A single-chain fab derived drug conjugate for HER2 specific delivery

Area of Science:

• Biotechnology
• Oncology
• Immunology

Background:

• Fragment antigen-binding (Fab) based drug conjugates offer unique advantages over traditional antibody-drug conjugates.
• Current limitations in Fab protein availability and stability hinder the development of Fab drug conjugates.

Purpose of the Study:

• To develop a stabilized single-chain Fab scaffold for high-yield expression.
• To create a homogenous Fab-SN38 conjugate for targeted chemotherapy.
• To evaluate the in vitro and in vivo efficacy and safety of the novel Fab conjugate.

Main Methods:

• Engineered a single-chain Fab scaffold for enhanced stability and bacterial expression.
• Utilized sortase A ligation to conjugate the anti-neoplastic agent SN38 to the Fab C-terminus, achieving a drug-to-Fab ratio of 1.
• Assessed antigen-dependent cell-killing ability and in vivo anti-tumor efficacy in HER2-positive tumors.

Main Results:

• Achieved high-yield expression of a stabilized single-chain Fab in bacterial cytoplasm.
• Generated a homogenous anti-HER2 Fab-SN38 conjugate with a precise drug-to-Fab ratio.
• Demonstrated potent, antigen-dependent cytotoxicity and significant tumor growth inhibition in vivo.
• Observed good tolerability at a dose of 7 mg/kg.

Conclusions:

• The developed single-chain Fab scaffold overcomes limitations in Fab protein stability and availability.
• The homogenous Fab-SN38 conjugate exhibits promising anti-tumor activity, safety, and tumor penetration.
• Fab conjugates represent a viable and advantageous platform for targeted chemotherapy.