Last updated: September 23, 2026
Camizestrant (Etcamah, AZD9833) is a next-generation, once-daily, oral selective estrogen receptor degrader (SERD), developed by AstraZeneca. It was granted FDA accelerated approval on September 4, 2026, in combination with a CDK4/6 inhibitor (abemaciclib, palbociclib, or ribociclib), for adults with HR-positive, HER2-negative locally advanced or metastatic breast cancer upon detection of an ESR1 mutation during aromatase-inhibitor + CDK4/6-inhibitor therapy, using an FDA-authorized ctDNA (blood) test.
Mechanism of action:Camizestrant blocks and degrades the estrogen receptor (ER) that drives HR-positive breast cancer. Crucially, unlike aromatase inhibitors, it remains active against ESR1-mutant receptor — a common driver of acquired resistance to first-line endocrine therapy. Taken by mouth once daily.
Regulatory status:FDA accelerated approval September 4, 2026 (brand name Etcamah) for emergent-ESR1-mutation HR+/HER2- advanced breast cancer with a CDK4/6 inhibitor — the first ctDNA-guided treatment-switch approval — based on the Phase 3 SERENA-6 trial. Early-breast-cancer and novel-combination settings are investigational (trials ongoing, not FDA-approved). As an accelerated approval, continued approval may be contingent on confirmatory trials.
Most hormone-receptor-positive (HR+) breast cancers are first treated with an aromatase inhibitor plus a CDK4/6 inhibitor like palbociclib. Over time, many tumors develop a mutation in a gene called ESR1 that lets them keep growing despite the aromatase inhibitor — and this mutation often shows up in a blood test (ctDNA) before the cancer visibly grows on scans.
Camizestrant is the first drug approved to act on that early warning. Instead of waiting for the cancer to progress on imaging, treatment switches to camizestrant (with the CDK4/6 inhibitor) the moment an ESR1 mutation is detected in the blood. Because camizestrant is a next-generation oral SERD that still works against the mutant receptor, it can control the cancer that the aromatase inhibitor no longer can.
What the trial showed. In the Phase 3 SERENA-6 study, making that ctDNA-guided switch to camizestrant delayed cancer progression to a median of 16.8 months versus 9.2 months for staying on the aromatase inhibitor — a 56% reduction in the risk of progression or death. It is a once-daily pill.
Camizestrant has 1 FDA-approved indication, anchored in the emergent-ESR1-mutation, ctDNA-guided-switch setting.
Emergent-ESR1-Mutation HR+/HER2- Advanced Breast Cancer, with a CDK4/6 Inhibitor (SERENA-6)
★ First-in-Paradigm: ctDNA-Guided Treatment Switch Before Radiographic Progression
Other oral SERDs — elacestrant (Orserdu), giredestrant, imlunestrant — are used mainly after the cancer has grown on scans in ESR1-mutant disease. Camizestrant's approval is different: it acts on a molecular signal in the blood — an ESR1 mutation emerging on ctDNA during first-line AI + CDK4/6 therapy — and switches treatment before radiographic progression. It is the first therapy approved for this ctDNA-guided early-switch paradigm.
The rationale: ESR1 mutations are a leading cause of acquired endocrine resistance and typically appear in ctDNA months before imaging changes. Intercepting resistance at that point — with a SERD that retains activity against the mutant receptor — extended progression-free survival in SERENA-6. The trade-off is the need for serial ctDNA monitoring to detect the mutation, and camizestrant's own side-effect profile (below).
Curated set of recruiting interventional camizestrant / Etcamah / AZD9833 trials in the ClinTrialFinder corpus as of September 2026 (5 recruiting interventional trials), grouped by setting. The registrational SERENA-6 trial that supported the September 2026 approval is described above as the approval basis; the trials below are those currently recruiting.
