Structure‐Activity Relationships, Tolerability and Efficacy of Microtubule‐Active 1,2,4‐Triazolo[1,5‐a]pyrimidines as Potential Candidates to Treat Human African Trypanosomiasis**

Abstract

Tubulin and microtubules (MTs) are potential protein targets to treat parasitic infections and our previous studies have shown that the triazolopyrimidine (TPD) class of MT‐active compounds hold promise as antitrypanosomal agents. MT‐targeting TPDs include structurally related but functionally diverse congeners that interact with mammalian tubulin at either one or two distinct interfacial binding sites; namely, the seventh and vinca sites, which are found within or between α,β‐tubulin heterodimers, respectively. Evaluation of the activity of 123 TPD congeners against cultured Trypanosoma brucei enabled a robust quantitative structure‐activity relationship (QSAR) model and the prioritization of two congeners for in vivo pharmacokinetics (PK), tolerability and efficacy studies. Treatment of T. brucei‐infected mice with tolerable doses of TPDs significantly decreased blood parasitemia within 24 h. Further, two once‐weekly doses at 10 mg/kg of a candidate TPD significantly extended the survival of infected mice relative to infected animals treated with vehicle. Further optimization of dosing and/or the dosing schedule of these CNS‐active TPDs may provide alternative treatments for human African trypanosomiasis.

Design, Synthesis, and Evaluation of An Anti‐trypanosomal [1,2,4]Triazolo[1,5‐a]pyrimidine Probe for Photoaffinity Labeling Studies

“… [a] Data previously published [2,7] . [b] Fold‐changes in acetylated α‐tubulin (AcTub) and total α‐tubulin (α‐Tub) protein levels in HEK293 cells, relative to vehicle (DMSO)‐treated cells, were determined after a 4 h incubation with compound at either 1 or 10 μM (*p<0.05 and **p<0.01 by one‐way ANOVA).…”

“…Computational studies were conducted using MAESTRO (Schrödinger) [13] and the Molecular Operating Environment (MOE) [14] . The αβ‐tubulin complex with cevipabulin was obtained from the Protein Data Bank (PDB ID: 7CLD), while the homology model for T. brucei tubulin was constructed as described in our recent study [7] . Briefly, the FASTA sequences for α‐ (P04106) and β‐ (P04107) tubulin from the UniProt database were used to model the proteins based on the mammalian tubulin structure (PDB: 7CLD [5] ) and refined with the AMBER10: EHT force field using MOE 2022.02.…”

“…A recent study of a broad set of TPD derivatives from all three classes against Trypanosoma brucei in vitro indicated that hybrid and Class II TPDs are potent nanomolar anti‐trypanosomal compounds [7] . In addition, although these compounds did not show cell selectivity in vitro , short‐term treatments ( i. e ., single‐ or two‐dose treatments) of T. brucei ‐infected mice with selected hybrid or Class II TPDs at or below the maximum tolerated dose decreased parasitemia to below detectable levels which translated into a significant extension of mouse survival [7] . Furthermore, a comparison of a matched molecular pair of representative compounds from the hybrid and Class II TPDs indicated that hybrid TPDs may provide a more promising combination of efficacy and tolerability in vivo [7] .…”

“…In addition, although these compounds did not show cell selectivity in vitro , short‐term treatments ( i. e ., single‐ or two‐dose treatments) of T. brucei ‐infected mice with selected hybrid or Class II TPDs at or below the maximum tolerated dose decreased parasitemia to below detectable levels which translated into a significant extension of mouse survival [7] . Furthermore, a comparison of a matched molecular pair of representative compounds from the hybrid and Class II TPDs indicated that hybrid TPDs may provide a more promising combination of efficacy and tolerability in vivo [7] . Although these results indicate that hybrid TPDs might be potential candidates to treat African trypanosomiasis, thus far, there has been no direct evidence of T. brucei tubulin engagement by TPDs.…”

Clickable Probes for Pathogen Proteasomes: Synthesis and Applications

“…HEK293 , and HepG2 cells were cultured in DMEM supplemented with 10% heat-inactivated fetal bovine serum (FBS) and 1% penicillin-streptomycin. Cells were grown in T75 cell culture flasks maintained at 37 °C in 5% CO 2 , and passaged at 60–80% cell confluence.…”