Polymorphisms in apoptosis genes predict response to infliximab therapy in luminal and fistulizing Crohn's disease

Background: Infliximab treatment is effective in 70-80% of patients with refractory luminal and fistulizing Crohn's disease. The effect of infliximab is ascribed to induction of apoptosis. Aim: To study whether polymorphisms in apoptosis genes predict the response to infliximab and whether they interact with clinical predictors. Methods: Cohort of 287 consecutive patients treated with infliximab for refractory luminal (n = 204) or fistulizing (n = 83) Crohn's disease was genotyped for 21 polymorphisms in apoptosis genes. Short-term clinical response was assessed at week 4 (luminal Crohn's disease) or 10 (fistulizing Crohn's disease) after the first infliximab infusion. Results: The response rate was 69% in luminal and 80% in fistulizing Crohn's disease. In luminal Crohn's disease, two genetic predictors were identified: (i) patients with the Fas ligand -843 CC/CT genotype (n = 135) responded in 75%, with the TT genotype (n = 21) in 38% only (P = 0.002; OR = 0.11; 95% CI: 0.08-0.56). (ii) Patients with the caspase-9 93 TT (n = 9) genotype all responded, in contrast with 67% (n = 147) with the CC and CT genotype (P = 0.04; OR = 1.50; 95% CI: 1.34-1.68). Concomitant azathioprine/mercaptopurine therapy overcame the effect of unfavourable genotypes. In the fistulizing Crohn's disease cohort, the same Fas ligand -843 CC/CT genotype was the only predictor of response (P = 0.002; OR = 1.66; 95% CI: 1.21-2.29), interacting with caspase-9 93 polymorphism but not with azathioprine/mercaptopurine. Conclusion: We observed that polymorphisms in FasL/Fas system and caspase-9 influence the response to infliximab in luminal and fistulizing Crohn's disease. The strongest association was seen between the Fas ligand -843 TT genotype and non-response. Concomitant mercaptopurine/azathioprine therapy, however, was able to overcome the effect of unfavourable genotypes in luminal disease.