Insight into the structural requirements of urokinase-type plasminogen activator inhibitors based on 3D QSAR CoMFA/CoMSIA models

Urokinase-type plasminogen activator (uPA), a trypsin-like serine protease, has been implicated in large number of malignancies, tumor cell invasion, angiogenesis and metastasis; hence, the potent and selective inhibitors of uPA may therefore be therapeutically useful drugs for treatment of various forms of cancer. A three-dimensional quantitative structure-activity relationship (3D QSAR) study was performed on five different chemical series reported as selective uPA inhibitors employing comparative molecular field analysis (CoMFA)/comparative molecular similarity indices analysis (CoMSIA) techniques to investigate the structural requirements for substrates and derive a predictive model that may be used for the design of novel uPA inhibitors. ClogP has been used as an additional descriptor in the CoMFA analysis to study the effects of lipophilic parameters on activity. Inclusion of ClogP did not improve the models significantly and exhibited comparable correlation coefficients with CoMFA steric and electrostatic models. 3D QSAR models were derived for 2-pyridinylguanidines (training set N = 25, test set N = 8), 4-aminoarylguanidines and 4-aminoarylbenzamidines (training set N = 29, test set N = 8), thiophene-2-carboxamindines (training set N = 64, test set N = 19), 2-naphthamidines (training set N = 32, test set N = 8), and 1-isoquinolinylguanidines (training set N = 29, test set N = 7). 3D contour maps generated from these models were analyzed individually, which provides the regions in space where interactive fields may influence the activity. The superimposition of contour maps on the active site of serine proteases additionally helps in understanding the structural requirements of these inhibitors. Further, the predictive ability of 3D QSAR models was affirmed by predicting the activity of novel 2-naphthamidines. 3D QSAR models developed may be used in designing and predicting the uPA inhibitory activity of novel molecules.

3D-QSAR CoMFA/CoMSIA studies on Urokinase plasminogen activator (uPA) inhibitors: a strategic design in novel anticancer agents.

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) was performed on a series of indole/benzoimidazole-5-carboxamidines as urokinase plasminogen activator (uPA) inhibitors. The ligand molecular superimposition on template structure was performed by atom/shape-based RMS fit, multifit, and RMSD fit methods. The removal of two outliers from the initial training set of 30 molecules improved the predictivity of the models. The statistically significant model was established from 28 molecules, which were validated by evaluation of test set of nine compounds. The atom-based RMS alignment yielded best predictive CoMFA model (r2(cv) = 0.611, r2(cnv) = 0.778, F value = 43.825, r2(bs) = 0.842, r2(pred) = 0.616 with two components) while the CoMSIA model yielded (r2(cv) = 0.499, r2(cnv) = 0.976, F value=96.36, r2(bs) = 0.993, r2(pred) = 0.694 with eight components). The contour maps obtained from 3D-QSAR studies were appraised for the activity trends of the molecules analyzed. The results indicate that the steric, electrostatic, and hydrogen bond donor/acceptor substituents play significant role in uPA activity and selectivity of these compounds. The data generated from the present study can be used as putative pharmacophore in the design of novel, potent, and selective urokinase plasminogen activator inhibitors as cancer therapeutics.

Synthesis and biological evaluation of 5-formyl-6-arylimidazo(2,1-b)-1,3,4-thiadiazole-2-N-(dimethylaminomethi no) sulfonamides as antitumor agents.

In search for potential anti cancer drug candidates in imidazo (2,1-b)-1,3,4-thiadiazole series, two series of 5-formyl-6-arylimidazo(2,1-b)-1,3,4-thiadiazole-2-N- (dimethylaminomethino) sulfonamides and 5-bromo-6-aryl/ethylacetateimidazo(2,1-b)-1,3,4- thiadiazole-2-sulfonamides were synthesised. All compounds showed significant cytotoxic effects (log10 GI50 < -4.0, log molar drug concentration required to cause 50% growth inhibition) against a variety of human tumor cell lines of the National Cancer Institute in vitro screen, including cells derived from solid tumors such as non-small cell lung, colon, central nervous system, melanoma, ovarian, prostate and breast cancer, and also few cell lines of leukemia and renal cancer. Introduction of a formyl group at the 5- and substituted aromatic group at 6-position generated compounds with potent antitumor activity. Incorporation of a bromo at 5- and ester group at 6-position produced compounds with reduced activity.