Imlunestrant (Inluriyo), is a daily oral SERD (selective estrogen receptor degrader) for adults with advanced/metastatic ESR1-mutated, ER+/HER2- breast cancer that has progressed after endocrine therapy.
Imlunestrant is a next generation, brain penetrant, oral selective estrogen receptor degrader that delivers continuous ER inhibition even in cancers with mutations in the gene encoding ESR 1.
Imlunestrant (brand name Inluriyo) is an FDA-approved oral hormonal therapy for adults with estrogen receptor (ER)-positive, HER2-negative advanced or metastatic breast cancer.
It works by degrading estrogen receptors to stop cancer growth, showing superior PFS compared to standard treatments.
Indications: Treatment of ER-positive, HER2-negative, ESR1-mutated advanced or metastatic breast cancer.
Approval Basis: Approved based on the EMBER-3 trial, which showed improved progression-free survival for ESR1-mutated tumors.
Side Effects: The most common side effects include fatigue, diarrhea, nausea, abdominal pain, back pain, decreased appetite, joint pain, neutropenia, rash, and vomiting.
Administration: It is taken as an oral pill, designed to be a more comfortable alternative to intramuscular injections like fulvestrant.
Efficacy: The drug is designed for patients who have developed resistance to prior endocrine therapies.
Availability: Approved in 2025, it is a new option often used in combination with CDK4/6 inhibitors such as abemaciclib. Imlunestrant showed a 38% reduction in risk of progression or death compared to standard hormone therapies in ESR1-mutated cases.
It acts as a “next-generation” drug designed to work even when tumors have developed resistance to conventional endocrine therapy.
Among patients with ER positive, HER2 negative advanced breast cancer Imlunestrant led to significantly longer progression free survival than standard therapy among those with ESR one mutations but not in the overall population.
The combination of Imlunestrant and abemaciclib significantly improved progression free survival as compared with Imlunestrant, regardless of the ESR 1 mutation status.
It is prescribed for patients who have an ESR1 gene mutation and whose disease has progressed after at least one previous line of endocrine therapy.
It binds to estrogen receptors on cancer cells, physically blocking estrogen from attaching and promoting cell growth, while also physically degrading the receptor itself.
It is uniquely effective against cancers with ESR1 mutations, which often develop resistance to standard treatments like aromatase inhibitors.
Common side effects include fatigue, nausea, diarrhea, musculoskeletal pain, and abdominal pain.
It can cause increased liver enzymes (AST/ALT), increased cholesterol/triglycerides, and decreased hemoglobin or calcium levels.Interactions.
Patients should avoid CYP3A4 inducers (such as the antibiotic rifampin, anti-seizure medication carbamazepine, or St. John’s wort) as they can decrease the effectiveness of the drug.
EMBER-3 trial, imlunestrant was shown to significantly increase progression-free survival compared to older standard hormonal therapies (such as fulvestrant or exemestane).