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Targeting cancer micrometastases with monoclonal antibodies: a binding-site barrier
1Nuclear Medicine Department, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
Monoclonal antibodies penetrate bulky tumors poorly after intravenous administration, in part because of specific binding to the target antigen. Experiments presented here demonstrate an analogous phenomenon in micrometastases; poor antibody penetration, attributable to a "binding-site barrier" phenomenon, can be seen in guinea pig micrometastases as small as 300 microns in diameter. Increasing the dose of antibody can partially overcome this limitation, but at a cost in specificity.
Insights
Monoclonal antibodies struggle to reach small tumors due to a binding-site barrier. Higher antibody doses can improve penetration but may reduce targeting accuracy.
Area of Science:
- Oncology
- Immunology
- Pharmacokinetics
Background:
- Monoclonal antibodies (mAbs) are crucial therapeutics but face challenges in reaching tumor sites.
- Poor penetration into bulky tumors is partly due to specific binding to target antigens.
Purpose of the Study:
- To investigate antibody penetration in micrometastases.
- To understand the "binding-site barrier" phenomenon in small tumor deposits.
Main Methods:
- Experiments were conducted using guinea pig models with micrometastases.
- Antibody penetration was assessed in relation to tumor size and antibody dose.
Main Results:
- A "binding-site barrier" limits antibody penetration in micrometastases as small as 300 microns.
- Increasing antibody dose partially overcomes this barrier.
- Higher doses lead to a decrease in antibody specificity.
Conclusions:
- The binding-site barrier significantly impacts antibody delivery to small tumors.
- Dose escalation is a potential strategy to improve penetration but requires careful consideration of specificity trade-offs.