5-Fluorouracil-methotrexate conjugate enhances the efficacy of 5-fluorouracil in colorectal cancer therapy.

To extend the short half-life of fluorouracil (Fu), enhance its tumor targeting, improve efficacy, and reduce side effects, providing a new approach for colorectal cancer treatment. Fluorouracil was hydroxylated and conjugated with methotrexate to form a 5-fluorouracil-methotrexate conjugate (MF). This was complexed with sulfobutyl ether-β-cyclodextrin (MF-SEBCD) using a stirring method to create an injectable formulation. In vitro studies assessed the conversion of MF-SEBCD in plasma and its antitumor activity. In vivo studies examined antitumor activity, preliminary safety, pharmacokinetics, and tissue distribution. MF was synthesized with a 25% yield and purity above 95%. The water solubility of MF increased by 92-fold with MF-SEBCD preparation. In vitro, MF-SEBCD effectively converted into Fu in plasma and showed strong antitumor activity, with IC50 values of 0.51, 1.29, and 1.26 µM for MC38, HT29, and 4T1 cells, respectively. In vivo, MF-SEBCD achieved a tumor inhibition rate of 57.08%. Pharmacokinetic studies showed that MF-SEBCD extended Fu's half-life to 47 min, nearly double that of Fu injection. Tissue distribution analysis confirmed improved tumor targeting. MF-SEBCD effectively prolongs Fu's half-life, enhances tumor targeting, increases antitumor efficacy, and reduces side effects, offering a promising approach for colorectal cancer treatment.