LeonaBio, Inc.

LeonaBio, Inc. is a clinical-stage biopharmaceutical company focused on developing new treatments for significant unmet medical needs, including treatment-resistant metastatic breast cancer and amyotrophic lateral sclerosis (ALS). In December 2025, the company acquired rights to lasofoxifene, a late-stage asset for the potential treatment of ESR1-mutated (mESR1) metastatic breast cancer. This program has generated promising clinical data. LeonaBio, Inc. also has an in-house asset, ATH-1105, which is a Phase 2-ready program for the potential treatment of ALS. The company aims to advance a pipeline of innovative, late-stage assets, both internally developed and strategically in-licensed. LeonaBio, Inc.'s lead drug candidates are lasofoxifene and ATH-1105, which are novel, small molecule therapies. Lasofoxifene, a selective estrogen receptor modulator (SERM), is currently being evaluated in an ongoing registrational Phase 3 trial for metastatic breast cancer with ESR1 mutations. ATH-1105, a small-molecule positive modulator of the neurotrophic HGF system, has completed a first-in-human Phase 1 trial, and planning for a Phase 2 clinical trial for the treatment of ALS is underway. These programs target unmet needs in either oncology or neurology.