Pegloticase is a pegylated, recombinant urate oxidase enzyme that is used to treat patients with chronic refractory and symptomatic gout. Pegloticase has not been associated with serum enzyme elevations during therapy or with instances of clinically apparent liver injury.


Pegloticase (peg loe’ ti kase) is a recombinant DNA-produced form of the porcine enzyme uricase that metabolizes urate to allantoin, an inert and water soluble purine metabolite that, unlike uric acid, is rapidly cleared by the kidney. Infusions of pegloticase decrease serum uric acid concentrations and can alleviate the symptoms and complications of gout. Pegloticase was approved in the United States in 2010 for use in patients with chronic symptomatic gout who are refractory to conventional therapy with uricourics and xanthine oxidase inhibitors, which should be discontinued before pegloticase is started. It is available as a sterile concentrate of 8 mg in a single use vial under the brand name Kystexxa. The recommended dose 8 mg given intravenously every two weeks. Common side effects of pegloticase include local and systemic infusion reactions, nausea, vomiting, constipation, chest pain and nasopharyngitis. Pegloticase infusions are associated with paradoxical flares of clinical gout during the first 3 months of therapy in up to 80% of patients. Severe adverse reactions may include anaphylaxis (in up to 7% of patients), severe infusion reactions, hemolysis and methemoglobinemia (in patients with G6PD deficiency) and congestive heart failure. Because resistance to pegloticase is associated with antibodies to the molecule and with rise of uric acid levels and initial control, it is recommended that patients be monitored for uric acid levels and that pegloticase be stopped if uric acid levels rise above 6 mg/dL.


In large clinical trials, serum enzyme elevations were rare (<1%) during pegloticase therapy and no more common than with placebo. Since licensure and its more wide scale, there have been no published case reports of hepatotoxicity due to pegloticase and the product label does not list liver injury as an adverse event. Thus, liver injury due to pegloticase must be rare, if it occurs at all.

Likelihood score: E (unlikely cause of clinically apparent liver injury).

Mechanism of Injury

Pegloticase is a polypeptide and is metabolized to amino acids by serum and tissue proteases, and is unlikely to have any direct hepatotoxic potential.

Drug Class: Antigout Agents



Pegloticase – Krystexxa®


Antigout Agents


Product labeling at DailyMed, National Library of Medicine, NIH



References updated: 21 May 2018

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    (Textbook of hepatotoxicity published in 1999 and before the availability of pegloticase).
  • Grosser T, Smyth E, FitzGerald GA. Pharmacotherapy of gout. Anti-inflammatory, antipyretic and analgesic agents; pharmacotherapy of gout. In, Brunton LL, Chabner BA, Knollman BC, eds. Goodman & Gilman’s the pharmacological basis of therapeutics. 12th ed. New York: McGraw-Hill, 2011, pp. 994-1000.
    (Textbook of pharmacology and therapeutics).
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    (Among 41 patients with severe, refractory gout treated with pegloticase in four dose regimens, adverse reactions included flares of gout and infusion reactions).
  • Sundy JS, Baraf HS, Yood RA, Edwards NL, Gutierrez-Urena SR, Treadwell EL, Vázquez-Mellado J, et al. Efficacy and tolerability of pegloticase for the treatment of chronic gout in patients refractory to conventional treatment: two randomized controlled trials. JAMA 2011; 306: 711-20. [PubMed: 21846852]
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    (Concise summary of the mechanism of action, pharmacology, clinical efficacy, safety and costs of pegloticase shortly after its approval for use in gout in the US mentions anaphylaxis, infusion reactions and gout flares, but not ALT elevations or hepatotoxicity).
  • Becker MA, Baraf HS, Yood RA, Dillon A, Vázquez-Mellado J, Ottery FD, Khanna D, et al. Long-term safety of pegloticase in chronic gout refractory to conventional treatment. Ann Rheum Dis 2013; 72: 1469-74. [PMC free article: PMC3756467] [PubMed: 23144450]
    (Among 149 patients with gout treated with pegloticase infusions every 2 weeks for an average of 25 months, adverse events included gout flares [71%], infusion reactions [44%], arthralgia [20%] and nausea [11%], but clinical chemistry results did not change from baseline).
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    (Among 118 adverse events attributed to pegloticase therapy reported to the FDA over a 2 year period, 11 were cases of anaphylaxis and 35 were infusion related reactions; miscellaneous reactions included 2 cases of hepatic failure, 2 hepatocellular injury, 3 hepatotoxicity, 1 liver function test abnormal and 1 transaminase increased; but no specific details given).
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    (38 year old Hispanic man developed severe hemolytic anemia and methemoglobinemia within 48 hours of an infusion of pegloticase for refractory gout, testing demonstrating G6PD deficiency despite reports of a negative assay done before therapy).
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    (Among 208 patients who received 6389 infusions of pegloticase in 3 studies, 94 [45%] had an infusion reaction with symptoms usually arising during the infusion [chest discomfort, flushing, dyspnea, back pain, sweating, nausea, erythema, urticarial rash, pruritus, muscle spasms and headache], all resolving with stopping the infusion but leading to discontinuation in 31 [15%] patients, but no patient died or required intubation and ventilation).
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  • Chalasani N, Bonkovsky HL, Fontana R, Lee W, Stolz A, Talwalkar J, Reddy KR, et al.; United States Drug Induced Liver Injury Network. Features and outcomes of 899 patients with drug-induced liver injury: the DILIN Prospective Study. Gastroenterology 2015; 148: 1340-52. [PMC free article: PMC4446235] [PubMed: 25754159]
    (Among 899 cases of drug induced liver injury in the US collected between 2004 and 2012, 8 cases were attributed to drugs used for gout [allopurinol in 7 and febuxostat in 1], but no cases were attributed to pegloticase or rasburicase).
  • Wilson FP, Berns JS. Tumor lysis syndrome: new challenges and recent advances. Adv Chronic Kidney Dis 2014; 21: 18-26. [PMC free article: PMC4017246] [PubMed: 24359983]
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  • Guttmann A, Krasnokutsky S, Pillinger MH, Berhanu A. Pegloticase in gout treatment - safety issues, latest evidence and clinical considerations. Ther Adv Drug Saf 2017; 8: 379-88. [PMC free article: PMC5703101] [PubMed: 29204266]
    (Careful review of the clinical features and epidemiology of gout and efficacy and safety of pegloticase, common side effects being a flare of gout [71-85%], infusion reactions [26-42%], headache [9-11%], nausea [7-12%] and cardiovascular events [2-7%]; no mention of ALT elevations or hepatotoxicity).