In vitro cytotoxicity, in vivo biodistribution and antitumor activity of HPMA copolymer–5-fluorouracil conjugates

5-Fluorouracil (5-FU) is an antimetabolite with a broad-spectrum activity against solid tumors. However, its very short half-life in plasma circulation greatly limited the in vivo antitumor efficacy and clinical application. The current work aimed to solve this problem as well as to increase 5-FU biodistribution to tumor by covalently conjugating 5-FU to a biocompatible, non-toxic and non-immunogenic drug carrier – N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer. The in vitro cytotoxicity, in vivo biodistribution and therapeutic efficacy of HPMA copolymer–5-FU conjugates (P-FU) were reported. Cytotoxicity was evaluated by using a serial of tumor cells (A549, CT-26, Hela, HepG2 cells and 5-FU resistant HepG2 cells). In vivo biodistribution and therapeutic efficacy were investigated in Kunming mice-bearing hepatoma 22 (H22). Results indicated that P-FU could increase the cytotoxicity of 5-FU in Hela, HepG2 and 5-FU resistant HepG2 cells, while it decreases the cytotoxicity of 5-FU in A549 and CT-26. Both in vitro release profile in plasma and biodistribution study showed that P-FU significantly prolonged the drug plasma circulation time. P-FU also showed an over 3-fold larger area under the concentration–time curve (AUC) in tumor when compared with free drug. Therapeutic evaluation also demonstrated that the treatment with P-FU displayed stronger inhibition of the tumor growth when compared with that of control group (physiologic saline) or 5-FU group at the same dose. All the results suggested that P-FU could increase cytotoxicity of 5-FU in certain cancer cell lines, prolong 5-FU circulation time in vivo, enhance 5-FU distribution to tumor and improve therapeutic efficacy. Therefore, HPMA copolymer is a potential carrier for 5-FU for the effective treatment of cancer.