Antibody-targeted photodynamic therapy

To assess the feasibility of conjugation of verteporfin (Visudyne, Parkedale Pharmaceuticals, Rochester, Minnesota, USA) to antibody against vascular endothelial growth factor.

Experimental study.

Rabbit antimouse vascular endothelial growth factor polyclonal antibody was conjugated to verteporfin. Fluorescence excitation-emission spectra of verteporfin and conjugate were examined. Vascular endothelial growth factor-expressing murine endothelial cells were incubated with saline, verteporfin, or conjugate, followed by laser exposure or no laser exposure. Cell viability at 1 and 24 hours was assessed via trypan blue exclusion. Results were analyzed by two-way analysis of variance with replication and the Bonferroni multiple comparison test.

The fluorescence excitation-emission spectrum of the conjugate was similar to that of verteporfin. After laser exposure, cell viability in conjugate-treated cells was reduced to 6% at 1 hour (P <.0001) and to 4% at 24 hours (P <.0001), compared with approximately 40% in nonlaser-exposed, conjugate-treated cells. The cytotoxicity in the conjugate-treated cells was higher than in verteporfin-treated cells exposed to laser, although the difference did not reach statistical significance.

The conjugation of verteporfin to polyclonal antibody is possible without the loss of its photosensitizing properties. Conjugated verteporfin destroys cellular targets at least as effectively as verteporfin alone.