KBE009: A Bestatin-Like Inhibitor of the Trypanosoma cruzi Acidic M17 Aminopeptidase with In Vitro Anti-Trypanosomal Activity

Abstract

Chagas disease, caused by the kinetoplastid parasite Trypanosoma cruzi, is a human tropical illness mainly present in Latin America. The therapies available against this disease are far from ideal. Proteases from pathogenic protozoan have been considered as good drug target candidates. T. cruzi acidic M17 leucyl-aminopeptidase (TcLAP) mediates the major parasite’s leucyl-aminopeptidase activity and is expressed in all parasite stages. Here, we report the inhibition of TcLAP (IC50 = 66.0 ± 13.5 µM) by the bestatin-like peptidomimetic KBE009. This molecule also inhibited the proliferation of T. cruzi epimastigotes in vitro (EC50 = 28.1 ± 1.9 µM) and showed selectivity for the parasite over human dermal fibroblasts (selectivity index: 4.9). Further insight into the specific effect of KBE009 on T. cruzi was provided by docking simulation using the crystal structure of TcLAP and a modeled human orthologous, hLAP3. The TcLAP-KBE009 complex is more stable than its hLAP3 counterpart. KBE009 adopted a better geometrical shape to fit into the active site of TcLAP than that of hLAP3. The drug-likeness and lead-likeness in silico parameters of KBE009 are satisfactory. Altogether, our results provide an initial insight into KBE009 as a promising starting point compound for the rational design of drugs through further optimization.

Identification of a potent and selective LAPTc inhibitor by RapidFire-Mass Spectrometry, with antichagasic activity

“…It is also interesting that the four most potent inhibitors (compounds 4, 7, 28 and 5; Table 1 ) share the thiazole ring. These novel LAPTc inhibitors complement the small cohort of previously described LAPTc inhibitors (including bestatin [ 14 ], arphamenine A [ 16 ] and the bestatin-derivative peptidomimetic KBE009 [ 27 ]; Fig 1 ), and provide new opportunities to explore this mechanism of action as a therapeutic target for Chagas disease as well as tool compounds to investigate basic biology. Compound 4 is highlighted as a candidate for further progression and the only molecule with a submicromolar IC 50 for LAPTc inhibition.…”

“…For compound 4, interaction with LAPTc’s metal cations is not predicted. A similar hydrophobicity-driven interaction has also been modelled for the bestatin-based peptidomimetic KBE009 [ 27 ] ( Fig 1 ), with hydrophobic interactions between KBE009 and LAPTc residues K 300 , F 304 , D 370 , T 402 , G 403 , A 496 and F 497 (numbering differs in one residue). Two of these residues also participate in the predicted interaction with compound 4 (T 402 and A 496 ).…”

“…Importantly, LAPTc and human LAP3 have differences in their hydrophilicity/hydrophobicity at the entrance to their catalytic pockets and LAP3 also has a relatively hydrophilic area close to the catalytic site. This is thought to drive the selectivity of KBE009, a relatively hydrophobic compound, for LAPTc over LAP3 [ 27 ] ( Fig 1 ). A similar effect may explain the selectivity we observe for compound 4, which is also relatively hydrophobic.…”

“…M17 LAP inhibitors are dipeptide-like compounds, with hydrophobic and bulky substituents. Only a few LAPTc inhibitors have been identified; bestatin [ 14 ], the bestatin-based peptidomimetic KBE009 [ 27 ] and arphamenine A [ 16 ] ( Fig 1 ). PfA-M17 inhibitors have also been reported.…”