Fabrication and Characterization of Panobinostat Loaded PLA-PEG Nanoparticles

Medulloblastoma is the most common malignant pediatric brain cancer and is classified into four different subgroups based on genetic profiling: sonic hedgehog (SHH), WNT, Group 3 and 4. Changes in gene expression often alter the progression and development of cancers. One way to control gene expression is through the acetylation and deacetylation of histones. More specifically in medulloblastoma SHH and Group 3, there is an increased deacetylation, and histone deacetylase inhibitors (HDACi) can be used to target this change. Not only can HDACi target increases in deacetylation, they are also known to induce cell cycle arrest and apoptosis. The combination of these factors has made HDACi a promising cancer therapeutic. Panobinostat, a hydrophobic, small molecule HDACi was recently identified as a potent molecule of interest for the treatment of medulloblastoma. Furthermore, panobinostat has already been FDA approved for treatment in multiple myeloma and is being explored in clinical trials against various solid tumors. The laboratory is interested in developing strategies to encapsulate panobinostat within nanoparticles composed of the biodegradable and biocompatible polymer poly(lactic acid)-poly(ethylene glycol) (PLA-PEG). Nanoparticles are formed by single emulsion, a process in which hydrophobic drugs can be trapped within the hydrophobic nanoparticle core. The goal was to determine if the molecular weight of the hydrophobic portion of the polymer, PLA, has an impact on loading of panobinostat in PLA-PEG nanoparticles. Nanoparticles formulated with PLA of varying molecular weight were characterized for loading, size, zeta potential, controlled release, and in vivo tolerability. The results of this work demonstrate that panobinostat loaded nanoparticles are optimally formulated with a 20:5kDa PLA-PEG, enabling loading of ~3.2 % w/w panobinostat within nanoparticles possessing an average diameter of 102 nm and surface charge of -8.04 mV. Panobinostat was released from nanoparticles in a potentially biphasic fashion over 72 hours. Nanoparticles were well tolerated by intrathecal injection, although a cell culture assay suggesting reduced bioactivity of encapsulated drug warrants further study. These experiments demonstrate that the molecular weight of PLA influences loading of panobinostat into PLA-PEG nanoparticles and provide basic characterization of nanoparticle properties to enable future in vivo evaluation.