Atossa Therapeutics Reveals Final Endoxifen Data From Mid-Stage Breast Cancer Trial

Atossa Therapeutics Inc ATOS has announced final data from its Phase 2 study of oral Endoxifen administered between the 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 oral Endoxifen for at least 14 days from the time of diagnosis up to the day of surgery.
Results showed a 65.1% reduction in Ki-67, a measure of tumor cell activity, from an average of 25.6% at the screening to 6% on the day of surgery.
Ki-67 was reduced below 25% for all patients, potentially clinically meaningful because studies by others have shown that a reduction below 25% improves long-term survival.
All adverse events were mild and considered related to the study drug.
No abnormal laboratory findings and no differences in vital signs, physical examinations, and ECGs were observed.
Estrogen receptor expression decreased from 100% at the screening to 88.6% on the day of surgery, and progesterone receptor expression increased from 84.3% at the screening to 92.9% on the day of surgery.
No correlation between Ki-67 expression and Endoxifen levels was observed.
Price Action: ATOS shares are down 26.9% at $4.44 during the market session on the last check Wednesday.