Arthrosi to Present Positive Phase 2 Data for its Novel Selective URAT1 Inhibitor AR882 in Patients with Tophaceous Gout at ACR Convergence 2023

Arthrosi Therapeutics, Inc., a clinical-stage biotechnology company developing treatments for gout that dissolve uric acid crystals and prevent joint damage, today announced new clinical data from its phase 2 AR882-203 study in patients with tophaceous gout. The late-breaking data will be presented as an oral presentation at the American College of Rheumatology (ACR) Convergence 2023 meeting, being held in San Diego, CA on November 10-15, 2023.

In the forthcoming late-breaking oral presentation, Dr. Robert Keenan MD, MPH, MBA, Chief Medical Officer of Arthrosi, will unveil compelling new clinical findings from the phase 2 trial. The data showcases the strong efficacy of AR882, demonstrating significant reduction of tophi, crystal burden, flare rates, in addition to lowering sUA among patients suffering from tophaceous gout.

In the intent-to-treat population, AR882 demonstrated a significant decrease in sUA at 3 months. Notably, in the 75 mg AR882 group, 86% and 64% of patients achieved sUA levels below 6 and 5 mg/dL, respectively, compared to 77% and 69% in the 50 mg AR882 + allopurinol group and 46% and 23% in the allopurinol group.

Significantly higher response rates in total crystal volume reduction were observed by Dual Energy Computed Tomography (DECT) imaging. Specifically, the AR882 75 mg group showed a notable reduction in total urate crystal volume (-8.3 cm3, baseline 15.6 cm3) compared to allopurinol (-1.2 cm3, baseline 11.5 cm3) or combination (-0.9 cm3, baseline 4.7 cm3) on DECT at Month 6. (Figure 1 illustrates DECT images of one severe gout patient’s crystal burden at baseline (left) and at 6 months following QD treatment of 75 mg AR882).

Consistent with DECT imaging, AR882 75 mg demonstrated significantly higher response rate of at least 1 complete target tophi dissolution by caliper measurement than allopurinol 300 mg, or allopurinol 300 mg in combination with AR882 50 mg. These clinical findings, highlighted via both DECT and caliper, underscore the effectiveness of AR882 in reducing urate crystal burden, further substantiating its potential as a groundbreaking therapeutic solution for patients.

“We are excited to share new data from our phase 2 tophaceous gout study at ACR highlighting its potential to significantly improve the standard of care for a broad range of patients living with gout,” said Arthrosi’s Chief Executive Officer Litain Yeh, PhD. “Importantly, in the case of patients with tophaceous gout, there remains a high unmet need for a safe, efficacious and convenient therapy to reduce sUA levels below 5 mg/dL, which has been established in the literature as necessary to quickly resolve and reduce debilitating symptoms associated with tophi and flares.” 


Details for the presentations are below:

Title: AR882, an Efficacious and Selective URAT1 Inhibitor for Patients with Chronic Gouty Arthritis and Subcutaneous Tophi: Results from a Global, Prospective, Proof-of-Concept Trial Using Dual Energy Computed Tomography

Session Title: Late-Breaking Abstracts

Abstract Number: #1651889

Date/Time: Wednesday, November 15 / 7:30am – 7:45am PST


Arthrosi will present three additional posters at ACR highlighting results from its previously completed phase 2b AR882-202 study evaluating AR882 in chronic gout patients. The phase 2b study was a global, multicenter, 12-week, randomized, double-blind, placebo-controlled study of 140 gout patients who met the gout classification according to the American College of Rheumatology (ACR) and The European Alliance of Associations for Rheumatology (EULAR).


Title: Efficacy and Safety of AR882, a Selective Uric Acid Transporter 1 (URAT1) Inhibitor, in Gout Patients with Various Baseline Characteristics Following 12-Week Treatment in Patients

Session Title: Metabolic & Crystal Arthropathies – Basic & Clinical Science Poster I

Abstract Number: #1553555

Date/Time: Sunday, November 12 / 9:00am – 11:00am PST


Title: Pharmacokinetics and Pharmacodynamics of AR882 Following 12-Week Treatment in Patients with Gout

Session Title: Metabolic & Crystal Arthropathies – Basic & Clinical Science Poster II

Abstract Number: #1553704

Date/Time: Monday, November 13 / 9:00am – 11:00am PST


Title: AR882, A Potent Uricosuric Agent, Shows Favorable Uric Acid Excretion Profile Following Multiple Doses

Session Title: Metabolic & Crystal Arthropathies – Basic & Clinical Science Poster II

Abstract Number: #1552575

Date/Time: Monday, November 13 / 9:00am – 11:00am PST


All four poster presentations will be available in the “Publications” section of Arthrosi’s website:


About the AR882-203 Phase 2 Study

The Phase 2 study of AR882 in patients with tophaceous gout was a six-month, 1:1:1 randomized, global, placebo-controlled study of 42 patients with subcutaneous tophi. The mean baseline sUA among the participants ranged between 9.1-9.6 mg/dL. In the study, patients received a once daily dose of either 75 mg AR882, 50mg AR882 + allopurinol, or allopurinol up to 300mg. Serum uric acid levels (< 6, <5, <4, or <3 mg/dL) were evaluated monthly through month 6, and safety and tolerability were assessed throughout the study. Tophi measurements with calipers were completed every 4 weeks for 6 months. Patients were also imaged using Dual-Energy Computed Tomography (DECT), DECT a specialized imaging technique that is able to differentiate and identify uric acid crystals in the joints and soft tissue, allowing for quantifying uric acid crystals and tophi at baseline and 6 months. The primary efficacy endpoint was sUA change at 3 months. Secondary endpoints included complete resolution of at least one target tophus with no new tophi and no tophus showing progression. Safety assessments, including vital signs and electrocardiograms, were collected throughout the study. 


About Gout:

In the U.S., an estimated 10 million individuals are diagnosed with gout. Gout is a form of inflammatory arthritis that can significantly diminish mobility, functionality, and overall quality of life. Gout emerges from the crystallization of uric acid within the joints and soft tissue, instigating painful flare-ups and chronic symptoms. The kidneys play a pivotal role in the process, as they are responsible for filtering out and excreting uric acid from the body. Elevated sUA levels often signify an imbalance in production or excretion of uric acid and acts as an early indicator of potential gout development. Consistent, elevated sUA levels have been identified as a precursor to gout attacks and related complications. It’s essential to monitor and manage sUA levels as part of comprehensive gout treatment and prevention strategies.


About Arthrosi:

Arthrosi Therapeutics, Inc., headquartered in San Diego, CA, was established in 2018. The company’s goal is to develop potential treatments aimed at uric acid levels and minimizing joint damage for gout patients. Arthrosi anticipates initiating pivotal phase 3 program in early 2024.


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