OBJECTIVE To establish a UPLC detection method for simultaneous determination of mycophenolic acid(MPA) and its glucuronide(MPAG) in plasma of rats, and to investigate gender-related pharmacokinetic characteristics of mycophenolic acid. METHODS Twelve SD rats(half male and half female) were intragastrically administrated with 90 mg·kg-1·d-1mycophenolate acetate, and blood was collected from periorbital vein at different time points after administration. Plasma samples were extracted by liquid-liquid extraction and drug concentrations of MPA and metabolite MPAG in plasma were determined using UPLC. The method was developed using Waters BEH C18 column. The gradient elution was performed at a flow rate of 0.35 mL·min-1 with the mobile phase acetonitrile solution (A)-0.1% formic acid aqueous solution(B). The detection wavelength was at 266 nm and column oven temperature was maintained at 40 ℃. The pharmacokinetic parameters were calculated by using DAS 2.0 software. RESULTS The linear relationship between peak area and concentrations of MPA and MPAG were good in the ranges of 0.31-160 µg·mL-1(R2=0.999 8) and 0.62-320 µg·mL-1(R2=0.999 4), respectively. Analytical methods of MPA and MPAG all met the requirements of the methodology. Pharmacokinetic parameters AUC0-t and Cmax of MPA and MPAG in female rats were higher than that in male rats(P<0.05 or P<0.01). In addition, the metabolic rate of genistein[UDP-glucuronosyltransferases(UGT)s substrate] and MPA in male rat liver microsomes were significantly faster than that in female rat liver microsomes. CONCLUSION This developed UPLC method is sensitive, accurate and specific, which is suitable to detect the concentrations of MPA and MPAG in the plasma. The pharmacokinetics of MPA and MPAG in rats are gender different, which may be related to the sex difference of UGTs metabolic enzyme activity.

Emerging SARS-CoV-2 variants have made COVID-19 convalescents susceptible to re-infection and have raised concern about the efficacy of inactivated vaccination in neutralization against emerging variants and antigen-specific B cell response. To this end, a study on a long-term cohort of 208 participants who have recovered from COVID-19 was conducted, and the participants were followed up at 3.3 (Visit 1), 9.2 (Visit 2), and 18.5 (Visit 3) months after SARS-CoV-2 infection. They were classified into three groups (no-vaccination (n = 54), one-dose (n = 62), and two-dose (n = 92) groups) on the basis of the administration of inactivated vaccination. The neutralizing antibody (NAb) titers against the wild-type virus continued to decrease in the no-vaccination group, but they rose significantly in the one-dose and two-dose groups, with the highest NAb titers being observed in the two-dose group at Visit 3. The NAb titers against the Delta variant for the no-vaccination, one-dose, and two-dose groups decreased by 3.3, 1.9, and 2.3 folds relative to the wild-type virus, respectively, and those against the Omicron variant decreased by 7.0, 4.0, and 3.8 folds, respectively. Similarly, the responses of SARS-CoV-2 RBD-specific B cells and memory B cells were boosted by the second vaccine dose. Results showed that the convalescents benefited from the administration of the inactivated vaccine (one or two doses), which enhanced neutralization against highly mutated SARS-CoV-2 variants and memory B cell responses. Two doses of inactivated vaccine among COVID-19 convalescents are therefore recommended for the prevention of the COVID-19 pandemic, and vaccination guidelines and policies need to be updated.