β-Cyclodextrin-poly (β-Amino Ester) Nanoparticles Are a Generalizable Strategy for High Loading and Sustained Release of HDAC Inhibitors

Therapeutic development of histone deacetylase inhibitors (HDACi) has been hampered by a number of barriers to drug delivery, including poor solubility and inadequate tissue penetration. Nanoparticle encapsulation could be one approach to improve the delivery of HDACi to target tissues; however, effective and generalizable loading of HDACi within nanoparticle systems remains a long-term challenge. We hypothesized that the common terminally ionizable moiety on many HDACi molecules could be capitalized upon for loading in polymeric nanoparticles. Here, we describe the simple, efficient formulation of a novel library of β-cyclodextrin-poly (β-amino ester) networks (CDN) to achieve this goal. We observed that network architecture was a critical determinant of CDN encapsulation of candidate molecules, with a more hydrophobic core enabling effective self-assembly and a PEGylated surface enabling high loading (up to ∼30% w/w), effective self-assembly of the nanoparticle, and slow release of drug into aqueous media (up to 24 days) for the model HDACi panobinostat. We next constructed a library of CDNs to encapsulate various small, hydrophobic, terminally ionizable molecules (panobinostat, quisinostat, dacinostat, givinostat, bortezomib, camptothecin, nile red, and cytarabine), which yielded important insights into the structural requirements for effective drug loading and CDN self-assembly. Optimized CDN nanoparticles were taken up by GL261 cells in culture and a released panobinostat was confirmed to be bioactive. Panobinostat-loaded CDNs were next administered by convection-enhanced delivery (CED) to mice bearing intracranial GL261 tumors. These studies confirm that CDN encapsulation enables a higher deliverable dose of drug to effectively slow tumor growth. Matrix-assisted laser desorption/ionization (MALDI) analysis on tissue sections confirms higher exposure of tumor to drug, which likely accounts for the therapeutic effects. Taken in sum, these studies present a novel nanocarrier platform for encapsulation of HDACi via both ionic and hydrophobic interactions, which is an important step toward better treatment of disease via HDACi therapy.

Abstract 5023: A 3D perfusable platform for high-throughput screening diverse racial/ethnic prostate cancer specimens

Prostate cancer (PCa) incidence and mortality in African American men is more than 1.5 times greater than men of other races/ethnicities (i.e., Caucasian, Hispanic, American Indian/Alaska Native, Asian/Pacific Islander) in the United States. While elucidating the underlying mechanisms for this cancer health disparity is critical to patient treatment and improved patient outcome, currently, there are no in vitro models available to adequately recapitulate the PCa tumor microenvironment (TME) and aid in this effort. Advanced in vitro culture conditions, such as extended ex vivo culture of patient-derived xenografts (PDXs), 3-dimensional (3D) culture of cells within a defined extracellular matrix (ECM), miniaturization to formats compatible with high-throughput screening (HTS), controlled media perfusion, and co-culture of cancer, stroma, and endothelium, are key elements for improving PCa study, but few systems include two or more of these features. We have optimized culture conditions of a 3D in vitro model system, the OncoPlate, which mimics the PCa TME. In the OncoPlate, cells are seeded in engineered HyStem® hyaluronic acid (HA)-enriched hydrogels, optionally modified with migration-permissive peptides to mimic the tumor ECM. PDX-derived PCa cells are seeded in 3D in MIMETAS' microfluidic OrganoPlate® platform and co-cultured with stromal fibroblasts and endothelial blood vessel mimics under continuous perfusion. We predict that this engineered “tumor-on-a-chip” will better predict patient responses and, by incorporating PCa cells from patients with diverse racial backgrounds, support cancer health disparity research. Here we report culture of several PDX-derived PCa models of diverse racial origin cultured in our OncoPlate format. Live/dead staining followed by automated high content fluorescence imaging was utilized at various time points to characterize viability and growth rate of each model. Immunofluorescent staining for PSA (PCa cells), FSP (cancer associated fibroblasts), and VE-cadherin (endothelial cells) was used to display phenotype and health of each cell type in the culture over a week and formation of 3D structures characteristic of prostate cancer histology. Studies are ongoing to screen each model with a panel of chemotherapeutic drugs for which in vivo mouse PDX response data is available with the goal to improve predictive accuracy by using our perfusable OncoPlate PCa models.

Citation Format: Lindsey Sablatura, Kristin M. Bircsak, Mary C. Farach-Carson, Nora Navone, Peter Shepherd, Thomas Zarembinski, Pamela E. Constantinou, Anthony Saleh, Daniel A. Harrington. A 3D perfusable platform for high-throughput screening diverse racial/ethnic prostate cancer specimens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5023.