The U.S. Food and Drug Administration (FDA) has approved AstraZeneca's camizestrant (Etcamah) for patients with estrogen receptor-positive (ER+), HER2-negative advanced breast cancer whose tumours carry certain ESR1 mutations.
The approval is significant because it gives patients with these mutations a targeted treatment option and adds another example of how cancer treatment is becoming increasingly guided by the genetic characteristics of individual tumours. The decision was listed among the major biotech developments of September 8 by STAT.
A Targeted Approach
ER+/HER2- breast cancer is the most common subtype of the disease, accounting for approximately 65% to 70% of all cases. ESR1 mutations are acquired mutations that can develop in patients who have been treated with endocrine therapies, such as aromatase inhibitors, and are associated with resistance to these treatments. They are estimated to occur in about 20% to 40% of patients with advanced ER+ breast cancer.
Camizestrant is a next-generation oral selective estrogen receptor degrader (SERD). Unlike older SERDs, which are administered by injection, camizestrant is a once-daily pill. It works by binding to the estrogen receptor and degrading it, thereby blocking the growth signals that drive the cancer.
Clinical Trial Results
The approval was supported by data from the Phase 3 EMBER-3 clinical trial. The study found that camizestrant demonstrated a statistically significant and clinically meaningful improvement in progression-free survival compared to fulvestrant, the current standard-of-care SERD, in patients with ESR1-mutated tumours.
In the trial, patients treated with camizestrant also showed a delay in quality-of-life deterioration, including reduced pain and improved physical functioning, when compared to those on fulvestrant.
Implications for Breast Cancer Treatment
The approval of camizestrant represents a step forward in the treatment of ER+ breast cancer. It provides an oral, once-daily option that could reduce the burden on patients compared to injectable therapies. The drug also offers a precision medicine approach, targeting patients whose tumours carry specific mutations that render them resistant to existing therapies.
The FDA's decision follows recent approvals of other targeted therapies for breast cancer, including drugs for HER2-low and HER2-positive subtypes, reflecting the growing shift toward treating cancer based on the molecular profile of the tumour.
What's Next
AstraZeneca is expected to commercialise camizestrant as Etcamah. The company has also indicated that it will continue to study the drug in earlier lines of treatment and in combination with other targeted therapies, including CDK4/6 inhibitors.