Rash developing after cessation of Daclizumab for relapsing remitting MS; a case series.

Daclizumab, a monoclonal antibody directed against CD25, a subunit of the high-affinity IL-2 receptor, was licensed as a disease modifying therapy (DMT) for relapsing remitting multiple sclerosis in 2017. Interference with IL-2 signalling is hypothesised to modulate T cell function. For example it results in a preferential shift of innate lymphoid cell (ILC) into CD56bright natural killer cells and a decrease in regulatory T Cells. We present three patients who developed urticarial papulovesicular rashes at a median of 3 months after discontinuation of Daclizumab. We propose an unexpected T cell mediated immune reaction as the cause.