Comparative analysis of drug-salt-polymer interactions by experiment and molecular simulation improves biopharmaceutical performance.

The propensity of poorly water-soluble drugs to aggregate at supersaturation impedes their bioavailability. Supersaturated amorphous drug-salt-polymer systems provide an emergent approach to this problem. However, the effects of polymers on drug-drug interactions in aqueous phase are largely unexplored and it is unclear how to choose an optimal salt-polymer combination for a particular drug. Here, we describe a comparative experimental and computational characterization of amorphous solid dispersions containing the drug celecoxib, and a polymer, polyvinylpyrrolidone vinyl acetate (PVP-VA) or hydroxypropyl methylcellulose acetate succinate, with or without Na+/K+ salts. Classical models for drug-polymer interactions fail to identify the best drug-salt-polymer combination. In contrast, more stable drug-polymer interaction energies computed from molecular dynamics simulations correlate with prolonged stability of supersaturated amorphous drug-salt-polymer systems, along with better dissolution and pharmacokinetic profiles. The celecoxib-salt-PVP-VA formulations exhibit excellent biopharmaceutical performance, offering the prospect of a low-dosage regimen for this widely used anti-inflammatory, thereby increasing cost-effectiveness, and reducing side-effects.

Amorphous Salts Solid Dispersions of Celecoxib: Enhanced Biopharmaceutical Performance and Physical Stability.

Numerous amorphous solid dispersion (ASD) formulations of celecoxib (CEL) have been attempted for enhancing the solubility, dissolution rate, and in vivo pharmacokinetics via high drug loading, polymer combination, or by surfactant addition. However, physical stability for long-term shelf life and desired in vivo pharmacokinetics remains elusive. Therefore, newer formulation strategies are always warranted to address poor aqueous solubility and oral bioavailability with extended shelf life. The present investigation elaborates a combined strategy of amorphization and salt formation for CEL, providing the benefits of enhanced solubility, dissolution rate, in vivo pharmacokinetics, and physical stability. We generated amorphous salts solid dispersion (ASSD) formulations of CEL via an in situ acid-base reaction involving counterions (Na+ and K+) and a polymer (Soluplus) using the spray-drying technique. The generated CEL-Na and CEL-K salts were homogeneously and molecularly dispersed in the matrix of Soluplus polymer. The characterization of generated ASSDs by differential scanning calorimetry revealed a much higher glass-transition temperature (Tg) than the pure amorphous CEL, confirming the salt formation of CEL in solid dispersions. The micro-Raman and proton nuclear magnetic resonance spectroscopy further confirmed the formation of salt at the -S═O position in the CEL molecules. CEL-Na-Soluplus ASSD exhibited a synergistic enhancement in the aqueous solubility (332.82-fold) and in vivo pharmacokinetics (9.83-fold enhancement in the blood plasma concentration) than the crystalline CEL. Furthermore, ASSD formulations were physically stable for nearly 1 year (352 days) in long-term stability studies at ambient conditions. Hence, we concluded that the ASSD is a promising strategy for CEL in improving the physicochemical properties and biopharmaceutical performance.

Identification and characterization of novel metabolites of nintedanib by ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry with in silico toxicological assessment.

RATIONALE: Nintedanib, an oral, triple angiokinase inhibitor, is used alongside docetaxel in the management of locally recurrent non-small-cell lung cancer and idiopathic pulmonary fibrosis. The present study deals with the identification and characterization of in vitro and in vivo stable and reactive (if any) metabolites of nintedanib and sheds light on some novel metabolites of the drug which have not been reported previously. METHODS: The study involved an oral administration of the drug to male Wistar rats, followed by collection of the biological matrices (urine, plasma and feces) at specific intervals for determination of in vivo metabolites. In addition, in vitro studies were performed on human and rat liver microsomes in the presence of appropriate co-factors. The samples were subjected to protein precipitation and nitrogen evaporation prior to ultra-performance liquid chromatography/quadrupole time-of-flight tandem mass spectrometry analysis. The toxicities of all the metabolites were assessed in silico, employing ADMET Predictor™. RESULTS: A total of 18 metabolites of nintedanib were identified in all the matrices, of which nine were found to be novel and unreported previously. The unreported metabolites were elucidated as oxidative, demethylated and glucuronide conjugates of nintedanib. Interestingly, acetonitrile adducts of a few metabolites (low concentration) were also observed. No reactive metabolites were observed in this study. CONCLUSIONS: Characterization of hitherto unknown in vitro and in vivo metabolites of nintedanib adds to the existing knowledge on the metabolism of the drug. Identification on the basis of the solvated adducts can be a useful approach for characterization of minor metabolites, which remain undetected owing to sensitivity issues.

