Advertisement
Original article| Volume 70, 104458, February 2023

Dimethyl fumarate treatment of primary progressive multiple sclerosis: results of an open-label extension study

  • Helene Højsgaard Chow
    Correspondence
    Corresponding author at: Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark.
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark
    Search for articles by this author
  • Jacob Talbot
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark
    Search for articles by this author
  • Henrik Lundell
    Affiliations
    Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen Denmark, Kettegård Alle 30, 2650 Hvidovre, Denmark
    Search for articles by this author
  • Lisbet Marstrand
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark
    Search for articles by this author
  • Camilla Gøbel Madsen
    Affiliations
    Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen Denmark, Kettegård Alle 30, 2650 Hvidovre, Denmark
    Search for articles by this author
  • Helle Bach Søndergaard
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark
    Search for articles by this author
  • Malene Bredahl Hansen
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark
    Search for articles by this author
  • Per Solberg Sørensen
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark

    Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Copenhagen, Denmark
    Search for articles by this author
  • Hartwig Roman Siebner
    Affiliations
    Danish Research Centre for Magnetic Resonance, Centre for Functional and Diagnostic Imaging and Research, Copenhagen University Hospital Amager and Hvidovre, Copenhagen Denmark, Kettegård Alle 30, 2650 Hvidovre, Denmark

    Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Copenhagen, Denmark

    Department of Neurology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Bispebjerg Bakke 23, 2400 Copenhagen, Denmark
    Search for articles by this author
  • Finn Sellebjerg
    Affiliations
    Danish Multiple Sclerosis Center, Copenhagen University Hospital – Rigshospitalet, Nordre Ringvej 57, 2600 Glostrup, Denmark

    Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Copenhagen, Denmark
    Search for articles by this author
Open AccessPublished:December 08, 2022DOI:https://doi.org/10.1016/j.msard.2022.104458

      Highlights

      • No clear effects of dimethyl fumarate on clinical or MRI outcome over 2 years.
      • Possible effect of dimethyl fumarate on the occurrence of new/enlarging T2 lesions.
      • Stable serum levels of neurofilament light chain and low age-adjusted NFL ratios.
      • Expected percentage of progression yet a substantial proportion improved as well.

      Abstract

      Introduction

      Dimethyl fumarate treatment is approved in Europe for patients with relapsing-remitting multiple sclerosis (MS) and in the US for relapsing forms of MS. We recently published the results of the first randomized placebo-controlled trial of 48 weeks of treatment with dimethyl fumarate or placebo in primary progressive MS (PPMS) (clinicaltrial.gov NCT02959658). The placebo-controlled phase of the trial did not meet its primary endpoint (reduction in cerebrospinal fluid concentrations of neurofilament light chain [NFL]).

      Aim

      To investigate the effects of dimethyl fumarate treatment in the open-label extension phase of the trial (week 48-96), where all patients were treated with DMF.

      Methods

      Reported data are from screening, week 48, and week 96 visits. Patients were clinically evaluated with Expanded Disability Status Scale (EDSS), 9-Hole Peg Test (9HPT), Timed 25-Foot Walk (T25FW) test, Symbol Digit Modalities Test (SDMT), California Verbal Learning Test, and Brief Visuospatial Memory-Revised. Serum NFL concentrations were measured by single-molecule array analysis. MRI was performed on a 3 tesla MRI scanner and included: new/enlarging lesions, volume of lesions, cortical grey matter, putamen, thalamus, and normal-appearing white matter, and additional diffusion tensor imaging and magnetization transfer ratio measures.

      Results

      Forty-two patients entered the open-label treatment phase, and 33 patients (61%) had complete data sets at week 96. The remaining 39% did not complete the trial and were not evaluated at week 96. We found no evidence of differences in clinical and MRI measures between patients initially treated with dimethyl fumarate and patients initially treated with placebo from baseline to week 48 and from week 48–96, where all patients were treated with dimethyl fumarate. Serum NFL concentrations remained stable in both groups over 96 weeks. Assessed with either EDSS, T25FW, or 9HPT at week 96, progression was observed for 14 patients (45%). Interestingly, another 15 patients (46%) had improvement in one or more of these domains. Applying a cut-off of 8 points, 2 (6%) patients worsened on SDMT, 25 (78%) did not change, and 5 (16%) improved.

      Conclusions

      Dimethyl fumarate treatment showed no effects on neither clinical nor MRI outcomes or changes in serum concentrations of NFL. An expected number of patients showed evidence of progression on standard clinical scales; however, this was matched by an equal number of patients improving. The reasons for the physical improvement in an unexpectedly high proportion of patients must be addressed in future studies.

      Keywords

      1. Introduction

      Patients with primary progressive multiple sclerosis (PPMS) comprise approximately 10–15% of the multiple sclerosis (MS) population. The pathogenesis of PPMS remains incompletely understood, but it is thought that adaptive and innate immune cells, as well as degenerative processes, including processes initiated by compromised energy metabolism due to mitochondrial injury, contribute. (
      • Hemmer B.
      • Kerschensteiner M.
      • Korn T.
      role of the innate and adaptive immune responses in the course of multiple Sclerosis.
      ) Treatment options for PPMS are limited, and only B cell-depleting treatment with ocrelizumab is currently approved for PPMS treatment in Europe and has shown a significant delay in the risk of disability progression. (
      • Montalban X.
      • Hauser S.L.
      • Kappos L.
      • Arnold D.L.
      • Bar-Or A.
      • Comi G.
      • De Seze J.
      • Giovannoni G.
      • Hartung H.P.
      • Hemmer B.
      • Lublin F.
      • Rammohan K.W.
      • Selmaj K.
      • Traboulsee A.
      • Sauter A.
      • Masterman D.
      • Fontoura P.
      • Belachew S.
      • Garren H.
      • Mairon N.
      • Chin P.
      • Wolinsky J.S.
      Ocrelizumab versus placebo in primary progressive multiple sclerosis.
      ,

      A. Gajofatto, M. Turatti, and M. D. Benedetti, Primary progressive multiple sclerosis: current therapeutic strategies and future perspectives, Expert Rev. Neurotherap.. doi: 10.1080/14737175.2017.1257385.

      ,
      • Wolinsky J.S.
      • Arnold D.L.
      • Brochet B.
      • Hartung H.P.
      • Montalban X.
      • Naismith R.T.
      • Manfrini M.
      • Overell J.
      • Koendgen H.
      • Sauter A.
      • Bennett I.
      • Hubeaux S.
      • Kappos L.
      • Hauser S.L.
      Long-term follow-up from the ORATORIO trial of ocrelizumab for primary progressive multiple sclerosis: a post-hoc analysis from the ongoing open-label extension of the randomised, placebo-controlled, phase 3 trial.
      )
      Dimethyl fumarate is a disease-modifying therapy with combined immunomodulatory and neuroprotective effects. (

      G. Montes Diaz, R. Hupperts, J. Fraussen, and V. Somers, Dimethyl fumarate treatment in multiple sclerosis: recent advances in clinical and immunological studies, Autoimmun. Rev.. doi: 10.1016/j.autrev.2018.07.001.

