Candesartan Cilexetil Formulations in Mesoporous Silica: Preparation, Enhanced Dissolution In Vitro, and Oral Bioavailability In Vivo.

Candesartan cilexetil (CC) is one of well-tolerated antihypertensive drugs, while its poor solubility and low bioavailability limit its use. Herein, two mesoporous silica (Syloid XDP 3150 and Syloid AL-1 FP) and the corresponding amino-modified products (N-XDP 3150 and N-AL-1 FP) have been selected as the carriers of Candesartan cilexetil to prepare solid dispersion through solvent immersion, and characterized through using powder X-ray diffraction analysis, infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and solid-state nuclear magnetic resonance spectroscopy, etc. The state of CC changed from crystalline to amorphous after loading onto the silica carriers, in which no interactions between CC and silica existed. Then, the dissolution behaviors in vitro were studied through using flow-through cell dissolution method. CC-XDP 3150 sample exhibited the most extensive dissolution, and the cumulative release of CC from it was 1.88-fold larger than that of CC. Moreover, the pharmacokinetic results in rats revealed that the relative bioavailability of CC-XDP 3150 and CC-N-XDP 3150 solid dispersions were estimated to be 326 % % and 238 % % in comparison with CC, respectively. Clearly, pore size, pore volume, and surface properties of silica carrier have remarkable effect on loading, dissolution and bioavailability of CC. In brief, this work will provide valuable information in construction of mesoporous silica-based delivery system toward poorly water-soluble drugs.

Solidification of deep eutectic solvent containing fimasartan through wet impregnation and exploration of flow attributes by modified SeDeM-SLA expert system.

The solidification of deep eutectic solvent (DES) through wet impregnation techniques on inert solid carriers is an interesting approach that offers better processing attributes and excellent stability. Herein, DES of Fimasartan (FS) was developed to improve its solubility and bioavailability. The selected DES-FS was solidified by wet impregnation method employing Nesulin US2 and Aerosil 200. The SeDeM-SLA (solid-liquid adsorption) system was employed to investigate flow attributes of solidified DES-FS. Further, the selected solidified DES-FS (A) was characterized by Fourier transforms infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM). The DES comprising Choline Chloride (ChCl): Glycerol (Gly) (1:3) revealed maximum drug solubility (35.6 ± 2.2 mg/mL) and thus opted for solidification. Solidification through wet impregnation was employed using 1:0.5 ratios (DES-FS to carriers). The Index of Good Flow (IGF) value was calculated from the SeDeM-SLA expert system, which indicates the better flow characteristics of solidified DES-FS, particularly with Neusilin US2 [SDES-FS (A)]. The solid-state evaluation data of SDS-FS (A) suggested a transition of FS to an amorphous form, resulting in an increment in solubility and dissolution. A similar trend was reported in the in vivo pharmacokinetic study, which indicated a 2.9 folds increment in the oral bioavailability of FS. Furthermore, excellent stability, i.e., a shelf life of 28.44 months, reported by SDES-FS (A) in accelerated stability studies, suggests better formulation perspectives. In a nutshell, the present study evokes the potentiality of performing solidification through wet impregnation and successful implementation of the SeDeM-SLA expert model, which could find wide applications in pharmaceutical science.

Solid dispersion systems for enhanced dissolution of poorly water-soluble candesartan cilexetil: In vitro evaluation and simulated pharmacokinetics studies.

