Atossa Therapeutics, Inc. (Nasdaq: ATOS) ("Atossa" or the "Company"), a clinical-stage biopharmaceutical company developing innovative medicines for breast cancer, today released positive topline data from the KARISMA-Endoxifen Phase 2 study of (Z)-endoxifen in premenopausal women with mammographic breast density (MBD). The study, which was conducted through the Karolinska Institute in Stockholm, Sweden, demonstrated that low doses of (Z)-endoxifen significantly reduced MBD and was generally well tolerated. A video summary of the results can be found here.

Study Highlights:

• The Atossa sponsored ATOS-016R prevention trial included healthy women, randomized to daily placebo and 1 and 2 mg of (Z)-endoxifen. There were 80 women in each study arm and the study lasted six months.

• Mammographic breast density decrease was used as a proxy for therapy response. Measurements at six months or early terminations were compared to baseline density.

• No important differences in age, BMI or other background factors between randomization arms were seen.

• The relative significant density change was -19.3 percent and -26.5 percent for the 1 and 2 mg arms, respectively, using the placebo arm as a reference. No significant difference was seen comparing the 1 and 2 mg arms.

o In a 2011 study, women with a breast density decrease of 10 percent or greater after taking tamoxifen for one year had a 62 percent reduction in breast cancer incidence after 5 years.

• No changes in hematological safety tests or vital signs were noted during the trial period.

• The mean endoxifen plasma concentration was 5.18 ng/mL in the 1 mg arm and 10.87 ng/mL in the 2 mg arm after one month of therapy. Plasma concentrations stayed the same at three and six months.

• The number of women that discontinued the study because of side effects related to the drug were 4, 5 and 12 in the placebo, 1 and 2 mg arms, respectively. Vasomotor symptoms were not reported as a reason for discontinuation.

• A validated questionnaire including 36 questions, and a five-graded Likert scale was used for self-assessment of symptoms. Only vasomotor symptoms (night and cold sweats and hot flushes) increased during the study period in the active arms, but not substantially: mean = 1.4 on a 10-point scale.

Nearly 50 percent of women receiving mammograms in the United States have dense breasts. While common and not considered abnormal, dense breasts make it harder to see tumors on mammograms and are an independent risk factor for developing breast cancer.

“We are thrilled with the topline results from the KARISMA-Endoxifen Phase 2 trial with (Z)-endoxifen and heartened by the idea that this work may someday lead us to a preventative approach to breast cancer,” said Dr. Steven Quay, Chief Executive Officer of Atossa Therapeutics. “Although further analysis of this study is required, the potential that 1 mg of (Z)-endoxifen may significantly reduce breast density as well as, if not better than currently available therapies, potentially without many of the intolerable side effects, is extremely encouraging and a significant step toward a solution for millions of women with dense breasts.”

Atossa and the Karolinska Institute expect to report detailed results from the KARISMA-Endoxifen trial at the San Antonio Breast Cancer Symposium in December, followed by full publication of the results in a peer-reviewed journal next year.

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