The effective delivery of cytotoxic agents to the tumor cells is a key challenge in anticancer therapy. Multivalent integrinspecific ligands are considered a promising tool to increase the binding affinity, selectivity, and internalization efficiency of small molecule-drug conjugates. Here we report the synthesis and biological evaluation of a multimeric conjugate containing the high-affinity integrin alpha v beta 3 binding ligand RAFT- c (RGDfK) 4 , a lysosomally cleavable Val-Cit linker and cryptophycin-55 glycinate, a potent inhibitor of tubulin polymerization. In vitro cytotoxicity assays verified that the multimeric RGD-cryptophycin conjugate displays improved potency compared to the monomeric analogue in integrin alpha v beta 3 overexpressing tumor cell lines, while significantly reduced activity was observed in the integrin-negative cell line. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.