5′-NucA-SMCC-DM1 and 5′-NucA-SPDMV-DM1 are Potent Aptamer–Drug Conjugates against Pancreatic Cancer

Pancreatic cancer is one of the most lethal cancers, characterized by low survival rates due to a complex tumor microenvironment, late-stage diagnosis and, notably, the limited effectiveness of current treatments. First-line therapies, such as gemcitabine and nab-paclitaxel, often lead to unexpected side effects. Mertansine, which is a more potent cytotoxic agent, faces similar challenges. In response, we designed and synthesized a highly water-soluble conjugate of an antinucleolin aptamer (NucA) and mertansine (NucA-DM1) to enhance the delivery of DM1 specifically to pancreatic tumor cells. Our <i>in vitro</i> studies demonstrated that the cytotoxic activity of this conjugate could retain potency compared to DM1 alone, with significant accumulation observed in pancreatic tumor cells rather than in normal cell lines. Additionally, 5'-NucA-SMCC-DM1 and 5'-NucA-SPDMV-DM1 conjugates exhibited excellent stability in serum. Notably, 3'-Cy5-5'-NucA-SMCC-DM1 was primarily taken up by PANC-1 cells through macropinocytosis. Further investigations into the antitumor activity and cell cycle dynamics indicated that the conjugation of NucA and DM1 minimally impacted the 5'-linked aptamer-drug conjugate (ApDC), whereas the 3'-linked ApDC remained unaffected. Our findings also confirmed that SMCC- and SPDMV-linked ApDCs retained stability in human serum for up to 48 h. Flow cytometry and confocal microscopy analyses further illustrated the excellent targeting capabilities of these conjugates in pancreatic cancer cell lines PANC-1 and MIA PaCa-2, in contrast to normal cells such as MIHA (normal human liver cells). Two candidates, 5'-NucA-SMCC-DM1 and 5'-NucA-SPDMV-DM1, were selected based on <i>in vitro</i> evaluations and exhibited potent antitumor efficacy with significantly decreased toxicity to the liver and heart compared with DM1 alone in xenografted mice.