Mycophenolic Acid Exposure Determines Antibody Formation Following <scp>SARS‐CoV</scp> ‐2 Vaccination in Kidney Transplant Recipients: A Nested Cohort Study

Despite (repeated) boosting, kidney transplant recipients (KTRs) may remain at increased risk of severe COVID-19 since a substantial number of individuals remain seronegative or with low antibody titers. In particular, mycophenolic acid use has been shown to affect antibody formation negatively and may be an important modifiable risk factor. We investigated the exposure–response relationship between mycophenolic acid 12-hour area under the curve (AUC 0–12h) exposure and seroconversion including antibody titers after vaccination using mRNA-1273 SARS-CoV-2 vaccine (Moderna) in 316 KTRs from our center that participated in the national Dutch renal patients COVID-19 vaccination – long term efficacy and safety of SARS-CoV-2 vaccination in kidney disease patients vaccination study. After two vaccination doses, 162 (51%) KTRs seroconverted. KTRs treated with mycophenolic acid showed less seroconversion and lower antibody titers compared with KTRs without mycophenolic acid (44% vs. 77%, and 36 binding antibody units (BAU)/mL vs. 340 BAU/mL; P < 0.001). The mean mycophenolic acid AUC 0–12h exposure was significantly lower in KTRs who seroconverted compared with KTRs who did not (39 vs. 29 mg⋅h/L; P < 0.001). High mycophenolic acid exposure (±90 mg⋅h/L) and no exposure to mycophenolic acid resulted in a seroconversion rate ranging from 10% to 80%. Every 10 mg⋅h/L increase in mycophenolic acid AUC 0–12h gave an adjusted odds ratio for seroconversion of 0.87 (95% confidence interval (CI), 0.79–0.97; P = 0.010) and 0.89 (95% CI, 0.85–0.93; P < 0.001) for KTRs on dual and triple maintenance immunosuppressive therapy, respectively. Higher mycophenolic acid AUC 0–12h correlated with lower antibody titers (R = 0.44, P < 0.001). This study demonstrates the exposure–response relationship between gold standard mycophenolic acid exposure and antibody formation to support interventional studies investigating mycophenolic acid adjustment to improve antibody formation after further boosting.