Omaveloxolone

Omaveloxolone (RTA 408) is an antioxidant inflammation modulator (AIM), which activates Nrf2 and suppresses nitric oxide (NO). Omaveloxolone attenuates osteoclastogenesis by inhibiting STING dependent NF-κb signaling. IC50 & Target:Nrf2^[1] In Vitro:To evaluate the anti-inflammatory activity of Omaveloxolone (RTA 408), RAW 264.7 mouse macrophage cells are treated with Omaveloxolone for two hours and then IFNγ is added to stimulate NO production and release into the media. Omaveloxolone dose-dependently reduces NO concentrations in the media with an IC₅₀ value of 4.4±1.8 nM. The potency of Omaveloxolone in this assay is similar to that of Bardoxolone methyl, which has an IC₅₀ value of 1.9±0.8 nM. Nrf2 activation is required for AIM-mediated NO suppression. A decrease in nitric oxide synthase 2 (Nos2) protein levels is observed in bardoxolone methyl-treated RAW 264.7 cells, which is attenuated when Nrf2 mRNA levels are reduced by siRNA. To evaluate the anticancer activity of Omaveloxolone, a panel of eight human cell lines derived from tumors of different origin are treated with Omaveloxolone and measured cell growth 72 hours later using the sulforhodamine B (SRB) assay. Omaveloxolone inhibits the growth of all tumor lines with an average GI₅₀ value of 260±74 nM. To determine whether Omaveloxolone induces apoptosis, the panel of tumor cells are treated with Omaveloxolone and the caspase substrate, DEVD-AFC, for 24 hours. Omaveloxolone dose-dependently increases DEVD-AFC cleavage, indicating that Omaveloxolone treatment triggers caspase activation in cancer cells. Caspase-3 and caspase-9 cleavage is also observed by western blot at the same concentrations of Omaveloxolone that increases DEVD-AFC cleavage^[1]. In Vivo:To determine whether Omaveloxolone (RTA-408) is an effective mitigator of hematopoietic acute radiation syndrome after bone marrow-lethal doses of total-body irradiation (TBI), mice are administered 3 daily injections of 17.5 mg/kg Omaveloxolone beginning 24 h after TBI. Teatment with Omaveloxolone results in the 35 day survival of 100% of 7 Gy (LD_40/35) TBI mice (P<0.05) and 60% of 7.5 Gy (LD_100/13) TBI mice (P<0.0001)^[2].