Atossa Therapeutics Phase 2 Endoxifen Breast Cancer Study Hits Primary Endpoint – Management Conducts Webinar Discussion (View Event Video!)

Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical stage biopharmaceutical company seeking to discover and develop innovative medicines in areas of significant unmet medical need with a current focus on breast cancer and COVID-19, today announced the following final data from its Phase 2 clinical study of oral Endoxifen administered in the “window of opportunity” between diagnosis of breast cancer and surgery. The study enrolled seven newly-diagnosed patients with ER+ and human epidermal growth factor receptor 2 negative (HER2-) stage 1 or 2 invasive breast cancer, requiring mastectomy or lumpectomy. Patients received the Atossa proprietary oral Endoxifen for at least 14 days from the time of diagnosis up to the day of surgery. The primary endpoint was to determine if the administration of oral Endoxifen reduces the tumor activity as measured by Ki-67. The secondary endpoints were safety and tolerability and assessment of the study drug on expression levels of both estrogen and progesterone receptors, and correlation between Ki-67 and Endoxifen levels. The Phase 2 study was conducted on behalf of Atossa by Avance Clinical, a leading Australian CRO.

• Primary Endpoint Met: Reduction in Ki-67 was achieved. Ki-67, a common measure of tumor cell activity, was reduced from an average of 25.6% at screening to 6% on the day of surgery, a 65.1% reduction. Ki-67 was reduced below 25% for all patients, which is potentially clinically meaningful because studies by others have shown that a reduction below 25% improves long term survival.

• Secondary Endpoints Were as Follows:
  • Safety and tolerability: All adverse events were mild and considered related to the study drug. There were no abnormal laboratory findings (serum chemistry, hematology, coagulation, urinalysis) and no differences in vital signs, physical examinations and ECGs. Based on these results, Endoxifen was considered safe and well tolerated in this study. No adverse events led to discontinuation of the study.
  • Other Results: Estrogen receptor expression decreased from 100% at screening to 88.6% on the day of surgery and progesterone receptor expression increased from 84.3% at screening to 92.9% on the day of surgery. No correlation between Ki-67 expression and Endoxifen levels was observed.

Atossa is evaluating a number of potential clinical benefits and potential indications for its oral Endoxifen in the window of opportunity, or neoadjuvant, setting. These may include avoidance of surgery in some patients, such as older and/or frail patients, allowing for breast conservation surgery, and use of Endoxifen in place of other neoadjuvant therapies such as chemotherapy, aromatase inhibitors and other endocrine therapies like tamoxifen.

Steven Quay, M.D., Ph.D., Atossa’s President and Chief Executive Officer

“Based on these favorable results, we are taking a number of steps to quickly advance our development of Endoxifen. We have begun the formal non-clinical toxicology program that will be needed for a New Drug Application to seek marketing approval for Endoxifen and plan to apply to the U.S. FDA for approval to conduct a clinical study here in the United States as soon as possible. We expect the next clinical study to measure pathological complete response in the neoadjuvant setting. Although there are several FDA-approved neoadjuvant therapies for breast cancers that are not estrogen receptor positive (ER+), currently there are very few approved therapies for the approximately 78% of breast cancers, which are ER+ that we believe creates a significant unmet need for our Endoxifen,” stated Steven Quay, M.D., Ph.D., Atossa’s President and Chief Executive Officer.