Pharmaceutical diketopiperazine compounds

A diketopiperazine of formula (I), wherein each of R 7 and R 8 which may be the same or different, is hydrogen or a nitro group; Y is (a), -O- or -S-, wherein each of R 9 and R 10 , which may be the same or different, is hydrogen or a nitro group; n is 0, 1 or 2; m is an integer of 1 to 6; each R 6 , which may be the same or different, is a C 1 -C 6 alkyl group; and X is selected from (i) a phenyl group of formula (b); (ii) a heterocyclic ring selected from furan, thiophene, pyridine, quinoline and indole; (iii) a C 1 -C 6 alkyl group, a 2,3-methylenedioxyphenyl group or a 3,4-methylenedioxyphenyl group; and (iv) a group -(CH 2 ) p -Z, wherein p is 0 or an integer of 1 to 4 and Z is a cyclohexyl group substituted by one or more C 1 -C 6 alkyl and the salts and esters thereof; have activity as inhibitors of plasminogen activator inhibitor.