Antitumor activity of TNF-α after intratumoral injection using an in situ thermosensitive hydrogel

Local drug delivery strategies based on nanoparticles, gels, polymeric films, rods and wafers are increasingly used in cancer chemotherapy in order to enhance therapeutic effect and reduce systemic toxicity. Herein, a biodegradable and biocompatible in situ thermosensitive hydrogel was designed and employed to deliver tumor necrosis factor-α (TNF-α) locally by intratumoral injection. The triblock copolymer was synthesized by ring-opening polymerization (ROP) of β-butyrolactone (β-BL) and lactide (LA) in bulk using polyethylene glycol (PEG) as an initiator and Sn(Oct)2 as the catalyst, the polymer was characterized by NMR, gel permeation chromatography and differential scanning calorimetry. Blood and tumor pharmacokinetics and in vivo antitumor activity of TNF-α after intratumoral administration in hydrogel or solution with the same dose were evaluated on S180 tumor-bearing mice. Compared with TNF-α solution, TNF-α hydrogel exhibited a longer T1/2 (4-fold) and higher AUCtumor (19-fold), but Cmax was lower (0.5-fold), which means that the hydrogel formulation improved the efficacy with a lower systhemic exposure than the solution formation. In addition, TNF-α hydrogel improved the antitumor activity and survival due to lower systemic exposure than the solution. These results demonstrate that the in situ thermosensitive hydrogel-based local delivery system by intratumoral injection is well suited for the administration of TNF-α.