Evaluation of Trilysine-Cross-Linked Gellan Gum for Intratumoral Delivery of Anti-PD-1 in a Colorectal Cancer Mouse Tumor Model

Colorectal cancer (CRC) is the second leading cause of death in the United States in the adult population. When detected at early stages, the survival rate is higher than 70% but when diagnosed at a metastatic stage, the 5-year survival rate significantly declines to 15%. In recent years, immunotherapy has shown promising results in a selective patient population with advanced or metastatic CRC with microsatellite instability (MSI) and mismatch repair (MMR). Hydrogels are a growing field of research to improve the delivery of monoclonal antibodies. In this work, a gellan gum-based (GG) hydrogel noncovalently cross-linked using trilysine (TLA) was characterized for its drug release and diffusion properties. A partial release of the checkpoint inhibitor anti-programmed death-1 (aPD-1) was observed with an almost 40% cumulative release within the first 24 h. FRAP analysis showed varying diffusion rates (μm²/s) for Atto 488-IgG (2.63 ± 0.32), 60-76 kDa FITC-Dextran (2.65 ± 0.31), and 150 kDa FITC-Dextran (2.80 ± 0.83), with a 70-90% recovery postbleaching. Additionally, intratumoral delivery of aPD-1 was evaluated in a CRC mouse (C57BL/6) tumor model inoculated with MC38 cells. Quantification of aPD-1 in the plasma and tumor showed an increase in concentration by 1.5- and 3-fold, respectively, when delivered using the intratumoral hydrogel route in comparison with either intraperitoneal (i.p.) or drug-free intratumoral administration. Overall, this noncytotoxic hydrogel provided an alternative delivery route for aPD-1, maximizing its presence both in circulating blood and in the treatment site, serving as a simple localized delivery system in CRC.