Criteria to Stop Krystexxa (Pegloticase)
Discontinue Krystexxa immediately when the pre-infusion serum uric acid level rises above 6 mg/dL on a single occasion, as continuing therapy beyond this point dramatically increases infusion reaction risk (from <1% to nearly 10% per infusion) while providing minimal additional benefit. 1, 2, 3
Primary Discontinuation Criterion: Loss of Uric Acid Control
Stop pegloticase when a single pre-infusion serum uric acid measurement exceeds 6 mg/dL, as post-hoc analysis of pivotal trials demonstrated this approach would reduce infusion reactions by approximately 67% with only a 20% reduction in efficacy outcomes. 1
Measure serum uric acid before every infusion to identify loss of therapeutic response early. 3
The FDA label explicitly states that physicians may stop pegloticase if uric acid levels do not become normal and stay controlled. 1
Infusion Reaction-Related Discontinuation
Discontinue immediately for any anaphylaxis (wheezing, peri-oral/lingual edema, hemodynamic instability, urticaria, dyspnea, throat tightness, or chest pain during or after infusion). 1, 2
Stop therapy for moderate-to-severe infusion reactions even if uric acid remains controlled, as these reactions indicate immune-mediated drug intolerance. 4
Recognize that 91% of all infusion reactions occur in patients with pre-infusion serum uric acid >6 mg/dL, making uric acid monitoring the key safety parameter. 3
Evidence Supporting the Single Elevated Uric Acid Rule
In responders receiving pegloticase every 2 weeks, infusion reactions occurred in <1 per 100 infusions (<1%), compared to 9.7% in non-responders with elevated uric acid levels. 2
Waiting for two consecutive elevated uric acid levels (>6 mg/dL) before stopping reduces infusion reactions by only 50% compared to 67% with the single-measurement rule, while providing little additional efficacy benefit. 1
Loss of uric acid lowering indicates development of anti-drug antibodies, which drive both treatment failure and infusion reaction risk. 5, 3
Additional Discontinuation Scenarios
Stop for G6PD deficiency diagnosis if discovered during treatment, as pegloticase is absolutely contraindicated in this population. 1
Discontinue if the patient requires oral urate-lowering therapy (allopurinol, febuxostat) during pegloticase treatment, as these agents should not be co-administered with pegloticase. 1
Consider stopping after achieving complete tophus resolution and sustained uric acid control if transitioning to oral urate-lowering therapy, particularly after ≥12 infusions, as 78% of such patients maintain uric acid <6 mg/dL on subsequent oral therapy. 6
Critical Monitoring Algorithm
Before each infusion:
- Measure serum uric acid—if >6 mg/dL on a single occasion, stop therapy immediately. 1, 3
- Assess for any new symptoms suggesting infusion reaction from prior dose. 1
During and 2 hours post-infusion:
- Monitor continuously for signs of anaphylaxis or infusion reactions. 1
- Have emergency equipment and medications immediately available. 1
Common Pitfalls to Avoid
Do not continue pegloticase after uric acid rises above 6 mg/dL hoping for spontaneous improvement—this exposes patients to high infusion reaction risk (nearly 10% per infusion) without therapeutic benefit. 2, 3
Do not wait for two consecutive elevated uric acid measurements before stopping, as this doubles the infusion reaction risk compared to stopping after a single elevation. 1
Do not restart pegloticase monotherapy after prior treatment failure, as the response rate drops to 9% with an 18% infusion reaction rate due to established anti-drug antibodies; if retreatment is considered, immunomodulation (methotrexate) must be initiated before the first pegloticase exposure. 4
Do not advise patients to stop pegloticase during a gout flare, as flares are expected in the first 3 months and decrease thereafter; instead, treat the flare while continuing pegloticase. 1