Garayoa et al. showed that the incorporation of a β-alanine-β-alanine (βAla-βAla) linker into a human tumor targeting bombesin peptide radiopharmaceutical (Figure 9) resulted in a two-fold increase in metabolic stability against proteolytic degradation and no decrease in receptor affinity when compared to the unmodified structure (sans linker) in studies performed using in vitro tumor cell cultures [81]. Here, GRP is linked to neoplasm.