Clinicopathological definition, management and prognostic value of mogamulizumab‐associated rash and other cutaneous events: A systematic review

Mogamulizumab is a first-in-class IgG1k monoclonal antibody that selectively targets the chemokine receptor type 4. The drug has received Food and Drug administration authorisation for mycosis fungoides and Sezary syndrome following failure of at least one previous course of systemic therapy and now is available in Europe. One of the most common treatment-related side effects observed has been the mogamulizumab-associated rash (MAR), which affects up to a quarter of patients and is the most frequent adverse event leading to drug discontinuation. The aim of this study is to perform a systematic review of the literature on patients diagnosed with MAR and other mogamulizumab-related cutaneous events to describe the clinical and histological characteristics, the management in clinical practice and to assess whether these events have prognostic implications. In total, 2073 records were initially identified through a literature search, 843 of which were duplicates. After screening for eligibility and inclusion criteria, 49 articles reporting mogamulizumab-associated cutaneous events were included. Totally, 1516 patients were retrieved, with a slight male prevalence as for the available data (639 males and 570 females, i.e. 52.9% vs. 47.1%). Regarding the reported clinicopathological findings of the cutaneous reactions, the five most common patterns were spongiotic/psoriasiform dermatitis (22%), eruptions characterized by the presence of papules and/or plaques (16.1%), cutaneous granulomatosis (11.4%), morbilliform or erythrodermic dermatitis (9.4%) and photodermatitis (7.1%). Our results highlight how the majority of the reported cutaneous adverse events on mogamulizumab are of mild-to-moderate entity and generally manageable in clinical practice, though prompt recognition is essential and case-by-case assessment should be recommended. Future research will need to focus on the MAR prognostic implications and to identify genomic and molecular markers for a more rapid and accurate diagnosis.