HORIZON (OP-106; NCT02963493), a pivotal, single-arm, multicenter Phase II study evaluating the efficacy and safety of melflufen in combination with dexamethasone, demonstrated efficacy and a manageable safety profile for the doublet in patients with heavily pretreated and poor-risk relapsed/refractory multiple myeloma refractory to pomalidomide and/or an anti-CD38 monoclonal antibody in an interim analysis (data cutoff date 1 October 2019) (Table 3 and Table 4) [56]. This evidence concerns the gene CD38 and plasma cell myeloma.