A novel aryl-guanidinium derivative, VP79s, targets the signal transducer and activator of transcription 3 signaling pathway, downregulates myeloid cell leukaemia-1 and exhibits preclinical activity against multiple myeloma

•IL-6/JAK/STAT3 cell signaling pathway is a promising target in multiple myeloma.•VP79s rapidly downregulates IL-6 receptor expression and STAT3 activation.•VP79s inhibits the expression of STAT3 target genes, including MCL1.•VP79s selectively induces apoptosis in myeloma cell lines and patient samples.•VP79s enhances bortezomib activity and inhibits induced drug resistance.