NASP Reduces Tophi in Uncontrolled Gout

CHICAGO—Gout is caused by high serum uric acid levels and is the most common form of inflammatory arthritis, affecting nearly 8.3 million individuals in the U.S.¹

On Sept. 10, 2025, the U.S. Food & Drug Administration (FDA) accepted the biologics license application for tolerogenic nano-encapsulated sirolimus with pegylated-adricase (NASP) for the treatment of uncontrolled gout.² The FDA has set a Prescription Drug User Fee Act target action date of June 27. The Biologics License Application submission includes data from the pivotal DISSOLVE I (NCT04513366) and II (NCT04596540) clinical trials.^3,4 In May 2024, the FDA granted fast-track designation for NASP due to its potential to address a serious condition with limited treatment options.

NASP, formerly called SEL-212, is administered every four weeks as a sequential, two-component, infusion therapy.

New Analysis

At ACR Convergence 2025, data on reducing tophi with NASP was presented by Herbert S.B. Baraf, MD, FACP, founder of Arthritis and Rheumatism Associates, clinical professor of medicine at The George Washington University School of Medicine, Washington, D.C., and a clinical associate professor of medicine at the University of Maryland School of Medicine.⁵ Using data on tophus outcomes in both phase 3, DISSOLVE clinical trials, the post-hoc analysis showed greater tophus response in patients treated with NASP than in patients who received placebo. Additionally, a robust reduction in serum uric acid was observed in patients treated with NASP.

Study participants were randomly assigned in a 1:1:1 ratio to receive low-dose NASP, high-dose NASP or placebo administered as an intravenous infusion every 28 days for up to 12 infusions. The data included individuals in the intent-to-treat population and those who received six doses of high-dose NASP, low-dose NASP or placebo.

Tophus response was a predefined secondary end point in the DISSOLVE studies. Tophus response included partial response (i.e., ≥50% and <100% reduction in the tophus area without enlargement of any existing tophus and no new tophus) and complete response (i.e., 100% reduction in area of or complete disappearance of a tophus without enlargement of any existing tophus and no new tophus).

The Results

At week 24, among patients with tophi at baseline, a tophus response of partial or better was seen in:

• 82% (P=0.0077) of patients in the high-dose NASP group;
• 88% (P=0.0016) of patients in the low-dose NASP group; and
• 51% of patients in the placebo group.

At week 24, a clinically relevant rate of complete response was observed in significantly more patients treated with NASP than those who received placebo. Complete response rates were:

• 31% (P=0.0044) of patients in the high-dose NASP group;
• 48% (P=0.0001) of patients in the low-dose NASP group; and
• 5% of patients in the placebo group.

Additionally, investigators examined a subset of study patients with tophi at baseline who received six NASP doses. A significantly greater proportion of these patients had a complete response by week 24 than those who received placebo. For this subset of patients, 49% (P=0.0002) who received high-dose NASP had a complete response, 70% (P<0.0001) who received low-dose NASP had a complete response, and 5% who received placebo had a complete response.

Correlating tophus reduction and serum uric acid reduction at the end of the study, patients who received six doses of NASP had 89% lower serum uric acid levels than patients who were treated with placebo. This analysis shows the effectiveness of NASP in lowering serum uric acid and promoting tophus resolution in patients with uncontrolled gout.

Michele B. Kaufman, PharmD, BCGP, is a freelance medical writer based in New York City and a pharmacist at New York Presbyterian Hospital – Lower Manhattan.

References

1. Ursani M. Understanding gout symptoms and treatment. American College of Rheumatology. 2023 Apr 27.      
2. FDA accepts biologics license application for Sobi’s NASP for patients with uncontrolled gout [news release]. Sobi. 2025 Sep 10.
3. A study of SEL-212 in patients with gout refractory to conventional therapy (DISSOLVE I) [NCT04513366]. ClinicalTrials.gov. 2025 Sep 11.
4. A study of SEL-212 in patients with gout refractory to conventional therapy II (DISSOLVE II) [NCT04596540]. ClinicalTrials.gov. 2024 Feb 20.
5. Baraf H, Khanna P, Lioté F, et al. Reduction in tophi observed in patients with uncontrolled gout treated with NASP: Results from phase 3 DISSOLVE studies [abstract 1998]. Arthritis Rheumatol. 2025;77(suppl 9).