In continuance of our investigation into the anticancer
activity
of oxadiazoles, we report here the preparation of 10 new 1,3,4-oxadiazole
analogues using the scaffold hopping technique. We have prepared the
oxadiazoles having a common pharmacophoric structure (oxadiazole linked
aryl nucleus) as seen in the reported anticancer agents IMC-038525
(tubulin inhibitor), IMC-094332 (tubulin inhibitor), and FATB (isosteric
replacement of the S of thiadiazole with the O of oxadiazole). All
of the oxadiazole analogues were predicted for their absorption, distribution,
metabolism, and excretion (ADME) profiles and toxicity studies. All
of the compounds were found to follow Lipinski’s rule of 5
with a safe toxicity profile (Class IV compound) against immunotoxicity,
mutagenicity, and toxicity. All of the compounds were synthesized
and characterized using spectral data, followed by their anticancer
activity tested in a single-dose assay at 10 μM as reported
by the National Cancer Institute (NCI US) Protocol against nearly
59 cancer cell lines obtained from nine panels, including non-small-cell
lung, ovarian, breast, central nervous system (CNS), colon, leukemia,
prostate, and cancer melanoma. N-(2,4-Dimethylphenyl)-5-(3,4,5-trifluorophenyl)-1,3,4-oxadiazol-2-amine
(6h) displayed significant anticancer activity against
SNB-19, OVCAR-8, and NCI-H40 with percent growth inhibitions (PGIs)
of 86.61, 85.26, and 75.99 and moderate anticancer activity against
HOP-92, SNB-75, ACHN, NCI/ADR-RES, 786-O, A549/ATCC, HCT-116, MDA-MB-231,
and SF-295 with PGIs of 67.55, 65.46, 59.09, 59.02, 57.88, 56.88,
56.53, 56.4, and 51.88, respectively. The compound 6h also registered better anticancer activity than Imatinib against
CNS, ovarian, renal, breast, prostate, and melanoma cancers with average
PGIs of 56.18, 40.41, 36.36, 27.61, 22.61, and 10.33, respectively.
Molecular docking against tubulin, one of the appealing cancer targets,
demonstrated an efficient binding within the binding site of combretastatin
A4. The ligand 6h (docking score = −8.144 kcal/mol)
interacted π-cationically with the residue Lys352 (with the
oxadiazole ring). Furthermore, molecular dynamic (MD) simulation studies
in complex with the tubulin-combretastatin A4 protein and ligand 6h were performed to examine the dynamic stability and conformational
behavior.