Purpose: Since their discovery as antitumor agents, anthracycline drugs such as doxorubicin have remained mainstays as an important class of chemotherapy for the treatment of a wide range of cancers including pediatric malignancies like Ewing Sarcoma (EWS). Unfortunately, their usage is limited due to cumulative dose-dependent cardiotoxicity. Targeted drug delivery could be an important option to circumvent this problem.
Experimental design: Our laboratory has developed a novel reconstituted HDL drug delivery system comprised of Myristic acid conjugated Apo AI mimicking 5A peptide (Myr5A). We used a hydrophobic derivative of doxorubicin, N-Benzyladriamycin-14-valerate (AD198) to engineer formulations of Myr5A-AD198. Physico-chemical characterization including size, zeta potential and entrapment efficiency was determined. Cytotoxic effectiveness of this formulation was tested in Ewing Sarcoma cells A673 and Cardiomyocytes, H9c2 in 2D and 3D spheroid model using CCK-8 assays. Using Myr5A based formulation-containing BODIPY; mechanism of uptake of payload was demonstrated by imaging. In addition, we investigated Biodistribution and payload retention in EWS tumors in xenograft NOG mice with EWS tumor model.
Results: Formulation of the Myr5A-AD198 was stable and non-leaky with payload entrapment efficiency of 47.6 ± 3.2%. The nanoparticles were spherical with average size of 47 ± 12 nm as observed by transmission electron microscopy (TEM). Cytotoxicity assays demonstrated that IC50 values of Myr5A-AD198 formulation was 2.8 ± 0.4 times more effective than free AD198 in EWS cells. On the other hand, 3 times more dose was required for Cardiomyocytes with Myr5A-AD198 formulation as compared to free AD198. Blocking the Scavenger Receptor type B1 (SR-B1) receptors, resulted in inhibition of the uptake of payload in Myr5A formulation. Subcutaneous injection of Myr5A-IR 780 dye in xenograft NOG mice indicated the retention of payload for up to 72 hours in tumor.
Conclusion: These preclinical studies indicated a great translational potential of Myr5A-AD198 formulation for the treatment of EWS patients due to its selective uptake mechanism and cardio-protective effect. Longer retention of the drug in tumors as well as lower dose requirement compared to free drug gives an additional advantage. In future, the Myr5A based technology shows promise for personalized treatment options in EWS and other type of cancers as well.
Rutledge Cancer Foundation, Fort Worth, TX, Wheels for Wellness, Fort Worth, TX.
