LeonaBio to Host Virtual Key Opinion Leader Event Highlighting Potential of Lasofoxifene in Treatment-Resistant ER+/HER2-, ESR1-Mutated Metastatic Breast Cancer

Rhea-AI Summary

LeonaBio (NASDAQ: LONA) will host a virtual Key Opinion Leader event on April 29, 2026 at 12:00 p.m. ET to discuss lasofoxifene in treatment‑resistant ER+, HER2‑, ESR1‑mutated metastatic breast cancer. Management and two clinical experts will review the evolving treatment landscape.

The company expects to complete enrollment in ELAINE‑3 in 4Q26 with topline data anticipated in 2H27. The live webcast will be archived on LeonaBio's investor events page.

News Market Reaction – LONA

-3.36%

6 alerts

-3.36% Session close to close

+10.3% Peak Tracked

-8.1% Trough Tracked

$87.41M Market Cap

1.1x Rel. Volume

In the Apr 24 session, LONA declined 3.36%, reflecting a moderate negative market reaction. Argus tracked a peak move of +10.3% during that session. Argus tracked a trough of -8.1% from its starting point during tracking. Our momentum scanner triggered 6 alerts that day, indicating moderate trading interest and price volatility.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement centers on a virtual Key Opinion Leader event discussing lasofoxifene’s role in tr...

Analysis

This announcement centers on a virtual Key Opinion Leader event discussing lasofoxifene’s role in treatment-resistant ER+/HER2-, ESR1-mutated metastatic breast cancer and reiterates ELAINE-3 timelines, with enrollment targeted for 4Q26 and data expected in 2H27. It follows earlier scientific and corporate updates that emphasized the same Phase 3 program. Investors may monitor how expert commentary, future clinical readouts, funding developments, and execution against these timelines shape the evolving risk–benefit profile of LeonaBio’s lead asset.

Key Figures

ELAINE-3 enrollment target timing: 4Q26 Topline data timing: 2H27 Webinar date: April 29, 2026 +1 more

4 metrics

ELAINE-3 enrollment target timing 4Q26 Expected completion of enrollment in Phase 3 registrational ELAINE-3 study

Topline data timing 2H27 Data from ELAINE-3 Phase 3 registrational study expected

Webinar date April 29, 2026 Virtual Key Opinion Leader event on lasofoxifene

Webinar time 12:00 p.m. ET Start time for virtual Key Opinion Leader event

Historical Context

3 past events · Latest: Apr 21 (Positive)

Pattern 3 events

Date	Event	Sentiment	24h Move	Catalyst
Apr 21	Preclinical data update	Positive	-1.7%	AACR nonclinical lasofoxifene data supporting ELAINE-3 Phase 3 rationale.
Mar 26	Earnings and funding	Positive	-7.3%	Full-year 2025 results, private placement proceeds, and ELAINE-3/ALS timelines.
Feb 03	Leadership appointment	Positive	+0.0%	Appointment of experienced Chief Business Officer to drive partnering strategy.

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

Pattern Detected

Recent positive scientific, financial, and leadership updates have been followed by flat-to-negative next-day price reactions.

Recent Company History

Over recent months, LeonaBio has focused on advancing lasofoxifene. On Feb 3 (news_id 1007180), it added a seasoned Chief Business Officer to drive business development. On Mar 26 (news_id 1032366), it reported 2025 results, highlighted a $90M private placement with additional warrant potential, and reiterated ELAINE-3 timelines, yet shares fell 7.33%. On Apr 21 (news_id 1042560), supportive AACR nonclinical data preceded a 1.71% decline, underscoring a pattern of weak price follow-through on seemingly constructive news.

Key Terms

er+, her2-, esr1-mutated, metastatic breast cancer, +2 more

6 terms

er+ medical

"treatment-resistant estrogen receptor-positive (ER+), HER2-negative, ESR1-mutated metastatic"

er+ indicates that a tumor’s cells have receptors that bind the hormone estrogen, meaning the cancer can grow in response to that hormone. Like a lock that opens when the estrogen “key” fits, this characteristic guides doctors to use hormone-blocking treatments instead of or alongside chemotherapy, and it shapes the size and type of therapies that biotech and pharmaceutical companies develop and sell — information investors use to assess clinical strategy and market potential.

her2- medical

"treatment-resistant estrogen receptor-positive (ER+), HER2-negative, ESR1-mutated metastatic"

