Rituximab hypersensitivity reactions and tolerance of ofatumumab therapy.

B-cell depleting agents play a key role in a variety of disease entities. Rituximab, a murine-human chimeric anti-CD20 monoclonal antibody, as one of these major agents, has been associated with hypersensitivity reactions, which not only include the classic hypersensitivity ranging from immediate (type 1) to delayed (type IV), but also infusion-related reactions (IRRs). Whilst these typical hypersensitivity reactions occur in the setting of prior exposure, IRRs may occur in first exposure. Factors to consider include chimeric composition of agent, for example, rituximab with murine component, which may be responsible for such hypersensitivity reactions. In these individuals, alternate anti-CD20, such as oftatumumab, a fully human monoclonal antibody may be used. We report three cases of rituximab hypersensitivity in patients with auto-immune disease, and in whom ofatumumab therapy was given and subsequently tolerated.