Krystexxa

Chronic Gout Management

Krystexxa is used for the treatment of chronic gout in adults whose condition is considered refractory. This means the gout has not responded to or cannot be controlled by conventional medications that lower uric acid levels.

Gout is a form of arthritis caused by an accumulation of uric acid crystals in the joints and surrounding tissues. When these levels remain high despite standard treatment, it can lead to frequent flares and the formation of tophi, which are visible lumps of crystals under the skin.

Healthcare providers may prescribe this medication to achieve the following:

• Reduce high blood levels of uric acid.
• Decrease the frequency and severity of gout attacks.
• Help dissolve uric acid crystal deposits in the joints and soft tissues.

Krystexxa is not recommended for individuals who have high uric acid levels but do not experience symptoms, a condition known as asymptomatic hyperuricemia.

Breaking Down Uric Acid

Krystexxa is a type of medication known as a uric acid-specific enzyme. It works by changing uric acid into a different substance called allantoin. Unlike uric acid, which can build up and form crystals in the joints and tissues, allantoin is highly soluble and is easily filtered out of the body by the kidneys.

Targeting Gout Crystals

Gout is caused by high levels of uric acid in the blood, a condition called hyperuricemia. When these levels remain high for a long time, the acid can turn into hard crystals. These crystals lead to the pain, swelling, and joint damage associated with gout. Krystexxa helps by:

• Lowering blood levels: It rapidly reduces the amount of uric acid circulating in the bloodstream.
• Dissolving deposits: By keeping uric acid levels very low, the medication allows the body to gradually dissolve existing crystal deposits, also known as tophi.
• Preventing new crystals: Maintaining low levels helps prevent new crystals from forming in the joints.

This medication is typically used for people with chronic gout whose symptoms have not improved with other standard treatments. Because humans do not naturally produce the enzyme needed to break down uric acid this way, Krystexxa provides a supplemental version of the enzyme to perform this function.

Common Side Effects

Many people experience an increase in gout flares during the first few months of treatment as the body begins to clear uric acid. Other common side effects include:

• Nausea
• Bruising or skin redness
• Sore throat
• Constipation
• Chest pain
• Vomiting

Serious Side Effects

Krystexxa can cause serious infusion reactions or allergic reactions. Seek emergency medical care if you experience:

• Wheezing or trouble breathing
• Swelling of the face, lips, or tongue
• Severe rash or hives
• Chest discomfort
• Flushing or redness of the skin
• Dizziness or fainting

This medication may also worsen congestive heart failure. Notify your doctor if you experience new or worsening shortness of breath or swelling in your lower legs or feet.

Individuals with a rare genetic condition called G6PD deficiency are at risk for serious blood problems, such as hemolysis or methemoglobinemia, while using this medication. Healthcare providers typically test for this condition before starting treatment.

Boxed Warning: Infusion Reactions and Anaphylaxis

Serious and potentially life-threatening allergic reactions, including anaphylaxis and infusion reactions, can occur during or after a Krystexxa treatment. These reactions are more likely to happen if uric acid levels in the blood begin to rise. Healthcare providers typically administer medications such as antihistamines and corticosteroids before the infusion to reduce this risk. Patients are usually monitored for some time after the infusion to watch for immediate reactions.

G6PD Deficiency Risk

Krystexxa should not be used by individuals with a genetic condition called glucose-6-phosphate dehydrogenase (G6PD) deficiency. In these patients, the medication can cause the rapid breakdown of red blood cells (hemolysis) or a condition called methemoglobinemia, which affects the blood's ability to carry oxygen. Screening for G6PD deficiency is recommended for patients at higher risk, such as those of African, Mediterranean, or Southern Asian descent, before starting treatment.

Monitoring Uric Acid Levels

Serum uric acid levels are monitored before every infusion. If blood uric acid levels rise above 6 mg/dL, it may indicate that the body has developed antibodies against the drug, significantly increasing the risk of a severe allergic reaction. In such cases, the healthcare provider may decide to discontinue the treatment.

