SAN DIEGO, May 26, 2026 /PRNewswire/ — Crystalys Therapeutics Inc. (‘Crystalys’ or ‘the Company’), a clinical-stage biopharmaceutical company addressing the significant unmet medical needs of people living with gout, today announced that the first patients have been dosed in its new randomized, double-blind, placebo-controlled, multicenter Phase 2 AMETHYST study (NCT07535034) evaluating the efficacy of dotinurad in participants with gout who are intolerant to xanthine oxidase inhibitors (XOIs) or have failed uricase treatment.

Dotinurad is a next-generation, once daily, oral URAT1 inhibitor with the potential to deliver best-in-class safety and efficacy for the treatment of gout, particularly in patients with limited treatment options.

“Dosing the first patient in our Phase 2 AMETHYST study marks an important milestone for Crystalys and for those living with gout who have limited treatment options,” said James Mackay, Ph.D., President and Chief Executive Officer of Crystalys Therapeutics. “This study builds on our broader clinical development program, including the ongoing Phase 3 RUBY and TOPAZ trials, and reinforces our commitment to advancing comprehensive treatment options for patients with gout.”

Nihar Bhakta, MD, Chief Medical Officer of Crystalys Therapeutics, added, “Many patients cannot take or tolerate existing therapies to achieve target uric acid levels and adequate control of gout flares. We believe dotinurad has the potential to address this unmet need.”

About the AMETHYST Study

The AMETHYST study (NCT07535034) is a U.S, Phase 2, randomized, double-blind, placebo-controlled, multicenter study to evaluate the safety and efficacy of dotinurad in approximately 90 patients with gout who are intolerant or have a contraindication to XOIs or have failed uricase treatment. The study will consist of two consecutive parts: a 24-week placebo-controlled period where participants will take either dotinurad or placebo (Treatment Period 1) followed by a 12-week active treatment period where all participants will take dotinurad (Treatment Period 2).

About Gout

Gout is the most common form of inflammatory arthritis. It is a condition that is very debilitating for patients and characterized by sudden, severe attacks of pain, swelling, redness and tenderness in one or more joints. This disease arises from excess uric acid in the body, known as ‘hyperuricemia,’ which causes buildup of uric acid crystals and inflammation, which can lead to tophaceous gout in people with chronic or undertreated disease. Despite available therapies that aim to reduce uric acid levels below the target 6 mg/dL, a major treatment gap remains between first-line xanthine oxidase inhibitors and last-line uricase therapy. Currently, no suitable second-line options exist in the U.S. or E.U., leaving a critical unmet need for patients who fail to respond to first-line treatments.

About Crystalys Therapeutics

Crystalys Therapeutics is a clinical-stage biopharmaceutical company transforming the treatment of gout. Headquartered in San Diego, California, and co-founded by Catalys Pacific and Novo Holdings, Crystalys brings together a world-class team with deep expertise in gout drug development, dedicated to delivering more effective options for people living with gout. The company’s lead candidate, dotinurad, is a next-generation, once daily oral, URAT1 inhibitor in clinical development as a second-line therapy aimed to reduce uric acid, gout flares and tophi. Dotinurad was invented by Fuji Yakuhin and has obtained regulatory approval in Japan, China, the Philippines, Taiwan and Thailand. With best-in-class potential for both safety and efficacy, dotinurad is supported by clinical data from multiple Asian markets where it is approved. Crystalys is advancing dotinurad in global Phase 3 trials toward regulatory approval and commercial launch.

For more information, visit www.crystalystx.com/ and follow us on X and LinkedIn.

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SOURCE Crystalys Therapeutics