LeonaBio has enrolled 495 patients in its Phase 3 ELAINE-3 trial of lasofoxifene, putting enrollment at roughly 83% of the study’s approximately 600-patient target as the company works toward completing enrollment in the fourth quarter of 2026. Topline data from the registrational study are expected in the second half of 2027, while outstanding cash-exercisable warrants could provide LeonaBio with up to an additional $146 million if exercised in full.
ELAINE-3 is evaluating lasofoxifene in combination with the CDK4/6 inhibitor abemaciclib in patients with ER-positive, HER2-negative, ESR1-mutated metastatic breast cancer following progression on aromatase inhibitors and CDK4/6 inhibitors. The primary endpoint is improvement in progression-free survival as determined through blinded independent central review.
LeonaBio obtained rights to lasofoxifene through an exclusive global license from Sermonix Pharmaceuticals in December 2025, excluding Asia and certain Middle Eastern countries. The agreement effectively shifted LeonaBio’s near-term development focus toward the late-stage breast cancer program.
The company is already investing ahead of the Phase 3 readout. LeonaBio said it is funding chemistry, manufacturing and controls work, regulatory preparation and commercial-readiness activities as ELAINE-3 approaches the end of enrollment, positioning the program for further development and potential commercialization if the trial and subsequent regulatory process are successful.
Financing capacity will be important as those activities advance. LeonaBio completed a $90 million private placement of common stock and warrants in connection with the Sermonix transaction in December 2025. The associated Series A warrants could generate up to another $146 million if fully exercised, with the proceeds intended to support development through clinical and regulatory milestones.
At June 30, LeonaBio had $51.1 million of cash, cash equivalents and investments, down from $88.3 million at the end of 2025. Net cash used in operations reached $37.9 million during the second quarter compared with $21.7 million a year earlier, reflecting the increased investment required as ELAINE-3 advances.
Research and development expense increased to $12.9 million from $3.7 million, primarily because of clinical trial spending on ELAINE-3. General and administrative expense increased to $6.6 million from $3.6 million. The company reported a second-quarter net loss of $19 million, or $0.80 per share, compared with $7 million, or $1.78 per share, a year earlier.
Prior clinical studies provide the basis for advancing lasofoxifene into the current registrational program. In ELAINE-1, lasofoxifene produced median progression-free survival of 5.6 months compared with 3.7 months for fulvestrant and an objective response rate of 13.3% versus 2.9%, although the study was not powered for those comparisons.
ELAINE-2 evaluated lasofoxifene in combination with abemaciclib in heavily pretreated patients and reported median progression-free survival of approximately 13 months, an objective response rate of 56% and a clinical benefit rate of 65.5%. LeonaBio is now testing that same combination in the larger Phase 3 ELAINE-3 study.
LeonaBio is also developing brelgometon for ALS, but its near-term resource allocation is clearly centered on the lasofoxifene program. The company said it will provide an update on timing for a proposed Phase 2 proof-of-concept study of brelgometon after completing ELAINE-3 enrollment.
KEY QUOTES:
“We enter the second half of 2026 with a clear focus on executing our Phase 3 ELAINE-3 trial and advancing lasofoxifene toward what we believe could be a transformative treatment option for patients with ESR1-mutated metastatic breast cancer. We have enrolled 495 patients and remain on track to complete enrollment of ELAINE-3 in the fourth quarter of 2026 with topline data expected in the second half of 2027. As the treatment landscape for metastatic breast cancer continues to evolve, we believe the differentiated profile of lasofoxifene positions it to address a significant unmet need as a potential endocrine therapy partner and create opportunities beyond ELAINE-3, including additional combination strategies and future label expansions. The body of clinical and scientific evidence behind lasofoxifene supports our confidence in its potential to greatly benefit patients battling this difficult-to-treat form of breast cancer.”
“As we approach the completion of enrollment in this Phase 3 registrational trial, we are investing today in critical CMC, regulatory, and commercial readiness activities to ensure we are well-positioned to bring this therapy to patients as quickly as possible, if approved. With our talented team and the potential to add up to an additional $146 million upon exercise of cash-exercisable warrants issued in our December 2025 financing, we believe LeonaBio is well-positioned to deliver on multiple value-creating milestones in the years ahead.”
Mark Litton, Ph.D., President and Chief Executive Officer of LeonaBio
