Development of α-acyloxycarboxamides targeting Leishmania amazonensis parasite†

Abstract

Leishmaniases comprise a set of neglected diseases, afflicting over one million people worldwide and frequently leading to fatal outcomes, mainly in their visceral form. The current treatment often comes with severe side effects and limitations regarding its effectiveness. It is imperative to explore novel therapeutic avenues that are more potent and less toxic. In this study, we successfully synthesized α-acyloxycarboxamides (also known as depsipeptides). These compounds underwent rigorous evaluation through a combination of molecular docking, molecular dynamics (MD) simulations, and in vitro assessments against both promastigote and amastigote forms of Leishmania amazonensis. Notably, most of the α-acyloxycarboxamides showed substantially low cytotoxicity in peritoneal macrophages with a CC₅₀ above 400 μM, whereas amphotericin B (positive control) showed a CC₅₀ value greater than 50 μM. This effect is reflected in the selectivity index (SI), where compounds 7a₁ and 7db₁ showed more favorable results (SI >14.66 and 10.44) when compared to the positive control (SI > 10.36). In vitro experiments demonstrated that the α-acyloxycarboxamides effectively inhibited the growth of axenic promastigote forms of L. amazonensis. Particularly, compounds 7a₁ (IC₅₀ = 31.83 μM) and 7db₁ (IC₅₀ = 33.88 μM) stood out, displaying significant activity in reducing intracellular parasites as well (IC₅₀ = 27.28 and 38.31 μM, respectively). To gain insights into the potential pathway of activity for compound 7a₁, we conducted in silico studies targeting predictive pharmacokinetic parameters and the application of reverse molecular docking utilizing critical biological targets, followed by molecular dynamics (MD) simulations. Among 59 Leishmania targets, the reverse approach suggested that compound 7a₁ targets the N-myristoyltransferase enzyme by establishing only hydrophobic interactions with four amino acid residues at the binding site, with an affinity energy of −8.98 kcal mol⁻¹. Subsequently, MD simulations were performed to obtain further information on its binding modes and complex stability under physiological conditions, in which it was observed that the macromolecule presented great stability in the presence of compound 7a₁ (<1.0 Å), suggesting a stable ligand–target complex formation. Regarding ADMET studies, a-acyloxycarboxamides demonstrated promising properties, with no violations of the Lipinski rule. This study underscores the promise of α-acyloxycarboxamides as potential therapeutic candidates targeting leishmaniasis. Developing these compounds could lead to more effective and less toxic treatments, addressing a critical need in the fight against this neglected disease.