Introduction: In patients with Multiple Sclerosis (pwMS) disease- modifying therapies (DMTs) are known to affect immune response to antigens and possibly to SARS-CoV2 vaccine. Therefore, post-vaccination serological assessments are needed to evaluate the effect of the vaccine on SARS-CoV-2 antibody response. Objectives and aims: We designed a prospective multicenter cohort study enrolling pwMS who were scheduled for SARSCov- 2 vaccination with mRNA vaccines (BNT162b2, Pfizer/ BioNTech, Inc or mRNA-1273, Moderna Tx, Inc) to evaluate their effect on SARS-CoV-2 antibody response. Methods: A blood collection for the measure of SARS-CoV-2 antibody before the first vaccine dose and 4 weeks after the second dose was planned, with a centralized and blinded serological assessment (electrochemiluminescence immunoassay, ECLIA, Roche Diagnostics). Results: Preliminary data were collected on 780 pwMS (76% BNT162b2 and 24% mRNA-1273) who had pre- and 4-week post-vaccination blood assessments. 87 (11.2%) were untreated, 154 (19.7%) on ocrelizumab, 25 (3.2%) on rituximab, 85 (10.9%) on fingolimod, 25 (3.2%) on cladribine and 404 (51.7%) on other DMTs. 677 patients (86.8%) had detectable post-vaccination SARS-CoV-2 antibodies. At multivariate analysis, the antibody levels of patients on ocrelizumab (178-fold decrease, p<0.001), fingolimod (26-fold decrease, p<0.001) and rituximab (17-fold decrease, p<0.001) were significantly reduced as compared to untreated patients. Vaccination with mRNA-1273 resulted in a systematically 3.5-fold higher antibody level than with the BNT162b2 vaccine (p<0.001). Interpretation: In pwMS, anti-CD20 treatment and fingolimod led to a reduced humoral response to mRNA-based SARS-CoV-2 vaccines. As mRNA-1273 elicits 3.5-higher antibody levels than BNT162b2, this vaccine may be preferentially considered for patients under anti-CD20 treatment or fingolimod. Combining our data with those that will be produced by studying the cellular immune response to vaccines, and including clinical follow-up, will contribute to better define the most appropriate SARS-CoV-2 vaccine strategies in the context of DMTs and MS. At the time of the ECTRIMS presentation data on the full sample (about 2000 subjects) will be presented.

Background: As the COVID-19 pandemic continues, evidencebased clinical guidance for managing the care of people with multiple sclerosis (MS) is an ongoing concern. In recent months, data from cohorts of people with MS has indicated that certain demographic and clinical characteristics, including use of some disease- modifying therapies (DMTs), leads to worse outcomes from SARS-CoV-2 infection. The COVID-19 in MS global data sharing initiative, which now includes over 4,500 confirmed COVID- 19 cases in people with MS, gives the opportunity to corroborate previous findings with greater certainty. Methods: Clinician-reported data from 32 countries were aggregated into a dataset of 5,543 patients who had suspected or confirmed COVID-19. Demographic and clinical covariates were queried, alongside COVID-19 clinical severity outcomes. These outcomes (hospitalisation, admission to ICU, requiring artificial ventilation, and death) were assessed in patients with suspected/ confirmed COVID-19 using multilevel mixed-effects logistic regression. All models were corrected for age, sex, EDSS, and MS type. DMTs were individually compared to glatiramer acetate (GA), as well as to pooled other DMTs and natalizumab. Results: Of 5,543 patients in the clinician-reported dataset, 909 with suspected and 4,634 with confirmed COVID-19 were included in the analysis. Previous demographic findings were confirmed: male sex, older age, progressive MS, and higher disability were associated with worse outcomes from SARS-CoV-2 infection. Use of anti-CD20 DMTs (ocrelizumab and rituximab) was associated with worse COVID-19 outcomes. Compared to GA, ocrelizumab and rituximab were associated with increased risk of hospitalisation (aOR=1.61(95%CI=1.06-2.43);aOR=2.42(95%CI=1.54-3.81) and ICU admission (aOR=3.13(95%CI=1.22-8.00);aOR=4.46 (95%CI=1.64-12.09)). Rituximab was associated with increased risk of artificial ventilation (aOR=3.57(95%CI=1.38-9.20));ocrelizumab showed a positive trend (aOR=1.86(95%CI=0.76-4.55). Rituximab showed a positive trend with increased risk of death (aOR=2.74(95%CI=0.68-11.09). Associations persisted on restriction to confirmed COVID-19 cases. Conclusions: Analysing the largest international real world dataset of people with MS who have suspected or confirmed COVID- 19 confirms previous findings that male sex, older age, progressive MS, higher disability, the use of anti-CD20 medication (ocrelizumab and rituximab) are associated with worse COVID-19 outcomes.

