PROJECT SUMMARY
Currently, there is no curative medication available for ulcerative colitis (UC), a type of inflammatory bowel
disease affecting the innermost mucosal layer of the rectum and the colon. Although mucosal healing is a major
treatment goal, many patients fail to achieve mucosal healing with available UC drugs such as anti-inflammatory,
immuno-modulatory and anti-TNF agents. Since epithelial repair is a critical process towards mucosal healing,
an agent facilitating this process will provide a novel therapeutic strategy differentiating from existing clinical care
for UC. Our therapeutic lead is a variant of the oral cholera vaccine antigen cholera toxin B subunit (CTB), which
was modified with a C-terminal extension including an endoplasmic reticulum retention motif (CTBSEKDEL). We
have recently shown that oral administration of CTBSEKDEL, but not native CTB, facilitates colon epithelial repair
and mucosal healing in a dextran sodium sulfate (DSS)-induced acute colitis mouse model. Moreover, biweekly
oral administration of CTBSEKDEL significantly reduced tumorigenesis in the azoxymethane/DSS model of colitis-
associated cancer. Based on these findings, we hypothesize that CTBSEKDEL provides a prototype oral biologic
facilitating mucosal healing in UC. The goal of this translational R01 project is to optimize and validate the
therapeutic potential of CTBSEKDEL in preclinical UC models. Since CTBSEKDEL has already shown feasibility in an
acute colitis model, we will immediately proceed with further validation in chronic colitis models. In parallel, in
Aim 1, we will create CTBSEKDEL variants with modifications in the C-terminal sequence (CTB(X)H/KDEL) to improve
molecular stability upon spray dry for enteric-coated formulations. We will produce these proteins using a
Nicotiana benthamiana plant transient overexpression system and screen them based on a series of biochemical
and biophysical assays, as well as a mouse acute DSS colitis model. In Aim 2, we will validate the efficacy and
safety of CTBSEKDEL and a selected CTB(X)H/KDEL in two chronic colitis models based on repeated DSS exposure
in C57bl/6 mice and piroxicam-exposed IL-10 knockout mice, in comparison to an anti-TNFa antibody.
Therapeutic efficacy and safety will be determined by disease activity index, histopathology,
immunohistochemistry and molecular biological analysis of inflammation, crypt regeneration, epithelial barrier
recovery and fibrosis. In Aim 3, we will employ a human colon explant model to further validate the mucosal
healing potential of CTBSEKDEL and CTB(X)H/KDEL. Colon biopsy and colectomy tissues will be obtained from
patients with different disease history and biological backgrounds. Efficacy will be evaluated based on wound
healing-related gene expression and immunohistochemistry for epithelial proliferation/regeneration markers. Cell
type-specific responses will be investigated in colon lamina propria mononuclear cells and colonic organoids.
Collectively, the project will generate pivotal preclinical data supporting the development of a first-in-class oral
biologic candidate inducing colon epithelial repair for UC treatment towards a Phase I clinical trial.
