Efaproxiral is a haemoglobin (Hb) synthetic allosteric modifier, decreases Hb-oxygen (O2) binding affinity and enhances oxygenation of hypoxic tumours during radiation therapy In Vitro Efaproxiral binds to only one pair of symmetry-related sites in the Hb central water cavity. Efaproxiral readily crosses the red cell membrane in the presence of serum albumin solutions. Efaproxiral is not inhibited from entering erythrocytes in the presence of an anion-channel blocking agent (DIDS). MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo Efaproxiral (150 mg/kg, i.p.) increase tumor oxygenation，and increase the tumor growth inhibition of radiotherapy over 5 days of treatment. Efaproxiral reduces hemoglobin-oxygen binding affinity, which facilitates oxygen release from hemoglobin into surrounding tissues and potentially increases the pO(2) of the tumorsMCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: Female C3H/HEJ mice (18–20 g), with radiation-induced fibrosarcoma tumor (RIF-1) cells xenograftDosage: 150 mg/kg Administration: Intraperitoneal injection; prior to X Irradiation (4 Gy/day), for 5 days Result: Significantly increased tumor oxygenation by 8.4 to 43.4 mmHg within 5 days, with maximum increases at 22–31 minutes after treatment. Form:Solid IC50& Target:haemoglobin (Hb)