Lasofoxifene Demonstrates Bone Protection and Tumor Regression in ESR1-Mutant Preclinical Study
Independent nonclinical data showed lasofoxifene prevented hormone withdrawal-induced bone loss and maintained robust anti-tumor responses in ER-positive and ESR1-mutant breast cancer animal models. These findings align with LeonaBio’s ELAINE-3 Phase 3 trial evaluating lasofoxifene combined with abemaciclib for ESR1-mutated metastatic breast cancer.
1. Preclinical Efficacy of Lasofoxifene
Independent researchers presented data showing lasofoxifene prevented hormone withdrawal–induced bone loss and maintained a robust anti-tumor response in primary and metastatic ER-positive breast cancer animal models.
2. Activity in ESR1-Mutant Models
In ESR1-mutant disease models, lasofoxifene significantly reduced metastatic tumor burden in bone while preserving bone microenvironment integrity, highlighting its context-dependent estrogen receptor agonist activity.
3. Support for ELAINE-3 Phase 3 Trial
These nonclinical results reinforce the scientific rationale for the ongoing ELAINE-3 trial (NCT05696626), which is evaluating lasofoxifene in combination with the CDK4/6 inhibitor abemaciclib for ESR1-mutated metastatic breast cancer.
4. Prior Clinical Data and Next Steps
Phase 2 studies ELAINE-1 and ELAINE-2 demonstrated lasofoxifene’s clinical potential, with ELAINE-1 showing median progression-free survival of 5.6 vs 3.7 months and ELAINE-2 reporting a 56% objective response rate; Phase 3 enrollment is underway.