Association of UGT1A9-2152C>T gene polymorphism with mycophenolic acid response in Indonesian patients with lupus nephritis

BACKGROUND: Mycophenolic acid (MPA) is a key immunosuppressant for lupus nephritis (LN), yet therapeutic response varies widely among individuals. Genetic variation in UGT1A9, particularly the -2152C>T promoter polymorphism, may influence MPA metabolism and exposure. Most existing pharmacogenomic studies have focused on solid organ transplant recipients, while evidence in autoimmune diseases, especially among Southeast Asian populations, remains limited. This study aimed to evaluate the association between the UGT1A9-2152C>T promoter polymorphism and MPA treatment response in Indonesian patients with LN. METHODS: A case-control study was conducted among 74 patients with LN receiving MPA therapy. Treatment response was classified as responders (n = 45) or non-responders (n = 29) based on the Systemic Lupus Erythematosus Disease Activity Responder Index-50 (SRI-50). Genotyping of the UGT1A9-2152C>T polymorphism was performed using polymerase chain reaction-restriction fragment length polymorphism. RESULTS: No significant differences in genotype frequencies or allele distribution were observed between responders and non-responders (P > 0.05). The T allele frequency was 11.5% and was not significantly associated with treatment response. CONCLUSION: UGT1A9-2152C>T showed no significant association with MPA response in Indonesian LN patients. These findings provide initial local pharmacogenomic evidence and underscore the need for larger multi-gene studies to support genotype-guided MPA therapy.