FDA Grants Fast Track Designation to Sobi's Pacritinib for VEXAS Syndrome
核心洞察
The FDA has granted Fast Track designation to Sobi (搜索)'s dual IRAK1 (搜索)/JAK2 (搜索) inhibitor pacritinib for the treatment of VEXAS syndrome (搜索), a rare autoinflammatory disease with no approved therapies.
Pacritinib is being evaluated in the Phase 2 PAXIS trial, the first randomized study in VEXAS, assessing whether the drug prevents disease flares after glucocorticoid tapering.
PAXIS is a randomized, multicenter, double-blind, placebo-controlled, dose-finding trial followed by an open-label period, with topline data expected in 2027.
The US Food and Drug Administration has granted Fast Track designation to pacritinib for the treatment of VEXAS syndrome (搜索), Sobi (搜索) North America, the North American affiliate of Swedish Orphan Biovitrum AB, announced on September 9, 2026. Pacritinib is a dual IRAK1 (搜索)/JAK2 (搜索) inhibitor currently in Phase II development for the condition.
Fast Track designation is designed to facilitate the development and expedite the review of medicines intended to treat serious conditions that may fill an unmet medical need.
"Achieving FDA's Fast Track designation for pacritinib is an important milestone and recognizes its potential as an investigational treatment for people living with VEXAS syndrome (搜索)," said Lydia Abad-Franch, MD, Head of R&D and Medical Affairs and Chief Medical Officer at Sobi (搜索). "There is a critical need for new treatment options for people living with this debilitating condition, who often face serious complications and limited therapeutic choices. With this designation, we look forward to working even more closely with the FDA as we accelerate the clinical evaluation of pacritinib and continue to work towards approval for patients with VEXAS syndrome."
A Disease With No Approved Options
VEXAS syndrome (搜索) (Vacuoles in blood-cell precursors, E1 enzyme, X-linked, Autoinflammatory, Somatic) is a systemic disorder characterized by an overlap of hematologic and inflammatory features. It was first described in 2020. The condition is potentially life-threatening, primarily affects older adults, and can cause severe systemic inflammation, blood abnormalities and damage to multiple organs. It can be progressive and debilitating, with patients experiencing involvement of multiple organ systems and potentially life-threatening complications.
Treatment poses a challenge, as most immunomodulators fail to control the disease, resulting in a requirement for moderate to high doses of glucocorticoids. There are currently no FDA-approved therapies specifically for VEXAS syndrome (搜索).
The PAXIS Trial
Since 2024, Sobi (搜索) has been evaluating pacritinib in VEXAS syndrome (搜索) through the PAXIS study, described as the first randomized trial for this condition. PAXIS (NCT06782373) is a Phase II, randomized, multicenter, double-blind, placebo-controlled, dose-finding trial followed by an open-label period. The study is designed to evaluate the efficacy and safety of pacritinib in preventing disease flares in patients with VEXAS syndrome following glucocorticoid tapering.
Topline data from the trial are expected in 2027. The study design was described in the Journal of Clinical Medicine in 2026.
Existing Myelofibrosis Indication
Pacritinib is marketed by Sobi (搜索) as VONJO in the United States for the treatment of adults with intermediate or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis (搜索) with a platelet count below 50 × 109/L. That indication is approved under accelerated approval based on spleen volume reduction, and continued approval may be contingent upon verification and description of clinical benefit in confirmatory trials.
VONJO carries serious risks described in its labeling, including severe bleeding that can be serious and in some cases lead to death, diarrhea that can be severe and cause dehydration, worsening low platelet counts, and QTc prolongation that can cause life-threatening irregular heartbeats. The label also notes increased risks observed with another Janus associated kinase (JAK) inhibitor in rheumatoid arthritis, including major cardiovascular events such as heart attack, stroke or death in people with cardiovascular risk factors who are current or past smokers, blood clots including deep vein thrombosis and pulmonary embolism, new secondary cancers, and serious infections. The most common side effects of VONJO include nausea, vomiting, anemia and swelling of the ankles, legs and feet. VONJO may affect fertility in males.
Company Background
Sobi (搜索) is a global biopharma company focused on rare diseases, with approximately 2,000 employees across Europe, North America, the Middle East, Asia and Australia. In 2025, revenue amounted to SEK 28 billion, and the company's share (STO:SOBI) is listed on Nasdaq Stockholm. Sobi shares closed at SEK 443.20 on the Wednesday preceding the announcement, down 3.02%.