Temoporfin (
mTHPC) represents a very potent second-generation synthetic
photosensitizer. It has shown to be effective in the
photodynamic therapy of early or recurrent oral
carcinomas, in the
palliative treatment of refractory oral
carcinomas and in the treatment of primary non-melanomatous tumours of the skin of the head and neck. Until now for all positive findings an intravenous application of the
photosensitizer was mandatory. In the case of cutaneous malignant or non-malignant diseases a topical application of the
drug onto the site of the disease followed by illumination, would be advantageous. Unfortunately,
mTHPC is a highly hydrophobic
drug with a low percutaneous absorption. The purpose of this experiment was to investigate the photodynamic efficacy of novel
mTHPC-loaded invasomes after their topical application onto the skin of mice bearing the subcutaneously implanted human colorectal tumour HT29 followed by photoirradiation. Invasomes are vesicles containing in addition to
phospholipids a mixture of
terpenes (
cineole,
citral and
d-limonene) or only one
terpene (
citral) and
ethanol, as penetration enhancers. This was a pilot study since until now no data are available about the efficacy of
mTHPC in the
photodynamic therapy of HT29 tumours after its topical application. The aim of this experiment was to investigate whether a
mTHPC-loaded invasome formulation can reduce tumour size by
photodynamic therapy or at least to find a formulation slowing down tumour growth compared to the control group (mice without any treatment). The groups of mice treated with
mTHPC-invasomes containing 1% of the
terpene mixture prior to photoirradiation showed a significantly smaller (p<0.05) tumour increase compared to control groups (mice without any treatment and mice only photoirradiated).