Evaluation of the Carcinogenic Potential of Roxadustat (FG-4592), a Small Molecule Inhibitor of Hypoxia-Inducible Factor Prolyl Hydroxylase in CD-1 Mice and Sprague Dawley Rats

Abstract

The carcinogenic potential of roxadustat (FG-4592), a novel orally active, heterocyclic small molecule inhibitor of hypoxia-inducible factor prolyl hydroxylase (HIF-PH) enzymes in clinical development for treatment of anemia, was evaluated in CD-1 mice and Sprague Dawley rats. Inhibition of HIF-PH by roxadustat leads to a rapid increase in cytoplasmic HIF-α concentrations, followed by translocation of HIF-α to the nucleus and upregulation of HIF-responsive genes, including erythropoietin. Roxadustat was dosed by oral gavage 3 times weekly (TIW) for up to 104 weeks in mice at 0, 15, 30, and 60 mg/kg and in rats at 0, 2.5, 5, and 10 mg/kg. Treatment-associated changes in hematology parameters were consistent with the pharmacologic activity of roxadustat and included elevations in hematocrit in mice at 30 and 60 mg/kg TIW and elevations in erythrocyte count, hemoglobin, hematocrit, and red cell distribution width in rats at 10 mg/kg TIW. No increase in mortality or neoplastic effects compared with vehicle controls was observed after roxadustat treatment in either species. No treatment-related nonneoplastic findings were observed in mice, whereas nonneoplastic microscopic findings in rats were limited to atrial/aortic thromboses at 10 mg/kg TIW males and bone marrow hypercellularity in all treated male and female groups, consistent with the pharmacology of roxadustat. In conclusion, roxadustat administered by oral gavage to mice and rats TIW for up to 104 weeks resulted in dose-dependent exposure and hematologic effects with no effect on survival or development of neoplastic lesions at up to 60 mg/kg in mice and up to 10 mg/kg in rats.

Perspectives for the therapy of anemia of chronic diseases

“…Therefore, further research on the long-term safety of HIF hydroxylase inhibitors is needed, with particular attention to the assessment of the risk of tumorigenesis. It should be emphasized that in rat studies, roxadustat did not show carcinogenic properties [68]. Another potential threat is that HIF stabilization may be associated with an increase in circulating fibroblast growth factor 23 (FGF23) level, and high concentrations of FGF23 have been associated with cardiovascular complications and bone mineralization disorders.…”

Source and microenvironmental regulation of erythropoietin in the kidney

“…In contrast to sub-cutaneous recombinant Epo application, which results in peaks in plasma Epo concentration and may underlie adverse outcomes [46], PHI treatment results in smaller fluctuations in plasma Epo levels [47][48][49]. Long-term treatment of mice and rats with the PHI FG-4592/roxadustat has no effect on the development of neoplastic lesions [50] and does not promote tumour initiation, progression or metastasis in a VEGF-sensitive model of spontaneous breast cancer [51]. However, a cautious outlook remains until the potential nonerythropoietic side effects because of activation of the HIF or other pathways [52] have been thoroughly addressed.…”

Multiwavelength UV-metric and pH-metric determination of the dissociation constants of the hypoxia-inducible factor prolyl hydroxylase inhibitor Roxadustat

“…12 showed the extrapolation of the mixed dissociation constants to the zero value of an ionic strength according to the limited Debye-Hückel law for four dissociation constants at 25 0 C and 37 0 C using UV-metric data (Fig. 12a, b) pK T a1 = 3.60(04), pK T a2 = 5.62 (14), pK T a3 = 7.66 (16), pK T a4 = 9.08(02) at 25°C and pK T a1 = 3.60(04), pK T a2 = 5.73 (10), pK T a3 = 7.52(10), pK T a4 = 8.99(02) at 37°C and using pH-metric data (Fig. 12c, d) pK T a1 = 4.33(09), pK T a2 = 6.57 (11), pK T a3 = 8.88(05), pK T a4 = 9.03(04) at 25°C and pK T a1 = 4.25(09), pK T a2 = 6.49 (10), pK T a3 = 8.80(06), pK T a4 = 9.00(05) at 37°C.…”

“…Upon administration, Roxadustat binds to and inhibits HIF-PHI, an enzyme responsible for the degradation of transcription factors in the HIF family under normal oxygen conditions. This prevents HIF breakdown and promotes HIF activity [10,11]. Increased HIF activity leads to an increase in endogenous erythropoietin production, thereby enhancing erythropoiesis [7].…”