approaches to identify C1s focused libraries that lack the amidine/guanidine functionalities, then the in silico generated libraries were evaluated by in vitro biological assays. While 3D structure-based methods were not suitable for virtual screening of C1s inhibitors, and a 2D similarity search did not lead to novel chemotypes, pharmacophore model generation allowed us to identify two novel chemotypes with submicromolar activities. In three screening rounds we tested altogether 89 compounds and identified 20 hit compounds (<10 μM activities; overall hit rate: 22.5%). The highest activity determined was 12 nM (1,2,4-triazole), while for the newly identified chemotypes (1,3-benzoxazin-4-one and thieno[2,3-d][1,3]oxazin-4-one) it was 241 nM and 549 nM, respectively.
Keywords: complement system; virtual screening; C1s inhibitor; FactorXa; biological screening; pharmacophore modelling complement system; virtual screening; C1s inhibitor; FactorXa; biological screening; pharmacophore modelling
MDPI and ACS Style

Szilágyi, K.; Hajdú, I.; Flachner, B.; Lőrincz, Z.; Balczer, J.; Gál, P.; Závodszky, P.; Pirli, C.; Balogh, B.; Mándity, I.M.; Cseh, S.; Dormán, G. Design and Selection of Novel C1s Inhibitors by In Silico and In Vitro Approaches. Molecules 2019, 24, 3641.

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