Sermonix Launches Phase 2 Trial Testing Lasofoxifene in Advanced Breast Cancer Patients with ER Mutations

Sermonix Launches Phase 2 Trial Testing Lasofoxifene in Advanced Breast Cancer Patients with ER Mutations

Sermonix is launching a Phase 2 trial to determine if its lead investigational medicine lasofoxifene is better than Faslodex (fulvestrant) at delaying disease progression or death in breast cancer patients who have a mutation in the estrogen receptor gene ESR1.

The open-label, randomized, multicenter trial will include 100 postmenopausal women with locally advanced or metastatic ER-positive/HER2-negative breast cancer. Recruitment will take place across 27 sites in the U.S.

“Sermonix is developing lasofoxifene as a personalized medicine treatment for patients with ER+ metastatic breast cancer that have progressed after endocrine and other therapies,” David Portman, Sermonix’s CEO, said in a press release. “We look forward to seeing how it performs in the Phase 2 trial versus fulvestrant.”

Therapies targeting the estrogen receptor (ER), such as Faslodex, are a mainstay in the treatment of ER-positive breast cancer. But despite initial responses, a large number of patients becomes resistant to treatment by acquiring ER mutations.

Lasofoxifene is a selective estrogen receptor modulator approved in Lithuania and Portugal under the brand name Fablyn for the prevention and treatment of osteoporosis and for the treatment of vaginal atrophy. The medicine has been tested in clinical trials involving more than 15,000 women, where it was also shown to reduce the rates of ER-positive breast cancer by 80 percent.

Interestingly, Sermonix found that lasofoxifene can also bind with high affinity to mutated estrogen receptors, suggesting it could be used for ER-positive patients who acquired resistance to other ER-targeting agents.

Sermonix now owns exclusive rights to develop and commercialize lasofoxifene for breast cancer patients with ESR1 mutations. The medicine could “be the ideal anti-estrogen to pair with newer agents — and those in development — for the treatment of advanced breast cancer,” the company says on its website.

“Clinical data have shown a significant reduction in the incidence of ER+ breast cancer in postmenopausal women with osteoporosis who were treated with lasofoxifene,” said Paul Plourde, MD, Sermonix’s vice president of clinical development. “Additional non-clinical and clinical study results provide further impetus for undertaking a Phase 2 trial in a targeted way that compares lasofoxifene to fulvestrant, a current, widely used injectable medication for advanced metastatic breast cancer.”

The Phase 2 trial will compare oral lasofoxifene with a Faslodex injection in advanced breast cancer patients with an ESR1 mutation. Its primary goal is to determine if lasofoxifene extends the time patients live without the disease progressing, or progression-free survival.

Linical Accelovance, a clinical development contract research organization, will be Sermonix’s research partner in the trial.

“Sermonix selected Linical Accelovance to be our clinical research development partner for this program because we are impressed with the organization’s integrated clinical trial services, as well as its operational capabilities in the development of oncology drugs,” said Miriam Portman, Sermonix’s chief operating officer.