Pegloticase

Introduction Overview

Generic Name

pegloticase

Brand Name

Krystexxa

Dosage Form

Intravenous infusion (Single-Dose Vial, 8 mg/1 mL)

Drug Class

Antihyperuricemic agents

Pharmacokinetics

Absorption:
Pegloticase is administered intravenously, bypassing gastrointestinal absorption processes. This route allows direct entry of the enzyme into systemic circulation, ensuring complete bioavailability. The intravenous infusion is typically given over at least two hours to maintain steady plasma concentrations and minimize infusion-related reactions.

Distribution:
Once in circulation, pegloticase distributes primarily within the vascular compartment due to its large molecular size as a PEGylated recombinant uricase enzyme. It does not readily cross cellular membranes and remains largely confined to the bloodstream and interstitial fluids. The PEGylation enhances its stability and prolongs plasma half-life by reducing renal clearance and proteolytic degradation.

Metabolism:
Pegloticase, being an enzyme, undergoes metabolism primarily via proteolytic degradation by reticuloendothelial system cells, including hepatic and splenic macrophages. The PEGylation decreases immunogenicity and slows enzyme degradation, contributing to a plasma half-life of approximately 10 to 12 days. Unlike small molecules, pegloticase is not metabolized by cytochrome P450 enzymes.

Elimination:
The inactive metabolites of pegloticase resulting from proteolysis are eliminated predominantly via the renal and hepatic pathways. Intact pegloticase is cleared via the reticuloendothelial system. The elimination half-life allows for dosing every two weeks. Patients with renal or hepatic impairment have not shown significantly altered elimination, but clinical monitoring is recommended. Antibody formation against pegloticase can accelerate clearance, reducing therapeutic efficacy.

Dosage Forms

Available Dosage Forms:
- Single-Dose Vial: 8 mg/1 mL solution for intravenous infusion

Dosages for Adults and Adolescents:
- The recommended dose for adults with chronic gout refractory to conventional therapy is 8 mg administered intravenously every two weeks.
- Krystexxa is typically co-administered with weekly oral methotrexate 15 mg to reduce immunogenicity and infusion reactions. In cases where methotrexate is contraindicated, pegloticase may be used alone.
- Infusions must be administered slowly over at least 2 hours by a healthcare provider.

Specific Patient Populations:
- Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency should not receive Krystexxa due to risk of hemolysis and methemoglobinemia.
- Safety and dosage in pediatric populations have not been established.
- Use in pregnant or breastfeeding women should be approached cautiously, with assessment of potential risks versus benefits.
- Regular monitoring is essential to evaluate treatment response and adverse effects. Gout flares may increase initially when treatment starts, and prophylactic medications for flare prevention may be recommended.

Clinical Guidelines:
- Premedication with antihistamines and corticosteroids prior to infusion is essential to reduce risk of anaphylaxis and infusion reactions.
- Treatment duration should be individualized based on clinical response and tolerability.

Mechanism Of Action

Pegloticase is a recombinant, PEGylated uricase enzyme that enzymatically converts soluble uric acid into allantoin, a highly soluble and easily excreted metabolite. This reaction occurs by oxidizing uric acid, which humans normally cannot do due to evolutionary loss of uricase enzyme activity. The increased breakdown of uric acid helps lower serum urate levels effectively in patients with refractory gout.

At the molecular level, pegloticase catalyzes the conversion of uric acid to allantoin by incorporating molecular oxygen and generating hydrogen peroxide as a byproduct. The PEGylation of the enzyme reduces immunogenicity, increases circulating half-life, and enhances enzyme stability in plasma. The enzyme’s activity thereby results in rapid and sustained depletion of circulating uric acid, preventing deposition of monosodium urate crystals which cause gout symptoms.

Cellularly, pegloticase circulates extracellularly, acting on urate molecules in plasma and tissues. The reduction in serum urate decreases the inflammatory response triggered by urate crystals in joints and other tissues. Clinically, this enzymatic activity translates into reduced frequency and severity of gout flares, improved joint function, and resolution of tophi in chronic gout patients unresponsive to standard therapies.

