Drug design and synthesis of new N-substituted-thienopyridine based on 2-aminothiophene derivatives as antileishmanial agents.

Leishmaniasis is a neglected tropical disease with limited and often toxic treatment options. This study explores the antileishmanial potential of N-substituted thieno[2,3-c]pyridine derivatives through combined in vitro and in silico approaches. Initially, N-Boc-thieno[2,3-c]pyridine (2a-i) and N-Boc-thieno[2,3-b]pyridine (1a-f) derivatives were synthesized and evaluated against Leishmania amazonensis, L. braziliensis, L. infantum, and RAW 264.7 macrophages. Only N-Boc-thieno[2,3-c]pyridine derivatives with substituted nitrogen at position 6 (2b, 2c, 2f, 2g) were active (IC₅₀ < 10 μM). Based on this, a series of N-benzyl-thieno[2,3-c]pyridine analogs (3a-i) was synthesized, with compounds 3c, 3f, and 3g showing improved antipromastigote activity and selectivity índices (SI). Notably, compound 3f demonstrated potent amastigote activities (IC₅₀ between 0.83 and 1.13 μM), comparable to amphotericin B, but with a 250-fold higher SI and low in vivo toxicity (LD₅₀ = 2000 mg/kg in Zophobas morio). Physicochemical and pharmacokinetic predictions using SwissADME and Osiris indicated favorable drug-like properties and oral bioavailability for 3f. Molecular docking and dynamics simulations revealed strong binding affinities to Nucleoside Diphosphate Kinase (NDK) (PDB: 5GO1), Dihydroorotate Dehydrogenase (DHODH) (PDB: 4WZH), and Sterol 14α-Demethylase (CYP51) (PDB: 3L4D), surpassing reference ligands, with stable complexes, key catalytic site interactions, low RMSD, compact Radius of gyration, and reduced RMSF, supporting their potential as conformationally stable and specific enzyme inhibitors for leishmaniasis treatment. Altogether, these findings strongly highlight the potential of N-substituted thieno[2,3-c]pyridine as promising scaffolds for antileishmanial drug development and highlight compound 3f as a lead candidate for further optimization.