The estrogen receptor (ER) is the growth driver in HR-positive breast cancer. Aromatase inhibitors lower estrogen, but tumors frequently escape by acquiring ESR1 mutations that keep the receptor active without estrogen. A selective estrogen receptor degrader (SERD) both blocks the receptor and targets it for destruction. Camizestrant is a next-generation, orally-bioavailable SERD designed to retain potent activity against the mutant ER, which is why it can control disease that has become resistant to aromatase inhibitors. Its approved use ties this mechanism to a diagnostic strategy — serial ctDNA testing to catch the ESR1 mutation as it emerges — enabling a switch to camizestrant before the cancer progresses on scans.
On-Mechanism Endocrine + Agent-Specific Effects
As an estrogen-blocking therapy, camizestrant carries on-mechanism effects such as hot flashes, fatigue, and arthralgia (joint aches). Notably for this agent, trials have observed sinus bradycardia (a slowed heart rate) and visual disturbances such as photopsia (flashes of light), which are monitored during treatment. It is a once-daily oral therapy given with a CDK4/6 inhibitor, whose own effects (e.g., low blood counts) also apply. Refer to the FDA prescribing information for the complete, camizestrant-specific safety profile, monitoring, and dose-modification guidance.
These considerations are general to the drug class and this agent and are not a substitute for the approved label. Your oncology team manages ctDNA monitoring, cardiac and visual monitoring, and any dose adjustments based on the official prescribing information and your individual situation.
Camizestrant joins a competitive oral-SERD field for endocrine-resistant HR+/HER2- breast cancer: elacestrant (Orserdu), already FDA-approved for ESR1-mutant disease after progression; giredestrant (GDC-9545), another oral SERD with a curative-setting Phase 3 program; and imlunestrant. Camizestrant's distinct niche is the ctDNA-guided early-switch setting with a CDK4/6 inhibitor. For the CDK4/6 backbone these regimens build on, see the CDK4/6 Inhibitors hub; for the disease-level view, see the breast cancer trials page.
What is camizestrant (Etcamah) and how does it work?
Camizestrant (Etcamah, AZD9833) is a next-generation, once-daily, oral selective estrogen receptor degrader (SERD) from AstraZeneca. It blocks and degrades the estrogen receptor that drives HR-positive breast cancer, and — unlike aromatase inhibitors — it remains active against ESR1-mutant receptor, a common cause of acquired endocrine resistance. It is taken by mouth once daily, with a CDK4/6 inhibitor.
What is camizestrant FDA-approved for?
On September 4, 2026, the FDA granted accelerated approval to camizestrant with a CDK4/6 inhibitor (abemaciclib, palbociclib, or ribociclib) for adults with HR-positive, HER2-negative locally advanced or metastatic breast cancer upon detection of an ESR1 mutation during aromatase-inhibitor + CDK4/6-inhibitor therapy, using an FDA-authorized ctDNA test. It is the first approval for a ctDNA-guided treatment switch.
What is the ctDNA-guided switch, and what did SERENA-6 show?
ESR1 mutations often emerge in the blood (ctDNA) during AI + CDK4/6 therapy and signal developing resistance before the tumor grows on scans. SERENA-6 tested switching to camizestrant + the CDK4/6 inhibitor at that molecular signal. Median progression-free survival was 16.8 months with the switch versus 9.2 months continuing the aromatase inhibitor — a 56% reduction in the risk of progression or death.
How is camizestrant different from other oral SERDs like elacestrant?
Camizestrant, elacestrant (Orserdu), giredestrant, and imlunestrant are all oral SERDs for ESR1-mutant / endocrine-resistant HR+/HER2- breast cancer. Camizestrant's distinguishing approval is for the ctDNA-guided early-switch setting — used when an ESR1 mutation is first detected in the blood during first-line AI + CDK4/6 therapy — rather than only after radiographic progression. Selection among SERDs is individualized with your oncologist.
Is camizestrant being studied in earlier breast cancer?
Yes. Recruiting trials include camizestrant in ER-positive, HER2-negative EARLY (non-metastatic) breast cancer after at least 2 years of adjuvant endocrine therapy (NCT05774951, Phase 3); camizestrant + ribociclib (NCT07195227 Phase 2; NCT07647328 Phase 3b); and saruparib (AZD5305, PARP1-selective) + camizestrant in advanced breast cancer (NCT06380751, Phase 3).
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