Plasma trough levels of mycophenolic acid do not correlate with efficacy and safety of mycophenolate mofetil in psoriasis.

Background: Mycophenolate mofetil (MMF) has been shown to be effective for systemic treatment of psoriasis. MMF is the prodrug of mycophenolic acid (MPA), the pharmacologically active compound. The measurement of plasma MPA levels could be useful for optimizing therapeutic management using MMF.
Objectives: To investigate whether plasma trough levels of MPA correlate with the efficacy and safety of oral MMF in the treatment of patients with psoriasis.
Methods: Six patients (four women and two men, mean age 58 years) with severe chronic plaque-type psoriasis were treated with oral MMF 1 g twice daily. The Psoriasis Area and Severity Index (PASI), routine laboratory examinations and plasma MPA trough levels, measured by an enzyme-multiplied immunoassay (EMIT), were determined at 2 weeks and 1, 3, 5 and 7 months.
Results: All the patients experienced a marked improvement within the first 15 days and continued to do so for 5-7 months. Two patients achieved complete remission. MMF was well tolerated. MPA levels showed a wide intra- and interindividual variability. There was no significant correlation between MPA trough levels and the reduction of the PASI or the presence of adverse effects, but a good correlation with therapeutic compliance.
Conclusions: The monitoring of MPA trough levels with EMIT appears to be a poor predictor of efficacy or toxicity. In contrast, it is a useful tool to evaluate the degree of therapeutic compliance.