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Problems of delivery of monoclonal antibodies. Pharmaceutical and pharmacokinetic solutions
R M Reilly1, J Sandhu, T M Alvarez-Diez
1Division of Nuclear Medicine, Toronto Hospital, Ontario, Canada.
Abstract:
Monoclonal antibodies to tumour-associated antigens have great theoretical potential for the specific targeting of radioactivity and anti-neoplastic agents to tumours. The clinical success of monoclonal antibody-based cancer diagnosis and therapy depends, however, on solving a number of pharmacokinetic delivery problems. These include: (i) slow elimination of monoclonal antibodies from the blood and poor vascular permeability; (ii) low and heterogeneous tumour uptake; (iii) cross-reactivity with normal tissues; (iv) metabolism of monoclonal antibody conjugates; and (v) immunogenicity of murine forms in humans. As a result of extensive pharmaceutical and pharmacokinetic research conducted over the past 10 to 15 years, several potential solutions to these delivery problems have been identified. Blood concentrations of antibody conjugates may be reduced through regional administration, the use of antibody fragments, interventional strategies and various pre-targeting techniques. Tumour uptake may be increased through administration of higher doses, or the use of agents to increase tumour vascular permeability. Tumour retention of antibody conjugates may be improved by inhibition of metabolism, by using more stable linkage chemistry. Alternatively, normal tissue retention may be decreased through the use of metabolisable chemical linkages inserted between the antibody and conjugated moiety. Very small antigen-binding fragments and peptides that exhibit improved tumour penetration and more rapid elimination from the blood and normal tissues have been prepared by genetic engineering techniques. Chimeric (mouse/human) and human monoclonal antibodies have been developed to circumvent the problem of immunogenicity. Future research will continue to be focused on improvements in the design of monoclonal antibodies for tumour targeting, with the ultimate goal of finally uncovering the 'magic bullet' envisioned by Paul Ehrlich almost a century ago.
Insights
Monoclonal antibodies offer targeted cancer therapy, but delivery challenges like poor tumor uptake and immunogenicity persist. Research is identifying solutions to improve antibody-based drug delivery for effective cancer treatment.
Area of Science:
- Oncology
- Pharmacology
- Biotechnology
Background:
- Monoclonal antibodies targeting tumor-associated antigens show promise for specific delivery of radioactivity and anti-cancer agents.
- Clinical application is hindered by pharmacokinetic delivery challenges including slow blood elimination, poor tumor penetration, and immunogenicity.
Purpose of the Study:
- To review and identify solutions for pharmacokinetic delivery problems associated with monoclonal antibody-based cancer diagnosis and therapy.
Main Methods:
- Review of pharmaceutical and pharmacokinetic research over the past 10-15 years.
- Identification of strategies to improve antibody conjugate delivery, including regional administration, antibody fragments, pre-targeting, and enhanced tumor vascular permeability.
- Development of genetic engineering techniques for smaller antibody fragments and peptides with improved tumor penetration and clearance.
- Creation of chimeric and humanized monoclonal antibodies to reduce immunogenicity.
Main Results:
- Several strategies have been identified to overcome delivery challenges.
- Reduced blood concentrations can be achieved through regional administration, antibody fragments, and pre-targeting.
- Tumor uptake and retention can be enhanced by increasing vascular permeability and using stable linkage chemistry.
- Genetic engineering yields smaller fragments with better tumor penetration and faster clearance.
- Chimeric and human antibodies address immunogenicity concerns.
Conclusions:
- Significant progress has been made in addressing pharmacokinetic delivery issues for monoclonal antibody-based cancer therapies.
- Ongoing research focuses on optimizing monoclonal antibody design for effective tumor targeting, aiming for the 'magic bullet' ideal.
- Overcoming these delivery hurdles is crucial for realizing the full clinical potential of antibody-drug conjugates in oncology.