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

## TL;DR

This study evaluates a hydrogel for delivering anti-PD-1 therapy to colorectal cancer tumors in mice, showing improved drug retention and effectiveness.

## Contribution

A noncytotoxic gellan gum-based hydrogel is proposed for localized delivery of anti-PD-1 in colorectal cancer.

## Key findings

- The hydrogel showed a 40% cumulative release of aPD-1 within 24 hours.
- Intratumoral delivery increased aPD-1 concentration in plasma and tumor by 1.5- and 3-fold compared to other routes.
- FRAP analysis revealed varying diffusion rates for different molecular weights in the hydrogel.

## Abstract

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.