      ) Dimethyl fumarate is approved by the Food and Drug Administration as a treatment for relapsing forms of MS and by the European Medicines Agency for patients with relapsing-remitting MS. (
      • Fox R.J.
      • Miller D.H.
      • Phillips J.T.
      • Hutchinson M.
      • Havrdova E.
      • Kita M.
      • Yang M.
      • Raghupathi K.
      • Novas M.
      • Sweetser M.T.
      • Viglietta V.
      • Dawson K.T.
      Placebo-controlled phase 3 study of Oral BG-12 or glatiramer in multiple sclerosis.
      ,
      • Gold R.
      • Kappos L.
      • Arnold D.L.
      • Bar-Or A.
      • Giovannoni G.
      • Selmaj K.
      • Tornatore C.
      • Sweetser M.T.
      • Yang M.
      • Sheikh S.I.
      • Dawson K.T.
      Placebo-controlled phase 3 study of oral BG-12 for relapsing multiple sclerosis.
      ) Dimethyl fumarate and other fumaric acid esters have been investigated in progressive MS patients. One study showed no disease progression in 75% of the treated patients and that fumaric acid esters were well tolerated. (
      • Strassburger Krogias K.
      • Ellrichmann G.
      • Krogias C.
      • Altmeyer P.
      • Chan A.
      • Gold R.
      Fumarate treatment in progressive forms of multiple sclerosis: first results of a single-center observational study.
      ) Another study showed a trend towards improvement in ambulation, compared with patients treated with glatiramer acetate. (
      • Moreira Ferreira V.F.
      • Liu Y.
      • Healy B.C.
      • Stankiewicz J.M.
      Effectiveness and safety of dimethyl fumarate in progressive multiple sclerosis.
      ) We recently completed the first randomized placebo-controlled trial investigating dimethyl fumarate treatment in patients with PPMS. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ) The trial did not meet its primary endpoint of reducing the cerebrospinal fluid (CSF) concentrations of neurofilament light chain (NFL), a marker of neuroaxonal injury. Neither did we find effects on other biomarkers of tissue injury or inflammation in CSF after treatment with dimethyl fumarate, except for a decrease in the number of CD4+ T cells and a corresponding increase in concentrations of the CD4+ T cell growth factor interleukin-7 in CSF. (
      • Talbot J.
      • Højsgaard Chow H.
      • Holm Hansen R.
      • von Essen M.R.
      • Sellebjerg F.
      Immunological effects of dimethyl fumarate treatment in blood and CSF of patients with primary progressive MS.
      )
      In MS, increased NFL levels in the CSF have been shown to be associated with the amount of focal inflammation, but NFL levels may also be associated with more diffuse pathology. (
      • Kuhle J.
      • Kropshofer H.
      • Haering D.A.
      • Kundu U.
      • Meinert R.
      • Barro C.
      • Dahlke F.
      • Tomic D.
      • Leppert D.
      • Kappos L.
      Blood neurofilament light chain as a biomarker of MS disease activity and treatment response.
      ,
      • Saraste M.
      • Bezukladova S.
      • Matilainen M.
      • Tuisku J.
      • Rissanen E.
      • Sucksdorff M.
      • Laaksonen S.
      • Vuorimaa A.
      • Kuhle J.
      • Leppert D.
      • Airas L.
      High serum neurofilament associates with diffuse white matter damage in MS.
      ,
      • Kapoor R.
      • Smith K.E.
      • Allegretta M.
      • Arnold D.L.
      • Carroll W.
      • Comabella M.
      • Furlan R.
      • Harp C.
      • Kuhle J.
      • Leppert D.
      • Plavina T.
      • Sellebjerg F.
      • Sincock C.
      • Teunissen C.E.
      • Topalli I.
      • von Raison F.
      • Walker E.
      • Fox R.J.
      Serum neurofilament light as a biomarker in progressive multiple sclerosis.
      ) NFL can be measured in serum, which provides a fast and readily accessible way of assessing neuroaxonal damage. (
      • Kuhle J.
      • Barro C.
      • Andreasson U.
      • Derfuss T.
      • Lindberg R.
      • Sandelius Å.
      • Liman V.
      • Norgren N.
      • Blennow K.
      • Zetterberg H.
      Comparison of three analytical platforms for quantification of the neurofilament light chain in blood samples: ELISA, electrochemiluminescence immunoassay and simoa.
      ) The serum concentration of NFL has been proposed as a treatment-responsive biomarker in MS, and treatment with dimethyl fumarate has been shown to reduce the concentrations of NFL in serum and CSF. (
      • Sejbaek T.
      • Nielsen H.H.
      • Penner N.
      • Plavina T.
      • Mendoza J.P.
      • Martin N.A.
      • Elkjaer M.L.
      • Ravnborg M.H.
      • Illes Z.
      Dimethyl fumarate decreases neurofilament light chain in CSF and blood of treatment naïve relapsing MS patients.
      ,
      • Delcoigne B.
      • Manouchehrinia A.
      • Barro C.
      • Benkert P.
      • Michalak Z.
      • Kappos L.
      • Leppert D.
      • Tsai J.A.
      • Plavina T.
      • Kieseier B.C.
      • Lycke J.
      • Alfredsson L.
      • Kockum I.
      • Kuhle J.
      • Olsson T.
      • Piehl F.
      Blood neurofilament light levels segregate treatment effects in multiple sclerosis.
      ) Here, we report the results from the open-label extension phase of the placebo-controlled treatment trial of dimethyl fumarate treatment in PPMS, including data on serum NFL, using a novel method for correcting the effect of age.

      2. Methods

      2.1 Study design and patients

      The study was a single-center study conducted at the Danish Multiple Sclerosis Center, Copenhagen University Hospital - Rigshospitalet. Inclusion criteria for the study were in brief: age 18–65 years, Expanded Disability Status Scale (EDSS) score 0–6.5, PPMS diagnosis, and NFL concentration above 380 ng/L in CSF. Key exclusion criteria were: immunomodulatory treatment within 6 months or treatment with corticosteroids within 3 months prior to enrollment. All in- and exclusion criteria are specified elsewhere. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ) The open-label extension phase with twice-daily oral dimethyl fumarate 240 mg (Biogen, Cambridge, MA, USA) followed the 48 weeks randomized, double-blind, placebo-controlled phase and lasted 48 weeks. All participants followed a titration schedule as follows: From day one to 21, dimethyl fumarate was titrated from 120 mg to 480 mg daily as maintenance dose. Sixty patients were screened to randomize 54 in the treatment trial. All 6 screen failures were invited for reassessment at week 48 to establish eligibility for the open-label phase. Eligibility was based on: 1 point increase in EDSS score if screening EDSS <6; 0.5 point increase in EDSS score from screening to week 48 if screening EDSS>5.5; 2 point increase in a physical functional system or; worsening in SDMT, 9HPT or T25FW >20% from screening to week 48. Only 1 out of 4 re-assessed patients were eligible for re-entry to the trial.

      2.2 Standard protocol approvals, registrations, and patient consents

      The study was undertaken in accordance with the International Conference on Harmonization of Good Clinical Practice (ICH-GCP) and the declaration of Helsinki. The study was approved by the Danish Medicines Agency and the Regional Ethical Committee (H-16032162), and monitoring was provided by the ICH-GCP Unit at Copenhagen University Hospital Bispebjerg. All patients signed written informed consent. The approved study protocol is available at www.dmsc.dk. The study is registered at ClinicalTrials.gov, number: NCT02959658. This study followed the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline for randomized clinical trials.

      2.3 Procedures

      Serum samples from screening, week 48 and 96 were stored at minus 80 degrees Celsius and later thawed for analyses of serum NFL. Serum NFL values were measured using single-molecule array analysis (SIMOA, Quanterix®). For a full description of sample handling and analyses, see the appendix (sections 1.1 and 1.2). Age-dependent reference levels for serum NFL in healthy Danish adults were previously reported. (
      • Hviid C.V.B.
      • Knudsen C.S.
      • Parkner T.
      Reference interval and preanalytical properties of serum neurofilament light chain in scandinavian adults.
      ) Using these age-dependent reference values, we calculated the serum NFL ratio as the ratio between the measured NFL level and the upper 97.5% reference level for the age of the specific patient. Serum NFL-ratio levels >1.0 were classified as increased:
      serumNFLratio=[serumNFL(ng/l)]4.19ng/lx1.029age(years)


      All patients were scanned on the same 3 tesla Verio MRI scanner (Siemens Healthcare, Erlangen, Germany). MRI data were analyzed at the independent MRI reading center at Copenhagen University Hospital, Hvidovre. MRI included the brain and the spinal cord until spinal level C2. The segmentation of lesions was performed with the automated longitudinal pipeline in the LST software, which provides an objective threshold for significantly evolving lesions to avoid inter-rater bias in the longitudinal lesion quantification. (
      • Schmidt P.
      • Pongratz V.
      • Küster P.
      • Meier D.
      • Wuerfel J.
      • Lukas C.
      • Bellenberg B.
      • Zipp F.
      • Groppa S.
      • Sämann P.G.
      • Weber F.
      • Gaser C.
      • Franke T.
      • Bussas M.
      • Kirschke J.
      • Zimmer C.
      • Hemmer B.
      • Mühlau M.
      Automated segmentation of changes in FLAIR-hyperintense white matter lesions in multiple sclerosis on serial magnetic resonance imaging.
      ,
      • Schmidt P.
      • Gaser C.
      • Arsic M.
      • Buck D.
      • Förschler A.
      • Berthele A.
      • Hoshi M.
      • Ilg R.
      • Schmid V.J.
      • Zimmer C.
      • Hemmer B.
      • Mühlau M.
      An automated tool for detection of FLAIR-hyperintense white-matter lesions in multiple sclerosis.
      ) This method is different from previously published papers from this study. A full description of the MRI protocol was published with the results from the placebo-controlled phase, and a description of the automated segmentation method can be found in the appendix of this paper (section 1.3). (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      )

      2.4 Clinical outcome measures and adverse event reporting

      Trained study nurses or physicians performed Timed 25-Foot Walk (T25FW) and Nine-Hole Peg Test (9HPT) and employed the Brief International Assessment for MS panel consisting of Symbol Digit Modalities Test (SDMT), California Verbal Learning Test (CVLT-II), and Brief Visuospatial Memory Test-Revised (BVMT-R). (

      D. W. Langdon, M. P. Amato, J. Boringa, B. Brochet, F. Foley, S. Fredrikson, P. Hämäläinen, H. P. Hartung, L. Krupp, I. K. Penner, A. T. Reder, and R. H. B. Benedict, Recommendations for a brief international cognitive assessment for multiple sclerosis (BICAMS), Mult. Scler. J.. doi: 10.1177/1352458511431076.

      ) SDMT and BVMT-R were applied in different versions throughout the study, and an expert neuropsychologist scored the BVMT-R. CVLT-II was applied in 2 different versions alternating. Worsening or improvement in EDSS was determined as a change of 1 or more points at screening EDSS values of 2.0–5.0 and a change of 0.5 points or more at screening EDSS values of 5.5–6.5. Relevant clinical change in T25FW and 9HPT was determined as a change of 20% or more. (
      • Cadavid D.
      • Cohen J.A.
      • Freedman M.S.
      • Goldman M.D.
      • Hartung H.P.
      • Havrdova E.
      • Jeffery D.
      • Kapoor R.
      • Miller A.
      • Sellebjerg F.
      • Kinch D.
      • Lee S.
      • Shang S.
      • Mikol D.
      The EDSS-Plus, an improved endpoint for disability progression in secondary progressive multiple sclerosis.
      ) Recently, different cut-off levels for determining a significant decrease in SDMT have been proposed. (
      • Strober L.B.
      • Bruce J.M.
      • Arnett P.A.
      • Alschuler K.N.
      • DeLuca J.
      • Chiaravalloti N.
      • Lebkuecher A.
      • Di Benedetto M.
      • Cozart J.
      • Thelen J.
      • Cadden M.
      • Guty E.
      • Román C.A.F.
      A much needed metric: defining reliable and statistically meaningful change of the oral version symbol digit modalities test (SDMT).
      ,
      • Weinstock Z.
      • Morrow S.
      • Conway D.
      • Fuchs T.
      • Wojcik C.
      • Unverdi M.
      • Zivadinov R.
      • Weinstock-Guttman B.
      • Iverson G.L.
      • Dwyer M.
      • Benedict R.H.B.
      Interpreting change on the symbol digit modalities test in people with relapsing multiple sclerosis using the reliable change methodology.
      ) We applied a cut-off level of 8 points as suggested by Weinstock et al. (
      • Weinstock Z.
      • Morrow S.
      • Conway D.
      • Fuchs T.
      • Wojcik C.
      • Unverdi M.
      • Zivadinov R.
      • Weinstock-Guttman B.
      • Iverson G.L.
      • Dwyer M.
      • Benedict R.H.B.
      Interpreting change on the symbol digit modalities test in people with relapsing multiple sclerosis using the reliable change methodology.
      )
      Common Terminology Criteria for Adverse Events (CTCAE) was used to report adverse events. Safety assessments included a physical examination every 24 weeks, along with an assessment of vital parameters and safety blood tests every 12 weeks. In addition, all MRI scans were clinically assessed by the same experienced neuroradiologist for assessment of disease activity and non-MS-related pathology.

