BACKGROUND: Glutathione S-transferases (GSTs) are involved in detoxification of xenobiotics such as fumaric acid esters (FAE). OBJECTIVES: To perform GSTT1 geno- and phenotyping in psoriasis patients treated with FAE to find out whether the responder status and/or occurrence of side-effects are associated with allelic variants and enzymatic activity of GSTT1. METHODS: We treated 106 psoriasis patients with FAE. GSTT1 genotyping was performed using PCR, phenotyping was carried out by means of a validated high performance liquid chromatography assay at baseline and under treatment. RESULTS: The distribution of GSTT1 genotypes was as follows: 31% *A/*A; 49% *A/*0; 20% *0/*0. GSTT1 phenotypes as expressed in enzyme activity significantly differed between conjugators classes. (P < 0.001). GSTT1 activity under treatment was significantly (P = 0.0001) increased when compared with baseline. There were no significant associations between the aforementioned GSTT1 pheno- and genotypes and clinical parameters such as psoriasis area and severity index (PASI)50, adverse effects and FAE dosage (P > 0.05), except for the frequent occurrence of reduction (>50%) of circulating lymphocytes in patients with *0/*0 GSTT1 status (P = 0.036; odds ratio: 6, 95% CI: 1.1-32). CONCLUSION: GSTT1 geno- and phenotypes significantly correlate in psoriasis patients and do not substantially differ from healthy controls. Response to FAE does likely not depend on GSTT1. However, *0/*0 GSTT1 status is a predictor for the occurrence of marked reduction of lymphocyte counts under FAE therapy. Notably, FAE seem to enhance GSTT1 enzyme activity in high and low conjugators.
BACKGROUND: Glutathione S-transferases (GSTs) are involved in detoxification of xenobiotics such as fumaric acid esters (FAE). OBJECTIVES: To perform GSTT1 geno- and phenotyping in psoriasispatients treated with FAE to find out whether the responder status and/or occurrence of side-effects are associated with allelic variants and enzymatic activity of GSTT1. METHODS: We treated 106 psoriasispatients with FAE. GSTT1 genotyping was performed using PCR, phenotyping was carried out by means of a validated high performance liquid chromatography assay at baseline and under treatment. RESULTS: The distribution of GSTT1 genotypes was as follows: 31% *A/*A; 49% *A/*0; 20% *0/*0. GSTT1 phenotypes as expressed in enzyme activity significantly differed between conjugators classes. (P < 0.001). GSTT1 activity under treatment was significantly (P = 0.0001) increased when compared with baseline. There were no significant associations between the aforementioned GSTT1 pheno- and genotypes and clinical parameters such as psoriasis area and severity index (PASI)50, adverse effects and FAE dosage (P > 0.05), except for the frequent occurrence of reduction (>50%) of circulating lymphocytes in patients with *0/*0 GSTT1 status (P = 0.036; odds ratio: 6, 95% CI: 1.1-32). CONCLUSION:GSTT1 geno- and phenotypes significantly correlate in psoriasispatients and do not substantially differ from healthy controls. Response to FAE does likely not depend on GSTT1. However, *0/*0 GSTT1 status is a predictor for the occurrence of marked reduction of lymphocyte counts under FAE therapy. Notably, FAE seem to enhance GSTT1 enzyme activity in high and low conjugators.