Atossa Therapeutics Announces Full Enrollment of (Z)-Endoxifen Arm of I-SPY 2 Clinical Trial

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Atossa Therapeutics, Inc. (Nasdaq: ATOS) has fully enrolled the (Z)-endoxifen arm of the Phase 2 I-SPY 2 clinical trial, evaluating it as a neoadjuvant treatment for newly diagnosed estrogen receptor-positive invasive breast cancer. The study aims to down-stage the tumor, improve tumor resectability, and reduce breast cancer recurrence. The company looks forward to seeing data from this study in the second half of 2024. The (Z)-endoxifen arm enrolled 20 patients as part of the I-SPY 2 Endocrine Optimization Pilot Protocol (EOP).
  • Full enrollment of the (Z)-endoxifen arm of the Phase 2 I-SPY 2 clinical trial
  • The potential of (Z)-endoxifen to improve treatment for estrogen receptor-positive breast cancer patients
  • None.

From a clinical perspective, the full enrollment in the Phase 2 I-SPY 2 clinical trial for Atossa Therapeutics' (Z)-endoxifen is a significant milestone. This development is crucial because it marks the progression of a potential new neoadjuvant therapy for estrogen receptor-positive (ER+) invasive breast cancer, which is a prevalent subtype of breast cancer. The ability of (Z)-endoxifen to down-stage tumors could be transformative, potentially enabling less extensive surgery and reducing the risk of recurrence. This is particularly important given the limitations of current neoadjuvant options such as aromatase inhibitors and systemic chemotherapy, which can have challenging side effects. The safety and tolerability profile of (Z)-endoxifen will be a key factor in its adoption, should clinical outcomes prove favorable.

From a research analysis standpoint, the announcement by Atossa Therapeutics signifies the transition from patient recruitment to data collection and analysis in the I-SPY 2 trial. The trial's design, which includes collaboration with notable cancer research centers and regulatory bodies, adds credibility to the study and may expedite the review process if results are positive. The focus on a Selective Estrogen Receptor Modulator (SERM) like (Z)-endoxifen is noteworthy, as SERMs are designed to either block or activate estrogen receptors in a tissue-selective manner. This mechanism could offer a targeted approach to treatment with fewer side effects than traditional therapies. The outcome of this study will be closely watched as it could impact treatment protocols and the competitive landscape of breast cancer therapies.

Analyzing the financial implications, Atossa Therapeutics' announcement may have a positive impact on investor sentiment, given the potential market size for ER+ breast cancer treatments. The successful completion of the Phase 2 trial enrollment indicates that the company is advancing on its clinical development timeline, which is a positive signal for investors. Future trial results will be a pivotal factor in the company's valuation. If (Z)-endoxifen demonstrates clinical efficacy and safety, it could lead to significant market penetration given the high prevalence of ER+ breast cancer. However, investors should also consider the inherent risks of clinical trials, as any negative outcomes could adversely affect the company's stock. The long-term financial outlook will be contingent upon trial outcomes, regulatory approvals and the ability to commercialize the treatment effectively.

SEATTLE, Feb. 07, 2024 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical stage biopharmaceutical company developing innovative medicines in areas of significant unmet medical need in oncology with a focus on breast cancer, today announced that the (Z)-endoxifen arm of the ongoing Phase 2 I-SPY 2 clinical trial has fully enrolled. In the study, (Z)-endoxifen, Atossa’s proprietary Selective Estrogen Receptor Modulator (SERM), is being evaluated as a neoadjuvant treatment for newly diagnosed estrogen receptor-positive (ER+) invasive breast cancer.

“We are excited that the (Z)-endoxifen arm of the I-SPY 2 study has fully enrolled and look forward to seeing data from this study in the second half of 2024,” said Steven Quay, MD, PhD, Atossa’s President and Chief Executive Officer. “Estrogen receptor positive breast cancer accounts for over 80% of all breast cancer diagnoses and unfortunately, the current neoadjuvant treatment options for these patients are sub-optimal. Treatment with (Z)-endoxifen has the potential to down-stage the tumor, improve tumor resectability and reduce the incidence of breast cancer recurrence, all while demonstrating a far superior safety and tolerability profile compared to aromatase inhibitors and systemic chemotherapy. This would transform the treatment paradigm for the hundreds of thousands of women diagnosed with ER-positive breast cancer every year.”

The I-SPY 2 TRIAL is a collaborative effort among academic investigators from major cancer research centers across the United States, Quantum Leap Healthcare Collaborative, the U.S. Food and Drug Administration, and the Foundation for the National Institutes of Health (FNIH) Cancer Biomarkers Consortium. The (Z)-endoxifen treatment arm, which enrolled 20 patients, is part of the I-SPY 2 Endocrine Optimization Pilot Protocol (EOP). Patients receive 10 mg of (Z)-endoxifen daily for up to 24 weeks prior to surgery.

About (Z)-Endoxifen
(Z)-endoxifen is the most active metabolite of the FDA approved Selective Estrogen Receptor Modulator (SERM), tamoxifen. Studies by others have demonstrated that the therapeutic effects of tamoxifen are driven in a concentration-dependent manner by (Z)-endoxifen. In addition to its potent anti-estrogen effects, (Z)-endoxifen at higher concentrations has been shown to target PKCβ1, a known oncogenic protein.

