Long-lasting severe anemia following treatment with natalizumab for relapsing-remitting multiple sclerosis: a case report.

BACKGROUND: Natalizumab is a monoclonal antibody used to treat patients with relapsing-remitting multiple sclerosis. Anemia is a recognized side effect, but it is usually mild and of a short duration when natalizumab is stopped. Here, we describe a case of a young woman with severe and especially long lasting anemia associated with treatment with natalizumab, persisting up to a year after treatment was stopped. CASE PRESENTATION: A 24 year-old Caucasian woman with relapsing-remitting multiple sclerosis developed severe transfusion dependent anemia after 27 infusions with natalizumab, which was her first and only treatment for her multiple sclerosis. Extensive hematologic diagnostics did not reveal any malignant cause or any other plausible non-malignant cause for her anemia. The bone marrow was found to be hypercellular, with a maturation arrest of the erythropoiesis and with grade 1-2 fibrosis. No specific treatment for the anemia was given. The hemoglobin level showed signs of spontaneous increase after nearly one year after natalizumab was discontinued. CONCLUSION: Severe anemia can be caused by treatment with natalizumab. This case adds information to the few other similar reported cases, demonstrating the potential duration of the anemia, as well as detailed description of hematologic findings. The mechanism is most likely due to inhibition of α4 subunit of the α4ß1-integrin, which is present on both lymphocytes and erythroid precursor cells.

Switching from natalizumab to an anti-CD20 monoclonal antibody in relapsing remitting multiple sclerosis: A systematic review.

BACKGROUND: Use of natalizumab (NTZ) is precluded in many Multiple Sclerosis (MS) patients by the risk of progressive multifocal leukoencephalopathy (PML). Regardless, some patients may commence natalizumab for short term disease control in spite of being seropositive, and others may seroconvert whilst on treatment. In these circumstances, discontinuation of NTZ should not occur until a clear exit strategy is established to prevent post-NTZ disease reactivation, which often exceeds the severity of disease activity prior to NTZ treatment. The objective of this systematic review was to summarise the available evidence for CD20-monoclonal antibodies (CD20mAb) as a suitable NTZ exit strategy, and to identify whether a superior switch protocol can be established. METHODS: In accordance with PRISMA guidelines, a total of 2393 references were extracted from a search of three online databases (PubMed, Scopus, MEDLINE). Following the application of inclusion/exclusion criteria, a total of 5 studies representing 331 patients were included. RESULTS: The overall incidence of clinical relapse during washout periods ranging from 4.4-10.7 weeks was 0 %. The incidence of clinical relapse during two-year follow-up ranged from 1.8 % to 10 % for switches to all types of CD20 monoclonal antibody. The weighted mean for clinical relapse at 12 months was 8.8 %. Three studies reported an annualised relapse rate (ARR) ranging from 0.02-0.12 with a weighted mean ARR of 0.07. The overall incidence of PML during washout was 0 % and the overall incidence of PML within 6 months follow-up was 0.6 %. CONCLUSIONS: This systematic review provides the first attempt at identifying a superior switch protocol in patients at risk of PML transitioning from NTZ to a CD20mAb. Our results indicate that CD20mAb's are a suitable transitional option for patients who discontinue NTZ, with our cohort demonstrating very low rates of carryover PML and low rates of clinical relapse. The most appropriate washout period is unclear due to confounding factors but is likely between 4 and 12 weeks.

Efficacy and safety of ocrelizumab in patients with relapsing multiple sclerosis: Real-world experience of two Swiss multiple sclerosis centers.

BACKGROUND: Ocrelizumab (OCR) is a humanized monoclonal antibody directed against CD-20 positive lymphocytes, mainly B-lymphocytes. OCR is approved for treatment of primary progressive (PPMS) and relapsing multiple sclerosis (RMS). This study aims to provide real-world safety and efficacy data of people with RMS treated with OCR in two Swiss Multiple Sclerosis (MS) centers. METHODS: We have conducted a retrospective data analysis using the patient cohorts from the Cantonal Hospital Aarau and Bern University Hospital (RMS: n = 235). Statistical analyses were performed with Mann-Whitney U-Test, Chi-squared test and Spearman-Rho-Correlation. Adjustment for multiple testing was performed by Bonferroni procedure. RESULTS: After initiation of OCR, there was a decrease in disease activity in RMS patients. In our study, 152/190 (80.0 %) RMS patients fulfilled the criteria for NEDA-3 12 months and 88/104 (84.6 %) showed NEDA-3 24 months after OCR initiation. The most frequent adverse events (AEs) in our study were infections, taking place in 78/235 (33.2 %) RMS patients. COVID-19 was the most common infection, followed by urinary infections and other respiratory infections and infectious adverse events occurred significantly more frequent in patients with reduced IgG serum concentration. CONCLUSIONS: Our real-world study showed OCR being associated with low rates of any type of MS disease activity as indicated by NEDA-3. The adverse event profile is comparable to the known events especially infections and an association between infections and reduced IgG serum concentration was found.

