Lasofoxifene found to be a promising treatment for therapy-resistant breast cancer

University of Chicago researchers have found lasofoxifene outperformed fulvestrant, the current gold-standard drug, in reducing or preventing primary breast cancer tumor growth in mice. The drug also was more effective at preventing metastasis in the lung, liver, bone and brain, the four most common areas for breast cancer to spread.

Additionally, while fulvestrant and similar drugs often cause unwanted, menopausal-like side effects, lasofoxifene prevented some of these symptoms in the study, which was published on May 13 in phase 2 clinical trial is now underway at UChicago Medicine to study lasofoxifene as a second-line treatment in postmenopausal women with ER positive metastatic breast cancers that have ER mutations. A separate clinical trial, now enrolling patients, will study lasofoxifene in combination with abemaciclib, a chemotherapy drug similar to palbociclib.

“Most women with ER-positive metastatic breast cancer right now are treated with fulvestrant, and based on our study, I don’t think it’s the best drug for this purpose,” said Muriel Laine, PhD, a research associate in the Ben May Department and lead author on the study. “Lasofoxifene definitely appears to be more promising for these women.”

The study, “Lasofoxifene as a potential treatment for therapy-resistant ER-positive metastatic breast cancer,” was supported by Sermonix Pharmaceuticals and the U.S. Department of Energy, Office of Biological and Environmental Research (DE-AC02-06CH11357). Additional authors include Ya-Fang Chang, Bradley Green, Marianne E. Greene, Justyna D. Kurleto and Linda Phung of UChicago; Sean W. Fanning of Loyola University Chicago; and Barry Comm of Komm-Sandin Pharma Consulting.