What can you tell me about Tecfidera depressing white blood cell counts? I am trying to decide between it and Copaxone and want to be informed.
Your white blood count or WBC includes many different cell types including neutrophils, monocytes, eosinophils and lymphocytes. All have different functions and loss of individual cell types can have different consequences. For instance, chemotherapies used to treat cancer can suppress neutrophil counts and make patients susceptible to bacterial and fungal infections. Suppressed lymphocyte counts have less predictable effects but when severe and prolonged, such as occurs in patients with HIV infection, can lead to unusual infections only seen in patients with suppression of normal immunity.
Tecfidera decreased mean lymphocyte counts by 30% in the phase III clinical trial that led to its approval by the FDA. This means the investigators compared the average of all the lymphocyte counts in all the patients on Tecfidera in the trial at each time point and compared this average number to those on placebo and the counts were 30% lower in the Tecfidera group. This does not mean that 30% of patients on Tecfidera experience a drop in lymphocyte counts. Overall this is considered a relatively mild and insignificant drop in lymphocyte counts. In fact the mean lymphocyte counts in patients on Tecfidera remained well above the lower limit of normal (lower limit of normal is a below a count of 900). Only 6% of patients experienced a drop in lymphocyte counts below 500 in the trial compared to 1% of patients on Placebo. This is reason that we need to monitor your lymphocyte count while taking Tecfidera; if your count remains below 500 on repeated testing over time and there is no other explanation (such as another medication or illness), then your physician may consider stopping the Tecfidera.
There was no evidence that patients on Tecfidera were more susceptible to infections as a result of this drop in lymphocyte counts during the study which lasted for 2 years, but there remains a concern that a prolonged drop in lymphocyte counts could lead to an increased risk of infections over years of treatment.
Other MS drugs that cause drops in lymphocyte counts include the interferons (Avonex, betaseron, Extavia and Rebif), Gilenya and Aubagio. The drops in lymphocyte counts are most dramatic with Gilenya (73% reduction in mean lymphocyte counts compared to placebo) but Gilenya has only been associated with a mild increased risk of respiratory tract infections and herpetic infections (e.g.. shingles) and this infection risk has not been necessarily linked to the reduction in lymphocyte count.
Rip Kinkel, MD