Pegloticase is a highly effective therapy for patients with refractory and/or tophaceous gout, but has a high discontinuation rate (30-50%) due to development of anti-drug antibodies causing loss of efficacy and risk of infusion reactions.
To describe the use of azathioprine or other immunosuppressive therapies as a pegloticase adjunct to prevent pegloticase immunogenicity when treating gout.
Case report of azathioprine use in a patient receiving pegloticase therapy for refractory tophaceous gout, and review of the literature for the impact of immunosuppressive agents on development of anti-drug antibodies.
A 56-year-old man with severe refractory tophaceous gouty arthritis was placed on low-dose azathioprine (50mg daily) in combination with pegloticase, with successful treatment after 98 weeks illustrated by significant improvement of caliper-measured tophi (77% decrease), resolution of gouty attacks, maintenance of low serum urate (sUA) level, absence of infusion reactions, and good toleration of the treatment by the patient. Two transient increases in sUA (maximal sUA 1.0 and 6.2mg/dL, respectively), were associated with azathioprine non-compliance and resolved with azathioprine reinstitution. Literature review confirmed successful use of DMARDs for prevention of anti-drug antibodies to anti-TNF-α therapies in RA, spondyloarthropathies, and inflammatory bowel disease. Additionally, one open-label trial of pegloticase for refractory tophaceous gout included 7 organ transplant recipients on immunosuppressive medications (mycophenolate mofetil, cyclosporine, azathioprine, and/or tacrolimus), only one of whom (14%) was noted to experience treatment failure (anti-pegloticase antibodies and loss of urate-lowering efficacy without infusion reaction), versus 52% (n =12) of non-immunosuppressed subjects (n = 23).
Low doses of oral immunosuppressive therapy may provide a safe, cost-effective adjunct to prevent the development of anti-drug antibodies associated with infusion reactions and high rate of pegloticase failure in patients with refractory gout. Controlled studies to assess an immunosuppressive strategy when using pegloticase are warranted.