Silane-tagged degrader Compound 7 achieves potent EGFR degradation in NSCLC models

A new hydrophobic tagging (HyT) degrader, designated Compound 7 in HyTdb (entry HyT-001), has been reported to induce efficient degradation of mutant EGFR in non-small cell lung cancer (NSCLC) models. The molecule couples a gefitinib-derived warhead to a tert-butyl(diphenyl)silane hydrophobic tag through a short alkyl linker.

Design and structure

The degrader follows the classic three-component architecture: a target-binding warhead, a linker, and a hydrophobic tag. The silane tag provides substantial hydrophobicity (calculated ClogP ≈ 5.18), which is believed to trigger recognition by the cellular quality-control machinery and subsequent degradation of the bound protein.

• Warhead — gefitinib scaffold, targeting the EGFR ATP-binding pocket
• Linker — short aliphatic chain (OCCCO)
• Hydrophobic tag — tert-butyl(diphenyl)silane

Degradation activity

Western blotting showed a dose-dependent decrease in mutant EGFR levels in HCC-827 cells, with a DC50 of 0.75 ± 0.1 μM. A second cell line (PC-9) gave a DC50 of 1.42 ± 0.3 μM. Cell viability assays (CCK-8) returned IC50 values of 0.09 μM and 0.34 μM respectively.

Mechanism of action

Mechanistic experiments point to the ubiquitin–proteasome pathway. After the warhead engages EGFR, the exposed hydrophobic tag is thought to be recognized by chaperones, leading to ubiquitination and proteasomal clearance of the receptor.

Pharmacokinetics

In vivo PK studies in mice showed a half-life of 2.18 h after intravenous dosing (1 mg/kg) and an oral bioavailability of 8.67% at 10 mg/kg. The compound was well tolerated in the tested dose range.

Significance

This entry illustrates how a clinically validated kinase inhibitor can be repurposed as a warhead for hydrophobic tagging, expanding the chemical space of degraders beyond bifunctional PROTACs. The accompanying structural, activity, PK, and disease-association data are fully recorded in the HyTdb entry page.