Lasofoxifene (CP-336156) is a selective oestrogen receptor modulator/antagonist that reduces serum IL-6 levels and inhibits joint inflammation and osteoporosis. It suppresses primary tumour growth and metastasis, making it suitable for breast cancer research.

Methods: Lasofoxifene (1, 5, and 10 mg/kg, 5 times per week) was administered subcutaneously to NSG mice with established human-derived xenograft models (MIND models) to assess the antitumor activity of lasofoxifene in endocrine therapy-resistant ER+ breast cancer mouse models. Results: Lasofoxifene demonstrated superior efficacy in inhibiting tumor growth and metastasis compared to fulvestrant, especially in Y537S and D538G mutant tumors, where lasofoxifene showed stronger inhibitory effects. [1]