Gangadhar Sunkara

Expression of Multidrug Resistance-Associated Protein (MRP) in Human Retinal Pigment Epithelial Cells and Its Interaction with BAPSG, a Novel Aldose Reductase Inhibitor

AbstractPurpose. The objective of this study was to determine the expression and activity of multidrug resistance–associated protein (MRP) in the retinal pigment epithelial (RPE) cells and to further assess whether BAPSG, a novel anionic aldose reductase inhibitor, interacts with MRP. Methods. Functional and biochemical evidence for MRP was obtained in a human retinal pigment epithelial (ARPE–19) cell line and primary cultures of human retinal pigment epithelial (HRPE) cells. Fluorescein accumulation and efflux in the presence and absence of MRP inhibitors was used to obtain functional evidence for MRP. Western blots and RT–PCR were used to obtain biochemical evidence for MRP1. The influence of MRP inhibitors on BAPSG accumulation and efflux in ARPE–19 cells was determined to understand its interaction with MRP. Results. MRP inhibitors increased fluorescein accumulation and reduced efflux in RPE cells. Both cell types exhibited a 190–kDa western blot band corresponding to MRP1 protein and a 287 bp RT–PCR band corresponding to MRP1 mRNA. MRP inhibitors reduced BAPSG efflux and increased its accumulation in ARPE–19 cells. Conclusions. MRP is functionally and biochemically active in human RPE cells. Anionic BAPSG is a likely substrate for MRP.

Vildagliptin, a Novel Dipeptidyl Peptidase IV Inhibitor, Has No Pharmacokinetic Interactions With the Antihypertensive Agents Amlodipine, Valsartan, and Ramipril in Healthy Subjects

We conducted 3 open–label, multiple–dose, 3‐period, randomized, crossover studies in healthy subjects to assess the potential pharmacokinetic interaction between vildagliptin, a novel dipeptidyl peptidase IV inhibitor for the treatment of type 2 diabetes, and representatives of 3 commonly prescribed antihypertensive drug classes: (1) the calcium channel blocker, amlodipine; (2) the angiotensin receptor blocker, valsartan; and (3) the angiotensin‐converting enzyme inhibitor, ramipril. Coadministration of vildagliptin 100 mg with amlodipine 5 mg, valsartan 320 mg, or ramipril 5 mg had no clinically significant effect on the pharmacokinetics of these drugs. The 90% confidence intervals of the geometric mean ratios for area under the plasma concentration–time curve from time zero to 24 hours (AUC0–24h) and maximum plasma concentration (Cmax) for vildagliptin, amlodipine, and ramipril (and its active metabolite, ramiprilat) were contained within the acceptance range for bioequivalence (0.80–1.25). Valsartan AUC0–24h and Cmax increased by 24% and 14%, respectively, following coadministration of vildagliptin, but this was not considered clinically significant. Vildagliptin was generally well tolerated when given alone or in combination with amlodipine, valsartan, or ramipril in healthy subjects at steady state. No adjustment in dosage based on pharmacokinetic considerations is required should vildagliptin be coadministered with amlodipine, valsartan, or ramipril in patients with type 2 diabetes and hypertension.

Evaluation of Pharmacokinetic Interactions Between Vildagliptin and Digoxin in Healthy Volunteers

Vildagliptin is a novel antidiabetic agent that is an orally active, potent, and selective inhibitor of dipeptidyl peptidase IV, the enzyme responsible for degradation of the incretin hormones. This open‐label, randomized, 3‐period crossover study investigated the potential for pharmacokinetic interactions in 18 healthy subjects during coadministration of vildagliptin and digoxin. Subjects were randomized to receive each of 3 treatments: vildagliptin 100 mg qd, digoxin (0.5 mg, then 0.25 mg qd on days 2–7), and the combination vildagliptin/digoxin for 7 days. Coadministration of digoxin with vildagliptin had no effect on exposure to vildagliptin (geometric mean ratios [90% confidence interval]: AUC0‐24h, 0.99 [0.95–1.03]; Cmax, 0.95 [0.85–1.06]) or to digoxin (AUC0‐24h, 1.02 [0.94–1.12]; Cmax, 1.08 [0.97–1.20]). In addition, no changes in tmax, t1/2, and CL/F were observed for either drug. These results indicate that no dose adjustment is necessary when vildagliptin and digoxin are coadministered.

