tcsc0208 LY2228820 (Ralimetinib Dimesylate;LSN2322600)

Ralimetinib dimesylate (LY2228820) is a selective, ATP-competitive inhibitor of p38 MAPK α/β with IC₅₀s of 5.3 and 3.2 nM, respectively.

IC50 & Target: IC50: 7 nM (p38 MAPK)

In Vitro: Ralimetinib dimesylate (LY2228820) inhibits p38α, as well as the level of phosphoMAPKAPK-2 (pMK2) in RAW 264.7 cells, with IC₅₀ values of 7 nM and 34.3 nM, respectively. Furthermore, Ralimetinib dimesylate (LY2228820) inhibits lipopolysaccharide (LPS)-induced TNFα formation in murine peritoneal macrophages, with IC₅₀ of 5.2 nM^[1]. In multiple myeloma (MM) cells, including INA6, RPMI-8226, U266, and RPMI-Dox40, Ralimetinib dimesylate (LY2228820) (200 nM-800 nM) significantly blocks p38MAPK signaling, as revealed by its inhibition on phosphorylation of HSP27, a downstream target of p38MAPK, without affecting the expression level of HSP27. Ralimetinib dimesylate (LY2228820) (200 nM-400 nM) enhances bortezomib-induced cytotoxicity and apoptosis, but Ralimetinib dimesylate (LY2228820) alone doesn't inhibit the growth of MM.1S cells. Ralimetinib dimesylate (LY2228820) (200 nM-800 nM) also inhibits secretion of IL-6 and MIP-1α in long-term BM stromal cells (LT-BMSCs), BM mononuclear cells (BMMNCs), peripheral blood (PB) CD138⁺, CD138^- or PB CD14⁺ cells. Ralimetinib dimesylate (LY2228820) (400 nM-800 nM) also blocks osteoclastogenesis from CD14⁺ cells^[2].

In Vivo: In LPS-induced mice, Ralimetinib dimesylate (LY2228820) effectively inhibits the formation of TNFα with a threshold minimum 50% effective dose (TMED₅₀) less than 1 mg/kg. In a rat model of collagen-inducedarthritis (CIA), Ralimetinib dimesylate (LY2228820) displays potent effects on paw swelling, bone erosion, and cartilage destruction, with a threshold minimum 50% effective dose (TMED₅₀)of 1.5 mg/kg^[1]. Ralimetinib dimesylate (LY2228820) inhibits tumor phospho-MK2 in a dose-dependent manner (TED₅₀=1.95 mg/kg, TED₇₀=11.17 mg/kg) in mice implanted with B16-F10 melanoma. Ralimetinib dimesylate (LY2228820) inhibits MK2 phosphorylation: mouse in vivo TED₅₀=1.01 mg/kg (compound exposure approximately 100 nM) and human ex vivo IC₅₀=0.12 μM with either mouse or human PBMC^[3].