A compound of Formula IV, or a pharmaceutically acceptable salt or solvate thereof: wherein: aa1 is a natural or non-natural amino acid residue； aa2 is a natural or unnatural amino acid residue, or is absent； wherein said aa1 and aa2 are each independently amino acid residues of Formula VI: wherein: R1 is selected from the group consisting of a substituted or unsubstituted group selected from C1-C12 alkyl, C2-C12 alkenyl, C2-C12 alkynyl , C3-C15 cycloalkyl； R2 is hydrogen R3 is hydrogen； or R3 is a link between two amino acid residues, when two amino acid residues are present； R4 is selected from the group consisting of H and a substituted or unsubstituted group selected from C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl； and n is 1, 2 or 3； wherein the term substituted when associated with any of the preceding groups refers to a group substituted in one or more positions with substituents selected from simple amino, mono and dialkylamino, mono and diarylamino, and alkylamino, acylamino including carbamoyl, and ureido, aminocarbonyl, mono and dialkylaminocarbonyl, cyano, azido, halogen, hydroxyl, nitro, trifluoromethyl, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, C1-C6 alkoxy, aryloxy, benzyloxy, benzyl, guanidino, imino and formyl； with the proviso that when R2 is H and R3 is H or a bond, then R1 is not a -CH2phenyl group.Un compuesto de Fórmula IV, o una de sus sales farmacéuticamente aceptables o solvatos: en donde: aa1 es un residuo de aminoácido natural o no natural； aa2 es un residuo de aminoácido natural o no natural, o está ausente； en donde dichos aa1 y aa2 son cada uno independientemente residuos de aminoácido de Fórmula VI: en donde: R1 se selecciona del grupo que consiste en un grupo sustituido o no sustituido seleccionado de alquilo C1-C12, alquenilo C2-C12, alquinilo C2-C12, cicloalquilo C3-C15； R2 es hidrógeno R3 es hidrógeno； o R3 es un enlace entre dos residuos de aminoácido, cuando están presentes dos resi
