Efaproxiral: a radiation enhancer used in brain metastases from breast cancer

To review the mechanism of action and clinical data of efaproxiral use in brain metastases of breast cancer.

Articles were identified through MEDLINE (1966-June 2005) and EMBASE (1980-May 2005) searches using the key words efaproxiral and RSR13. Published abstracts over the previous 10 years from various scientific meetings, including American Society of Clinical Oncology and San Antonio Breast Cancer Symposium, were also searched for investigations of efaproxiral. Data on efaproxiral were also provided by Allos Therapeutics.

All published clinical data in humans regarding efaproxiral use in brain metastases from breast cancer were selected for this review. In addition, published studies in humans that discussed the pharmacokinetics, pharmacodynamics, and safety of efaproxiral were evaluated.

Efaproxiral is a synthetic allosteric modifier of hemoglobin that results in a shift of the hemoglobin oxygen dissociation curve to the right. Therefore, oxygen is more readily released from hemoglobin into tissues. Efaproxiral demonstrated a significant survival benefit when used as a radiation enhancer in patients with brain metastases originating from breast cancer. The safety profile of efaproxiral and improved survival rates make this agent advantageous over radiation alone. Further investigation and results from the ongoing clinical trials will help to define the role of efaproxiral in clinical practice.

Efaproxiral is the first synthetic allosteric modifier to demonstrate significant improvement in survival in patients undergoing radiation therapy for brain metastases of breast cancer. Validation of this effect in ongoing clinical trials will be important in determining the role of efaproxiral in brain metastases from breast cancer.