Efaproxiral: a novel radiation sensitiser

Abstract

Efaproxiral (RSR13) is a synthetic allosteric modifier of haemoglobin that reduces its oxygen binding affinity. By facilitating the release of oxygen from haemoglobin, efaproxiral causes an increase in whole blood P₅₀ (partial pressure of oxygen which results in 50% haemoglobin saturation) and an increase in the Po₂ (partial pressure of oxygen) in the tissue. The therapeutic strategy of enhancing oxygen unloading from haemoglobin to tissue emulates and amplifies physiological tissue oxygenation and can enhance the oxygenation of hypoxic tumours. Since hypoxia is known to decrease the effectiveness of radiation therapy, the use of efaproxiral as a radiation sensitiser may be advantageous. Unlike previous radiation sensitisers, efaproxiral does not need to enter the cancer cells to increase radiosensitivity. Phase I – III trial data have defined the safety profile and dosing of the drug, with the potential benefit for extended survival.

• efaproxiral
• hypoxia
• radiation sensitiser
• radiation therapy
• RSR13