Tocilizumab Outperforms Rituximab for RA Patients with Low B-Cell Levels

Constantino Pitzalis, MD, PhD

A recent study is shedding light on the effectiveness of tocilizumab and rituximab in rheumatoid arthritis patients with low B-cell levels in synovial tissue.

Results of the study, which were presented at the 2019 American College of Rheumatology annual meeting in Atlanta, GA, demonstrated tocilizumab was more effective than rituximab in this specific patient population.

With previous research indicating patients with early rheumatoid arthritis had low levels or the complete absence of B-cell infiltration in their synovial tissue, investigators designed a 48-week, phase 4 study to compare the two popular treatments.

The multi center, open-label, randomized, controlled trial included a total of 164 patients from centers in Europe who were randomized to receive either rituximab and tocilizumab. Investigators noted all patients in the study were failing or intolerant to csDMARD therapy and at least 1 TNF inhibitor.

Synovial tissue of patients was obtained at trial entry and investigators classified patients as B-cell rich or B-cell poor. Randomization of patients was based on this histological classification.

The primary outcome measures of the study included the Clinical Disease Activity Index (CDA) improvement of 50 or more from baseline and Major Treatment response (MTR) improvement of 50% or more and CDAI less than 10.1. Secondary outcome measure for the study was CDAI response in the B-cell rich cohort.

The study, which was powered to test superiority of tocilizumab in B-cell poor patients, had a power of 89.5%. OF the 164 patients included in the study, 83 received rituximab and 81 received tocilizumab. From these groups, 81 rituximab patients and 73 tocilizumab patients completed treatment to week 16.

Upon analyses, tocilizumab appeared to be more effective for treating this patient population. In the B-cell poor group, investigators observed a significantly higher number of patients met the primary endpoint of MTR(46.3% versus 23.7%) and additional secondary endpoints.

“These findings are important as they indicate that patients with low level of B cells in the synovial tissue are less likely to respond to rituximab and should be treated with alternative medications,” said study presenter Costantino Pitzalis MD, PhD, director of the Center for Experimental Medicine and Rheumatology at Barts and the London School of Medicine and Dentistry.

Conversely, in B-cell rich patients investigators noted there was no significant difference in the majority of the study’s endpoints. Investigators did note an increased number of adverse events in patients treated with tocilizumab compared to those treated with rituximab.

This study, “A Randomized, Open Labelled Clinical Trial to Investigate Synovial Mechanisms Determining Response - Resistance to Rituximab versus Tocilizumab in Rheumatoid Arthritis Patients Failing TNF Inhibitor Therapy,” was presented at ACR 2019 by Costantino Pitzalis MD, PhD.