Effect of Truncating AUC at 12, 24 and 48 hr When Evaluating the Bioequivalence of Drugs with a Long Half-Life

Exploring various measures of the area under the curve for the assessment of dose-proportionality and estimation of bioavailability

OBJECTIVE

In pharmacokinetics, the area under the concentration versus time curve (AUC) extrapolated to infinity (AUC0-∞) is the preferred metric but it is not always possible to have a reliable estimate of the terminal phase half-life. Here we sought to explore the accuracy of three different area measures to accurately identify dose proportionality and bioavailability.

METHODS

One to three compartment model simulations with different doses for dose-proportionality or different rates and/or extents of bioavailability. Area measures evaluated were AUC0-∞, to the last quantifiable concentration (AUCtlast), and to a common time value (AUCt').

RESULTS

Under linear pharmacokinetics, AUCt' provided the most accurate measure of dose proportionality. Except for the one compartment model where AUC0-∞ provided the best predictor of the true measure, there was no clear advantage to the use of either of the three measures of AUC.

CONCLUSION

With uncertainty about the terminal phase half-life, the use of AUCt' can be a very useful and even the preferred measure of exposure for use in assessing proportionality in exposure between doses. The choice of AUC measure in bioavailability is less clear and may depend on compartmental nature of the drug, and study parameters including assay sensitivity and sampling protocols.

Evaluation of Truncated AUC as an Alternative Measure to Assess Pharmacokinetic Comparability in Bridging Biologic-Device Using Prefilled Syringes and Autoinjectors

Pharmacokinetic (PK) comparisons between therapeutic biologics have largely been based on the total area under the concentration-time curve (AUC) and the maximum concentration (Cmax ). For biologics with a long half-life, a PK comparability study may be long in duration and costly to conduct. The goal of this study was to evaluate whether a truncated AUC (tAUC) can be used to assess PK comparability when bridging prefilled syringe (PFS) and autoinjector (AI) treatment options for biologics with a long half-life. Fifteen biologics license applications (BLAs) were included to determine the concordance and geometric percent coefficient of variation (%CV) between tAUCs evaluated on days 7, 14, 21, and 28 and AUC evaluated to infinity (AUC0-inf ). Concordance is established if the tAUCs are comparable with AUC0-inf . Trial simulation was performed to examine the effect of the absorption rate constant (ka ) and sample size on the concordance of tAUCs. The tAUCs evaluated on day 14, 21, and 28 had 100% concordance with AUC0-inf for all 15 BLAs. The concordance of tAUC evaluated at day 7 was 87.5%. Based on the trial simulation, tAUC evaluated to day 28 post-dose can achieve high concordance (≥85%) for biologics exhibiting linear or nonlinear elimination with a ka of ≥0.1/day and with a sample size of 70 subjects per arm. tAUC appears to be a promising alternative PK measure, relative to AUC0-inf , for PK comparability assessments.

Preparation and in vitro/vivo evaluation of folate-conjugated pluronic F87-PLGA/TPGS mixed nanoparticles for targeted drug delivery

AIM

Folate-conjugated Pluronic F87-poly(lactic-co-glycolic acid) block copolymer (FA-F87-PLGA) was synthesized to encapsulate anticancer drug Paclitaxel (PTX) for targeted drug delivery. To further improve the curative effect, D-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS or Vitamin E TPGS) was added to form FA-F87-PLGA/TPGS mixed NPs.

METHODS

FA-F87-PLGA was synthesized by the ring-opening polymerization and the structure was characterized. PTX-loaded nanoparticles were prepared with the nanoprecipitation method. The physicochemical characteristics were studied to determine the appropriate dose ratio of the FA-F87-PLGA to TPGS. The cytotoxicity against Ovarian Cancer Cells (OVCAR-3) was determined by MTT assay. The Area-Under-the Curve (AUC) and half-life were measured in the vivo pharmacokinetic studies.

RESULTS

Based on the optimization of particle size and embedding rate of PTX-loaded mixed NPs, the appropriate dosage ratio of FA-F87-PLGA to TPGS was finally determined to be 5:3. According to in vitro release studies, the cumulative release rate of PTX-loaded FA-F87-PLGA/TPGS mixed NPs was 92.04%, which was higher than that of nanoparticles without TPGS. The cytotoxicity studies showed that the IC50 value of PTX-loaded FA-F87-PLGA/TPGS decreased by 75.4 times and 19.7 times after 72 h treatment compared with free PTX injections and PTX-loaded FA-F87-PLGA NPs, respectively. In vivo pharmacokinetic studies indicated that FA-F87-PLGA/TPGS mixed NPs had a longer drug metabolism time and a larger Area-Under-the-Curve (AUC) compared with free PTX injections.

CONCLUSION

FA-F87-PLGA/TPGS mixed NPs are potential candidates for targeted drug delivery systems.