Atossa Therapeutics to Host Virtual KOL Event Featuring Dr. Laura Esserman to Discuss Development of (Z)-Endoxifen in ER-Positive Breast Cancer

Atossa Therapeutics (Nasdaq: ATOS) will host a virtual key opinion leader event on May 19, 2026, highlighting development of its investigational SERM/D (Z)-endoxifen in ER-positive breast cancer.

Rhea-AI Summary

Atossa Therapeutics (Nasdaq: ATOS) will host a virtual key opinion leader event on May 19, 2026, highlighting development of its investigational SERM/D (Z)-endoxifen in ER-positive breast cancer.

The webinar will feature breast cancer expert Dr. Laura Esserman discussing emerging clinical and translational data, combination strategies, and development opportunities.

Argus May 14 session

-0.19% close to close Open Argus

Details

News Market Reaction – ATOS

In the May 14 session, ATOS declined 0.19%, reflecting a mild negative market reaction.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement spotlights Atossa’s effort to position (Z)-endoxifen as a next‑generation endocrin...

Analysis

This announcement spotlights Atossa’s effort to position (Z)-endoxifen as a next‑generation endocrine therapy in ER‑positive breast cancer, leveraging data from the I‑SPY2 Endocrine Optimization Pilot and translational biomarkers like Ki‑67 and circulating tumor DNA. Historically, the company has paired such scientific updates with regulatory designations and leadership hires. Investors may watch how this event frames future trial strategy, combination plans, and development across multiple ER‑positive settings.

Key Figures

Event date: May 19, 2026 Event time: 1:00–2:00 p.m. PT Replay availability: 60 days +2 more

Event date

May 19, 2026

Scheduled virtual KOL event on (Z)-endoxifen

Event time

1:00–2:00 p.m. PT

Scheduled duration of KOL webcast

Replay availability

60 days

Webcast replay on investor website

I-SPY2

I-SPY2 trial

Endocrine Optimization Pilot evaluating (Z)-endoxifen monotherapy

CDK4/6

CDK4/6 inhibitor

Planned combination strategy with (Z)-endoxifen

Historical Context

5 past events · Latest: May 08

5 events

1. May 08

   Q1 2026 results

   24h Move

   -1.2%

   Quarterly results showed higher operating expenses and a larger net loss in Q1 2026.

2. May 06

   Phase 2 publication

   24h Move

   +3.9%

   KARISMA Phase 2 data showed significant reductions in mammographic breast density with Endoxifen.

3. May 04

   RPD designation

   24h Move

   +9.9%

   FDA granted Rare Pediatric Disease designation for (Z)-endoxifen in McCune-Albright Syndrome.

4. Mar 25

   2025 results

   24h Move

   -13.1%

   Year-end 2025 report highlighted larger net loss and higher operating expenses versus 2024.

5. Mar 19

   Leadership hires

   24h Move

   +0.4%

   Company added two senior clinical leaders to advance breast cancer and rare disease programs.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

key opinion leader, selective estrogen receptor modulator/degrader, serm/d, estrogen receptor, +4 more

8 terms

key opinion leader technical

"it will host a virtual key opinion leader event focused on the evolving"

A key opinion leader is an individual whose insights, expertise, or influence significantly shape the opinions and decisions of others within a particular field or community. For investors, they are like trusted guides whose views can impact market trends or perceptions, making their perspectives important to watch. Their influence often stems from experience, reputation, or widespread respect among peers.

selective estrogen receptor modulator/degrader medical

"the Company's investigational selective estrogen receptor modulator/degrader, or SERM/D"

A selective estrogen receptor modulator/degrader (SERM/SERD) is a drug that targets the estrogen receptor in the body and either blocks its action in some tissues or causes the receptor to be removed. Think of it like a dimmer switch or a targeted cleaner that turns down or takes away a specific control knob rather than shutting down the whole system; for investors this matters because these drugs can treat hormone-driven diseases, drive sales or licensing value, and are sensitive to clinical trial results, approvals and competing therapies.

serm/d medical

"selective estrogen receptor modulator/degrader, or SERM/D, as a potential"

A SERM/D is a drug that both modulates and promotes destruction of the estrogen receptor in certain cells—combining the effects of a selective estrogen receptor modulator (SERM) and a selective estrogen receptor degrader (SERD). For investors, this matters because such dual-action drugs can offer stronger or more durable control of hormone-driven diseases (like some breast cancers), which may increase clinical value, market potential, and the importance of trial or approval milestones.

estrogen receptor medical

"backbone across multiple estrogen receptor ("ER") -positive breast cancer"

A protein inside or on the surface of cells that binds the hormone estrogen and changes how those cells behave, for example by turning certain genes on or off; think of it as a lock that estrogen (the key) fits into to flip a biological switch. Investors care because these receptors are common drug targets and diagnostic markers—knowing whether a disease involves estrogen receptors can affect treatment choices, regulatory approval prospects, and the commercial value of therapies and tests.

biomarker medical

"to discuss the emerging clinical and biomarker data supporting this opportunity"

