On April 23, 2026 LeonaBio, Inc. (NASDAQ: LONA), a clinical-stage biopharmaceutical company dedicated to the development of novel therapeutics for diseases with high unmet medical needs, reported 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.

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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.

(Press release, LeonaBio, APR 23, 2026, View Source [SID1234664739])