      3. Statistics

      The group was dichotomized based on treatment allocation in the randomized placebo-controlled phase. Inter-group comparisons were made using paired t-tests. Group 1 received placebo in the randomized phase and switched to active treatment in the open-label phase, and group 2 received active treatment at both study intervals.
      As the study was descriptive and exploratory, endpoints were tested at a nominal significance level of 5% without adjustment for multiple testing. SPSS v25 was applied for all statistical analyses.

      4. Results

      Fifty-four patients were randomized in the placebo-controlled phase of the study. Four patients (7%) dropped out in this phase. Fifty (93%) patients were eligible for entry into the open-label phase. However, 5 (10%) patients did not continue in the open-label phase, and 4 (8%) were excluded due to prolonged lymphopenia. The 5 patients who did not enter the open-label phase were discounted for the following reasons: side effects of the treatment; difficulty with transport to the clinic; worry that the treatment worsened the MS symptoms; switching to ocrelizumab treatment; unreachable by the trial staff. Four out of 6 non-randomized patients were re-assessed at week 48, and 1 was eligible for entry into the open-label phase based on worsening in EDSS of more than 1 point. Thus, a total of 42 patients (78%) entered the open-label phase. Nine patients (21%) dropped out during the open-label phase. Thirty-three (79%) had complete data sets at week 96. A detailed report of the trial profile can be seen in Fig. 1, and the demographics of the participants are shown in Table 1. Additional demographics and patient characteristics can be seen in the appendix (Table A1).
      Fig 1
      Fig. 1Trial profile.
      Overview of participant inclusion and drop out in the open-label phase week 48–96.
      Table 1Baseline characteristics at week 48.
      CharacteristicPlacebo (n = 22)Dimethyl fumarate (n = 20)
      Age (years)56.2 (5.6)55.7 (5.6)
      Female, n (%)9 (41%)7 (35%)
      EDSS, median [IQR]4.0 [3.5–5.6]4.5 [4.0–6.0]
      Disease duration (years)13.3 (8.2)13.9 (8.6)
      Gd-enhancing lesions
       2; n (%)1 (4.5%)0
       1; n (%)1 (4.5%)0
       0; n (%)20 (91.0%)20 (100%)
       NA; n (%)1 (4.5%)0
      Serum NFL (ng/l), median [IQR]13.4 [11.0–16.2]12.8 [8.5–16.6]
      Serum NFL-ratio, median [IQR]0.61 [0.53–0.82]0.61 [0.47–0.72]
      Values are gives as mean with standard deviation (SD) unless otherwise specified. One patient was eligible for re-entry to the trial at the open-label phase after reassessment at week 48. Data for this patient is included in the placebo column.
      EDSS = expanded disability status scale; Gd = Gadolinium; IQR = inter-quartile range; NFL = neurofilament light chain.
      There was no significant change in disability at a group level upon treatment with dimethyl fumarate from week 48-96, except for a worsening in non-dominant 9HPT in the original placebo group (p = 0.024) (Table 2).
      Table 2Changes in clinical measures and neurofilament light chain from screening to week 48 and from week 48 to 96 for the initial dimethyl fumarate group and control group.
      Initial placebo groupInitial dimethyl fumarate group
      Untreated

      Week 0-48

      n = 16
      Dimethyl fumarate

      Week 48-96

      n = 16
      pDimethyl fumarate

      Week 0-48

      n = 17
      Dimethyl fumarate

      Week 48-96

      n = 17
      p
      EDSS0.00 (-0.68–0.68)0.22 (-0.10–0.54)0.5420.15 (-0.23–0.52)0.00 (-0.22–0.22)0.369
      T25FW, average (s)-0.06 (-0.50–0.38)0.44 (-0.28–1.16)0.2040.56 (-0.92–2.04)-0.48 (-2.31–1.36)0.391
      9HPT dominant, average (s)-1.05 (-2.15–0.05)1.02 (-1.08–3.12)0.085-2.35 (-4.38–-3.33)2.11 (-1.57–5.80)0.099
      9HPT non-dominant, average (s)-1.62 (-4.20–0.97)2.31 (-0.16–4.78)0.0248.18 (-8.64–25.00)3.42 (1.01–5.83)0.093
      SDMT, no. correct in 90s4.2 (0.9–7.5)-1.4 (-5.4–2.6)0.0932.9 (-0.8–6.6)-1.2 (-4.4–2.0)0.156
      CVLT-II, out of 80 points2.7 (-3.2–8.5)1.9 (-4.1–7.9)0.8871.0 (-3.0–5.0)1.529412 (-1.8–4.8)0.860
      BVMT-R, out of 36 points0.5 (-2.4–3.4)-0.7 (-3.7–2.3)0.7220.8 (-1.9–3.4)-0.1 (-2.4–2.2)0.670
      NFL in serum (ng/l)0.30 (-1.9–2.4)-0.17 (-3.1–2.8)0.829-0.15 (-4.4–4.1)-1.6 (-6.1–2.8)0.712
      Serum NFL-ratio-0.00 (-0.1–0.0)-0.07 (-0.2–0.1)0.565-0.03 (-0.3–0.2)-0.11 (-0.4–0.1)0.699
      Results are given as mean difference with 95% confidence interval. Analyses on differences between groups were performed with paired t-test.
      BVMT-R = Brief Visuospatial Memory Test-Revised; CVLT-II = California Verbal Learning Test 2; EDSS = expanded disability status scale; NFL = neurofilament light chain; SDMT = Symbol Digit Modalities Test; T25FW = timed 25-foot walk; 9HPT = 9-hole peg test.
      Seven (12%) out of 60 screened patients had a serum NFL ratio above 1.0, indicating elevated levels for their age (range: 1.05–1.91), and 4 (10%) of the 42 patients entering the open-label phase had an increased NFL ratio (range: 1.20–2.49). There was no difference in serum NFL concentrations between the patients treated with dimethyl fumarate and placebo from baseline to week 48 (Table 2), and concentrations remained stable over time (Fig. 2).
      Fig 2
      Fig. 2Scatterplots of serum NFL values.
      NFL values plotted for each period in the trial. X- and Y-axis are log-transformed.
      NFL = neurofilament light chain.
      Fourteen patients (42%) had physical disease progression assessed with either EDSS, T25FW, or 9HPT at week 96. However, another 15 patients (46%) had improved in one or more of the physical domains at week 96. A total overview of worsening and improvement on EDSS, T25FW, 9HPT, and SDMT can be seen in Table 3. Six (18%) of the 7 patients with EDSS worsening was confirmed from week 72 to 96, and 5 (15%) of the 6 with EDSS improvements was confirmed from week 72 to 96. Applying a cut-off of 8 points on the SDMT, 2 (6%) patients worsened, 25 (78%) did not change, and 5 (16%) improved.
      Table 3Number of patients showing clinically relevant changes from screening to week 96 in selected clinical measures.
      WorsenedUnchangedImproved
      EDSS, no.7 (21%)20 (61%)6 (18%)
      T25FW, no.7 (22%)19 (59%)6 (19%)
      9HPT dominant, no.3 (9%)25 (76%)5 (15%)
      9HPT non-dominant, no.3 (10%)23 (77%)4 (13%)
      SDMT, no.2 (6%)25 (78%)5 (16%)
      Definitions of clinical change: EDSS increase or decrease of at least 1.0 point (from EDSS 2.0–5.0) or 0.5 points (from EDSS above 5.5). T25FW and 9HPT increase or decrease of at least 20%. SDMT increase or decrease of at least 12 points.
      T25FW: missing data n = 1
      9HPT non-dominant: data missing n = 3
      SDMT: data missing n = 1
      EDSS = expanded disability status scale; SDMT = Symbol Digit Modalities Test; T25FW = timed 25-foot walk; 9HPT = 9-hole peg test.
      MRI results are summarized in Table 4. We found several nominally significant results regarding cortical grey matter (CGM) in the patients initially randomized to dimethyl fumarate and continuing dimethyl fumarate treatment from week 48-96. However, they were all explained by an initial change from screening to week 48, followed by an almost equal reverse change from week 48 to week 96. Only few patients developed new lesions in either period of the entire trial. In the placebo group during the randomized phase, 1 patient developed 3 new lesions, and 2 developed 1 new lesion each. During the same period, 2 patients in the dimethyl fumarate-treated group each developed 1 new lesion. In the open-label phase, 1 patient had 2 new lesions, and 2 patients had 1 new lesion each in the initially placebo-treated group. In the group that had received dimethyl fumarate during the randomized phase, there was 1 patient with 2 new lesions in the extension phase. Likewise, enlarging lesions were rare in either period of the trial. In the randomized phase of the trial, the treated group had no enlarging lesions, whereas, in the placebo group, 1 patient had 4 enlarging lesions, 1 patient had 3 enlarging lesions, and 1 patient had 1 enlarging lesion. In the open-label phase, there were no enlarging lesions in the group that received placebo during the randomized phase. In the group that had received dimethyl fumarate in the randomized phase, there was 1 patient with 1 enlarging lesion from week 48-96.
      Table 4Changes in magnetic resonance imaging measures from screening to week 48 and from week 48 to 96 for the initial dimethyl fumarate group and control group.
      Initial placebo groupInitial dimethyl fumarate group
      Untreated

