Roxadustat Activates Thyroid Hormone Receptors α and β at Clinically Relevant Concentrations

Roxadustat, a drug recently approved for treating renal anemia, might activate thyroid hormone receptors (TRα and TRβ). We, thus, investigated the direct effects of roxadustat on intact TRα and TRβ in vitro. U2OS, MCF-7, COS-7, and Caco-2 cells were transiently transfected with a firefly luciferase reporter plasmid highly responsive to the activation of TRα and TRβ, along with a plasmid overexpressing either TRα or TRβ. Transfected cells were incubated for three hours in 100% thyroid hormone-stripped fetal bovine serum (FBS) with or without either roxadustat or triiodothyronine (T3). Also, transfected U2OS cells were placed for three hours in 100% unprocessed normal adult human serum with or without the addition of either roxadustat or T3. Cell lysates were measured for firefly luciferase activity. Roxadustat induced firefly luciferase activities when added at clinically achievable serum concentrations in TRα- or TRβ-transfected U2OS, MCF-7, COS-7, and Caco-2 cells placed in thyroid hormone-deprived FBS. The induction was comparable to or greater than that observed with T3 added at normal or even supranormal serum concentrations. Roxadustat also increased firefly luciferase activities in TRα- or TRβ-transfected U2OS cells in adult human serum. These data suggest the possibility that roxadustat could activate TRα and TRβ at clinically relevant concentrations. Physicians prescribing roxadustat should be aware of its thyromimetic activity.