Lasofoxifene

Hormonal / PCT

Also known as: Fablyn, CP-336156, Lasofoxifene Tartrate

Selective Estrogen Receptor ModulatorsResearch phase: EMA-approved / Phase 2 (oncology)Regulatory: EMA-approved for osteoporosis (Fablyn). Not FDA-approved. Under clinical investigation for ESR1-mutant breast cancer.

Mechanism

Lasofoxifene is a third-generation SERM approved by the European Medicines Agency for osteoporosis. It shows broad tissue selectivity — bone protection, breast cancer risk reduction, cardiovascular benefit, and vaginal health improvement — with minimal uterine stimulation. It is also being investigated for ESR1-mutant ER+ breast cancer.

Technical detail

Lasofoxifene is a naphthalene-derived third-generation SERM with high oral bioavailability and a long half-life (~6 days). The PEARL trial (n=8,556) demonstrated significant reductions in vertebral and non-vertebral fractures, ER-positive breast cancer incidence (79% reduction), coronary heart disease events, and stroke, alongside improvements in vaginal atrophy measures — representing the broadest benefit profile of any SERM. It is currently under investigation (ELAINE trials) for ESR1-mutated advanced ER+ breast cancer, where ESR1 mutations confer resistance to aromatase inhibitors.

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