Comparison of long-term clinical outcome with etanercept treatment and adalimumab treatment of rheumatoid arthritis with respect to immunogenicity.

OBJECTIVE: To compare rates of sustained low and minimal disease activity and remission according to the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria during 3-year followup in rheumatoid arthritis (RA) patients treated with etanercept and adalimumab in routine care.
METHODS: Four hundred seven RA patients previously unexposed to tumor necrosis factor antagonists were treated with etanercept (n = 203) or adalimumab (n = 204) and assessed at 3- and later 6-month intervals. Treatment allocation was at the discretion of the treating rheumatologist. Clinical parameters were measured at each time point, as were anti-adalimumab antibodies in adalimumab-treated patients. Achievement of clinical outcome was defined as the occurrence of sustained (at least 12 consecutive months) low disease activity (28-joint Disease Activity Score [DAS28] <3.2), minimal disease activity (DAS28 <2.6), or ACR/EULAR remission based on the Simplified Disease Activity Index (SDAI). Non-overlapping response rates were calculated.
RESULTS: Among the adalimumab group, 13% reached sustained low disease activity but not sustained minimal disease activity, 15% reached sustained minimal disease activity but not sustained remission according to the SDAI, and 16% reached sustained ACR/EULAR remission. In the etanercept group the corresponding rates were 16%, 11%, and 12%, respectively (P = 0.42, overall test for linear trend). Adalimumab-treated patients without anti-adalimumab antibodies (n = 150 [74%]) had the best outcomes, and adalimumab-treated patients with anti-adalimumab antibodies the worst, with outcomes in etanercept-treated patients in between (P < 0.0001). Differences were most apparent in the sustained SDAI remission and sustained minimal disease activity categories. For example, 40% of anti-adalimumab antibody-negative patients, 23% of etanercept-treated patients, and 4% of anti-adalimumab antibody-positive patients achieved at least sustained minimal disease activity.
CONCLUSION: Overall, etanercept and adalimumab treatment appear similar in inducing a good long-term clinical outcome. However, in the case of adalimumab this is strongly dependent on the presence or absence of anti-adalimumab antibodies.