Towards engineering hormone-binding globulins as drug delivery agents

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Delivery Systems

Background:

• Targeted drug delivery is crucial for minimizing severe side effects in diseases like cancer.
• Corticosteroid binding globulin (CBG) naturally carries cortisol and releases it upon cleavage by elastase at inflammation sites.
• Exploiting natural biological mechanisms offers elegant solutions for precise therapeutic delivery.

Purpose of the Study:

• To investigate the feasibility of engineering CBG for targeted delivery of therapeutic agents.
• To modify CBG's reactive center loop for cleavage by disease-specific proteases.
• To demonstrate the potential of engineered CBG in reducing off-target drug toxicity.

Main Methods:

• Site-directed mutagenesis was used to alter CBG's reactive center loop.
• Engineered CBG was tested for cleavage by prostate specific antigen (PSA) and thrombin.
• Fluorescence-based assays were employed to assess ligand binding and release modifications.
• Mutations were introduced to enhance ligand release efficiency.

Main Results:

• CBG was successfully engineered to be cleaved by PSA, relevant for prostate hyperplasia, and thrombin, relevant for thrombotic sites.
• The engineered CBG demonstrated the ability to bind a new compound, thyroxine-6-carboxyfluorescein, instead of cortisol.
• Mutations were shown to increase the efficiency of ligand release from CBG.
• This proof-of-concept study validates engineered CBG as a potential drug delivery vehicle.

Conclusions:

• Engineered CBG offers a novel platform for targeted drug delivery, leveraging protease-specific cleavage.
• This approach holds significant promise for reducing off-target effects in various disease treatments.
• Modifying the serpin conformational change mechanism provides a versatile strategy for therapeutic development.