Discovery of a Novel Inhibitor of Human Purine Nucleoside Phosphorylase by a Simple Hydrophilic Interaction Liquid Chromatography Enzymatic Assay.

Human purine nucleoside phosphorylase (HsPNP) belongs to the purine salvage pathway of nucleic acids. Genetic deficiency of this enzyme triggers apoptosis of activated T-cells due to the accumulation of deoxyguanosine triphosphate (dGTP). Therefore, potential chemotherapeutic applications of human PNP inhibitors include the treatment of T-cell leukemia, autoimmune diseases and transplant tissue rejection. In this report, we present the discovery of novel HsPNP inhibitors by coupling experimental and computational tools. A simple, inexpensive, direct and non-radioactive enzymatic assay coupled to hydrophilic interaction liquid chromatography and UV detection (LC-UV using HILIC as elution mode) was developed for screening HsPNP inhibitors. Enzymatic activity was assessed by monitoring the phosphorolysis of inosine (Ino) to hypoxanthine (Hpx) by LC-UV. A small library of 6- and 8-substituted nucleosides was synthesized and screened. The inhibition potency of the most promising compound, 8-aminoinosine (4), was quantified through Ki and IC50 determinations. The effect of HsPNP inhibition was also evaluated in vitro through the study of cytotoxicity on human T-cell leukemia cells (CCRF-CEM). Docking studies were also carried out for the most potent compound, allowing further insights into the inhibitor interaction at the HsPNP active site. This study provides both new tools and a new lead for developing novel HsPNP inhibitors.

Novel rivaroxaban-loaded poly(lactic-co-glycolic acid)/poloxamer nanoparticles: preparation, physicochemical characterization, in vitro evaluation of time-dependent anticoagulant activity and toxicological profile.

Rivaroxaban (RXB), an oral direct factor Xa inhibitor, presents innovative therapeutic profile. However, RXB has shown adverse effects, mainly due to pharmacokinetic limitations, highlighting the importance of developing more effective formulations. Therefore, this work aims at the preparation, physicochemical characterization and in vitro evaluation of time-dependent anticoagulant activity and toxicology profile of RXB-loaded poly(lactic-co-glycolic acid) (PLGA)/poloxamer nanoparticles (RXBNps). RXBNp were produced by nanoprecipitation method and physicochemical characteristics were evaluated. In vitro analysis of time-dependent anticoagulant activity was performed by prothrombin time test and toxicological profile was assessed by hemolysis and MTT reduction assays. The developed RXBNp present spherical morphology with average diameter of 205.5 ± 16.95 nm (PdI 0.096 ± 0.04), negative zeta potential (-26.28 ± 0.77 mV), entrapment efficiency of 91.35 ± 2.40%, yield of 41.81 ± 1.68% and 3.72 ± 0.07% of drug loading. Drug release was characterized by an initial fast release followed by a sustained release with 28.34 ± 2.82% of RXB available in 72 h. RXBNp showed an expressive time-dependent anticoagulant activity in human and rat blood plasma and non-toxic profile. Based on the results presented, it is possible to consider that RXBNp may be able to assist in the development of promising new therapies for treatment of thrombotic disorders.

Translational impact of novel widely pharmacological characterized mofezolac-derived COX-1 inhibitors combined with bortezomib on human multiple myeloma cell lines viability.

A set of novel diarylisoxazoles has been projected using mofezolac (1) as a lead compound to investigate structure-inhibitory activity relationships of new compounds and the cyclooxygenases (COXs) catalytic activity. Mofezolac was chosen because is the most potent and selective reversible COX-1 inhibitor [COX-1 IC50 = 0.0079 µM and COX-2 IC50 > 50 µM, with a selectivity index (SI) in favor of COX-1 higher than 6300]. Seventeen new compounds were synthesized in fair to good yields and evaluated for their COXs inhibitory activity and selectivity. SIs ranged between 1 and higher than 1190.3,4-Bis(4-methoxyphenyl)-5-vinylisoxazole (22) has the highest SI with COX-1 IC50 = 0.042 µM and COX-2 IC50 > 50 µM. 1 and 22 were superior to aspirin in inhibiting platelet aggregation (IC50 = 0.45, 0.63 and 1.11 µM, respectively) in human platelet rich plasma (hPRP) assay. They did not induce blood coagulation and hemolysis, and are neither genotoxic nor mutagen. 1 and 22 slightly increase bortezomib cytotoxic effect on multiple myeloma (MM) cell lines (NCI-H929 and RPMI-8226) and affects MM cell cycle and apoptosis when co-administered with the proteasome inhibitor bortezomib, a drug clinically used to treat plasma cell neoplasms including MM. In addition, structure-based binding mode of 1 and 22, through Fingerprints for Ligands and Proteins (FLAG) calculation, allowed to explain the one order of magnitude difference between COX-1 IC50 values of the two compounds. Specifically, the higher inhibitory potency seems due to the formation of a H-bond between COX-1 S530 and the carboxyl, present in 1 and absent in 22.