A biomarker is a measurable indicator found in the body, such as in blood or tissues, that provides information about health, disease, or how the body responds to treatment. For investors, biomarkers can signal the potential success or risk of medical products or therapies, influencing the value of related companies and industry trends. They act like signals or clues that help assess the progress of medical advancements and their market impact.

ki-67 medical

"Translational biomarker data, including Ki-67 reduction, MRI functional tumor"

Ki-67 is a protein found in cells that marks how quickly they are dividing; doctors measure it in tumor samples to estimate how fast a cancer is growing, similar to checking a car’s speed to judge how urgently it needs attention. For investors, Ki-67 levels matter because they can influence clinical trial results, help predict a treatment’s effectiveness or approval prospects, and affect the size of the potential market for therapies and diagnostics tied to cancer growth.

circulating tumor DNA medical

"MRI functional tumor volume changes, and circulating tumor DNA dynamics"

Fragments of DNA shed by cancer cells into the bloodstream that act like tiny fingerprints of a tumor; they can be detected with a blood test rather than a biopsy. Investors care because circulating tumor DNA (ctDNA) enables faster, lower-cost ways to detect disease, track treatment response, identify emerging resistance and enroll patients in trials—factors that can materially affect the commercial prospects of diagnostics and therapeutics.

cdk4/6 inhibitor medical

"Combination strategies, including CDK4/6 inhibitor combinations"

A CDK4/6 inhibitor is a type of cancer drug that blocks two proteins (CDK4 and CDK6) that tell cells to divide, effectively slowing or stopping the growth of tumors. Think of it as cutting power to a photocopier that keeps making cancer cells; that control can shrink tumors or delay progression. For investors, these drugs matter because clinical trial results, regulatory approvals, patent life, safety issues and competition directly affect sales potential and company value.

AI-generated analysis. How Rhea-AI works. Not financial advice.

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

Event to feature Dr. Laura Esserman, internationally recognized surgical oncologist, breast cancer expert, and founder and principal investigator of the I-SPY Trials

SEATTLE, May 14, 2026 /PRNewswire/ -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) ("Atossa" or the "Company"), a clinical-stage biopharmaceutical company developing novel therapies in oncology and other areas of significant unmet medical need, today announced that it will host a virtual key opinion leader event focused on the evolving clinical and translational data supporting the development of (Z)-endoxifen, the Company's investigational selective estrogen receptor modulator/degrader, or SERM/D, as a potential next-generation endocrine therapy backbone across multiple estrogen receptor ("ER") -positive breast cancer settings.

The event will feature internationally recognized surgical oncologist and breast cancer expert Dr. Laura Esserman. Dr. Esserman serves as Director of the University of California San Francisco Breast Care Center and is the founder and principal investigator of the I-SPY Trials, an innovative platform designed to accelerate the development of personalized breast cancer therapies.

"Dr. Esserman has been at the forefront of innovation in breast cancer clinical research, adaptive trial design, and precision oncology for decades," said Dr. Steven Quay, M.D., Ph.D., Chairman and Chief Executive Officer of Atossa Therapeutics. "We believe (Z)-endoxifen has the potential to become more than a single-indication therapy; it may serve as an endocrine therapy platform across multiple ER-positive breast cancer settings. Dr. Esserman's leadership in translational breast cancer research makes her an ideal expert to discuss the emerging clinical and biomarker data supporting this opportunity."

The discussion is expected to address several topics of interest to clinicians, investors, and potential strategic partners, including:

• Recent data from the I-SPY2 Endocrine Optimization Pilot study evaluating (Z)-endoxifen as monotherapy in newly diagnosed ER-positive breast cancer patients
• Translational biomarker data, including Ki-67 reduction, MRI functional tumor volume changes, and circulating tumor DNA dynamics
• Data supporting (Z)-endoxifen activity across clinically relevant ESR1 mutations, including Y537N, Y537S, and D538G
• The rationale for (Z)-endoxifen as a potential next-generation endocrine therapy backbone
• Combination strategies, including CDK4/6 inhibitor combinations
• Development opportunities in premenopausal breast cancer and endocrine therapy optimization

Event Details

Date: Tuesday, May 19, 2026
Time: 1:00 to 2:00 p.m. PT
Moderator: Michael King, Managing Director at Rodman & Renshaw
Registration: https://zoom.us/webinar/register/WN_fd6jdLUvQPC-3J84CUEnMA

Attendees may submit questions to ATOS@waterseid.com up to 24 hours prior to the event.

A replay of the webcast will be available on the Company's "Investors" portion of its website for at least 60 days following the live event.

About (Z)-Endoxifen

(Z)-endoxifen is a potent Selective Estrogen Receptor Modulator/Degrader, or SERM/D, with demonstrated activity across multiple mechanisms of action. Atossa is evaluating its potential applications in oncology and rare diseases. The Company's proprietary oral formulation has shown a favorable safety profile and pharmacology distinct from tamoxifen, including ER-targeted effects and PKC inhibition. Atossa's (Z)-endoxifen is not approved for any indication.

