Crystalys Therapeutics has raised $130 million in series B financing to advance the development of its gout drug dotinurad and prepare for a potential commercial launch.
The financing comes less than a year after Crystalys emerged from stealth with an impressive $205 million series A round in September 2025.
Frazier Life Sciences led the latest round, with participation from new investors Wellington Management, HBM Healthcare Investments, Soleus Capital and Cormorant Asset Management, among others. All of Crystalys’ existing investors also participated, including Novo Holdings, SR One and Catalys Pacific.
“It was one of the fastest financings that I've ever participated in,” Crystalys CEO James Mackay, Ph.D., told Fierce. “Last year we raised our $205 million series A. I think that made a lot of investors who didn't participate in that sit up and take notice.”
The proceeds will support two ongoing, registration-directed phase 3 trials, as well as the phase 2 Amethyst study. Crystalys also plans to use the money to prepare for dotinurad’s potential commercialization. The financing is expected to extend the company’s runway through multiple clinical and regulatory milestones.
Dotinurad is a once-daily oral inhibitor of urate transporter 1 (URAT1), designed to help the kidneys excrete uric acid. Excess uric acid can lead to the formation of crystals in the joints, causing the painful inflammation associated with gout.
Mackay described dotinurad as an extremely “de-risked molecule” because it has already been approved in several Asian markets. The drug, originally developed by Japanese drugmaker Fuji Yakuhin, is approved in Japan, China, the Philippines, Taiwan and Thailand.
Crystalys acquired the rights to dotinurad from Urica Therapeutics in July 2024. In exchange, Urica received common stock representing 35% of Crystalys’ outstanding equity and a 3% royalty on future net sales.
Drawing on clinical data generated in Asia and earlier U.S. studies, Crystalys secured regulators’ support to move directly into late-stage development in the U.S. and Europe. The phase 3 Ruby trial is comparing dotinurad with allopurinol in patients with hyperuricemia associated with gout, while the phase 3 Topaz trial is evaluating the same treatments in patients with tophaceous gout.
FDA-approved urate-lowering treatments include the xanthine oxidase inhibitors allopurinol and febuxostat. Febuxostat’s label carries a boxed warning about an increased risk of cardiovascular death in patients with established cardiovascular disease and limits its use to patients who do not respond adequately to allopurinol, cannot tolerate it or should not receive it.
Mackay said roughly half of patients treated with existing first-line drugs reach their treatment goals. For patients whose chronic gout remains uncontrolled despite treatment with xanthine oxidase inhibitors, one option is Krystexxa, an intravenous therapy administered every two weeks alongside weekly methotrexate.
“There's a massive unmet medical need in the second line space,” Mackay told Fierce.
San Diego-based Crystalys was formed in 2022 and co-founded by Mackay, Novo Holdings, Catalys Pacific and other members of its leadership team. Mackay previously led Aristea Therapeutics, an AstraZeneca spinout that shut down in 2023 after safety concerns emerged in a clinical trial of its lead inflammatory disease drug. Before that, he led Ardea Biosciences and helped develop Zurampic, the first URAT1 inhibitor approved in the U.S.
Now, with dotinurad in late-stage development and Crystalys newly flush with cash, Mackay is considering the company’s longer-term financing options. With the biotech market “reasonably buoyant” at the moment, he said Crystalys could pursue an IPO. For now, he expects the series B proceeds to give the company enough cash to operate “at least a year beyond the phase 3 data readouts.”