Intravenous Thrombopoietin Receptor Agonists (TPO-RAs)
Thrombopoietin Receptor Agonists (TPO RAs) are medicines that help the bone marrow make more platelets. They are commonly used when ITP continues or returns after first line treatments such as corticosteroids or IVIg. TPO RAs are one of the most effective long term treatment options for persistent or chronic ITP.
Medications included
Eltrombopag (Revolade)
Romiplostim (Nplate) (not currently available in New Zealand)
Avatrombopag (Doptelet) (not currently available in New Zealand)
When TPO-RAs are used
TPO-RAs are usually used as second line treatments, including when:
- Steroids or IVIg haven’t worked well enough
- Platelet counts remain low for several months
- A longer term treatment is needed
- Splenectomy is not preferred or not suitable
- A person wants to avoid immunosuppressive medicines
- A stable, predictable platelet count is needed for work, lifestyle or medical procedures
TPO-RAs may be used alone or combined with other treatments in more complex cases.
How they work
TPO RAs work by:
- Stimulating the bone marrow to produce more platelets
- Increasing the number of young platelets, which are often more effective
- Helping the body outpace immune related platelet destruction
They do not suppress the immune system. Instead, they boost platelet production to maintain a safe level.
What to expect
- Eltrombopag is taken as a tablet once daily
- Romiplostim is given as a weekly injection
- Avatrombopag is taken as a tablet
- Platelet counts often improve within 1–3 weeks
- Doses are adjusted based on platelet response
- Regular blood tests are needed, especially at the start
- Treatment may be long term, depending on response
- Some people can eventually taper and stop TPO RAs
Your doctor will work with you to find the lowest dose that keeps your platelet count in a safe range.
Side effects
Most people tolerate TPO RAs well.
Common effects
Common effects include:
- Headache
- Nausea
- Fatigue
- Mild liver test changes (especially with eltrombopag)
Less common effects
Less common effects include:
- Increased risk of blood clots (rare)
- Bone marrow changes (reversible and monitored)
Your doctor will monitor your platelet count and liver function regularly.
Adults, Children and in Pregnancy
Adults
- TPO RAs are widely used in adults with persistent or chronic ITP
- They are often preferred when long term stability is needed
- Some adults may switch between TPO RAs if one is not effective
Children
- TPO RAs are used in children with ongoing ITP or significant bleeding
- Romiplostim and Eltrombopag are commonly used in paediatrics
- Avatrombopag may be used depending on age and formulation availability
Pregnancy
- TPO RAs are not routinely used during pregnancy
- They may be considered in selected cases under specialist care
- IVIg and steroids remain the preferred options
Other Considerations
These points help patients understand the practical aspects of TPO RA treatment:
- Eltrombopag must be taken on an empty stomach (2-4 hours away from dairy, calcium, iron or supplements)
- Romiplostim requires weekly injections, usually at a clinic, but over time can be self-administered with the right training.
- Switching between TPO RAs is common and often effective
- TPO RAs do not cure ITP, but they can maintain safe platelet levels
- Around 10–30% of people may eventually stop TPO RAs and maintain a good platelet count
- TPO RAs are not immunosuppressive, so they do not increase infection risk
- Nplate and Avatrombopag are not currently available in New Zealand.