Effectiveness of biological targeted therapies may discriminate seronegative from seropositive rheumatoid arthritis.

OBJECTIVE: To assess the real-world effectiveness of targeting biologic drugs (bDMARD) in rheumatoid arthritis (RA) patients negative for rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA). METHODS: We retrospectively selected 81 seronegative and 404 seropositive RA patients receiving treatment with abatacept, anti-tumor necrosis factor (TNF) alpha, or tocilizumab. Effectiveness was evaluated by analyzing drug survival using Kaplan-Meyer analysis over 10-year follow-up. Survival rates were compared by log rank test, and hazard ratios (HRs) of therapy discontinuation were estimated through multivariate Cox-regression. RESULTS: Clinical characteristics were similar between the two groups, except for a significantly higher percentage of inadequate responders to prior bDMARDs in the seronegative RA patients (p= 0.02). Among seronegative RA, tocilizumab demonstrated a survival rate of 73.9% with a mean survival time (MST) of 76.8 months (95% CI 61-92), which was significantly higher than abatacept (37.5%, MST 37.1 months (95% CI 22-51; p= 0.01). Anti-TNF alpha therapy fell in the middle (50.0%, MST 63.5 months (95% CI 47-79) but the difference was not significant. Nevertheless, seropositive RA patients did not show significantly different drug survival rates. Negative predictors of drug discontinuation were RF/ACPA positivity (HR 0.56) and sex male (HR 0.58), but treatment with abatacept (HR 1.88) or anti-TNF alpha (HR 1.79), no co-therapy with cDMARD (HR 1.74), absence of bone erosions (HR 1.41), and higher HAQ (HR 1.58) were positive predictors. CONCLUSIONS: To confirm these preliminary findings and to explore the hypothesis of a distinctive therapeutic algorithm in seronegative RA, prospective studies on larger cohorts are needed.