A blood test that uses a patient's unique genetic signature has shown some ability to predict nonresponse to tumor necrosis factor inhibitors as treatment for rheumatoid arthritis, an observational clinical study has found, but the test's predictive accuracy was well below 100%.
The test is the blood-based molecular signature response classifier (MSRC) that uses RNA sequencing data based on 23 different biomarkers: 19 RNA transcripts and 4 clinical features. The clinical features are body mass index, gender, patient global assessment, and anticyclic citrullinated protein (anti-CCP) status.
The NETWORK-004 study, published in Rheumatology and Therapy, was able to stratify patients who were likely to respond inadequately to TNFi therapy and could provide patient-specific information to guide therapy choice in RA patients regardless of whether they've already been on TNFi therapy. The study evaluated the MSRC test in 504 patients, 391 of whom were treatment naive.
Avoiding "Fail First" Approach
The idea behind the test is to circumvent the "fail first" approach in finding the right therapy for RA in an individual patient. While the test costs $4,995, Alif Saleh, chief executive officer of Scipher Medicine, which markets the test under the name PrismRA, said in a press release that it has the potential to reduce costs by $19,000 or more per patient per year by avoiding treatments that don't work. A previous study, which Scipher funded, reported that the test resulted in savings of $7,379 in per-patient costs of ineffective therapy. The same study reported a 25% decrease in costs for ineffective treatments for Medicare-eligible patients.
The price of RA drugs, particularly anti-TNF agents, is hefty and rising. GoodRx has reported that the price of RA drugs increased 92% from 2014 to 2019, and the prices for anti-TNF agents such as etanercept and adalimumab more than doubled in that period. Adalimumab can cost upwards of $84,000 per year while etanercept has a list price of around $72,000 a year. The pharmacy benefit manager WellDyne started covering the test MSRC in February.
Nehad Soloman, MD, a rheumatologist and internist at Midwestern University Arizona College of Osteopathic Medicine in Glendale and a compensated NETWORK-004 investigator, said the MSRC test would be indicated for confirmed RA patients for whom rheumatologists are considering biologic agents, particularly TNFi drugs. "You wouldn't do it on an RA patient who's been on several different medications because it doesn't serve a purpose at that point," he said.
The potential cost savings may not be the only reason to use the test, Soloman said. "You don't want to be dabbling with the wrong drug if there's another path you can try and save society some money as well as the time and energy it takes to monitor the patients – as well as the patient's pain," he said.
How the MSRC Test Works
The MSRC test detects a signal that's associated with a high or very high likelihood of inadequate response to TNFi therapies and indicates that the patient is unlikely to achieve low disease activity or remission with TNFi therapies. Response is defined as achieving ACR50 – meaning 50% improvement in American College of Rheumatology response criteria – at 6 months.
Test results are reported on a continuous 1-25 scale, explained Slava Akmaev, PhD, chief technology officer and head of therapeutics at Scipher. "The higher the score, the more likely the patient will have an inadequate response to TNFi therapies and be unable to reach low disease activity; the lower the score, the less likely the patient will have an inadequate response to TNFi therapies," he said. However, Akmaev noted that a low score does not ensure a positive response to TNFi therapies.
The MSRC test differs from the multibiomarker disease activity blood test (MBDA; marketed as Vectra by Myriad Genetics) in the number of biomarkers it measures: 19 RNA transcripts vs. 12 serum protein biomarkers in MBDA. The MBDA test is also intended to provide a quantitative, objective measurement of RA disease activity rather than to predict nonresponse to TNFi or other biologics. A number of studies have validated the MBDA test for predicting disease control in RA patients, but not necessarily response to TNFi therapy.
The "high" category threshold of the MSRC test corresponds to an approximate 90% chance of inadequate response to TNFi therapy, or a 10% chance of responding. The "very high" category threshold corresponds to an approximate 95% chance of inadequate response to TNFi therapy, Akmaev said.
NETWORK-004 used area under the curve (AUC) to measure the accuracy of the MSRC test. An AUC of 1 represents 100% accuracy. Overall, the MSRC had an AUC of 0.64, or 64% accuracy of predicting patients unlikely to respond to TNFi therapy and to achieve ACR50 at 6 months, with an odds ratio of 4.1 (95% confidence interval, 2.0-8.3; P = .0001).
The predictive accuracy went up to 74% with ORs of 3.4-8.8 for additional endpoints at 3 and 6 months (P < .01). Among patients who had already been on TNFi therapy, the predictive accuracy was 83% and associated with ORs of 3.3-26.6 based on ACR, 28-joint Disease Activity Score using C-reactive protein (DAS28-CRP), and Clinical Disease Activity Index (CDAI) metrics.
The investigators also performed an in-cohort cross-validation of the MSRC using baseline blood samples of 245 treatment-naive patients from the CERTAIN study, which yielded a 66% predictive accuracy for the ACR50 outcome at 6 months. Using the 19 RNA transcripts from the test, but not the clinical factors, the predictive accuracy was 62.5%. Using ACR70, CDAI, and DAS28 as measures for 6-month response, the cross-validation analysis of all 23 MSRC features yielded predictive accuracy of 64%-67%.
The study found significant differences in model scores between patients who did and did not have the molecular signal of nonresponse, and the proportion of patients who achieved low disease activity or remission at 6 months based on CDAI and DAS28-CRP measures was greater among those who lacked a molecular signature of nonresponse.
"Those who lack this signature can proceed with TNFi therapy and possibly achieve an increased response rate relative to the unstratified population," wrote lead study author Stanley B. Cohen, MD, and colleagues.
Daniel E. Furst, MD, emeritus professor at the University of California, Los Angeles, described the design of the NETWORK-004 study as "excellent," but said that it didn't overcome potential issues with the MSRC test itself. "The results unfortunately are great for group data but not for individuals, with a predictive area under the curve of 60% to 80%, it really is not that useful," he said. "Let's say you're a patient who's not doing well, and I do a test and it's positive; that still means that 20% of the time you will respond."
He also noted that he coauthored a paper that used decreases in DAS28 to predict nonresponse to certolizumab pegol plus methotrexate with 95% probability in the first 12 weeks of treatment. "That's closer to what we need," Furst said.
However, the MSRC test is a promising sign of where testing for predicting RA therapy is headed, he said. "We are steadily working toward genetic signatures that really are predictive on an individual basis," Furst said. "It's coming; it's just not here yet."
Furst had no relevant financial relationships to disclose. Soloman is a paid investigator and consultant to Scipher Medicine.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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Cite this: Can a Blood-Based Test Predict TNFi Nonresponse in RA? - Medscape - Aug 16, 2021.