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Momelotinib orphan drug designations for VEXAS
GSK announced that its drug momelotinib has received Orphan Drug Designation from both the US FDA and the European Medicines Agency for the treatment of VEXAS syndrome, a rare and life-threatening condition with no current approved treatments. This designation supports the ongoing development of momelotinib, including the planned ATLAS phase II/III trial, and follows retrospective case studies and a case report indicating potential clinical benefit. Momelotinib is already approved in the US, EU, UK, and Japan for myelofibrosis. Disclaimer*
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Issued: 12 June 2026, London UK GSK's momelotinib granted Orphan Drug Designations in the US and EU for VEXAS syndrome · VEXAS syndrome is a rare, life-threatening haemato-inflammatory condition with no approved treatments · ATLAS phase II/III trial in VEXAS underway, advancing momelotinib's broader development programme · Designations support development efforts and regulatory evaluations for medicines with potential to treat or prevent rare disorders GSK plc (LSE/NYSE: GSK) today announced that momelotinib, a JAK inhibitor with a differentiated mechanism of action, has received Orphan Drug Designation (ODD) from the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of VEXAS (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic) syndrome. VEXAS syndrome is a clonal myeloid disorder with rheumatologic and haematologic clinical features. It is a highly symptomatic progressive condition with poor prognosis and a 30-40% five-year mortality rate.[1] There are currently no approved treatment options. The ODDs were supported by retrospective case studies demonstrating that JAK inhibitors may be an effective therapeutic option for VEXAS syndrome as well as evidence from a case report that indicated potential clinical benefit from treatment with momelotinib, including improvements in symptoms and VEXAS-related inflammation and haematological manifestations.[2] ODDs are granted by regulators to support the development efforts and regulatory evaluations of new medicines that have the potential to treat or prevent rare disorders. The planned phase II/III ATLAS trial will evaluate momelotinib's efficacy and safety in VEXAS syndrome and will support planned global regulatory submissions.[3] The study design will be presented at the 2026 European Hematology Association (EHA) Congress taking place 11-14 June. The trial is part of momelotinib's ongoing development programme evaluating its potential across multiple haematological conditions. Momelotinib (Ojjaara/Omjjara) is currently approved in the US for the treatment of intermediate- or high-risk myelofibrosis in adults with anaemia. It is also approved in the EU and UK for the treatment of myelofibrosis with disease-related splenomegaly or symptoms in adults with moderate to severe an...