Importance: Natalizumab discontinuation induces the recurrence of Multiple Sclerosis (MS) disease activity: Currently no therapeutic approach has been found able to abolish disease reactivation. Objective: To collect data from patients with MS switching from natalizumab to cyclophosphamide. Design: Retrospective multicentre study. Setting: Nine Multiple Sclerosis Centers in Italy. Participants: A total of 47 patients with clinically definite RR-MS switched to cyclophosphamide after natalizumab discontinuation. Two patients were excluded from the analysis because received less than 12 natalizumab infusions. The remaining 45 patients were subdivided into two main groups: Early Treatment (period of washout between natalizumab and cyclophosphamide 1 to 3 months), Late Treatment (washout between natalizumab and cyclophosphamide higher than 3 months). Intervention: Cyclophosphamide intravenous pulses after natalizumab discontinuation. Main outcome measure: Number of relapses, Expanded Disability Status Scale scores, number of new T2/fluidattenuated inversion recovery lesions and contrast-enhancing lesions on brain magnetic resonance imaging, rebound effect, adverse events. Results: In the Early Treatment group, only 3/23 patients (13%) experienced a clinical relapse and only 2 out of 13 (15%) patients showed brain Magnetic Resonance Imaging (MRI) activity at 3 months, while none developed MRI activity at 6 months after cyclophosphamide introduction. In the Late Treatment Group 12/22 patients (63%) had relapses during the washout period and 4/22 (40%) after the introduction of cyclophosphamide; MRI disease activity was shown in 5/9 (56%) at 3 months and in 5/14 (36%) at 6 months after cyclophosphamide introduction. Conclusions and relevance: These data show that cyclophosphamide could be able to reduce disease reactivation after natalizumab, in particular with a short washout period after natalizumab discontinuation. It can be suggested that a short period (3-6 months) of cyclophosphamide monthly pulses could be used as “re-induction” treatment in patients discontinuing natalizumab.

4-Aminopyridine (4-AP) has been recently introduced as a symptomatic treatment of walking impairment in MS patients. The clinical benefits have been reported in about 1/3 of patients. The study was intended to verify in patients treated with 4-AP: – the ability of motor-evoked potentials (MEPs) in identifying patients responding to treatment; – if there are MEP parameters changes related to clinical improvement. Patients were enrolled in a prospective study. Patients underwent neurological examination, in order to determine: EDSS, T25WF (a walking test, measuring speed). MEPs have been recorded at lower limb, central motor conduction time (CMTT) and CMAP/MEPs ratio have been evaluated before starting and after 30 days of 4-AP treatment. We enrolled 14 patients. Patients with high EDSS score (>4) and bilateral CMTT alteration were most likely responding to therapy. MEP parameters changes observed in some patients were not related to clinical effect measured with T25WF. The response to 4-AP occurs only in 35% of MS patients. Given the drug’s side effects and its high cost, it would be useful to have predictor of response to treatment. Joining together EDSS score and CMTT value we could identify a great number of patients responding to therapy (nearly 85%).