Polymeric conjugates of mono- and bi-cyclic alphaVbeta3 binding peptides for tumor targeting
Amitava Mitra1, Tomika Coleman, Mark Borgman
1Department of Pharmaceutical Sciences, University of Maryland, Baltimore, Maryland 21201, USA.
Abstract:
The alphaVbeta3 integrin plays important roles in tumor-induced angiogenesis and tumor metastasis and hence, many small molecule alphaVbeta3 ligands have been developed for cancer diagnosis and therapy. Although these show good alphaVbeta3 targeting, most have suboptimal pharmacokinetics and show rapid tumor washout. We studied the biodistribution and tumor targeting properties of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer based conjugates of mono-(RGDfK) and doubly cyclized (RGD4C) alphaVbeta3 binding peptides. Endothelial cell adhesion studies showed similar affinity of HPMA-RGD4C and HPMA-RGDfK conjugate for alphaVbeta3 integrins. Scintigraphic images of tumor bearing mice demonstrated that both conjugates showed tumor localization at 24 h post-injection and were retained at the tumor site until 192 h, whereas the efficient background clearance was observed over time. Necropsy organ counts showed that tumor accumulation of both HPMA-RGD4C and HPMA-RGDfK conjugates increased over time with peak accumulations at 4.9 +/- 0.9% and 5.0 +/- 1.2% ID/g, respectively. In contrast the background organ distribution rapidly cleared over time resulting in significant increases of tumor-to-background ratios. The radioactive dose as indicated by the area under curve (HPMA-RGD4C: 4825.3 microCi/g h and HPMA-RGDfK: 4424.9 microCi/g h) was highest for the tumor. The polymer conjugates of RGD4C or RGDfK provide a means to enhance tumor uptake, decrease background accumulation, and enable selective delivery of therapeutic or diagnostic agents to tumor sites.
Insights
New polymer conjugates using RGD4C or RGDfK peptides show enhanced tumor targeting and retention for cancer therapy. These N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-based agents improve tumor uptake and reduce background accumulation.
Area of Science:
- Bioconjugate Chemistry
- Integrin Biology
- Cancer Therapeutics
Background:
- AlphaVbeta3 integrin is crucial for tumor angiogenesis and metastasis.
- Existing small molecule alphaVbeta3 ligands often have poor pharmacokinetics and rapid tumor washout.
- There is a need for improved delivery systems for targeted cancer diagnosis and therapy.
Purpose of the Study:
- To evaluate the biodistribution and tumor targeting properties of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-based conjugates.
- To compare the efficacy of mono-(RGDfK) and doubly cyclized (RGD4C) alphaVbeta3 binding peptides when conjugated to HPMA copolymers.
- To assess the potential of these conjugates for selective delivery of diagnostic or therapeutic agents to tumors.
Main Methods:
- Synthesis of HPMA copolymer conjugates with RGDfK and RGD4C peptides.
- Endothelial cell adhesion studies to determine binding affinity for alphaVbeta3 integrins.
- In vivo biodistribution studies using scintigraphy in tumor-bearing mice.
- Quantification of conjugate accumulation in tumors and organs via necropsy counts.
Main Results:
- Both HPMA-RGD4C and HPMA-RGDfK conjugates demonstrated similar high affinity for alphaVbeta3 integrins.
- Scintigraphy confirmed tumor localization and sustained retention (up to 192 h) for both conjugates.
- Organ biodistribution revealed rapid clearance from background tissues, leading to significantly increased tumor-to-background ratios.
- Peak tumor accumulation reached approximately 5% ID/g for both conjugates, with the highest radioactive dose (area under the curve) observed in tumors.
Conclusions:
- HPMA copolymer conjugates of RGD4C and RGDfK peptides effectively target and accumulate in tumors.
- These polymer conjugates improve upon existing ligands by enhancing tumor uptake and reducing background accumulation.
- The developed conjugates offer a promising strategy for the selective delivery of diagnostic and therapeutic agents to tumor sites.
