Within medicinal chemistry nowadays, the so-called pharmaco-dynamics seeks for qualitative (for understanding) and quantitative (for predicting) mechanisms/models by which given chemical structure or series of congeners actively act on biological sites either by focused interaction/therapy or by diffuse/hazardous influence. To this aim, the present review exposes three of the fertile directions in approaching the biological activity by chemical structural causes: the special computing trace of the algebraic structure-activity relationship (SPECTRAL-SAR) offering the full analytical counterpart for multi-variate computational regression, the minimal topological difference (MTD) as the revived precursor for comparative molecular field analyses (CoMFA) and comparative molecular similarity indices analysis (CoMSIA); all of these methods and algorithms were presented, discussed and exemplified on relevant chemical medicinal systems as proton pump inhibitors belonging to the 4-indolyl,2-guanidinothiazole class of derivatives blocking the acid secretion from parietal cells in the stomach, the 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine congeners’ (HEPT ligands) antiviral activity against Human Immunodeficiency Virus of first type (HIV-1) and new pharmacophores in treating severe genetic disorders (like depression and psychosis), respectively, all involving 3D pharmacophore interactions.

Molecular modeling and MTD methods are useful tools to assess both qualitative(SAR) and quantitative (QSAR) chemical structure-biological activity relationships. The 1-[(2-hydroxiethoxi)-methyl]-6-(phenylthio)thymine congeners (HEPT ligands) show in vitroanti-viral activity against the type-1 human immunodeficiency virus (HIV-1), which is theetiologic agent of AIDS. This work shows an extensive QSAR study performed upon a largeseries of 79 HEPT ligands using the MTD and HyperChem molecular modeling methods.The studied HEPT ligands are HIV reverse-transcriptase inhibitors. Their geometries wereoptimized and conformational analysis was carried out to build the hypermolecule, whichallowed applying the MTD method. The hypermolecule was used for space mapping of thereceptor’s interaction site. The obtained results show that there are three 3D molecular zonesimportant for the anti-HIV biological activity of the HEPT ligands under study.