Atossa Therapeutics Announces Phase 2 Study Contract for Oral Endoxifen to Reduce Mammographic Breast Density in Women

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Atossa Therapeutics Announces Phase 2 Study Contract for Oral Endoxifen to Reduce Mammographic Breast Density in Women

SEATTLE, Dec. 19, 2019 (GLOBE NEWSWIRE) — Atossa Therapeutics Inc. (Nasdaq:ATOS), a clinical-stage biopharmaceutical company developing novel therapeutics and delivery methods for breast cancer and other breast conditions, today announced that it has contracted with Stockholm South General Hospital in Sweden to conduct a Phase 2 study of Atossa’s proprietary oral Endoxifen to reduce mammographic breast density (MBD) in women. The study is being led by principal investigator Per Hall, M.D., Ph.D., Head of the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet. MBD is an emerging public health issue, as studies conducted by others have shown that MBD increases the risk of developing breast cancer and that reducing MBD can reduce the incidence of breast cancer.

“Atossa’s primary strategic objective is to develop oral Endoxifen to reduce MBD and this Phase 2 study is a major milestone in advancing this objective,” commented Steve Quay, M.D., Ph.D., President and CEO of Atossa. “Dr. Hall and his clinic are uniquely qualified to lead this study as they recently successfully completed the Phase 2 study of our topical Endoxifen, which demonstrated MBD reduction and they have conducted numerous studies using tamoxifen in both the treatment and prevention setting.”

The primary endpoint of the new Phase 2 study is to determine whether oral Endoxifen administration results in an individual change in MBD, which will be measured after three and six months of treatment. The secondary endpoints are safety and tolerability. Assuming the institutional review board (IRB) approves the study, enrollment is expected to open in the first quarter of 2020.

Significant progress has been made with Atossa’s lead Endoxifen program:

  • Atossa has completed multiple Phase 1 clinical studies using both a topical and oral (capsule and modified-release tablet) formulations of Endoxifen, the results of which indicated that oral Endoxifen was safe and well tolerated.
  • Atossa’s recently completed Phase 2 study of topical Endoxifen found that, despite study participants reporting skin rashes and irritation, a statistically significant reduction in MBD was achieved in women taking the higher dose form of topical Endoxifen in as little as three months of dosing.
  • In an FDA-approved, single patient, expanded access (or “compassionate use”) study, a breast cancer patient receiving Atossa’s oral Endoxifen experienced a significant reduction in cancer cell biological activity – the Ki-67 activity decreased by 50 percent, and the estrogen receptor content decreased by over 20 percent.

Atossa’s Proprietary Endoxifen

Endoxifen is an active metabolite of tamoxifen. Tamoxifen is an FDA-approved drug to prevent new breast cancer as well as recurrent breast cancer in breast cancer patients. Tamoxifen itself must be broken down by the liver into active compounds (metabolites), of which Endoxifen is the most active. Although oral tamoxifen is approved to prevent breast cancer in “high-risk” women, it is used by less than 5 percent of women with an increased risk of developing breast cancer, including women with MBD, because of the actual or perceived side effects and risks of tamoxifen.

Mammographic Breast Density (MBD)

Legislation has been recently enacted in over 35 states requiring that women be notified if they have MBD and those notifications typically state that women with MBD have a higher risk of developing breast cancer, and that mammography may not be as effective in detecting breast cancer because the MBD can “mask” the detection of cancers. In February 2019, Federal legislation was enacted that requires that the FDA adopt rules requiring that mammography reports include information about MBD and inform women about their MBD status. There is no FDA-approved treatment for MBD.

MBD has been shown in studies conducted by others to be an independent risk factor for developing breast cancer. It is estimated that approximately ten million women in the Unites States have MBD. Atossa Therapeutics believes its Endoxifen may provide an option for women to proactively reduce the mammographic density of their breasts. Moreover, the company’s Endoxifen may improve mammography accuracy and patient care by unmasking cancerous tumors that are otherwise obscured by high breast density.

Based on the number of women with MBD and the number of patients who have survived breast cancer but are not fully benefiting from taking tamoxifen, Atossa estimates that the potential markets for its proprietary formulations of Endoxifen could potentially exceed $1 billion in annual sales. Moreover, reducing the incidence of breast cancer could significantly reduce healthcare costs.

About Atossa Therapeutics

Atossa Therapeutics Inc. is a clinical-stage biopharmaceutical company developing novel therapeutics and delivery methods to treat breast cancer and other breast conditions. For more information, please visit

Forward-Looking Statements

Forward-looking statements in this press release, which Atossa undertakes no obligation to update, are subject to risks and uncertainties that may cause actual results to differ materially from the anticipated or estimated future results, including the risks and uncertainties associated with any variation between preliminary and final clinical results, actions and inactions by the FDA, the outcome or timing of regulatory approvals needed by Atossa including those needed to commence studies, lower than anticipated rate of patient enrollment, estimated market size of drugs under development, the safety and efficacy of Atossa’s products and services, performance of clinical research organizations and investigators, obstacles resulting from proprietary rights held by others with respect to fulvestrant, such as patent rights, potential market sizes for Atossa’s drugs under development and other risks detailed from time to time in Atossa’s filings with the Securities and Exchange Commission, including without limitation its periodic reports on Form 10-K and 10-Q, each as amended and supplemented from time to time.

Atossa Therapeutics Company Contact

Atossa Therapeutics Inc.
Kyle Guse
CFO and General Counsel
Office: 800-351-3902

Investor Relations Contact:

Scott Gordon
377 Oak Street
Concourse 2
Garden City, NY 11530
Office: 516.222.2560

Dec 19, 2019