      Week 0-48

      n = 16
      Dimethyl fumarate

      Week 48-96

      n = 16
      pDimethyl fumarate

      Week 0-48

      n = 17
      Dimethyl fumarate

      Week 48-96

      n = 17
      p
      CGM volume (ml)-0.01 (-4.94–4.72)-1.17 (-4.99–2.65)0.722-7.23 (-12.56–-1.91)5.63 (0.25–11.00)0.005
      NAWM volume (ml)-3.46 (-10.44–3.51)-0.15 (-11.40–11.10)0.6250.84 (-4.12–5.81)-1.45 (-9.32–6.42)0.670
      Lesion volume (ml)0.11 (-0.23–0.44)0.11 (-0.11–0.33)0.983-0.05 (-0.12–0.11)0.30 (-0.08–0.68)0.107
      No. new lesions, total54NA22NA
      No. enlarging lesions, total80NA01NA
      Thalamus volume (ml)0.16 (-0.24–0.57)0.02 (-0.31–0.35)0.448-0.09 (-0.15–-0.03)-0.00 (-0.12–0.11)0.266
      Putamen volume (ml)0.08 (-0.05–0.24)0.05 (-0.21–0.30)0.715-0.05 (-0.14–-0.03)-0.00 (-0.08–0.08)0.466
      MD in CGM (µm2/ms)-0.002 (-0.016–0.013)-0.120 (-0.260–0.021)0.7800.005 (-0.006–0.017)-0.274 (-0.472–-0.076)0.020
      MD in NAWM (µm2/ms)0.006 (0.001–0.012)0.006 (-0.001–0.012)0.9720.002 (-0.008–0.013)0.006 (-0.003–0.015)0.603
      MD in lesions (µm2/ms)-0.004 (-0.020–0.012)0.014 (-0.006–0.034)0.2060.005 (-0.014–0.024)0.007 (-0.005–0.019)0.576
      MD in thalamus (µm2/ms)0.002 (-0.017–0.021)-0.037 (-0.128–0.054)0.856-0.001 (-0.022–0.019)0.009 (-0.004–0.022)0.267
      MD in putamen (µm2/ms)0.004 (-0.005–0.013)0.015 (-0.000–0.031)0.2450.009 (-0.008–0.025)0.008 (-0.011–0.028)0.949
      FA in CGM0.000 (-0.004–0.004)-0.001 (-0.004–0.002)0.584-0.004 (-0.007–-0.002)-0.001 (-0.002–0.004)0.033
      FA in NAWM-0.003 (-0.010–0.003)-0.002 (-0.002–0.006)0.217-0.002 (-0.007–0.004)-0.003 (-0.008–0.003)0.194
      FA in lesions0.002 (-0.004–0.009)-0.001 (-0.011–0.009)0.5310.002 (-0.005–0.009)-0.005 (-0.013–0.003)0.355
      FA in thalamus0.002 (-0.005–0.009)-0.003 (-0.012–0.005)0.301-0.002 (-0.010–0.006)-0.006 (-0.011–-0.001)0.188
      FA in putamen-0.010 (-0.031–0.012)-0.004 (-0.019–0.011)0.438-0.001 (-0.009–0.006)-0.011 (-0.040–0.017)0.483
      MTR in CGM (PU)0.2 (-0.5–1.0)-0.1 (-0.8–0.6)0.5710.4 (-0.2–1.0)-0.3 (-0.5–-0.0)0.029
      MTR in NAWM (PU)0.2 (-0.4–0.8)0.2 (-0.2–0.6)0.9870.4 (-0.1–1.0)-0.1 (-0.3–0.2)0.162
      MTR in lesions (PU)0.1 (-0.6–0.8)0.7 (0.3–1.1)0.1760.7 (0.1–1.2)0.1 (-0.2–0.4)0.180
      MTR in thalamus (PU)0.1 (-0.5–0.6)0.4 (-0.2–1.0)0.3830.4 (-0.2–1.0)0.2 (-0.4–0.7)0.772
      MTR in putamen (PU)0.1 (-0.6–0.8)-0.2 (-0.9–0.5)0.5160.3 (-0.4–1.0)0.2 (-0.3–0.8)0.938
      Results are given as mean difference with 95% confidence interval. Analyses on differences between groups were performed with paired t-test.
      FA = fractional anisotropy; CGM = cortical grey matter; MD = mean diffusivity; MTR = magnetization transfer ratio; NAWM = Normal Appearing White Matter; PU = percentage units.
      The results for physical, cognitive, and MRI changes in the combined group, looking at the entire trial from baseline to week 96, can be seen in the appendix (Table A2). Overall, the patients were remarkably stable, but the T2 lesion volume increased, and mean diffusivity (MD) in normal-appearing white matter (NAWM) and putamen increased over the 96 weeks of the study.
      An overview of adverse events is given in Table 5. The adverse events in the open-label phase were comparable to those reported in the randomized phase, except for a decrease in flu-like symptoms and fewer reports of flushing. In addition, there were fewer events of grade 2 and 3 lymphopenia. Overall, the frequency of infection in the open-label phase was comparable to the somewhat increased frequency observed in the treatment group in the randomized phase, but there were no opportunistic infections. The occurrence of serious adverse events was comparable to the frequency in the randomized phase, with one case of basal cell carcinoma in the open-label phase. Adverse events occurring in less than 5% can be seen in the appendix (Table A3).
      Table 5Adverse events week 48–96.
      Any adverse event; n (%)37 (88.1)
      Adverse event ≥ 5%; n (%)
       Flushing15 (35.7)
       Gastrointestinal pain7 (16.7)
       Diarrhea6 (14.3)
       Headache6 (14.3)
       Upper respiratory infection5 (11.9)
       Urinary tract infection5 (11.9)
       Nausea4 (9.5)
      One of these was a serious adverse event.
       Back pain3 (7.1)
       Fall3 (7.1)
      Lymphocyte count decrease; n (%)
       Grade 1 (<LLN – 0.8 × 10 10e9 /l)3 (7.1)
       Grade 2 (<0.8 – 0.5 × 10 10e9 /l)4 (9.5)
       Grade 3 (<0.5 – 0.2 × 10 10e9 /l)7 (16.7)
      Adverse event by severity; n
       Mild (grade 1)29 (69.0)
       Moderate (grade 2)19 (45.2)
       Severe (grade 3)11 (26.2)
       Life-threatening (grade 4)0
      Death (grade 5)0
      Serious adverse events; n (%)
       Dyspepsia1 (2.4)
       Nausea1 (2.4)
       Basal cell carcinoma1 (2.4)
       Urinary retention1 (2.4)
       Sepsis, urosepsis1 (2.4)
      Treatment related serious adverse event0
      Study withdrawal because of change of therapy1 (2.4)
      Study withdrawal because of adverse event8 (19.0)
       Lymphopenia (grade 3)2 (4.8)
       Edema and/or joint pain2 (4.8)
       Diarrhea and or/gastrointestinal pain2 (4.8)
       Flushing1 (2.4)
       Vertigo1 (2.4)
      low asterisk One of these was a serious adverse event.

