A compound having the formula (I) R1-COOH. R1 is an alkyl or alkenyl group having a C7-11 backbone, optionally branched with a C1-6 alkyl group at any C position in the backbone, or a pharmaceutically acceptable salt, amide or ester thereof. The backbone of the alkyl or alkenyl group, and/or the branched alkyl groups, are optionally interrupted by one or more heteroatoms, provided that when R1 is an alkyl group having a C7 backbone, the branching does not consist only of a hexyl group at the α carbon of R1, or only of a methyl group at the γ carbon of R1, or of only single methyl groups at both the β and ω-1 carbons of R1, and provided that when R1 is an alkyl group having a C8 dor C11 backbone, the branching does not consist only of a propyl group at the α carbon of R1.
