Tumor-specific targeting of a mitochondrial Kv1.3 channel inhibitor through conjugation to gastrin/cholecystokinin B receptor ligand strongly reduces pancreatic ductal adenocarcinoma in orthotopic models

Pancreatic ductal adenocarcinoma (PDAC) is a highly chemoresistant and immunoresistant tumor with an overall five-year survival rate of less than 10 %. Current treatments for PDAC are rather limited, highlighting the importance of finding novel strategies. In this study, we investigated a strategy for the tumor-specific targeting of PAPTP, a small molecule that reduces PDAC growth by inhibiting the mitochondrial potassium channel mtKv1.3, thereby inducing mitochondrial dysfunction and killing cancer cells. PAPTP was reversibly conjugated to three tumor-penetrating peptides: iRGD, VH434, and a short version of minigastrin (CCK2p). These recognize neuropilin-1 and integrin (iRGD), the low-density lipoprotein receptor (VH434), and the gastrin/cholecystokinin B receptor (CCK2p). In vivo pharmacokinetic studies revealed that the PAPTP-bound iRGD peptide underwent rapid metabolic cleavage, which prevented optimal uptake of the construct into PDAC. The VH434 conjugate was highly hemolytic. However, CCK2p-PAPTP exhibited preferential distribution to the pancreas in animals bearing orthotopic PDAC. Efficacy studies revealed a reduction in mean tumor volume of up to 65 % in two independent orthotopic mouse models, with no tumor evident in some of the animals treated with the CCK2p-bound PAPTP construct. Our data suggest that tumor-specific targeting of small molecules may be a promising strategy for precision medicine against PDAC.