HER2- describes a tumor that lacks an excess of the HER2 protein or the gene that produces it; HER2 is a cell-surface receptor that can fuel cancer growth when overabundant. For investors, HER2- status matters because it determines whether patients will benefit from HER2-targeted medicines — like finding there is no matching lock for a specialized key — which directly affects the size of the eligible patient pool, treatment choices, pricing dynamics and potential sales for related drugs.

esr1-mutated medical

"treatment-resistant estrogen receptor-positive (ER+), HER2-negative, ESR1-mutated metastatic"

ESR1-mutated means there is a change in the ESR1 gene that alters the estrogen receptor protein, which tells certain cells how to respond to the hormone estrogen. Investors should care because in hormone-driven cancers these mutations can make standard hormone-blocking treatments stop working, increasing demand for alternative drugs and diagnostic tests and affecting clinical trial outcomes and the commercial value of therapies — like a lock changing shape so the usual key no longer fits.

metastatic breast cancer medical

"treatment landscape in metastatic breast cancer and the potential for lasofoxifene"

Metastatic breast cancer is breast cancer that has spread beyond the breast and nearby lymph nodes to other organs, such as bones, liver, lungs or brain. For investors it matters because these advanced-stage cases often require long-term, complex and costly treatments, drive demand for specialty drugs and diagnostics, and influence regulatory approvals, pricing negotiations and the long-term revenue potential of companies developing therapies aimed at slowing spread or improving quality of life. An everyday analogy: it’s like a weed that has taken root in multiple beds rather than just one garden patch, requiring broader and more sustained effort to manage.

phase 3 medical

"ongoing ELAINE-3 Phase 3 Registrational Study of Lasofoxifene in Metastatic"

Phase 3 is the late-stage clinical testing step for a new drug or medical treatment, where the product is given to large groups of patients to confirm effectiveness, monitor side effects, and compare it to standard care. Successful Phase 3 results are often the final scientific hurdle before regulators decide on approval and market launch—like passing a final exam before graduation—and can sharply change a company's valuation and future revenue prospects.

registrational study medical

"ongoing ELAINE-3 Phase 3 Registrational Study of Lasofoxifene in Metastatic"

A registrational study is a late-stage clinical trial designed to give the government regulators the evidence they need to decide whether a drug, therapy, or medical device can be approved for sale. Think of it as the final exam or road test for a medical product: its results largely determine whether the product can reach the market, which directly affects potential revenue, company valuation, and investor risk.

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

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Management to be Joined by Two Clinical Leaders in the Breast Cancer Field 

Expected to Complete Enrollment in Ongoing ELAINE-3 Phase 3 Registrational Study of Lasofoxifene in Metastatic Breast Cancer in 4Q26 with Data Expected in 2H27

Webinar Event on Wednesday, April 29, 2026, at 12:00 p.m. ET

BOTHELL, Wash., April 23, 2026 (GLOBE NEWSWIRE) -- LeonaBio, Inc. (NASDAQ: LONA), a clinical-stage biopharmaceutical company dedicated to the development of novel therapeutics for diseases with high unmet medical needs, today announced that it will host a virtual Key Opinion Leader event with two leading physician experts in the breast cancer field to discuss the current and evolving treatment landscape in metastatic breast cancer and the potential for lasofoxifene to transform the standard of care for patients with treatment-resistant estrogen receptor-positive (ER+), HER2-negative, ESR1-mutated metastatic breast cancer.

The event titled, “Modulation and Combination: the Potential for Lasofoxifene to Transform the Standard-of-Care in Metastatic Breast Cancer,” will take place on Wednesday, April 29, 2026, beginning at 12:00 p.m. ET. To participate in the event, register here.

“As we look toward completing enrollment in ELAINE-3 later this year, with data expected in the second half of 2027, we are pleased to be joined by two leading voices in the breast cancer field to discuss the evolving treatment landscape in metastatic disease,” said Mark Litton, Ph.D., President and Chief Executive Officer of LeonaBio. “This conversation will highlight the persistent gaps in care, particularly for genetically defined populations, and the potential for lasofoxifene to address a critical unmet need in patients with treatment-resistant ER+, HER2-, ESR1-mutated metastatic breast cancer.”

