LeonaBio (formerly Athira Pharma) is a clinical-stage biopharmaceutical company developing treatments for ESR1-mutated metastatic breast cancer and ALS. The company has no approved products and no product revenue, funding operations entirely through equity financing. LeonaBio's lead asset is lasofoxifene, an oral selective estrogen receptor modulator (SERM) in-licensed from Sermonix Pharmaceuticals in December 2025. Lasofoxifene is designed to inhibit estrogen receptor signaling even in breast cancers with ESR1 mutations, a key resistance mechanism to standard endocrine therapies. It is currently in a pivotal Phase 3 trial (ELAINE-3) in combination with abemaciclib for ER+/HER2- metastatic breast cancer patients who progressed after prior CDK4/6 inhibitor-based therapy, with topline data expected in the second half of 2027. LeonaBio's second lead candidate, ATH-1105, is an internally developed oral small molecule targeting the HGF/MET neurotrophic system as a potential ALS treatment; it completed Phase 1 in healthy volunteers and a Phase 2 trial in ALS patients is planned for 2026. The company also has ATH-1020, an earlier HGF/MET-targeting compound that completed part of a Phase 1 trial. LeonaBio's path to commercialization involves either independent product launches or partnerships and licensing arrangements for both assets. The company employs 19 people.