      5. Discussion

      We found no obvious effects of treatment with dimethyl fumarate in the open-label, extended phase of the randomized, controlled trial, where patients were offered open-label treatment with dimethyl fumarate for 48 weeks after the initial 48 weeks of treatment with either dimethyl fumarate or placebo. There was a significant worsening in dexterity (assessed with 9HPT) from week 48 to week 96 in the group initially treated with placebo. However, this worsening was not supported by a similar deterioration from screening to week 48 in the patients initially treated with dimethyl fumarate, and the finding is likely coincidental. Previously, a study reported no disease progression in 75% of progressive MS patients treated with fumaric acid esters. (
      • Strassburger Krogias K.
      • Ellrichmann G.
      • Krogias C.
      • Altmeyer P.
      • Chan A.
      • Gold R.
      Fumarate treatment in progressive forms of multiple sclerosis: first results of a single-center observational study.
      ) This seemingly indicates a potential effect of dimethyl fumarate in progressive MS; however, there was no control group, and the follow-up time was highly variable. Our results show that PPMS patients, on average, are clinically and MRI stable over 2 years, with or without dimethyl fumarate treatment. Overall, we show comparable progression rates for this cohort of patients with PPMS compared to previous results. (
      • Cadavid D.
      • Cohen J.A.
      • Freedman M.S.
      • Goldman M.D.
      • Hartung H.P.
      • Havrdova E.
      • Jeffery D.
      • Kapoor R.
      • Miller A.
      • Sellebjerg F.
      • Kinch D.
      • Lee S.
      • Shang S.
      • Mikol D.
      The EDSS-Plus, an improved endpoint for disability progression in secondary progressive multiple sclerosis.
      ,
      • Kapoor R.
      • Ho P.R.
      • Campbell N.
      • Chang I.
      • Deykin A.
      • Forrestal F.
      • Lucas N.
      • Yu B.
      • Arnold D.L.
      • Freedman M.S.
      • Goldman M.D.
      • Hartung H.P.
      • Havrdová E.K.
      • Jeffery D.
      • Miller A.
      • Sellebjerg F.
      • Cadavid D.
      • Mikol D.
      • Steiner D.
      • Bartholomé E.
      • D'Hooghe M.
      • Pandolfo M.
      • Van Wijmeersch B.
      • Bhan V.
      • Blevins G.
      • Brunet D.
      • Devonshire V.
      • Duquette P.
      • Freedman M.
      • Grand'Maison F.
      • Jacques F.
      • Lapierre Y.
      • Lee L.
      • Morrow S.
      • Yeung M.
      • Dufek M.
      • Havrdová E.K.
      • Kanovsky P.
      • Stetkarova I.
      • Talabova M.
      • Frederiksen J.
      • Kant M.
      • Petersen T.
      • Ravnborg M.
      • Sellebjerg F.
      • Airas L.
      • Elovaara I.
      • Eralinna J.P.
      • Sarasoja T.
      • Al Khedr A.
      • Brassat D.
      • Brochet B.
      • Camu W.
      • Debouverie M.
      • Laplaud D.
      • Lebrun Frenay C.
      • Pelletier J.
      • Vermersch P.
      • Vukusi S.
      • Baum K.
      • Berthele A.
      • Faiss J.
      • Flachenecker P.
      • Hohlfeld R.
      • Krumbholz M.
      • Lassek C.
      • Maeurer M.
      • Meuth S.
      • Ziemssen T.
      • Hardiman O.
      • McGuigan C.
      • Achiron A.
      • Karussis D.
      • Bergamaschi R.
      • Morra V.B.
      • Comi G.
      • Cottone S.
      • Grimaldi L.
      • Mancardi G.L.
      • Massacesi L.
      • Nocentini U.
      • Salvetti M.
      • Scarpini E.
      • Sola P.
      • Tedeschi G.
      • Trojano M.
      • Zaffaroni M.
      • Frequin S.
      • Hupperts R.
      • Killestein J.
      • Schrijver H.
      • Van Dijl R.
      • van Munster E.
      • Czarnecki M.
      • Drozdowski W.
      • Fryze W.
      • Hertmanowska H.
      • Ilkowski J.
      • Kaminska A.
      • Klodowska-Duda G.
      • Maciejowski M.
      • Motta E.
      • Podemski R.
      • Potemkowski A.
      • Rog T.
      • Selmaj K.
      • Stelmasiak Z.
      • Stepien A.
      • Tutaj A.
      • Zaborski J.
      • Boyko A.
      • Chefranova Z.
      • Evdoshenko E.
      • Khabirov F.
      • Sivertseva S.
      • Yakupov E.
      • Alvarez Cermeño J.C.
      • Escartin A.
      • Fernandez O.F.
      • Garcia-Merino A.
      • Hernandez Perez M.A.
      • Ayuso G.I.
      • Lallana J.M.
      • Gairin X.M.
      • Oreja-Guevara C.
      • Saiz Hinarejos A.
      • Gunnarsson M.
      • Lycke J.
      • Martin C.
      • Piehl F.
      • Roshanisefat H.
      • Sundstrom P.
      • Duddy M.
      • Gran B.
      • Harrower T.
      • Hobart J.
      • Kapoor R.
      • Lee M.
      • Mattison P.
      • Nicholas R.
      • Pearson O.
      • Rashid W.
      • Rog D.
      • Sharrack B.
      • Silber E.
      • Turner B.
      • Williams A.
      • Woolmore J.
      • Young C.
      • Bandari D.
      • Berger J.
      • Camac A.
      • Cohan S.
      • Conway J.
      • Edwards K.
      • Fabian M.
      • Florin J.
      • Freedman S.
      • Garwacki D.
      • Goldman M.
      • Harrison D.
      • Herrman C.
      • Huang D.
      • Javed A.
      • Jeffery D.
      • Kamin S.
      • Katsamakis G.
      • Khatri B.
      • Langer-Gould A.
      • Lynch S.
      • Mattson D.
      • Miller T.
      • Miravalle A.
      • Moses H.
      • Muley S.
      • Napier J.
      • Nielsen A.
      • Pachner A.
      • Pardo G.
      • Picone M.A.
      • Robertson D.
      • Royal W.
      • Sheppard C.
      • Thrower B.
      • Twyman C.
      • Waubant E.
      • Wendt J.
      • Yadav V.
      • Zabad R.
      • Zarelli G.
      Effect of natalizumab on disease progression in secondary progressive multiple sclerosis (ASCEND): a phase 3, randomised, double-blind, placebo-controlled trial with an open-label extension.
      ) However, we cannot comment on confirmed worsening on T25FW and 9HPT individually, as these were not tested at week 72. Overall, the patients were relatively stable (i.e., no signs of disease activity) during the entire trial period, as assessed with MRI. However, T2 lesion volume increased, and MD in NAWM and putamen increased over the 96 weeks of the study. We have previously demonstrated that this cohort has comparable levels of many biomarkers of inflammation in CSF with that of relapsing-remitting MS patients and significantly elevated levels compared with healthy controls. We found no effect on these factors by dimethyl fumarate treatment. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ,
      • Talbot J.
      • Højsgaard Chow H.
      • Holm Hansen R.
      • von Essen M.R.
      • Sellebjerg F.
      Immunological effects of dimethyl fumarate treatment in blood and CSF of patients with primary progressive MS.
      ,
      • Talbot J.
      • Chow H.H.
      • Mahler M.
      • Buhelt S.
      • Hansen R.H.
      • Lundell H.
      • Vinther-Jensen T.
      • Hellem M.N.N.
      • Nielsen J.E.
      • Siebner H.R.
      • von Essen M.R.
      • Sellebjerg F.
      Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis.
      )
      Somewhat surprisingly, we found that several PPMS patients improved on physical measures during the 2-years of follow-up. The physical improvements seen in collectively 46% of the patients are likely explained by optimization of supportive measures by the trial personnel, e.g., referral for physical therapy and perhaps some degree of learning effects. No patients initiated fampridine therapy during the trial. This treatment was tested and initiated in relevant subjects before screening, and all eligible patients remained on fampridine treatment throughout the trial. Reports of physical improvements in longitudinal studies in progressive MS are sparse. However, previous reports from the ASCEND trial comparing natalizumab and placebo showed a sustained significant improvement in the multicomponent endpoint of physical measures and in T25FW alone in the treatment group. (
      • Giovannoni G.
      • Steiner D.
      • Sellebjerg F.
      • Cohan S.
      • Jeffery D.
      • Rog D.
      • Chen Y.
      • Dong Q.
      • Ho P.-R.
      • Campbell N.
      • Cadavid D.
      • Amarante D.
      Sustained disability improvement as assessed by a multicomponent endpoint in secondary progressive multiple sclerosis (SPMS) patients: a post hoc analysis from ASCEND (P5.359).
      ) Although our cohort is very small, compared with the cohort in the ASCEND study, we show an even higher degree of improvement in EDSS, T25FW, and collectively improvement of 46%. Because we have been unable to show any treatment effects of dimethyl fumarate in our cohort through several investigative measures, the cohort can be viewed as non-treated. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ,
      • Talbot J.
      • Højsgaard Chow H.
      • Holm Hansen R.
      • von Essen M.R.
      • Sellebjerg F.
      Immunological effects of dimethyl fumarate treatment in blood and CSF of patients with primary progressive MS.
      ,
      • Talbot J.
      • Chow H.H.
      • Mahler M.
      • Buhelt S.
      • Hansen R.H.
      • Lundell H.
      • Vinther-Jensen T.
      • Hellem M.N.N.
      • Nielsen J.E.
      • Siebner H.R.
      • von Essen M.R.
      • Sellebjerg F.
      Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis.
      ) Therefore, our finding of a substantial degree of improvement is very interesting in itself.
      Until recently, a cut-off of 4 points on the SDMT was used as a threshold for significant change at a group level. This was based on work published in 2010, which concluded that a worsening of at least 4 points was associated with a decline in work status. (
      • Morrow S.A.
      • Drake A.
      • Zivadinov R.
      • Munschauer F.
      • Weinstock-Guttman B.
      • Benedict R.H.B.
      Predicting loss of employment over three years in multiple sclerosis: clinically meaningful cognitive decline.
      ) However, recent work indicates that a much higher cut-off is necessary to obtain a statistically significant change at an individual level. (
      • Strober L.B.
      • Bruce J.M.
      • Arnett P.A.
      • Alschuler K.N.
      • DeLuca J.
      • Chiaravalloti N.
      • Lebkuecher A.
      • Di Benedetto M.
      • Cozart J.
      • Thelen J.
      • Cadden M.
      • Guty E.
      • Román C.A.F.
      A much needed metric: defining reliable and statistically meaningful change of the oral version symbol digit modalities test (SDMT).
      ,
      • Weinstock Z.
      • Morrow S.
      • Conway D.
      • Fuchs T.
      • Wojcik C.
      • Unverdi M.
      • Zivadinov R.
      • Weinstock-Guttman B.
      • Iverson G.L.
      • Dwyer M.
      • Benedict R.H.B.
      Interpreting change on the symbol digit modalities test in people with relapsing multiple sclerosis using the reliable change methodology.
      ) Using a cut-off for clinically significant change of 8 points, 2 (6%) patients worsened on SDMT, 25 (78%) did not change, and 5 (16%) improved. A follow-up time of 2 years is short in terms of recording progression. More patients improved than worsened over the 2 years. This is possibly explained by repeated testing even though different versions of the SDMT were applied and that there were approximately 48 weeks between testing. (
      • Fuchs T.A.
      • Gillies J.
      • Jaworski M.G.
      • Wilding G.E.
      • Youngs M.
      • Weinstock-Guttman B.
      • Benedict R.H.
      Repeated forms, testing intervals, and SDMT performance in a large multiple sclerosis dataset.
      )
      We found no group differences or significant changes in serum NFL levels in the randomized or open-label phase, despite previous reports of lower levels of NFL in CSF and serum in relapsing-remitting MS patients treated with dimethyl fumarate. (
      • Kuhle J.
      • Kropshofer H.
      • Haering D.A.
      • Kundu U.
      • Meinert R.
      • Barro C.
      • Dahlke F.
      • Tomic D.
      • Leppert D.
      • Kappos L.
      Blood neurofilament light chain as a biomarker of MS disease activity and treatment response.
      ,
      • Sejbaek T.
      • Nielsen H.H.
      • Penner N.
      • Plavina T.
      • Mendoza J.P.
      • Martin N.A.
      • Elkjaer M.L.
      • Ravnborg M.H.
      • Illes Z.
      Dimethyl fumarate decreases neurofilament light chain in CSF and blood of treatment naïve relapsing MS patients.
      ) However, although CSF levels of NFL were significantly increased compared with controls, serum NFL levels were mainly within the normal range, with only 12% of patients having a serum NFL ratio above 1.0 at screening. Nevertheless, the patients had clear evidence of intrathecal inflammation, indicated by increased CSF concentrations of a wide range of biomarkers of inflammation. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ,
      • Talbot J.
      • Chow H.H.
      • Mahler M.
      • Buhelt S.
      • Hansen R.H.
      • Lundell H.
      • Vinther-Jensen T.
      • Hellem M.N.N.
      • Nielsen J.E.
      • Siebner H.R.
      • von Essen M.R.
      • Sellebjerg F.
      Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis.
      )
      The significant results regarding CGM on MRI in the group treated with dimethyl fumarate in both study phases are all explained by a bidirectional change in the two periods, and not by a comparable change in the group initially treated with placebo. This finding is most likely an incidental finding, which would not have persisted after a correction for multiple comparisons, including all MRI metrics of interest. Interestingly, we observed an apparent reduction in new and enlarging lesions going from placebo to treatment. Unfortunately, we could not perform statistical analysis on new or enlarging lesions because this occurred in only a few patients. This difference was not observed in our report from the randomized phase of the trial, in which a manual segmentation of lesions was applied. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      )
      Adverse event reports of flushing were fewer than in the randomized phase; however, this can be explained by roughly 50% of patients entering the open-label phase being habituated to the treatment. The fewer cases of grade 2 and 3 lymphopenia are partially explained by the exclusion of patients with prolonged lymphopenia in the randomized phase, before entering the open-label phase. However, we still found an increased frequency of lymphopenia grade 3 compared with the ENDORSE follow-up study, possibly explained by higher age in our cohort compared with the ENDORSE cohort. (
      • Gold R.
      • Arnold D.L.
      • Bar-Or A.
      • Hutchinson M.
      • Kappos L.
      • Havrdova E.
      • Macmanus D.G.
      • Yousry T.A.
      • Pozzilli C.
      • Selmaj K.
      • Sweetser M.T.
      • Zhang R.
      • Yang M.
      • Potts J.
      • Novas M.
      • Miller D.H.
      • Kurukulasuriya N.C.
      • Fox R.J.
      • Phillips T.J.
      Long-term effects of delayed-release dimethyl fumarate in multiple sclerosis: interim analysis of ENDORSE, a randomized extension study.
      ,
      • Morales F.S.
      • Koralnik I.J.
      • Gautam S.
      • Samaan S.
      • Sloane J.A.
      Risk factors for lymphopenia in patients with relapsing–remitting multiple sclerosis treated with dimethyl fumarate.
      ) There were five serious adverse events in the open-label phase. None were judged to be causally linked to the treatment. There was one case of basal cell carcinoma. However, this is the most common type of malignancy in humans and is unlikely to be caused by the treatment. (
      • Kim D.P.
      • Kus K.J.B.
      • Ruiz E.
      Basal cell carcinoma review.
      )
      This study carries limitations, especially in sample size. Only 33 patients had complete datasets at week 96, meaning that 39% did not finish the study. Participants who dropped out or were excluded were not evaluated at week 96. This loss to follow-up is a clear limitation since this may entail enrichment for responders and thereby skewing our results for improved versus worsened participants, especially since 5 were lost to follow-up for reasons such as difficulty with transport to the clinic or worries that the treatment worsened the MS symptoms. Therefore, the study may have lost patients due to a self-perceived adverse benefit-risk balance. However, the data set is highly uniform, having been collected by only two neurologists, two study nurses, and 1 neuropsychologist and additionally monitored by an independent GCP unit. The MRI protocol was validated, and all patients were scanned on the same 3 Tesla MRI scanner. Although progression rates were comparable to previous reports in progressive MS, several patients improved. Unfortunately, the follow-up period of 2 years is too short of establishing any conclusive results on this phenomenon.
      In conclusion, we show no evidence of an effect of dimethyl fumarate treatment in this PPMS cohort, despite previous findings of a high level of intrathecal inflammation. (
      • Højsgaard Chow H.
      • Talbot J.
      • Lundell H.
      • Gøbel Madsen C.
      • Marstrand L.
      • Lange T.
      • Mahler M.R.
      • Buhelt S.
      • Holm Hansen R.
      • Blinkenberg M.
      • Romme Christensen J.
      • Soelberg Sørensen P.
      • Rode von Essen M.
      • Siebner H.R.
      • Sellebjerg F.
      Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
      ,
      • Talbot J.
      • Chow H.H.
      • Mahler M.
      • Buhelt S.
      • Hansen R.H.
      • Lundell H.
      • Vinther-Jensen T.
      • Hellem M.N.N.
      • Nielsen J.E.
      • Siebner H.R.
      • von Essen M.R.
      • Sellebjerg F.
      Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis.
      ) Serum NFL concentrations remained stable over 96 weeks, irrespective of dimethyl fumarate treatment. There was an expected degree of progression accompanied by a certain degree of MRI dynamic. Yet, many patients improved to an extent even beyond that found in the ASCEND treatment arm. This finding is very interesting and warrants further investigation.