The webcast event will feature a discussion with David Portman, M.D., Chief Executive Officer of Sermonix Pharmaceuticals and an oncology consultant to LeonaBio, along with two physician experts in the breast cancer field:

• Matthew P. Goetz, M.D., Erivan K. Haub Family Professor of Cancer Research Honoring Richard F. Emslander, M.D, Mayo Clinic, Principal investigator and director, Breast Cancer Specialized Program of Research Excellence (SPORE), Mayo Clinic Comprehensive Cancer Center and Enterprise Deputy Director, Translational Research, Mayo Clinic Comprehensive Cancer Center.
• Seth Wander, M.D., Ph.D., Director of Precision Medicine, Termeer Center for Targeted Therapies, Director of Translational Research, Breast Oncology Program, Mass General Brigham Cancer Institute, Assistant Professor of Medicine, Harvard Medical School.
  
  

In addition to the live webinar, the event will be archived on the LeonaBio website under Events in the Investor Relations here.

About Metastatic Breast Cancer
Metastatic breast cancer (MBC) occurs when cancer spreads from the breast to other parts of the body—such as bones, lungs, liver, or brain. While approximately two-thirds of breast cancers are diagnosed at a localized stage, a notable proportion either present as metastatic at diagnosis or progress to that stage over time. From 2001 to 2021, approximately 4.65 million new cases of female breast cancer were reported in the United States, with approximately 260,000 (5.6%) diagnosed as distant (metastatic) stage at initial diagnosis. The metastatic breast cancer treatment market represents a sizable and rapidly expanding global opportunity with a global market of $17.1 billion in 2021, expected to expand to $41.7 billion by 2030, with a compound annual growth rate (CAGR) of approximately 10.4%. These projections reflect a market rich with innovation—from chemotherapy and hormone therapies to biologics, targeted agents and emerging personalized medicine. Growth is driven by the persistent incidence of metastatic disease, regulatory and clinical advances and evolving treatment landscapes.

About Lasofoxifene
Lasofoxifene is a novel, nonsteroidal selective estrogen receptor modulator (SERM) with a unique binding profile, designed to confer potent activity against both wild-type and mutant estrogen receptors, including the clinically significant ESR1 mutations commonly associated with resistance to endocrine therapy in metastatic breast cancer. Two Phase 2 studies—ELAINE-1 and ELAINE-2—have demonstrated its potential to address a critical unmet need in this patient population.

ELAINE-1, a randomized trial comparing lasofoxifene to fulvestrant, showed improved outcomes for lasofoxifene, including longer median progression-free survival (5.6 vs. 3.7 months), higher objective response rates (13.3% vs. 2.9%), and a durable complete response lasting more than 2.5 years. Patients also reported quality-of-life benefits and the treatment was well tolerated.

ELAINE-2, an open-label study evaluating lasofoxifene in combination with abemaciclib, demonstrated clinical benefits in heavily pretreated patients, with a median progression-free survival of approximately 13 months, an objective response rate of 56%, and a clinical benefit rate of 65.5%. The combination was generally well tolerated, with most adverse events being low grade.

Lasofoxifene is being advanced in a Phase 3 clinical trial as a targeted therapy for estrogen receptor-positive (ER+), HER2-negative, ESR1-mutated metastatic breast cancer, a population with limited treatment options following progression on aromatase inhibitors and CDK4/6 inhibitors. The ongoing ELAINE-3 trial (NCT05696626) is evaluating lasofoxifene in combination with the CDK4/6 inhibitor, abemaciclib, and is aiming to establish a new standard of care for this genetically defined patient group.

About LeonaBio
LeonaBio, headquartered in the Seattle, Washington area, is a clinical-stage biopharmaceutical company dedicated to the development of novel therapeutics for diseases with high unmet medical needs, including treatment-resistant metastatic breast cancer and amyotrophic lateral sclerosis (ALS), with the goal of improving patients’ lives. Our lead drug candidates, lasofoxifene and ATH-1105, are novel, small molecule therapies with the potential to address devastating diseases where current treatment options are limited or ineffective. With a strong commitment to scientific excellence and patient-centered innovation, we are dedicated to developing meaningful new therapies for those who need them most.

For more information, visit www.leonabio.com.

