A macrocyclic peptidomimetic molecule for use in the treatment of cancer in a subject, this macrocyclic peptidomimetic molecule having the structure of Formula: wherein: each A, C, and D is independently a natural or non-natural amino acid; B is a natural amino acid, non-natural amino acid, an amino acid comprising at least one additional methylene groups between the amino and carboxyl group, an amino acid comprising an amino group which is a secondary or tertiary amine, an amino acid comprising a carboxy group replaced by an ester, [-NHN(R 3)C -], [-NH-L 3 -CO-], [-NH-L 3 -SO 2 -], or [-NH-L 3 -]; Y is -NH-, -N(R 4)-, -NHN(R 4)-, -NH-O-, -O-, or -S-; L 1, L 2, and L 3 are independently aliphatic, aryl, substituted aliphatic, substituted aryl, heteroatom-containing aliphatic, heteroatom-containing aryl, substituted heteroatom-containing aliphatic, substituted heteroatom-containing aryl group, unsubstituted or substituted with R 7; R 1, R 2, R 3, R 4, and R 5 are independently -H, aliphatic, substituted aliphatic, aryl, or substituted aryl groups; each R 7 is independently -H, an aliphatic, substituted aliphatic, an aryl, and a substituted aryl group; x is an integer from 0-10; y is an integer from 0-10; z is an integer from 0-10; w is an integer from 1-1000; x+y+z is at least 3; and wherein the macrocycle-forming linker [-L1-Z-L2-Y-] is selected from a group of macrocycle-forming linkers consisting of: wherein the symbol indicates an ortho-, meta- or para-disubstituted phenyl ring; 'm' and 'n' are each independently an integer number ranging from 1 to 10; and each R' is independently -H or -CH 3; and wherein the macrocyclic peptidomimetic molecule comprises an amino acid sequence which is at least 80% identical to an amino acid sequence selected from a group consisting of the amino acid sequences of SEQ ID NOS. 1 through 37, or is an amino acid sequence selected from a group consisting of the amino acid sequences of SEQ ID NOS. 1 through 10. each A, C, and D is independently a natural or non-natural amino acid; B is a natural amino acid, non-natural amino acid, an amino acid comprising at least one additional methylene groups between the amino and carboxyl group, an amino acid comprising an amino group which is a secondary or tertiary amine, an amino acid comprising a carboxy group replaced by an ester, [-NHN(R 3)C -], [-NH-L 3 -CO-], [-NH-L 3 -SO 2 -], or [-NH-L 3 -]; Y is -NH-, -N(R 4)-, -NHN(R 4)-, -NH-O-, -O-, or -S-; L 1, L 2, and L 3 are independently aliphatic, aryl, substituted aliphatic, substituted aryl, heteroatom-containing aliphatic, heteroatom-containing aryl, substituted heteroatom-containing aliphatic, substituted heteroatom-containing aryl group, unsubstituted or substituted with R 7; R 1, R 2, R 3, R 4, and R 5 are independently -H, aliphatic, substituted aliphatic, aryl, or substituted aryl groups; each R 7 is independently -H, an aliphatic, substituted aliphatic, an aryl, and a substituted aryl group; x is an integer from 0-10; y is an integer from 0-10; z is an integer from 0-10; w is an integer from 1-1000; x+y+z is at least 3; and wherein the macrocycle-forming linker [-L1-Z-L2-Y-] is selected from a group of macrocycle-forming linkers consisting of: wherein the symbol indicates an ortho-, meta- or para-disubstituted phenyl ring; 'm' and 'n' are each independently an integer number ranging from 1 to 10; and each R' is independently -H or -CH 3; and