To determine whether melflufen activity can be detected and differs in BM samples from MM patients, we evaluated the efficacy of melflufen and four additional drugs (melphalan, selinexor, bortezomib, and 4-hydroperoxycyclophosphamide) towards CD138+CD38+ plasma cells in 15 BM-MNC samples (NDMM = 6; RRMM = 9) obtained from 14 different MM patients (Online Supplementary Figure S14, Tables S1). Here, CD38 is linked to Miyoshi myopathy.