# Design of Potent Mannose‐6‐Phosphate Derivatives as Ligands for CI‐M6P/IGF2R Using Fluorescence Polarization Assay

## TL;DR

Researchers designed new M6P derivatives to better bind a key receptor involved in lysosomal enzyme transport, using a fluorescence test to evaluate their effectiveness.

## Contribution

The study introduces multivalent M6P derivatives and phosphonate-based analogs as more stable and potent ligands for the CI-M6P/IGF2R receptor.

## Key findings

- Multivalent M6P ligands show significantly higher receptor affinity compared to monomeric compounds.
- Phosphonate groups are a more stable and potent alternative to native M6P for receptor binding.
- Computational modeling helps explain the binding mechanisms of the ligands with the receptor.

## Abstract

The cation‐independent mannose‐6‐phosphate/IGF2 receptor (CI‐M6P/IGF2R) plays a crucial role in transporting lysosomal enzymes and other ligands. In this study, we designed and synthesized novel stable mannose‐6‐phosphate (M6P) derivatives to enhance their affinity for CI‐M6P/IGF2R. To evaluate the binding potency, we employed a sensitive and cost‐effective fluorescence polarization assay, enabling rapid quantification of receptor–ligand interactions in solution. The tested compounds included di‐, tri‐, and penta‐M6P peptides along with various M6P‐derived small molecules featuring phosphate isosteres or other functional modifications. Our findings indicate that ligands bearing multiple M6P moieties exhibit significantly higher receptor affinities than monomeric compounds and that phosphonate groups may serve as a more stable and potent alternative to native M6P. Computational modeling of ligand interactions with the CI‐M6P/IGF2R domains further elucidated the binding mechanisms, offering new directions for the development of more effective ligands. This study advances the design of therapeutic strategies that leverage CI‐M6P/IGF2R for targeted biomolecule delivery to lysosomes, thereby opening new possibilities for biomedical applications.

We designed and synthesized novel mannose‐6‐phosphate (M6P) derivatives to enhance their binding affinity for the CI‐M6P/IGF2 receptor, which plays a key role in lysosomal targeting. Using a fluorescence polarization assay, we evaluated di‐, tri‐, and penta‐M6P peptides and modified M6P analogs. Our results show that multivalent ligands significantly improve receptor binding, with phosphonate groups emerging as a promising stable alternative to native M6P