There are a variety of hydrolytic enzymes in plasma. If the compound to be studied has affinity for one of these enzymes and has a hydrolyzable group at a suitable position, then the compound can be decomposed in plasma. Thereby affecting the accuracy of biological test conclusions or making it unable to reach an effective therapeutic concentration in the body. Lead compound optimization to improve the plasma stability of the compound helps to improve the pharmacokinetic and pharmacodynamic properties of the compound in vivo. In drug development, the determination of the stability of a compound in rat plasma and the plasma protein binding rate can provide a basis for clinical drug development and research of the compound and establish a corresponding detection method.
Some compounds containing specific functional groups are easy to decompose in the blood. These functional groups mainly include ester groups, amides, lactones, carbamates, lactams, sulfonamides, and peptide structures. However, unstable compounds often have higher clearance rates and shorter half-lives, resulting in poor in vivo pharmacokinetics and pharmacodynamic properties. If only the liver metabolism stability of the compound is concerned and the plasma stability is ignored during the development of new drugs, the problem of in vivo stability of the compound may not be effectively solved. By optimizing the lead compound, modifying the structure of the compound to improve the plasma stability of the compound, prolong the action time of the drug in the body, increase the exposure in the body, reduce the clearance rate of the compound, and increase the bioavailability, thereby improving its pharmacokinetics and Pharmacodynamic properties are necessary for drug development. Medicilon provides research on plasma protein binding rate, whole blood/plasma stability, liver microsomal metabolism test, metabolic phenotype research, CYP450 induction test, CYP450 inhibition test, drug-drug interaction, etc. to help customers in drug development .
Plasma stability is one of the important factors in the evaluation of drug-readiness. If a researcher investigates the stability of short peptide proteasome inhibitors with potential anti-tumor activity in mouse plasma and whole blood, it provides a reference for further research on the druggability of compounds 1 and 2 to be studied. The researcher took mouse blank plasma and whole blood, added solutions of 1 and 2 at a certain concentration, and took samples after 37 incubation for different times. The remaining amount of the compound in the plasma and whole blood was determined by LC-MS/MS, and the compound was calculated separately Half-life and degradation rate in mouse whole blood and plasma . The results of the study found that the linear range of the compound in mouse plasma and whole blood was 70.0～5600.0ng•mL-1, and the lower limit of quantification (LLOQ) was 70.0ng•mL-1. The intra-day and inter-day coefficient of variation (RSD) are both less than 10%, which meets the analysis requirements of biological samples. After the compound was incubated with plasma and whole blood for different times, the drug concentration in whole blood was lower than the plasma drug concentration at the same time. The half-lives of compound 1 and 2 in whole blood were 2.98h and 1.85h, and the half-lives in plasma were 7.26. h and 4.76h. The study found that the stability of compounds 1 and 2 in mouse plasma was higher than their stability in whole blood, and compound 1 was more stable than compound 2 in mouse plasma and whole blood.
Some researchers used high-performance liquid phase as a detection method, using ultrafiltration to investigate the binding of dihydrooleanolic acid to rat plasma proteins . The results of the study found that when the mass concentration of dihydrooleanolic acid in rat plasma is 1-20 μg/ml, the plasma stability is good, and the rat plasma protein binding rate is high without concentration dependence. The ultrafiltration method established in this study can meet the requirements for the determination of plasma protein binding rate, and the established HPLC detection method meets the in vitro test of dihydrooleanolic acid.
In short, in the early stage of drug development, the plasma stability of lead compounds should be evaluated, and potentially unstable structures should be discovered as early as possible and necessary structural modifications should be made, or lead compounds with better stability should be selected for further pharmacological activity and metabolism. The optimization of properties is essential for drug development.
 LC-MS/MS to study the stability of new peptidomimetic proteasome inhibitors in plasma and whole blood[J].
 Study on the plasma stability and protein binding rate of dihydrooleanolic acid by high performance liquid chromatography [J].