The best b/tsDMARD treatment retention rates have been observed in psoriatic arthritis (PsA) patients, according to an Adelaide study.

Comprising 230 adult patients with RA, PsA, and AS commencing first and subsequent b/tsDMARDs between 2008 and 2018, the study, published in Frontiers in Medicine, found the most common initial b/tsDMARD was a TNFi, prescribed in 74%, 96%, and 100% of RA, PSA, and AS patients, respectively.

Overall treatment retention rates at five years of follow-up were 47% for RA, 70% for PsA and 53% for AS.

The overall median treatment duration before failure was 4.0, 8.2, and 6.2 years, respectively.

“When compared to RA patients, the risk of b/tsDMARD failure was halved in PsA patients (HR = 0.50), but no different in AS patients (HR = 1.0),” the study authors from the Rheumatology Unit, Flinders Medical Centre, said.

The investigators said the higher retention rates in PsA compared to RA may be related to the earlier achievement of remission and possibly milder disease in PsA.

“Contrary to expectations, none of the additional covariates (age, gender, disease duration, smoking status and the use of concomitant csDMARDS) were associated with the risk of b/tsDMARD failure,” they noted.

“Further, in an analysis restricted to RA patients, there was no relationship between seropositivity and b/tsDMARD failure (HR 0.89, 95% CI 0.53, 1.50, p = 0.66).”

The study found 64% of RA patients who failed a TNFi were switched to a non-TNFi b/tsDMARD – predominantly tocilizumab.

“As expected, the majority of b/tsDMARD switching in both PsA and AS patients was within TNFi. In PsA, 3/16 patients who switched treatment switched from TNFi to secukinumab, and a further two switched to ustekinumab. In AS, 3/21 patients who switched treatment switched from TNFi to secukinumab.”

“The most frequent reasons for b/tsDMARD failure/switching were secondary failure (n = 62), primary failure (n = 35) and side effects (n = 24).”

The study authors said observed retention rates for first b/ts DMARDs were largely consistent with other studies.

“Retention rates of second and third b/tsDMARDs are more difficult to compare with our current study, as there are few studies that have analysed similar data.”

“Despite greater availability of b/tsDMARDs with differing mechanisms of action, retention rates of the first b/tsDMARD remain similar to previous years,” they said.