For example, Kim et al. developed theranosticagent 44 (Figure 18), composed of Dox linked to an albumin-binding maleimidemoiety through a cathepsin B-responsive peptide sequence (FRRG).241 Compared with the parent drug (Dox itself; t1/2 = 0.25 h), the maleimide moiety in the scaffoldwas found to improve the half-life (t1/2 = 3.1 h), presumably as a result of being bound to the plasma albumin.After presumed albumin-mediated passive tumor accumulation, theranostic 44 is activated by cathepsin B to release Dox inside the cancercells. Here, CTSB is linked to neoplasm.