Biopharmaceutical company AstraZeneca (LSE: AZN)) (STO: AZN) (Nasdaq: AZN) reported on Wednesday that its investigational drug camizestrant significantly improved progression-free survival (PFS) in first-line treatment of advanced hormone receptor (HR)-positive, HER2-negative breast cancer with an emergent ESR1 mutation. Results from the SERENA-6 Phase III trial demonstrated that switching to camizestrant, in combination with a cyclin-dependent kinase (CDK) 4/6 inhibitor, delayed disease progression compared to standard-of-care aromatase inhibitor therapy.

SERENA-6 is the first global, double-blind Phase III trial to use a circulating tumour DNA-guided approach to detect endocrine resistance before disease progression. Interim analysis showed a statistically significant and clinically meaningful PFS improvement, with a trend toward prolonged second progression-free survival (PFS2). The trial will continue to evaluate overall survival and other key secondary endpoints.

Camizestrant, a next-generation oral selective estrogen receptor degrader (SERD) and complete estrogen receptor antagonist, is the first in its class to demonstrate first-line benefit in combination with widely used CDK4/6 inhibitors. The safety profile was consistent with previous findings, with no new concerns identified.

Globally, HR-positive breast cancer accounts for 70% of cases, with resistance to CDK4/6 inhibitors and endocrine therapies remaining a significant challenge. ESR1 mutations are a key driver of endocrine resistance, emerging in approximately 30% of patients during first-line treatment.

AstraZeneca's broad oncology pipeline includes multiple Phase III trials evaluating camizestrant's potential across different treatment settings. Data from SERENA-6 will be presented at an upcoming medical meeting and shared with regulatory authorities.