Purpose: Exosomes are increasingly explored as delivery systems for small drug molecules, oligonucleotides and proteins. Characterization of exosomes pharmacokinetics has been primarily described using pseudo-quantitative imaging techniques that provided qualitative understanding of the biodistribution. Since accurate quantification of therapeutic at the target site is critical in preclinical drug development, we aimed to characterize the pharmacokinetics of therapeutic exosomes using valid quantitative methods in an orthotopic mouse model of hepatocellular carcinoma (HCC).
Methods: Exosomes were isolated from HEK293T cells and loaded with human cholesterol-labeled antisense miR-221 (chol-ASO-221-EVs) as a therapeutic. Surgeries were performed on athymic nude mice and luciferase-expressing hepatocellular carcinoma SK-Hep1 cells were injected into one lobe of the liver to generate orthotopic tumor xenografts. Upon confirmation of tumor growth in vivo, mice were injected with a single intravenous bolus dose of chol-ASO-221 exosomes (52 nmol/kg of chol-ASO-221) via tail vein. Blood and tissue samples were collected predose and at various time points up to 48 hours post dose. RT-qPCR was used for absolute quantification of ASO-221 in plasma and tissue samples. Both non-compartmental and compartmental analysis were used to estimate ASO-221 pharmacokinetics in plasma and liver.
Results: Plasma levels of ASO-221 followed an IV bolus two compartment model with a half-life of 1.2 hours. The average peak ASO-221 concentration in the liver was achieved at 12 hours, and therapeutic ASO-221 levels were maintained 48 hours post dose. Average peak tumor concentrations were 30 nM within this single dose study, though model simulations indicate that target concentration will be achieved with multiple dosing three times weekly.
Conclusion: We present novel quantitative plasma, liver and tumor pharmacokinetic data for the ASO-221 cargo packaged in therapeutic exosomes. The findings of this study will be helpful in guiding future efficacy and disposition studies of therapeutic exosomes in preclinical mouse models. Current work is ongoing to address more fundamental pharmacokinetic questions such as dose proportionality, blood to plasma ratio, and the effect of dosing route on the biodistribution of exosomes.
Jinmai Jiang– College of Pharmacy, University of Florida
Steve Pomeroy– College of Pharmacy, University of Florida
Anees Dauki– Division of Pharmaceutics & Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University
Xiaohua Zhu– Division of Pharmaceutics & Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University
Dhruvitkumar Sutaria– Postdoctoral Associate, University of Florida, Orlando, Florida
Thomas Schmittgen– College of Pharmacy, University of Florida
Mitch Phelps– Division of Pharmaceutics & Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University