Related Experiment Video
Updated: Jun 20, 2026
Generation of Subcutaneous and Intrahepatic Human Hepatocellular Carcinoma Xenografts in Immunodeficient Mice
Published on: September 25, 2013
Xenografted Tumors Share Comparable Fraction Unbound and Can Be Surrogated by Mouse Lung Tissue
Min Wang1, Sandip Kuldharan1, Aravind Shenoy1
1Pharmacokinetics and Drug Metabolism, Amgen Inc., South San Francisco, California (M.W., U.P.D.); Pharmacokinetics and Drug Metabolism, Syngene Amgen Research & Development Center, Bangalore, India (S.K., A.S., S.R.); and Amgen Research (K.R., T.O.) and Pharmacokinetics and Drug Metabolism (J.W.), Amgen Inc., Thousand Oaks, California.
Abstract:
Free (unbound) drug concentration at the site of action is the key determinant of biologic activity since only unbound drugs can exert pharmacological and toxicological effects. Unbound drug concentration in tumors for solid cancers is needed to understand/explain/predict pharmacokinetics, pharmacodynamics, and efficacy relations. Fraction unbound (fu ) in tumors is usually determined across several xenografted tumors derived from various cell lines in the drug discovery stage, which is time consuming and a resource burden. In this study, we determined the fu values for a set of diverse compounds (comprising acid, base, neutral, zwitterion, and covalent drugs) across five different xenografted tumors and five commercially available mouse tissues to explore the correlation of fu between tumors and the possibility of surrogate tissue(s) for tumor fu (fu,tumor) determination. The crosstumor comparison showed that fu,tumor values across tumors are largely comparable, and systematic tissue versus tumor comparison demonstrated that only lung tissue had comparable fu to all five tumors (fu values within twofold change for >80% compounds in both comparisons). These results indicated that mouse lung tissue can be used as a surrogate matrix for a fu,tumor assay. This study will increase efficiency in fu,tumor assessment and reduce animal use (adapting the replace, reduce, and refine principle) in drug discovery. SIGNIFICANCE STATEMENT: The free drug concept is a well accepted principle in drug discovery research. Currently, tumor fraction unbound (fu,tumor) is determined in several tumors derived from different cell lines to estimate free drug concentrations of a compound. The results from this study indicated that fu,tumor across xenografted tumors is comparable, and fu,tumor can be estimated using a surrogate tissue, mouse lung. The results will increase efficiency in fu,tumor assessment and reduce animal use in drug discovery.
Insights
Free drug concentration in tumors is crucial for drug efficacy. This study found that mouse lung tissue can serve as a reliable surrogate for measuring unbound drug levels in tumors, improving efficiency and reducing animal use in drug discovery.
Area of Science:
- Pharmacology
- Drug Discovery
- Toxicology
Background:
- Free drug concentration at the site of action dictates biologic activity.
- Accurate unbound drug concentration in tumors is essential for predicting pharmacokinetics, pharmacodynamics, and efficacy in solid cancers.
- Current methods for determining tumor unbound fraction (f_u,tumor) are time-consuming and resource-intensive.
Purpose of the Study:
- To explore the correlation of unbound drug fraction (f) across different xenografted tumors.
- To identify potential surrogate tissues for determining tumor unbound fraction (f_u,tumor).
- To enhance the efficiency of f_u,tumor assessment and reduce animal usage in drug discovery.
Main Methods:
- Determined f values for diverse compounds across five xenografted tumors and five mouse tissues.
- Compared f_u,tumor values across different tumor types.
- Systematically compared f values in mouse tissues versus tumors.
Main Results:
- Unbound drug fraction (f_u,tumor) values were largely comparable across different xenografted tumors.
- Mouse lung tissue demonstrated comparable f values to all five tested tumors (>80% compounds within twofold change).
- Mouse lung tissue can be utilized as a surrogate matrix for f_u,tumor assays.
Conclusions:
- Mouse lung tissue serves as a viable surrogate for estimating unbound drug fraction in tumors.
- Utilizing lung tissue can significantly increase efficiency in f_u,tumor assessment.
- This approach supports the 'replace, reduce, and refine' principle by potentially decreasing animal use in drug discovery.
