06/04/2025 | News release | Distributed by Public on 06/04/2025 02:44
In a major development unveiled at the 2025 ASCO Annual Meeting, AstraZeneca's camizestrant, an investigational oral SERD (selective estrogen receptor degrader), has demonstrated remarkable efficacy in delaying disease progression in patients with hormone receptor-positive (HR-positive), HER2-negative advanced breast cancer, the most common subtype of breast cancer.
The findings stem from the SERENA-6 trial, which aimed to intercept cancer progression earlier than current treatment protocols by identifying ESR1 mutations before clinical symptoms appear. These mutations, which alter the estrogen receptor and drive resistance to standard hormone therapy, typically emerge after initial treatment with aromatase inhibitors and CDK4/6 inhibitors.
The SERENA-6 studies enrolled 3,256 participants with advanced HR-positive, HER2-negative breast cancer. Approximately 550 of them developed ESR1 mutations during first-line treatment, which were detected via liquid biopsies blood tests that identify tumor DNA fragments.
Out of this group, 315 patients were randomized: one half continued on aromatase inhibitors, while the other switched to camizestrant while both groups remained on CDK4/6 inhibitors. Patients who transitioned to camizestrant saw a 56% reduction in the risk of disease progression or death, with median progression-free survival increasing to 16 months, compared to 9.2 months for those on standard care.
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ESR1 mutations are a well-known mechanism of resistance in HR-positive breast cancer. They alter the shape of the estrogen receptor, keeping it permanently "on" even in the absence of estrogen. Camizestrant, unlike aromatase inhibitors, degrades the receptor entirely, addressing the mutation head-on. This targeted approach is why oncologists view camizestrant as a potential game-changer in breast cancer care.
"This early switch approach, before we see progression in imaging, allows us to stay ahead of the curve," said Dr. Eleonora Teplinsky of Valley-Mount Sinai Comprehensive Cancer Care during an ASCO press briefing.
Not only did camizestrant delay disease progression, but it also helped maintain quality of life for longer periods of time. Importantly, less than 2% of patients discontinued treatment due to side effects, which remained consistent with previous trials, according to AstraZeneca.
Experts believe that regulatory approval of camizestrant would not only add a valuable tool to oncologists' arsenal but also reshape clinical guidelines. Current ESR1 testing occurs after disease progression; camizestrant's success suggests that serial monitoring and early switching could soon become standard.
AstraZeneca is also investigating whether camizestrant could replace aromatase inhibitors entirely in first-line settings, and additional trials are underway in early-stage breast cancer.
In a landscape where resistance to hormone therapy often marks the beginning of decline, camizestrant offers new hope pushing the boundaries of precision oncology and redefining care for thousands of patients.
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