Table 1: Comparison of recent, improved targeted delivery systems.

NP* typeIncrease to NT**Decrease to NT***Efficacy of targeted delivery system

BIVs + small molecules + reversible masking200-foldNoneComplete elimination of aggressive, orthotopic pancreatic cancers after 5 iv injections administered once a week [9]
RTNs with endosomally cleavable PEG2-foldNone75% reduction in subcutaneous neuroblastoma tumor size after 7 iv injections administered every 48 h [10, 11]
MEND + pH-sensitive fusogenic peptide or a cell penetrating peptide + cleavable PEGNone2-foldNone reported [12, 13]
FRT + cleavable PEG1-foldNoneNone reported [14]
Copolymers + cleavable PEGNoneNoneNone reported [15]
Liposomes + cell penetrating peptide + cleavable PEG1.3-foldNoneNone reported [16, 17]

*Nanoparticle (NP).
**Nontargeted (NT); increased delivery of the targeted NP to the target compared with the corresponding nontargeted formulation.
***Nontargeted (NT); decreased delivery of the targeted NP to the target compared with the corresponding nontargeted formulation.