Randomised, open labelled clinical trial to investigate synovial mechanisms determining response: Resistance to rituximab versus tocilizumab in RA patients failing TNF inhibitor therapy

Background: Biologic therapies have transformed the outlook for RA but the significant health economic impact of these therapies has highlighted the need to define predictive markers of response. Rituximab (RTX) is licensed for use following failure of csDMARDs and TNF inhibitor (TNFi) therapy. However, in this increasing therapeutically resistant cohort only 30% of patients achieve an ACR50 response. The observation in early RA that 50% of patients show low/absence of synovial B-cells prompted us to test the hypothesis that in these patients a biologic agent targeting alternative pathways maybe more effective. We report results from the first pathobiology-driven randomised controlled trial (RCT) in RA (R4RA) evaluating whether patient stratification according to the synovial Bcell rich/poor status enriches for response/non response to RTX. Methods: R4RA is a phase IV open-label RCT conducted in 19 European centres recruiting patients failing or intolerant to csDMARD therapy and at least one TNFi. Synovial tissue was obtained at trial entry and used to classify patients as B-cell rich or poor using both histological and RNA-seq classification criteria. Patients were randomised to receive RTX or tocilizumab (TCZ). The study was powered to test in the B cell poor population superiority of TCZ over RTX at 16 weeks. The primary and co-primary end-points were defined respectively as Clinical Disease Activity Index (CDAI) ≥50% improvement from baseline and Major Treatment response (MTR)= CDAI improvement ≥ 50% and CDAI <10.1. Results: The trial recruited to target (n=164) with a power of 89.5%. In the B cell poor cohort a numerically higher number of patients achieved the primary endpoint and a significantly higher number of patients achieved co-primary endpoint (MTR). Classification of patients as B cell poor/rich according to RNA-seq criteria enhanced the difference between TCZ and RTX, with a significantly higher number of TCZ treated patients reaching both CDAI 50% improvement and CDAI MTR in the B-cell poor group. Conclusion: In a RA B cell poor population failing csDMARDs and TNFi therapy, TCZ is more effective than RTX. This first biopsy-driven RCT suggests clinical utility for integrating molecular pathology profiling into treatment algorithms to allocate targeted therapies.