Allos Therapeutics, Inc informed that it has received an approvable letter from the US Food and Drug Administration (FDA) for its New Drug Application (NDA) for RSR13 (efaproxiral) for the treatment of patients with brain metastases originating from breast cancer.

In the letter, the FDA indicated that before the NDA may be approved, it would be necessary for Allos to complete its ongoing Phase III clinical trial of RSR13 in patients with brain metastases originating from breast cancer and submit the results as an NDA amendment for the FDA's review. "If the study shows effectiveness in this population (increased survival) using the pre-specified analysis, and the study is otherwise satisfactory, we believe it would, together with the subset result in RT-009, support approval," the FDA stated in the letter.

The ongoing Phase III trial, called ENRICH (Enhancing Whole Brain Radiation Therapy In Patients with Breast Cancer and Hypoxic Brain Metastases), will seek to enroll approximately 360 patients at up to 50 cancer centers across North America.

However, the FDA indicated that additional general comments from Clinical Pharmacology/Toxicology and Chemistry would be forwarded separately. The FDA also noted that it has not completed its inspection of the manufacturing and controls facilities listed in the NDA, which remains a prerequisite to approval of the NDA.

"We are pleased that the FDA has determined that RSR13 is approvable, assuming a favorable outcome of our ENRICH study," said Michael Hart, president and chief executive officer of Allos. "We remain focused on completing the enrollment of the ENRICH study as soon as possible, and will continue to work with the FDA with the goal of advancing RSR13 toward approval," he added.

RSR13 (efaproxiral) is the first synthetic small molecule designed to sensitize hypoxic, or oxygen-deprived, areas of tumors prior to radiation therapy by facilitating the release of oxygen from hemoglobin, the oxygen-carrying protein contained within red blood cells, and increasing the level of oxygen in tumors.

Allos Therapeutics, Inc. is a biopharmaceutical company focused on developing drugs for improving cancer treatments.