Publications by authors named "Toorop A"

Background: Biomarkers of neuronal and axonal damage (serum neurofilament light (sNfL) and serum glial fibrillary acidic protein (sGFAP)) may provide insight into the aetiology of natalizumab wearing-off symptoms (WoSs).

Objectives: We investigated the longitudinal association between and predictive value of sNfL and sGFAP and the occurrence of WoS in MS patients treated with natalizumab.

Methods: We performed longitudinal measurements of sNfL and sGFAP in NEXT-MS trial participants who completed a questionnaire about WoS.

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Background: Several studies reported lower drug concentrations with subcutaneous natalizumab compared to intravenous natalizumab. With the emergence of extended interval dosing, gaining more insight into lower concentrations after subcutaneous administration is essential.

Methods: We compared serum trough concentrations between subcutaneous and intravenous administration within a matched cohort (n = 50).

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Background And Objectives: Wearing-off symptoms during natalizumab treatment in multiple sclerosis are characterized by an increase of MS-related symptoms prior to natalizumab administration. The influence of extended interval dosing (EID) on wearing-off symptoms are important to consider, as this might cause hesitancy in initiating or continuing EID.

Methods: Participants of the NEXT-MS trial, in which treatment intervals are adjusted based on drug concentrations, were divided into two groups: an extended group containing participants with at least one week of additional interval extension, and a group with a fixed interval during the trial (range 4-7 weeks).

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Background: Extended interval dosing (EID) of natalizumab treatment is increasingly used in multiple sclerosis. Besides the clear anti-inflammatory effect, natalizumab is considered to have neuroprotective properties as well.

Objectives: This study aimed to study the longitudinal effects of EID compared to standard interval dosing (SID) and natalizumab drug concentrations on brain atrophy.

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Background: Extended interval dosing (EID) of natalizumab is a promising strategy to optimise treatment in multiple sclerosis (MS). Personalised EID by therapeutic drug monitoring can enable further extension of treatment intervals.

Methods: The NEXT-MS trial is an investigator-initiated prospective phase IV non-randomised study.

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Background And Objectives: Although MRI-based markers of neuroinflammation have proven crucial for the diagnosis of multiple sclerosis (MS), predicting clinical progression with inflammation remains difficult. Neurodegenerative markers such as brain volume loss show stronger clinical (predictive) correlations, but also harbor age-related variation that must be disentangled from disease duration. In this study we investigated how clinical disability is related to volumetric MRI measures in a cohort of MS patients and healthy controls (HC) of the same age: Project Y.

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Background: The majority of patients with multiple sclerosis on ocrelizumab have B-cell depletion after standard interval dosing of 26 weeks. With B-cell-guided dosing patients receive their next dose when B-cell repopulation occurs. Prediction of B-cell repopulation using ocrelizumab concentrations could aid in personalising treatment regimes.

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Background: Natalizumab is effective in the treatment of multiple sclerosis (MS). In 2021, the European Medicines Agency approved the subcutaneous (SC) variant of natalizumab which can be used instead of intravenous administration. However, the course of drug levels varies between administration routes, and the Food and Drug Administration rejected the request for approval of natalizumab SC for reasons that were not disclosed.

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Article Synopsis
  • Recent approval of natalizumab for multiple sclerosis includes subcutaneous administration, leading to interest in personalized dosing methods.
  • A study was conducted on 30 patients to compare natalizumab levels in capillary blood (from fingerpricks) versus venous blood samples before IV administration.
  • Results showed that capillary and venous concentrations were similar, suggesting fingerprick testing is a viable option for monitoring drug levels and tailoring treatment.
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Ocrelizumab, an anti-CD20 monoclonal antibody, counteracts induction of humoral immune responses after severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccinations in patients with multiple sclerosis (MS). We aimed to assess if serum ocrelizumab concentration measured at the time of vaccination could predict the humoral response after SARS-CoV-2 vaccination. In 52 patients with MS, we found ocrelizumab concentration at the time of vaccination to be a good predictor for SARS-CoV-2 IgG anti-RBD titers after vaccination (comparable to B-cell count).

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Article Synopsis
  • Patients with relapsing-remitting multiple sclerosis (RRMS) often experience significant long-term neurodegeneration despite effective treatments.
  • The study evaluated the predictive value of serum neurofilament-light (sNfL) and serum contactin-1 (sCNTN1) in assessing neurodegeneration using MRI in RRMS patients treated with natalizumab over several years.
  • Results showed that sNfL levels after the first year of treatment were associated with brain atrophy metrics, while sCNTN1 levels did not demonstrate a clear predictive value.
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Background: Patients with multiple sclerosis (MS) who are treated with monoclonal antibodies frequently report an increase of MS-related symptoms prior to the next dose known as the wearing-off phenomenon. The objective of this study was to assess the prevalence and predicting factors of the wearing-off phenomenon in patients with MS using ocrelizumab.

