In Vitro and in Vivo Activity of mTOR Kinase and PI3K Inhibitors Against Leishmania donovani and Trypanosoma brucei

Abstract

Kinetoplastid parasites, including Leishmania and Trypanosoma spp., are life threatening pathogens with a worldwide distribution. Next-generation therapeutics for treatment are needed as current treatments have limitations, such as toxicity and drug resistance. In this study, we examined the activities of established mammalian target of rapamycin (mTOR)/phosphoinositide 3-kinase (PI3K) inhibitors against these tropical diseases. High-throughput screening of a library of 1742 bioactive compounds against intracellular L. donovani was performed, and seven mTOR/PI3K inhibitors were identified. Dose-dilution assays revealed that these inhibitors had half maximal effective concentration (EC50) values ranging from 0.14 to 13.44 μM for L. donovani amastigotes and from 0.00005 to 8.16 μM for T. brucei. The results of a visceral leishmaniasis mouse model indicated that treatment with Torin2, dactolisib, or NVP-BGT226 resulted in reductions of 35%, 53%, and 54%, respectively, in the numbers of liver parasites. In an acute T. brucei mouse model using NVP-BGT226 parasite numbers were reduced to under the limits of detection by five consecutive days of treatment. Multiple sequence and structural alignment results indicated high similarities between mTOR and kinetoplastid TORs; the inhibitors are predicted to bind in a similar manner. Taken together, these results indicated that the TOR pathways of parasites have potential for the discovery of novel targets and new potent inhibitors.

Homology Modeling and Molecular Dynamics Simulations ofTrypanosoma cruziPhosphodiesterase b1

“…In agreement with this line of thought, target repurposing, i. e., using known ligands of a protein as starting points to find modulators of a close orthologous protein, has increasingly been used to find new drugs for infectious diseases. [44][45][46][47] All in all, the experiments conducted to evaluate the docking and scoring accuracy suggest that our TcrPDEb1 homology model can be used in computeraided drug discovery efforts to discover novel TcrPDEb1 inhibitors, and that the realized sampling strategy has been useful to provide a more representative conformation of the binding site, with the center of one of the clusters providing the best results in our retrospective screen.…”

The host mTOR pathway and parasitic diseases pathogenesis

“…Interestingly, GSK-2126458 and rapamycin decreased the parasite load and the footpad swelling of infected mice. However, the administration “in vitro” of a wide range of rapamycin doses, selected based on IC 50 values could not allow the elimination of promastigotes which emphasizes the complexity to correlate “in vivo” and “in vitro” drug conversions and effects and the need to proper dose-dilution inhibitory assays and screenings (Phan et al 2020 ). Immunoassay experiments indicated a higher significant increase in the ratio of interleukin (IL)-4 and IFN-γ/IL-4 in splenocytes of infected mice treated with rapamycin.…”

“…Other mTOR/PI3K inhibitors have been found useful against visceral leishmaniasis (VL). The half-maximal effective concentration (EC 50 ) levels of such compounds were reported to be 0.14 up to 13.44 μM for amastigote forms of L. donovani (Phan et al 2020 ). The treatment of experimental VL with mTOR/PI3K inhibitors including dactolisib (BEZ235, NVP-BEZ235), torin 2, and NVP-BGT226 also reduced the rate of Leishmania parasites by 53%, 35%, and 54% respectively, in infected livers (Phan et al 2020 ).…”

“…The half-maximal effective concentration (EC 50 ) levels of such compounds were reported to be 0.14 up to 13.44 μM for amastigote forms of L. donovani (Phan et al 2020 ). The treatment of experimental VL with mTOR/PI3K inhibitors including dactolisib (BEZ235, NVP-BEZ235), torin 2, and NVP-BGT226 also reduced the rate of Leishmania parasites by 53%, 35%, and 54% respectively, in infected livers (Phan et al 2020 ). Moreover, there are other inhibitors like miransertib (ARQ 092) that potentiate mTOR-dependent autophagy in Leishmania -infected macrophages and “in vivo” (Nandan et al 2018 ).…”

“…The target of rapamycin pathway is also present in parasites themselves with high similarities between mTOR and parasite TORs which makes mTOR/PI3K inhibitors highly effective against parasites both “in vivo” and “in vitro” (Diaz-Gonzalez et al 2011 ; Phan et al 2020 ). In parasites, there are orthologues with different regulatory functions including cell cycle regulation and protein synthesis or cell polarization and cytokinesis (Barquilla et al 2008 ; Barquilla and Navarro 2009 ).…”