ATTEMPTS: a heparin/protamine-based delivery system for enzyme drugs

Area of Science:

• Biochemistry
• Biotechnology
• Pharmacology

Background:

• Enzyme drugs require targeted delivery and controlled release to enhance efficacy and minimize side effects.
• Current enzyme therapeutics, particularly in thrombolytic therapy, face challenges with systemic toxicity and suboptimal activity at target sites.

Purpose of the Study:

• To develop and evaluate an "Antibody Targeted, Triggered, Electrically Modified Prodrug-Type Strategy (ATTEMPTS)" for enzyme drug delivery.
• To enable antibody-directed administration of inactive tissue-type plasminogen activator (tPA) with triggered release at the target site.

Main Methods:

• Cation-modified tPA (mtPA) was attached to a heparin-antifibrin complex via ionic interaction.
• Anti-fibrin IgG was conjugated to heparin for targeting; protamine was used as a competitive heparin inhibitor to trigger tPA release.
• Cation modification of tPA was achieved through chemical conjugation or recombinant DNA methods.

Main Results:

• The modification process did not significantly alter tPA's specific activity (plasminogen activation, fibrin-binding, fibrinogen response).
• The heparin/mtPA complex exhibited no intrinsic catalytic activity due to heparin blocking the tPA active site.
• Protamine addition reversed heparin-induced inhibition, demonstrating prodrug-like behavior and controlled release.

Conclusions:

• Heparin/protamine-based enzyme delivery systems offer a promising approach to regulate active enzyme release and mitigate systemic toxicity.
• This strategy can potentially improve enzyme therapeutics and thrombolytic therapy outcomes.
• Optimization via recombinant DNA technology and computer simulation has enhanced the therapeutic efficacy of the original strategy.