BACKGROUND: Candesartan cilexetil (CC) is a selective angiotensin II receptor antagonist widely used to treat hypertension. CC is a substrate of P-glycoprotein (P-gp), causing its efflux to the intestinal lumen. It is also practically insoluble in water and has low oral bioavailability (14%). Thus, the current study aims to improve the in vitro dissolution of CC by developing solid dispersion systems (SDSs) and corroborating the in vitro results using a simulated pharmacokinetics study. METHODS: The SDSs were prepared using polyvinyl pyrrolidone (PVP) as a water-soluble polymer, Eudragit E100 (EE100) as a pH-dependent soluble carrier, and a combination of these two polymers. The saturation solubility and the dissolution rate studies of the prepared systems in three dissolution media were performed. The optimized system SE-EE5 was selected for further investigations, including DSC, XRD, FTIR, FESEM, DLS, TSEM, IVIVC convolution study, and stability studies. RESULTS: The solubility of CC significantly increased by a factor of 27,037.344 when formulated as a solid dispersion matrix using EE100 at a ratio of 1:5 (w/w) drug to polymer (SE-EE5 SD), compared to the solubility of the pure drug. The mechanism of solubility and dissolution rate enhancement of CC by the optimized SDS was found to be via the conversion of the crystalline CC into the amorphous form as well as nanoparticles formation upon dissolution at a pH below 5. The instrumental analysis tests showed good compatibility between CC and EE100 and there was no chemical interaction between the drug and the polymer. Moreover, the stability tests confirmed that the optimized system was stable after three months of storage at 25°C. CONCLUSION: The utilization of the solid dispersion technique employing EE 100 polymer as a matrix demonstrates significant success in enhancing the solubility, dissolution, and subsequently, the bioavailability of water-insoluble drugs like CC.

Assessment of drug-drug interaction of dapagliflozin with LCZ696 based on an LC-MS/MS method.

The co-administration of dapagliflozin (DPF) and sacubitril/valsartan (LCZ696) has emerged as a promising therapeutic approach for managing heart failure. Given that DPF and LCZ696 are substrates for P-glycoprotein, there is a plausible potential for drug-drug interactions when administered concomitantly. To investigate the pharmacokinetic changes when these drugs are co-administered, we have established and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method capable of simultaneously detecting DPF, LBQ657 (the active metabolite of sacubitril) and valsartan in rat plasma. This method has demonstrated selectivity, sensitivity, and accuracy. Drug-drug interactions were examined by the LC-MS/MS method. The mechanisms were investigated using everted intestinal sac models and Caco-2 cells. The results showed that DPF significantly increased the area under the curve (AUC(0-t)) (3,563.3 ± 651.7 vs. 7,146.5 ± 1,714.9 h µg/L) of LBQ657 (the active metabolite of sacubitril) and the AUC(0-t) (24,022.4 ± 6,774.3 vs. 55,728.3 ± 32,446.3 h µg/L) of valsartan after oral co-administration. Dapagliflozin significantly increased the amount of LBQ657 and valsartan in intestinal sacs by 1- and 1.25-fold at 2.25 h. Caco-2 cell uptake studies confirmed that P-glycoprotein is the transporter involved in this interaction. This finding enhances the understanding of drug-drug interactions in the treatment of heart failure and provides a guidence for clinical therapy.

Pharmacokinetic Comparison of a Fixed-Dose Combination of Candesartan Cilexetil/Amlodipine/Atorvastatin Versus Co-administration of Individual Formulations in Healthy Participants.

INTRODUCTION: Fixed-dose combinations (FDCs) of angiotensin II receptor blockers, calcium channel blockers, and statins are conventional therapeutic interventions prescribed for cardiovascular diseases. This study aimed at drawing a comparison between the pharmacokinetics and safety of an FDC and the corresponding individual formulations in healthy subjects. METHODS: A randomized, open-label, single-dose, three-sequence, three-period, partially repeated crossover study was conducted with a cohort of healthy volunteers. A 14-day washout period was maintained between each of the three periods. In this study, candesartan cilexetil, amlodipine, and atorvastatin was administered orally as FDCs of 16/10/40 mg in study 1 and 16/5/20 mg in study 2. The maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration (AUClast) of candesartan, amlodipine, and atorvastatin were estimated as the geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of the FDC to individual formulations. If the within-subject coefficient of variation (CVwr) of Cmax was greater than 0.3, the bioequivalence (BE) range calculated using the reference-scaled average bioequivalence was used to assess whether the 90% CI was within the BE range. RESULTS: The GMRs (90% CIs) for the AUClast for candesartan and amlodipine were 0.9612 (0.9158-1.0089)/0.9965 (0.9550-1.0397) and 1.0033 (0.9800-1.0271)/1.0067 (0.9798-1.0344), and the GMRs (90% CIs) for Cmax were 0.9600 (0.8953-1.0294)/0.9851 (0.9368-1.0359) and 1.0198 (0.9950-1.0453)/1.0003 (0.9694-1.0321) in studies 1 and 2, respectively. The extended BE ranges calculated from the CVwr of the Cmax of atorvastatin were 0.7814-1.2797 and 0.7415-1.3485, respectively. The GMRs (90% CIs) for the AUClast of atorvastatin were 1.0532 (1.0082-1.1003)/1.0252 (0.9841-1.0680), and the GMRs (90% CIs) for Cmax were 1.0630 (0.9418-1.1997)/0.9888 (0.8792-1.1120) in studies 1 and 2, respectively. CONCLUSION: The Cmax and AUClast values of candesartan cilexetil/amlodipine/atorvastatin 16/10/40 mg and 16/5/20 mg, respectively, were within the BE ranges. There were no clinically significant differences in safety between the two formulations. TRIAL REGISTRATION: ClinicalTrials.gov identifier, study 1: NCT04478097; study 2: NCT04627207.

