KRN5, a derivative of KRN2, is an oral active Nuclear factor of activated T cells 5 (NFAT5) suppressor, with an IC 50 of 750 nM. KRN5 has potential to treat NFAT5-mediated Chronic Arthritis In Vitro KRN5 is less toxic than BBR as determined by a cytotoxicity assay, hERG K+ channel assay, cytochrome inhibition assay, and liver microsomal metabolic stability test, which makes it a potential drug candidate. KRN5 at a concentration of 1 μM inhibits the expressions of NFAT5, IL-6,MCP-1, and GM-CSF,which are NFAT5 target molecules, in RAW264.7 macrophages stimulated with LPS. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo Oral feeding of KRN5 (15 mg/kg and 60 mg/kg) every other day for 3 weeks from day 21 dose-dependently mitigates arthritis severity . The concentration of serum anti-type II collagen IgG also significantly decreases in the sera of KRN5-treated mice. TNF-α and IL-6 production by LPS-stimulated splenocytes are significantly lower in KRN5-treated CIA mice than in vehicle-treated mice . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: 8-week-old DBA/1Jmice immunized with bovine type II collagen . Dosage: 15 mg/kg and 60 mg/kg. Administration: Orally on alternate days (every other day) for 3 weeks. Result: Dose-dependently mitigated arthritis severity. Form:Solid IC50& Target:IC50: 750 nM (NFAT5)