Dendritic hexadecapeptide as a cathepsin B degradable carrier for delivery of HSP90 inhibitor

Biodegradable vehicles that degrade specifically at tumor sites are highly desirable since they can cause selective exposure of highly toxic drugs at tumor sites whereas keep the conjugates stable during blood circulation. Here, we evaluate the utility of a dendritic hexadecapeptide comprised of four arms, each having a tetrapeptide sequence recognized by an enzyme cathepsin B as a carrier system for heat shock protein 90 (HSP90) inhibitor geldanamycin (GDM). We report the synthesis of a carrier having GDM conjugated to the terminal end of each arm (>55% wt/wt drug). We further report the stability of the GDM containing peptidic dendrimer in various buffers and in the presence of serum along with its ability to release free drug in the presence of cathepsin B, the enzyme overexpressed in a variety of tumors. Using androgen-independent prostate cancer cell line (DU-145) we further demonstrate that the geldanamycin containing peptidic dendrimer has antiproliferative property similar to the free drug derivative.