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Incidence of persistent lymphopenia in people with multiple sclerosis on dimethyl fumarate
Callum H Wood1, Neil P Robertson2, Zin Min Htet2
1School of Medicine, Cardiff University, Heath Park Campus, Cardiff, UK.
Background:
Dimethyl fumarate (DMF) is a disease modifying therapy (DMT) used in the management of Multiple Sclerosis (MS). Lymphopenia occurs in approximately 30% of people receiving this medication. The recently revised Summary of Product Characteristics (SPC) recommends increased monitoring or cessation of this medication in the context of persistent lymphopenia, because of an increased risk of progressive multifocal leukoencephalopathy (PML). It is therefore important for clinicians and patients to be aware of the frequency of persistent, moderate-severe lymphopenia in order to make informed decisions regarding drug choice and safety monitoring.
Methods:
We reviewed medical records of 156 people with MS (PwMS) started on DMF between 2014 and 2020, who received at least 6 months of treatment, in order to identify the incidence and duration of persistent lymphopenia.
Result:
Ten were excluded due to missing data. In 146 patients, treated for 30.7 months (mean), 16 (11%) were found to experience persistent moderate lymphopenia (0.5-0.7 × 109/L) and 5 (3%) experienced persistent severe lymphopenia (<0.5 × 109/L). Of the 5 patients with persistent severe lymphopenia, 3 discontinued DMF. Two cases stopped directly due to SPC recommendations and after 6-months no further DMTs were initiated. Treatment was withdrawn in a further case due to lack of efficacy. Two cases remained on DMF as their persistent severe lymphopenia predated SPC revision. Mean times to persistent moderate and severe lymphopenia were 10.6 months and 25.5 months respectively. Increased age was a predictor for persistent lymphopenia (B = 0.071, p = 0.004) while sex, and previous DMT were not.
Insights
Persistent lymphopenia affects 14% of patients on dimethyl fumarate (DMF) for Multiple Sclerosis (MS). Increased age is a risk factor, highlighting the need for careful monitoring of this disease-modifying therapy.
Area of Science:
- Neurology
- Immunology
- Pharmacology
Background:
- Dimethyl fumarate (DMF) is a key disease-modifying therapy (DMT) for Multiple Sclerosis (MS).
- Lymphopenia, a decrease in lymphocyte count, affects approximately 30% of patients on DMF.
- Revised guidelines recommend monitoring or stopping DMF due to increased PML risk in persistent lymphopenia.
Purpose of the Study:
- To determine the incidence and duration of persistent moderate-to-severe lymphopenia in MS patients treated with DMF.
- To inform clinical decision-making regarding DMF use and safety monitoring.
Main Methods:
- Retrospective review of medical records for 146 MS patients treated with DMF for at least 6 months (2014-2020).
- Analysis of lymphocyte counts to identify persistent moderate (0.5-0.7 x 10^9/L) and severe (<0.5 x 10^9/L) lymphopenia.
- Identification of predictors for persistent lymphopenia.
Main Results:
- 11% (16/146) of patients developed persistent moderate lymphopenia, and 3% (5/146) developed persistent severe lymphopenia.
- Mean time to persistent moderate lymphopenia was 10.6 months; for severe lymphopenia, it was 25.5 months.
- Increased age was a significant predictor of persistent lymphopenia (p=0.004); sex and prior DMT use were not.
Conclusions:
- Persistent lymphopenia is a notable side effect of DMF treatment in MS patients.
- The findings underscore the importance of monitoring lymphocyte counts, especially in older patients.
- Clinical management decisions, including DMF cessation, should consider the risk of persistent lymphopenia and updated safety guidelines.
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