Binding poses of the analyzed compounds were modeled on the basis of the crystal-lographic binding mode of ligand I in the PTR1 binding site (PDB code 3GN2 ), and prepared in the same way as the receptors for docking simulations. The modified inhibitor structures were built and minimized within the TbPTR1 pocket, and then truncated to the final fragments. The TbPTR1-ligand binding energy was calculated for the binding pocket model composed of 11 amino acid residues within 4 Å of any atom of the I ligand fragment (Fig. , SI), i.e., Met163, Gln166, Cys168, Gly205, Val206, Glu217, Trp221, Lys224, Leu263 (chain A of TbPTR1), and His267 and Ala268 (chain D).