A functional group-guided approach to aptamers for small molecules.

Aptameric receptors are important biosensor components, yet our ability to identify them depends on the target structures. We analyzed the contributions of individual functional groups on small molecules to binding within 27 target-aptamer pairs, identifying potential hindrances to receptor isolation-for example, negative cooperativity between sterically hindered functional groups. To increase the probability of aptamer isolation for important targets, such as leucine and voriconazole, for which multiple previous selection attempts failed, we designed tailored strategies focused on overcoming individual structural barriers to successful selections. This approach enables us to move beyond standardized protocols into functional group-guided searches, relying on sequences common to receptors for targets and their analogs to serve as anchors in regions of vast oligonucleotide spaces wherein useful reagents are likely to be found.

Placental and breastmilk transfer of voriconazole to offspring from pregnant and lactating bottlenose dolphins (Tursiops truncatus).

Fungal pneumonia is a common disease in bottlenose dolphins (Tursiops truncatus), including pregnant and lactating ones. Voriconazole (VRCZ) is commonly used to treat respiratory fungal infections in this species; however, it is unknown whether VRCZ is transferred via the placenta and breastmilk and whether its usage is safe in pregnant and lactating dolphins. We measured VRCZ concentrations in breastmilk and dams', umbilical cord, and calves' plasma samples from four dam-calf dolphin pairs in the Port of Nagoya Public Aquarium, Japan, treated with or without VRCZ. Three pregnant and/or lactating dams were administered VRCZ (loading dose 1.5-2.3 mg/kg, for 3 days; maintenance dose 1.5-3.1 mg/kg, every 5-18 days), twice daily, orally, without side effects in dams or calves. VRCZ was detected in two dams' umbilical cord plasma (0.14 and 2.35 µg/ml) and in one calf's plasma (0.18 µg/ml), collected immediately after birth. Further, VRCZ was detected in breastmilk samples (maximum 13.45 µg/ml) from three VRCZ-administered dams and in plasma from three calves (maximum 7.54 µg/ml) given or nursed from VRCZ-administered dams' breastmilk. The calves' plasma VRCZ concentrations varied, depending on the amount of breastmilk and food consumed. VRCZ concentrations were higher in breastmilk samples than in dams' plasma. To our knowledge, this is the first report on placental and breastmilk VRCZ transfer to offspring in bottlenose dolphins. During VRCZ medication in pregnant and lactating bottlenose dolphins, it is crucial to monitor plasma VRCZ concentrations and any side effects in dams as well as in their calves.

Paper spray high-resolution accurate mass spectrometry for quantitation of voriconazole in equine tears.

Paper spray high-resolution accurate mass spectrometry is a fast and versatile analysis method. This ambient ionization technique enables the quantitation of xenobiotics in complex biological matrices without chromatography or conventional sample extraction. The simplicity, rapidity, and affordability of the paper spray mass spectrometry (PS-MS) method make the technique especially attractive for clinical investigations where fast and affordable sample analysis is crucial. A new PS-MS method for the quantitation of voriconazole in equine tears was developed and validated. For a concentration range of 10 to 1000 ng/mL, good linearity (R2 > 0.99), inter- and intra-run precision (coefficient of variation (CV) max. 11.9%), accuracy (bias of the nominal concentration ± 13.9%), and selectivity (signal areas of the double blanks represent 0.13 ± 0.05% of the lower limit of quantitation (LLOQ) signal in equine tears) were observed. The quantitation of voriconazole was based on three product ions and calculated relative to the isotope-labeled internal standard, voriconazole-d3, which had a final concentration of 250 ng/mL in the standards and samples. The matrix effect of the method showed an ionization suppression by reduction of the voriconazole response to 63.6%, 70.2%, and 81.9% for 30 ng/mL, 450 ng/mL, and 900 ng/mL in equine tears compared with voriconazole in solvent (methanol:water, 50:50, v:v). The method was used to analyze 126 study samples collected for a pharmacokinetic study investigating a novel approach for treatment of fungal keratitis in horses. Therefore, the integrity of the sample dilution (n = 6, CV 6.90%, and bias of nominal concentration + 8.40%) and the carryover effect (increase from 0.33 ± 0.21% to 1.33 ± 0.89% of the signal of the LLOQ) was further investigated. To our knowledge, this method is the first application of PS-MS for quantitation of drug concentrations in tears from any species.

Comparison of the Ocular Penetration and Pharmacokinetics Between Natamycin and Voriconazole After Topical Instillation in Rabbits.

