Session Title: Biology and Pathology of Bone and Joint - Poster II
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: The Spleen tyrosine kinase (Syk) inhibitor fostamatinib was not approved as treatment for rheumatoid arthritis (RA) due to insufficient effect on joint structure in the phase III OSKIRA-1 study. Here we use a translational model system to investigate the direct effect of Fostamatinib on the extracellular matrix (ECM) of the target tissues (cartilage, bone, and synovium) for a better understanding of the insufficient effect in joint structure found in OSIKRA-1.
Methods: Human mature osteoclasts (HOC) seeded on bone, bovine cartilage explants (BEX) and human synovial explants (SME) were treated with the active metabolite of Fostamatinib, R406, at 5µM-0.05µM. Osteoclasts were co-stimulated with 25 ng/ml M-CSF and RANKL, while BEX and SME were co-stimulated with TNFα 2 ng/mL and OSM 10 ng/mL (O+T) or TNFα 10 ng/mL, respectively. CTX-1 and Calcium (Ca2+) were measured in conditioned medium (CM) from HOC. Metabolic activity of HOC was assessed with Alamar Blue®. C2M and AGNx1 were measured in CM from BEX, while acMMP3, C1M, and C3M were measured in CM from SME. The biomarkers in BEX and SME CM were measured at 4 time points and the total release were quantified by area under the curve (AUC). CTX-1, C2M, AGNx1, acMMP3, C1M, C2M and C3M were measured with ELISA. Ca2+was measured with ADVIA Chemistry system. Statistical differences of metabolic activity was calculated with One-way ANOVA with Dunnett’s multiple comparison test. Statistical differences between biomarkers levels or AUC were calculated with Kruskall Wallis test with Dunn’s multiple comparision test.
Results: R406 decreased the release of CTX-1 (Fig 1A) and Ca2+ in a dose-dependent manner, with a significant decrease at 1µM (P<0.01). This might be due to a toxic effect of R406 on HOC (Fig 1B) (P<0.05). In cartilage, R406 decreased the total release of C2M and AGNx1 in a dose-dependent manner. C2M was inhibited a concentrations down to 1.25µM (P=0.034), and AGNx1 down to 5µM (P=0.012). In synovial explants, R406 tended to decrease release of C3M (Fig 1e), C1M and acMMP3 (Fig 1f) at 5µM, but this was not significant.
Conclusion: Serum-based biomarkers of the joint ECM turnover were measured in CM from HOC, cartilage and synovial explant cultures. R406 decreased bone resorption and HOC metabolic activity in a dose-dependent manner, together with the MMP-mediated degradation of type II (C2M) collagen and aggrecanse degradation of aggrecan (AGNx1) in cartilage. However, R406 had limited effect on the inflammation driven MMP-mediated degradation of type I (C1M) and III (C3M) collagen and activation of MMP-3. From these data it is expected that Fostamatinib would have some effect on bone and cartilage, but not on inflammation driven degradation of the synovium.
To cite this abstract in AMA style:Kjelgaard-Petersen CF, Bay-Jensen AC, Christiansen TG, Karsdal MA, Hägglund P, Thudium CS. Test of the Spleen Tyrosine Kinase Inhibitor Fostamatinib in a Translational Joint Tissue Model Show Significant Effect on Bone, but Not on Synovial Tissue [abstract]. Arthritis Rheumatol. 2016; 68 (suppl 10). https://acrabstracts.org/abstract/test-of-the-spleen-tyrosine-kinase-inhibitor-fostamatinib-in-a-translational-joint-tissue-model-show-significant-effect-on-bone-but-not-on-synovial-tissue/. Accessed September 19, 2019.
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