The design and synthesis of inhibitors for the essential Leishmania bromodomain LdBDF5 Jennifer Carter 1 , Nathaniel Jones 2 , Catherine Russell 2 , Jeremy Mottram 2 , Anthony Wilkinson 2 , Jacob Bush 3 , Stuart Conway 1 1 University of Oxford, UK, 2 University of York, UK, 3 GlaxoSmithKline, UK
Leishmaniasis is a disease caused by the parasite Leishmania that is epidemic across Africa, Asia, and Latin America. 1 Leishmania have complex lifecycles, adopting a range of phenotypes to survive in multiple hosts. 2 Epigenetic processes link genotype to phenotypic diversity in a population and so must play a role in regulation of the Leishmania lifecycle. Bromodomain-containing proteins (BCPs) are epigenetic proteins which recognise acetylated lysine (KAc) residues in histones and regulate transcription. Therefore, it might be possible to develop Leishmania specific bromodomain inhibitors that impair epigenetic functions in the parasite. Ld BDF5 is a BCP that contains two bromodomains ( Ld BDF5.1 and Ld BDF5.2) and interprets histone acetylation marks in Leishmania to maintain normal levels of gene expression. 3 Inducible gene deletion has shown that Ld BDF5 is essential for parasite survival in its two main life stages; the promastigote and the amastigote. 3 The aim of this project is to design, synthesise, and evaluate high affinity bromodomain ligands that are selective for Ld BDF5 to help validate this protein as a therapeutic target to treat leishmaniasis. We adopted a fragment-based screening approach to identify ligands for Ld BDF5. A total of 32 KAc-mimicking fragments were synthesised and evaluated using biophysical assays. We identified 10 compounds that interact with Ld BDF5.1, but none binding to Ld BDF5.2. Compound 1 ( K d = 1410 nM, microscale thermophoresis) was selected to probe the SAR of Ld BDF5.1 (Figure 1). A concise synthetic route was developed to synthesise 35 analogues of 1 with modifications at two positions, R 1 and R 2 . The introduction of an aromatic ring at R 2 led to substantial increases in compound affinity. Addition of a 3-nitro or 3-nitrile group on the aromatic ring generated compounds 2 , 3 and 4 which show a >10-fold increase in affinity for LdBDF5.1We hypothesise that the nitro and nitrile groups on the benzene ring are forming H-bonds with T-99. A range of amines and water solubilising groups were introduced at R 1 . The combination of a morpholine ring at R 1 , and a 3-nitro benzene ring at R 2 gives compound 3 , with K d = 68 nM. Optimised compounds are being tested in parasite viability assays and demonstrate promising activity in the parasite, with compound 3 having EC 50 = 5.5µM in promastigotes. References 1. Alvar, J., Yactayo, S. and Bern, C., Leishmaniasis and poverty. Trends Parasitol 22 , 552-557 (2006) 2. Field, M., Horn, D., Fairlamb, A. et al. Anti-trypanosomatid drug discovery: an ongoing challenge and a continuing need. Nat Rev Microbiol 15 , 217–231 (2017) 3. Jones, N.G., Geoghegan, V., Moore, G. et al. Bromodomain factor 5 is an essential regulator of transcription in Leishmania . Nat Commun 13 , 4071 (2022)
P10
© The Author(s), 2022
Made with FlippingBook Learn more on our blog