Development and validation of an UPLC-MS/MS method for the simultaneous determination of fexofenadine and olmesartan in human serum: Application to in vivo pharmacokinetic studies.

A sensitive, reproducible, robust, high-throughput ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantification of fexofenadine and olmesartan in human serum. Samples (50 µL) undergo protein precipitation prior to UPLC-MS/MS analysis. The analytes were separated using an Acquity BEH C18 column (2.1 mm × 50 mm, 1.7 µm) at a flow rate of 0.5 mL/min using a gradient elution with a total run time of 4 min. The analytes were detected in positive ion mode and selected reaction monitoring (SRM) was used for quantitation. The standard curve concentration range was 1.0-500.0 ng/mL for both analytes and each analyte showed excellent linearity with correlation coefficients (R2 > 0.99). The intra- and inter-day accuracy and precision were ±15% for each analyte, and excellent recovery was demonstrated (93-98%) for both analytes. The method is well suited for high-throughput quantitative determination of fexofenadine and olmesartan simultaneously and was successfully applied to an in vivo pharmacokinetic and transporter phenotyping study in humans.

Discovery of a Novel Potent Tetrazole Antifungal Candidate with High Selectivity and Broad Spectrum.

Thirty-one novel albaconazole derivatives were designed and synthesized based on our previous work. All compounds exhibited potent in vitro antifungal activities against seven pathogenic fungi. Among them, tetrazole compound D2 was the most potent antifungal with MIC values of <0.008, <0.008, and 2 µg/mL against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus, respectively, the three most common and critical priority pathogenic fungi. In addition, compound D2 also exhibited potent activity against fluconazole-resistant C. auris isolates. Notably, compound D2 showed a lower inhibitory activity in vitro against human CYP450 enzymes as well as a lower inhibitory effect on the hERG K+ channel, indicating a low risk of drug-drug interactions and QT prolongation. Moreover, with improved pharmacokinetic profiles, compound D2 showed better in vivo efficacy than albaconazole at reducing fungal burden and extending the survival of C. albicans-infected mice. Taken together, compound D2 will be further investigated as a promising candidate.

Drug-drug interaction between danshensu and irbesartan and its potential mechanism.

To uncover the effect of danshensu on irbesartan pharmacokinetics and its underlying mechanisms.To investigate the effect of danshensu on the pharmacokinetics of irbesartan, Sprague-Dawley rats (n = 6) were orally administered 30 mg/kg irbesartan alone (control group) or pre-treated with 160 mg/kg danshensu (experimental group). The effect of danshensu on the metabolic stability of irbesartan in RLMs was examined by LC-MS/MS method. The effect of danshensu on CYP2C9 activity was also determined.Danshensu markedly increased the AUC(0-t) (9573 ± 441 vs. 16157 ± 559 µg/L*h) and Cmax (821 ± 24 vs. 1231 ± 44 µg/L) of irbesartan. Danshensu prolonged the t1/2 (13.39 ± 0.98 vs. 16.04 ± 1.21 h) and decreased the clearance rate (2.27 ± 0.14 vs. 1.19 ± 0.10 L/h/kg) of irbesartan. Danshensu enhanced the metabolic stability of irbesartan in vitro with prolonged t1/2 (36.34 ± 11.68 vs. 48.62 ± 12.03 min) and reduced intrinsic clearance (38.14 ± 10.24 vs. 28.51 ± 9.06 µL/min/mg protein). Additionally, the IC50 value for CYP2C9 inhibition by danshensu was 35.74 µM.Danshensu enhanced systemic exposure of irbesartan by suppressing CYP2C9. The finding can also serve as a guidance for further investigation of danshensu-irbesartan interaction in clinical practice.

