An experimental hormone therapy pill has shown promise in extending the lives of women with tough-to-treat advanced breast cancer , a new clinical trial shows.
The drug, imlunestrant , improved progression-free survival in patients whose breast cancer was driven by the female hormone estrogen.
The drug was particularly effective in breast cancers with a mutation in the ESR1 gene, which encodes estrogen receptors, according to results published in the New England Journal of Medicine . Researchers also presented the findings at the San Antonio Breast Cancer Symposium.
Individuals with hormone receptor-positive (HR+) breast cancer are most affected by ESR1 mutations, which can cause resistance to hormone therapy.
“These promising results mean that imlunestrant is potentially another single-agent option for patients whose recurrent breast cancers harbor ESR1 mutations,” said Dr. Komal Jhaveri , section head of the Endocrine Therapy Research Group at Memorial Sloan Kettering Cancer Center.
Imlunestrant is a selective estrogen receptor degrader (SERD), designed to reduce estrogen receptor activity in cancer cells.
Researchers enrolled 874 women with advanced breast cancer whose disease had progressed despite prior treatment.
All cancers were estrogen receptor-positive. Roughly 70% of breast cancers fall into this category, according to the Cleveland Clinic.
One-third of participants received imlunestrant alone, another third received imlunestrant plus Verzenio (abemaciclib), and the remaining third received standard hormone therapy.
Verzenio is a CDK4/6 inhibitor that disrupts cancer cell division.
Among women with ESR1 mutations, imlunestrant reduced the risk of cancer progression or death by 38% compared with standard therapy.
When combined with Verzenio, the risk reduction increased to 43%.
Median progression-free survival was 9.4 months for combination therapy, compared with 5.5 months for imlunestrant alone and 3.8 months for standard therapy.
Only about 6% of women discontinued treatment due to side effects, indicating strong tolerability.
Both medications are taken orally. Imlunestrant can cross the blood-brain barrier, potentially helping treat cancers that have spread to the brain.
“Taken together, these data are encouraging and suggest imlunestrant could offer a new all-oral treatment option,” Jhaveri said.
The study was funded by Eli Lilly and Co., the developer of imlunestrant.
More information
The American Cancer Society has more on hormone-driven breast cancers.
SOURCE: San Antonio Breast Cancer Symposium, news release, Dec. 11, 2024
