Pheophorbide a (Pba) is a chlorophyll catabolite
that has been proposed as photosensitizer in photodynamic
therapy. In a previous study we conjugated Pba to
monomethoxy-polyethylene glycol (mPEG-Pba), to increase
its solubility and pharmacokinetics. Here, we compare
the photodynamic therapy efficacy of free Pba and
mPEG-Pba to cure a subcutaneous amelanotic melanoma
transplanted in C57/BL6 mice. The photosensitizers, i.p.
injected (30 mg/kg), showed no toxicity when the animals
were kept in the dark. But, after photoactivation with a
660 nm laser (fluence of 193 J/cm2), both photosensitizers,
in particular mPEG-Pba, showed a strong efficacy to cure
the tumor, both in terms of tumor growth delay and increase
of Kaplan-Meier median survival time. Together, our in vivo data demonstrate that mPEG-conjugated Pba is a promising
photosensitizer for the photodynamic therapy of cancer.
