Esters of 5-aminolevulinic acid as photosensitizing agents in photochemotherapy

A compound for use in photochemotherapy or diagnosis, said compound being of formula I:

• R22N—CH2COCH2—CH2CO—OR1 (I)
• (wherein R1 represents an optionally substituted alkyl group other than an unsubstituted straight-chained alkyl;
• and
• R2 independently represents a hydrogen atom or an optionally substituted alkyl group) or a pharmaceutically acceptable salt thereof.

A compound of formula I:

• R22N—CH2COCH2—CH2CO—OR1 (I)
• (wherein
• R1 represents
• an optionally substituted branched C5-30 alkyl group, preferably a C6-9 alkyl group, comprising a straight chain C4-29 alkyl group, preferably a C4-8, more preferably a C5-8 (e.g C5 or C6) alkyl group, branched by substitution with one or more C1-6 alkyl groups, preferably C1 or C2, wherein said site of substitution is at C2 or a higher C atom, or
• a non-heteroaromatic aryl substituted alkyl group, preferably a C1 or C2 alkyl group, wherein said aryl group is substituted, especially preferably substituted by one or more alkyl (e.g. C1-2 alkyl), fluoro, chloro, nitro or trifluoromethyl groups, or
• an alkoxy substituted alkyl group, preferably a C1 or C2 alkyl group, wherein said alkyl group is substituted by a methoxy group;
• R2, each of which may be the same or different, represents a hydrogen atom or an optionally substituted alkyl group, e.g. a group R1;
• wherein said substituents are selected from hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, amino, aryl, nitro, oxo, fluoro, —SR3, —NR32 and —PR32 groups,
• and said alkyl group is optionally interrupted by one or more —O—, —NR3—, —S— or —PR3— groups;
• and
• R3 represents a hydrogen atom or C1-6 alkyl group) or a pharmaceutically acceptable salt thereof.