AstraZeneca Reports Phase 3 Success for Oral SERD in Breast Cancer, Eyeing $5B Peak Sales

AstraZeneca has announced a significant advancement in its breast cancer treatment pipeline, reporting positive results from a phase 3 trial of its oral selective estrogen receptor degrader (SERD), camizestrant. The interim analysis revealed that the drug met its primary endpoint of improved progression-free survival (PFS) in patients with hormone receptor-positive, HER2-negative breast cancer.

Trial Design and Results

The phase 3 trial employed a novel design to address an unmet need in breast cancer treatment. Patients initially received a standard-of-care aromatase inhibitor along with a CDK4/6 inhibitor as first-line therapy. Circulating tumor DNA was monitored to detect ESR1 mutations, which are found in approximately 5% of patients at metastatic diagnosis and increase to about 40% by the end of first-line treatment. Upon detection of an ESR1 mutation before disease progression, patients were switched to camizestrant while continuing their CDK4/6 inhibitor.

Dr. Susan Galbraith, Executive Vice President of Oncology R&D at AstraZeneca, highlighted the significance of this approach, stating, "The trial was designed to show if camizestrant can extend the benefit of first-line therapy for those patients [with ESR1 mutations]."

While the study achieved its primary PFS endpoint, data on time to second disease progression (PFS2) and overall survival (OS) were not mature at the time of the interim analysis. AstraZeneca noted a trend toward improvement in PFS2 but did not comment further on OS data. Importantly, no new safety concerns were identified, and treatment discontinuations were reported to be very low.

Market Potential and Competition

AstraZeneca CEO Pascal Soriot has set an ambitious peak sales target of over $5 billion for camizestrant, positioning it as a potential new backbone therapy in breast cancer treatment. However, the company faces stiff competition in the oral SERD market.

Eli Lilly recently reported phase 3 data on its oral SERD imlunestrant in patients who progressed on an aromatase inhibitor. Meanwhile, Roche is expected to present data on its candidate, giredestrant, from mid-2025 onward.

AstraZeneca believes camizestrant's safety profile and combinability with other drugs will set it apart from competitors. Dr. Galbraith emphasized, "The safety profile that we're seeing with camizestrant leads to an extremely low discontinuation rate, very low rates of these GI side effects, which I think is important, particularly when you go into the earlier lines of therapy. People want to stay on the drug for a long period of time."

With these promising results, AstraZeneca plans to share the interim phase 3 data with global regulatory authorities, marking a significant step forward in the development of oral SERDs for breast cancer treatment.