      Funding

      This study was funded by a grant from Biogen (Cambridge, MA, USA) and grants from the Danish Multiple Sclerosis Society (A33491, A35741, and A38444). Biogen also supplied study drug and placebo free of charge.
      Hartwig R. Siebner holds a 5-year professorship in precision medicine at the Faculty of Health and Medical Sciences, University of Copenhagen which is sponsored by the Lundbeck Foundation (grant no. R186-2015-2138). Finn Sellebjerg holds a professorship in neurology at the Faculty of Health and Medical Sciences, University of Copenhagen which is sponsored by the Danish Multiple Sclerosis Society. Henrik Lundell has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 804746).

      Conflicts of interests

      H. Højsgaard Chow reports non-financial support from Merck, non-financial support from Teva, non-financial support from Biogen, non-financial support from Roche, outside the submitted work.
      J. Talbot reports non-financial support from Biogen and Sanofi Genzyme, outside the submitted work.
      H. Lundell has a patent for performing diffusion weighted magnetic resonance measurements on a sample pending to RWI AB.
      L. Marstrand reports grants from Novartis, personal fees from Biogen, outside the submitted work
      C. Gøbel Madsen, H.B. Søndergaard and M.B. Hansen have nothing to disclose.
      P. S. Sørensen has received personal compensation for serving on scientific advisory boards, steering committees, independent data monitoring committees or have received honoraria as speaker from Biogen, Merck, Novartis, TEVA, GlaxoSmithKline, SanofiAventis/Genzyme, and BMS/Celgene.
      Hartwig R. Siebner has received honoraria as speaker from Sanofi Genzyme, Denmark, Lundbeck AS, Denmark, and Novartis, Denmark, as consultant from Sanofi Genzyme, Denmark, Lophora, Denmark, and Lundbeck AS, Denmark, and as editor-in-chief (Neuroimage Clinical) and senior editor (NeuroImage) from Elsevier Publishers, Amsterdam, The Netherlands. He has received royalties as book editor from Springer Publishers, Stuttgart, Germany and from Gyldendal Publishers, Copenhagen, Denmark.
      Finn Sellebjerg reports grants from Biogen, grants from Danish Multiple Sclerosis Society, during the conduct of the study; grants and personal fees from Biogen, personal fees from Lundbeck, grants and personal fees from Merck, grants and personal fees from Novartis, grants and personal fees from Roche, grants and personal fees from Sanofi Genzyme, outside the submitted work; and is section editor on Multiple Sclerosis and Related Disorders.

      CRediT authorship contribution statement

      Helene Højsgaard Chow: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Resources, Visualization, Writing – original draft. Jacob Talbot: Conceptualization, Data curation, Investigation, Methodology, Project administration, Resources, Validation, Writing – review & editing. Henrik Lundell: Data curation, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Writing – review & editing. Lisbet Marstrand: Data curation, Investigation, Methodology, Writing – review & editing. Camilla Gøbel Madsen: Data curation, Investigation, Methodology, Writing – review & editing. Helle Bach Søndergaard: Data curation, Investigation, Methodology, Validation, Writing – review & editing. Malene Bredahl Hansen: Data curation, Investigation, Methodology, Validation, Writing – review & editing. Per Solberg Sørensen: Conceptualization, Formal analysis, Investigation, Methodology, Supervision, Writing – review & editing. Hartwig Roman Siebner: Investigation, Methodology, Project administration, Resources, Supervision, Writing – review & editing. Finn Sellebjerg: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Supervision, Writing – review & editing.

      Acknowledgements

      We wish to pay a special thanks to the study nurses Sidsel Walter Nielsen and Karina Jørgensen for their excellent assistance and meticulous work on the FUMAPMS study. We likewise thank the staff at our laboratory for producing high quality assays and owe a special thanks to Ulla Abildtrup, Lisbeth Egelykke Stolpe and Birgit Højsgaard Kassow for their thorough handling and analyses of samples. In addition, we wish to thank MRI technician Sussi Larsen for her through work on planning and executing all MRI scans, and Nina Reislev for assisting in setting up the MR analyses.

