Programs

Well-positioned across the treatment paradigm

(Z)-endoxifen

Breast-Cancer-sentinel-lymphnodeMetastatic Breast Cancer – A Persistent Unmet Need

(Z)-endoxifen’s potent anti‐estrogen activity has been validated in both Phase 1 and Phase 2 settings, demonstrating clear advantages over tamoxifen in patients with advanced, ER-positive disease:

Superior Progression-Free Survival in Front-Line Patients
In CDK4/6 inhibitor–naïve metastatic patients, (Z)-endoxifen more than doubled median PFS compared to tamoxifen (7.2 vs. 2.4 months), underscoring its enhanced efficacy in an endocrine-sensitive population.

Meaningful Benefit After Tamoxifen Failure
Patients who progressed on tamoxifen and then crossed over to (Z)-endoxifen achieved notable clinical benefit—ranging from partial tumor responses to prolonged stable disease. A subset of these heavily pretreated individuals maintained disease control for more than 2–3 years, highlighting (Z)-endoxifen’s ability to overcome resistance.

These data from early‐stage trials reinforce (Z)-endoxifen as a next-generation SERM with the potential to redefine standards of care in metastatic breast cancer.

Atossa is actively engaged in discussions with the U.S. Food and Drug Administration to define the optimal regulatory pathway for advancing our metastatic breast cancer indication. We expect to share additional details and program milestones as these conversations progress, with updates to follow throughout 2026.

woman having mammogramAdjuvant Therapy: Exploring Earlier-Stage Intervention

Many patients in the adjuvant setting either do not respond to tamoxifen or cannot tolerate aromatase inhibitors, leaving a significant unmet need for safer, more effective options. (Z)-endoxifen’s direct active-form delivery offers the potential for:

  • Consistent Drug Exposure: Bypassing hepatic metabolism ensures reliable systemic levels across diverse patient populations.
  • Enhanced Safety & Tolerability: Early data suggest a lower incidence of common SERM-related side effects—such as hot flashes and thromboembolic risk—potentially reducing treatment discontinuations.

Atossa is actively engaging with the U.S. Food and Drug Administration to define a streamlined regulatory pathway for adjuvant breast cancer—and other earlier-stage—indications. We look forward to sharing updates on our discussions and development plans throughout 2026.

Prime the Fight: Tumor Reduction Before Surgery

There is a clear unmet need for safer, more efficacious neoadjuvant therapies. Early data suggest (Z)-endoxifen may effectively reduce tumor proliferation, potentially leading to improved surgical outcomes.

EVANGELINE trial: In an ongoing neoadjuvant clinical study, (Z)-endoxifen has demonstrated promising early efficacy with 1 complete and multiple partial responses.

  • Readout: 40 and 80 mg data presented at SABCS 2023 and 2024, respectively.
  • The 4-week Ki-67 ≤10% response rate was generally above 85% across dose levels, with or without the presence of OFS.
  • Endocrine therapies are generally observed to be cytostatic and do not cause tumor shrinkage.

The I-SPY2 trial: Monotherapy and combination therapy with abemaciclib
(In collaboration with Quantum Leap Healthcare Collaborative)

  • (Z)-endoxifen monotherapy at 10 mg once daily met the primary endpoint with 95% of patients receiving greater than 75 % of planned treatment with promising rapid activity in reducing 3-wk Ki-67 and functional tumor volume (FTV) at 69% and 30%, respectively.
  • (Z)-endoxifen combination data expected 2026.

Stop Cancer Before It Starts: Proactive Risk Reduction

Prior studies have shown the potential to reduce key risk factors such as breast tissue density and estrogen receptor activity.

The KARISMA Trial

  • (Z)-endoxifen has demonstrated 1 mg dose of (Z)-endoxifen reduced MBD by 19 percentage points (p<0.01), compared to a minimal change in the placebo group of 0.27 percentage points.
  • Plasma concentrations for (Z)-endoxifen were measured at 4.8 ng/mL for the 1 mg, highlighting the effectiveness of the lower dose in achieving significant reductions.
  • Importantly, no significant differences in adverse events were observed between the 1 mg dose and placebo

Expanded Access Policy: Purpose & Philosophy

Atossa Therapeutics is a clinical-stage biopharmaceutical company developing novel, proprietary therapeutics and delivery methods for breast cancer and other breast conditions.

Atossa Therapeutics’ development resources are focused on conducting clinical studies to fully answer important scientific questions about the potential risks and benefits of the investigational products, and to obtain marketing approval by the FDA and other regulatory health authorities.

Atossa Therapeutics is committed to making investigational products available to seriously ill patients who have exhausted other treatment options. A treating physician, who is able to comply with the requirements that are stated in this document, may request information about how to apply for access to Atossa Therapeutics’ investigational products by contacting the Company.

The purpose of this policy is to describe the requirements for Expanded Access to Atossa Therapeutics investigational products to patients outside of a clinical study. To read our full expanded access policy CLICK HERE.