PURPOSE: To investigate the ocular penetration of natamycin (NAT) and voriconazole (VRC) after topical instillation in New Zealand white rabbits using simplified liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance liquid chromatography. METHODS: Seventy-eight healthy rabbits were randomly divided into 3 groups. In the first 2 groups, 72 rabbits were used for single-dose testing (36 for NAT, 36 for VRC), in which 50 µL of 5.0% NAT or 1.0% VRC was instilled into the rabbits' left eyes. In the 3rd group, 6 rabbits were used for repeated-dose testing in which 50 µL of 5.0% NAT was instilled into their left eyes 12 times (once per hour) during the daytime. These animals were sacrificed immediately to collect their aqueous humors and corneas. RESULTS: After a single topical instillation, the highest concentrations in the cornea and aqueous humor for VRC were 34.1 µg/g and 14.7 µg/mL, respectively. The permeability ratios of aqueous/cornea were from 0.1 to 1.26. The highest concentrations in cornea and aqueous humor for NAT were 299.3 ng/g and 27.1 ng/mL, respectively. The permeability ratios of aqueous/cornea were from 0.02 to 0.23. In the repeated-dose group, the NAT concentrations in the cornea and aqueous humor were 10,569 ng/g and 54.4 ng/mL, respectively. The permeability ratio was as low as 0.0051. CONCLUSION: The better corneal penetration of VRC suggests that it is more suitable for deep corneal fungal infections than NAT via topical ocular administration.

Simultaneous determination of voriconazole, posaconazole, itraconazole and hydroxy-itraconazole in human plasma using LCMS/MS.

INTRODUCTION: Invasive fungal infections are an increasing cause of mortality and morbidity in high risk patient populations such as those on immunosuppressive therapy. Triazole antifungals are recommended for the prevention and treatment of such infections. The aim of this study was to develop and validate a simple, sensitive and robust LCMS/MS method for the simultaneous analysis in human plasma of three frequently used antifungal drugs: voriconazole, posaconazole, and itraconazole. METHODS: Precipitation reagent, containing deuterated internal standards, is added to 50µL of plasma. The vials are vortexed before centrifugation. The organic supernatant is transferred to a polypropylene vial and 1µL is injected into the Waters Acquity® Ultra Performance Liquid Chromatography system coupled with a Waters Acquity® TQ Detector system. Chromatographic separation is achieved on a BEH C18 column using gradient elution with mobile phases consisting of 2mM ammonium acetate with 0.1% formic acid in water and methanol. Run time is <5min between injections. RESULTS: The evaluation of the LCMS/MS triazole method showed good precision (intra-assay CVs<6.7%, inter-assay CVs<8.3%). The lower limit of quantitation for all antifungal triazoles tested was 0.10mg/L. Passing Bablok comparisons of voriconazole (n=50) and posaconazole (n=50) showed good correlation with the current HPLC method (Voriconazole LCMS=0.94(HPLC)+0.03, r2=0.99; Posaconazole LCMS=1.18(HPLC)-0.04, r2=0.95). Passing Bablok comparisons of itraconazole and hydroxy-itraconazole (n=18) showed good agreement with an external referral laboratory's antifungal LCMS/MS method (Itraconazole LCMS=1.00(referral lab)+0.01, r2=0.99; Hydroxy-Itraconazole LCMS=1.05(referral lab)+0.04, r2=0.99). External quality assurance samples for posaconazole and voriconazole (n=12, UK NEQAS Antifungal Pilot Panel) were assayed 'blind' and results were in good agreement with consensus mean values (both r2=0.99). CONCLUSION: The rapid pre-analytical sample preparation procedure, short chromatographic time, limit of quantitation and linear range make this LCMS/MS method suitable for determination of plasma voriconazole, posaconazole, itraconazole and hydroxy-itraconazole levels in a high throughput laboratory.

Development and Validation of Voriconazole Concentration by LC-MS-MS: Applied in Clinical Implementation.