Conversion of Olmesartan to Olmesartan Medoxomil, A Prodrug that Improves Intestinal Absorption, Confers Substrate Recognition by OATP2B1.

PURPOSE: Olmesartan medoxomil (olmesartan-MX), an ester-type prodrug of the angiotensin II receptor blocker (ARB) olmesartan, is predominantly anionic at intestinal pH. Human organic anion transporting polypeptide 2B1 (OATP2B1) is expressed in the small intestine and is involved in the absorption of various acidic drugs. This study was designed to test the hypothesis that OATP2B1-mediated uptake contributes to the enhanced intestinal absorption of olmesartan-MX, even though olmesartan itself is not a substrate of OATP2B1. METHODS: Tetracycline-inducible human OATP2B1- and rat Oatp2b1-overexpressing HEK 293 cell lines (hOATP2B1/T-REx-293 and rOatp2b1/T-REx-293, respectively) were established to characterize OATP2B1-mediated uptake. Rat jejunal permeability was measured using Ussing chambers. ARBs were quantified by liquid chromatography-tandem mass spectrometry. RESULTS: Significant olmesartan-MX uptake was observed in hOATP2B1/T-REx-293 and rOatp2b1/T-REx-293 cells, whereas olmesartan uptake was undetectable or much lower than olmesartan-MX uptake, respectively. Furthermore, olmesartan-MX exhibited several-fold higher uptake in Caco-2 cells and greater permeability in rat jejunum compared to olmesartan. Olmesartan-MX uptake in hOATP2B1/T-REx-293 cells and in Caco-2 cells was significantly decreased by OATP2B1 substrates/inhibitors such as 1 mM estrone-3-sulfate, 100 µM rifamycin SV, and 100 µM fluvastatin. Rat Oatp2b1-mediated uptake and rat jejunal permeability of olmesartan-MX were significantly decreased by 50 µM naringin, an OATP2B1 inhibitor. Oral administration of olmesartan-MX with 50 µM naringin to rats significantly reduced the area under the plasma concentration-time curve of olmesartan to 76.9%. CONCLUSION: Olmesartan-MX is a substrate for OATP2B1, and the naringin-sensitive transport system contributes to the improved intestinal absorption of olmesartan-MX compared with its parent drug, olmesartan.

Pharmacokinetics and safety of cenobamate, a novel antiseizure medication, in healthy Japanese, and an ethnic comparison with healthy non-Japanese.

Cenobamate (XCOPRI and ONTOZRY) is a novel antiseizure medication for the treatment of focal-onset seizures. Nonetheless, there is limited information on the pharmacokinetics (PKs), safety, and efficacy of cenobamate in Asian people, including Japanese people. This study aimed to evaluate the PKs and safety of cenobamate after a single oral dose in healthy Japanese subjects and to compare the PKs with that reported in non-Japanese subjects. A randomized, double-blind, placebo-controlled, single ascending dose study was conducted at four dose levels of 50, 100, 200, and 400 mg. Subjects were randomly assigned to cenobamate or placebo in a 6:2 ratio. Cenobamate was rapidly absorbed, reaching its maximum plasma concentration (Cmax ) in 0.75 to 2.25 h, and was eliminated with a mean half-life of 37.0 to 57.7 h. The Cmax increased dose proportionally, whereas area under the concentration-time curve increased more than dose proportionally, which was consistent with the findings in non-Japanese subjects. The systemic exposure of cenobamate was comparable between Japanese and non-Japanese subjects at all dose levels evaluated. All adverse events were mild in severity, and their incidence did not show dose-dependent trends. Furthermore, there were no clinically significant issues in safety parameters, including sedation tests, neurologic examinations, and Columbia Suicide Severity Rating Scale interviews. In conclusion, the systemic exposure of cenobamate after a single dose in Japanese subjects increased by dose, which was similar to the pattern in non-Japanese subjects. In addition, a single dose of cenobamate was well-tolerated in the dose range of 50 to 400 mg in healthy Japanese subjects.

