Peptidic compounds

A compound of formula I(a)

• or pharmaceutically acceptable salts thereof,
• wherein
• Q1 and Q2 are each independently selected from hydrogen, C1-C12alkyl, C3-C6cycloalkyl, C1-C12alkyloxy, nitro, halogen, hydroxyl, amino, mono or dialkylamino, carboxylic acid or a salt or ester thereof, sulphonic acid or a salt or ester thereof, phosphoric acid or a salt or ester thereof, carboxamide, sulphonamide and phosphoramide wherein each C1-C12alkyl, C3-C6cycloalkyl, or C1-C12alkyloxy is optionally substituted with hydroxyl, amino, carboxylic acid or a salt or ester thereof, sulphonic acid or a salt or ester thereof, phosphoric acid or a salt or ester thereof, carboxamide, sulphonamide or phosphoramide;
• B is selected from —O—, —S—, —S(O)—, —S(O)2—, —NH—, and —N(C1-C6alkyl)-;
• R1 is selected from hydrogen, C1-C12alkyl, C1-C6alkylC3-C6cycloalkyl, C1-C6alkylC6-C10aryl, C2-C6alkenyl, C2-C6alkynyl, and a polyoxyalkylene having from 2 to 6 carbon atoms, and when B is —S—, —S(O)—, —S(O)2—, —NH— or —N(C1-C6alkyl)-then R1 may be hydroxyl;
• V is a linker group selected from —O—, —O-L-C(O), —O-L-NR6—, —C(O)—, —NR6—, —S(O)—, —S(O)2—, —O-L-S(O)—, —S(O)2-L-C(O)—, —S(O)2-L-NR6—, and P(O)2O—;
• wherein L is selected from C1-C12alkyl, C2-C8alkenyl, C3-C6cycloalkyl, polyoxyalkylene having from 2 to 6 carbon atoms, C6-C10aryl and C1-C6alkylC6-C10aryl;
• and
• wherein R6 is selected from H and C1-C12alkyl;
• A1 and A2 are the same or different and are basic amino acid residues wherein each basic amino acid residue has a side chain comprising an amino group or an amino group substituted on the nitrogen with up to two substituents and wherein said amino group or substituted amino group is capable of carrying a positive charge at physiological pH;
• each of S1 and S2 are absent;
• S3 is an independently selected amino acid residue;
• and
• T is absent or selected from —C(O)R8, —C(O)OR8, —OR8, —NHR8, NHOR8, —NH—C6aryl-CO—R8, —NH—C6aryl-CO—NHR8, —NH—C6aryl-CONHOR8, —NH—C6aryl-CONHOH, —C(O)NHR8, —(NH)—SO2C6aryl, and —(NH)COR8, or T forms a carboxylate isostere, optionally substituted with R8, which replaces the carboxylic acid group of the amino acid to which T is connected;
• wherein R8 is selected from hydrogen, C1-C12alkyl, C1-C6alkylC6-C10aryl, C1-C6alkylC3-C6cycloalkyl, C2-C6alkenyl and C2-C6alkynyl;
• and
• wherein when T is connected to the C-terminus of an amino acid residue then the carbonyl group of the amino acid residue may be reduced to methylene.