#USA #Seattle #FDA Approval #Atossa Therapeutics #(Z)-endoxifen

Atossa Therapeutics Advances Towards IND Submission

Atossa Therapeutics, Inc. (NASDAQ: ATOS), a clinical-stage biopharmaceutical firm focusing on innovative cancer therapies, has made headlines recently with promising feedback from the U.S. Food and Drug Administration (FDA) regarding its (Z)-endoxifen program. This compound is under investigation for treating estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer, a condition in dire need of effective treatment options.

On July 29, 2025, Atossa announced that the FDA offered constructive written responses concerning its proposed dose optimization trial for (Z)-endoxifen. This positive feedback is expected to significantly streamline the path toward the upcoming Investigational New Drug (IND) submission planned for the fourth quarter of 2025. Notably, the FDA's responses preempted the need for a virtual meeting, signaling a collaborative spirit from the regulatory body and confidence in Atossa's clinical development strategy.

Dr. Steven Quay, CEO of Atossa, expressed optimism regarding the FDA's guidance. He emphasized that the detailed feedback aligns with their plan, reinforcing their strategy for advancing (Z)-endoxifen toward regulatory approval. This product candidate excels as a highly potent selective estrogen receptor modulator (SERM), showing potential not only in inhibiting estrogen receptors but also in degrading them. Moreover, it has demonstrated effectiveness in tumors resistant to other endocrine therapies while providing comparable bone-protective benefits when compared to tamoxifen.

Key Insights from FDA Feedback

The FDA's feedback encompassed several crucial aspects of Atossa's trial design. For starters, the agency agreed that the current clinical and nonclinical data are substantial enough to initiate the monotherapy portion of the dose optimization study. Clear directives on cohort sizes and enhancements in study design were also provided, helping to refine their approach.

In addition, the FDA endorsed the concept of combining (Z)-endoxifen with existing standard-of-care breast cancer therapies, like CDK4/6 inhibitors, mTOR inhibitors, and others. Although not all potential combinations will be explored in this study, the encouragement from the FDA helps streamline Atossa’s strategic framework as they gear up for the IND submission.

Furthermore, the FDA deemed Atossa’s existing nonclinical safety data adequate, negating the need for additional toxicity studies before proceeding with trials. An important aspect of their trial's cardiac safety assessment—utilizing electrocardiograms (ECGs) and QT interval monitoring—was also confirmed as sufficient for the monotherapy, highlighting Atossa’s diligence in ensuring patient safety throughout the drug development process.

Next Steps for Atossa

As Atossa moves forward, plans for the target patient group, combination therapies, and overall trial design will soon be announced. The FDA has encouraged Atossa to make specific safety and eligibility adjustments to the final trial protocol, which the company has committed to implementing.

Dr. Quay noted that with the FDA’s insights in hand, Atossa is motivated to progress swiftly. The company aims to uphold this strategic momentum, adhering closely to FDA expectations while prioritizing patient-centric solutions in its quest to deliver (Z)-endoxifen to those battling metastatic breast cancer.

The development of (Z)-endoxifen is fundamentally committed to addressing the urgent need for innovative therapies in the metastatic breast cancer arena, especially as existing treatment options may fall short for many patients. As part of its robust research programs, Atossa is also moving forward with multiple Phase 2 trials assessing (Z)-endoxifen, including studies for patients with ductal carcinoma in situ (DCIS) and specific breast cancer subtypes.

Atossa’s ongoing endeavors reflect not only its commitment to transforming breast cancer treatment but also its strategic alignment with ongoing regulatory frameworks like the FDA’s Project Optimus initiative, which emphasizes judicious dose selection based on sound data to improve patient outcomes. Anticipation grows around Atossa’s next innovations, as stakeholders eagerly await updates on clinical progress and potential market entry.