Conference scene: lessons from animal models of autoimmune diseases: from mechanisms to applications

The Association Between Azathioprine Genetic Polymorphisms, Clinical Efficacy and Adverse Drug Reactions Among Egyptian Patients with Autoimmune Diseases

Purpose

The study aimed to detect the frequencies of allelic variants (TPMT*3A, TPMT*3C, and TPMT*3G) in the TPMT genes in the Egyptian population and assess the association between TPMT polymorphisms and azathioprine (AZA)—clinical efficacy and adverse drug reactions among Egyptian patients with autoimmune diseases.

Patients and Methods

Design

A prospective, observational single-center clinical trial.

Setting

Rheumatology and Rehabilitation Department, Kasr Alainy University Hospital, Faculty of Medicine, Cairo University.

Patients

Patients attending Kasr Alainy Rheumatology Outpatient Clinic between December 1, 2017 and June 30, 2019 were included in the study after signing a consent form. TPMT genetic polymorphisms were detected for all patients, and the association between polymorphisms presence and azathioprine’s clinical efficacy and adverse drug reactions were determined.

Results

A total of 150 patients with a mean age of 35.85 years were enrolled in this study. About 72% of patients were heterozygous in the TPMT*3 G460A and TPMT*3 A719G mutant alleles and 81% were wild type in the TPMT*2 G238C mutant allele. Abnormal liver function tests were detected in 42% of patients. Myelosuppression was presented as anemia which was detected in 63% of patients, leucopenia in 51%, and thrombocytopenia in 25% of patients. AZA clinical failure has occurred in 50% of patients where AZA was discontinued or shifted to another drug which occurred in 45% of patients. Myelosuppression rates were higher in homozygous patients in the three mutant alleles, but statistically significant in TPMT*2 G238C while not statistically significant in TPMT*3 G460A and TPMT*3 A719G. Females had a higher risk of immunosuppression than males (p-value 0.031).

Conclusion

The study provided an overview of the genomic variations in the Egyptian population. Routine TPMT genotyping prior to the initiation of AZA therapy should be considered.

Association between Thiopurine S-Methyltransferase Polymorphisms and Azathioprine-Induced Adverse Drug Reactions in Patients with Autoimmune Diseases: A Meta-Analysis

Purpose

Azathioprine (AZA) is widely used as an immunosuppressive drug in autoimmune diseases, but its use is limited by significant adverse drug reactions (ADRs). Thiopurine S-methyltransferase (TPMT) is an important enzyme involved in AZA metabolism. Several clinical guidelines recommend determining TPMT genotype or phenotype before initiating AZA therapy. Although several studies have investigated the association between TPMT polymorphisms and AZA-induced ADRs, the results are inconsistent. The purpose of this study is to evaluate whether there is an association between TPMT polymorphisms and AZA-induced ADRs using meta-analysis.

Methods

We explored PubMed, Web of Science and Embase for articles on TPMT polymorphisms and AZA-induced ADRs. Studies that compared TPMT polymorphisms with-ADRs and without-ADRs in patients with autoimmune diseases were included. Relevant outcome data from all the included articles were extracted and the pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated using Revman 5.3 software.

Results

Eleven published studies, with a total of 651 patients with autoimmune diseases, investigated associations between TPMT polymorphisms and AZA-induced ADRs, were included in this meta-analysis. Our meta-analysis demonstrated that TPMT polymorphisms were significantly associated with AZA-induced overall ADRs, bone marrow toxicity and gastric intolerance; pooled ORs were 3.12 (1.48–6.56), 3.76 (1.97–7.17) and 6.43 (2.04–20.25), respectively. TPMT polymorphisms were not associated with the development of hepatotoxicity; the corresponding pooled OR was 2.86 (95%CI: 0.32–25.86). However, the association in GI subset could be driven by one single study. After this study was excluded, the OR was 2.11 (95%CI: 0.36–12.42); namely, the association became negative.

Conclusions

Our meta-analysis demonstrated an association of TPMT polymorphisms with overall AZA-induced ADRs, bone marrow toxicity and gastric intolerance, but not with hepatotoxicity. The presence of the normal TPMT genotypes cannot preclude the development of ADRs during AZA treatment, TPMT genotyping prior to commencing AZA therapy cannot replace, may augment, the current practice of regular monitoring of the white blood cell. Because of small sample sizes, large and extensive exploration was required to validate our findings.