Camizestrant Approved for Metastatic HR-Positive Breast Cancer
On Sept. 4, the U.S. Food and Drug Administration (FDA) approved camizestrant (brand name: Etcamah). The medicine is to be used in combination with a CDK4/6 inhibitor to treat hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer that developed an ESR1 mutation after at least six months of treatment with an aromatase inhibitor and a CDK 4/6 inhibitor.
Locally advanced breast cancer is breast cancer that has spread to tissue near the breast, but not to parts of the body away from the breast. Metastatic breast cancer is breast cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Doctors will use a liquid biopsy, a type of blood test that looks for circulating tumor DNA (ctDNA), to detect ESR1 mutations. The liquid biopsy test is done every three months while a person is taking an aromatase inhibitor and a CDK4/6 inhibitor.
The approval was based on results from the SERENA-6 study. It found that — after an ESR1 mutation was detected — switching from an aromatase inhibitor and a CDK4/6 inhibitor to camizestrant and a CDK4/6 inhibitor lowered the risk of the cancer growing. Progression-free survival (how long people live without cancer growing) was 16 months for people who switched to camizestrant versus nine months for people who stayed on an aromatase inhibitor.
See camizestrant prescribing information.
How camizestrant works
Camizestrant is a type of hormonal therapy medicine called a selective estrogen receptor degrader (SERD). SERDs, like selective estrogen receptor modulators (SERMs), block estrogen from attaching to cancer cells in the breast. By sitting in the estrogen receptors in and on hormone receptor-positive breast cancer cells, SERDs stop estrogen from signaling the cells to grow. SERDs also reduce the number of estrogen receptors and change the shape of the receptors so they don’t work as well.
Camizestrant is a pill taken by mouth. The recommended dose is 75 mg once a day, with or without food, along with a CDK4/6 inhibitor. You should take camizestrant at approximately the same time each day. Swallow the tablets whole; don’t cut, crush, or chew them.
Camizestrant side effects
Like most cancer medicines, camizestrant can cause side effects. The most common side effects seen in the SERENA-6 study were low white blood cell counts, anemia, vision problems, and fatigue.
For some people, camizestrant can cause serious side effects, including heart problems.
Camizestrant can cause bradycardia, which is a slower-than-normal heart rate. Because it’s taken with a CDK4/6 inhibitor, the medicine also can cause a heart issue called QT interval prolongation. This means the heart muscle takes longer than usual to contract and relax. If camizestrant and a CDK4/6 inhibitor cause both bradycardia and QT interval prolongation, your heart may contract and relax even more slowly, which can cause heart failure.
When taken with Kisqali (chemical name: ribociclib), camizestrant can cause Torsades de Pointes. This is an irregular, very fast heart rate that can cause fainting, dizziness, or a sudden heart attack.
Tell your doctor right away if you have a change in heartbeat, including a fast or irregular heartbeat, or if you feel dizzy or like you might faint. You have an electrocardiogram before you start camizestrant, then once a week for the first two weeks of treatment, and then periodically while you’re taking the medicine. (An electrocardiogram, or ECG or EKG, measures how fast or slow your heart is beating).
There are certain medicines you shouldn’t take if you’re taking camizestrant:
Strong CYP3A inhibitors, because they increase the effects of camizestrant. This class of medicines includes antifungal medicines such as Nizoral (chemical name: ketoconazole).
Strong or moderate CYP3A inducers, because they decrease the effects of camizestrant. This class of medicines includes Rifamate (chemical name: rifampin), an antibiotic used to treat tuberculosis.
CYP2C9 substrates, because camizestrant can increase their effects. This class of medicines includes anticoagulants, like warfarin; NSAID pain relievers like aspirin, naproxen, and ibuprofen; and high blood pressure medicines like losartan.
CYP2C19 substrates, because camizestrant can increase their effects. This class of medicines includes proton pump inhibitors like omeprazole and pantoprazole, and antidepressants like amitriptyline and Celexa (chemical name: citalopram).
Medicines that treat improper beating of the heart, whether too fast or too slow. These medicines include Cordarone (chemical name: amiodarone), Norpace (chemical name: disopyramide), procainamide, Quinaglute (chemical name: quinidine), and Betapace (chemical name: sotalol).
Medicines known to cause heart rhythm problems, including beta blockers, digoxin, and certain opioids, like propofol or fentanyl.
Camizestrant also can harm a fetus. You shouldn’t take camizestrant if you’re pregnant, trying to get pregnant, or if there’s any chance that you could be pregnant. Anyone who could become pregnant should use an effective non-hormonal type of birth control while taking camizestrant and for four weeks after the last dose. Ask your doctor which type of non-hormonal birth control would be best for you.
You also shouldn’t breastfeed while taking camizestrant and for one week after the last dose.
If you’re a man taking camizestrant and have a partner who can become pregnant, your partner should use birth control while you’re taking camizestrant and for one week after the last dose.
Paying for camizestrant
The cost of camizestrant may vary. The price you’ll pay depends on your health insurance provider and plan, where you live, and the pharmacy you use.
Note: Your insurance company may require you to get prior authorization before covering camizestrant.
AstraZeneca, the company that makes camizestrant, has the ACCESS 360 Program that may be able to help you with the cost of camizestrant. You can also call 1-844-275-2360, Monday to Friday, 8 a.m.–6 p.m. ET, or email Access360@AstraZeneca.com.
Learn more about financial assistance and tips for lowering medicine costs.