LeonaBio enrolls 500th subject in Phase 3 ELAINE-3 trial

LeonaBio, Inc. (NASDAQ: LONA) said in a Form 8-K dated August 26, 2026 that it enrolled the 500th subject in its Phase 3 ELAINE-3 trial of lasofoxifene. The trial tests lasofoxifene in combination with abemaciclib, a CDK4/6 inhibitor, as a targeted therapy for estrogen receptor-positive, HER2-negative, ESR1-mutated metastatic breast cancer that has progressed on aromatase inhibitors and CDK4/6 inhibitors. The filing says the announcement also establishes the ELAINE-3 Enrollment Date as of the date of the report, which is one of the conditions that determine when the Series A common warrants can be exercised.

The warrant terms

The company issued warrants in its December 2025 private placement, including 23,031,494 Series A Common Warrants. The exercise price is $6.35 per share, payable in cash. If the resale registration statement covering the underlying shares is unavailable at the time of exercise, the warrants can be exercised on a cashless net exercise basis instead.

Each holder may exercise after the earlier of October 31, 2026 and the latest of three dates: June 30, 2026, the ELAINE-3 Enrollment Date, and the date on which the U.S. Food and Drug Administration approves, or issues a complete response letter for, the marketing application for imlunestrant in combination with abemaciclib submitted by Eli Lilly & Co. The warrants remain exercisable until the 30th day after that initial exercise date, and no later than November 30, 2026.

If exercised in full, the warrants would provide the company with approximately $146.2 million of additional capital. The filing names no underwriter, placement agent or financial advisor for the December 2025 private placement or for the warrants.

The trial and the drug

LeonaBio describes itself as a clinical-stage biopharmaceutical company. The annual report traces lasofoxifene to a research collaboration between Pfizer Inc. and Ligand Pharmaceuticals. Pfizer continued development of the drug in osteoporosis, female sexual dysfunction and vaginal atrophy, and in 2011 returned global rights to Ligand. Sermonix Pharmaceuticals later in-licensed it from Ligand in 2015.

The European Medicines Agency approved lasofoxifene for osteoporosis in 2009 under the name Fablyn. Pfizer decided not to launch Fablyn in Europe, and the marketing authorization was withdrawn automatically under the Sunset Provision in 2012. The annual report says lasofoxifene is not authorized for marketing anywhere in the world today.

The company's current development path centers on ELAINE-3. The annual report says the trial is a pivotal study, that the company plans to complete it to position lasofoxifene for potential approval in the United States and Europe, if successful, and that topline data are expected in the second half of 2027. Roughly 70% of breast cancer cases are estrogen receptor-positive, and the annual report describes resistance to endocrine therapy, often through ESR1 mutations, as the unmet need the drug is designed to address.

Financial position

The annual report figures in SEC XBRL data show research and development expense of $17.5 million for 2025, against $70.7 million for 2024. The net loss was $105.6 million for 2025 and $96.9 million for 2024. Operations used $45.7 million of cash in 2025 and $97.2 million in 2024.

At year-end 2025, cash and cash equivalents were $69.3 million and short-term investments were $19.1 million. A year earlier, the company reported $48.4 million of cash and cash equivalents and $2.8 million of short-term investments. The quarterly report shows cash and cash equivalents of $32.3 million at June 30, 2026, with short-term investments of $18.7 million.

What is unproven and what could go wrong

LeonaBio has no approved product, and the annual report says lasofoxifene is not authorized for marketing anywhere in the world. Enrolling the 500th subject is a milestone for the trial's size, not evidence that the drug works. ELAINE-3 must still finish and report topline data, which the company expects in the second half of 2027.

The company lost $105.6 million in 2025, with operations using $45.7 million of cash, and held $32.3 million in cash and $18.7 million in short-term investments at June 30, 2026. Warrant proceeds of about $146.2 million depend on holders choosing to exercise, with the window ending no later than November 30, 2026. Full exercise would mean 23,031,494 new shares at $6.35, which adds to the share count.

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