Zytiga

Approved Uses

Zytiga is indicated for the treatment of men with advanced prostate cancer. It is specifically used for the following conditions:

• Metastatic castration-resistant prostate cancer (mCRPC): This refers to prostate cancer that has spread to other areas of the body and no longer responds to medical or surgical treatments designed to lower testosterone levels.
• Metastatic high-risk castration-sensitive prostate cancer (mCSPC): This refers to prostate cancer that has spread to other parts of the body but still responds to treatments that lower testosterone.

Combination Therapy

Zytiga is not used alone. It must be taken in combination with a corticosteroid medication, such as prednisone or methylprednisolone. This combination helps manage the cancer while reducing certain side effects associated with the treatment.

This medication is typically prescribed for patients whose cancer is considered advanced or high-risk, often after other treatments have been tried or in specific clinical situations determined by a healthcare provider.

Mechanism of Action

Prostate cancer cells often depend on male hormones, known as androgens (such as testosterone), to grow and multiply. Zytiga belongs to a group of drugs called androgen biosynthesis inhibitors.

This medication works by blocking a specific enzyme called CYP17. This enzyme is required for the body to produce androgens. Unlike some other treatments that only stop hormone production in the testes, Zytiga reduces hormone production in three different locations:

• The testes
• The adrenal glands
• The prostate tumor itself

By lowering the levels of these hormones throughout the body, Zytiga helps slow down the progression of the cancer and may shrink existing tumors. It is typically taken in combination with a corticosteroid, such as prednisone, to help maintain a balance of other necessary hormones that the medication might otherwise affect.

Common Side Effects

Many people taking Zytiga experience mild to moderate side effects. These may include:

• Joint swelling or pain
• Muscle aches
• Hot flashes
• Diarrhea
• Cough or cold-like symptoms
• Headache
• Feeling very tired or weak
• Nausea or vomiting
• Heartburn
• Skin rash
• Urinary tract infections

Serious Side Effects

Some side effects can be severe and require immediate medical attention. Contact a healthcare provider right away if you experience:

• Liver problems: Symptoms include yellowing of the skin or eyes (jaundice), dark-colored urine, or severe nausea and vomiting.
• Heart issues: This may include chest pain, shortness of breath, rapid or irregular heartbeat, and swelling in the feet, ankles, or legs.
• High blood pressure: Blood pressure should be monitored frequently during treatment.
• Low potassium levels: Signs include muscle weakness, leg cramps, or a fluttering feeling in the chest.
• Adrenal gland problems: Symptoms may include dizziness, loss of appetite, or unexplained weight loss.
• Bone fractures: An increased risk of bone thinning or breaks may occur during treatment.

Mineralocorticoid Excess

Zytiga may cause high blood pressure (hypertension), low potassium levels (hypokalemia), and fluid retention (edema). These conditions result from increased mineralocorticoid levels caused by the medication. To manage these risks, Zytiga must be administered in combination with a corticosteroid, such as prednisone or prednisolone. Monitoring of blood pressure and potassium levels is typically required before and during treatment.

Hepatotoxicity

Severe liver toxicity, including cases of liver failure and death, has been observed in patients taking this medication. Liver function tests, including serum transaminases (ALT and AST) and bilirubin, are usually performed before starting treatment, every two weeks for the first three months, and monthly thereafter. Dose reductions or discontinuation may be necessary if liver enzyme levels become significantly elevated.

Adrenocortical Insufficiency

Adrenal gland problems can occur, particularly if the patient experiences medical stress or if the prescribed corticosteroid is discontinued or reduced. Healthcare providers may monitor for signs of adrenal insufficiency, such as low blood pressure, dizziness, or electrolyte imbalances. Increased corticosteroid doses may be necessary during periods of physical stress.

Cardiovascular Events

Safety has not been established in patients with significant heart conditions, such as severe or unstable angina, recent heart attack, or heart failure. The drug should be used with caution in individuals with a history of cardiovascular disease, as fluid retention and hypertension associated with the medication can strain the heart.

Embryo-Fetal Toxicity and Handling

Zytiga is not indicated for use in women and can cause fetal harm if taken during pregnancy. Due to the risk of absorption through the skin, women who are pregnant or who may become pregnant should not handle the tablets without protective gloves.

Pregnancy and Fetal Risk

Zytiga is not indicated for use in women. Clinical data suggests that exposure to this medication during pregnancy can cause significant harm to a developing fetus or lead to birth defects. The medication can be absorbed through the skin; therefore, women who are pregnant or who may become pregnant are advised to avoid handling the tablets. If handling is required, the use of protective gloves is recommended.

Precautions for Men

Because Zytiga may be present in semen, men with female partners of reproductive potential typically use effective contraception during and after treatment. This often includes:

• Using a condom along with another effective method of birth control during sexual activity.
• Maintaining these contraceptive practices for 3 weeks following the final dose of the medication.

Breastfeeding

Zytiga is not for use in women, and there is no information available regarding its safety during breastfeeding. It is unknown if the drug passes into human breast milk or what effects it may have on a nursing infant.

Dosage Forms

Zytiga is available in the following oral forms:

• Tablets
• Film-coated tablets

This medication is administered by mouth. It must be taken on an empty stomach, as consuming food with the medication can significantly increase the amount of the drug absorbed by the body, potentially leading to increased side effects.

FDA Approval History

The U.S. Food and Drug Administration (FDA) first approved Zytiga (abiraterone acetate) in April 2011. Initially, it was approved for patients with metastatic castration-resistant prostate cancer who had already undergone chemotherapy. Its use was later expanded in 2012 to include patients who had not yet received chemotherapy, and in 2018 for those with metastatic high-risk castration-sensitive prostate cancer.

Approved Indications

Zytiga is approved for use in combination with prednisone for the treatment of:

• Metastatic castration-resistant prostate cancer (mCRPC).
• Metastatic high-risk castration-sensitive prostate cancer (mCSPC).

Safety and Monitoring

While Zytiga does not have a Boxed Warning or a Risk Evaluation and Mitigation Strategy (REMS) program, the FDA requires specific monitoring due to risks of hepatotoxicity (liver toxicity), hypertension, and hypokalemia. Patients must have their liver function and blood pressure monitored regularly while taking this medication.

Cost Factors

The price of Zytiga can vary based on several factors, including the patient's insurance plan, the pharmacy used, and the prescribed dosage. Because it is a specialty medication, out-of-pocket costs can be significant.

Generic Availability

A generic version of Zytiga, known as abiraterone acetate, is available. Generic medications contain the same active ingredients as brand-name drugs but are typically much less expensive. Many insurance plans may require the use of the generic version to manage treatment costs.

Insurance and Medicare Coverage

Most private insurance plans and Medicare Part D provide coverage for abiraterone. However, the drug is often placed on a higher cost-sharing tier, which may require patients to pay a percentage of the cost (coinsurance) rather than a fixed copay. It is advisable to check with the insurance provider for specific coverage details and any prior authorization requirements.

Financial Assistance Programs

Several options may help reduce the cost of Zytiga:

• Manufacturer Support: The drug's manufacturer may offer copay cards or assistance programs for eligible patients with commercial insurance.
• Patient Assistance Foundations: Independent non-profit organizations may provide financial aid to help cover the cost of cancer treatments for those who qualify.
• Medicare Extra Help: Individuals with Medicare who have limited income and resources may qualify for assistance with their prescription drug costs.