# Preclinical Development of First-in-Class GSTO1 Degraders for Colorectal Cancer

> **NIH NIH R01** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2022 · $542,198

## Abstract

Glutathione S-transferase omega 1 (GSTO1) is an atypical GST isoform that is overexpressed in several cancers
and has been implicated in drug resistance. Currently, no small-molecule drug targeting GSTO1 is under clinical
development. Using genetic tools, including extensive bioinformatics analysis coupled with siRNA, shRNA,
proteomics, and CRISPR/Cas9 technologies; and pharmacologic small-molecule inhibitors and degraders, we
have validated GSTO1 as an impactful druggable target in oncology. Previously, we identified C1-27 as a potent
GSTO1 inhibitor that shows efficacy against cancer cells in both in vitro and in vivo models. We also synthesized
and tested the very first GSTO1 PROTAC confirming GSTO1 degradation in vitro. Through transcriptional
profiling using Bru-seq and RNA-seq coupled with proteomics, we uncovered novel pharmacodynamic markers
and cellular pathways critical for oncogenesis regulated by GSTO1. Taken together, our findings validate GSTO1
as an important drug target for cancer therapeutics and C1-27 as a potent and validated prototype inhibitor.
Previously, we solved the crystal structure of C1-27 (IC50 = 31 nM) and other potent inhibitors in complex with
GSTO1. Our most recent lead optimization campaign using 6 different co-crystal structures resulted in the most
potent GSTO1 inhibitor (IC50 = 0.22 ± 0.02 nM) known to date. Our CRISPR/Cas9 GSTO1 knockout (KO) cell
lines do not form tumors or display tumor growth delay in vivo and form smaller 3D spheroids in vitro. Through
multi-omics studies in GSTO1 KO cells, we found a strong positive correlation with cell adhesion molecules and
interferon response pathways, and a strong negative correlation with Myc transcriptional signature. Importantly,
we also identified several clinically used chemotherapies showing significant synthetic lethality with loss or
inhibition of GSTO1. We discovered that tissue factor (gene name, F3) transcription and protein expression are
downregulated in response to GSTO1 KO and C1-27 treatment, further implicating a role for GSTO1 in the innate
immune response. In summary, our results implicate GSTO1 as a therapeutic target in cancer and offer new
mechanistic insights into its significant role in cancer progression. Importantly, our results show for the first time
that inhibition of GSTO1 can activate immune responses and downregulate F3. We hypothesize that inhibiting
GSTO1 will have a two-pronged effect on tumor cells: (A) impair cancer cell survival by reducing Myc
transcriptional signature and F3 downregulation, and (B) enhance immune responses through interferon-
mediated innate immune sensing of cancers. We further hypothesize that GSTO1 inhibitors will sensitize cancer
cells to select chemotherapy and immunotherapy. We will test these hypotheses through the following three
specific aims. Aim 1: Elucidate the functions of GSTO1 in enhancing immune response through activation of
type-I interferon and reducing tumor cell viability through F3 and My...

## Key facts

- **NIH application ID:** 10520682
- **Project number:** 1R01CA266513-01A1
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** NOURI NEAMATI
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $542,198
- **Award type:** 1
- **Project period:** 2022-08-02 → 2027-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10520682

## Citation

> US National Institutes of Health, RePORTER application 10520682, Preclinical Development of First-in-Class GSTO1 Degraders for Colorectal Cancer (1R01CA266513-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10520682. Licensed CC0.

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