Patients with rheumatoid arthritis (RA) with an inadequate response to adalimumab are less likely to benefit from etanercept compared with biologic-naïve patients, according to study results published in the Scandinavian Journal of Rheumatology.

The results indicated that these results only applied to patients with adalimumab concentrations ≥0.5 μg/mL. Patients with <0.5 μg/mL had similar etanercept response compared with biologic-naïve patients.

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The study included participants with RA starting etanercept treatment in the Reade Rheumatology Registry (n=449). In participants previously on adalimumab, the researchers determined serum concentrations before discontinuing treatment. They categorized the participants into 3 subgroups based on serum adalimumab concentration: <0.5 μg/mL, 0.5-5.0 μg/mL, and ≥5.0 μg/mL.

The investigators compared the European League Against Rheumatism (EULAR) good/moderate response rate after 52 weeks of etanercept of the switcher subgroups with biologic-naïve participants.

Of 449 participants, 15% (n=69) switched from adalimumab and 85% (n=380) were biologic-naïve.

Of the biologic-naïve participants, 74% achieved a EULAR good or moderate response. In the switcher subgroups, a EULAR good or moderate response was achieved by 72% of patients in the <0.5 μg/mL group, 50% in the 0.5 to 5.0 μg/mL group, and 52% in the ≥5.0 μg/mL group (P =.15).

The researchers found that participants with an adalimumab concentration ≥0.5 μg/mL were significantly less likely to achieve a EULAR good or moderate response on etanercept compared with biologic-naïve participants. There was no significant difference between participants with an adalimumab concentration <0.5 μg/mL and biologic-naïve participants in the likelihood of achieving a good or moderate EULAR response.

“To our knowledge, this is the first study showing that patients with sufficient drug exposure respond less often to a second [tumor necrosis factor inhibitor],” the researchers wrote.

Reference l’ Ami MJ, Ruwaard J, Krieckaert CLM, et al. Serum drug concentrations to optimize switching from adalimumab to etanercept in rheumatoid arthritis [published online April 23, 2019]. Scand J Rheumatol. doi:10.1080/03009742.2019.1577915