ROLE OF DELIVERY VEHICLES FOR PHOTOSENSITIZERS IN THE PHOTODYNAMIC THERAPY OF TUMORS

The use of photosensitizing drugs associated with different types of d elivery vehicle has received strong interest within the field of the p hotodynamic therapy of tumours. Lipid-based delivery vehicles, such as liposomes and oil emulsions, allow the administration of water-insolu ble photosensitizers, widening the choice of photosensitizers potentia lly useful for treating tumours. In some cases, these delivery vehicle s increase the selectivity of tumour targeting by favouring photosensi tizer uptake in tumour tissue. However, a higher selectivity of tumour targeting could be obtained through the association of photosensitize rs with delivery vehicles which can interact preferentially or specifi cally with tumour cells. With this aim in mind, low-density lipoprotei ns (LDLs) and monoclonal antibodies, in particular, are regarded as th e most promising delivery systems for anticancer drugs. Some pharmacok inetic studies with LDL-associated photosensitizers have demonstrated a higher tumour uptake compared with the same photosensitizers deliver ed with other formulations. Monoclonal antibody-coupled photosensitize rs have been tested mainly in vitro, and have shown a high selectivity towards cells expressing specific antigens. Only a limited number of reports are available on the biodistribution of immunoconjugated photo sensitizers and on their selectivity in vivo, so that their importance for the selectivity of tumour targeting has not yet been defined. (C) 1997 Elsevier Science S.A.