Hetrombopag, an Emerging Iron-Chelating Agent, Alleviates Systemic Iron Overload

Background: Iron overload is a syndrome in which excessive iron accumulates in the body, leading to tissue damage and functional disorders. This condition is common in patients with refractory anaemia who receive long-term red blood cell transfusions. Hetrombopag (HPAG) is a new generation, oral, small molecule, nonpeptide thrombopoietin receptor agonist that can chelate iron and alleviate iron overload while promoting haematopoiesis. Nevertheless, there is currently a lack of research on the iron-chelating function of HPAG, and its mechanism of regulating iron metabolism in the body is not clear.

Aims: The aim of this study was to clarify the iron-chelating function of HPAG, its effects on haematopoiesis, immune abnormalities, and tissue damage caused by iron overload and explore its potential mechanism of systemic iron metabolism, providing a new theoretical basis for the treatment of haematological diseases with HPAG.

Methods: Iron overload was induced in mice by intraperitoneal injection of iron dextran, and treatment was performed with HPAG, deferasirox (DFX, an iron chelator), or ferrostatin-1 (Fer-1, a ferroptosis inhibitor). The iron-chelating function of HPAG and its effects on haematopoiesis, immune abnormalities, and tissue damage caused by iron overload were clarified in vivo, and the underlying mechanism was explored via transcriptomics and lipidomics.

Results: Iron-overloaded mice treated with HPAG or DFX showed recovery in terms the of weight loss, hepatomegaly, histopathological iron deposition, reduced glutathione/oxidized glutathione (GSH/GSSG) balance and superoxide dismutase (SOD) activity, and increased non-transferrin-bound iron (NTBI) and malondialdehyde (MDA) levels caused by iron overload. Importantly, compared with untreated mice, iron-overloaded mice treated with HPAG, DFX, or Fer-1 presented restored tissue fibrosis and increased numbers of long-term haematopoietic stem cells (LT-HSCs), short-term haematopoietic stem cells (ST-HSCs), and Treg cells and an increased CD4/CD8 ratio. Lipidomic and transcriptomic data from the liver and c-kit+ cells in bone marrow revealed that HPAG induces molecular changes consistent with intracellular iron reduction and lipid peroxidation inhibition, with decreased expression of the HAMP, FTH1, BMP6, and HMOX1 genes. Furthermore, compared with those in DFX-treated mice, immune response-related signalling pathways, especially those related to the inhibition of the response to type I interferon, were significantly enriched in HPAG-treated mice.

Conclusion: HPAG is an emerging iron-chelating agent and a potential inhibitor of ferroptosis that alleviates tissue damage, haematopoietic stem cell injury, and immune abnormalities caused by systemic iron overload and provides an immunoregulatory function.