Atossa Therapeutics Highlights Progress in RECAST™ DCIS Platform Trial at Early Detection Research Conference; Laura Esserman, MD, MBA, to Discuss Active-Surveillance Strategy and Novel Endocrine Agents

Rhea-AI Summary

Atossa Therapeutics (Nasdaq: ATOS) highlighted enrollment progress and biomarker strategy for the RECAST™ Phase 2 DCIS platform trial ahead of an Early Detection Research Conference presentation on October 21, 2025.

RECAST is a multi-arm, randomized neoadjuvant trial testing standard endocrine therapy and novel agents—(Z)-Endoxifen, elacestrant, Hav-088—with imaging, biomarker discovery, and quality-of-life endpoints. Enrollment began January 2024 with 50 of 400 patients enrolled across 17 active U.S. sites. The trial aims to identify patients suitable for long-term active surveillance and generate interim imaging and biomarker readouts to de-risk later-stage development.

Positive

• Platform design enables parallel testing of multiple agents
• Enrollment started Jan 2024: 50 patients enrolled
• 17 active U.S. clinical sites activated

Negative

• Enrollment at 50/400 (12.5% of target) may slow timelines
• No disclosed interim data or definitive biomarker readouts yet

Insights

Clinical Trials & Strategic Development Analyst

RECAST platform shows early enrollment and biomarker-driven design; interim imaging and biomarker readouts are the main near-term milestones.

The program uses a multi-arm, randomized Phase 2 platform to test whether endocrine agents, including (Z)-Endoxifen, can expand eligibility for active surveillance in hormone receptor–positive DCIS. The design ties comparative imaging (mammography and MRI), biomarker discovery, and quality-of-life measures to generate signal-level evidence across control and experimental arms, which can inform registration and payer conversations without yet relying on long-term invasive‑cancer outcomes.

Key dependencies and risks include slow enrollment relative to the 400 patient target (currently 50 enrolled across 17 sites), the quality and reproducibility of interim imaging and biomarker signals to correlate with progression risk at six months, and reliance on shared infrastructure and external sponsors for site activation. The trial’s ability to produce decision-grade biomarkers and clear imaging endpoints will determine whether it meaningfully de-risks later stages.

Concrete items to watch: enrollment progress toward the 400 patient target, any announced interim imaging or biomarker readouts, and measures of active‑surveillance suitability by arm over the coming quarters. Near-term time horizon: the next several quarters for interim signals and site activations; the six‑month risk‑correlation objective is a specific milestone to monitor.

Investor-focused update underscores enrollment momentum, biomarker strategy, and near-term data readouts designed to de-risk development of (Z)-Endoxifen and other endocrine therapies for DCIS

SEATTLE, Oct. 21, 2025 /PRNewswire/ -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) ("Atossa" or the "Company"), a clinical-stage biopharmaceutical company developing innovative medicines in oncology, today announced that Laura J. Esserman, MD, MBA, Professor of Surgery and Radiology at the University of California, San Francisco and Principal Investigator of RECAST™, will speak at the Early Detection Research Conference in Portland, OR, about the Company's collaborative work in the RECAST platform trial for ductal carcinoma in situ (DCIS), a biologically heterogeneous, non-invasive breast condition that can progress to invasive breast cancer in a subset of patients.

RECAST is a multi-arm, Phase 2, randomized, neoadjuvant platform trial designed to identify which patients with hormone receptor–positive DCIS are best suited for active surveillance and to determine whether novel endocrine therapies can expand the population that can safely avoid surgery. The trial includes arms evaluating standard therapy (tamoxifen or aromatase inhibitor) as well as novel agents: (Z)-Endoxifen, elacestrant, and Hav-088. Efficacy is assessed with mammography and breast MRI, alongside biomarker discovery and quality-of-life endpoints. Enrollment began in January 2024; 50 patients have been enrolled toward a target of 400 across 17 activated clinical sites, with additional sites planned.