      Appendix. Supplementary materials

      References

        • Cadavid D.
        • Cohen J.A.
        • Freedman M.S.
        • Goldman M.D.
        • Hartung H.P.
        • Havrdova E.
        • Jeffery D.
        • Kapoor R.
        • Miller A.
        • Sellebjerg F.
        • Kinch D.
        • Lee S.
        • Shang S.
        • Mikol D.
        The EDSS-Plus, an improved endpoint for disability progression in secondary progressive multiple sclerosis.
        Mult. Scler. 2017; 23: 94https://doi.org/10.1177/1352458516638941
        • Delcoigne B.
        • Manouchehrinia A.
        • Barro C.
        • Benkert P.
        • Michalak Z.
        • Kappos L.
        • Leppert D.
        • Tsai J.A.
        • Plavina T.
        • Kieseier B.C.
        • Lycke J.
        • Alfredsson L.
        • Kockum I.
        • Kuhle J.
        • Olsson T.
        • Piehl F.
        Blood neurofilament light levels segregate treatment effects in multiple sclerosis.
        Neurology. 2020; 94: e1201https://doi.org/10.1212/WNL.0000000000009097
      1. G. Montes Diaz, R. Hupperts, J. Fraussen, and V. Somers, Dimethyl fumarate treatment in multiple sclerosis: recent advances in clinical and immunological studies, Autoimmun. Rev.. doi: 10.1016/j.autrev.2018.07.001.

        • Fox R.J.
        • Miller D.H.
        • Phillips J.T.
        • Hutchinson M.
        • Havrdova E.
        • Kita M.
        • Yang M.
        • Raghupathi K.
        • Novas M.
        • Sweetser M.T.
        • Viglietta V.
        • Dawson K.T.
        Placebo-controlled phase 3 study of Oral BG-12 or glatiramer in multiple sclerosis.
        N. Engl. J. Med. 2012; 367: 1087https://doi.org/10.1056/NEJMoa1206328
        • Fuchs T.A.
        • Gillies J.
        • Jaworski M.G.
        • Wilding G.E.
        • Youngs M.
        • Weinstock-Guttman B.
        • Benedict R.H.
        Repeated forms, testing intervals, and SDMT performance in a large multiple sclerosis dataset.
        Mult. Scler. Relat. Disord. 2022; 68104375https://doi.org/10.1016/J.MSARD.2022.104375
      2. A. Gajofatto, M. Turatti, and M. D. Benedetti, Primary progressive multiple sclerosis: current therapeutic strategies and future perspectives, Expert Rev. Neurotherap.. doi: 10.1080/14737175.2017.1257385.

        • Giovannoni G.
        • Steiner D.
        • Sellebjerg F.
        • Cohan S.
        • Jeffery D.
        • Rog D.
        • Chen Y.
        • Dong Q.
        • Ho P.-R.
        • Campbell N.
        • Cadavid D.
        • Amarante D.
        Sustained disability improvement as assessed by a multicomponent endpoint in secondary progressive multiple sclerosis (SPMS) patients: a post hoc analysis from ASCEND (P5.359).
        Neurology. 2017; 88
        • Gold R.
        • Kappos L.
        • Arnold D.L.
        • Bar-Or A.
        • Giovannoni G.
        • Selmaj K.
        • Tornatore C.
        • Sweetser M.T.
        • Yang M.
        • Sheikh S.I.
        • Dawson K.T.
        Placebo-controlled phase 3 study of oral BG-12 for relapsing multiple sclerosis.
        N. Engl. J. Med. 2012; 367: 1098https://doi.org/10.1056/NEJMoa1114287
        • Gold R.
        • Arnold D.L.
        • Bar-Or A.
        • Hutchinson M.
        • Kappos L.
        • Havrdova E.
        • Macmanus D.G.
        • Yousry T.A.
        • Pozzilli C.
        • Selmaj K.
        • Sweetser M.T.
        • Zhang R.
        • Yang M.
        • Potts J.
        • Novas M.
        • Miller D.H.
        • Kurukulasuriya N.C.
        • Fox R.J.
        • Phillips T.J.
        Long-term effects of delayed-release dimethyl fumarate in multiple sclerosis: interim analysis of ENDORSE, a randomized extension study.
        Mult. Scler. 2017; 23: 253https://doi.org/10.1177/1352458516649037
        • Højsgaard Chow H.
        • Talbot J.
        • Lundell H.
        • Gøbel Madsen C.
        • Marstrand L.
        • Lange T.
        • Mahler M.R.
        • Buhelt S.
        • Holm Hansen R.
        • Blinkenberg M.
        • Romme Christensen J.
        • Soelberg Sørensen P.
        • Rode von Essen M.
        • Siebner H.R.
        • Sellebjerg F.
        Dimethyl fumarate treatment in patients with primary progressive multiple sclerosis: a randomized, controlled trial.
        Neurol. Neuroimmunol. Neuroinflammation. 2021; 8https://doi.org/10.1212/NXI.0000000000001037
        • Hemmer B.
        • Kerschensteiner M.
        • Korn T.
        role of the innate and adaptive immune responses in the course of multiple Sclerosis.
        Lancet. Neurol. 2015; 14: 406https://doi.org/10.1016/S1474-4422(14)70305-9
        • Hviid C.V.B.
        • Knudsen C.S.
        • Parkner T.
        Reference interval and preanalytical properties of serum neurofilament light chain in scandinavian adults.
        Scand. J. Clin. Lab. Invest. 2020; 80: 291https://doi.org/10.1080/00365513.2020.1730434
        • Kapoor R.
        • Ho P.R.
        • Campbell N.
        • Chang I.
        • Deykin A.
        • Forrestal F.
        • Lucas N.
        • Yu B.
        • Arnold D.L.
        • Freedman M.S.
        • Goldman M.D.
        • Hartung H.P.
        • Havrdová E.K.
        • Jeffery D.
        • Miller A.
        • Sellebjerg F.
        • Cadavid D.
        • Mikol D.
        • Steiner D.
        • Bartholomé E.
        • D'Hooghe M.
        • Pandolfo M.
        • Van Wijmeersch B.
        • Bhan V.
        • Blevins G.
        • Brunet D.
        • Devonshire V.
        • Duquette P.
        • Freedman M.
        • Grand'Maison F.
        • Jacques F.
        • Lapierre Y.
        • Lee L.
        • Morrow S.
        • Yeung M.
        • Dufek M.
        • Havrdová E.K.
        • Kanovsky P.
        • Stetkarova I.
        • Talabova M.
        • Frederiksen J.
        • Kant M.
        • Petersen T.
        • Ravnborg M.
        • Sellebjerg F.
        • Airas L.
        • Elovaara I.
        • Eralinna J.P.
        • Sarasoja T.
        • Al Khedr A.
        • Brassat D.
        • Brochet B.
        • Camu W.
        • Debouverie M.
        • Laplaud D.
        • Lebrun Frenay C.
        • Pelletier J.
        • Vermersch P.
        • Vukusi S.
        • Baum K.
        • Berthele A.
        • Faiss J.
        • Flachenecker P.
        • Hohlfeld R.
        • Krumbholz M.
        • Lassek C.
        • Maeurer M.
        • Meuth S.
        • Ziemssen T.
        • Hardiman O.
        • McGuigan C.
        • Achiron A.
        • Karussis D.
        • Bergamaschi R.
        • Morra V.B.
        • Comi G.
        • Cottone S.
        • Grimaldi L.
        • Mancardi G.L.
        • Massacesi L.
        • Nocentini U.
        • Salvetti M.
        • Scarpini E.
        • Sola P.
        • Tedeschi G.
        • Trojano M.
        • Zaffaroni M.
        • Frequin S.
        • Hupperts R.
        • Killestein J.
        • Schrijver H.
        • Van Dijl R.
        • van Munster E.
        • Czarnecki M.
        • Drozdowski W.
        • Fryze W.
        • Hertmanowska H.
        • Ilkowski J.
        • Kaminska A.
        • Klodowska-Duda G.
        • Maciejowski M.
        • Motta E.
        • Podemski R.
        • Potemkowski A.
        • Rog T.
        • Selmaj K.
        • Stelmasiak Z.
        • Stepien A.
        • Tutaj A.
        • Zaborski J.
        • Boyko A.
        • Chefranova Z.
        • Evdoshenko E.
        • Khabirov F.
        • Sivertseva S.
        • Yakupov E.
        • Alvarez Cermeño J.C.
        • Escartin A.
        • Fernandez O.F.
        • Garcia-Merino A.
        • Hernandez Perez M.A.
        • Ayuso G.I.
        • Lallana J.M.
        • Gairin X.M.
        • Oreja-Guevara C.
        • Saiz Hinarejos A.
        • Gunnarsson M.
        • Lycke J.
        • Martin C.
        • Piehl F.
        • Roshanisefat H.
        • Sundstrom P.
        • Duddy M.
        • Gran B.
        • Harrower T.
        • Hobart J.
        • Kapoor R.
        • Lee M.
        • Mattison P.
        • Nicholas R.
        • Pearson O.
        • Rashid W.
        • Rog D.
        • Sharrack B.
        • Silber E.
        • Turner B.
        • Williams A.
        • Woolmore J.
        • Young C.
        • Bandari D.
        • Berger J.
        • Camac A.
        • Cohan S.
        • Conway J.
        • Edwards K.
        • Fabian M.
        • Florin J.
        • Freedman S.
        • Garwacki D.
        • Goldman M.
        • Harrison D.
        • Herrman C.
        • Huang D.
        • Javed A.
        • Jeffery D.
        • Kamin S.
        • Katsamakis G.
        • Khatri B.
        • Langer-Gould A.
        • Lynch S.
        • Mattson D.
        • Miller T.
        • Miravalle A.
        • Moses H.
        • Muley S.
        • Napier J.
        • Nielsen A.
        • Pachner A.
        • Pardo G.
        • Picone M.A.
        • Robertson D.
        • Royal W.
        • Sheppard C.
        • Thrower B.
        • Twyman C.
        • Waubant E.
        • Wendt J.
        • Yadav V.
        • Zabad R.
        • Zarelli G.
        Effect of natalizumab on disease progression in secondary progressive multiple sclerosis (ASCEND): a phase 3, randomised, double-blind, placebo-controlled trial with an open-label extension.
        Lancet. Neurol. 2018; 17: 405https://doi.org/10.1016/S1474-4422(18)30069-3
        • Kapoor R.
        • Smith K.E.
        • Allegretta M.
        • Arnold D.L.
        • Carroll W.
        • Comabella M.
        • Furlan R.
        • Harp C.
        • Kuhle J.
        • Leppert D.
        • Plavina T.
        • Sellebjerg F.
        • Sincock C.
        • Teunissen C.E.
        • Topalli I.
        • von Raison F.
        • Walker E.
        • Fox R.J.
        Serum neurofilament light as a biomarker in progressive multiple sclerosis.
        Neurology. 2020; 95: 436https://doi.org/10.1212/WNL.0000000000010346
        • Kim D.P.
        • Kus K.J.B.
        • Ruiz E.
        Basal cell carcinoma review.
        Hematol. Oncol. Clin. North Am. 2019; 33: 13https://doi.org/10.1016/J.HOC.2018.09.004
        • Kuhle J.
        • Barro C.
        • Andreasson U.
        • Derfuss T.
        • Lindberg R.
        • Sandelius Å.
        • Liman V.
        • Norgren N.
        • Blennow K.
        • Zetterberg H.
        Comparison of three analytical platforms for quantification of the neurofilament light chain in blood samples: ELISA, electrochemiluminescence immunoassay and simoa.
        Clin. Chem. Lab. Med. 2016; 54: 1655https://doi.org/10.1515/cclm-2015-1195
        • Kuhle J.
        • Kropshofer H.
        • Haering D.A.
        • Kundu U.
        • Meinert R.
        • Barro C.
        • Dahlke F.
        • Tomic D.
        • Leppert D.
        • Kappos L.
        Blood neurofilament light chain as a biomarker of MS disease activity and treatment response.
        Neurology. 2019; 92: E1007https://doi.org/10.1212/WNL.0000000000007032
      3. D. W. Langdon, M. P. Amato, J. Boringa, B. Brochet, F. Foley, S. Fredrikson, P. Hämäläinen, H. P. Hartung, L. Krupp, I. K. Penner, A. T. Reder, and R. H. B. Benedict, Recommendations for a brief international cognitive assessment for multiple sclerosis (BICAMS), Mult. Scler. J.. doi: 10.1177/1352458511431076.