Olmesartan niosomes ameliorates the Indomethacin-induced gastric ulcer in rats: Insights on MAPK and Nrf2/HO-1 signaling pathway.

AIMS: Gastric ulcer is a continuous worldwide threat that inquires protective agents. Olmesartan (OLM) has potent anti-oxidant and anti-inflammatory characters, yet having limited bioavailability. We targeted the gastro-protective potential and probable mechanism of OLM and its niosomal form against indomethacin (IND) induced-gastric ulcer in rats. MAIN METHODS: we prepared OLM niosomes (OLM-NIO) with different surfactant: cholesterol molar ratios. We evaluated particle size, zeta-potential, polydispersity, and entrapment efficiency. In-vitro release study, Fourier transform infrared spectroscopy, differential scanning calorimetry, and transmission electron microscopy were performed for selected niosomes. In-vivo, we used oral Omeprazole (30 mg/kg), OLM or OLM-NIO (10 mg/kg) for 3 days before IND (25 mg/kg) ingestion. We assessed gastric lesions, oxidative and inflammatory markers. KEY FINDINGS: OLM-NIO prepared with span 60:cholesterol ratio (1:1) showed high entrapment efficiency 93 ± 2%, small particle size 159.3 ± 6.8 nm, low polydispersity 0.229 ± 0.009, and high zeta-potential -35.3 ± 1.2 mV, with sustained release mechanism by release data. In-vivo macroscopical and histological results showed gastro-protective effects of OLM pretreatment, which improved oxidative stress parameters and enhanced the gastric mucosal cyclooxygenase-1 (COX-1) and prostaglandin E2 (PGE2) contents. OLM pretreatment suppressed interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) contents and translocation of p38 mitogen-activated protein kinase (p38-MAPK). Besides, OLM substantially promoted the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) protective pathway. OLM-NIO furtherly improved all previous outcomes. SIGNIFICANCE: We explored OLM anti-ulcerative effects, implicating oxidative stress and inflammation improvement, mediated by the Nrf2/HO-1 signaling pathway and p38-MAPK translocation. Meanwhile, the more bioavailable OLM-NIO achieved better gastro-protective effects compared to conventional OLM form.

Physiologically based pharmacokinetic modeling of candesartan related to CYP2C9 genetic polymorphism in adult and pediatric patients.

Candesartan cilexetil is an angiotensin II receptor blocker and it is widely used to treat hypertension and heart failure. This drug is a prodrug that rapidly converts to candesartan after oral administration. Candesartan is metabolized by cytochrome P450 2C9 (CYP2C9) enzyme or uridine diphosphate glucurinosyltransferase 1A3, or excreted in an unchanged form through urine, biliary tract and feces. We investigated the effect of genetic polymorphism of CYP2C9 enzyme on drug pharmacokinetics using physiologically based pharmacokinetic (PBPK) modeling. In addition, by introducing the age and ethnicity into the model, we developed a model that can propose an appropriate dosage regimen taking into account the individual characteristics of each patient. To evaluate the suitability of the model, the results of a clinical trial on twenty-two healthy Korean subjects and their CYP2C9 genetic polymorphism data was applied. In this study, PK-Sim® was used to develop the PBPK model of candesartan.

Multivariate Assessment for Bioequivalence Based on the Correlation of Random Effect.

