Association between biologic exposure and relapse incidence in relapsing polychondritis: a retrospective cohort study

Relapsing polychondritis is characterized by recurrent flares, and comparative evidence for relapse prevention using biologics remains limited. We evaluated the association between biologic exposure and relapse incidence.

This single-centre retrospective cohort study (Kyoto University Hospital, 2000-23) investigated adults with relapsing polychondritis. Follow-up was divided into periods without biologics (No-Bio), with TNF-α inhibitors (TNFi) or with IL-6 receptor inhibitor (IL-6Ri). Primary outcomes were relapsing polychondritis relapse and hospitalized infection. Period-level incidence rate ratios (IRRs) were estimated using negative binomial regression with a log(person-time) offset and adjusted for prespecified covariates, and adjusted absolute event rates and rate differences were estimated by regression standardization.

Over 503.5 person-years, 55 patients were included (never-Bio, n = 28; ever-Bio, n = 27). Within the ever-Bio cohort, crude relapse rates were 46.9, 22.4 and 12.5 per 100 person-years during the No-Bio, TNFi and IL-6Ri periods, respectively. In adjusted models, both TNFi and IL-6Ri were associated with lower relapse rates than the No-Bio period (TNFi: IRR 0.4, 95% CI 0.2-0.8; adjusted rate difference, -54.0 events per 100 person-years, 95% CI -141.5 to -5.5; IL-6Ri: IRR 0.2, 95% CI 0.1-0.4; adjusted rate difference, -68.3 events per 100 person-years, 95% CI -149.8 to -21.4). Hospitalized infection estimates were imprecise (TNFi: IRR 0.3, 95% CI 0.1-1.4; IL-6Ri: IRR 0.7, 95% CI 0.2-2.6).

Biologic exposure was associated with lower relapse rates than during No-Bio periods in relapsing polychondritis, whereas estimates for hospitalized infection were imprecise.