Photosensitisers for PDT

Although there are many dyes which can photosensitise the production of singlet oxygen (see section 4.4.1), in PDT the first products of real interest came from haematoporphyrin. Subsequent, studies led to the haematoporphyrin derivatives HpD Stage 1 and Stage 11, which were found to be more active as PTD sensitisers as they localised preferentially in tumours. The first commercially available sensitiser, Photofrin, is based on processed material from HpD Stage 11, and is a complex mixture of monomeric, dimeric and oligomeric e.g. hexamer) porphyrins, in an 

second generation photosensitisers were needed to overcome these deficiencies and also to display the following characteristics  

The search for second generation sensitisers has yielded several leading candidates. The structures of some of those that are undergoing clinical trials are shown in Fignre 

Sensitiser (Company) Xmax/ nm (emaxj Singlet oxygen h( o,) Drug use/ mg kg- Light dose/ Treatment J cmr time/s Indicators Comments (US Approval) 

Photofrin (QLT) 628 (3000) 0.89 1.2-5 75-250 750-2500 Early treatment of bladder, lung, esophagus, cervix, stomach and mouth Palliative in later stages Skin phototoxicity (up to 4 weeks) is a problem (Approved, esophegal and lung) 

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