Sobi acquires startup Arthrosi Therapeutics for $950 million to expand gout drug prospects
Sobi currently has a drug under FDA review as a late-stage treatment for gout, and the company is spending $950 million to acquire Arthrosi Therapeutics, a startup with a gout drug candidate in Phase 3 development that offers a different approach and the potential for use as an early treatment for the popular arthritis disease.
While there are medications to treat gout, they either have limited effectiveness or carry dangerous risks of complications. The Arthrosi acquisition, announced Monday, enables Stockholm-based Sobi to address the needs of patients underserved by existing gout treatments, while also providing the company with product candidates expected to contribute to its sales growth targets.
In gout, high uric acid levels in the blood cause urate crystals to form in the joints, causing inflammation and pain. The standard treatment is allopurinol, a 60-year-old drug that inhibits a key enzyme in uric acid production. But many patients find that their disease does not respond adequately to this oral small molecule.
San Diego-based Arthrosi's lead drug candidate is pozdeutinurad (formerly AR882), an oral small molecule designed to inhibit URAT1, a transporter that enables the kidneys to absorb uric acid. By blocking URAT1, this once-daily capsule is designed to promote the excretion of uric acid in the urine, thereby reducing levels of this compound in the body.
For patients who do not respond to allopurinol, the current second-line treatment is febuxostat, sold under the brand name Uloric. The Takeda Pharmaceutical drug works similarly to allopurinol but carries a boxed warning about the risk of potentially fatal cardiovascular complications. Takeda said it would discontinue Uloric by the end of March; generic versions of the drug are already on the market. In third-line treatment, patients can take Amgen's Krystexxa, an engineered version of uricase, an enzyme that breaks down uric acid. But patients may develop antibodies against the therapy, rendering it ineffective.
Sobi's gout drug candidate is also an engineered version of uricase. Pegadricase (formerly SEL-212) is made with technology that reduces the immune response to treatment. The drug pairs nanoencapsulated sirolimus, an immunosuppressant, with the enzyme pegylated enzyme, or NASP. In 2020, Sobi acquired global rights (excluding China) to Selecta Biosciences' gout drug candidate. In phase III testing, monthly infusions of the drug led to statistically significant reductions in uric acid levels in the blood. NASP is currently under FDA review as a treatment for gout that cannot be controlled despite use of urate-lowering therapy. The FDA is expected to make a decision by the end of June.
In an investor presentation on Monday, Sobi said Arthrosi's pozdeutinurad complements NASP. NASP will offer third-line treatment, obviating the need for systemic oral immunosuppression, while pozdeutinurad offers a once-daily treatment option in the second-line setting. In phase 2 testing, Arthrosi reported continued reductions in uric acid levels in the blood and dissolution of tophi (deposits of uric acid crystals in joints and surrounding tissue). Two placebo-controlled Phase 3 studies evaluating URAT1 inhibitor capsules are fully enrolled; preliminary data are expected in the second quarter of 2026.
Sobi is short for Swedish Orphan Biovitrum, and for much of the company's history, its focus has been on orphan or rare diseases. The company reported 2024 revenue of SEK 26 billion (approximately $2.7 billion), primarily in the areas of hematology and immunology treatments. Through his research on gout, Thorby's scope is broadening to include a common disease. An estimated 8.3 million people in the United States are diagnosed with gout. Sobi calculates that more than 200,000 patients with uncontrolled gout may be eligible for Arthrosi in the United States alone.
“The acquisition of Arthrosi allows us to expand our gout product pipeline with highly differentiated new assets,” Sobi President and CEO Guido Oelkers said in a prepared statement. “Pozdeutinurad has the potential to become the treatment of choice for patients with progressive gout who have persistent and unresolved symptoms despite first-line therapy. This product has the potential to significantly accelerate our growth in the mid-2030s and beyond.”
Sobi may face competition from another URAT1 inhibitor. In September, startup Crystallys Therapeutics raised $205 million to fund two Phase 3 tests of its small molecule dotinurad. Like Arthrosi, Crystallys claims its URAT1 inhibitor could offer safety and efficacy advantages over currently available gout drugs. Two Phase 3 trials of dotinurad are ongoing; preliminary data are expected in 2027.
In October, Arthrosi raised $153 million to fund Phase 3 testing of pozdeutinurad. In addition to Sobi's upfront payment, terms of the acquisition also net the startup up to $550 million in milestone payments. The companies expect to complete the transaction in the first half of next year.
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