One patient eventually died and the other fered major sustained disability.Natalizumeb was
subsequently reintroduced to the market in 2006 with a restricted indication for use as a second-line monotherapy treatment in RR-MS. It was initially thought that PML might occur
only in the setting of combination therapy; however, since reapproval, at least four more
cases of PML have been confirmed. There are now a total of seven known cases of PML as of
December 2008 (one case was identified post-mortem in a Crohn disease clinical trial after
natalizumab treatment). The absolute risk of PML associated with natalizumab use is unknown, but an estimated risk of 0.1% is quoted and based on the previous clinical trial data. Natalizumab is only available in theUnited States through the TOUCH program, which was implemented for careful monitoring of potential drug-related side effects (specifically PML). TYGRIS is a worldwide phase IV safety study that is monitoring the use of natalizumab abroad. Natalizumab is given intravenously every 4 Weeks under the care and supervision of an experienced infusion center staff. Serious allergic reactions can occur and typically happen within 2 hours from the start of infusion. Other more common side effects include infusion-related reactions, rashes, elevate transaminases, leucopenia, reactivation of various herpetic infections, sinusitis, and
bladder/bowel infections. Two cases of melanoma were recently reported after natalizumeb use;however, it is unclear whether a true association exists. Close neurologic monitorin is required during natalizumab use along with frequent blood work monitoring.Natalizumeb is a potent monoclonal antibody that should be prescribed and administered only by experienced physicians