Endoxifen Shows Promise in Treating Breast Cancer in Australian Trial, Development in the US to Accelerate


Results of a trial assessing endoxifen in patients with breast cancer in Australia were positive enough for the manufacturer to stop the trial before it was scheduled to be completed. The drug’s manufacturer will now accelerate its development in the U.S.

Treatment with oral endoxifen during the “window of opportunity” between breast cancer diagnosis and surgery induced a significant reduction in tumor activity among the first six patients enrolled on a phase 2 trial in Australia, according to the drug’s manufacturer, Atossa Therapeutics.

Moreover, the positive results were so significant that the manufacturer decided to stop the trial before its scheduled completion and says it plans to accelerate the drug’s development in the United States.

“It is a welcome event to halt an ongoing clinical trial because the results are so overwhelmingly positive,” Atossa’s President and CEO Dr. Steven Quay, said in a company-issued press release.

“Data from the first six patients in our Australian phase 2 window of opportunity study shows a 74% average reduction in Ki-67, which is a common measure of tumor cell activity, and that at the time of surgery all patients had Ki-67 levels lower than 25%, which is an important threshold to improve long-term survival as identified in studies by others. We believe that additional enrollment will not alter these positive results, so we are terminating the study early. This saves at least a year on the development timeline allowing us to accelerate clinical development in the Unites States.”

Seven patients with newly diagnosed ER-positive and HER2-negative stage 1 or 2 invasive breast cancer who required mastectomy or lumpectomy were enrolled on the trial. Measuring the reduction of anti-tumor activity via decrease in the Ki-67 protein was the main goal of the study. Other secondary goals of the study were to assess the drug’s safety and tolerability.

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