medwireNews: Patients with early moderate-to-severe rheumatoid arthritis (RA) who test positive for HLA-DRB1 shared epitope alleles may benefit more from abatacept than adalimumab, an analysis of head-to-head data indicates.
The phase IV trial – early AMPLE – involved 80 biologic-naïve RA patients, with a disease duration of 12 months or less, who were seropositive for anti-cyclic citrullinated protein-2 antibodies and had active disease despite taking weekly doses of methotrexate. These patients were randomly assigned to receive subcutaneous abatacept 125 mg/week or subcutaneous adalimumab 40 mg every 2 weeks, while continuing on weekly methotrexate.
After 24 weeks of treatment, the proportion of patients achieving ACR20, 50, and 70 responses was numerically higher with abatacept than adalimumab, at 83% versus 63%, 70% versus 45%, and 48% versus 30%, respectively, giving estimated differences of 20%, 25%, and 18% in favor of abatacept.
Researcher Vivian Bykerk (Hospital for Special Surgery, New York, USA) pointed out: “The results we saw appeared to be driven by the [HLA-DRB1] shared epitope.”
In all, 61 patients tested positive for this shared epitope based on the presence of least one of the following alleles: *01:01, *01:02, *04:01, *04:04, *04:05, *04:08, *04:10, *10:01, *14:02, or *14:06.
And among the 30 taking abatacept, 87% achieved an ACR20 response. This compared with 58% of 31 patients taking adalimumab, giving a significant estimated difference of 28.6% in favor of abatacept, reported Bykerk. The corresponding rates for ACR50 and ACR70 response were 77% versus 45% and 57% versus 29%, with significant estimated differences of 31.5% and 27.6%, respectively.
The proportion of shared epitope-positive patients achieving DAS28-CRP remission (<2.6 points) was also greater among those taking abatacept, at 50%, compared with 23% of those taking adalimumab, giving a significant estimated difference of 27%.
Bykerk commented that “there were no new safety signals” identified during the study and the treatment-related adverse event rate was similar, at 30% for the abatacept group and 28% for the adalimumab group.
There was one treatment-related serious adverse varicella infection reported with adalimumab, but no treatment-related serious events with abatacept.
Bykerk concluded that there may be “a differential benefit by treating patients with the shared epitope and early RA with abatacept compared with adalimumab.”
She added that, of note, “they saw higher abatacept titers in this shared epitope group and this requires further observation and understanding.”
By Lucy Piper
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