Evidence of disease activity during pregnancy and post-partum in MS patients treated with high-efficacy therapies.

BACKGROUND: Multiple sclerosis (MS) predominantly affects women of childbearing age. Due to the risk of teratogenicity, women with active multiple sclerosis (MS) who require high-efficacy therapies (HET) may need to discontinue treatment during pregnancy. Fingolimod and Natalizumab withdrawal increases the risk of disease reactivation, a risk not commonly associated with anti-CD20 therapies. However, comparative data are limited during pregnancy and post-partum. Our aim was to compare evidence of disease activity during pregnancy and post-partum in women treated with HET (anti-CD20 therapies, Natalizumab or Fingolimod) before conception, whether or not exposed during pregnancy. METHODS: In this single-center retrospective study, we included consecutive pregnancies of relapsing-remitting MS patients and classified them in three groups according to the last HET used before conception: « anti-CD20 ¼ « Natalizumab (NTZ) ¼ and « Fingolimod (FGD) ¼. The main outcome was annualized relapse rate (ARR) during pregnancy and post-partum. RESULTS: We included 66 pregnancies: 21, 24 and 21 in anti-CD20, NTZ and FGD groups respectively. Overall, mean ARR (SD) increased from 0.36 (0.6) during the preconception year to 0.60 (1.3) during pregnancy and to 1.03 (2.0) in the first 3 months post-partum. Mean ARR in anti-CD20 group (0.09 (0.3)) during pregnancy and the first 3 months post-partum was lower compared with NTZ (0.48 (0.6); p = 0,09) and FGD (1.50 (1.8); p = 0.001) groups. Proportion of pregnancies with radiological activity during pregnancy and post-partum in anti-CD20 group (5.2 %) was lower compared with NTZ (63.1 %; p < 0.001) and FGD (72.2 %; p < 0.001) groups. There was no significant difference in the evolution of EDSS score from conception to post-partum between each group (p = 0.75). CONCLUSION: Evidence of disease activity was significantly lower in patients exposed to anti-CD20 therapies before conception. This study suggests that use of anti-CD20 therapies is an efficient option to prevent disease reactivation during pregnancy and post-partum.

Safety and efficacy of extended versus standard interval dosing of natalizumab in multiple sclerosis patients: a systematic review and meta-analysis.

BACKGROUND: Multiple sclerosis (MS) is a chronic inflammatory, immune-mediated disease affecting the central nervous system. Natalizumab, an FDA-approved monoclonal antibody for MS, has been explored for its off-label extended interval dosing (EID), suggesting a potential reduction in the risk of progressive multifocal leukoencephalopathy (PML) compared to standard interval dosing (SID). Our objective was to assess the efficacy and safety of EID in comparison to SID for natalizumab treatment in patients with MS. METHODS: We searched PubMed, Embase, WOS, Scopus, Ovid, Science Direct, Clinical trials.gov, and Cochrane Library. Our assessed outcomes were clinical relapses, MRI activity, change in expanded disability status scale [EDSS], and the risk of PML. The EID group was defined as 5 to 8 weeks [EID (Q5-8W)]. The analysis was conducted using RevMan ver. 5.4. The effect estimates were presented as a risk ratio [RR] or mean difference with 95% confidence intervals [CI] using SID group as the reference for comparisons. RESULTS: Fourteen studies met our inclusion criteria: 2 RCTs, 1 switched single-arm trial, and 12 observational studies. No significant differences were found in all efficacy outcomes of interest. Risk of clinical relapses [RR = 0.90, (95%CI 0.80, 1.02)], risk of new or newly enlarging T2 hyperintense MRI lesions [RR = 0.78, (95%CI 0.59, 1.04)], risk gadolinium enhancing lesions [RR = 1.30, (95%CI 0.98, 1.72)], change in EDSS [MD = 0.09 (95%CI - 0.57, 0.76)], risk of PML [RR = 1.09, 95%CI (0.24, 4.94)]. CONCLUSION: In summary, our meta-analysis indicates that natalizumab maintains its effectiveness under extended interval dosing [up to 8 weeks], presenting comparable risks for clinical relapses, MRI lesions, EDSS, and PML. Caution is advised given study limitations and heterogeneity. Robust conclusions necessitate well-designed high-quality prospective studies.

