In a significant development for the treatment of estrogen receptor (ER)-positive, HER2-negative breast cancer, camizestrant has shown to significantly improve progression-free survival (PFS) compared to fulvestrant. This conclusion comes from the phase 2 SERENA-2 trial, which involved 240 patients with advanced ER-positive, HER2-negative breast cancer who had experienced disease progression on at least one line of endocrine therapy but had not received more than one previous endocrine therapy in the advanced setting.
Patients were randomly assigned to receive either fulvestrant at 500 mg or camizestrant at 75 mg, 150 mg, or 300 mg. Notably, the 300 mg arm was closed early, and no efficacy analysis was performed for this group. The median follow-up periods were 16.6 months for the 75 mg camizestrant group, 16.3 months for the 150 mg group, and 14.7 months for the fulvestrant group.
Key findings include:
- Objective response rates were 12% for fulvestrant, 16% for the 75 mg camizestrant group, and 17% for the 150 mg group.
- Median PFS was 3.7 months with fulvestrant, 7.2 months with the 75 mg dose of camizestrant, and 7.7 months with the 150 mg dose.
- Overall survival data were not mature at the time of data cutoff, with the median overall survival in the fulvestrant arm being 20.5 months and not reached in the camizestrant arms.
Regarding safety, treatment-related adverse events (TRAEs) were reported in 18% of fulvestrant recipients, 53% of the 75 mg camizestrant group, and 67% of the 150 mg group. Importantly, there were no treatment-related deaths, and the rate of grade 3-4 TRAEs was low across the camizestrant groups.
The researchers concluded that camizestrant at 75 and 150 mg doses offers a significant benefit in progression-free survival over fulvestrant, supporting its further development for treating ER-positive, HER2-negative breast cancer.
