Data are not definitive
Both antiadalimumab (Humira) antibodies and adalimumab serum levels fell short on predicting drug responses in rheumatoid arthritis patients who failed initial adalimumab therapy, based on a retrospective cohort study of 137 adults.
Biologic disease-modifying antirheumatic drugs (bDMARDs), notably adalimumab, are often prescribed for RA, but “approximately 41% of RA patients do not achieve good response after 6 months of treatment with adalimumab,” wrote Evy Ulijn of Sint Maartenskliniek, Nijmegen, the Netherlands, and colleagues. Preliminary studies have suggested that antiadalimumab antibodies (antidrug antibodies, ADA) and adalimumab serum levels (ADL) may predict the response to a second bDMARD in patients who fail initial adalimumab treatment, they said.
In a study published in Annals of the Rheumatic Diseases, the researchers examined data from 137 adult RA patients seen at the clinic during Jan. 2012–Jan. 2018 who failed to respond to adalimumab after at least 3 months of treatment and started another bDMARD. The average age of the patients was 64 years, and approximately 69% were women.
Overall, the presence of ADA was not a significant predictor of a European League Against Rheumatism good response in patients who switched to another TNFi (etanercept, golimumab, infliximab, or certolizumab pegol), with sensitivity of 18% and specificity of 75%. ADA also was not predictive of response to a non-TNFi bDMARD (rituximab, tocilizumab, or abatacept), with sensitivity and specificity of 33% and 70%, respectively.
Similarly, ADL levels in patients who switched to a TNFi or non-TNFi were not significant predictors of treatment response, with sensitivities and specificities of 50% and 52%, respectively, for TNFi and 32% and 69%, respectively, for non-TNFi.
The findings that neither ADA nor ADL showed predictive values contrast with previous studies, the researchers said.
“Not only did the results of this study show no predictive values, in some analyses a prediction is found in the opposite direction of what was expected,” they wrote.
The study findings were limited by several factors, including the random timing of sample collection, retrospective study design, and potential for misclassification of responders or nonresponders, the researchers noted.
However, the results were strengthened by the blinded choice of treatment and outcome assessment, larger sample size than previous studies, and focus on adalimumab in particular, they said.
“While counterintuitive, it is hard to find an explanation for the lack of a positive finding,” they concluded.
More research is needed to confirm the predictive value of ADA and ADL, they said. In the meantime, rheumatologists should base decisions to switch patients to TNFi or non-TNFi treatment after adalimumab failure based on factors including side effects, local protocol, economical aspects, and patient preferences, they said.
The study received no external funding. The researchers had no financial conflicts to disclose.
SOURCE: Ulijn E et al. Ann Rheum Dis. 2020 Apr 21. doi: 10.1136/annrheumdis-2020-216996.