Comparatively, pegloticase’s mechanism is distinct from xanthine oxidase inhibitors such as allopurinol and febuxostat that reduce uric acid production; pegloticase accelerates uric acid degradation. Clinical studies have demonstrated its superior urate-lowering ability in refractory cases, albeit with risks of infusion reactions and antibody formation limiting long-term use. Research continues to optimize co-therapies for efficacy and safety.

Pharmacological Actions

Enzymatic degradation of uric acid to allantoin, facilitating urate clearance
Reduction of serum uric acid concentration in patients with hyperuricemia
Prevention and resolution of monosodium urate crystal deposition
Mitigation of gout symptoms including joint inflammation and tophi
PEGylation prolongs enzyme half-life and reduces immunogenicity
Administration leads to rapid and sustained urate lowering
Adjunctive use with methotrexate decreases immunogenicity and infusion reactions
Reduces frequency and severity of gout flares after initial treatment period
Bypassing renal uric acid excretion mechanisms, beneficial in patients with renal impairment
Facilitates improved joint function and quality of life in refractory gout patients
Enzyme is cleared by proteolytic pathways, limiting accumulation
Mechanism distinct from xanthine oxidase inhibitors, offering an alternative therapeutic approach
Initiation of therapy may transiently increase gout flares due to crystal mobilization

Therapeutic Or Clinical Uses

Treatment of chronic gout in adult patients refractory to conventional therapy
Indicated for patients who have failed maximum medically appropriate doses of xanthine oxidase inhibitors
Management of hyperuricemia with persistent signs and symptoms despite standard care
Reduction of tophaceous gout and urate crystal burden
Alternative treatment for patients contraindicated for allopurinol or febuxostat
Adjunctive option when methotrexate is used concomitantly to improve tolerance
Used in patients experiencing frequent gout flares despite other treatments
May help improve joint function and reduce inflammation associated with gout
Utility in patients with renal impairment limiting use of traditional urate-lowering agents
Treatment option for severe tophaceous gout with significant morbidity
Improves quality of life by controlling refractory gout symptoms
Utilized in specialist settings due to need for intravenous administration and monitoring
Recommended only after other gout treatments have failed or are inappropriate

Side Or Adverse Effects

Infusion-related reactions including itching, skin redness, flushing, and chest discomfort
Anaphylaxis potentially life-threatening, requiring premedication and monitoring
Gout flares often increase transiently during the initial treatment phase
Hypersensitivity reactions such as urticaria and wheezing
Common COVID-19 symptoms reported including fever, chills, cough, and fatigue
Nausea, vomiting, and constipation during or after infusion
Bruising and minor bleeding complications
Shortness of breath and light-headedness during infusion
Fast heartbeat and nervousness during or after administration
Potential for antibody-mediated loss of efficacy and increased infusion reactions
Chest pain or discomfort requiring immediate medical attention
Risk of hemolysis in patients with G6PD deficiency
Rare occurrence of methemoglobinemia in G6PD deficient patients
Local injection site reactions uncommon but possible
Potential worsening of pre-existing cardiovascular conditions during treatment

Precautions

Contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency due to risk of hemolytic anemia
Premedication with antihistamines and corticosteroids is advised to minimize infusion reactions
Patients should be monitored closely during and after infusion for signs of hypersensitivity
Discontinue therapy immediately if severe infusion reactions or anaphylaxis occur
Used cautiously in patients with pre-existing cardiovascular conditions or uncontrolled hypertension
Assess for allergies to pegloticase or PEG components before initiation
Regular monitoring of serum uric acid levels and clinical response is essential
Pregnant or breastfeeding women should use only if potential benefits justify potential risks
Avoid concurrent use with xanthine oxidase inhibitors such as allopurinol or febuxostat without physician approval
Instruct patients to report symptoms such as itching, shortness of breath, or chest pain promptly
Methotrexate co-administration recommended to reduce immunogenicity and improve safety
Avoid abrupt discontinuation of concomitant gout prophylactic medications
Monitor for new or worsening gout flares, particularly during early treatment
Ensure patients understand the importance of adherence to infusion schedules
Use with caution in patients with renal or hepatic impairment and monitor accordingly

