Effects of low temperature on blood-to-plasma ratio measurement

摘要

The blood-to-plasma ratio (R-b) is an important property of drug candidates. R-b is applied widely in drug discovery to convert plasma pharmacokinetic parameters to the respective parameters in blood and to develop in vitro-in vivo correlations. Some compounds such as prodrugs, soft drugs, and peptide mimetics are unstable in blood, making accurate in vitro R-b measurement challenging, but necessary. Low temperature often reduces the rate of enzymatic and chemical reactions and increases the stability of labile compounds in biomatrices. In this study, the effects of 4 degrees C on R-b measurement were evaluated using a set of structurally diverse compounds with various binding and red blood cell (RBC) transport mechanisms. The results indicate that a 4 degrees C R-b method provides comparable R-b values to the 37 degrees C method for most compounds and can therefore be applied to measure the R-b of unstable compounds in drug discovery. In some rare cases, when compounds have a high affinity to specific RBC components (e.g., carbonic anhydrase), the 4 degrees C method may underestimate R-b. In these specific cases, the use of appropriate inhibitors to stabilize unstable compounds is recommended.