# Atossa Therapeutics

Source: https://onco.cc/companies/atossa-therapeutics/  
OnCo record `atossa-therapeutics` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Atossa is a Seattle company developing oral endoxifen, the active metabolite of tamoxifen, for breast cancer prevention and treatment and for reducing dense breast tissue.

## Summary

Atossa Therapeutics, founded in 2009 in Seattle, develops (Z)-endoxifen, the most active metabolite of tamoxifen, as an oral drug that bypasses the CYP2D6 metabolism that makes tamoxifen variable between patients. It is tested to reduce mammographic breast density in women at high risk, in the window before surgery, and alongside CDK4/6 inhibitors in advanced hormone receptor-positive breast cancer. Its trials are registered on ClinicalTrials.gov under Atossa as lead sponsor.

## Fields

- Kind: Company
- Last checked: 2026-09-11
- Also known as: Atossa Therapeutics, Inc.; Atossa Genetics
- Tags: ctgov-sponsor
- HQ: Seattle, WA
- Type: biotech
- Website: https://atossatherapeutics.com

## Sources

- Official website: https://atossatherapeutics.com
- ClinicalTrials.gov: trials led by Atossa Therapeutics, Inc.: https://clinicaltrials.gov/search?lead=Atossa%20Therapeutics%2C%20Inc.
- Wikidata: https://www.wikidata.org/wiki/Q107517747

## Connected records

- cancers: [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/)
- fronts: [Hormonal Therapy](https://onco.cc/fronts/hormonal/), [Prevention & Risk](https://onco.cc/fronts/prevention/)
- terms: [Clinical trial](https://onco.cc/terms/clinical-trial/), [Pivotal (registrational) trial](https://onco.cc/terms/pivotal-trial/)

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JSON: https://onco.cc/api/v1/entities/atossa-therapeutics.json