Crystalys Therapeutics Advances Phase 3 Trials of Dotinurad for the Treatment of Gout with Dosing of First Patients

SAN DIEGO, Oct. 21, 2025 /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 two randomized, double-blind, multicenter Phase 3 trials, the RUBY study (NCT07089875) and the TOPAZ study (NCT07089888), evaluating dotinurad, a next-generation, once daily oral, URAT1 inhibitor with potential for best-in-class safety and efficacy for the treatment of gout.

These Phase 3 clinical studies are designed to evaluate the safety and efficacy of dotinurad compared to an active control arm (physician-determined stable dose of allopurinol) in adults with hyperuricemia associated with gout (RUBY) and adults with tophaceous gout (TOPAZ). To learn more, visit the JEWEL program here.

"Dosing the first patients in our Phase 3 RUBY and TOPAZ studies marks a significant milestone for Crystalys and for the gout community," said James Mackay, Ph.D., President and Chief Executive Officer of Crystalys Therapeutics. "Despite existing therapies, many patients continue to experience uncontrolled disease. Dotinurad's differentiated profile offers the potential to help improve disease symptoms for these patients. These studies are designed to confirm its best-in-class potential while supporting future regulatory filings in the U.S. and Europe. We are proud to be advancing this important program and bringing a new, effective, and well-tolerated treatment option closer to patients in need."

About the RUBY Study

The RUBY study (NCT07089875) is a Phase 3, randomized, double-blind, multicenter study to evaluate the safety and efficacy of dotinurad in approximately 500 patients with hyperuricemia associated with gout. Study participants will be given dotinurad orally once a day for up to 64 weeks.

About the TOPAZ Study

The TOPAZ study (NCT07089888) is a Phase 3, randomized, double-blind, multicenter study to evaluate the safety and efficacy of dotinurad in approximately 250 patients with tophaceous gout. Study participants will be given dotinurad orally once a day for up to 76 weeks.

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, leading 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 (XOIs) 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, Philippines 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.

SOURCE Crystalys Therapeutics