Efaproxiral is a haemoglobin (Hb) synthetic allosteric modifier, decreases Hb-oxygen (O2) binding affinity and enhances oxygenation of hypoxic tumours during radiation therapy ^[1]. IC50 & Target: haemoglobin (Hb)^[1] In Vitro: Efaproxiral binds to only one pair of symmetry-related sites in the Hb central water cavity^[2].
Efaproxiral readily crosses the red cell membrane in the presence of serum albumin solutions^[2].
Efaproxiral is not inhibited from entering erythrocytes in the presence of an anion-channel blocking agent (DIDS)^[2].
In Vivo: Efaproxiral (150 mg/kg, i.p.) increase tumor oxygenation，and increase the tumor growth inhibition of radiotherapy over 5 days of treatment^[3].
Efaproxiral reduces hemoglobin-oxygen binding affinity, which facilitates oxygen release from hemoglobin into surrounding tissues and potentially increases the pO(2) of the tumors^[4]