“Given its favorable cost-effectiveness profile, [rituximab] remains a valuable treatment option in the current landscape of MS treatments, even at the reduced dose,” wrote Giulio Disanto, MD, PhD, of the Neurocenter of Southern Switzerland in Lugano, and coauthors. The study was published in Multiple Sclerosis Journal.
To determine the clinical and radiologic effectiveness of deescalating rituximab dosage – along with assessing any adverse outcomes – this observational, single-center study examined 59 patients with MS who had been treated with rituximab at 1,000 mg for at least 1 year before the study began. Roughly 63% (n = 37) of the patients had relapsing remitting MS (RRMS), while the rest (n = 22) had secondary progressive disease (SPD). Their median age was 51, and nearly 75% were women.
All patients underwent neurologic examinations at baseline and then every 3 months for 1 year, with new symptoms, infections, or adverse events being assessed via the Expanded Disability Status Scale (EDSS). They also underwent brain and spinal MRI at baseline and at 12 months while blood samples were taken at baseline and then every 3 months for 1 year, with previous data for both collected when available.
Study results
All 59 patients completed 12-month follow-up, and no relapses occurred in the year after lowering rituximab dosage to 500 mg. No significant differences were observed when comparing EDSS scores at the start of the 1,000-mg dose with the start of the 500-mg dose (Wilcoxon P = .131) as well as from the start of the 500-mg dose to the end of follow-up (Wilcoxon P = .284). Analyzing RRMS and SPD patients separately also led to no differences in EDSS scores from the start of the 500-mg dose to the end of follow-up (Wilcoxon P = .531; Wilcoxon P = .408).
During the 1,000-mg treatment period the number of patients who developed at least one new T2 lesion on their brain or spine was 9 and 4, respectively. During the 500-mg period, just one patient developed a new T2 brain lesion and two patients developed new T2 spine lesions. IgG and IgM levels did not change from the start of 500-mg treatment, although total dose of rituximab was inversely associated with IgG concentrations when previous treatment with 1,000 mg was factored in (coefficient, −0.439; P = 0.041).
A total of 33 patients reported at least one adverse event during the 500-mg treatment period, with only three events being classified as serious: one pancreatitis, one coronary stenting, and one neutropenia.
Validating clinical experience
“This randomized trial is an important step,” said Timothy Vollmer, MD, of the Rocky Mountain MS Center in Westminster, Colo., in an interview. “It clearly supports that you can lessen the dose, which will allow us to use this revolutionary drug for a longer period of time in patients.”
Dr. Vollmer noted that, at his center, they have been using 500 mg of rituximab over a 6-month period since 2010 without a formal clinical trial and with no notable difference in adverse outcomes on MRIs or disability scales. “This validates what we’ve been doing, which we appreciate,” he said.
“The next thing you have to do is determine whether you really have to give it every 6 months,” he added, “because the treatment effect in most patients will last, in terms of B-cell depletion, about a year or more. What we should be testing next is giving the 500 mg and waiting until patients begin to recover B cells before we give them the next cycle, to see if that helps decrease the major side effect, which is a drop in IgG levels.”
The authors acknowledged their study’s limitations, including a moderate sample size, a short follow-up period after 500-mg dosage, and an inability to confirm consistency among 1,000-mg dose administration among all patients, which “may well influence efficacy and safety measures.”
The study was supported by the Neurocenter of Southern Switzerland. One author declared numerous potential conflicts of interest, including receiving speaker fees, research fees, and travel support, and serving on advisory boards for various foundations, universities, and pharmaceutical companies.
SOURCE: Disanto G et al. Mult Scler J. 2020 Aug 25. doi: 10.1177/1352458520952036.