Abstract
Chagas disease is endemic to 21 countries across the Americas, with an estimated 6-7 million people infected worldwide. Currently, only two drugsbenznidazole (BZN) and nifurtimoxare approved for treatment. While effective during the acute phase and in preventing mother-to-child transmission, these medications exhibit minimal to no efficacy in the chronic phase, require prolonged treatment courses, and are associated with significant side effects. Building on our previous work, we identified hit 1 (IC(50) = 7 μM) as demonstrating superior in vitro activity against trypomastigotes forms of Trypanosoma cruzi Tulahuen strain compared to BZN (IC(50) = 34 μM), along with a high selectivity index (SI = 114). To further investigate its potential, we synthesized 17 analogs, preserving the essential 4-(4-nitrophenyl)-1H-1,2,3-triazole scaffold crucial for antitrypanosomal activity, while modifying the N-benzylacetamide moiety. Preliminary screening for antitrypanosomatid activity and cytotoxicity against the T. cruzi Tulahuen strain identified compound 16 as the most promising candidate. This compound features a peracetylated galactopyranosyl unit in place of the N-benzylacetamide moiety, enhancing its potential for further development. It demonstrated potent activity against T. cruzi (IC(50) 6 ± 1 μM, Tulahuen CL2 β-galactosidase strain) with no detectable cytotoxicity in mammalian cell lines. Compound 16 and its deprotected derivative, compound 19, were further evaluated for their activity against T. cruzi intracellular amastigotes in infected LLC-MK2 (epithelial) and C2C12 (myoblast) cells. Noninfected control cells were exposed to the same treatment conditions to assess compound cytotoxicity (CC(50)). Notably, compound 16 (IC(50): LLC-MK2, 0.16 ± 0.02 μM; C2C12, 0.13 ± 0.01 μM) and compound 19 (IC(50): LLC-MK2, 0.10 ± 0.04 μM; C2C12, 0.11 ± 0.02 μM) exhibited higher antiamastigote activity with selectivity indices exceeding 400. In comparison, BZN, a first-line drug against T. cruzi, required significantly higher concentrations to achieve antiamastigote activity (IC(50): LLC-MK2, 1.4 ± 0.1 μM; C2C12, 6 ± 1 μM) and exhibited lower selectivity indices, ranging from 14.4 to 32.8. The exceptional efficacy of compounds 16 and 19 was 33- to 36-fold greater than their activity against trypomastigotes, underscoring their strong therapeutic potential during the chronic phase. Additionally, pre-exposure of LLC-MK2 and C2C12 cell lines to these compounds significantly reduced infection rates in both models, demonstrating potent residual antiamastigote activity. The ability of compounds 16 and 19 to lower the infection index in LLC-MK2 and C2C12 cells was further assessed in combination with BZN. All combinations outperformed BZN alone, yielding significantly reduced post-treatment parasite burdens even at the lowest concentrations (0.06 μM) of compounds 16 and 19. As derivatives of benznidazole, both compounds were evaluated as substrates for T. cruzi nitroreductase (TcNTR) and displayed only residual activity. These results suggest that compounds 16 and 19 operate through mechanisms distinct from BZN, with their combined inhibitory activity likely arising from synergic effects. Finally, both compounds were tested against Recombinant trans-sialidase from T. cruzi (TcTS), considering the role of galactose units in parasite mucins as acceptors of host sialic acid during the TcTS-catalyzed transfer reaction. The deprotected galactosyl derivative 19 was identified as a weak TcTS inhibitor, with an IC(50) of 1.1 ± 0.1 mM. We presented novel galactosyl-4-(4-nitrophenyl)-1H-1,2,3-triazole derivatives that demonstrate high efficacy and selectivity, showing potential for treating both acute and chronic phases of Chagas disease. These compounds represent promising leads for the development of new drug candidates to address this neglected disease.