In Silico Quantitative Structure-Activity Relationship Studies on P-gp Modulators of Tetrahydroisoquinoline-Ethyl-Phenylamine Series

Changdev G Gadhe,Gugan Kothandan,Seung Joo Cho,Thirumurthy Madhavan

doi:10.1186/1472-6807-11-5

Abstract

BackgroundMultidrug resistance (MDR) is a major obstacle in cancer chemotherapy. The drug efflux by a transport protein is the main reason for MDR. In humans, MDR mainly occurs when the ATP-binding cassette (ABC) family of proteins is overexpressed simultaneously. P-glycoprotein (P-gp) is most commonly associated with human MDR; it utilizes energy from adenosine triphosphate (ATP) to transport a number of substrates out of cells against concentration gradients. By the active transport of substrates against concentration gradients, intracellular concentrations of substrates are decreased. This leads to the cause of failure in cancer chemotherapy.ResultsHerein, we report Topomer CoMFA (Comparative Molecular Field Analysis) and HQSAR (Hologram Quantitative Structure Activity Relationship) models for third generation MDR modulators. The Topomer CoMFA model showed good correlation between the actual and predicted values for training set molecules. The developed model showed cross validated correlation coefficient (q2) = 0.536 and non-cross validated correlation coefficient (r2) = 0.975 with eight components. The best HQSAR model (q2 = 0.777, r2 = 0.956) with 5-8 atom counts was used to predict the activity of test set compounds. Both models were validated using test set compounds, and gave a good predictive values of 0.604 and 0.730.ConclusionsThe contour map near R1 indicates that substitution of a bulkier and polar group to the ortho position of the benzene ring enhances the inhibitory effect. This explains why compounds with a nitro group have good inhibitory potency. Molecular fragment analyses shed light on some essential structural and topological features of third generation MDR modulators. Fragments analysis showed that the presence of tertiary nitrogen, a central phenyl ring and an aromatic dimethoxy group contributed to the inhibitory effect. Based on contour map information and fragment information, five new molecules with variable R1 substituents were designed. The activity of these designed molecules was predicted by the Topomer CoMFA and HQSAR models. The novel compounds showed higher potency than existing compounds.

Highlights

Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy
Cyclosporine-A, was designed as an immunosuppressant, but shows a promising P-gp inhibitory effect. Both these drugs are used as first generation P-gp inhibitors, called MDR modulators
Simulated annealing was performed for each ligand up to 200 cycles with default parameters, and conformations were sorted according to the least potential energy value

Summary

Introduction

Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy. The drug efflux by a transport protein is the main reason for MDR. By the active transport of substrates against concentration gradients, intracellular concentrations of substrates are decreased This leads to the cause of failure in cancer chemotherapy. In MDR tumour cells, various member of the ABC family of transport proteins can simultaneously be overexpressed: these include P-gp (ABCB1), breast cancer resistance protein (BCRP, ABCG2) and MDR associated protein 1 (MRP1, ABCC family) [2]. The calcium channel blocker verapamil can overcome MDR in cancer cells [10] Another drug, cyclosporine-A, was designed as an immunosuppressant, but shows a promising P-gp inhibitory effect. The second generation modulators, dexverapamil and PSC833, had higher efficacy and lower toxicity, but produce serious drugdrug interactions clinically

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