A Dual-Action CXCR4-Targeted Peptide−Drug Conjugate Engineered to Enhance Antitumor Efficacy and Mitigate Myelosuppression in Pancreatic Cancer

Abstract Gemcitabine (GEM) is a first-line therapeutic option for pancreatic cancer; however, it has low efficacy due to rapidly developed drug resistance and severe dose-limiting myelosuppression. To enhance its therapeutic effect, this study developed a novel peptide−drug conjugate using a CXCR4 antagonistic peptide as the targeting head and gemcitabine as the drug payload, based on the characteristics of pancreatic tumor cells highly expressing CXCR4 that mediates immunosuppression and tumor progression through interaction with its specific ligand CXCL12. The therapeutic effect of the conjugate (P12-GEM) was investigated using pancreatic ductal adenocarcinoma cell lines and an orthotopic pancreatic cancer mouse model. Its myelosuppressive effect was assessed from the perspective of hematological toxicity profiles. The results showed that P12-GEM maintained a cell-killing capability comparable to that of GEM while effectively inhibiting the phosphorylation of Erk and P38, thereby reducing CXCL12-mediated tumor cell migration and adhesion to stromal cells. In a tumor-bearing mouse model, P12-GEM demonstrated superior antitumor efficacy compared to GEM and significantly extended animal survival. Moreover, P12-GEM reduced the proportion of tumor-associated macrophages and increased the infiltration of CD8+ T cells in the tumor microenvironment without reducing platelet and white blood cell counts in the peripheral blood. In summary, P12-GEM possesses dual functions of CXCR4 antagonism and tumor cell killing, contributing to reversal of the immunosuppressive microenvironment and alleviation of myelotoxicity.