Methods: This was a prospective cohort study in patients with MS receiving ocrelizumab ≥1 year.

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Over the past two decades, treatment options for patients with multiple sclerosis (MS) have increased exponentially. In the current therapeutic landscape, "no evidence of MS disease activity" is within reach in many of our patients. Minimizing risks of complications, improving treatment convenience, and decreasing health care costs are goals that are yet to be reached.

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In women with very active multiple sclerosis (MS), natalizumab can be continued during pregnancy to prevent rebound disease activity. Our aim was to evaluate changes in serum natalizumab trough concentrations during pregnancy. Blood samples of 3 patients were collected before, during, and after pregnancy.

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Objective: The objective of this study was to measure humoral responses after SARS-CoV-2 vaccination in MS patients treated with ocrelizumab (OCR) compared to MS patients without disease modifying therapies (DMTs) in relation to timing of vaccination and B-cell count.

Methods: OCR treated patients were divided into an early and a late group (cut-off time 12 weeks between infusion and first vaccination). Patients were vaccinated with mRNA-1273 (Moderna).

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In this observational study, 159 patients with multiple sclerosis received personalized dosing of ocrelizumab incentivized by the COVID-19 pandemic. Re-dosing was scheduled when CD19 B-cell count was ⩾10 cells/µL (starting 24 weeks after the previous dose, repeated 4-weekly). Median interval until re-dosing or last B-cell count was 34 [30-38] weeks.

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Ocrelizumab is often used as an alternative therapy in natalizumab-treated MS patients at risk for progressive multifocal leukoencephalopathy (PML). Our objective was to assess efficacy and safety of JC-virus positive patients switching (either directly or indirectly) from natalizumab to ocrelizumab. Forty-two patients were included from an observational cohort (median follow-up 21 months).

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There is not much awareness of varicella zoster virus (VZV) associated central nervous system (CNS) infections under treatment with natalizumab. Here we describe two natalizumab treated MS patients who developed acute retinal necrosis combined with CNS vasculitis caused by VZV. In natalizumab treated patients, visual symptoms atypical of optic neuritis should be promptly evaluated by an ophthalmologist.

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Objective: To describe the disease course of carryover progressive multifocal leukoencephalopathy (PML) after switching from natalizumab to ocrelizumab in 2 patients with relapsing-remitting MS.

Methods: Two case reports with 1 year of follow-up and retrospective longitudinal measurements of serum neurofilament light (NfL) levels and B-cells.

Results: PML was diagnosed 78 days (case 1) and 97 days (case 2) after discontinuation of natalizumab.

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Purpose: In previous studies, associations between breast-milk cortisol levels obtained on one occasion and infant neurodevelopment were demonstrated. However, more recent evidence indicates that breast-milk cortisol and cortisone concentrations follow the diurnal rhythm of maternal hypothalamus-pituitary-adrenal axis, peaking in the early morning and with a nadir at midnight. We studied associations between breast-milk glucocorticoid (GC) rhythmicity, and infant behavior and sleep.

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Context: The hypothalamus-pituitary-adrenal (HPA) axis displays a diurnal rhythm. However, little is known about its development in early life.

Objective: To describe HPA-axis activity and study possible influencing factors in 1-month-old infants.

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Objective: Glucocorticoids (GCs) in breastmilk have previously been associated with infant body growth and body composition. However, the diurnal rhythm of breastmilk GCs was not taken into account, and we therefore aimed to assess the associations between breastmilk GC rhythmicity at 1 month and growth and body composition at 3 months in infants.

Methods: At 1 month postpartum, breastmilk GCs were collected over a 24-h period and analyzed by LC-MS/MS.

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Steroid concentrations were studied in ovarian tissue obtained by means of unilateral ovariectomy during a 10-day period preceding first ovulation. Furthermore, the levels of progesterone were measured in this period in the serum of simultaneous intact control rats. Ovarian concentrations of testosterone and oestradiol were at about 70 and 15 fmol/mg ovary respectively from 10 to 4 days before first ovulation; they clearly increased to a maximum of 170 and 120 fmol/mg ovary during the last 1-3 days before first ovulation.

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The present study examined the ovarian progesterone levels in rats during the normal 5-day oestrous cycle and in rats with an experimentally induced delayed or advanced ovulation. Ovarian androgen and oestrogen concentrations were also studied in rats with an advanced ovulation. The ovarian progesterone concentrations during the normal cycle showed two peaks: one during metoestrus and dioestrus 1 and the second during the afternoon of pro-oestrus.

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