About Atossa Therapeutics

Atossa Therapeutics, Inc. (Nasdaq: ATOS) is a clinical-stage biopharmaceutical company developing innovative medicines in oncology and other areas of significant unmet need. The Company's lead product candidate, (Z)-endoxifen, is currently in development across several clinical settings.

Atossa's (Z)-endoxifen program is supported by a growing global intellectual property portfolio, including multiple recently issued U.S. patents and numerous pending applications worldwide. More information is available at https://atossatherapeutics.com.

Forward-Looking Statements

This press release contains certain "forward-looking statements" within the meaning of applicable securities laws, including but not limited to statements regarding the Company's development and regulatory strategy and related milestones; the potential indications that the Company may pursue for (Z)-endoxifen; the potential role of (Z)-endoxifen as an endocrine therapy platform; the potential for (Z)-endoxifen to receive regulatory approval and the timing thereof; expectations regarding the design, enrollment, data, timing, results and outcomes of the Company's clinical studies; and the potential market and growth opportunities for the Company. Words such as "expect," "potential," "continue," "may," "will," "should," "could," "would," "seek," "intend," "plan," "estimate," "anticipate," "believe," "design," "predict," "future," and similar expressions are intended to identify forward-looking statements.

Forward-looking statements in this press release are subject to risks and uncertainties that may cause actual results, outcomes, or the timing of actual results or outcomes to differ materially from those projected or anticipated, including, without limitation, risks and uncertainties associated with: the Company's ability to successfully execute its strategy to shorten clinical development timelines for its lead program, (Z)-endoxifen; the expected timing, completion and results of preclinical studies, clinical trials, and research and development programs; the unpredictable relationship between preclinical study results and clinical study results; the timing or likelihood of regulatory filings and approvals; the outcome or timing of necessary regulatory approvals; the Company's ability to maintain compliance with Nasdaq listing requirements; the Company's ability to establish and maintain intellectual property rights covering its products; the impact of general macroeconomic conditions on the Company's business; the Company's ability to raise capital; and other risks and uncertainties detailed from time to time in Atossa's filings with the SEC, including, without limitation, its Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q.

Forward-looking statements are presented as of the date of this press release. Except as required by law, the Company does not intend to update any forward-looking statements.

View original content to download multimedia:https://www.prnewswire.com/news-releases/atossa-therapeutics-to-host-virtual-kol-event-featuring-dr-laura-esserman-to-discuss-development-of-z-endoxifen-in-er-positive-breast-cancer-302771938.html

SOURCE Atossa Therapeutics Inc

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What is the focus of Atossa Therapeutics' May 19, 2026 virtual KOL event on (Z)-endoxifen (NASDAQ: ATOS)?

The event will focus on emerging clinical and translational data for (Z)-endoxifen in ER-positive breast cancer. According to Atossa, topics include biomarker responses, ESR1 mutation activity, combination strategies, and development opportunities in premenopausal and endocrine therapy optimization settings.

Who is Dr. Laura Esserman and what is her role in the Atossa (ATOS) (Z)-endoxifen KOL event?

Dr. Laura Esserman is an internationally recognized breast cancer surgeon and researcher speaking at the event. According to Atossa, she directs the UCSF Breast Care Center and founded the I-SPY Trials, bringing expertise in adaptive trial design and precision oncology to the (Z)-endoxifen discussion.

What clinical data on (Z)-endoxifen in ER-positive breast cancer will Atossa (ATOS) highlight during the May 2026 webinar?

Atossa plans to highlight data from the I-SPY2 Endocrine Optimization Pilot studying (Z)-endoxifen monotherapy in newly diagnosed ER-positive patients. According to Atossa, the event will cover Ki-67 reduction, MRI functional tumor volume changes, circulating tumor DNA dynamics, and activity across key ESR1 mutations.

How is Atossa Therapeutics positioning (Z)-endoxifen as an endocrine therapy backbone for ER-positive breast cancer (ATOS)?

(Z)-endoxifen is being developed as a potential next-generation endocrine therapy backbone across multiple ER-positive settings. According to Atossa, the event will review rationale for this strategy, including biomarker data, ESR1 mutation activity, and combination approaches such as CDK4/6 inhibitor regimens.

When is the Atossa (NASDAQ: ATOS) (Z)-endoxifen virtual KOL event and how can investors attend?

The webinar is scheduled for Tuesday, May 19, 2026, from 1:00 to 2:00 p.m. PT. According to Atossa, investors can register via the provided Zoom link, submit questions up to 24 hours prior, and access a replay on the company’s investor website for at least 60 days.

Will Atossa (ATOS) discuss (Z)-endoxifen combination strategies like CDK4/6 inhibitors at the May 19, 2026 event?

Yes, combination strategies are planned as a discussion topic during the event. According to Atossa, the KOL session will cover combining (Z)-endoxifen with CDK4/6 inhibitors and explore additional development opportunities in premenopausal breast cancer and broader endocrine therapy optimization.