Azathioprine (AZA) is widely used in inflammatory bowel disease (IBD), but inter-individual variability in efficacy and toxicity limits its optimal use. Genetic variants affecting thiopurine metabolism, particularly in TPMT and MTHFR, may contribute to these differences. This study assessed the influence of TPMT G460A (rs1800460) and MTHFR C677T (rs1801133) polymorphisms, along with non-genetic factors, on AZA outcomes in Tunisian IBD patients.

A retrospective cohort of 62 IBD patients treated with AZA for ≥3 months was analyzed. Clinical and demographic data were collected from standardized records. Genotyping of TPMT G460A and MTHFR C677T was performed by PCR-RFLP. Associations with AZA efficacy and toxicity were evaluated using chi-square or Fisher’s exact tests and multivariate logistic regression for variables with p < 0.1. Statistical significance was set at p < 0.05.

The TPMT G460A variant was identified in one patient only, limiting analysis; subsequent evaluation focused on the MTHFR C677T polymorphism (CC 45.2%, CT 40.3%, TT 14.5%). No significant association was found between C677T genotype and AZA efficacy (p = 0.47) or toxicity (p = 0.61). Non-genetic factors—including age, sex, BMI, smoking status, disease subtype, corticosteroid response, and concomitant treatments—were also not associated with outcomes. Multivariate regression identified no independent predictors of AZA response or adverse effects. These findings likely reflect both the low prevalence of TPMT variants in this population and the absence of additional thiopurine-metabolizing gene variants (e.g., TPMT2, TPMT3A, NUDT15) in the analysis.

While no significant determinants of AZA efficacy or toxicity were identified, this study highlights the low frequency of common TPMT variants in Tunisian IBD patients and underscores the need for broader pharmacogenetic screening. These results provide a basis for larger, multi-gene studies to optimize individualized thiopurine therapy in North African populations.