What Is the Risk of Progressive Multifocal Leukoencephalopathy in Patients With Ulcerative Colitis or Crohn's Disease Treated With Vedolizumab?

Background: Progressive multifocal leukoencephalopathy is a serious condition linked to certain diseases and immunosuppressant therapies, including the α4 integrin antagonist natalizumab. No cases have been reported to date with vedolizumab, a selective antagonist of the α4β7 integrin expressed on gut-homing lymphocytes. This analysis aimed to describe the current and future expected occurrence of progressive multifocal leukoencephalopathy with vedolizumab use, were the risk the same as in other populations in which this disease has been studied. Methods: The expected number of vedolizumab-associated progressive multifocal leukoencephalopathy cases was estimated up to May 19, 2016, and modeled up to 2034. These estimates were based on the cumulative exposure to the drug, assuming an equivalent risk to that of patients treated with natalizumab or those from other reference populations where progressive multifocal leukoencephalopathy has been examined. Future cases were modeled based on similar risks and projected sales. Results: The cumulative vedolizumab exposure was estimated at 54,619 patient-years, with a 95% confidence interval of 0.0 to 6.75 cases per 100,000 patient-years. An estimated 30.2 (95% confidence interval, 19.4-40.9) cases of progressive multifocal leukoencephalopathy would have occurred if vedolizumab had the same risk as that of natalizumab. There would be a 50% chance of the first case occurring by 2018, assuming an equivalent risk to the general population. Conclusions: These analyses indicate that the risk of progressive multifocal leukoencephalopathy with vedolizumab is small, and unlikely to be above 6.75 cases per 100,000 patient-years.