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For gout, xanthine oxidase (XO) inhibitors are the choice for first-line urate-lowering therapy (ULT) according to the 2020 American College of Rheumatology Guideline for the Management of Gout, which endorsed allopurinol, but should that be the approach for all patients, or should first-line therapy be tailored to the mechanism of each patient’s hyperuricemia? Two gout experts, Lisa Stamp, MBChB, PhD, a rheumatologist and professor of medicine at the University of Otago in Christchurch, New Zealand, and Fernando Pérez-Ruiz, MD, PhD, consultant in the Rheumatology Division of Cruces University Hospital, Barakaldo, head of the Investigation Group for Arthritis at Biocruces Health Research Institute, Barakaldo, and associate professor in the Department of Medicine at the Faculty of Medicine and Nursing at the University of the Basque Country in Leioa, Spain, debated this question recently at the annual research symposium of the Gout, Hyperuricemia and Crystal-Associated Disease Network.

Before the debate began, audience members voted on the question and 56% favored using XO inhibitors as a first-line therapy for all rather than tailoring first-line therapy to disease mechanism.

Up first, Stamp argued that XO inhibitors should be first-line therapy for all patients with gout. She said that XO inhibitors have been demonstrated to work regardless of the cause of hyperuricemia and degree of kidney function, and they are cheap, readily available, and easy to administer. She showed results from a study published by her debate opponent, Pérez-Ruiz, which demonstrated efficacy of XO inhibitors in both under-excreters and over-excreters of uric acid. That study compared the efficacy of the XO inhibitor allopurinol to the uricosuric agent benzbromarone and found the latter to be more effective, but Stamp argued that the allopurinol dose used in the study — 300 mg/d — “may not be enough for many patients who have gout. Dose-restricting allopurinol is one way to demonstrate that an alternative agent is superior,” she said.

A more recent study showed low-dose benzbromarone was better than low-dose febuxostat, another XO inhibitor. “I think we do need to have clinical trials that reflect real-world practice. I accept that this may have reflected [accepted practice where the studies] were undertaken, but these [XO inhibitor] doses don’t represent what many of us would do in other parts of the world,” Stamp said.

One concern is the utility of a ULT in patients with impaired renal function. Stamp cited her own post hoc analysis of a randomized, controlled trial showing that allopurinol is effective irrespective of renal function, as long as the dose is escalated to achieve target urate level, and a meta-analysis of observational studies suggesting that febuxostat is effective irrespective of renal function.

On the other hand, she showed data from a 1994 study of benzbromarone in renal transplant recipients, which showed that the drug’s effect on decreasing plasma uric acid dropped off significantly with lower creatinine clearance. “It does work, but the efficacy really drops off as renal function decreases. Benzbromarone is probably the most effective uricosuric in patients with renal impairment, but this agent is not readily available,” Stamp said.

The uricosuric agent probenecid, which is generally available across the world, led to only about 30% success in achieving target levels of uric acid among patients with an estimated glomerular filtration rate < 50 mL/min/1.73 m². “I think we can all agree that getting 30% of our patients to target uric acid is not an acceptable outcome,” she said.

Stamp emphasized the importance of drug availability and noted that allopurinol is also the only medication for gout that is on the World Health Organization list of essential medications. “I think we should be recommending medications that are readily available, irrespective of where you live,” she said, noting that this is true of allopurinol, febuxostat, and probenecid.

Stamp also addressed the mechanism of action of ULTs. “Does the cause of hyperuricemia affect treatment response? I don’t think it does. Most people respond to allopurinol whether they’re a normal excreter or an under-excreter. Everyone who is lacking uricase will respond to allopurinol. Not everyone will respond to a uricosuric [agent], particularly in the setting of comorbidities such as renal impairment, which many of our patients with gout have,” she said.

Counterargument: Combine Therapies With Different Mechanisms of Action

In his counterargument, Pérez-Ruiz contended that gout is not in fact a metabolic disease and suggested that combining therapies with different mechanisms of action could be the best approach for difficult-to-treat gout. “The problem we face in clinical practice is how to treat difficult-to-treat patients,” he said. He referenced his own PhD thesis, which showed both high urinary uric acid output and underexcretion among patients with gout.

Pérez-Ruiz agreed that XO inhibitors should be used as first-line therapy but noted that the effect of allopurinol tapers off at higher doses. “If you use very high doses of allopurinol, you cannot expect to get much more effect,” he said. This is also true of febuxostat, he said.

He showed another study that illustrated difficulties in achieving target serum urate level with intensive therapy. “Even using a high dose of allopurinol, if you would like to get lower than 3 mg/dL for intensive therapy, close to 50% of patients will fail,” he said.

Pérez-Ruiz described a strategy of combining XO inhibitors with a uricosuric therapy, creating what he called a “uricase-like effect” on serum uric acid levels. Ruiz-Perez uses high-dose febuxostat in patients with chronic kidney disease who cannot be given uricosuric agents. “You can go to very low [serum urate levels] by raising up the doses,” he said.

He does not believe that allopurinol is the best agent for combination therapy in the treatment of tophaceous deposits. Instead, he favors combinations with febuxostat. He presented his own experience with 12 patients with very severe tophaceous gout who he treated with a combination of febuxostat and benzbromarone, which reduced serum urate to just over 2 mg/dL. “So this is a pegloticase-like effect [that is] very useful for tophaceous gout,” he said.

In her response, Stamp noted that most of the studies presented by Pérez-Ruiz showed XO inhibitors as first-line therapies, with other medications added on. “I think I heard Fernando agree with me. In just about all of those slides, he showed that a xanthine oxidase inhibitor was the first-line therapy, and subsequently a uricosuric was added,” she said.

Still, Stamp took issue with the idea that serum urate needs to get as low as Pérez-Ruiz advocated for. “What’s the risk associated with getting a serum urate to that level? I’m not sure that a sustained serum urate of around 1 [mg/dL] is necessarily good in the long term,” she said.

Stamp also pointed out the potential risks of polypharmacy, along with adherence issues. “If we can give our patients one therapy, one drug that’s going to get them to a target that we know is going to have beneficial long-term effects, that’s going to help improve our adherence. Maybe we are coming to a new era of [treatment, with] remission induction driving the serum urate very low, and then a maintenance therapy where we can back off. But irrespective, if you use that strategy, Fernando nicely showed that every time you’re going to start with a xanthine oxidase inhibitor,” she said.

After the debate, audience members voted again, and this time the result was 66% in favor of XO inhibitors as a first-line treatment.

Pérez-Ruiz is an adviser for Arthrosi, LG, Novartis, Protalix, and SOBI. He is a speaker for Menarini Central America and the Spanish Foundation for Rheumatology and has received funding from Cruces Rheumatology Association. Stamp did not disclose any financial relationships.

Jim Kling is a writer in Bellingham, Washington.