Investigators at Georgia Institute of Technology and the University of Texas-Houston Health Science Center have taken a closer look at these targeted nanocarriers and examined the relationships between circulation time, tumor targeting and therapeutic efficacy. In an article published in Nanotechnology the authors demonstrate that the incorporation of targeting ligands can have drastic effects on circulation times of liposomal nanocarriers (due to recognition and clearance by the immune system) thereby decreasing their ability to passively accumulate at the tumor site. Reductions in passive accumulation offset the advantages of targeting resulting in the absence of increased tumor uptake and therapeutic efficacy over comparable non-targeted formulations.

These findings have widespread implications for the design of nanocarrier formulations targeted to tumors, particularly those targeted to tumors with leaky vasculature, which benefit from prolonged circulation in the bloodstream. If the ability to passively accumulate to tumor is compromised by a reduction in circulation time due to targeting ligand incorporation, then targeting will be ineffective and treatment efficacy will be compromised. This report stresses the importance of considering the effects of targeting nanocarriers on circulation time when tailoring these formulations for specific applications.