Calcein assay: a high-throughput method to assess P-gp inhibition

Area of Science:

• Pharmacology and Toxicology
• Drug Development
• Biochemistry

Background:

• Transporter-mediated drug-drug interactions (tDDI) involving ABCB1 are clinically significant.
• Early assessment of ABCB1 tDDI potential is crucial in drug development.
• Existing methods like digoxin transport inhibition have limitations for high-throughput screening.

Purpose of the Study:

• To evaluate the Calcein assay for assessing ABCB1 tDDI potential.
• To compare the sensitivity and throughput of the Calcein assay with traditional methods.
• To investigate the impact of ABCB1 expression levels on assay results.

Main Methods:

• Utilized the Calcein assay in K562MDR cells.
• Compared Calcein assay results with digoxin transport inhibition in MDCKII-MDR1 cells.
• Applied the Calcein assay to cell lines with varying ABCB1 expression levels.

Main Results:

• The Calcein assay in K562MDR cells demonstrated higher sensitivity than digoxin transport inhibition in MDCKII-MDR1 cells.
• IC(50) values varied 10-100-fold across cell lines with different ABCB1 expression.
• Higher ABCB1 expression correlated with higher IC(50) values.

Conclusions:

• The Calcein assay is a sensitive, high-throughput alternative to digoxin transport inhibition for evaluating ABCB1 tDDI.
• The assay provides comparable selectivity but enhanced sensitivity.
• Results highlight the dependence of ABCB1 IC(50) values on expression levels and cell type.