Conjugation of cRGD Peptide to Chlorophyll a Based Photosensitizer (HPPH) Alters Its Pharmacokinetics with Enhanced Tumor-Imaging and Photosensitizing (PDT) Efficacy

Abstract

The αvβ3 integrin receptor plays an important role in human metastasis and tumor-induced angiogenesis. Cyclic Arg-Gly-Asp (cRGD) peptide represents a selective αvβ3 integrin ligand that has been extensively used for research, therapy, and diagnosis of neoangiogenesis. For developing photosensitizers with enhanced PDT efficacy, we here report the synthesis of a series of bifunctional agents in which the 3-(1′-hexyloxyethyl)-3-devinylpyropheophorbide-a (HPPH), a chlorophyll-based photosensitizer was conjugated to cRGD and the related analogs. The cell uptake, in vitro PDT efficacy of the conjugates were studied in αvβ3 integrin overexpressing U87 and 4T1 cell lines whereas the in vivo PDT efficacy and fluorescence-imaging potential of the conjugates were compared with the corresponding non-conjugated photosensitizer HPPH in 4T1 tumors. Compared to HPPH, the HPPH-cRGD conjugate in which the arginine and aspartic acid moieties were available for binding to two subunits of αvβ3 integrin showed faster clearance, enhanced tumor-imaging and PDT efficacy at 2–4 h post-injection. Molecular modeling studies also confirmed that the presence of HPPH moiety in HPPH-cRGD conjugate does not interfere with specific recognition of cRGD by αvβ3 integrin. Compared to U87 and 4T1 cells the HPPH-cRGD showed significantly low photosensitizing efficacy in A431 (αvβ3 negative) tumor cells, suggesting possible target-specificity of the conjugate.

Photodynamic diagnosis of gastric cancer using HPPH-CD

“…19 Recent uorescence imaging studies with HPPH-CD aimed at tumor imaging also revealed the conjugate to have signicant tumor-imaging capability with excitation of the uorescent cyanine dye moiety in subcutaneous models created by the implantation of carcinoma cells such as RIF cells, colon 26 cells and human U87 cells. 27,28 Herein, our data paralleled previously published study that HPPH-CD showed great imaging efficacy in subcutaneous tumors using the S180 tumor model with obvious contrast between the tumors and surrounding tissues.…”

Synthesis, Photophysical Properties, and Biological Evaluation of trans-Bisthioglycosylated Tetrakis(fluorophenyl)chlorin for Photodynamic Therapy

“…10 Recently, the 14-mer bombesin, which is a high-affinity ligand for gastrin-releasing peptide receptor, was conjugated to a photosensitizer for use in PDT. 8 CTPs are more cost-effective ligands than antibodies, and it is relatively easy to prepare uniform conjugates.…”

Strategies for optimizing the delivery to tumors of macrocyclic photosensitizers used in photodynamic therapy (PDT)

“…It has been shown that peptides with a RGD motif bind selectively to the a v b 3 integrin and cRGD (cyclic Arg-Gly-Asp) peptides were particularly useful for tumor targeting with therapeutics and imaging agents. Srivatsan et al conjugated the chlorophyll a derivative 2-(10-hexyloxyethyl)-2-devinylpyropheophorbide a (HPPH) to cRGD and confirmed specific targeting of a v b 3 integrin overexpressing tumors with the conjugated HPPH [98]. In vitro studies with 4T1 mouse mammary tumor and U87 human glioblastoma cells, both overexpressing the a v b 3 integrin, showed much higher phototoxicity of the conjugate in comparison to HPPH while in the a v b 3 -negative A431 cells the unconjugated HPPH was more phototoxic.…”