Background/Purpose:

Exportin 1 (XPO1; also called chromosome region maintenance 1, CRM1) is a key protein that controls the export of ~220 cargo proteins and several mRNAs out of nucleus. Novel Selective Inhibitors of Nuclear Export (SINE) are oral XPO1 inhibitors that activate multiple tumor suppressor proteins and are currently in clinical development for a variety of cancers. SINE also force the nuclear retention of various cargos that play key roles in inflammation including the proteins IkB, COMMD1, FOXO, PPARγ, NRF2, RXRγ, as well as COX2 mRNA. Here, we report the in vitro effects of SINE on RA cells and their oral activity in vivo in the Collagen Induced Arthritis (CIA) and Collagen Antibody Induced Arthritis (CAIA) RA models.

Methods:

The effects of SINE on fibroblast-like synoviocytes (FLS) were tested in vitro by 1. Time-lapse imaging to quantify the anti-proliferative effects of SINE on RA FLS cell lines. 2. Quantifying anti-proliferative effects of SINE on activation of T-cells by bacterial superantigen presented by FLS. 3. Measuring SINE inhibition of cytokine secretion by FLS stimulated by cytokine-activated T-cells. Cytokines in culture supernatants were analyzed by Luminex assay. In the CAIA model, study animals were treated with vehicle, dexamethasone or various oral doses of the SINE KPT-355 on days 4, 6, 8 and 10. In the CIA model, study animals received vehicle, dexamethasone, or KPT-355 from day 11 to day 28 on QoD or QD regimens. A standard clinical scoring system was used to quantify the clinical symptoms of arthritis in both models. In the CIA model, the levels of cytokines and pro-inflammatory markers were measured in the synovial fluid using a Luminex assay and ELISA. Bone erosion within the paws was quantified with 3D micro-tomodensitometry. Histopathology was conducted on the hind paws of rats using H&E staining.

Results:

SINE inhibited RA FLS proliferation (IC₅₀ ~10nM) as well as T cell responses to bacterial superantigen presented by FLS that had been pretreated with IFN-γ. SINE showed minimal cytotoxicity to these cells.  SINE blocked the secretion of IL-6, IL-8 and other cytokines by FLS in a dose dependent manner (IC₅₀~100nM).  In both CIA and CAIA models, KPT-355 SINE treated animals had significantly lower disease scores compared to the vehicle treated animals. In the CIA model, peak clinical scores were 1.4±0.542 with KPT-355 compared to 8.5±0.707 with the vehicle. In the CAIA model peak clinical scores were 0.56 ± 0.29 with KPT-355 compared to 7.44 ± 0.85 with vehicle. Histological analyses of SINE treated animals showed significant reduction in the degeneration of articular cartilage and inflammation in the joint spaces. KPT-355 also significantly reduced the levels of IL-1ß (p=0.0262), IL-6 (p=0.0253), MCP-1 (p=0.0008) and CRP (p=0.0003) in the synovial fluid. Micro-CT data showed that SINE significantly prevented bone mineral density loss. 

Conclusion:

These studies demonstrate that SINE display potent anti-inflammatory activity, joint sparing activity, and protection from bone mineral density loss in established models of rheumatoid arthritis, justifying further development of SINE for RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/novel-selective-inhibitors-of-nuclear-export-attenuate-inflammation-and-prevent-bone-mineral-density-loss-in-multiple-preclinical-models-of-rheumatoid-arthritis/