Investigating Lasofoxifene Efficacy Against the Y537S

Estrogen receptor alpha (ER alpha) plays a critical role in breast cancer (BC) progression, with endocrine therapy being a key treatment for ER alpha + BC. However, resistance often arises due to somatic mutations in the ER alpha ligand-binding domain (LBD). Lasofoxifene, a third-generation selective estrogen receptor modulator, has shown promise against Y537S and D538G mutations. However, the emergence of a novel F404 mutation in patients with pre-existing LBD mutations raises concerns about its impact on lasofoxifene efficacy. This study investigates the impact of the dual Y537S and F404V mutations on lasofoxifene's efficacy. Using molecular dynamics simulations and molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) free energy calculations, we found that the dual mutation reduces lasofoxifene binding affinity and binding free energy, disrupts crucial protein-ligand interactions, and induces significant conformational changes in the ligand-binding pocket. These alterations are likely due to the loss of the pi-pi stacking interaction in the F404V mutation. These findings suggest a potential reduction in lasofoxifene efficacy due to the dual mutation. Further experimental validation is required to confirm these results and fully understand the impact of dual mutations on lasofoxifene's effectiveness in ER alpha + metastatic BC.