California-based Crystalys Therapeutics has emerged from stealth with $205 million in Series A funding to advance dotinurad, an oral URAT1 blocker for gout treatment that has already demonstrated clinical success across multiple Asian markets. The substantial funding round positions the company among the highest Series A raises this year, trailing only Verdiva Bio's $411 million obesity-focused raise in January.
Addressing Critical Treatment Gaps in Gout Management
The biotech is targeting a significant unmet medical need in gout treatment, a condition affecting an estimated 56 million people worldwide. Gout, a form of arthritis caused by excess uric acid buildup in the body, typically manifests as sudden, severe joint pain episodes known as "gout attacks," most commonly affecting the big toe joint.
Current treatment options remain limited despite decades of clinical use. While allopurinol serves as the standard of care by hindering uric acid production, approximately half of patients taking this medication still have uncontrolled disease. Alternative options include febuxostat, which sees limited U.S. use due to associated cardiovascular risks, and Krystexxa, an expensive infusion therapy that generated $1.2 billion in sales last year for Amgen following its acquisition of Horizon Therapeutics.
"The second-line treatment space is empty," said James Mackay, Crystalys' cofounder and CEO, highlighting the therapeutic gap the company aims to address.
Dotinurad's Established Clinical Profile
Dotinurad represents a next-generation approach to gout treatment, functioning as an orally available URAT1 blocker that lowers serum uric acid levels and prevents crystal formation in joints. Originally discovered by Japanese firm Fuji Yakuhin, the drug received approval in Japan in 2020 and has since expanded to additional markets.
Under an August 2021 agreement, Eisai holds rights to dotinurad in China and several Southeast Asian countries. The drug secured Chinese approval in 2025, supported by Phase III data demonstrating superior uric acid reduction compared to Takeda's Uloric. Marketing approvals have also been granted in the Philippines and Thailand.
According to Mackay, dotinurad offers key advantages over previous URAT1 blockers, including more specific binding to the transporter protein and slower uric acid elimination that should provide kidney protection. This represents a significant improvement over Zurampic, which Mackay helped develop at Ardea Biosciences and AstraZeneca before its market withdrawal in 2019 due to kidney damage concerns.
"The label in Japan really has not changed in the five years it has been on the market, and that's actually very reassuring from a safety perspective," Mackay noted.
Strategic Development and Investor Support
Crystalys acquired U.S. and European rights to dotinurad from a Fortress Bio subsidiary in July, subsequently securing FDA agreement to proceed directly to global Phase III testing based on existing Asian trial data. The company plans to focus these studies on patients who don't respond to initial gout therapies.
The Series A funding round was co-led by Novo Holdings, SR One, and Catalys Pacific, with participation from more than a dozen firms including Alexandria Venture Investments, Lightstone Ventures, and AN Venture Partners. Novo Holdings previously invested in Aristea Therapeutics, another Mackay-founded startup.
Competitive Landscape and Market Opportunity
Crystalys joins several biotechnology companies developing new gout treatments, including San Diego-based Arthrosi Therapeutics, which has a candidate in Phase III testing. Despite potential competition, Mackay expressed confidence in the market opportunity.
"We feel that the unmet medical need is so large here that even if multiple of these drugs were approved, there's certainly room for this, and patients need other treatment options," he said.
The substantial funding and dotinurad's established regulatory profile across multiple markets provide Crystalys with a strong foundation for advancing global development of what could become a significant addition to the limited gout treatment armamentarium.
