How Orserdu Works Against Breast Cancer
Orserdu (elacestrant) treats ER-positive, HER2-negative advanced or metastatic breast cancer in postmenopausal women or adult men with ESR1 mutations, detected by an FDA-approved test. It blocks estrogen receptors on cancer cells, preventing estrogen from fueling tumor growth.[1][2]
Mechanism of Action
Orserdu is a selective estrogen receptor degrader (SERD). It binds to estrogen receptors (ER), changes their shape, and triggers their degradation inside cells. This cuts off estrogen signaling that drives cancer proliferation, unlike selective estrogen receptor modulators (SERMs) that only partially block the receptor.[1][3]
Who Gets Prescribed Orserdu
Approved for patients whose cancer progressed after at least one line of endocrine therapy, often with prior CDK4/6 inhibitors like palbociclib. ESR1 mutations, which cause resistance to standard treatments like tamoxifen or aromatase inhibitors, make tumors responsive to Orserdu.[1][2]
How It's Taken and Dosing
Patients take 345 mg orally once daily with food, continuing until disease progression or unacceptable toxicity. No dose adjustments for mild liver impairment, but it's avoided in moderate/severe cases.[1][4]
Clinical Trial Results
In the EMERALD trial, Orserdu extended progression-free survival to 3.8 months versus 1.9 months with standard endocrine therapy in ESR1-mutated patients (hazard ratio 0.55). Overall response rates were 12.4% versus 7.9%, with benefits in bone and soft tissue.[2][5]
Common Side Effects
Fatigue (40%), nausea (35%), decreased appetite (25%), and vomiting (20%) occur most often. Serious risks include elevated cholesterol, liver enzyme increases, and embryo-fetal toxicity—effective contraception is required.[1][4]
Comparison to Fulvestrant
Both are SERDs, but Orserdu is oral while fulvestrant requires intramuscular injections. Orserdu showed superior progression-free survival in ESR1-mutated cases (3.8 vs. 1.9 months), positioning it as a next-line option post-CDK4/6 therapy.[2][5]
Patent Status and Availability
Stemline Therapeutics (Menarini Group) holds U.S. patents for Orserdu through 2037-2040, covering composition and use in ESR1-mutated breast cancer. No generic challenges listed yet.6
[1]: https://www.accessdata.fda.gov/drugsatfda_docs/label/2023/217358s000lbl.pdf
[2]: https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-elacestrant-er-positive-her2-negative-esr1-mutated-advanced-or-metastatic-breast-cancer
[3]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10491943/
[4]: https://www.orserdu.com/
[5]: https://www.nejm.org/doi/full/10.1056/NEJMoa2305044