Low-dose Rituximab May Be Effective in Preventing Relapses

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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A reduced dosage of rituximab maintenance therapy may be effective at preventing relapses among people with ANCA-associated vasculitis (AAV), a new study reports.

Specifically, the researchers said 500 mg infusions every six months “appear to be an effective and safe option” for maintaining AAV remission.

“This study provides real-world data to reiterate the effectiveness of [this] reduced rituximab dose,” the researchers wrote.

Published in Rheumatology Advances in Practice, the study is titled “Rituximab 500mg 6 monthly infusions is an option in maintenance therapy of ANCA associated vasculitis.”

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Rituximab is a medication that kills B-cells, a type of immune cell that produces antibodies and is overactive in AAV. It is widely approved to treat granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), two types of AAV.

The medication is given by infusion, which is a slow injection into the bloodstream. However, the optimum dose and infusion schedule, in the context of AAV, isn’t definitively known. In fact, the reported dosages in the scientific literature have ranged from as high as 1,000 mg given every four months to as low as 500 mg given twice per year. In the U.K., the recommended dosage is either 1,000 or 500 mg, given every six months for two years.

Given the uncertainty in dosing, a team of researchers in the U.K. now sought to determine the effectiveness and safety of a reduced rituximab dose (500mg) given every six months. To that end, the team conducted a retrospective evaluation using data from 62 people with AAV who were treated with rituximab at the University Hospitals Birmingham NHS Foundation Trust between 2002 and 2020.

These patients were given one of four dosing schedules of rituximab. Regime A, which consisted of 2,000 mg of rituximab per year, was given to 16 individuals. A total of 21 patients — including eight who switched to this regime after two years or more on regime A — were given regime B, which involved 1,000 mg infusions every six months.

In regime C, which included 27 patients, rituximab was first given at 1,000 mg every six months, with the dosage then reduced to 500 mg every six months after a median of four of the higher-dose infusions. The final group, regime D, consisted of six patients given 500 mg rituximab every six months.

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Among the 16 patients in regime A, 14 experienced a total of 43 AAV relapses. By contrast, there were four relapses among the 27 participants on regime C, and no relapses reported for participants on regimes B or D.

Rates of infections were generally low for all regimens. The average rate of infections per year was highest among patients given regime A, at 0.47 infections per year, followed by 0.24 infections per year with regime D, and no infections in patients receiving regimens B or C. Yet, no patients on regime D reported a serious infection.

The rate of serious infections and of abnormally low antibody levels, called hypogammaglobulinemia, also were higher on regime A (50%), relative to the other dosages (19-17%).

The researchers noted that, since this is a retrospective study, it’s likely that some infections and other adverse events may have been missed because they were not reported to doctors and recorded in medical records.

“Although this is a small retrospective study, 500 mg 6 monthly infusions appear to be an effective and safe option in maintenance of remission in AAV, either following previous [1,000 mg] 6 monthly or 500 mg 6 monthly from start of maintenance rituximab therapy,” the team concluded.

They stressed a need for further research to confirm these observations and to establish the optimal dosage for rituximab in AAV.