To test whether the G-to-A polymorphism at position −308 in the promoter of the tumor necrosis factor α (TNFα) gene influences response to infliximab therapy in patients with rheumatoid arthritis (RA).
We genotyped 59 RA patients by polymerase chain reaction and subdivided them into two groups: those with the A/A or A/G genotype and those with the G/G genotype. We compared the groups' clinical responses to infliximab treatment after 22 weeks, using the Disease Activity Score in 28 joints (DAS28).
We found that 42% of patients in the A/A and A/G group and 81% of patients in the G/G group had improvement of at least 1.2 in the DAS28 score (P = 0.0086). The average improvement in the DAS28 score was 1.24 in the A/A and A/G patients and 2.29 in the G/G patients (P = 0.029).
These data suggest that patients with a TNFα −308G/G genotype are better infliximab responders than are patients with A/A or A/G genotypes. TNFα −308 genotyping may be a useful tool for predicting response to infliximab treatment.