BACKGROUND AND OBJECTIVE: Bioequivalence tests are fundamental step in assessing the equivalence in bioavailability between a test and reference product. In practice, two separate linear mixed models (LMMs) with random subject effects, which have an area under the concentration-time curve (AUC) and the peak concentration (Cmax) as the responses, have become the gold standard for evaluating bioequivalence. Recently, Lee et al developed a multivariate hierarchical generalized linear model (HGLM) for several responses that modeled correlations among multivariate responses via correlated random effects. The objective of this study was to apply this multivariate analysis to the bioequivalence test in practice and to compare the performance of multivariate HGLM and separate LMMs. METHODS: Three pharmacokinetic datasets, fixed-dose combination (naproxen and esomeprazole), tramadol and fimasartan data were analyzed. We compared the 90% confidence interval (CI) for the geometric mean ratio (GMR) of a test product to a reference product using the multivariate HGLM and two conventional separate LMMs. RESULTS: We found that the 90% CIs for the GMRs of both AUC and Cmax from the multivariate HGLM were narrower than those from the separate LMMs: (0.843, 1.152) vs (0.825, 1.177) for Cmax of esomeprazole in fixed-dose combination data; (0.805, 0.931) vs (0.797, 0.941) for Cmax in tramadol data; (0.801, 1.501) vs (0.762, 1.578) for Cmax and (1.163, 1.332) vs (1.009, 1.341) for AUC in fimasartan data, consistent with the random subject effects from two separate LMMs being highly correlated in the three datasets (correlation coefficient r = 0.883; r = 0.966; r = 0.832). CONCLUSION: This multivariate HGLM had good performance in the bioequivalence test with multiple endpoints. This method would provide a more reasonable option to reduce the 90% CI by adding correlation parameters and thus an advantage especially in evaluating the bioequivalence of highly variable drugs with broad 90% CIs.

Pharmacology of Cenobamate: Mechanism of Action, Pharmacokinetics, Drug-Drug Interactions and Tolerability.

Cenobamate is one of the latest antiseizure medications (ASMs) developed for the treatment of focal onset seizures in adult patients. The recommended starting dose is 12.5 mg/day, titrated gradually to the target daily dose of 200 mg, which may be increased to a maximum of 400 mg/day based on clinical response. Although the high rate of seizure freedom observed in randomized, placebo-controlled clinical trials has resulted in exciting expectations, further clinical studies are needed to better define its clinical profile. Cenobamate is characterized by a peculiar pharmacology regarding both pharmacodynamics and pharmacokinetics. The mechanism of action has only partly been described, with the drug acting on voltage-gated sodium channels through a pronounced action on persistent rather than transient currents. Cenobamate also acts as a positive allosteric modulator of GABAA receptors independently from the benzodiazepine binding site. The bioavailability of cenobamate is not influenced by other drugs, except phenytoin; it can inhibit cytochrome P450 (CYP) 2C19 and induce CYP3A4 and 2B6, and hence can potentially interact with many drugs (e.g. dose adjustments may be required for lamotrigine, carbamazepine and clobazam). The pharmacokinetics of cenobamate are not linear and dosage increases imply a disproportional increase in plasma levels, particularly at doses higher than 300 mg. The most common and dose-related adverse effects associated with cenobamate include central nervous system-related symptoms, mainly somnolence, dizziness, diplopia, and disturbances in gait and coordination. A somewhat higher incidence of adverse events has been observed in patients concomitantly treated with sodium channel blockers. The most relevant safety issues are currently represented by the risk of severe skin reactions (apparently avoidable by a slow titration) and QT shortening (the drug is contraindicated in patients with familial short QT syndrome or taking QT-shortening drugs). Overall, cenobamate is a promising ASM with an intriguing and not fully understood mechanism of action; pharmacokinetic issues need to be considered in clinical practice.

UPLC-MS/MS assay of Tedizolid in rabbit aqueous humor: Application to ocular pharmacokinetic study.

