Selective estrogen receptor degraders (SERDs)
- Medical Review: Claire Smith, MD
Selective estrogen receptor degraders (SERDs) are medicines that attach tightly to, and break down, estrogen receptors on hormone receptor-positive breast cancer cells. This prevents estrogen from signaling the cancer cells to grow.
SERDs are a type of hormonal therapy, also known as endocrine therapy.
How SERDs work
Selective estrogen response degraders work by attaching to the estrogen receptors on breast cancer cells. When this happens, SERDs:
- Block estrogen from helping breast cancer to grow
- Weaken and break down estrogen receptors
With fewer receptors, the breast cancer cells can’t receive growth signals from estrogen.
SERDs used in breast cancer treatment
Three SERDs are FDA approved to treat advanced or metastatic breast cancer:
- Fulvestrant (Faslodex) was approved in 2002 and is given as an injection in the buttock muscle. It can be used alone or combined with other treatments.
- Elacestrant (Orserdu) was approved in 2023 for people with metastatic breast cancer that stopped responding to other hormonal therapies. The cancer also has to test positive for a mutation in a gene called ESR1. Elacestrant is taken as a pill.
- Imlunestrant (Inluriyo) was approved in 2025 for people with metastatic breast cancer that tests positive for a mutation in the ESR1 gene. Imlunestrant is taken as a pill.
All three treatments are approved for use in postmenopausal women and men. Premenopausal women can take fulvestrant if they also take ovarian suppressing medicine at the same time.
SERD side effects
Common side effects of selective estrogen response degraders can include:
- Hot flashes and night sweats
- Nausea and vomiting
- Fatigue
- Headache
- Joint, bone, or muscle pain
- Loss of appetite
For more detailed information on each medicine’s side effects, visit the Elacestrant and Fulvestrant pages.
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