THU0419 BIOMARKERS OF BONE AND CARTILAGE TURNOVER CTX-I AND CTX-II PREDICT TOTAL JOINT REPLACEMENTS IN OA
Authors: Jonathan Bjerre-Bastos, Anne-Christine Bay-Jensen, Morten Karsdal, Inger Byrjalsen, Jeppe Ragnar Andersen, Bente Juel Riis, Claus Christiansen, Asger Reinstrup Bihlet
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Osteoarthritis (OA) can lead to joint failure and ultimately total joint replacement (TJR). Identifying risk-factors of developing joint failure is of interest for clinicians and researchers. Currently late-stage clinical trial design for evaluating new treatments in OA is evolving with the possible utilization of accelerated approval pathways. This may require outcome studies with longer duration, in which joint failures may qualify as an endpoint. However, TJRs are relatively rare events and are known to be biased by doctor/patient interactions as well as local practice guidelines, and consequently, there is a need for objective non-invasive measures, such as soluble biomarkers (BM), to enrich the population for this outcome. BM may act as important tools in investigating the association between biochemical/pathological processes and risk of joint failure. Degradation of collagens type I and II are known to be involved in OA disease progression, and the biomarkers CTX-I (C-telopeptide of crosslinked collagen type I), a marker of bone degradation, and CTX-II (C-telopeptide of crosslinked collagen type II), a marker of cartilage degradation, may reflect disease progression with clinical relevance for the risk of joint failure. <h3>Objectives</h3> To evaluate baseline (BL) BM sCTX-I and uCTX-II as predictors of TJR. <h3>Methods</h3> Data from two clinical trials investigating oral salmon calcitonin (SMC) in OA, NCT00486434 and NCT00704847, was analyzed post-hoc. Data was dichotomized by the bottom and top quartile of the respective BM concentration at BL to compare the number TJRs of the knee or hip in groups with high vs. low sCTX-I or uCTX-II, respectively. For means of visualization, plotted in Kaplan-Meier curves. Cox Proportional Hazard Regression was performed to determine the association of BL sCTX-I and uCTX-II to the incidence of TJR while adjusting for co-variates; age, BMI, and gender. Data from both treatment groups were analyzed. Only the first reported incident was included in the analysis for each subject. <h3>Results</h3> A total of 68 TJRs of knee or hip were reported, of which 49 were knees and 18 were hips. One patient underwent two TJRs, resulting in 67 subjects with events. Results from the Cox Proportional Hazard Regression adjusted for covariates of age, BMI, and sex (table 1), indicate that high BL sCTX-I compared to low was associated with a 3.4 times higher risk of undergoing an arthroplasty of the knee or hip within a two-year period (p=0.04). High BL uCTX-II compared to low was associated with a 3.1 times higher risk of undergoing a TJR of the knee or hip during the study period (p=0.04), and an 8.9-fold increased risk of undergoing a knee replacement during the study period (p=0.02). TJR events over time in groups of high or low uCTX-II through the study are illustrated in figure 1. <h3>Conclusion</h3> High levels of sCTX-I and uCTX-II at BL were associated with increased risk of undergoing TJR of the knee or hip during the two year study. Our findings support the role of sCTX-I and uCTX-II as important biomarkers in clinical OA trials evaluating incidence of TJRs. <h3>Disclosure of Interests</h3> Jonathan Bjerre-Bastos Employee of: I am a full-time employee in Nordic Bioscience, Anne-Christine Bay-Jensen Shareholder of: I own shares of Nordic Bioscience, Employee of: I am a full-time employee in Nordic Bioscience, Morten Karsdal Shareholder of: I own shares of Nordic Bioscience, Employee of: I am a full-time employee in Nordic Bioscience, Inger Byrjalsen Employee of: I am a full-time employee in Nordic Bioscience, Jeppe Ragnar Andersen Shareholder of: Nordic Bioscience, Employee of: Nordic Bioscience, Bente Juel Riis Shareholder of: Yes, I own shares in Nordic Bioscience, Employee of: I am a full-time employee in Nordic Bioscience, Claus Christiansen Shareholder of: Yes, I own shares in Nordic Bioscience, Employee of: I am a full-time employee in Nordic Bioscience, Asger Reinstrup Bihlet Shareholder of: Yes, I own shares in Nordic Bioscience., Employee of: I am a full-time employee in Nordic Bioscience