Uricase-Based Gout Drug Meets Endpoints in Phase 3 Trials

MILAN – Serum uric acid of less than 6 mg/dL was achieved and maintained for a substantial period of time with a once-monthly infusion of SEL-212 in patients with refractory gout, according to results of the two phase 3 DISSOLVE I and II trials.

Both trials met their primary endpoints. In DISSOLVE I – the U.S. study – 56% of patients on SEL-212 at 0.15 mg/kg (high dose) achieved a response, defined as achievement and maintenance of a reduction in serum urate to less than 6 mg/dL for at least 80% of the time during month 6 of treatment. In DISSOLVE II – the global study – 46% of patients on SEL-212 on the 0.15-mg/kg dose achieved response.

In participants aged 50 years or older, there was a statistically significant higher response rate at the high dose of SEL-212 in both DISSOLVE I and II of 65% and 47%, respectively, compared with placebo.

Herbert S.B. Baraf, MD, clinical professor of medicine at George Washington University, Washington, and principal investigator of the DISSOLVE program, presented results of the two phase 3 trials during a late-breaking session at the annual European Congress of Rheumatology.

"The top-line data from the two SEL-212 phase 3 studies are encouraging. They show that induction of immunotolerance with an infusion of a rapamycin-containing nanoparticle (SEL-110), followed immediately by an infusion of pegadricase, a potent but immunogenic uricase, allows for a strong and sustained uric acid–lowering effect without the development of anti-drug antibodies," Dr. Baraf said in an interview.

SEL-212 is a monthly two-part infusion therapy – a combination of Selecta Biosciences's ImmTOR immune tolerance platform, and a therapeutic uricase enzyme (pegadricase), designed to treat refractory gout. SEL-110 (ImmTOR) is an immune-tolerizing, nanoencapsulated rapamycin administered 30 minutes before pegadricase and inhibits anti-pegadricase antibodies. SEL-37 is a pegylated uricase (pegadricase) that converts uric acid to excretable allantoin.

SEL-212 was originally developed by Selecta. Swedish Orphan Biovitrum (Sobi) licensed SEL-212 from Selecta in June 2020 and is responsible for development, regulatory, and commercial activities in all markets outside of China. Selecta is responsible for ImmTOR manufacturing. The phase 3 program for SEL-212 was run by Selecta and funded by Sobi.

It is understood that a biologic license application will be submitted to the Food and Drug Administration, most likely next year, and if approved, "the SEL-212 two-component infusion treatment would provide a monthly alternative to twice-monthly pegloticase, for patients with refractory gout," Dr. Baraf added.

Details of the trials

The two DISSOLVE studies replicate double-blind, placebo-controlled trials in patients with chronic refractory gout. DISSOLVE I was carried out in 112 patients across 29 sites in the United States, and DISSOLVE II tested the two-part treatment in 153 patients across 37 sites in the United States, Russia, Ukraine, Georgia, and Serbia.

Both studies randomized patients 1:1:1 to a high dose (SEL-110 of 0.15 mg/kg plus SEL-037 of 0.2 mg/kg), low dose (SEL-110 of 0.1 mg/kg plus SEL-037 of 0.2 mg/kg), or placebo (saline) infused every 28 days for 6 months. Prophylaxis against infusion reactions and gout flares were given to all participants.

Adult patients had a 10- to 14-year history of symptomatic gout, with three or more flares over the 18 months prior to screening, or one or more tophus, or a diagnosis of gouty arthritis. They were also required to have chronic refractory gout with a failure to normalize serum uric acid with any xanthine oxidase inhibitor (for example, allopurinol) and to have not been previously exposed to uricase-based therapy. Serum uric acid had to be at least 7 mg/dL. Participants were balanced for age, body mass index, and sex across treatment groups. Gout severity was greater in DISSOLVE II, Dr. Baraf reported.

Both studies treated patients for 6 months, but DISSOLVE 1 continued with a 6-month, blinded safety extension. The primary endpoint in both studies was serum urate control during month 6, and secondary endpoints included tender and swollen joint counts, tophus burden, patient-reported outcomes of activity limitation, quality of life, and gout flare incidence.

In DISSOLVE I, patients on SEL-212 had a statistically significant higher response rate during month 6 of 56% with the high dose (P < .0001) and 48% with the low dose (P < .0001), compared with 4% of patients randomized to receive placebo. In DISSOLVE II, participants on SEL-212 had a statistically significant higher response rate during month 6 of 46% with the high dose (P = .0002) and 40% with the low dose (P = .0008), compared with 11% of patients randomized to receive placebo.

"We also saw significant reductions in serum uric acid for all treatment groups, compared with placebo," Dr. Baraf reported. Mean percentage change was –62.3% and –58.3% in the high- and low-dose groups, respectively, in DISSOLVE I, and –58.1% and –52.2% in DISSOLVE II, respectively.

SEL-212 had a favorable safety profile with adverse events as expected across both doses, including mild to moderate stomatitis (3.4% in the low-dose group and 9.2% in the high-dose group versus 0% in the placebo group), and a greater number of infusion reactions at 24 hours and 1 hour after drug administration in both treatment groups versus placebo. Six patients had treatment-related serious adverse events, including two cases of anaphylaxis and one gout flare in both the high- and low-dose treatment groups. The 6-month extension period in the DISSOLVE I trial showed that the majority (75%) of patients who completed 6 months of SEL-212 treatment as a responder continued to be successfully treated through 12 months with no infusion reactions or safety signals.

"I expect more data will be forthcoming on the important clinical secondary endpoints targeted by SEL-212 therapy," Dr. Baraf noted.

Need control arm taking allopurinol?

Roy Fleischmann, MD, clinical professor of medicine at the University of Texas Southwestern Medical Center and codirector of the Metroplex Clinical Research Center, both in Dallas, commented on the study methods after the presentation. "The major problem with this study is that they say the patients had had insufficient response to allopurinol, and my guess is most had received 100-200 mg of allopurinol but were not titrated up to the maximum tolerated dose," he said, adding: "they should have had a control arm of patients on allopurinol and titrated to the maximum tolerated dose. So, I don't know what this is really telling us with respect to allopurinol, which is a relatively cheap drug."

Dr. Baraf reported consulting with Horizon, Sobi, and Selecta; serving on Horizon's speakers bureau, and receiving grant/research support from Horizon and Sobi. Dr. Fleischmann reported no financial relationship of relevance to this study.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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Cite this: Uricase-Based Gout Drug Meets Endpoints in Phase 3 Trials - Medscape - Jun 07, 2023.