# Systematic design of DMBT1-derived peptides correlating physicochemical properties and sequence motifs with siRNA delivery and efficacy in cancer therapy

## TL;DR

Researchers designed peptides to improve siRNA delivery for cancer therapy, identifying a key motif that enhances effectiveness and safety in animal models.

## Contribution

A systematic framework for optimizing DMBT1-derived peptides for siRNA delivery, including a conserved motif linked to high gene silencing efficiency.

## Key findings

- Twenty-seven peptides improved siRNA binding, and twenty achieved robust uptake in serum.
- The SWGRVRVLRGDKW motif was associated with over 75% gene knockdown efficiency.
- Lead peptide HE25 reduced tumor growth in mice and showed biosafety in repeated dosing.

## Abstract

Molecules driving the cancer process are frequently difficult to target with traditional small-molecule drugs. Small interfering RNAs (siRNAs) offer high specificity, but their clinical translation is hindered by inefficient delivery and rapid degradation. We previously identified DMBT1-derived cell-penetrating peptides (CPPs) that encapsulate siRNA and improve serum stability in vitro.

We designed 37 DMBT1-derived peptides using a rational, high-throughput pipeline to enhance siRNA encapsulation, stability, and delivery. Binding, uptake, and silencing were assessed in A375 and MCF7 cells. Regression and motif discovery analyses were applied to link peptide physicochemical features with encapsulation efficiency, serum stability, and gene silencing.

Twenty-seven peptides showed improved siRNA binding and 20 achieved robust uptake in serum. We identified a conserved motif, SWGRVRVLRGDKW, enriched in complexes achieving >75% knockdown, associated with efficient cytosolic release. HE25 emerged as the lead peptide, delivering BRAFV600E-siRNA and significantly reducing A375 proliferation in vitro. In female NOG CIEA mice xenografts, HE25 suppressed tumour growth, while repeated intravenous dosing in BALB/c mice confirmed biosafety.

Targeted optimisation combined with motif-based design establishes a framework for developing next-generation CPPs. The identification of a conserved motif driving efficient delivery highlights new opportunities for advancing siRNA therapeutics in cancer and beyond.

This work was supported by 10.13039/501100009708Novo Nordisk Foundation, 10.13039/100008398Villum Foundation, 10.13039/501100003554Lundbeck Foundation, 10.13039/501100005747A.P. Møller Foundation, 10.13039/100007403Dagmar Marshalls Foundation, Neye Foundation, 10.13039/501100010347Fabrikant Einar Willumsens Mindelegat, and Direktør Michael Hermann Nielsens Mindelegat.