PEGylated dendritic diaminocyclohexyl-platinum (II) conjugates as pH-responsive drug delivery vehicles with enhanced tumor accumulation and antitumor efficacy

Environmentally responsive peptide dendrimers loaded with drugs are suitable candidates for cancer therapy. In this study, we report the preparation and characterization of mPEGylated peptide dendrimer-linked diaminocyclohexyl platinum (II) (dendrimer-DACHPt) conjugates as pH-responsive drug delivery vehicles for tumor suppression in mice. The DACHPt has a molecular structure, is and activity closely related to oxaliplatin and was linked to dendrimer via N,O-chelate coordination. The products were pH-responsive and released drug significantly faster in acidic environments (pH 5.0) than pH 7.4. Consequently, the conjugates suppressed tumor growth better than clinical oxaliplatin® without inducing toxicity in an SKOV-3 human ovarian cancer xenograft. Through the systemic delivery of conjugates, 25-fold higher tumor platinum uptake at 36 h post-injection was seen observed due to the enhanced permeability and retention (EPR) effect thereby remarkably enhancing the therapeutic indexes of this small-molecule drug. Thus, the mPEGylated peptide dendrimer-linked DACH-platinum conjugates are novel potential drug delivery systems with implications in future ovarian cancer therapy.