A Novel Concept for Cleavable Linkers Applicable to Conjugation Chemistry - Design, Synthesis and Characterization

Area of Science:

• Medicinal Chemistry
• Drug Delivery Systems
• Bioconjugation Chemistry

Background:

• Disulfide bonds are currently the sole cleavable linkers triggered by physiological thiol gradients for intracellular drug release.
• A need exists for alternative cleavable linker strategies that do not rely on disulfide bonds.

Purpose of the Study:

• To introduce a novel concept for a disulfide-bond-free cleavable linker exploiting thiol gradient phenomena.
• To develop and characterize an electron-deficient sulfonamide-based linker for drug conjugation and targeted delivery.

Main Methods:

• Synthesis of an electron-deficient sulfonamide-based cleavable linker.
• Modulation of aryl sulfonamide electron-withdrawing properties to control stability and release.
• In vitro evaluation of linker stability and drug release in human serum.
• Cell-based assays using antibody-drug conjugates (ADCs) to validate intracellular payload release.
• Characterization of drug-linker adduct by-products.

Main Results:

• A novel sulfonamide-based cleavable linker, independent of disulfide bonds, was successfully developed.
• Linker stability and controlled payload release were confirmed in human serum under physiological thiol concentrations using potent cytotoxic drugs.
• Intracellular drug release was validated in cell-based assays with ADCs.
• Downstream by-products of the drug-linker adduct were identified, supporting the proposed release mechanism.

Conclusions:

• A new class of cleavable linkers based on thiol-gradient-triggered sulfonamide chemistry has been established.
• This disulfide-bond-free linker system demonstrates potential for controlled intracellular drug release in targeted therapies like ADCs.
• The findings offer a promising alternative for developing advanced drug delivery systems.