Baseline demographics and clinical characteristics
| Characteristic | Overall population (n=6148) | ≥8-year treatment cohort (n=491) | <8-year treatment cohort (n=1056) |
| Age at baseline, mean (SD), years | 37.1 (9.8) | 35.9 (9.2) | 38.7 (9.8) |
| Female, n (%) | 4430 (72.1) | 366 (74.5) | 755 (71.5) |
| Relapses in year prior to natalizumab initiation | |||
| Mean (SD) | 2.0 (1.0) | 2.0 (1.1) | 2.0 (1.1) |
| n (%) | |||
| ≤1 | 2094 (34.1) | 164 (33.4) | 395 (37.4) |
| >1 | 4054 (65.9) | 327 (66.6) | 661 (62.6) |
| Baseline EDSS score | |||
| Mean (SD) | 3.5 (1.6) | 3.3 (1.5) | 3.8 (1.8) |
| ≤3.0, n (%) | 2843 (46.2) | 240 (48.9) | 423 (40.1) |
| >3.0, n (%) | 3245 (52.8) | 250 (50.9) | 625 (59.2) |
| Unknown, n (%) | 60 (1.0) | 1 (0.2) | 8 (0.8) |
| Disease duration at baseline, median (range), years | 7.8 (0 to 48) | 7.6 (0 to 39) | 8.8 (0 to 48) |
| Treatment duration prior to natalizumab initiation, years | |||
| Mean (SD) | 4.0 (3.9) | 3.8 (3.5) | 3.8 (3.5) |
| Median (range) | 2.9 (0 to 22) | 2.7 (0 to 16) | 2.8 (0 to 17) |
| Prior DMTs, n (%) | |||
| 0 | 952 (15.5) | 65 (13.2) | 152 (14.4) |
| 1 | 2897 (47.1) | 241 (49.1) | 514 (48.7) |
| ≥2 | 2299 (37.4) | 185 (37.7) | 390 (36.9) |
| Prior MS DMT used, n (%)* | |||
| Interferon beta-1a formulations | 4494 (73.1) | 378 (77.0) | 811 (76.8) |
| Glatiramer acetate | 2034 (33.1) | 154 (31.4) | 322 (30.5) |
| Fingolimod | 233 (3.8) | 1 (0.2) | 3 (0.3) |
| Dimethyl fumarate | 44 (0.7) | 0 (0) | 2 (0.2) |
| Teriflunomide | 25 (0.4) | 1 (0.2) | 1 (0.1) |
| Alemtuzumab | 2 (<0.1) | 1 (0.2) | 0 (0) |
| Prior immunosuppressant use, n (%) | 983 (16.0) | 82 (16.7) | 175 (16.6) |
| Natalizumab doses prior to enrolment, mean (SD) | 1.1 (1.1) | 1.2 (1.2) | 1.2 (1.2) |
| Patients who were anti-JCV antibody positive, n (%) | 2102 (34.2)† | 170 (34.6)† | 293 (27.7)† |
| Patients who were anti-JCV antibody negative, n (%) | 2230 (36.3)† | 294 (59.9)† | 146 (13.8)† |
*Patients may have used >1 DMT.
†Anti-JCV antibody status at enrolment was tested in 4339 patients in the overall population, 469 patients in the ≥8-year treatment cohort and 440 patients in the <8-year treatment cohort.
DMT, disease-modifying therapy; EDSS, Expanded Disability Status Scale; JCV, JC virus; MS, multiple sclerosis.