Pharmacophore requirements for HIV-1 reverse transcriptase inhibitors that selectively "Freeze" the pre-translocated complex during the polymerization catalytic cycle

A Novel 3-meta-Pyridine-1,2,4-oxadiazole Derivative of Glycyrrhetinic Acid as a Safe and Promising Candidate for Overcoming P-Glycoprotein-Mediated Multidrug Resistance in Tumor Cells

Given the pharmacophore properties of the nitrogen-containing moiety in the molecular structure of P-glycoprotein (P-gp) inhibitors, we report the evaluation of the P-gp inhibitory and MDR reversal activities of 2g, a 3-meta-pyridin-1,2,4-oxadiazole derivative of 18βH-glycyrrhetinic acid. Through molecular docking, we have shown that 2g has the potential to directly interact with the transmembrane domain of P-gp with a low free binding energy (-10.2 kcal/mol). Using KB-8-5 human cervical carcinoma cells and RLS40 murine lymphosarcoma cells, both of which exhibit a multidrug-resistant (MDR) phenotype mediated by P-gp activation, we have shown that 2g, at nontoxic concentrations, effectively increased the intracellular accumulation of fluorescent P-gp substrates (rhodamine 123 or doxorubicin (DOX)), leading to a marked sensitization of the model cells to the cytotoxic effect of DOX. Considering the comparable activity of 2g with verapamil, a known P-gp inhibitor, 2g can be considered as a promising candidate for the development of agents capable of overcoming P-gp-mediated MDR in tumor cells.

New Deoxycholic Acid Derived Tyrosyl-DNA Phosphodiesterase 1 Inhibitors Also Inhibit Tyrosyl-DNA Phosphodiesterase 2

A series of deoxycholic acid (DCA) amides containing benzyl ether groups on the steroid core were tested against the tyrosyl-DNA phosphodiesterase 1 (TDP1) and 2 (TDP2) enzymes. In addition, 1,2,4- and 1,3,4-oxadiazole derivatives were synthesized to study the linker influence between a para-bromophenyl moiety and the steroid scaffold. The DCA derivatives demonstrated promising inhibitory activity against TDP1 with IC₅₀ in the submicromolar range. Furthermore, the amides and the 1,3,4-oxadiazole derivatives inhibited the TDP2 enzyme but at substantially higher concentration. Tryptamide 5 and para-bromoanilide 8 derivatives containing benzyloxy substituent at the C-3 position and non-substituted hydroxy group at C-12 on the DCA scaffold inhibited both TDP1 and TDP2 as well as enhanced the cytotoxicity of topotecan in non-toxic concentration in vitro. According to molecular modeling, ligand 5 is anchored into the catalytic pocket of TDP1 by one hydrogen bond to the backbone of Gly458 as well as by π–π stacking between the indolyl rings of the ligand and Tyr590, resulting in excellent activity. It can therefore be concluded that these derivatives contribute to the development of specific TDP1 and TDP2 inhibitors for adjuvant therapy against cancer in combination with topoisomerase poisons.

Medicinal chemistry of pyrophosphate mimics: A mini review

The pyrophosphate mimicking groups offer rational modification of the pyrophosphate-bearing natural substrates of the overexpressed enzymes that cause the onset of disease progression. Mainly, the modified substrate interacts differently with the enzyme active site eventually causing its deactivation, or provides the therapeutically active products at the completion of the catalytic cycle that contribute toward the inhibition of the target enzyme. Many of the pyrophosphate mimic-containing molecules serve as competitive or allosteric inhibitors of the target enzyme to achieve the desirable properties for the mitigation of the target enzyme's pathophysiology. This review presents an epigrammatic overview of the pyrophosphate mimics in medicinal chemistry.

5,6-Dihydroxypyrimidine Scaffold to Target HIV-1 Nucleocapsid Protein

The HIV-1 nucleocapsid (NC) protein is a small basic DNA and RNA binding protein that is absolutely necessary for viral replication and thus represents a target of great interest to develop new anti-HIV agents. Moreover, the highly conserved sequence offers the opportunity to escape the drug resistance (DR) that emerged following the highly active antiretroviral therapy (HAART) treatment. On the basis of our previous research, nordihydroguaiaretic acid 1 acts as a NC inhibitor showing moderate antiviral activity and suboptimal drug-like properties due to the presence of the catechol moieties. A bioisosteric catechol replacement approach led us to identify the 5-dihydroxypyrimidine-6-carboxamide substructure as a privileged scaffold of a new class of HIV-1 NC inhibitors. Hit validation efforts led to the identification of optimized analogs, as represented by compound 28, showing improved NC inhibition and antiviral activity as well as good ADME and PK properties.