Effect of the novel oral dipeptidyl peptidase IV inhibitor vildagliptin on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects

ABSTRACT Objective: Vildagliptin is a potent and selective dipeptidyl peptidase‑IV (DPP‑4) inhibitor that improves glycemic control in patients with type 2 diabetes by increasing alpha and beta-cell responsiveness to glucose. This study assessed the effect of multiple doses of vildagliptin 100 mg once daily on warfarin pharmacokinetics and pharmacodynamics following a single 25 mg oral dose of warfarin sodium. Research design and methods: Open-label, randomized, two-period, two-treatment crossover study in 16 healthy subjects. Results: The geometric mean ratios (co-administration vs. administration alone) and 90% confidence intervals (CIs) for the area under the plasma concentration-time curve (AUC) of vildagliptin, R- and S‑warfarin were 1.04 (0.98, 1.11), 1.00 (0.95, 1.04) and 0.97 (0.93, 1.01), respectively. The 90% CI of the ratios for vildagliptin, R- and S‑warfarin maximum plasma concentration (Cmax) were also within the equivalence range 0.80–1.25. Geometric mean ratios (co-administration vs. warfarin alone) of the maximum value and AUC for prothrombin time (PTmax, 1.00 [90% CI 0.97, 1.04]; AUCPT, 0.99 [0.97, 1.01]) and international normalized ratios (INRmax, 1.01 [0.98, 1.05]; AUCINR, 0.99 [0.97, 1.01]) were near unity with the 90% CI within the range 0.80–1.25. Vildagliptin was well tolerated alone or co-administered with warfarin; only one adverse event (upper respiratory tract infection in a subject receiving warfarin alone) was reported, which was judged not to be related to study medication. Conclusions: Co-administration of warfarin with vildagliptin did not alter the pharmacokinetics and pharmacodynamics of R- or S‑warfarin. The pharmacokinetics of vildagliptin were not affected by warfarin. No dosage adjustment of either warfarin or vildagliptin is necessary when these drugs are co-medicated.

Dose Proportionality and the Effect of Food on Vildagliptin, a Novel Dipeptidyl Peptidase IV Inhibitor, in Healthy Volunteers

Vildagliptin is a potent and selective dipeptidyl peptidase IV inhibitor in development for the treatment of type 2 diabetes that improves glycemic control by enhancing α‐ and β‐cell responsiveness to glucose. Two open‐label, single‐dose, randomized, crossover studies in healthy subjects (ages 18–45 years) investigated the dose proportionality of vildagliptin pharmacokinetics (n = 20) and the effect of food (n = 24) on vildagliptin pharmacokinetics. There was a linear relationship (r2 = 0.999) between vildagliptin doses of 25, 50, 100, and 200 mg and area under the plasma concentration‐time curve from time zero to infinity (AUC0–∞) and maximum plasma concentration (Cmax). Dose proportionality was assessed using a statistical power model [X = α·(dose)β]. The 90% confidence intervals of the proportionality coefficient, β, for AUC0–∞ (1.15–1.19) and Cmax (1.04–1.14) indicated that deviations from dose proportionality were small (<7.7%). Doubling of dose led to 2.1‐ to 2.3‐fold increases in AUC0–∞ and Cmax but no dose‐dependent changes in time to reach Cmax or terminal elimination half‐life. Administration of vildagliptin 100 mg following a high‐fat meal decreased Cmax by 19% and AUC0–∞ by 10%. Vildagliptin displays approximately dose‐proportional pharmacokinetics over the 25‐ to 200‐mg dose range, and administration with food has no clinically relevant effect on vildagliptin pharmacokinetics.

Evaluation of the potential for steady-state pharmacokinetic interaction between vildagliptin and simvastatin in healthy subjects

ABSTRACT Background: Vildagliptin is an orally active, potent and selective inhibitor of dipeptidyl peptidase IV (DPP-4), the enzyme responsible for the degradation of incretin hormones. By enhancing prandial levels of incretin hormones, vildagliptin improves glycemic control in type 2 diabetes. Co-administration of vildagliptin and simvastatin, an HMG-CoA-reductase inhibitor may be required to treat patients with diabetes and dyslipidemia. Therefore, this study was conducted to determine the potential for pharmacokinetic drug–drug interaction between vildagliptin and simvastatin at steady-state. Methods: An open label, single center, multiple dose, three period, crossover study was conducted in 24 healthy subjects. All subjects received once daily doses of either vildagliptin 100 mg or simvastatin 80 mg or the combination for 7 days with an inter-period washout of 7 days. Plasma levels of vildagliptin, simvastatin, and its active metabolite, simvastatin β-hydroxy acid (major active metabolite of simvastatin) were determined using validated LC/MS/MS methods. Pharmacokinetic and statistical analyses were performed using WinNonlin and SAS, respectively. Results: The 90% confidence intervals of Cmax and AUCτ of vildagliptin, simvastatin, and simvastatin β-hydroxy acid were between 80 and 125% (bioequivalence range) when vildagliptin and simvastatin were administered alone and in combination. These data indicate that the rate and extent of absorption of vildagliptin and simvastatin were not affected when co-administered, nor was the metabolic conversion of simvastatin to its active metabolite. All treatments were safe and well tolerated in this study. Conclusions: The pharmacokinetics of vildagliptin, simvastatin, and its active metabolite were not altered when vildagliptin and simvastatin were co-administered.