Drug-Induced Progressive Multifocal Leukoencephalopathy (PML): A Systematic Review and Meta-Analysis.

INTRODUCTION: Progressive multifocal leukoencephalopathy (PML) was first described among patients affected by hematological or solid tumors. Following the human immunodeficiency virus (HIV) epidemic, people living with HIV have represented most cases for more than a decade. With the diffusion of highly active antiretroviral therapy, this group progressively decreased in favor of patients undergoing treatment with targeted therapy/immunomodulators. In this systematic review and meta-analysis, the objective was to assess which drugs are most frequently related to PML development, and report the incidence of drug-induced PML through a meta-analytic approach. METHODS: The electronic databases MEDLINE, EMBASE, ClinicalTrials.gov, Web of Science and the Canadian Agency for Drugs and Technologies in Health Database (CADTH) were searched up to May 10, 2022. Articles that reported the risk of PML development after treatment with immunomodulatory drugs, including patients of both sexes under the age of 80 years, affected by any pathology except HIV, primary immunodeficiencies or malignancies, were included in the review. The incidence of drug-induced PML was calculated based on PML cases and total number of patients observed per 100 persons and the observation time. Random-effect metanalyses were conducted for each drug reporting pooled incidence with 95% confidence intervals (CI) and median (interquartile range [IQR]) of the observation time. Heterogeneity was measured by I2 statistics. Publication bias was examined through funnel plots and Egger's test. RESULTS: A total of 103 studies were included in the systematic review. In our analysis, we found no includible study reporting cases of PML during the course of treatment with ocrelizumab, vedolizumab, abrilumab, ontamalimab, teriflunomide, daclizumab, inebilizumab, basiliximab, tacrolimus, belimumab, infliximab, firategrast, disulone, azathioprine or danazole. Dalfampridine, glatiramer acetate, dimethyl fumarate and fingolimod show a relatively safe profile, although some cases of PML have been reported. The meta-analysis showed an incidence of PML cases among patients undergoing rituximab treatment for multiple sclerosis (MS) of 0.01 cases/100 persons (95% CI - 0.08 to 0.09; I2 = 20.4%; p = 0.25) for a median observation period of 23.5 months (IQR 22.1-42.1). Treatment of MS with natalizumab carried a PML risk of 0.33 cases/100 persons (95% CI 0.29-0.37; I2 = 50%; p = 0.003) for a median observation period of 44.1 months (IQR 28.4-60) and a mean number of doses of 36.3 (standard deviation [SD] ± 20.7). When comparing data about patients treated with standard interval dosing (SID) and extended interval dosing (EID), the latter appears to carry a smaller risk of PML, that is, 0.08 cases/100 persons (95% CI 0.0-0.15) for EID versus 0.3 cases/100 persons (95% CI 0.25-0.34) for SID. CONCLUSIONS: A higher risk of drug-related PML in patients whose immune system is not additionally depressed by means of neoplasms, HIV or concomitant medications is found in the neurological field. This risk is higher in MS treatment, and specifically during long-term natalizumab therapy. While this drug is still routinely prescribed in this field, considering the efficacy in reducing MS relapses, in other areas it could play a smaller role, and be gradually replaced by other safer and more recently approved agents.

Natalizumab extended interval dosing: what about wearing-off effect?

