Subcutaneous Natalizumab on the PBS

The subcutaneous form of natalizumab is now available on the Pharmaceutical Benefits Scheme (PBS) for the treatment of relapsing-remitting multiple sclerosis. Natalizumab is a monoclonal antibody that binds to α4 integrins on leucocytes. This inhibits their migration into the central nervous system, which is thought to reduce central inflammation and demyelination. Previously only available as an intravenous infusion, the introduction of a subcutaneous form has potential advantages for some patients.

The usual natalizumab dose is 300mg every four weeks. The vials for intravenous use contain 300mg and should be diluted in 100 mL of 0.9% sodium chloride and infused over one hour. The pre-filled syringes for subcutaneous use contain 150mg each and are administered as two consecutive injections (given not more than 30 minutes apart). While the subcutaneous form still requires administration by a healthcare professional, it may be given in a wider range of clinical settings. This may be particularly convenient for patients who live remotely.

The DELIVER study compared the pharmacokinetics and pharmacodynamics of natalizumab administered by different routes. Following two weeks of continuous dosing, the serum concentration and trough serum concentration were similar in patients receiving natalizumab via the intravenous or subcutaneous route. All pharmacodynamic parameters appeared similar in each group.

Natalizumab is generally well tolerated. Common adverse events include headache, fatigue, and mild infections (e.g. respiratory and urinary tract infections). Natalizumab is associated with an increased risk of progressive multifocal leukoencephalopathy (PML), a viral infection of the brain that can cause death or severe disability. Patients should be closely monitored for early signs and symptoms of PML during treatment and for around six months after stopping.