Abstract:
Cytokine Interleukin-2 (IL-2) has a prevalent role in the growth, activation, and differentiation
o f T-cells. To suppress immune responses associated with organ transplant rejection and
other autoimmune diseases, it is important to disrupt the interaction of IL-2 with its receptor
system. IL-2 is now emerging as a target in the discovery of novel therapeutics for addressing
the problems related to immune system. The main goal of this study was to establish an
effective in silico protocol for identification of IL-2 inhibitors. It describes a pharmacophore
based virtual screening combined with docking study as a rational strategy for identification of
novel IL-2 inhibitors. Structure based pharmacophore model was developed using the crystal
structure of IL-2/IL-2Rα (PDB ID: 1Z92) complex.
The predictive pharmacophore model consisted of three features, two hydrophobic and one
cationic feature with three excluded volumes. The pharmacophore was validated using a
training set of thirty known IL-2 inhibitors. Pharmacophore model as a 3D search query was
searched against ZINC and MOE database, in order to retrieve new chemical scaffolds that
may be potent IL-2 inhibitors. The hits retrieved from this search were filtered based on their
RMSD values and pharmacophoric features. Hits that were retained were used in a molecular
docking study to find the binding mode and molecular interactions with crucial residues at the
active site of the target. Pharmacophore based molecular docking was carried out on virtually
screened compounds using 1Z92 as target by MOE software that led to the identification of 15
hits belonging to diverse classes of heterocycles. These hits were further optimized and a
library of forty six compounds including 5-6 membered azaheterocycles namely
dihydropyrimidines, heteroazepines, pyrazoles and benzimidazoles besides some compounds
such as chalcones and Schiff bases, was designed and synthesized.
All newly synthesized compounds were characterized by their MS and NMR spectral analysis.
IL-2 inhibition studies on the members of the synthesized library led to the identification of
novel IL-2 inhibitors with IC 50 values ranging from <2- >50μg/ml using cyclosporine as a
standard drug. This entire set of experiments in both dry and wet labs led to a successful
designing and synthesis of a variety of compounds as novel scaffolds that may be developed
into interesting immunomodulators.