BACKGROUND: Up to two thirds of patients with multiple sclerosis (MS) under natalizumab report a resurgence of symptoms at the end of the natalizumab cycle (wearing-off (WO) effect). At the outbreak of COVID-19, in line with the international recommendations for MS management, our centre switched all clinically stable patients on natalizumab therapy for more than one year from standard interval dosing (SID) to extended interval dosing (EID) with every six weeks infusions. This study aimed to evaluate the impact of EID in WO in MS patients under natalizumab. METHODS: An observational retrospective study in patients with MS under natalizumab on EID was conducted. A questionnaire regarding current (on EID) and past (on SID) experience of WO effect was applied. RESULTS: Seventy-six patients were included. No significant differences were found in the annual relapse rate after the switch to EID (p = 0.083). However, there was a significant increase in the proportion of patients complaining of WO from 38.2% to 56.6% (p = 0.001). Moreover, patients with WO on SID, referred a significant increase in severity (p = 0.019) and duration of WO symptoms (p = 0.029), due to an anticipation of the symptoms relative to the day of natalizumab infusion (p = 0.019), when switching to EID. Symptoms improved with treatment maintenance in 23.3% of patients; instead, a reduction in interval dosing was needed in 54.8% with symptom improvement. CONCLUSION: WO affects a significant proportion of MS patients under natalizumab. Its prevalence, severity, and duration increase on EID, therefore despite clinical effectiveness maintenance of this posology should be individualized.

Rituximab treatment in pediatric-onset multiple sclerosis.

BACKGROUND AND PURPOSE: Rituximab (RTX) is frequently used off-label in multiple sclerosis. However, studies on the risk-benefit profile of RTX in pediatric-onset multiple sclerosis are scarce. METHODS: In this multicenter retrospective cohort study, patients with pediatric-onset multiple sclerosis from Sweden, Austria and Germany, who received RTX treatment were identified by chart review. Annualized relapse rates, Expanded Disability Status Scale scores and magnetic resonance imaging parameters (new T2 lesions and contrast-enhancing lesions) were assessed before and during RTX treatment. The proportion of patients who remained free from clinical and disease activity (NEDA-3) during RTX treatment was calculated. Side effects such as infusion-related reactions, infections and laboratory abnormalities were assessed. RESULTS: Sixty-one patients received RTX during a median (interquartile range) follow-up period of 20.9 (35.6) months. The annualized relapse rate decreased from 0.6 (95% confidence interval [CI] 0.38-0.92) to 0.03 (95% CI 0.02-0.14). The annual rate of new T2 lesions decreased from 1.25 (95% CI 0.70-2.48) to 0.08 (95% CI 0.03-0.25) and annual rates of new contrast-enhancing lesions decreased from 0.86 (95% CI 0.30-3.96) to 0. Overall, 70% of patients displayed no evidence of disease activity (NEDA-3). Adverse events were observed in 67% of patients. Six patients discontinued treatment due to ongoing disease activity or adverse events. CONCLUSION: Our study provides class IV evidence that RTX reduces clinical and radiological activity in pediatric-onset multiple sclerosis.

Efficacy and safety of rituximab in multiple sclerosis and neuromyelitis optica spectrum disorder.

In Thailand, resource limitations lead many multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) patients to use off-label immunosuppressants. This study assesses the efficacy and safety of rituximab (RTX) with a CD19-based reinfusion regimen among Thai MS and NMOSD patients. A retrospective review of patients at the Faculty of Medicine Siriraj Hospital from January 1994 to April 2023 was conducted. The primary outcome assessed was the change in annualized relapse rate (ARR) for patients using RTX for over a year. Secondary outcomes included changes in the Expanded Disability Status Scale (EDSS) scores, time to the first relapse after RTX initiation for patients using RTX for over a year, and an evaluation of the safety of RTX. The study encompassed 36 MS and 39 NMOSD patients. A majority of patients (91.7% of MS and 79.5% of NMOSD) experienced no relapses during a median follow-up of 30 months (Interquartile range [IQR] 20-46) and 31 months (IQR 23-41), respectively. The median ARR significantly decreased in both MS (from 0.77 [IQR 0.42-1.83] to 0 [IQR 0-0], p < 0.001) and NMOSD (from 0.92 [IQR 0.68-1.78] to 0 [IQR 0-0.17], p < 0.001) patients after switching to RTX, with no difference between those following a fixed 6-month time point regimen and a CD19-based reinfusion regimen. Median EDSS scores improved significantly at the last follow-up visit in both groups. The mean time to the first subsequent relapse was 8.3 ± 3.0 months in MS and 6.8 ± 1.7 months in NMOSD. Mild adverse drug reactions occurred in 44% of patients. RTX effectively prevents relapses in Thai MS and NMOSD patients, with no observed serious adverse drug reactions.

Control of disease activity with large extended-interval dosing of rituximab/ocrelizumab in highly active pediatric multiple sclerosis.