        • Montalban X.
        • Hauser S.L.
        • Kappos L.
        • Arnold D.L.
        • Bar-Or A.
        • Comi G.
        • De Seze J.
        • Giovannoni G.
        • Hartung H.P.
        • Hemmer B.
        • Lublin F.
        • Rammohan K.W.
        • Selmaj K.
        • Traboulsee A.
        • Sauter A.
        • Masterman D.
        • Fontoura P.
        • Belachew S.
        • Garren H.
        • Mairon N.
        • Chin P.
        • Wolinsky J.S.
        Ocrelizumab versus placebo in primary progressive multiple sclerosis.
        N. Engl. J. Med. 2017; 376: 209https://doi.org/10.1056/NEJMoa1606468
        • Morales F.S.
        • Koralnik I.J.
        • Gautam S.
        • Samaan S.
        • Sloane J.A.
        Risk factors for lymphopenia in patients with relapsing–remitting multiple sclerosis treated with dimethyl fumarate.
        J. Neurol. 2020; 267: 125https://doi.org/10.1007/s00415-019-09557-w
        • Moreira Ferreira V.F.
        • Liu Y.
        • Healy B.C.
        • Stankiewicz J.M.
        Effectiveness and safety of dimethyl fumarate in progressive multiple sclerosis.
        Mult. Scler. J. 2021; 7https://doi.org/10.1177/20552173211010832
        • Morrow S.A.
        • Drake A.
        • Zivadinov R.
        • Munschauer F.
        • Weinstock-Guttman B.
        • Benedict R.H.B.
        Predicting loss of employment over three years in multiple sclerosis: clinically meaningful cognitive decline.
        Clin. Neuropsychol. 2010; 24: 1131https://doi.org/10.1080/13854046.2010.511272
        • Saraste M.
        • Bezukladova S.
        • Matilainen M.
        • Tuisku J.
        • Rissanen E.
        • Sucksdorff M.
        • Laaksonen S.
        • Vuorimaa A.
        • Kuhle J.
        • Leppert D.
        • Airas L.
        High serum neurofilament associates with diffuse white matter damage in MS.
        Neurol. Neuroimmunol. Neuroinflammation. 2021; 8https://doi.org/10.1212/NXI.0000000000000926
        • Schmidt P.
        • Gaser C.
        • Arsic M.
        • Buck D.
        • Förschler A.
        • Berthele A.
        • Hoshi M.
        • Ilg R.
        • Schmid V.J.
        • Zimmer C.
        • Hemmer B.
        • Mühlau M.
        An automated tool for detection of FLAIR-hyperintense white-matter lesions in multiple sclerosis.
        Neuroimage. 2012; 59: 3774https://doi.org/10.1016/J.NEUROIMAGE.2011.11.032
        • Schmidt P.
        • Pongratz V.
        • Küster P.
        • Meier D.
        • Wuerfel J.
        • Lukas C.
        • Bellenberg B.
        • Zipp F.
        • Groppa S.
        • Sämann P.G.
        • Weber F.
        • Gaser C.
        • Franke T.
        • Bussas M.
        • Kirschke J.
        • Zimmer C.
        • Hemmer B.
        • Mühlau M.
        Automated segmentation of changes in FLAIR-hyperintense white matter lesions in multiple sclerosis on serial magnetic resonance imaging.
        NeuroImage. Clin. 2019; 23https://doi.org/10.1016/J.NICL.2019.101849
        • Sejbaek T.
        • Nielsen H.H.
        • Penner N.
        • Plavina T.
        • Mendoza J.P.
        • Martin N.A.
        • Elkjaer M.L.
        • Ravnborg M.H.
        • Illes Z.
        Dimethyl fumarate decreases neurofilament light chain in CSF and blood of treatment naïve relapsing MS patients.
        J. Neurol. Neurosurg. Psychiatry. 2019; 90: 1324https://doi.org/10.1136/jnnp-2019-321321
        • Strassburger Krogias K.
        • Ellrichmann G.
        • Krogias C.
        • Altmeyer P.
        • Chan A.
        • Gold R.
        Fumarate treatment in progressive forms of multiple sclerosis: first results of a single-center observational study.
        Ther. Adv. Neurol. Disord. 2014; 7: 232https://doi.org/10.1177/1756285614544466
        • Strober L.B.
        • Bruce J.M.
        • Arnett P.A.
        • Alschuler K.N.
        • DeLuca J.
        • Chiaravalloti N.
        • Lebkuecher A.
        • Di Benedetto M.
        • Cozart J.
        • Thelen J.
        • Cadden M.
        • Guty E.
        • Román C.A.F.
        A much needed metric: defining reliable and statistically meaningful change of the oral version symbol digit modalities test (SDMT).
        Mult. Scler. Relat. Disord. 2022; 57103405https://doi.org/10.1016/J.MSARD.2021.103405
        • Talbot J.
        • Højsgaard Chow H.
        • Holm Hansen R.
        • von Essen M.R.
        • Sellebjerg F.
        Immunological effects of dimethyl fumarate treatment in blood and CSF of patients with primary progressive MS.
        J. Neuroimmunol. 2021; 361https://doi.org/10.1016/J.JNEUROIM.2021.577756
        • Talbot J.
        • Chow H.H.
        • Mahler M.
        • Buhelt S.
        • Hansen R.H.
        • Lundell H.
        • Vinther-Jensen T.
        • Hellem M.N.N.
        • Nielsen J.E.
        • Siebner H.R.
        • von Essen M.R.
        • Sellebjerg F.
        Relationship between cerebrospinal fluid biomarkers of inflammation and tissue damage in primary progressive multiple sclerosis.
        Mult. Scler. Relat. Disord. 2022; 104209https://doi.org/10.1016/J.MSARD.2022.104209
        • Weinstock Z.
        • Morrow S.
        • Conway D.
        • Fuchs T.
        • Wojcik C.
        • Unverdi M.
        • Zivadinov R.
        • Weinstock-Guttman B.
        • Iverson G.L.
        • Dwyer M.
        • Benedict R.H.B.
        Interpreting change on the symbol digit modalities test in people with relapsing multiple sclerosis using the reliable change methodology.
        Mult. Scler. 2022; 28: 1101https://doi.org/10.1177/13524585211049397
        • Wolinsky J.S.
        • Arnold D.L.
        • Brochet B.
        • Hartung H.P.
        • Montalban X.
        • Naismith R.T.
        • Manfrini M.
        • Overell J.
        • Koendgen H.
        • Sauter A.
        • Bennett I.
        • Hubeaux S.
        • Kappos L.
        • Hauser S.L.
        Long-term follow-up from the ORATORIO trial of ocrelizumab for primary progressive multiple sclerosis: a post-hoc analysis from the ongoing open-label extension of the randomised, placebo-controlled, phase 3 trial.
        Lancet Neurol. 2020; 19: 998https://doi.org/10.1016/S1474-4422(20)30342-2