Lymph directing prodrugs

A compound of the formula (I):

• wherein
• R1 and R2 independently represent H, or a residue of a C2-C28 fatty acid;
• —X—is selected from —O—, —NH—and —S—;
• —Y—represents an optionally substituted —C3-C20alkyl-, —C3-C20alkenyl- or —C3-C20alkynyl-group, wherein one or more of the carbon atoms in the alkyl, alkenyl or alkynyl group may be replaced with NH, S, O, a C5C8aromatic or aliphatic cyclic group or a C5-C8 aromatic or aliphatic heterocyclic group, provided that the alkyl, alkenyl or alkynyl group does not exceed a length equivalent to a linear C20alkyl group;
• represents a residue of a pharmaceutical agent;
• —L—is —X′—or —X′C(O)—;
• X′ is O, S, N, N(R4) or S(O)2NH;
• represents a single bond when X′ is O, S, N(R4) or S(O)2NH;
• or
• represents two separate bonds when X′ is N;
• —Z—is —C(O)—or —C(O)R3—when —L—is —X′—;
• or
• —Z—is absent when —L—is —X′C(O)—;
• R3 is a self-immolative group;
• and
• R4 is H or C1-C4alkyl;
• or
• pharmaceutically acceptable salts thereof.