Sobi, which currently has a drug under FDA review as a later line of therapy for gout, is paying $950 million to acquire Arthrosi Therapeutics, a startup with a gout drug candidate in Phase 3 development offering a different approach and the potential for use as an earlier treatment for the prevalent arthritic disorder.
While drugs for gout are available, they either offer limited efficacy or come with dangerous complication risks. The Arthrosi acquisition announced Monday puts Stockholm-based Sobi in position to address patients who are underserved by existing gout treatments while also providing the company with a product candidate poised to contribute to its sales growth goals.
In gout, high levels of uric acid in the blood lead to the formation of urate crystals in joints, causing inflammation and pain. Standard treatment is allopurinol, a 60-year-old drug that inhibits an enzyme key to uric acid production. But many patients find their disease does not respond adequately to this oral small molecule.
The lead drug candidate of San Diego-based Arthrosi is pozdeutinurad (formerly AR882), an oral small molecule designed to inhibit URAT1, a transporter protein that enables the absorption of uric acid by the kidneys. By blocking URAT1, this once-daily capsule is intended to lead to more excretion of uric acid in urine, reducing levels of this compound in the body.
For patients who do not respond to allopurinol, the current second-line treatment is febuxostat, brand name Uloric. This Takeda Pharmaceutical drug works similarly to allopurinol, but carries a black box warning for the risk of potentially fatal cardiovascular complications. Takeda has said it will discontinue Uloric at the end of March; generic versions of this drug are already available. In the third-line setting, patients can take Amgen’s Krystexxa, which is an engineered version of uricase, an enzyme that breaks down uric acid. But patients can develop antibodies against the therapy that render 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 the therapy. The drug, which pairs nanoencapsulated sirolimus (an immunosuppressant) with pegadricase, is called NASP for short. In 2020, Sobi licensed global rights, excluding China, to this Selecta Biosciences gout drug candidate. In Phase 3 testing, the once-monthly infused drug led to statistically significant reduction in uric acid levels in the blood. NASP is currently under FDA review as a treatment for of gout that is uncontrolled despite use of urate-lowering therapies. An FDA decision expected by late June.
In a Monday investor presentation, Sobi said Arthrosi’s pozdeutinurad complements NASP. While NASP would offer a third-line treatment that avoids the need for systemic oral immunosuppression, pozdeutinurad offers a once-daily treatment option in the second-line setting. In Phase 2 testing, Arthrosi reported sustained reduction of uric acid levels in the blood and dissolution of tophi, the deposits of uric acid crystals in joints and surrounding tissue. Two placebo-controlled Phase 3 studies are fully enrolled evaluating the URAT1-inhibiting capsule; 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 26 billion Swedish krona (about $2.7 billion) in revenue for 2024, mainly in the therapeutic areas of hematology and immunology. By pursuing gout, Sobi’s scope is expanding to a common disorder. An estimated 8.3 million people in the U.S. have been diagnosed with gout. Sobi calculates that there are more than 200,000 people alone in the U.S. with uncontrolled gout that could be eligible for the Arthrosi drug.
“The acquisition of Arthrosi allows us to expand our gout pipeline with a highly differentiated new asset,” Sobi President and CEO Guido Oelkers said in a prepared statement. “Pozdeutinurad has the potential to become the therapy of choice for patients who have progressive gout with persistent and unresolved symptoms despite first-line therapy. The product has the potential to materially accelerate our growth until the mid-2030s, and beyond.”
Sobi could face competition from another URAT1 inhibitor. In September, startup Crystalys Therapeutics raised $205 million to finance two Phase 3 tests of its small molecule, dotinurad. Similar to Arthrosi, Crystalys claims its URAT1 inhibitor could offer safety and efficacy advantages over currently available gout medications. Two Phase 3 tests of dotinurad are underway; preliminary data are expected in 2027.
In October, Arthrosi raised $153 million to finance pozdeutinurad’s Phase 3 tests. Beyond the upfront payment from Sobi, the acquisition terms put the startup in line for up to $550 million in milestone payments. The companies expect to complete the transaction in the first half of next year.
Photo: maxsattana, Getty Images