Warnings

Serious hypersensitivity and anaphylactic reactions including fatal outcomes have been reported
Risk of severe infusion reactions necessitates administration in healthcare settings equipped for emergency management
Contraindicated in patients with G6PD deficiency due to risk of hemolytic anemia and methemoglobinemia
Do not use concomitantly with allopurinol, probenecid, or febuxostat as it may increase adverse reactions or reduce efficacy
Initial treatment period may paradoxically increase gout flares; prophylaxis recommended
Patients should be observed for signs of immunogenicity that may result in loss of efficacy
Use caution in patients with pre-existing cardiovascular, respiratory, or immune disorders
Pregnancy risks unknown; use only if clearly needed and under medical supervision
Use requires careful monitoring of vital signs and infusion tolerance throughout administration
Risk of serum sickness-like reactions after repeated administration
Discontinue drug if infusion reactions or allergic symptoms develop
Inform patients of potential severity and symptoms of infusion-related reactions
Avoid self-administration; must be administered by trained healthcare professionals
Potential for drug interaction with multiple gout medications requiring treatment adjustment
Close monitoring advised during co-administration with immunosuppressants

Contraindication

Known hypersensitivity to pegloticase or any component of the formulation
Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency
Concurrent use with xanthine oxidase inhibitors such as allopurinol or febuxostat
History of severe allergic reactions to biologic enzyme therapies
Patients with active infections or immunocompromised status unless benefits outweigh risks
Known hypersensitivity to polyethylene glycol (PEG) or PEGylated products
Use in pediatric patients is contraindicated due to lack of safety and efficacy data
Severe uncontrolled cardiovascular disease without physician oversight
Pregnancy and breastfeeding unless under specific medical advice
Patients unable to receive proper premedication or monitoring for infusion reactions
Known intolerance to methotrexate when co-administered and no suitable alternatives
Concurrent use with probenecid unless medically supervised
Known history of serum sickness with enzyme replacement therapies
Conditions where intravenous infusion is contraindicated
Patients with severe hepatic impairment without close monitoring

Drug Interactions

Avoid concomitant use with allopurinol due to increased risk of adverse effects and reduced pegloticase efficacy
Concurrent administration with febuxostat may result in drug interactions and is not recommended
Probenecid co-administration should be avoided to prevent complex drug interactions
Methotrexate used concomitantly to decrease immunogenicity and infusion reactions
Potential interactions with immunosuppressants requiring dose adjustment
No significant cytochrome P450 mediated interactions expected
Interactions with antihistamines and corticosteroids used as premedication are clinically managed
Use caution when combined with other gout flare prophylactics such as colchicine or NSAIDs
Drugs affecting immune function may alter pegloticase safety and efficacy profiles
Potential pharmacodynamic interaction with other biologics requiring monitoring
Avoid use with nephrotoxic drugs to minimize renal stress in gout patients
Vitamin and herbal supplements should be disclosed to healthcare providers to avoid unknown interactions
Careful assessment required when used with drugs altering uric acid metabolism
Monitoring advised if combined with medications affecting cardiovascular or respiratory systems
Potential pharmacokinetic and pharmacodynamic interactions with new experimental therapies remain under investigation

Preparations Of The Drug

Krystexxa is supplied as a sterile single-dose vial containing 8 mg of pegloticase in 1 mL solution
Formulated for intravenous infusion only; no oral or subcutaneous formulations available
Vials must be stored refrigerated between 2°C and 8°C (36°F and 46°F) and protected from light
Should be prepared under aseptic conditions by diluting with compatible infusion fluids prior to administration
Supplied by Horizon Therapeutics Ireland DAC
Premedication formulations often include antihistamines (e.g., diphenhydramine) and corticosteroids (e.g., methylprednisolone) to be administered before infusion
Packaging includes detailed instructions for dilution, administration rate, and handling precautions
No biosimilars interchangeable with Krystexxa are currently FDA approved comprising identical formulation
Enzyme activity in preparation is standardized and quality controlled to ensure consistent dosing
Disposal guidelines recommend treating unused portions as biohazardous waste
No oral, topical, or inhalation formulations; strict intravenous administration recommended
Infusion devices and equipment required for administration supplied separately and should comply with standard intravenous therapy protocols
Patient information leaflets included to guide on infusion-related risks and side effect management
Preparation protocols include screening for G6PD deficiency prior to initiation
Instructions emphasize slow infusion over at least two hours and patient monitoring throughout procedure