Tedizolid phosphate (TZP) a prodrug of Tedizolid (TDZ) is a novel oxazolidinone antibiotic, used for the treatment of acute bacterial skin, skin structure infections and other serious gram positive and MRSA infections. In the present study, a sensitive UPLC-MS/MS analytical method was developed and validated for the quantification of TDZ in rabbit's aqueous humor (AqH) by using linezolid as internal standard (IS). Both TDZ and IS were separated on an Acquity™ HILIC column using an isocratic mobile phase comprising of acetonitrile: 20 mM ammonium acetate (85:15, v/v), eluted at 0.3mLmin-1 flow rate with total run time of 3 min. The AqH samples were processed by protein precipitation method by using acetonitrile as precipitating agent. TDZ and IS were detected in positive mode using electrospray ionization source. The precursor to product ion transitions at m/z 371.15 to 343.17 for TDZ and m/z 338.18 to 296.22 for IS were used for the quantification in multiple reaction monitoring mode. The calibration curve was linear in the concentration range of 4.98-1000ngmL-1 and the lower limit of detection was 1.97ngmL-1 only. The method was validated following US-FDA-guidelines and the results of validation parameter were found within the set limits. The developed UPLC-MS/MS method was fast, sensitive and reliable for the quantification of TDZ in the rabbit AqH and was successfully employed for ocular pharmacokinetic study of TDZ in AqH after topical ocular application of TZP-containing formulations in rabbit eyes.

Novel Antimalarial Tetrazoles and Amides Active against the Hemoglobin Degradation Pathway in Plasmodium falciparum.

Malaria control programs continue to be threatened by drug resistance. To identify new antimalarials, we conducted a phenotypic screen and identified a novel tetrazole-based series that shows fast-kill kinetics and a relatively low propensity to develop high-level resistance. Preliminary structure-activity relationships were established including identification of a subseries of related amides with antiplasmodial activity. Assaying parasites with resistance to antimalarials led us to test whether the series had a similar mechanism of action to chloroquine (CQ). Treatment of synchronized Plasmodium falciparum parasites with active analogues revealed a pattern of intracellular inhibition of hemozoin (Hz) formation reminiscent of CQ's action. Drug selections yielded only modest resistance that was associated with amplification of the multidrug resistance gene 1 (pfmdr1). Thus, we have identified a novel chemical series that targets the historically druggable heme polymerization pathway and that can form the basis of future optimization efforts to develop a new malaria treatment.

Evaluation of Drug Dissolution Rate in Co-amorphous and Co-crystal Binary Drug Delivery Systems by Thermodynamic and Kinetic Methods.

In order to better explain and predict the dissolution characteristics of binary drug delivery systems (BDDSs), the dissolution behaviors of co-crystal (CC) and co-amorphous (CA) systems of sacubitril (SCB) and valsartan (VST) were evaluated in vitro and in vivo by thermodynamic and kinetic methods. The CCs of SCB and VST were prepared into a CA state through rotary evaporation. Solid-state properties were systematically evaluated. Herein, based on the results from previous studies of single-phase systems, we used thermodynamic methods to evaluate the increase in drug dissolution rate after BDDSs change from the crystalline to the amorphous state. After comparing the predicted and measured dissolution rate enhancement of the CC and CA systems, this paper attempts to explain the dissolution rate characteristics of the BDDSs. We then evaluated the bioavailability of two BDDSs in beagle dogs to confirm that there was no discrepancy in vivo with the results obtained in vitro. The results exhibited that there is strong intermolecular interaction between SCB and VST and good physical stability for the CA system. Compared with the CC, the bioavailability of SCB and VST in the CA system increased by 313.9% and 130.5%, respectively. The predicted dissolution rate ratio between CC and CA systems and their actual intrinsic dissolution rates differed by only a factor of 2.5, demonstrating the good correlation between the predicted and measured values. In the future, this method could be expanded to a variety of new samples and exciting drug prospects.

PK/PD modeling of a clazosentan thorough QT study with hysteresis in concentration-QT and RR-QT.

