Conference Coverage

B-cell-poor RA responds better to tocilizumab than to rituximab



– Tocilizumab proved more effective than rituximab in B-cell-poor but not in B-cell-rich patients with RA who have had an inadequate response to disease-modifying antirheumatic drugs (DMARDs) and tumor necrosis factor inhibition in the randomized, open-label, 48-week, phase 4 R4-RA trial.

Dr. Constantino Pitzalis, head of the Centre for Experimental Medicine & Rheumatology, Queen Mary University of London Sharon Worcester/MDedge News

Dr. Constantino Pitzalis

If validated, the findings of the trial – the first randomized, controlled, biopsy-driven trial in RA – could have “massive implications” for treatment selection and improved outcomes, Constantino Pitzalis, MD, reported during a press conference at the annual meeting of the American College of Rheumatology.

Of 164 RA patients who were failing or intolerant to conventional synthetic (cs) DMARD therapy and at least one tumor necrosis factor inhibitor (TNFi), 83 were randomized to receive rituximab and 81 received tocilizumab. Of those patients, 49.1% were considered B-cell poor (BCP) based on synovial tissue biopsies obtained at trial entry.

The BCP patients treated with tocilizumab were numerically more likely than those treated with rituximab to achieve the coprimary endpoint of Clinical Disease Activity Index (CDAI) improvement of at least 50% from baseline at 16 weeks (56.1% vs. 44.7%), and they were significantly more likely – twice as likely, in fact – to achieve the coprimary endpoint of CDAI improvement of at least 50% from baseline at 16 weeks as well as CDAI score less than 10, indicating a major treatment response (46.3% vs. 23.7%), said Dr. Pitzalis, head of the Centre for Experimental Medicine & Rheumatology at Queen Mary University of London.

BCP patients receiving tocilizumab also were significantly more likely to achieve a number of secondary endpoints, he noted.

In the B-cell-rich (BCR) population, no significant differences were seen in the majority of endpoints with tocilizumab versus rituximab, he said.

Study participants had a mean age of 55-56 years and were intolerant of or refractory to csDMARDs and at least one TNFi. They were recruited from 19 centers in Europe, were randomized and treated with standard doses of rituximab or tocilizumab, and were stratified based on histologic classification (BCP vs. BCR). Baseline characteristics were comparable among the treatment groups, Dr. Pitzalis said.

Adverse events occurred in 62 and 68 patients in the rituximab and tocilizumab groups, respectively, and serious adverse events occurred in 8 and 12 patients, respectively, thus 40% of all serious adverse events occurred in the rituximab group and 60% in the tocilizumab group. Infections and serious infections each occurred in three patients in each group, and two patients in each group discontinued treatment because of adverse events.

B cells are pivotal to RA pathogenesis, as demonstrated by the efficacy of the B-cell-depleting agent, rituximab. However, rituximab, which is licensed for use following failure of csDMARDs and TNFi therapy, is only effective for achieving a 50% improvement in ACR response criteria at 6 months in about 30% of such patients, Dr. Pitzalis noted. In a recent early RA cohort, he and his colleagues found synovial heterogeneity, with more than half of patients showing low or no synovial B-cell infiltration.

“So why would you give them rituximab?” he asked, explaining the rationale for the R4-RA trial: The hypothesis was that alternative biologic agents targeting alternative pathways may be more effective in BCP patients.

“The results showed quite clearly that rituximab was inferior to tocilizumab in this patient group,” he said. “We demonstrated that tocilizumab is more effective than rituximab in achieving low disease activity in patients who had, on synovial biopsy, low levels of B-cell infiltration.

“The study really highlights the importance of integrating molecular pathology into the clinical algorithms, because making the diagnosis is not sufficient. We really need to know what the pathology of the patient is so we can give the right drug to the right patients.”

Dr. Donald Thomas, a rheumatologist in private practice in Silver Spring, Md.

Dr. Donald Thomas

Donald Thomas, MD, a rheumatologist in private practice in Silver Spring, Md., called the study “fascinating,” and noted during a question-and-answer period during the press conference that, during his lifetime, he “has probably wasted tens of thousands to hundreds of thousands of dollars,” using the trial-and-error approach to treatment.

“We can only treat by trial and error ... so being able to pinpoint therapy is just phenomenal,” he added, further noting in an interview after the press conference that finding the right treatment can be “such a struggle.”

“I literally have patients who have gone through 10 medicines and wasted thousands of dollars,” he said.

In response to a question from Dr. Thomas about the potential for rheumatologists to do their own synovial biopsies to help guide treatment in the event the findings are validated, Dr. Pitzalis said that is both feasible and an important goal.

“All the biopsies [in the study] were carried out by rheumatologists,” he noted. “We have trained over 150 rheumatologists worldwide, including at 15 centers in the United States. ... We want to empower the rheumatologists to do it.”

He added that “this is early data ... and will require validation in larger trials,” but said the point is that “we can’t continue to just give these drugs and see if the patient responds.”

R4-RA is funded by the National Institute of Health Research Efficacy and Mechanism Evaluation program. Dr. Pitzalis and some of the other study authors reported financial relationships with Roche/Genentech, which markets tocilizumab and rituximab, and other pharmaceutical companies.

SOURCE: Pitzalis C et al. Arthritis Rheumatol. 2019;71(suppl 10), Abstract 2911.

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