# Discovery of first-in-class inhibitors of the TRF1:TIN2 protein:protein interaction by fragment screening

## TL;DR

Researchers discovered the first inhibitors of a key protein interaction in telomere protection, which could lead to new cancer treatments.

## Contribution

The first-in-class TRF1:TIN2 interaction inhibitors were identified using fragment screening techniques.

## Key findings

- Compound 40 binds to TRF1TRFH with a KD of 29 µM and displaces TIN2 with an IC50 of 67 µM.
- The compound expels TRF1 from the shelterin complex, disrupting its assembly.
- A novel crystal system of TRF1TRFH was used to identify binding hotspots for future drug development.

## Abstract

TRF1 is a subunit of the shelterin complex that binds to and protects the linear ends of chromosomes known as telomeres. Both genetic deletion and chemical inhibition of TRF1 have been shown to block the growth of lung carcinoma, glioblastoma, and renal cell carcinoma in mice without affecting mouse survival or tissue function, making TRF1 a potential therapeutic target in cancer1–3. Here, we report the discovery of a series of fragment hits that bind at the interface between the TRFH domain of TRF1 (TRF1TRFH) and a peptide of TIN2 (TIN2TBM), an interaction essential for the recruitment of TRF1 to shelterin, using X-ray crystallography (XChem) and ligand-observed NMR (LO-NMR) fragment screening. We discovered a first-in-class inhibitor of the TRF1:TIN2 interaction (compound 40) that binds to TRF1TRFH with a KD of 29 µM (95% CI: 20–41 µM), displaces a TIN2 probe with an IC50 of 67 µM (95% CI: 10–120 µM), and expels TRF1 from purified shelterin. Aided by a novel crystal system of TRF1TRFH, we characterised fragments binding in a hotspot at the TRF1:TIN2 interface; these will serve as a starting point for the structure-guided development of potent inhibitors of TRF1 protein:protein interactions to disrupt shelterin complex assembly.

The online version contains supplementary material available at 10.1038/s41598-025-23858-3.