BACKGROUND: Voriconazole (VRZ) is a triazole antifungal used for treatment of invasive fungal infection, which is a life-threatening condition. Therapeutic drug monitoring is recommended for identifying the optimal dose in patients who have hepatic/renal impairment or reduced function of the CYP2C19 metabolizing enzyme. METHODS: One hundred microliters of sample plasma was extracted by protein precipitated with 200 µl of acetonitrile containing fluconazole as internal standard (IS). After vortexing and centrifugation, supernatant was dried and reconstituted with 100 µl of mobile phase (ACN: 0.1% formic acid in 10 mM Ammonium acetate) (50:50 v/v) before injected. The column was C18, 2.7 µm, 3.0 × 50 mm at flow rate of 0.5 ml/min with retention time of 0.5 and 0.75 min for VRZ and IS, respectively. The tandem mass spectrometer was set in multiple reactions monitoring (MRM) mode with the following transition; VRZ m/z 350.10→281.10 and 307.20→220.20 (IS). RESULTS: The accuracy and precision inter- and intra-day were less than 9%, over the range 0.05-10 µg/ml. The linearity was consistent (r2 = 0.9987) and recovery was more than 85.0% for both analyses. CONCLUSION: This method is applicable for routine monitoring of patients' VRZ plasma level with fast and accurate runtime to assess CYP2C19 genotype.

Development and characterization of the voriconazole loaded lipid-based nanoparticles.

The number of topical fungal infections is growing, mostly owing to immunosuppressive therapy. Several topical fungal infections, such as eye mycoses, can be treated by local administration of antimycotic drugs. One major group of the antifungal agents is triazole, such as voriconazole (VCZ), which is used as the first line treatment of aspergillosis. A disadvantage of VCZ is its low water solubility making the drug difficult to administer in a liquid preparation. The lipid-based nanoparticles (LNP) have attracted increasing attention due to their advantageous properties. Contrarily to the conventional carrier systems, LNP can improve the poor solubility of topically used drugs, such as VCZ. Therefore, LNP represents promising alternatives to traditional carrier systems. The aim of the study was to formulate VCZ loaded lipid-based nanoparticles (VCZ-LNP) by high pressure homogenization (HPH). The developed LNPs were characterized by particle size analysis, IR spectroscopy, differential scanning calorimetry, dialysis test and antifungal efficacy studies. The particle size of the optimized nanoparticles from the selected lipid base, Witepsol® W35, was 182±4.1nm after five cycles of homogenization at 600bar. The antifungal study confirmed that the optimized VCZ-LNP inhibited the fungus reproduction.

Therapeutic Drug Monitoring of Voriconazole in the Management of Invasive Fungal Infections: A Critical Review.

The broad-spectrum triazole antifungal agent voriconazole is highly efficacious against invasive fungal infections (IFIs) caused by Aspergillus spp. and Candida spp. IFIs are associated with high rates of mortality and morbidity, especially in vulnerable populations such as patients with hematopoietic stem cell transplant as well as other immunocompromised patients. Efficacy of voriconazole in these patients is critical to ensure positive outcomes and reduce mortality. However, a major limitation of voriconazole is the risk of adverse events such as hepatotoxicity and neurotoxicity. As such, therapeutic drug monitoring (TDM) has been suggested as a mechanism to optimize both efficacy and safety. The aim of this review was to summarize and evaluate evidence from the primary literature that assessed TDM outcomes for voriconazole as well as evaluate the association between CYP2C19 polymorphism and the clinical outcomes of voriconazole. Findings showed associations for both efficacy and safety outcomes with measurement of drug concentrations, yet exact targets or thresholds remain unclear. As such, TDM should be reserved for those patients not responding to therapy with voriconazole or those experiencing adverse drug reactions. Future studies should attempt to further define these populations within controlled settings. Studies that evaluated the effect of CYP2C19 genetic polymorphism on clinical outcomes found no significant relationship between CYP2C19 genotype and hepatotoxicity. These negative findings may be due to lack of power, use of phenotypes not well-defined, and the presence of other interacting factors that may impact voriconazole pharmacokinetics. Future well-designed studies are warranted to confirm these findings.

Pharmacokinetics and distribution of voriconazole in body fluids of dogs after repeated oral dosing.

The goal of this project was to determine the pharmacokinetics of voriconazole and its concentration in cerebrospinal fluid (CSF), aqueous humor, and synovial fluid in five healthy dogs following once daily oral dose of 6 mg/kg for 2 weeks. Body fluid and plasma drug concentrations were determined by high-performance liquid chromatography (HPLC). Mild to moderate gastrointestinal adverse effects were seen. The mean AUC0-24 : minimum inhibitory concentration (MIC) ratio was 15.23 for a chosen MIC of 1 µg/mL, which is lower than the recommended target of 20-25 and also lower than previously reported in dogs, perhaps reflecting induction of metabolizing enzymes by multiple dosing. Voriconazole concentrations in the CSF, aqueous humor, and synovial fluid were only 13-30% the concurrent plasma concentration, which is lower than previously reported in other species. Results of this study suggest that twice daily, administration may be necessary to maintain therapeutic plasma concentrations in dogs but further studies are warranted.