Allos Therapeutics Inc., a biopharmaceutical company focused on developing and commercializing innovative drugs for improving cancer treatments, announced the presentation of positive findings from its Phase 3 clinical trial of the investigational radiation sensitizer RSR13 (efaproxiral). The results demonstrate a significant survival benefit for women with breast cancer and brain metastases who received RSR13 plus whole brain radiation therapy (WBRT) versus WBRT alone. Baldassarre Stea, MD, PhD, head of the department of radiation oncology at the Arizona Health Sciences Center in Tucson, presented the findings at the 26th Annual San Antonio Breast Cancer Symposium.
In poster number 175, entitled "Results from a subgroup analysis of patients with metastatic breast cancer (MBC) in a phase 3, randomized, open-label, comparative study of standard whole brain radiation therapy (WBRT) with supplemental-oxygen, with or without RSR13, in patients with brain metastases," Dr Stea and colleagues showed that adding RSR13 to WBRT with supplemental oxygen nearly doubled the median survival rate of patients with breast cancer and brain metastases to 8.67 months versus 4.57 months for patients who received WBRT alone (p=0.006). Patients with breast cancer and brain metastases who were treated with RSR13 plus WBRT also achieved a higher response rate in the brain than the control group (71.7 per cent vs. 49.1 per cent; p=0.02). A statistically significant stable or improvement in quality of life at 3 months was observed in patients receiving RSR13, as assessed by the Karnofsky Performance Score (35 per cent vs. 18 per cent; p=0.001) and the Spitzer Index (37 per cent vs. 24 per cent; p=0.01). In general, patients experienced minimal serious adverse events with the most common being hypoxemia (3.4 per cent n=266), which is dose-dependent and effectively managed with supplemental oxygen.
"The presentation of survival and quality of life data at this meeting validates the potential of RSR13 to increase the effectiveness of radiation therapy in breast cancer patients with brain metastases," said Michael E. Hart, president and CEO of Allos Therapeutics, Inc. "Brain metastases are devastating to patients and new therapies are desperately needed."
"You would expect patients with higher response rates in the brain to live longer and that's exactly what we saw in breast cancer patients," said Dr. Stea. "Additional analyses of the data set continue to deliver encouraging news regarding the potential benefits of using RSR13 with whole brain radiation therapy in patients with metastatic breast cancer. These data suggest that RSR13 has a positive treatment effect on survival and quality of life in patients struggling with breast cancer and brain metastases, providing added hope in their fight against cancer."
The preliminary results from the 538-patient randomized Phase 3 trial of RSR13 were announced in April 2003. The results did not meet the primary survival endpoint of the study using standard log rank analysis. In the overall study population, patients receiving RSR13/WBRT experienced a 17.6 per cent improvement in median survival compared to patients receiving WBRT alone (5.26 months vs. 4.47 months; p=0.17; n=538). However, the survival benefit for RSR13 was statistically significant in a pre-specified Cox multiple regression model (Hazard Ratio 0.775 [95 per cent, 0.941], p=0.010). The company is currently submitting a rolling New Drug Application (NDA) for RSR13 as an adjunct to WBRT for the treatment of brain metastases originating from breast cancer to the US Food and Drug Administration (FDA). The FDA granted Fast Track Product designation for RSR13 in November 2000. The company expects to complete its rolling NDA submission this month.