Supramolecular drug carriers are designed to accumulate in tumors by passive targeting via the enhanced permeability and retention (EPR) effect. The conjugation of targeting moieties, as Folic acid (FA), results in receptor-mediated selective drug delivery. Here, we compare the in vitro and in vivo pharmacological activity of two drug delivery systems bearing doxorubicin (Dox) and folic acid. In the first approach, two pullulan (Pull)-based prodrugs of Dox were synthesized, distinguished by the presence or absence of FA as targeting moiety, namely Pull-PEG-FA-Dox and Pull-PEG-Dox1. The second drug delivery system is PEGylated liposomal doxorubicin (PLD, Doxil™) and its folate version obtained by ligand post-insertion into the commercial formulation (PLD-FA)2.
The specific binding of Pull-PEG-FA-Dox and PLD-FA to the folate receptor (FR) was demonstrated by a competition assay using [3H]FA on FR-overexpressing human cervical carcinoma KB cells. Receptor-mediated internalization and cellular trafficking were evaluated by following doxorubicin fluorescence using laser scanning confocal microscopy. Both folate-targeted systems showed a 5-fold increase in inhibition of proliferation of KB cells compared with the non-targeted carriers.
The drug delivery systems were able to reduce Dox-induced cardiotoxicity, after 15 mg/kg of Dox-equivalent dose. The mice treated with the free drug developed adverse remodeling, especially in the systolic phase, and impaired contractility reflected by impaired left ventricle ejection fraction.
We demonstrated an effective chemical protocol to conjugate FA to different DDS, maintaining the binding affinity of the ligand for the FR, and exploiting the targeting properties to promote the internalization of the carriers. The DDS are able to maintain the in vitro pharmacological activity of Dox on cancer cells and to reduce cardiotoxicity in vivo.
1. Scomparin A, et al. Eur J Pharm Sci 2011, 42:547-558
2. Gabizon A, et al. In: Targeted Drug Strategies for Cancer and Inflammation. Eds. Leamon and Jackman, Springer-Verlag, Heidelberg 2011: 217-247.
