The active ingredient of Tysabri® is natalizumab. Natalizumab is a synthetic antibody which locks onto certain immune cells, called T-cells. Once the natalizumab is attached to the T- Cells, they cannot cross the blood brain barrier to attack the myelin or nerves in the brain and spinal cord where inflammation and damage is caused in MS.

How is Tysabri administered?

Tysabri® is administered by IV infusion once every twenty eight days. Tysabri® is available for funding if the PHARMAC criteria are fulfilled. There are a number of criteria you are required to meet before your neurologist obtains authority to write this prescription.

Tysabri is given as an infusion at a special clinic. Usually this clinic will be attached to a hospital. A nurse or other qualified health professional will monitor you before, during and after your infusion.

Benefits shown in clinical trials

Clinical trials found that Tysabri® (natalizumab) has a significant beneficial effect in people with relapsing-remitting multiple sclerosis by reducing the accumulation of permanent physical disability, exacerbation frequency and disease activity measured by gadolinium-enhanced lesions on brain magnetic resonance images (MRI).

Side Effects?

Most people taking Tysabri tolerate it well, but there can be side effects – including a very rare, but potentially fatal infection called PML (progressive multifocal leukoencephalopathy)

Common side effects include:

  • joint pain, fever, tiredness, a runny or blocked nose, sore throat, feeling or being sick, headache or dizziness.
  • During the infusion of Tysabri, and up to an hour afterwards, some people shiver, or feel sick or dizzy.
  • Around one in 25 people who take Tysabri may have an allergic reaction to taking it, either during the infusion or in the hour following.
  • In addition, some people might have skin reactions to the infusion.

PML (progressive multifocal leukoencephalopathy) caused by a viral infection in the brain. It can cause severe neurological symptoms, which may at first be mistaken for MS relapses. Meticulous monitoring for this rare (Progressive Multifocal Leukoencephalopathy, PML, caused by the JC virus) is a requirement mandated by PHARMAC

Monitoring also includes specialised blood tests and regular MRI scans. All nurses are trained in administration of the drug and infusions occur under the supervision of a Neurologist or in regional centres by a Physician experienced in neurological conditions.

Neurologists prescribing Tysabri must ensure that everyone –  professionals and patients – is aware of the risks, the early signs of PML to look out for and what to do if they notice these signs.


For details of the criteria you need must meet to get funded access to Tysabri® see P24-26 of the Pharmaceutical Schedule for Entry and Stopping Criteria

Special Authority must be approved by the Multiple Sclerosis Treatment Assessment Committee (MSTAC) before funding is approved. Applications will be considered by MSTAC at its regular meetings and approved subject to eligibility according to the Entry and Stopping criteria.

Application details may be obtained from PHARMAC’s website or:

The coordinator Phone: 04 460 4990

Multiple Sclerosis Treatment Assessment Committee Facsimile: 04 916 7571

PHARMAC, PO Box 10 254, Wellington


Application forms must be completed by a Neurologist or Specialist General Physician and sent to the coordinator for MSTAC and will be considered by MSTAC at the next practicable opportunity.

Notification of MSTAC’s decision will be sent to the patient, the applying clinician and the patient’s GP (if specified).

Recent Studies

Efficacy and safety of Natalizumab in multiple sclerosis: interim observational programme results - H Butzkueven et al. -  14 Feb 2014 - JNNP Online



Current Research into Tysabri/Natalizumab


Efficacy and Safety of Natlizumab in MS: Interim observational programme results - 14 Feb 2014- H Butzkueven at al. - JNNP Online


Clinical trials established the efficacy and safety of natalizumab. Data are needed over longer periods of time and in the clinical practice setting.


To evaluate long-term safety of natalizumaband its impact on annualised relapse rate and Expanded Disability Status Scale (EDSS) progression in patients with relapsing-remitting multiple sclerosis (RRMS).


The Tysabri (natalizumab) Observational Program (TOP) is an open-label, multinational, 10-year prospective study in clinical practice settings.


In this 5-year interim analysis, 4821 patients were enrolled. Follow-up for at least 4 years from natalizumab commencement in 468 patients and at least 2 years in 2496 patients revealed no new safety signals. There were 18 cases of progressive multifocal leucoencephalopathy reported, following 11–44 natalizumab infusions. Mean annualised relapse rate decreased from 1.99 in the 12 months prior to baseline to 0.31 on natalizumab therapy (p<0.0001), remaining low at 5 years. Lower annualised relapse rates were observed in patients who used natalizumab as fi rst MS therapy, in patients with lower baseline EDSS scores, and in patients with lower prenatalizumab relapse rates. Mean EDSS scores remained unchanged up to 5 years.


Interim TOP data con firm natalizumab’soverall safety profile and the low relapse rate and stabilised disability levels in natalizumab-treated patients with RRMS in clinical practice.

Read more


MiR-126: a novel route for natalizumab action?

Mult Scler. 2014 Mar 5. [Epub ahead of print]

This study shows the potential role of a particular type of protein (miR-126), which control gene expression and are involved in immunity. This particular protein was found to be down-regulated in patients treated with natalizumab, while the protein was up-regulated during relapse. This provides us with a better understanding of how natalizumab works on MS activity as well as helping us understand specific side-effects associated with the drug.

Read more


Neurofilament light antibodies in serum reflect response to natalizumab treatment in MS

Mult Scler. 2014 Feb 10. [Epub ahead of print]
This study group looked at certain components/proteins of neurons, and the role of antibodies against these proteins (neurofilament light protein (NF-L)), as biomarkers for monitoring response to treatment (with natalizumab/tysabri) and their correlation with the different types of MS. Overall, the results support the potential use of serum autoantibodies to these proteins (NF-L) as a good indicator of disease activity in MS. There was also an association between treatment with natalizumab/tysabri and lowered levels of these proteins (NF-L) in the blood.
Read more

Reduced sick leave in multiple sclerosis after one year of natalizumab treatment

Mult Scler. 2013 Dec 30. [Epub ahead of print]
Natalizumab is used for the treatment of relapsing remitting MS and it acts by inhibiting lymphocyte migration across the blood-brain-barrier. This study group looked at the amount of sick leave in subjects with relapsing remitting MS (RRMS) before and one year after treatment with natalizumab (Tysabri). They found that the initiation of natalizumab treatment in RRMS may be associated with improved ability to work. Both younger age and improvement of walking ability correlated with decreased sick leave.

Read more

 JC virus reactivation during prolonged natalizumab monotherapy for MS

Ann Neurol. 2014 Mar 31. doi: 10.1002/ana.24148. [Epub ahead of print]
This study looks at getting a better understanding of the virus which causes PML (Progressive Multifocal Leucoencephalopathy) in patients treated with natalizumab (tysabri).
The study shows that after more than 18 months of treatment with natalizumab, a high viral load was found in specific T cells (CD34+) and monocytes. The virus may reactivate in the cerebrospinal fluid without new clinical or MRI findings in patients.
This helps to improve our understanding of the virus and further research is needed to improve PML risk stratification.
Read more