A Biodegradable Injectable Implant Sustains Systemic and Ocular Delivery of an Aldose Reductase Inhibitor and Ameliorates Biochemical Changes in a Galactose-Fed Rat Model for Diabetic Complications

AbstractPurpose. To fabricate and characterize in vitro and in vivo performance of a sustained release biodegradable implant for N-4-(benzoylaminophenylsulfonyl glycine) (BAPSG), a novel aldose reductase inhibitor. Methods. The ability of BAPSG to inhibit aldose reductase activity and glucose-induced vascular endothelial growth factor (VEGF) expression was assessed in a retinal pigment epithelial cell line (ARPE-19). A poly (DL-lactic-co-glycolic acid) implant containing 50% w/w BAPSG was fabricated and characterized for drug loading, in vitro drug release, and the thermal behavior of the drug and the polymer. Implants were injected subcutaneously into a galactose-fed diabetic rat model and cataract scores, plasma and tissue drug levels, galactitol levels in the lens and the retina, glutathione levels in the plasma, lens, cornea and retina and VEGF expression in the retina were determined on or until 18 days. Results. BAPSG inhibited aldose reductase activity and reduced VEGF expression in ARPE-19 cells. Implants (1 × 4 mm), with a loading efficiency of 106 ∓ 7% for BAPSG, were fabricated. Upon implant fabrication, while the glass transition temperature of the polymer decreased, the melting point of the drug was not affected. In vivo drug release correlated well with in vitro release, with ≈44% drug release occurring in vivo by the end of 18 days. The implant reduced galactitol accumulation, glutathione depletion, cataract scores, and VEGF expression in galactose-fed rats. Conclusions. An injectable biodegradable implant of BAPSG sustained drug release in vitro and in vivo, and reduced galactitol accumulation, glutathione depletion, cataract scores, and VEGF expression in galactose-fed rats.

Iontophoretic in Vivo Transdermal Delivery of β-Blockers in Hairless Rats and Reduced Skin Irritation by Liposomal Formulation

AbstractPurpose. To demonstrate the in vivo transdermal delivery and establish the comparative pharmacokinetics of five β-blockers in hairless rat. Methods. Intravenous dosing was initially done via jugular cannula. For iontophoretic delivery, current (0.1 mA/cm2) was applied for 2 h through a drug reservoir patch containing the β-blocker (10 mg/ml). Blood samples were collected and analyzed by stereoselective HPLC assays. Any irritation resulting from patch application was quantified by a chromameter. Multilamellar liposomal formulation was prepared by the thin-film hydration method and converted to unilamellar liposomes by extrusion. Results. With transdermal iontophoresis, therapeutically relevant amounts of propranolol (83.78 ± 7.4 ng/ml) were delivered within an hour and lasted for up to 4 h. Cmax (185.1 ± 56.8 ng/ml) was reached at hour 3. A significantly higher amount (p < 0.05) of sotalol HCl was delivered compared to other β-blockers. There was no significant difference in the S/R ratio of AUC0-t for enantiomers after both intravenous and transdermal delivery. Skin irritation was significantly reduced (p < 0.05) when a liposomal formulation of the propranolol base was used rather than the base itself. Conclusions. The comparative pharmacokinetics of intravenous and transdermal iontophoretic delivery of five β-blockers in hairless rats was established. It was shown that there is no stereoselective permeation.

Influence of pH and Temperature on Kinetics of Ceftiofur Degradation in Aqueous Solutions

The objective of this study was to evaluate the stability of ceftiofur (1mgmL‐1)in aqueous solutions at various pH (1, 3, 5, 7.4 and 10) and temperature (0, 8, 25, 37 and 60°C) conditions. The ionic strength of all these solutions was maintained at 0.5 M. Ceftiofur solutions at pH 5 and 7.4 and in distilled water (pH = 6.8) were tested at all the above temperatures. All other solutions were tested at 60°C. Over a period of 84 h, the stability was evaluated by quantifying ceftiofur and its degradation product, desfuroylceftiofur, in the incubation solutions. HPLC was used to analyse these compounds.

Pharmacokinetic and pharmacodynamic properties of canakinumab in patients with gouty arthritis

Pharmacokinetics and pharmacodynamics of the anti‐interleukin (IL)‐1β monoclonal antibody, canakinumab, in gouty arthritis patients from three studies are reported. Canakinumab has low serum clearance (0.214 L/day), low steady‐state volume of distribution (7.44 L), a 25.8‐day half‐life, and approximately 60% subcutaneous absolute bioavailability in a typical 93‐kg patient. Creatinine clearance had a small positive impact on serum canakinumab clearance that is not likely to be clinically relevant. Binding to circulating IL‐1β was demonstrated by increases in total serum IL‐1β following canakinumab dosing. Total IL‐1β kinetics and canakinumab pharmacokinetics were characterized by a population‐based pharmacokinetic‐binding model, where the estimated apparent in vivo dissociation constant (signifying binding affinity of canakinumab to circulating IL‐1β) was 0.99 nmol/L in gouty arthritis patients. Canakinumab treatment provided rapid, sustained decreases in C‐reactive protein and serum amyloid A, provided superior pain relief to triamcinolone acetonide, and increased time to first recurrent attack (P ≤ 0.01 favoring all canakinumab doses vs. triamcinolone acetonide).