Clazosentan's potential QT liability was investigated in a thorough QT study in which clazosentan was administered intravenously as a continuous infusion of 20 mg/h immediately followed by 60 mg/h. Clazosentan prolonged the placebo-corrected change-from-baseline QT interval corrected for RR with Fridericia's formula (ΔΔQTcF) with the maximum QT effect occurring 4 h after the maximum drug concentration, apparently associated with vomiting. The delayed effect precluded the standard linear modeling approach. This analysis aimed at characterizing the concentration-QT relationship in consideration of RR-QT hysteresis, concentration-ΔΔQTcF hysteresis, and the influence of vomiting. Nonlinear mixed-effects modeling was applied to characterize pharmacokinetics and pharmacodynamics, i.e., ΔΔQTcF. Simulations were used to predict ΔΔQTcF for expected therapeutic dose used in Phase 3 clinical development. Correction for RR-QT hysteresis did not influence ΔΔQTcF to a relevant extent. Pharmacokinetics of clazosentan were best described by a linear two-compartment model. The delayed QT prolongation was characterized by an indirect-response model with loglinear drug effect. Vomiting had no statistically significant influence on QT prolongation despite apparent differences between subjects vomiting and not vomiting, probably since vomiting occurred mostly after the main QT prolongation. Following a simulated 3-h infusion of 15 mg/h of clazosentan, the upper bound of the predicted 90% CI for mean ΔΔQTcF was expected to exceed the 10-ms regulatory threshold of concern with maximum effect 3.5 h after end of infusion. TRN: NCT03657446, 05 Sep 2018.

Simultaneous determination of sacubitrilat and fimasartan in rat plasma by a triple quad liquid chromatography-tandem mass spectrometry method utilizing electrospray ionization in positive mode.

An LC-tandem mass spectrometry method was developed and validated for the simultaneous quantitation of fimasartan and sacubitrilat using positive ion mode. The protein precipitation method was employed for the extraction of fimasartan, sacubitrilat and alprazolam (internal standard) from rat heparinized plasma. Baseline separation of the analytes was accomplished using an ACE-5, C18 (4.6 × 50 mm) column and gradient elution of mobile phase A (5 mm ammonium formate and 0.1% formic acid in purified water) and B (acetonitrile:methanol, 80:20; v/v). All peaks of interest were eluted within a 5-min runtime. The quantitation was achieved in the selected reaction monitoring mode. The developed method was validated as per US Food and Drug Administration guidelines and met the pre-defined acceptance criteria. The method showed linearity from 5 to 10,000 ng/mL. The accuracy/precision of intra- and inter-batch assays was 96.64%/2.05% to 109.17%/13.70% and 100.74%/3.76% to 106.39%/9.75% for fimasartan and 100.02%/1.49% to 113.80%/9.38% and 100.75%/2.31% to 108.40%/7.74% for sacubitrilat, respectively, in rat plasma. Fimasartan and sacubitrilat remained stable in rat plasma at different experimental conditions up to 21 days. The developed method was sensitive, selective and applied successfully to monitor plasma concentrations of fimasartan and sacubitrilat in an oral rat pharmacokinetic study.

Safety of Candesartan, Amlodipine, and Atorvastatin in Combination: Interaction Study in Healthy Subjects.

For efficient cardiovascular risk protection antihypertensive treatment is often combined with cholesterol-lowering treatment, although solid data of interaction and side effects are missing. This is a prospective, single-center interaction study conducted in a fixed sequence design at steady state of candesartan, amlodipine, and atorvastatin. Five-day monotherapy of candesartan 8 mg was followed by 5-day atorvastatin 40 mg monotherapy and subsequently 9-day amlodipine 5 mg monotherapy; each treatment separated by washout phases. Immediately after amlodipine monotherapy, all 3 drugs were administered concomitantly for 5 days. Pharmacokinetic parameters as well as safety were assessed. Eighteen healthy subjects enrolled and completed the study. No significant difference in the maximum concentration (Cmax ) and the area the under plasma concentration-time curve (AUC) for amlodipine and AUC of atorvastatin was detected following combination versus monotherapy. Cmax of atorvastatin decreased slightly but clinically not relevantly when given in combination. A statistically significant but not below 0.80-fold decrease between candesartan following combination vs monotherapy was detected for Cmax and AUC. In general, all treatments were well tolerated. Concluding, systemic exposure of candesartan, amlodipine, and atorvastatin is not clinically significantly changed upon coadministration. These data support a fixed-dose combination of the 3 components for dual cardiovascular risk prevention.