PSMA-Targeted Stably Linked “Dendrimer-Glutamate Urea-Methotrexate” as a Prostate Cancer Therapeutic

One of the important criteria for achieving efficient nanoparticle-based targeted drug delivery is that the drug is not prematurely released at off-target sites. Here we report the preclinical evaluation of a serum-stable dendrimer-based drug conjugate capable of actively targeting into prostate cancer (PC) cells, delivered through the prostate-specific membrane antigen (PSMA). Multiple molecules of PSMA-binding small molecule glutamate urea (GLA; targeting agent) and the drug methotrexate (MTX) were conjugated to generation 5 PAMAM dendrimer (G5) through Cu-free “click” chemistry. The GLA was conjugated through a stable amide bond, and the MTX was conjugated either through ester (Es)- or amide (Am)-coupling, to generate G5-GLAm-(Es)MTXn and G5-GLAm-(Am)MTXn, respectively. In serum-containing medium, free MTX was slowly released from “G5-GLAm-(Es)MTXn”, with ∼8% MTX released from the dendrimer in 72 h, whereas the MTX on G5-GLAm-(Am)MTXn was completely stable. The G5-GLAm-(Am)MTXn bound and internalized i...