Noninvasive measurement of pharmacokinetics by near-infrared fluorescence imaging in the eye of mice

Michael Dobosz,Kay-Gunnar Stubenrauch,Werner Scheuer,Franz Osl,Steffen Strobel

doi:10.1117/1.jbo.19.1.016022

Abstract

For generating preclinical pharmacokinetics (PKs) of compounds, blood is drawn at different time points and levels are quantified by different analytical methods. In order to receive statistically meaningful data, 3 to 5 animals are used for each time point to get serum peak-level and half-life of the compound. Both characteristics are determined by data interpolation, which may influence the accuracy of these values. We provide a method that allows continuous monitoring of blood levels noninvasively by measuring the fluorescence intensity of labeled compounds in the eye and other body regions of anesthetized mice. The method evaluation was performed with four different fluorescent compounds: (i) indocyanine green, a nontargeting dye; (ii) OsteoSense750, a bone targeting agent; (iii) tumor targeting Trastuzumab-Alexa750; and (iv) its F(ab')2-alxea750 fragment. The latter was used for a direct comparison between fluorescence imaging and classical blood analysis using enzyme-linked immunosorbent assay (ELISA). We found an excellent correlation between blood levels measured by noninvasive eye imaging with the results generated by classical methods. A strong correlation between eye imaging and ELISA was demonstrated for the F(ab')2 fragment. Whole body imaging revealed a compound accumulation in the expected regions (e.g., liver, bone). The combination of eye and whole body fluorescence imaging enables the simultaneous measurement of blood PKs and biodistribution of fluorescent-labeled compounds.

Highlights

The study of the time course of a drug in the body is a key determinant in the selection of a drug candidate
The continuously increasing half-life values may be attributed to the limited clearing capacity of the liver and the cumulative dose effect of the three applications leading to an accumulation of indocyanine green (ICG) in the blood
We examined if the injection of escalating dosages of ICG correlated with increased fluorescence signal intensities (SIs) in the eye [Fig. 3(a) and Video 3]

Summary

Introduction

The study of the time course of a drug in the body is a key determinant in the selection of a drug candidate. Pharmacokinetic (PK) provides information that can guide future animals and clinical studies for the selection of the dose levels and frequency of administration. Multiple steps are involved in PK studies, e.g., formulation, animal dosing and sampling, sample processing and analysis, and PK regression and data reporting. The maximum observed concentration in the concentration–time profile (Cmax) and the time to reach that peak-level (tmax) are important descriptors of the extent and nature of drug exposure. In the drug discovery setting, secondary or derived parameters such as half-life (t1∕2) or area under the curve (AUC) have increased practical importance. The half-life is generally used as a guide to determine the dose interval of a

Methods

Results

Discussion

Conclusion