Recent studies in adults suggested that extended-interval dosing of rituximab/ocrelizumab (RTX/OCR) larger than 12 months was safe and could improve safety. This was an observational cohort study of very active pediatric-onset multiple sclerosis (PoMS) (median (range) age, 16 (12-17) years) treated with RTX/OCR with 6 month standard-interval dosing (n = 9) or early extended-interval dosing (n = 12, median (range) interval 18 months (12-25)). Within a median (range) follow-up of 31 (12-63) months after RTX/OCR onset, one patient (standard-interval) experienced relapse and no patient showed disability worsening or new T2-weighted lesions. This study suggests that the effectiveness of RTX/OCR is maintained with a median extended-interval dosing of 18 months in patients with very active PoMS.

Ocrelizumab in highly disabled progressive multiple sclerosis patients.

BACKGROUND: Ocrelizumab is a commonly used anti-CD20 monoclonal antibody with efficacy in the treatment of both relapsing-remitting (RRMS) and primary progressive (PPMS) multiple sclerosis. Real world use of ocrelizumab in MS patients with higher levels of motor disability requiring a walker or a wheelchair is not well characterized as these populations were excluded from initial studies. Higher levels of disability may be a barrier to treatment access. This study aimed to describe the access to, and tolerability and therapeutic outcomes of ocrelizumab in highly disabled MS patients in a real-world setting. METHODS: As part of an ongoing study of ocrelizumab treatment access, barriers, and outcomes in MS patients at the Brigham MS Center, we retrospectively reviewed all patients with an Expanded Disability Status Scale (EDSS) of 6.5 or greater at the time of ocrelizumab initiation. All patients were started on ocrelizumab by their treating providers prior to this study initiation. Patients were excluded for recent rituximab exposure, co-treatment with more than one immunosuppressant, or alternative diagnoses contributing to high EDSS. Data was collected on incidence and severity of side effects while on ocrelizumab, persistence of treatment beyond one year, and MS stabilization versus progression while on this treatment. RESULTS: Of the 1219 patients on ocrelizumab between 2017 and 2021, 113 (9.3 %) had EDSS of 6.5 or greater at the time of ocrelizumab initiation. Of the 113, 51 (45.1 %) were excluded: 6 (5.3 %) because they were duplicates or didn't receive ocrelizumab at our center, 25 (22.1 %) due to rituximab treatment in the previous year, 16 (14.2 %) due to lack of at least 1 year of follow up, and 4 (3.5 %) due to relevant comorbidities/treatment with other immunosuppressants. 62 patients were included in the final analysis. At ocrelizumab start, mean age was 62.1 +/- 8.7 years and median EDSS was 7.0 (range 6.5 to 9.5). Ocrelizumab was started in 26 of the included 62 patients (41.9 %) because of objective clinical disease worsening, in 17 (27.4 %) because of subjective worsening, in 8 (12.9 %) to prevent future progression. 32 patients (51.6 %) continued ocrelizumab throughout the study period, with average length of ocrelizumab use of 36.5 +/- 17.0 months. 29 patients (46.8 %) experienced no side effects during the study period. 29 (46.7 %) patients discontinued treatment, and of those, 9 (31.0 %) cited more than one reason for discontinuation: 17 (58.6 %) cited side effects, 12 (41.4 %) cited progression/lack of benefit, 6 (20.7 %) cited the Covid19 pandemic, and 1 (3.4 %) cited financial issues as a reason for discontinuation. Over the course of the study, 16 (25.8 %) patients had disability worsening by EDSS, 5 (8.1 %) had disability improvement, and 41 (66.1 %) remained stable, with a median end EDSS of 7.0 (range 6.5 to 9.5). Importantly, 18 patients (29.0 %) reported subjective disease stability while on ocrelizumab. CONCLUSIONS: Ocrelizumab may lead to disease stabilization in a subset of highly disabled MS patients, but possible benefits need to be carefully balanced against the incidence of adverse events in this high-risk patient population.

Neutropenia following immune-depletion, notably CD20 targeting, therapies in multiple sclerosis.