Why this matters for investors

• Large, under-served market: DCIS is commonly treated like invasive cancer (surgery ± radiation ± endocrine therapy). Demonstrating that a biomarker-guided, non-surgical approach is safe and effective could reshape standard of care and expand use of oral endocrine agents in early-stage disease management.
• Efficient signal-finding: The platform design enables parallel testing of multiple agents, including Atossa's (Z)-Endoxifen, with common imaging and biomarker endpoints to generate comparative signals that can inform registration strategies.
• Multiple potential catalysts: Early imaging response, biomarker correlation, and active-surveillance suitability rates by arm create interim readout opportunities that can de-risk later-stage programs and guide payer-relevant health-economic modeling.
• Strategic collaborations: RECAST is sponsored by Quantum Leap Healthcare Collaborative with research support from NIH and industry partners. This shared-infrastructure model can accelerate enrollment, broaden site access, and optimize capital efficiency.

"RECAST is purpose-built to answer the question that payers, physicians, and patients care most about: who truly needs surgery and who does not," said Steven Quay, MD, PhD, Chairman and CEO of Atossa Therapeutics. "For Atossa, the trial offers a capital-efficient path to demonstrate the potential of (Z)-Endoxifen in a large early-disease setting, generate decision-grade biomarkers, and position us for value-creating milestones over the coming quarters."

RECAST Trial Objectives

1. Increase the fraction of DCIS patients suitable for long-term active surveillance using novel endocrine therapy.
2. Correlate risk of progression to invasive ductal carcinoma with risk categorization after six months of therapy.
3. Identify biomarkers that predict response and elucidate mechanisms of imaging response and resistance.
4. Assess quality of life compared with standard endocrine therapy.

Current Trial Status

• Phase: 2 (platform)
• Population: HR-positive DCIS (any grade)
• Arms: Tamoxifen/AI (control), (Z)-Endoxifen, elacestrant, Hav-088
• Assessments: Mammogram, MRI, biomarker panels, QoL
• Enrollment: 50/400; 17 active U.S. sites; additional site activations planned.

About Atossa Therapeutics

Atossa Therapeutics, Inc. (Nasdaq: ATOS) is a clinical-stage biopharmaceutical company developing novel therapies in oncology, including (Z)-Endoxifen, to improve outcomes for patients across the breast cancer continuum of care. Information about Atossa can be found at the website: https://atossatherapeutics.com/. Information about the conference can be found here: https://www.earlydetectionresearch.com/

Forward-Looking Statements

This press release contains forward-looking statements, including statements regarding the design, conduct, timing, and potential impact of the RECAST trial; the development, safety, and efficacy of (Z)-Endoxifen and other endocrine therapies; potential changes to standards of care; anticipated milestones, data readouts, regulatory interactions, and market opportunities; and the benefits of collaborative platform trials. These statements are subject to risks and uncertainties that could cause actual results to differ materially, including those described in Atossa's filings with the SEC. Atossa undertakes no obligation to update forward-looking statements except as required by law.

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SOURCE Atossa Therapeutics Inc

FAQ

What is the RECAST Phase 2 trial Atossa is participating in (ATOS)?

RECAST is a multi-arm Phase 2 neoadjuvant platform trial testing standard endocrine therapy and novel agents including (Z)-Endoxifen, elacestrant, and Hav-088 in HR-positive DCIS.

How many patients has Atossa enrolled in RECAST as of Oct 21, 2025?

Enrollment is 50 of a 400-patient target across 17 active U.S. sites with additional site activations planned.

What endpoints will RECAST use to assess (Z)-Endoxifen in DCIS?

Efficacy is assessed by mammography and breast MRI, alongside biomarker discovery and quality-of-life endpoints.

What investor catalysts does Atossa expect from the RECAST trial (ATOS)?

Potential catalysts include early imaging responses, biomarker correlations, and active-surveillance suitability readouts that could de-risk later programs.

Who sponsors the RECAST platform trial mentioned by Atossa?

RECAST is sponsored by Quantum Leap Healthcare Collaborative with research support from NIH and industry partners.