Atossa is developing a proprietary oral formulation of (Z)-endoxifen that does not require liver metabolism to achieve therapeutic concentrations and is encapsulated to bypass the stomach as acidic conditions in the stomach convert a greater proportion of (Z)-endoxifen to the inactive (E)-endoxifen. Atossa’s (Z)-endoxifen has been shown to be well tolerated in Phase 1 studies and in a small Phase 2 study of women with breast cancer. (Z)-endoxifen is currently being studied in four Phase 2 trials: one in healthy women with measurable breast density, one in women diagnosed with ductal carcinoma in situ, and two other studies including the EVANGELINE study in women with ER+/HER2- breast cancer. Atossa’s (Z)-endoxifen is protected by three issued U.S. patents and numerous pending patent applications.

About Atossa Therapeutics
Atossa Therapeutics, Inc. is a clinical-stage biopharmaceutical company developing innovative medicines in areas of significant unmet medical need in oncology with a focus on breast cancer. For more information, please visit

About Quantum Leap Healthcare Collaborative
Quantum Leap Healthcare Collaborative is a 501c(3) charitable organization established in 2005 as a collaboration between medical researchers at University of California, San Francisco and Silicon Valley entrepreneurs. Our mission is to integrate care and research, and to foster high-impact trials with embedded clinical processes and systems technology and improved data management, greater access to clinical trial matching, and greater benefit to patients, providers, and researchers. Our goal is to improve and save lives. Quantum Leap provides operational, financial, and regulatory oversight to I-SPY. For more information, visit

About the I-SPY TRIALs
The I-SPY TRIAL (Investigation of Serial studies to Predict Your Therapeutic Response with Imaging And moLecular analysis 2) (I-SPY 2 TRIAL) was designed to rapidly screen promising experimental treatments and identify those most effective in specific patient subgroups based on molecular characteristics (biomarker signatures). The Endocrine Optimization Pilot (EOP) is developing better endpoints and new endocrine targeted agents for stage 2/3 molecularly low risk breast cancer. The trial is a unique collaborative effort by a consortium that includes the Food and Drug Administration (FDA), industry, patient advocates, philanthropic sponsors, and clinicians from 30 major U.S. cancer research centers. Under the terms of the collaboration agreement, Quantum Leap Healthcare Collaborative is the trial sponsor and manages all study operations. For more information, visit

Atossa Therapeutics Contact:
Eric Van Zanten
VP, Investor and Public Relations

This press release contains certain information that may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. We may identify these forward-looking statements by the use of words such as “expect,” “potential,” “continue,” “may,” “will,” “should,” “could,” “would,” “seek,” “intend,” “plan,” “estimate,” “anticipate,” “believe,” “future,” or other comparable words. Forward-looking statements in this press release are subject to risks and uncertainties that may cause actual results, outcomes, or the timing of actual results or outcomes, to differ materially from those projected or anticipated, including risks and uncertainties associated with: macroeconomic conditions and increasing geopolitical instability; the expected timing of releasing data; any variation between interim and final clinical results; actions and inactions by the FDA and foreign regulatory bodies; the outcome or timing of regulatory approvals needed by Atossa, including those needed to continue our planned (Z)-endoxifen trials; our ability to satisfy regulatory requirements; our ability to regain compliance with the continued listing requirements of the Nasdaq Stock Market; our ability to successfully develop and commercialize new therapeutics; the success, costs and timing of our development activities, including our ability to successfully initiate or complete our clinical trials, including our (Z)-endoxifen trials; our anticipated rate of patient enrollment; our ability to contract with third-parties and their ability to perform adequately; our estimates on the size and characteristics of our potential markets; our ability to successfully defend litigation and other similar complaints and to establish and maintain intellectual property rights covering our products; whether we can successfully complete our clinical trial of oral (Z)-endoxifen in women with mammographic breast density and our trials of (Z)-endoxifen in women with breast cancer, and whether the studies will meet their objectives; our expectations as to future financial performance, expense levels and capital sources, including our ability to raise capital; our ability to attract and retain key personnel; our anticipated working capital needs and expectations around the sufficiency of our cash reserves; and other risks and uncertainties detailed from time to time in Atossa’s filings with the Securities and Exchange Commission, including without limitation its Annual Reports on Form 10-K and Quarterly Reports on 10-Q. Forward-looking statements are presented as of the date of this press release. Except as required by law, we do not intend to update any forward-looking statements, whether as a result of new information, future events or circumstances or otherwise.

The ticker symbol for Atossa Therapeutics, Inc. is ATOS.

The Phase 2 I-SPY 2 clinical trial is focusing on evaluating (Z)-endoxifen as a neoadjuvant treatment for newly diagnosed estrogen receptor-positive invasive breast cancer.

The goal is to down-stage the tumor, improve tumor resectability, and reduce the incidence of breast cancer recurrence for patients with estrogen receptor-positive breast cancer.

20 patients were enrolled in the (Z)-endoxifen treatment arm as part of the I-SPY 2 Endocrine Optimization Pilot Protocol (EOP).

Steven Quay, MD, PhD is the President and Chief Executive Officer of Atossa Therapeutics, Inc.
Atossa Therapeutics Inc


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About ATOS

atossa therapeutics, inc. develops and markets medical devices, laboratory tests, and therapeutics to address breast health conditions in the united states. the company's lead program is the development of endoxifen, an active metabolite of tamoxifen which is in phase ii studies to treat and prevent breast cancer. it is also developing intraductal microcatheter technology to target the delivery of therapies, including fulvestrant, immunotherapies, and chimeric antigen receptor t-cell therapies, directly to the site of breast cancer. the company was formerly known as atossa genetics inc. and changed its name to atossa therapeutics, inc. in january 2020. atossa therapeutics, inc. was founded in 2009 and is headquartered in seattle, washington.