A compound according to formula below, or a pharmaceutically acceptable salt thereof: wherein: R 1 and R 2 independently represent alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkylcycloalkyl, alkylcycloalkenyl, alkenylcycloalkyl, alkenylcycloalkenyl, aryl, heteroaryl, alkylaryl, alkylheteroaryl, alkenylaryl or alkenylheteroaryl any of which groups may optionally be substituted by monocylic aryl or monocyclic heteroaryl; or R 1 and/or R 2 represents hydrogen; and wherein one or more carbon atoms of R 1 and/or R 2 not being part of an aryl or heteroaryl group are optionally replaced by a heteroatom selected from O, N and S p in which p represents 0, 1 or 2 and wherein one or more carbon atoms of R 1 and/or R 2 are optionally replaced by carbonyl; or R 1 and R 2 are joined to form a saturated or unsaturated heterocyclic ring containing the nitrogen atom shown and wherein one or more carbon atoms of said ring are optionally replaced by a heteroatom selected from O, N and S p in which p represents 0, 1 or 2 and wherein one or more carbon atoms of said ring are optionally replaced by carbonyl and which heterocyclic ring may optionally be fused to an aryl or heteroaryl ring; and wherein one or more carbon atoms of an R 1 and/or R 2 group may optionally be substituted by one or more halogen atoms; R 3 represents H or - x alkyl; R 4 represents H or OH; R 5 represents H, OH or =O; n represents a single or double bond save that when n represents a double bond R 4 represents H; m represents a single or double bond save that when m represents a double bond R 5 represents H; and x represents 0 or 1; including any tautomer thereof; or an isomer thereof in which the C26, 27 C=C bond shown as trans is cis; and including a methanol adduct thereof in which a ketal is formed by the combination of the C-53 keto,if present, and the C-15 hydroxyl groups and methanol. R 1 and R 2 independently represent alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkylcycloalkyl, alkylcycloalkenyl, alkenylcycloalkyl, alkenylcycloalkenyl, aryl, heteroaryl, alkylaryl, alkylheteroaryl, alkenylaryl or alkenylheteroaryl any of which groups may optionally be substituted by monocylic aryl or monocyclic heteroaryl; or R 1 and/or R 2 represents hydrogen; and wherein one or more carbon atoms of R 1 and/or R 2 not being part of an aryl or heteroaryl group are optionally replaced by a heteroatom selected from O, N and S p in which p represents 0, 1 or 2 and wherein one or more carbon atoms of R 1 and/or R 2 are optionally replaced by carbonyl; or R 1 and R 2 are joined to form a saturated or unsaturated heterocyclic ring containing the nitrogen atom shown and wherein one or more carbon atoms of said ring are optionally replaced by a heteroatom selected from O, N and S p in which p represents 0, 1 or 2 and wherein one or more carbon atoms of said ring are optionally replaced by carbonyl and which heterocyclic ring may optionally be fused to an aryl or heteroaryl ring; and wherein one or more carbon atoms of an R 1 and/or R 2 group may optionally be substituted by one or more halogen atoms; R 3 represents H or - x alkyl; R 4 represents H or OH; R 5 represents H, OH or =O; n represents a single or double bond save that when n represents a double bond R 4 represents H; m represents a single or double bond save that when m represents a double bond R 5 represents H; and x represents 0 or 1; including any tautomer thereof; or an isomer thereof in which the C26, 27 C=C bond shown as trans is cis; and including a methanol adduct thereof in which a ketal is formed by the combination of the C-53 keto,if present, and the C-15 hydroxyl groups and methanol.