medwireNews: Disease activity does not change following the switch from etanercept to the biosimilar formulation SB4, and treatment retention rates may be determined by patient-specific factors, suggests an analysis of the DANBIO registry.
“In Denmark, a nationwide guideline of mandatory switch from 50 mg originator [etanercept] to biosimilar (SB4) etanercept was issued for patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) and axial spondyloarthritis [axSpA] in 2016,” explain Bente Glintborg (Rigshospitalet, Glostrup, Denmark) and colleagues.
In their real-world study, the researchers demonstrated that 79% of 2061 etanercept-treated patients – including 77% of 1219 patients with RA, 86% of 407 with PsA, and 77% of 435 with axSpA – switched to SB4 between 2016 and 2017.
They report in the Annals of the Rheumatic Diseases that there were “no clinically relevant differences” in disease activity following the switch to SB4. Median DAS28 score was a comparable 1.9 points 3 months before the switch and 2.1 points after the switch in RA patients, and 1.8 and 2.1 points, respectively, among those with PsA. Similarly, median BASDAI score was a corresponding 33 and 31 points at the two timepoints in patients with axSpA.
Treatment retention rates were higher among patients who switched to the biosimilar than those who remained on originator etanercept, at 83% versus 77%. The most common reason for treatment withdrawal among switchers and non-switchers was lack of effect (46% and 34%, respectively), followed by adverse events (26% and 10%, respectively).
Glintborg and colleagues note that “adverse events were mainly unspecific,” including headache, nausea, rash/itching, and diarrhea, and that “no major safety signals were observed.”
The researchers also observed an association between disease activity and retention rates. Among patients who switched to SB4, those who were not in remission at the time of switching were 70% more likely to discontinue treatment than those who were in remission. Similarly, patients who remained on etanercept originator were more than twice as likely to discontinue treatment if they were not in remission.
These findings “suggest that switch outcomes in routine care are affected by patient-related factors and non-specific drug effects,” conclude the study authors.
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