GSK's momelotinib receives orphan drug designation from US and EU watchdogs.

Drugmaker GSK said on Friday that its JAK inhibitor momelotinib has been granted orphan drug designation by both the US Food and Drug Administration and the European Medicines Agency for the treatment of VEXAS syndrome, a rare and severe autoinflammatory condition with no approved therapies.

GSK
12 June 2026 08:17:35

Source: Sharecast

GSK said the designations were supported by retrospective case studies suggesting JAK inhibitors may offer clinical benefit, as well as a case report indicating improvements in symptoms, inflammation and haematological markers with momelotinib.

The FTSE 100-listed company plans to evaluate the drug in VEXAS through its upcoming phase II/III ATLAS trial, which will support future global regulatory submissions. The trial forms part of a broader development programme assessing momelotinib across multiple haematological conditions.

Momelotinib, marketed as Ojjaara/Omjjara, has already been approved in the US for intermediate‑ or high‑risk myelofibrosis in adults with anaemia, and in the EU, UK and Japan for myelofibrosis with splenomegaly or disease‑related symptoms in patients with moderate to severe anaemia.

As of 0815 BST, GSK shares were up 1.14% at 1,984.80p.

Reporting by Iain Gilbert at Sharecast.com

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