Patients with rheumatoid arthritis (RA) whose symptoms improved after they started taking nonbiologic disease-modifying antirheumatic drugs also demonstrated restored balance in their oral and gut flora, which could potentially serve as a marker of how they’ll respond to DMARDs, an observational study in the United Kingdom found.
Reporting in the journal Rheumatology, researchers led by Nathan Danckert, PhD, a genetic epidemiology researcher at King’s College London, and Maxim Freidin, PhD, of the Queen Mary University of London, London, England, evaluated stool and saliva samples of 144 people recently diagnosed with RA before and after they started DMARD therapy.
ChrisChrisW/Getty Images
“We identified a partial restoration of the microbiome to a more eubiotic state in RA patients at 6 weeks and 12 weeks of DMARD treatment in participants [who] responded well to DMARD therapy,” they wrote. “This was further supported by long-term (> 1 year) treated DMARD RA participants with similar community shifts.” Microbiomes, they said, are “a promising diagnostic tool” for directing DMARD therapy.
Study Goal Not Met
The goal of the study was to determine whether the microbiome of patients before they began treatment with DMARDs could predict their response to therapy. The patients were enrolled in the IMRABIOME study. Eligible patients had inflammatory arthritis symptoms for a year or less and met the clinical criteria for RA. Most patients were taking methotrexate (134 at baseline, 77 at 12 weeks), but study participants were also taking sulfasalazine (16 at baseline, 14 at 12 weeks) or hydroxychloroquine (58 at baseline, 45 at 12 weeks) either in combination or as a stand-alone treatment.
The study found a total of 26 different stool microbes that decreased in patients who had a minimal clinically important improvement (MCII) after starting DMARD therapy. At 6 weeks, the most significant declines were in Prevotella species. At 12 weeks, the greatest declines were in Streptococcus.
The researchers also developed models that used gut and oral metagenomes to predict MCII in patients starting DMARD therapy. They used a previously published microbiome dataset as a validation cohort for the model, but they acknowledged their models “were not as strong” as three previously published models. “Our findings support the hypothesis of DMARD restoration of a eubiotic gut microbiome when patient and treatment align,” the authors wrote.
They noted they had anticipated finding baseline microbiome samples that would help predict treatment responses. While baseline evaluation didn’t differentiate between responders and nonresponders, they wrote that a longitudinal analysis demonstrated changing microbiota and a positive response to therapy, with declining levels of Prevotella and Streptococcus species most pronounced at 6 and 12 weeks, respectively.
“Microbiomes provide a promising diagnostic tool for guiding therapeutic decisions in the future,” the study authors wrote.
Commentary
In commenting on the study, Gregg J. Silverman, MD, professor of medicine and pathology at the New York University School of Medicine, New York City, said it “was carefully performed, technically it was actually quite impressive, and the scale of the study actually was quite suitable.”
NYU School of Medicine
Dr. Gregg J. Silverman
However, the study fell short of achieving its primary goal of using the microbiome to predict treatment response, he said. “Basically, they could not find there was anything they could correlate with clinical response rates, although they did find that the presence or absence of certain bacteria at 6 weeks or 12 weeks into treatment correlated with a clinical response,” he said.
The multiplicity of DMARDs used by the study population was “one of the complicating factors” of the study, Dr. Silverman said. “It would’ve been a much more easily interpreted study if it used just a single agent like methotrexate,” he said. “I think that’s problematic, but I do think this contributes to getting us a little further down the road of understanding how the microbiome can influence the pathogenesis of rheumatoid arthritis response to treatment.”
One of the questions surrounding the microbiome changes is whether they occurred because of the effect of the therapy itself or because the disease activity subsides, Dr. Silverman said. “So, you’re not sure if it’s cause or effect. There’s evidence to suggest that either could be true.”
This study adds to a 2022 study that found a similar effect with methotrexate, Dr. Silverman said. “They considered a lot of variables, and they considered a lot of potential confounding effects,” he said. “So, their data were well-considered, and they will actually hold up over time and contribute to the next range of studies that will be performed, no doubt, in this area.”
It would be better if those future studies focused on just one DMARD drug and studied the recovered bacteria in animal models to gain a better understanding of how they correlate to pathogenesis, Dr. Silverman added.
The study received funding from Versus Arthritis. Dr. Danckert, Dr. Freidin, and coauthors, as well as Dr. Silverman, reported no relevant financial relationships.
A version of this article appeared on Medscape.com.