title: Photodynamic therapy with WST09 (Tookad): quantitative studies in normal colon and transplanted tumours.
abstract: Photodynamic therapy (PDT) is attracting increasing interest for the safe destruction of localised tumours in a range of organs. However, most photosensitising drugs require a delay of hours to days between drug administration and light activation with skin photosensitivity that may last for weeks. WST09 (Tookad) is a new faster acting photosensitiser that clears within a few hours. In normal rat colon, after sensitisation with an intravenous bolus of WST09, light was delivered to a single point on the mucosa and the extent of PDT necrosis measured 3 days later. The lesion diameter was greatest with the highest dose of drug and light and the shortest drug light interval (DLI), falling rapidly with a DLI more than 5 min. In tumours transplanted subcutaneously or into the colon, the extent of necrosis only started falling with a DLI greater than 15 min, suggesting a possible window for tumour selectivity. Histological changes 3 days after PDT were essentially the same as those seen with longer acting photosensitisers. The lesion dimensions were comparable to the largest ones seen with other photosensitisers under similar experimental conditions. We conclude that WST09 is a powerful photosensitiser that produces PDT effects similar to those seen with longer acting drugs, but with the major advantages of a short DLI and rapid clearance.
authors.affiliation: National Medical Laser Centre, Academic Division of Surgical Specialities, Royal Free and University College Medical School, University College London, London, United Kingdom.
authors.forename: Josephine H
authors.initials: JH
authors.lastname: Woodhams
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: MacRobert
authors.forename: Marco
authors.initials: M
authors.lastname: Novelli
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Bown
mesh_terms: D000818:Animals; D001429:Bacteriochlorophylls / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D003110:Colonic Neoplasms / Q000188:drug therapy*; D007275:Injections, Intravenous; D009336:Necrosis; D009374:Neoplasms, Experimental; D010778:Photochemotherapy / Q000379:methods; D010787:Photosensitivity Disorders; D051381:Rats; D017208:Rats, Wistar; D012878:Skin Neoplasms / Q000188:drug therapy
chemical_list: D001429:Bacteriochlorophylls; C456120:palladium-bacteriopheophorbide