These levels are “enormous,” he said, higher even than those in the HIV population before the rise of antiretroviral medications.
Overall, as of Nov. 30, 2017, 177,800 patients have received natalizumab in the postmarketing setting, and 756 cases of PML have been reported as of Dec. 7, 2017. All but three of those cases were in patients with MS, and the overall incidence was 4.19/1,000.
Dr. Berger recommends regular screening MRIs for PML in patients taking natalizumab, and he advised physicians to be on alert for signs of trouble like the appearance of new neurologic symptoms or a new or increasing JC virus antibody index.
Two other MS drugs, fingolimod (Gilenya) and dimethyl fumarate (Tecfidera), fall into the category of low risk, with just 19 and 5 reported cases, respectively, as of February 2018, Dr. Berger said. He added that two of the fingolimod patients had earlier exposure to natalizumab.