GSK’s momelotinib gains orphan drug status in US and EU for VEXAS
- Momelotinib received Orphan Drug Designation from both the FDA and EMA for the treatment of VEXAS syndrome.
- The planned ATLAS phase II/III trial (NCT07569081) will evaluate momelotinib’s efficacy and safety in VEXAS and its design will be presented at the 2026 EHA Congress (11–14 June).
- VEXAS is a clonal myeloid haemato‑inflammatory disorder with no approved treatments and a reported five‑year mortality of 30–40%.
- Momelotinib is approved for myelofibrosis in the US, EU, UK and Japan and inhibits JAK1, JAK2 and ACVR1, with ACVR1 inhibition linked to decreased hepcidin and possible anaemia benefit.
Regulatory update
GSK’s JAK inhibitor momelotinib has been granted Orphan Drug Designation by the US Food and Drug Administration and the European Medicines Agency for the treatment of VEXAS syndrome. The designations were supported by retrospective case series suggesting JAK inhibitors may be effective in VEXAS and by a case report indicating clinical benefit from momelotinib, including symptom and inflammation improvements and effects on haematological manifestations.
Clinical development
The ATLAS phase II/III study (ClinicalTrials.gov identifier NCT07569081) is planned to evaluate momelotinib’s efficacy and safety in participants with VEXAS syndrome and to support planned global regulatory submissions; the study design will be presented at the 2026 European Hematology Association Congress (11–14 June). This trial is part of momelotinib’s broader programme across haematological conditions.
Drug profile
Momelotinib (Ojjaara/Omjjara) is approved for intermediate‑ or high‑risk myelofibrosis with anaemia in the US and for myelofibrosis with disease‑related splenomegaly or symptoms in adults with moderate to severe anaemia in the EU and UK, and is also approved in Japan. It inhibits JAK1, JAK2 and ACVR1; JAK inhibition may improve constitutional symptoms and splenomegaly, while ACVR1 inhibition has been linked to decreased circulating hepcidin and potential anaemia‑related benefit.
About VEXAS syndrome
VEXAS is a recently classified clonal myeloid disorder combining rheumatologic and haematologic features, characterised by severe inflammatory manifestations and frequent haematologic complications such as macrocytic anaemia and thrombocytopenia. Diagnosis is confirmed by testing for somatic UBA1 mutations; the condition predominantly affects men over 50 and currently has no approved treatments.
Source: GSK