Forward-Looking Statements
This communication contains “forward-looking statements” within the meaning of Section 27A of the Securities Act, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995. These forward-looking statements are not based on historical fact and include statements regarding: the beneficial characteristics, safety and efficacy of LeonaBio’s drug candidates; the potential of any subsequent clinical trials to show the beneficial characteristics, safety and efficacy of LeonaBio’s drug candidates; LeonaBio’s drug candidates as potential treatments for metastatic breast cancer and other diseases; anticipated development milestone timelines, such as the completion of enrollment of clinical trials and the timing of data releases, and LeonaBio’s ability to meet such timelines; the potential of LeonaBio to complete the Phase 3 ELAINE-3 clinical trial for lasofoxifene and to meet the trial endpoints; LeonaBio’s ability to obtain regulatory approval for any of its product candidates and to successfully commercialize any approved products; the rate and degree of market acceptance of LeonaBio’s drug candidates, if approved for commercial use; the size and growth potential of the markets for LeonaBio’s drug candidates, if approved for commercial use, and LeonaBio’s ability to serve those markets; and the potential for lasofoxifene to be a new standard of care in its target genetically defined patient group. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as “may,” “will,” “should,” “on track,” “would,” “expect,” “plan,” “believe,” “intend,” “pursue,” “continue,” “suggest,” “potential,” “target” and similar expressions. Any forward-looking statements are based on management’s current expectations of future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to, risks associated with the possible failure to realize certain anticipated benefits of the license relating to lasofoxifene and the recent private placement financing, including with respect to future financial and operating results; the data from nonclinical and clinical trials may not support the safety, efficacy and tolerability of LeonaBio’s drug candidates; development of drug candidates may cease or be delayed; regulatory authorities could object to protocols, amendments and other submissions; future potential regulatory milestones for drug candidates, including those related to current and planned clinical studies, may be insufficient to support regulatory submissions or approval; whether LeonaBio’s trials are sufficiently powered to meet the planned endpoints; LeonaBio may not be able to recruit sufficient patients for its clinical trials; the outcome of legal proceedings that may in the future be instituted against LeonaBio, its directors and officers; possible negative interactions of LeonaBio’s drug candidates with other treatments; FDA regulatory delays and uncertainty and new policies, including executive orders, changes in the leadership of federal agencies such as the FDA and SEC, staff layoffs, budget cuts to agency programs and research and changes in drug pricing controls; LeonaBio’s assumptions regarding its financial condition and the sufficiency of its cash, cash equivalents and investments to fund its planned operations may be incorrect; adverse conditions in the general domestic and global economic markets, including as a result of tariffs; the impact of competition; the impact of drug candidate development and clinical activities on operating expenses; the impact of new or changing laws and regulations; as well as the other risks detailed in LeonaBio’s filings with the SEC from time to time. These forward-looking statements speak only as of the date hereof and LeonaBio undertakes no obligation to update forward-looking statements. LeonaBio may not actually achieve the plans, intentions or expectations disclosed in its forward-looking statements, and you should not place undue reliance on the forward-looking statements.

Investor & Media Contact:
Julie Rathbun
LeonaBio
Julie.rathburn@leonabio.com
206-769-9219

FAQ

When is LeonaBio (LONA) hosting the lasofoxifene Key Opinion Leader event?

The event is scheduled for April 29, 2026 at 12:00 p.m. ET. According to the company, the webinar will feature management and two breast cancer clinical experts and will be archived on LeonaBio's investor events page.

What did LeonaBio (LONA) say about ELAINE‑3 enrollment and data timing?

ELAINE‑3 enrollment is expected to complete in 4Q26. According to the company, topline data from the Phase 3 registrational study are anticipated in the second half of 2027.

Who will speak at LeonaBio's (LONA) lasofoxifene webinar on April 29, 2026?

Speakers include LeonaBio management and clinical leaders Matthew P. Goetz, M.D. and Seth Wander, M.D., Ph.D. According to the company, David Portman, M.D. will also participate as an oncology consultant.

How can investors access the LeonaBio (LONA) lasofoxifene webcast and archive?

Investors can join the live webcast by registering for the April 29 event. According to the company, the event recording will be archived under Events on LeonaBio's investor relations website.

What topics will LeonaBio (LONA) cover about lasofoxifene at the April 29 webinar?

The webinar will discuss the treatment landscape and lasofoxifene's potential in ER+, HER2‑, ESR1‑mutated metastatic breast cancer. According to the company, speakers will emphasize gaps in care and possible therapeutic roles for lasofoxifene.