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Atossa Therapeutics and Its Accelerated FDA Strategy for (Z)-Endoxifen

Atossa Therapeutics, Inc., a pioneering biopharmaceutical company focused on breast cancer treatment and prevention, has revealed its strategy to expedite the advancement of (Z)-endoxifen. This innovative approach, discussed during a recent meeting with the U.S. Food and Drug Administration (FDA), aims to streamline the regulatory process across various treatment settings including metastatic breast cancer, neoadjuvant therapies, and risk-reduction strategies.

Overview of the FDA Meeting

On November 17, 2025, Atossa conducted a Type C meeting with the FDA, which is critical in a drug's developmental journey. In this meeting, the FDA provided valuable feedback on the clinical development design and endpoint strategies, which serve as a foundation for a more efficient registrational approach. According to Steven Quay, M.D., Ph.D., President and CEO of Atossa, the insights gained from the FDA discussions will significantly shorten the regulatory timeline, thereby enhancing the company's potential to expedite (Z)-endoxifen’s journey to market.

Key Clinical Development Focus

Atossa is strategically positioning itself to initiate critical trials in various high-value clinical settings:
1. Metastatic Breast Cancer (mBC): The company is preparing to conduct a dose-ranging study to support its registration strategy.
2. Neoadjuvant ER+/HER2- Breast Cancer: Progress continues in the Phase 2 EVANGELINE trial, which is crucial for establishing effective treatments in early-stage settings.
3. Breast Cancer Risk-Reduction: Atossa is exploring a low-dose approach aimed at reducing mammographic breast density and overall cancer risk, indicative of a proactive strategy in preventive health.

In addition to this, Atossa recently submitted an Investigational New Drug (IND) application to the FDA to further propel its metastatic breast cancer program. The company expects additional IND submissions in 2026, indicating its ambition to broaden its approach to combination therapies.

Clinical Trials and Patient Engagement

Atossa's ongoing clinical program has already involved nearly 800 participants. Insights from these studies form the backbone of the company's belief in its approach and regulatory strategy. Janet Rea, Senior Vice President of Research and Development, emphasized the importance of establishing clear, value-driven milestones in clinical trials. The anticipation of important upcoming data, combined with FDA input, supports the company's aim to achieve multiple regulatory endpoints.

Understanding (Z)-Endoxifen

(Z)-endoxifen is characterized as a powerful Selective Estrogen Receptor Modulator/Degrader (SERM/D) known for its ability to inhibit and potentially degrade estrogen receptors, even in cases where tumors have developed resistance to standard treatments. Its inhibitory properties are complemented by action on the oncogenic signaling pathway, protein kinase C beta 1 (PKCβ1), demonstrating its versatility as a therapeutic agent. Importantly, (Z)-endoxifen holds promise for delivering similar or superior bone-protective effects compared to tamoxifen, a standard treatment in breast cancer therapy.

A proprietary enteric oral formulation of (Z)-endoxifen has been developed by Atossa. This formulation avoids degradation by stomach acid, ensuring optimal bioavailability and therapeutic integrity. The drug has shown a favorable safety profile in both healthy individuals and breast cancer patients. To date, no maximum tolerated dose has been identified, which encourages ongoing research into its dosing.

Intellectual Property and Future Directions

Atossa's (Z)-endoxifen program is underpinned by a growing portfolio of global intellectual property, with a strong presence in the U.S. patent system. This robust legal foundation is instrumental in protecting the company’s innovations and strategies moving forward.

Conclusion

Atossa Therapeutics is firmly positioned to transform the landscape of breast cancer treatment and prevention. With a clear regulatory strategy informed by comprehensive FDA feedback, the company is enhancing its capabilities to deliver (Z)-endoxifen for various breast cancer indications. As it pushes towards quicker and more targeted therapeutic solutions, Atossa remains at the forefront of innovations in oncology.

For more information about Atossa Therapeutics and its ongoing projects, visit Atossa's website.