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JAK1/JAK2/ACVR1 inhibitor

Momelotinib (Specialist drug)

Brand names: Omjjara

Momelotinib is an oral JAK inhibitor used, under specialist supervision, for disease-related splenomegaly or symptoms in adults with myelofibrosis who have moderate to severe anaemia.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits JAK1, JAK2 and the activin receptor ACVR1, reducing inflammatory cytokine signalling and lowering hepcidin, which can improve myelofibrosis-related anaemia.

Prescribing in practice

  • Serious infections, including reactivation of viral hepatitis and other opportunistic infections, can occur, so infection status is checked and patients are monitored, with treatment avoided during active serious infection.
  • It can cause thrombocytopenia and other cytopenias requiring dose adjustment, and peripheral neuropathy should be assessed.
  • As a JAK inhibitor it carries class warnings, and screening for tuberculosis and viral hepatitis before starting is advised.

Monitoring

Monitor full blood count, liver function and for signs of infection and neuropathy before and during treatment.

Counselling the patient

  • Report fever, persistent cough or other signs of infection promptly.
  • Tell your team about new numbness or tingling in the hands or feet.
  • Do not stop or change the dose without advice, and attend regular blood tests.

Evidence & guidelines

The MOMENTUM and SIMPLIFY trials supported benefit in myelofibrosis with anaemia; use follows licensed and specialist guidance.

Reference: NICE TA957; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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