Reducing the dose of tumor necrosis factor inhibitors by approximately one-third did not increase disease activity in adults with psoriatic arthritis (PsA) or axial spondyloarthritis (axSpA) in a stable low–disease activity state, according to findings from two parallel controlled retrospective cohort studies.
Disease activity–guided dose optimization (DAGDO) can reduce drug exposure in patients with PsA or axSpA who have low disease activity, but its impact on increased disease activity has not been as well studied as full-dose continuation, Celia A.J. Michielsens, MD, of Sint Maartenskliniek, Nijmegen, the Netherlands, and colleagues wrote.
“DAGDO or discontinuation of bDMARDs [biologic disease-modifying antirheumatic drugs] as a standard of care in adults with stable axSpA is currently discouraged by” the American College of Rheumatology, the researchers said. However, guidelines from the European Alliance of Associations for Rheumatology allow for the slow tapering of bDMARDs in patients with sustained remission.
In a controlled, retrospective cohort study published in Rheumatology, the researchers analyzed data from their outpatient clinic, which initiated a specific TNF inhibitor DAGDO protocol in 2010 for patients with RA, PsA, and axSpA. Disease activity was measured using the Disease Activity Score in 28 joints with C-reactive protein (DAS28-CRP) for patients with PsA and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) for patients with axSpA.
The study population included 153 patients with PsA who had a mean DAS28-CRP of 6.5 and 171 with axSpA who had a similar mean number of disease activity measurements (6.5 with DAS28-CRP and 6.4 with BASDAI). Median follow-up time was several months short of 4 years in each group. Treatment was divided into three periods: continuation of full TNF inhibitor dose, TNF inhibitor DAGDO, and a period with stable TNF inhibitor dose after DAGDO.
Overall, no significant differences appeared in mean DAS28-CRP and BASDAI over the course of the study between the period of the full TNF inhibitor dose continuation and both the TNF inhibitor DAGDO period and the stable TNF inhibitor dose period. Among PsA patients, the mean DAS28-CRP was 1.94 for the full-dose period, 2.0 in the TNF inhibitor DAGDO period, and 1.97 in the stable TNF inhibitor dose after DAGDO period. For axSpA patients, the mean BASDAI was 3.44, 3.47, and 3.48, respectively, for the three periods. Older age, longer disease duration, and longer follow-up were significantly associated with higher DAS28-CRP scores in patients with PsA, and older age and female gender were significantly associated with higher BASDAI scores in patients with axSpA.
The mean percentage of daily defined dose (%DDD) for patients with PsA was 108% during the full dose period, 62% in the TNF inhibitor DAGDO period, and 78% with stable TNF inhibitor after DAGDO, and nearly the same for patients with axSPA at 108%, 62%, and 72%, respectively.
The %DDD represents “a modest degree of tapering,” compared with studies in RA patients, the researchers noted. “Explanations for this difference could be that the full dose-reduction potential was not met due to suboptimal execution of the local protocol, whereas in prospective intervention trials, protocol adherence is likely higher.”
The study findings were limited by several factors including the open-label design and potential for nocebo effects, possible incorrect attribution, and information bias, as well as the use of DAS28-CRP and BASDAI rather than more modern measurement tools, the researchers noted.
However, the results were strengthened by the large sample size and real-world clinical setting, frequent assessment of disease activity, long-term follow-up, and the performance of DAGDO by rheumatologists familiar with the measuring tools, they said. The results suggest that DAGDO is safe and effective for patients with low disease activity in either condition, but randomized, prospective studies can provide more definitive evidence.
The study received no outside funding. One author disclosed relationships with multiple pharmaceutical companies.