- Current enrollment in any interventional clinical study in which an investigational drug or approved therapy for investigational use is administered within 30 days prior to the Baseline Visit OR prior participation in any of the following Biogen studies: 998HA101 (NCT01027377), 997HA301 (NCT01181128), 8HA02PED (NCT01458106), 997HA307 (NCT02083965), and 8HA01EXT (NCT01454739).