# Development of a Tumor-Specific PROTAC

> **NIH NIH F31** · YALE UNIVERSITY · 2020 · $30,240

## Abstract

Project Summary:
Proteolysis Targeting Chimeras (PROTACs) have introduced a new pharmacological paradigm, event-driven
pharmacology. PROTACs are bifunctional small-molecules that simultaneously engage an E3 ubiquitin ligase
and a protein of interest (POI). Ternary formation induced by PROTAC binding results in ubiquitination of the
POI by the E3 ligase and subsequent degradation of the POI by the 26S proteasome. Most research efforts have
focused on increasing POI diversity. However, identification and development of E3 ligase recruiting elements
(E3REs) has lagged. The next innovation for PROTAC technology is the induction of tumor-specific protein
degradation. PROTACs that induce degradation only in tumor cells are likely to have decreased off-target
cytotoxicity, thereby improving their therapeutic utility. However, the E3 ligases most commonly recruited, Von
Hippel-lindau, Cereblon, and Mouse double minute 2 homolog, are expressed in both cancerous and
untransformed tissues. New E3REs must be developed that engage E3 ligases with tumor specific expression
to impart tumor-specificity.
Type I Melanoma Antigen Gene (MAGE) family proteins are cancer testis antigens, whose expression is
restricted to the male germ line, but can be re-expressed in cancers. MAGE-A3 binds TRIM28, a ubiquitously
expressed protein with E3 ligase activity, to form an oncogenic tumor-specific E3 ligase complex. A PROTAC
harboring a MAGE-A3 E3RE may be able to recruit MAGE-A3/TRIM28 and induce tumor-specific degradation.
MAGE-A3 has been found to exist as a dimer in solution. A fluorescent peptide that mimics key residues involved
in this dimerization will be used to develop a fluorescence polarization assay (FP). The FP assay will then be
used to identify a small-molecule ligand of MAGE-A3. Orthogonal biophysical assays, like thermal shift, intrinsic
Trp fluorescence, and isothermal calorimetry will then be used to confirm binding.
Once identified, the MAGE-A3 ligand will be used as an E3RE in the synthesis of a MAGE-A3 based PROTAC.
Cellular experiments using the HaloTag7-GFP reporter system developed in the Crews Lab will then be used to
test the activity of MAGE-A3 based PROTACs. This project will determine if a MAGE-A3 ERE3 can be used to
recruit the MAGE-A3/TRIM28 E3 ligase complex to induce tumor-specific protein degradation. PROTACs
created during this project may serve as the starting point for the future development of a tumor-specific therapy.

## Key facts

- **NIH application ID:** 9977993
- **Project number:** 5F31CA232477-03
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Michael Joseph Bond
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $30,240
- **Award type:** 5
- **Project period:** 2018-09-01 → 2021-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9977993

## Citation

> US National Institutes of Health, RePORTER application 9977993, Development of a Tumor-Specific PROTAC (5F31CA232477-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9977993. Licensed CC0.

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