Gout Flares

An increase in gout flares is common during the first few months of treatment as the body begins to clear stored uric acid from the joints. To help manage this, healthcare providers often prescribe other medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or colchicine, to be taken alongside Krystexxa for the first six months of therapy.

Congestive Heart Failure

Krystexxa has not been formally studied in patients with severe congestive heart failure. Caution is advised for individuals with heart conditions, as the treatment may worsen heart failure symptoms. Patients should be monitored closely for signs of fluid retention or worsening heart function during treatment.

Use with Other Gout Medications

Oral medications used to lower uric acid, such as allopurinol or febuxostat, should generally be stopped before starting Krystexxa. Using these drugs together can hide a rise in uric acid levels, making it difficult for healthcare providers to identify when a patient is at an increased risk for a serious infusion reaction.

Pregnancy

There are no adequate and well-controlled studies of Krystexxa in pregnant women. While animal studies using doses significantly higher than the recommended human dose did not show evidence of harm to the fetus, human data is currently insufficient to determine if there is a drug-associated risk of major birth defects or miscarriage.

Breastfeeding

It is not known whether Krystexxa passes into human breast milk or if it has any effect on a nursing infant or milk production. Because many drugs are excreted in human milk, caution is generally advised when using this medication while nursing.

Consult Your Doctor

If you are pregnant, planning to become pregnant, or are breastfeeding, it is important to discuss the potential benefits and risks of Krystexxa treatment with your healthcare provider. They can help determine the best course of action based on your individual medical needs and the severity of your condition.

Dosage Forms

Krystexxa is supplied as a sterile, clear, and colorless solution. It is intended for administration through an intravenous infusion after being diluted by a healthcare professional.

The medication is provided in the following format:

• Single-dose vial: Each vial contains the medication as a concentrated liquid for one-time use.

FDA Approval and Indications

Krystexxa (pegloticase) is approved by the U.S. Food and Drug Administration (FDA) for the treatment of chronic gout in adult patients. It is specifically indicated for those with refractory gout, meaning their condition has not responded to or cannot be managed with conventional urate-lowering therapies.

Boxed Warning

The FDA has issued a boxed warning for Krystexxa regarding the risk of serious infusion reactions and anaphylaxis. These reactions can be life-threatening and may occur during or shortly after the administration of the drug. Because of these risks, Krystexxa must only be administered in a healthcare setting by medical professionals who are prepared to manage emergency allergic reactions. Patients are typically pre-medicated with antihistamines and corticosteroids to help reduce the likelihood of these reactions.

Contraindications and Safety Monitoring

The FDA requires specific safety protocols for patients using Krystexxa:

• G6PD Deficiency: The medication is contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency. There is a high risk of hemolysis (the breakdown of red blood cells) and methemoglobinemia in these individuals. Healthcare providers are advised to screen patients at risk for G6PD deficiency before starting treatment.
• Uric Acid Levels: Providers must monitor serum uric acid levels before every infusion. A rise in uric acid levels can indicate that the body has developed antibodies against the medication, which increases the risk of a serious infusion reaction.

Regulatory Oversight

The FDA continues to monitor the safety of Krystexxa through post-marketing surveillance. This includes tracking potential signals of serious risks, such as skin and subcutaneous tissue disorders, identified through the FDA Adverse Event Reporting System (FAERS) to ensure ongoing patient safety.

Cost Components

Krystexxa is an intravenous (IV) medication administered by a healthcare professional, usually every two weeks. The overall cost is influenced by several factors:

• Medication Price: The cost of the drug itself.
• Administration Fees: Charges for the healthcare provider's time and the equipment used for the infusion.
• Facility Costs: Fees associated with the clinic, hospital, or infusion center where the treatment is given.
• Premedications: The cost of medicines like antihistamines and corticosteroids given before the infusion to prevent allergic reactions.

Insurance and Financial Support

Krystexxa is generally covered under the medical benefit portion of insurance plans rather than the pharmacy benefit. Coverage varies based on your specific plan, and most insurers require prior authorization before they will pay for the treatment. Patients with commercial insurance may be eligible for copay assistance programs offered by the manufacturer. For those without insurance or who are underinsured, patient assistance programs may be available to help cover the costs based on financial need.