Hormone receptor-positive (HR+) breast cancer is one of the most common types of breast cancer, making up about 70% to 80% of new diagnoses. In HR+ breast cancer, tumor cells have receptors for hormones such as estrogen (ER-positive) and/or progesterone (PR-positive), which can help fuel cancer growth. Because these tumor cells rely on hormones to grow, treatments that block or lower hormone levels, known as hormone or endocrine therapies, are among the most effective treatment options available.
Hormone therapies can help lower risk of breast cancer for women who are at high risk, and also as a treatment for HR+ breast cancer. In either case, many women who use them experience side effects that affect their daily lives and overall wellbeing. Hot flashes and night sweats are among the most common challenges associated with hormone therapy treatments for HR+ breast cancer. For some, these debilitating symptoms can quickly derail a treatment plan, causing some women to skip their treatment or stop it altogether.
Typically, women with no history of breast cancer may be prescribed estrogen plus progestin hormone replacement therapy (HRT) as a way to manage these menopausal side effects. However, those with a history of HR+ breast cancer are advised against using them because they can provide fuel to hormone-sensitive tumors.
Through the OASIS-4 (NCT05587296) clinical trial, researchers are investigating whether a new non-hormonal drug called elinzanetant can provide relief to women with severe hot flashes and night sweats who are taking hormone therapy to prevent or treat HR+ breast cancer. Beyond symptom relief, researchers are hopeful this drug will help improve sleep and menopause-related quality of life.
Resetting the Brain’s Thermostat: How Elinzanetant Works
During menopause, women experience a natural drop in estrogen levels, which causes the brain’s “thermostat” to become extra sensitive. As a result, nerve cells in the brain called neurons react to this drop in estrogen by releasing two different chemical messengers that tell the brain the body is overheating. This puts the body’s thermostat into panic mode.
When the brain’s internal thermostat detects this alarm, it opens up the blood vessels to dump the heat, which is what causes feelings of warmth, flushing and sweating known as a hot flash. To prevent this process from happening, elinzanetant blocks the two chemical messengers in the brain, also called “neurokinins,” that cause the brain’s thermostat to panic. Elinzanetant’s blocking of these neurokinins helps reset the thermostat back to normal, ultimately preventing hot flashes and related sleep issues.
An Opportunity for Relief from Menopause-Related Symptoms
The OASIS-4 clinical trial is a randomized, phase 3 study that is investigating elinzanetant as a preventive treatment for hot flashes in women with or at high risk of HR+ breast cancer, who are taking hormone therapies like tamoxifen or aromatase inhibitors. OASIS-4 is the fourth study in a series that is testing this drug. Its predecessor study, OASIS-3, was a phase 3 clinical trial that investigated the efficacy of elinzanetant for a longer time of up to 52 weeks. OASIS-4 is now testing both the safety and efficacy of elinzanetant for a 52-week period, at a higher dose of 120 mg.
To date, the OASIS-4 trial has included a total of 474 women from 16 different countries. Participants are women 18-70 years old who have experienced high levels of hot flashes and night sweats (35 or more) from their hormone treatment.
The study is randomized, double-blind and placebo-controlled, which means some participants get elinzanetant while others receive a placebo (sugar pill). Neither the participants nor the doctors know which group they belong to for at least 12 weeks.
The primary study lasted a full year, and at the end, participants had the option to continue for an additional two years to evaluate long-term outcomes. Researchers found that elinzanetant cut down hot flashes and night sweats much better than the placebo. Those who took the drug slept better and felt a boost in their overall quality of life.
Elinzanetant was reported as safe and had only mild side effects that were similar to those in the placebo group. Many participants saw improvements in just one week, and these benefits lasted for a full year. In fact, over 90% of these women were so happy with the results that they chose to stay on the treatment for two more years. These promising results were presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.
One Step Closer to A Better Solution
The FDA approval of elinzanetant, which happened in October 2025, marks a major milestone in providing a non-hormonal option for women with HR+ breast cancer or those who are at a high risk for it. While elinzanetant is generally covered by insurance, including commercial plans and Medicare, patients should be aware that it often requires prior authorization to ensure it is medically necessary.
Investigators of the OASIS-4 trial are hopeful that their findings will drastically enhance the quality of life for women who are either living with HR+ breast cancer or trying to prevent it. If successful, the study could also mean a major milestone for the metastatic breast cancer (MBC) community and men with HR+ breast cancer.
Did you know? More than $287 million in Komen research grants have supported over 600 clinical trials.
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