The present invention provides use of compounds which are polyunsaturated fatty acid (PUFA) derivatives of formula (I), in the form of racemates, stereoisomers or mixtures of stereoisomers, or pharmaceutically acceptable salts, or solvates thereof, wherein -AIk- is -(CH2)4-CH(OR2)-[trans]CH=CH-[cis]CH=CH-, -(CH2)4-[cis]CH=CH- [trans]CH=CH-CH(OR2)-, -CH(OR2)-[trans]CH=CH-[cis]CH=CH-CH2- [cis]CH=CH-(CH2)3-, -(CH2)3-CH(OR2)-[trans]CH=CH-[cis]CH=CH-CH2- [cis]CH=CH-, or -(CH2)3-[cis]CH=CH-CH2-[cis]CH=CH-[trans]CH=CH- CH(OR2)- R1 is a hydrogen atom or R1 is a C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C6-C10 aryl, 5- to 10-membered heteroaryl, C3-C7 carbocyclyl or 5- to 10-membered heterocyclyl group or R1 is a group of formula -CH2-CH(OR3)-CH2-(OR4), wherein R3 and R4 are each independently hydrogen atoms or -(C=O)-R6, wherein R6 is an aliphatic group having from 3 to 29 carbon atoms or R1 is a group of formula -(CH2OCH2)mOH, wherein m is an integer of from 1 to 200 or R1 is a drug moiety each R2 is the-same or different- and each independently represents a hydrogen atom or a group -(C=O)-R5, wherein R5 is a C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C6- C10 aryl, 5- to 10-membered heteroaryl, C3-C7 carbocyclyl or 5- to 10-membered heterocyclyl group, or R5 is an aliphatic group having from 3 to 29 carbon atoms, or R5 is a drug moiety or a group of formula -(CH2OCH2)nOH, wherein n is an integer of from 1 to 200 or a drug moiety and wherein said alkyl, alkenyl, alkynyl and aliphatic groups are the same or different and are each unsubstituted or substituted with 1, 2 or 3 unsubstituted substituents which are the same or different and are selected from halogen atoms and C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 haloalkyl, C2-C4 haloalkenyl, C1-C4 haloalkoxy, C2-C4 haloalkenyloxy, hydroxyl, -SR, and -NRR" groups where R and R" are the same or different and represent hydrogen or unsubstituted C1-C2 alkyl said aryl, heteroaryl, carbocyclyl and heterocyclyl groups are the same or d
