What Is Inluriyo, and Why Does It Matter?
Inluriyo (imlunestrant) is a new oral treatment for certain types of locally advanced or metastatic breast cancer that has progressed after at least one round of hormone therapy. The FDA has approved it for people whose cancer is estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-), and has a faulty ESR1 gene.
About half of the people with ER+, HER2- locally advanced or metastatic breast cancer develop ESR1 mutations after taking aromatase inhibitors, a commonly used hormonal treatment. These ESR1 mutations make the tumor cells more responsive to hormones like estrogen, promoting their growth, spread, and making hormone therapy less effective over time.
Inluriyo works by blocking and breaking down overactive estrogen receptors – proteins that help some breast cancers (including those with ESR1 mutations) grow. By slowing down tumor growth, this medicine offers a new option for people whose cancer has progressed despite being treated with hormone therapy. Taken as a once-daily pill, this medicine may provide a simpler and more convenient way for treating advanced breast cancer than injection-based therapies.
Why Was It Approved?
Inluriyo was approved because it worked better than standard hormone treatments at slowing tumor growth in people with ER+, HER2-, ESR1-mutated breast cancer who had already tried hormone therapy.
In a study involving 256 patients, those who took this medicine went longer without their cancer getting worse than those who took other hormone therapies. On average, cancer stayed under control for about 5.5 months with Inluriyo, versus nearly four months with the other treatments. About twice the number of patients on this medicine, compared with those on other standard treatments (14.3% vs. 7.7%), saw their tumors shrink or improve. After about 19 months, the average time spent without disease progression was also longer with Inluriyo than with standard therapy (7.9 months vs. 5.4 months).
The most common side effects included low levels of red blood cells, white blood cells, and platelets; low levels of calcium; muscle or joint pain; increased levels of liver enzymes, cholesterol, and triglycerides; tiredness; diarrhea; nausea; constipation; and abdominal (belly) pain. Serious side effects involving fluid buildup around the lungs were uncommon, and life-threatening complications such as heart attack, heart failure, and internal bleeding were rarely seen.
What Do I Need to Know?
Inluriyo is a 400-mg. tablet to be taken once a day on an empty stomach – either two hours before or one hour after eating. Do not chew, crush, or split the tablets before swallowing them. If you miss a dose by six hours or more or vomit after taking it, skip that dose and take your next one at the usual time the next day.
This medicine can raise your cholesterol and triglyceride levels, so your health care provider will check them before and during treatment. Inluriyo can also interact with other medicines, especially those that affect how your liver processes medicines. Be sure to let your health care provider know if you have liver disease or have had it before, and about all the medicines you take, including over-the-counter products, herbal treatments, and supplements.
Tell your health care provider if you are pregnant or planning pregnancy, as this medicine can harm an unborn baby and may affect your ability to have children. If you can become pregnant, use birth control during the treatment and for a week after your last dose. Male patients with partners who can become pregnant should use birth control for the same duration. Breastfeeding is also not recommended during this time.
This medicine is expected to be available in the U.S. within a few weeks of approval.