Compounds for pdt

A tetrakis(hydroxyphenyl) chlorin, bacteriochlorin or isobacteriochlorin of formula (12), (13) or (14) or imino tautomer thereof,

• wherein n=1 to 3 and each substituent R the same or different may be a hydroxyl (OH) group itself free or substituted with a C1 to C12 alkyl or acyl group or otherwise derivatised, but in at least one and desirably more than one instance is of formula (15);
• where:
• (i) each X, the same or different is O, S;
• (ii) Y is O (carbamate or thiocarbamate link);
• (iii) A is a hydrocarbon group containing 2 to 40 carbon atoms, preferably 4 to 20 carbon atoms and very preferably 6 carbon atoms (this group may be branched or unbranched, cyclic or acyclic, saturated or unsaturated, aliphatic or aromatic);
• (iv) B is an optional group ((CH2)p—O)q where p=1 to 4;
• q=0,1
• (v) D is a poly(alkylene oxide), preferably polyethylene glycol, with an average molecular weight of at least 200 and not more than 40,000, preferably 750 to 20,000 and very preferably 2,000 to 5,000 Da;
• (vi) E is an alkyl or acyl group containing 1 to 12 carbon atoms, preferably a methyl group;
• and any pharmaceutically acceptable derivative of such chlorin, bacteriochlorin or isobacteriochlorin as a salt with a mineral or other acid or a metal complex or a hydrate or other solvate.