Atossa Therapeutics Releases Promising Preliminary Analysis Demonstrating (Z)-Endoxifen’s Potential to Rapidly Reduce Ki-67 and Tumor Volume in ER+/HER2- Breast Cancer

Welcome to this explainer video. My name is Dr. Steven Quay, and I am Chairman and CEO of Atossa, a public company trading on the NASDAQ stock exchange under the ticker symbol ATOS.

This video accompanies an Atossa press release this morning entitled *Atossa Therapeutics Releases Promising Preliminary Analysis Demonstrating Z-Endoxifen’s Potential to Reduce Ki-67 and Tumor Volume in ER-Positive, HER2-Negative Breast Cancer.* I’m going to be making forward-looking statements here, and you should examine all of our filings with the SEC before making any investment decisions.

Today’s press release focuses on the use of Z-endoxifen as neoadjuvant treatment in ER-positive HER2-negative breast cancer. Neoadjuvant treatment is treatment in the window of time between diagnosis and definitive therapy. The NCCN guidelines speak to the value of neoadjuvant trials to shrink tumors, facilitate breast conservation, render inoperable tumors operable, predict response in the adjuvant setting, allow time for genetic testing and breast reconstruction planning, and permit more limited radiation therapy.

The trial design is shown on this slide. After recruitment, the patients were randomized to either aromatase inhibitors plus ovarian function suppression as the control group or 10 milligrams per day of endoxifen. Evaluations were done at four intervals during the trial. First, at baseline, there was a biopsy, an MRI, and blood work. Then at three weeks, there was another biopsy, another MRI, and repeat blood work. It is this preliminary time point that was analyzed for this press release. There was then a third evaluation point at 12 weeks with a third MRI and more blood work, and then finally at the time of definitive surgical excision, there was another MRI and some final blood work done at the end of the trial.

This slide shows the preliminary analysis at the first 3-week time point. Both Ki-67, a marker of cell growth, and functional tumor volume were greatly reduced after only 21 days of endoxifen. The reduction in Ki-67 by biopsy immunohistochemistry was 69%, while the reduction in functional tumor volume by MRI was 30%. Both of these results surprised me for occurring so rapidly.

The preliminary analysis of the adverse events showed endoxifen was well tolerated. The most common side effects were mild and included hot flashes, insomnia, and fatigue. No dose reductions or discontinuations due to treatment-related adverse events occurred.

Other ongoing studies of endoxifen are looking at higher doses in combination with Lilly’s AIPB to provide dual targeting of ER-alpha and PKC beta activity by endoxifen and CDK4/6 targeting by AAPB, and then lower doses to explore mammographic breast density reduction.

In conclusion, we are very encouraged by these results and thrilled by the rapid reduction in Ki-67 and functional tumor volume. It demonstrates progress in our effort to develop Z-endoxifen as a potentially effective and tolerant neoadjuvant treatment for ER-positive HER2-negative breast cancer patients. We are honored to have these findings from the I-SPY 2 endocrine optimization pilot study of Z-endoxifen presented at the inaugural RISE UP conference, and we commend Dr. Laura Esserman and other members of the organizing committee for their focus on reimagining breast cancer prevention and treatment.

If you’d like more information about this trial and other ongoing trials at Atossa Therapeutics, please go to our website at www.atossainc.com. Thank you for your attention.