Next steps
These reports, along with the thousands of papers published over the past few decades describing phenotypic and functional abnormalities in synovial tissue obtained from RA patients undergoing joint replacement surgery or, more recently, via STB early in the course of disease, have provided a wealth of information, Helen Michelle McGettrick, MD, noted in an editorial addressing the potential of STB analysis for “unlocking the hidden secrets to personalized medicine.”
The question, however, is whether they have moved the field closer to “translating this discovery science into new biomarkers or drugs to improve diagnosis or prognosis,” she wrote (Arthritis Res Ther. 2019;21[90]. doi: 10.1186/s13075-019-1871-5).
“Three sides of our square are in place: clinical expertise, technology, and patient willingness,” she said, arguing that the fourth side is “standardization in the handling, evaluation, and interpretation of STB.”
In fact, her editorial focused on a joint consensus of the European League Against Rheumatism Synovitis Study Group and the OMERACT Synovial Tissue Biopsy Group (Arthritis Res Ther. 2018;20[265]. doi: 10.1186/s13075-018-1762-1).
The groups, based on member survey responses, proposed a “consensual set of analysis items” to be used for synovial biopsies in clinical practice and translational research, including matters such as biopsy sampling, histologic criteria, and biopsy interpretation. Their work, according to Dr. McGettrick and the authors themselves, marked a step forward, but provided only a foundation for a standardization framework.
One particular area of synovial research that has received recent attention and which illustrates the need for standardization involves the role of synovial B cells in RA. The R4-RA researchers, in conjunction with the Pathobiology of Early Arthritis Cohort, are working to better define the relationship of synovial B cells to clinical RA phenotypes at various disease stages and drug exposures as a potential source of predictive and prognostic biomarkers, and in an article accepted for publication in Arthritis & Rheumatology, they describe a “robust semiquantitative histological B cell score that closely replicates the quantification of B cells by digital or molecular analyses.”
In their study of 329 patients, they demonstrated an ongoing B cell–rich synovitis more prevalent in patients with established RA who had inadequate response to tumor necrosis factor inhibitor therapy than in those with early RA (47.4% vs. 35%), but which does not appear to be captured by standard clinimetric assessment (Arthritis Rheumatol. 2019 Nov 29. doi: 10.1002/art.41184).
“Overall, our study confirms the relevance of synovial B cells in RA and suggests that the classification of patients into B cell–rich/–poor can contribute to patient stratification,” they concluded.
In a related editorial, Dana E. Orange, MD, and Laura T. Donlin, PhD, of the Hospital for Special Surgery, New York, note that previously discrepant findings with respect to the value of B cell infiltrate scores for predicting RA treatment response may relate to the lack of a standardized scoring system (Arthritis Rheumatol. 2019 Nov 29. doi: 10.1002/art.41185).
Together, these emerging findings are “advancing our understanding of the transcriptional and cellular characteristics of the synovium in RA,” they wrote, concluding that incorporation of synovial assessments into clinical management of patients is “the next step in empowering clinicians to apply advances in molecular immunology to better tailor treatment decisions.”
Indeed, an important goal is empowering rheumatologists to become adept in obtaining synovial biopsies in clinical practice, much like gastroenterologists collect tissue for biopsy via colonoscopy, Dr. Pitzalis said in an interview following his R4-RA presentation at the ACR meeting.
Dr. Hughes predicts that a subset will embrace the concept, but not all rheumatologists are interested and not all use musculoskeletal US in their practice.
“It requires a lot of training, there is a credentialing exam, and it’s not necessary for practicing rheumatology, but there is a lot of growth,” she said, noting that training is being promoted through the ACR and other organizations, and Europeans who are well-versed in US-guided STB have served as mentors. “It’s been a nice collaboration, and I think it’s just going to push the field forward ... it really is exciting – I think synovial biopsies will yield a lot of information and really, hopefully, help us target therapy and find new therapeutic targets that we haven’t even thought of.”
However, Dr. Pitzalis stressed that there remains much work to do.
“It’s important to understand this is early data and will require validation in larger and target-driven and biopsy-driven treatment clinical trials,” he said of the R4-RA findings.
Those efforts are underway; the REASON study, for example, is moving forward, having recently been awarded a National Institutes of Health Research Project Grant, Dr. Perlman said, explaining that the latest goal is to determine whether the transcription modules the investigators have identified to date can be predictive of treatment response.
He expects to report outcomes at ACR 2020, and noted that preliminary findings suggest that “we can tell, by 4 weeks, which patients will respond or not.”
Dr. Pitzalis and his colleagues are also working on their “next set of trials,” which are using biopsies for treatment allocation (B cell–poor patients get one drug, B cell–rich patients, another, for example), and he, too said he expects to have additional data to present at ACR 2020.
“If we are to demonstrate clinical utility, I think rheumatology will be ready to implement this methodology in clinical practice,” he said.
The authors interviewed for this article reported having no relevant financial disclosures.