# Development of PD-L1 Proteolysis-Targeting Chimeras (PROTACs): An Innovative Cancer Drug Discovery Route

> **NIH NIH F31** · TEXAS A&M UNIVERSITY · 2024 · $39,353

## Abstract

Project Summary
The current cancer treatment bottleneck showcases the need for more innovative approaches in drug discovery
efforts. As of recent, immune-checkpoint inhibitors (ICHs) have shown promise in cancer therapeutics, and work
by manipulating immunoregulatory pathways involved in tumor detection and elimination. Many cancer types
overexpress the PD-L1 receptor to inhibit T cell activation and subsequently evade the immune response.
Though proven effective, the PD-1/PD-L1 pathway targeting ICHs are pharmacologically limited by occupancy-
based inhibition. A new drug paradigm has emerged through the development of proteolysis targeting chimeras
(PROTACs) that are not limited by such a mechanism. PROTACs are heterobifunctional molecules consisting of
an E3 ubiquitin (Ub) ligase ligand, a target protein warhead, and a linker connecting the two and work by bringing
an E3 Ub ligase and the target protein together through bivalent binding. The formation of a ternary structure
through this bivalent interaction drives the polyubiquitination and subsequent degradation of the target via the
ubiquitin proteasome system (UPS). Although this drug design has shown great medicinal promise through
research findings and clinical trials, there is seldom literature on the use of transmembrane E3 Ub ligase
recruiting PROTACs to degrade cancer-promoting membrane proteins such as PD-L1. The proposed project
is aimed at investigating the applicability of such PD-L1 PROTACs by recruitment of the transmembrane
E3 Ub ligase ZNRF3. In doing so, three specific aims will be investigated: Aim 1. Identifying cyclic peptide
binders of the ZNRF3 extracellular domain. Previous research in the Liu lab utilized a cyanobenzothiazole based
linker that allows for cyclization of peptides on a phage surface with applications in phage selections against
CD44 and SARS-CoV-2 spike protein epitopes. Recombinant bacterial expression of biotinylated ZNRF3 ECD
has been developed, and the binding of selected cyclic peptides will be validated through BLI and flow cytometry.
Aim 2. Synthesis and in-vitro characterization of PD-L1 PROTACs. Reported binders of PD-L1 will be
incorporated in the PROTAC design via polyethylene glycol (PEG) and polyether linkages of varying lengths.
The optimal positioning of linkers will be determined through structure-activity relationships (SAR) analysis,
binding assays, co-cocrystal structures, and molecular docking studies of ligand-protein interactions of the
ZNRF3 ECD and PD-L1. Aim 3. In-vivo characterization of PD-L1 PROTACs. Degradation potency will be
evaluated with western-blotting of residual PD-L1 and ZNRF3 dependency on the induced degradation of PD-L1
and mode of action (proteosome vs lysosome) will be assessed. In addition, whole-cell proteomics studies will
be conducted to investigate any consequences on normal cellular activities due to PROTAC activity. By
accomplishing these aims, new and important conclusions can be made about the efficacy a...

## Key facts

- **NIH application ID:** 10816386
- **Project number:** 5F31CA268883-02
- **Recipient organization:** TEXAS A&M UNIVERSITY
- **Principal Investigator:** Demonta Coleman
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $39,353
- **Award type:** 5
- **Project period:** 2023-04-01 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10816386

## Citation

> US National Institutes of Health, RePORTER application 10816386, Development of PD-L1 Proteolysis-Targeting Chimeras (PROTACs): An Innovative Cancer Drug Discovery Route (5F31CA268883-02). Retrieved via AI Analytics 2026-07-20 from https://api.ai-analytics.org/grant/nih/10816386. Licensed CC0.

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