THE EFFECT OF GSTA1, CYP2C19, AND CYP2B6 POLYMORPHISM ON CYCLOPHOSPHAMIDE EFFECTIVITY AND SIDE EFFECT IN LUPUS NEPHRITIS PATIENT

• Main Author: Yen Ari Indrawijaya, Yen
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87491
• Institution: Institut Teknologi Bandung

Systemic Lupus Erythematosus (SLE) is a chronic multisystem autoimmune disease that predominantly effects women of reproductive age, with renal involvement in the majority of cases. Approximately 95% of SLE patients experience lupus nephritis (LN) as a complication, which carries a high risk of renal failure and represents a major factor contributing to morbidity and mortality. Cyclophosphamide (CYC) is the primary therapeutic choice for severe LN, although its efficacy varies based on genetic factors and patient ethnicity. Therefore, strategies to improve LN treatment management through the implementation of pharmacogenetics for precision medicine are crucial. Cyclophosphamide is a prodrug that requires cytochrome P450 (CYP450) for activation and glutathione S-transferase (GST) for deactivation. Pharmacogenetic studies of CYC have highlighted the role of polymorphisms in CYP2B6 and CYP2C19, though results are inconsistent between Japan and the United States. Additionally, the influence of GSTA1 polymorphisms varies according to promotor variant positions in Egypt and China. However, the diplotype effects of GSTA1, CYP2C19, and CYP2B6 polymorphisms have not been previously reported. This study aims to analyze the impact of GSTA1, CYP2C19, and CYP2B6 polymorphisms, both individually and in combination, on the effectivity and side effects of CYC in LN patients and to provide recommendations for precision medicine. This study began with an exploration of genetic variants effecting CYC metabolism, which were subsequently used as biomarker polymorphisms. Identification of the optimal genotyping method using PCR-Sanger sequencing. One hundred adult lupus nephritis (LN) patients who received six intravenous doses of CYC according to the National Institute of Health (NIH) or European Alliance of Associations for Rheumatology (EULAR) protocols, were included in the study. Effectivity and side effects of CYC were evaluated based on laboratory results and patient medical records from 2012 to 2023, following a retrospective case-control study design. Ten single nucleotide polymorphisms (SNPs) from GSTA1, CYP2C19, and CYP2B6 were successfully detected. Five SNP combinations were identified, including GSTA1 (-52, -69), GSTA1 (-52, -69, -513), GSTA1 (-52, -69, -567), CYP2C19 (c.681, c.819+228), and CYP2B6 (-2320, -1778, -750). The effect of genetic polymorphisms on CYC effectivity and side effects was analyzed statistically using multiple binary logistic regression based on odd ratio (OR), with accuracy determined by sensitivity and specificity percentages from the receiver operating characteristic (ROC) curve. CYC effectivity was determined by improvements in renal function and disease activity, as measured by the Modified- Systemic Lupus Erythematosus Disease Activity Index 2000 (M-SLEDAI-2K). Following CYC therapy, significant improvements were observed in creatinine clearance (98.50 vs. 109.50 mL/min), proteinuria (3.00 vs. 1.50), serum creatinine (0.79 vs. 0.69 mg/dL), and M-SLEDAI-2K scores (8.61 vs. 6.95, p<0.05). Remission rates were categorized as 30% complete remission (CR), 49% partial remission (PR), and 21% non-remission (NR), with 40% of patients categorized low disease activity while 60% of patients with high disease activity. Patients with LN without hypertension, aged 18-20 years, who were treated using the NIH protocol, achieved remission and improvement in disease activity. The covariates of hypertension, protocol type, and age significantly influenced the efficacy of cyclophosphamide (CYC) (p<0.05). Side effects, including alopecia (64%), amenorrhea (53.84%), gastrointestinal disturbances (18%), and leukopenia (13%), were documented. The analysis of GSTA1, CYP2C19, and CYP2B6 polymorphisms revealed significant effect on CYC effectivity and side effects in LN patients. Genetic polymorphisms revealed significant effect to high disease activity (OR<1) for GSTA1 (-52 AG), (-513 AG), (-567 GT+GG), CYP2B6 (-750 TC+CC), and (-1778 AA+AG). Polymorphisms in CYP2C19 (c.681 GA+AA), (c.819+228 AG+AA), and CYP2B6 (-750 TC+CC) were significantly effect to reduce of achieving remission (PR+CR) (OR<1), while GSTA1 (-567 GT+GG) and CYP2B6 (-750 TC+CC) significantly inhibited complete remission (CR) (OR<1). Based on these findings, patients with genetic polymorphisms that reduce CYC effectiveness may benefit from alternative immunosuppressive therapy, such as mycophenolate mofetil (MMF)/ cyclosporine/ tacrolimus (CNI). Conversely, patients with genotypes GSTA1 (-52 AA), (-513 AA), (-567 TT), CYP2C19 (c.681 GG), (c.819+228 AA), CYP2B6 (-1778 GG), and (-750 TT) are recommended to use CYC as first-line therapy. Polymorphisms in CYP2C19 (c.681 GA+AA) and (c.819+228 AG+AA) were found to significantly reduce the risk of alopecia (OR<1), while CYP2B6 (-2320 TC+CC) significantly increased the risk of gastrointestinal disorders (OR>1). No significant interactions were observed between SNP combinations and CYC effectivity or side effects. Overall, the pharmacogenetic analysis of GSTA1, CYP2C19, and CYP2B6 provides valuable insights into predicting CYC treatment outcomes and side effects in LN patients. Pharmacogenetic testing for these polymorphisms is recommended before initiating CYC therapy to implement precision medicine.