In vivo metabolic investigation of cetilistat in normal versus pseudo-germ-free rats using UPLC-QTOFMS/MS and in silico toxicological evaluation of its metabolites.

Cetilistat (CET) is a pancreatic lipase inhibitor approved for management of obesity after the serious adverse effects exhibited by its analogue orlistat. Exhaustive literature review reveals lack of comprehensive reports on its biotransformation. With a view to study the same, the present study reports the identification and characterization of metabolites of CET in rats using UPLC-MS/MS. As the small intestine is the site of action for CET, it is important that the role of microbial flora in the metabolism of CET be explored. To achieve this, the metabolic profile of CET was compared between normal and pseudo-germ-free rats. The study involved the administration of a drug suspension to male Sprague-Dawley pseudo-germ-free and normal untreated rats followed by collection of urine, feces, and blood at specific intervals. Sample preparation was performed using liquid-liquid extraction and concentration of samples followed by analysis using LC-MS/MS. Finally, an in silico study was performed on the drug and metabolites to predict their toxicological properties using ADMET PredictorTM software. Four metabolites of CET were observed in in vivo matrices. As expected, significant changes were observed both qualitatively and quantitatively, implying that formation of metabolites was both CYP enzymes and gut microflora mediated.

In vitroand in vivo investigation of metabolic fate of riociguat by HPLC-Q-TOF/MS/MS and in silico evaluation of the metabolites by ADMET predictor™.

Riociguat, a guanyl cyclase inhibitor, is one of its kind drug regimen approved for management of pulmonary arterial hypertension and chronic thromboembolism pulmonary hypertension. Extensive literature review indicates lack of comprehensive reports on its metabolic fate. The present study reports the in vivo and in vitro identification and characterization of metabolites of riociguat, using high-performance liquid chromatography-quadruple time-of-flight tandem mass spectrometry. In vitro studies were conducted by incubating the drug in human and rat liver microsomes in presence of respective cofactors. In vivo studies were undertaken by oral administration of suspension of drug to male Sprague-Dawley rats followed by collection of urine, feces and blood at specific intervals. A total of 18 metabolites were observed in in vivo and in vitro matrices which includes hydroxyl, N-oxide, desmethyl, defluorinated hydroxyl, glucuronides and N-acetyl cysteine conjugates. Presence of N-acetyl cysteine conjugates strongly points towards the formation of a reactive metabolite intermediate trapped through N-acetyl cysteine and can be considered a matter of concern as the reactive metabolites have been known to manifest toxicities. Their presence was mimicked in in vitro samples as well. The toxicological properties of drug and metabolites were evaluated by using ADMET Predictor ™ software.

Enhanced Biopharmaceutical Performance of Rivaroxaban through Polymeric Amorphous Solid Dispersion.

Rivaroxaban (RXB) is an orally active direct inhibitor of the activated serine protease Factor Xa, given as monotherapy in the treatment of venous thromboembolism (VTE). It has been characterized in vitro as a substrate for the active, nonsaturable efflux via P-gp transporter, limiting its high permeability. Therefore, the role of P-gp inhibiting polymers in enhancing the biopharmaceutical performance of RXB by preparing polymeric amorphous solid dispersion and subsequent improvement in solubility and permeability was investigated. Initially, solubility parameter and Flory-Huggins interaction parameter were determined for miscibility studies between drug and polymers. Binary dispersions were prepared by dissolving drug with polymers eudragit S100, eudragit L100, and soluplus in common solvent (5% v/v water in tetrahydrofuran) using spray dryer. Prepared binary dispersions were analyzed by differential scanning calorimetry (DSC), microscopy, powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FTIR), dynamic vapor sorption (DVS), and solution nuclear magnetic resonance (NMR) spectroscopy. Superior performance of binary dispersions was observed upon dissolution and solubility studies over micronized active pharmaceutical ingredient. Amorphous solid dispersion (ASD) prepared with soluplus showed 10-fold increase in apparent solubility and maintenance of supersaturation for 24 h compared to the crystalline RXB. Further, pharmacokinetic study performed in animals was in good correlation with the solubility data. Increases of 5.7- and 6.7-fold were observed in AUC and Cmax, respectively, for ASDs prepared with soluplus compared to those with crystalline RXB. FTIR and NMR spectroscopy unveiled the involvement of N-H group of RXB with C═O group of polymers in intermolecular interactions. The decreased drug efflux ratio was observed for ASDs prepared with eudragit S100 and soluplus in Caco-2 transport study suggesting improvement in the absorption of RXB. Hence, the present study demonstrates ASD using soluplus as a promising formulation strategy for enhancing the biopharmaceutical performance of RXB by increasing the solubility and circumventing the P-gp activity.