medwireNews: Findings from a real-world investigation suggest that obesity does not influence the effectiveness of cell-targeted therapies in patients with rheumatoid arthritis (RA), but it does negatively impact the effectiveness of cytokine-targeted therapies.
Martin Schäfer (German Rheumatism Research Centre, Berlin) and study co-authors analyzed data on 10,593 individuals from the German RABBIT registry who received treatment for RA with one of five agents or drug groups: rituximab; abatacept; tocilizumab; conventional DMARDs; or tumor necrosis factor (TNF) inhibitors, for 6 months. A total of 2909 patients were obese (BMI≥30 kg/mg2).
Obesity was not significantly associated with improvement in DAS28-ESR scores among the 153 people who took rituximab, or the 144 who took abatacept, with the improvement only a nonsignificant 0.13–0.18 and 0.22–0.23 points below that for the 504 and 378 non-obese patients receiving the same respective therapies.
On the other hand, when treated with tocilizumab, there was significantly less improvement in DAS28-ESR scores among obese females and males than among their non-obese peers, by a respective 0.22 and 0.41 points.
The researchers note in Rheumatology that among those treated with tocilizumab, obesity was associated with joint pain, as well as with joint swelling in women and a weaker erythrocyte sedimentation rate (ESR) response in men.
Previous studies regarding the effect of obesity on tocilizumab in patients with RA were labelled “ambiguous” by the authors, who postulate: “This may be due to previous studies not assessing the effect of obesity in a sex-specific manner and, in some cases, to a potential lack of power resulting from small sample sizes.”
The team also found that in women, but not men, obesity was significantly associated with a poorer improvement in DAS28-ESR score with conventional DMARD and TNF-inhibitor treatment, with the improvement in scores 0.15 and 0.22 points lower than that for non-obese women who received the same respective treatments.
The weaker response to conventional DMARDs among obese versus non-obese women was mainly associated with ESR and inflammation response, while the weaker response to TNF inhibitors was associated with joint pain and a worse patient global health assessment.
Given that the impact of obesity on cytokine-targeted treatment had “a statistically significant effect in considerably more outcomes and therapies for woman than for men,” whereas there was no effect for cell-targeted therapies, the team suggests that rituximab and abatacept “might thus be particularly worthwhile treatment options for obese women.”
They note, however, that the group sizes were bigger for women (n=7845) than for men (2748) and for those receiving cytokine-targeted therapies (n=1173–4848) compared with rituximab (n=648) and abatacept (n=531), meaning the power to detect obesity effects in these groups was greater.
Overall, the DAS28-ESR response outcomes associated with obesity were echoed for other measures, including CDAI, SDAI, and good EULAR response.
By Hannah Kitt
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Rheumatology 2019; doi:10.1093/rheumatology/kez535