Neutropenia serves as a risk factor for severe infection and is a consequence of some immune-depleting immunotherapies. This occurs in people with multiple sclerosis following chemotherapy-conditioning in haematopoietic stem cell transplantation and potent B cell targeting agents. Whilst CD52 is expressed by neutrophils and may contribute to early-onset neutropenia following alemtuzumab treatment, deoxycytidine kinase and CD20 antigen required for activity of cladribine tablets, off-label rituximab, ocrelizumab, ofatumumab and ublituximab are not or only weakly expressed by neutrophils. Therefore, alternative explanations are needed for the rare occurrence of early and late-onset neutropenia following such treatments. This probably occurs due to alterations in the balance of granulopoiesis and neutrophil removal. Neutrophils are short-lived, and their removal may be influenced by drug-associated infections, the killing mechanisms of the therapies and amplified by immune dyscrasia due to influences on neutropoiesis following growth factor rerouting for B cell recovery and cytokine deficits following lymphocyte depletion. This highlights the small but evident neutropenia risks following sustained B cell depletion with some treatments.

Infections in inflammatory bowel disease patients on immunomodulator and biologic therapy are not associated with high serum drug levels.

BACKGROUND: Inflammatory bowel disease (IBD) therapies now utilise higher doses of immunomodulatory and biologic therapies, predisposing patients to an increased risk of infections. AIMS: We aimed to determine whether infections were associated with high anti-tumour necrosis factor (TNF) drug levels in IBD and to quantify the risk and consequences of infections. METHODS: Two retrospective studies were performed, a descriptive cohort study and a matched case-control study. For the matched case-control study, cases of infection occurring on anti-TNF agents were matched in a 1:2 ratio to controls of anti-TNF treated patients without infections. RESULTS: In the descriptive study, 76 infections occurred in 60 patients, including 49 bacterial, 24 viral, four fungal and four parasitic. Of these, 61 (80.3%) were on biologics, 49 (64.5%) on immunomodulators and 11 (14.5%) on corticosteroids. Thirty-four (44.7%) were on combination therapy, 27 (35.5%) on biologic monotherapy and 15 (19.7%) on immunomodulator monotherapy. Median anti-TNF drug levels in infection cases were 3.9 µg/mL for infliximab and 6.0 µg/mL for adalimumab. In the case-control study, 32 cases of infection in 27 anti-TNF treated patients were matched with 64 anti-TNF treated controls without infections. Among infection cases, 59.5% were on combination therapy versus 40.6% on biologic monotherapy (P = 0.59). Median drug levels for cases and controls respectively were 3.9 µg/mL versus 5.5 µg/mL for infliximab (P = 0.72) and 6.0 µg/mL versus 9.9 µg/mL for adalimumab (P = 0.34). CONCLUSION: Infections in patients with IBD were common, and the risk was highest with combination therapy. Infections were not associated with high serum anti-TNF levels.

Long-term outcome of natalizumab-associated progressive multifocal leukoencephalopathy in Austria: a nationwide retrospective study.

BACKGROUND/OBJECTIVE: The use of natalizumab (NAT) in multiple sclerosis (MS) may be complicated by progressive multifocal leukoencephalopathy (PML), a rare and life-threatening opportunistic brain infection. We aimed to analyze the course of MS after PML recovery together with the long-term outcome of NAT-associated PML (NAT-PML) in Austria. METHODS: Retrospective study based on identification of cases in the nationwide Austrian MS treatment registry (AMSTR) and MS centers with review of patient records. The expanded disability status scale (EDSS) was used to measure neurological disability and outcome. RESULTS: As of December 2022, we identified 15 NAT-PML cases in Austria; only 20% occurred after 2016, when increased vigilance commenced. Two patients did not survive acute PML, and an additional patient died five years later, yielding a mortality rate of 20%. Seizures occurred exclusively in patients with pronounced EDSS increase. Gadolinium (Gd)-enhancement on brain magnetic resonance imaging (MRI) on PML suspicion was associated with minor changes of post-PML neurological disability. Long-term follow-up of up to 132 months (median 76 months) was available in 11/15. The overall median EDSS increased from 3.5 at pre-PML to 6.5 at the last assessment. Regarding inflammatory MS-related disease activity during the observation period, one single individual experienced an MS relapse and another patient had two Gd-enhancing brain lesions. Three patients converted to progressive MS within three years from PML and the EDSS further increased in 6/11. CONCLUSIONS: The number of NAT-PML cases is decreasing over time. While many patients accumulated severe persistent neurological deficits compared to pre-PML, inflammatory MS-related disease activity after PML recovery was rare.