In the same way as antibodies, peptides are molecules composed by aminoacids covalently linked each other. Peptides are short proteic segments that could have ample spectrum of biological action, including antitumoral activity. Generally, a bioactive peptide could recognize specifically a given cellular target, such as a receptor present in the plasma membrane, activating a biochemical path that culminates in cellular death by apoptosis or necrosis. Alternatively, certain peptides could be internalized in the host cells and exert a cytotoxic effect by means of other cytosolic components. A peptide could even promote an indirect antitumoral effect by means of angiogenesis inhibition or by activation of an immune response against tumoral cells.
Peptides could be chemically synthesized and modified in a way to improve their stability and in vivo activity. Peptide synthesis in industrial scale and clinical grade quality is also viable, favoring their therapeutic utilization. For these reasons, bioactive peptides integrate an important new class of drugs, which has attracted large interest from part of the pharmaceutical industry. Currently, there are about 50 peptides being utilized worldwide for the treatment of different infirmities.