Abstract
INTRODUCTION: Gout is a painful inflammatory condition caused by chronically elevated serum uric acid levels (sUA). When standard urate-lowering therapies fail/are not tolerated, uncontrolled gout (elevated sUA, subcutaneous tophi, chronic gouty arthritis, frequent flares) can occur. Pegloticase, a recombinant uricase, converts uric acid to allantoin, a readily excreted molecule. Responder rate in trials was 42%, limited by anti-drug antibody (ADA) development. Immunomodulators attenuate ADA formation and case reports suggest immunomodulation increases pegloticase responder rates. The current study retrospectively examined responder rate in patients undergoing methotrexate/pegloticase co-therapy. METHODS: Patients who underwent methotrexate/pegloticase co-treatment at a single rheumatology practice were included. Demographics, clinical, treatment, and safety parameters were collected. The primary outcome was the proportion of responders (≥ 12 biweekly pegloticase infusions, sUA < 6 mg/dl just prior to infusion 12). RESULTS: Ten patients (nine men, 52.3 ± 13.5 years) with uncontrolled tophaceous gout (erosive damage, ulcerative tophi, frequent flares, gout-related hospitalizations) were included. Patients had failed allopurinol (100-300 mg) or febuxostat (40 mg) therapy (doses not increased because of intolerance, kidney concerns, noncompliance, or rapid tophi resolution requirement). Baseline sUA was 9.42 ± 2.05 mg/dl. Along with standard pre-infusion prophylaxis, nine patients received subcutaneous methotrexate (25 mg/week) initiated 14-35 days before pegloticase and one patient received oral methotrexate (12.5 mg/week) initiated 14 days after pegloticase. Eight patients (80%) were responders, receiving 15.5 ± 3.8 infusions (range, 12-21) over 31.8 ± 9.5 weeks. One patient had efficacy loss with mild infusion reaction during infusion 4 and one patient was lost to follow-up after infusion 5. One patient reported one gout flare. No new safety concerns emerged. CONCLUSIONS: Methotrexate/pegloticase co-therapy resulted in a higher responder rate than the established 42% with pegloticase alone. Therefore, methotrexate/pegloticase co-therapy may safely allow more patients to benefit from a full treatment course, likely through ADA attenuation.