Abstract: Tumor targeting units are disclosed which have a peptide sequence Cy—Y—G-F—X—W-G-Z-Cyy (SEQ ID NO: 25), or a pharmaceutically or physiologically acceptable salt thereof. Tumor targeting agents are also disclosed having at least one targeting unit, directly or indirectly coupled to at least one effector unit. Diagnostic or pharmaceutical compositions having at least one targeting unit or at least one targeting agent, and targeting units or targeting agents for the preparation of a medicament for the treatment of cancer related diseases (including cancer), especially for the treatment of colon/colorectal cancer or its metastases are also disclosed.

Abstract: The present invention relates to a method for synthesizing peptide conjugates comprising a functional peptide, cyclic by means of a lactam bridge; a sulfur-linker bound to said cyclic peptide, wherein said sulfur-linker comprises sulfur or a sulfur-reactive site. The invention further relates to a method for synthesizing peptide-effector conjugates. The invention also relates to peptide conjugates. Peptide conjugates according to the present invention have improved half-life and increased availability at the active site and they are useful in cell targeting and tumor diagnosis and therapy.