Sub Topic | Secondary Topic: Drug Delivery - Pharmaceutical Technologies (Small Molecule) - Formulation | Nanotechnology
Authors: Andrew Gdowski, University of North Texas Health Science Center (Main Author); Amalendu Ranjan, University of North Texas Health Science Center (Presenting Author); Marjana Sarker, University of North Texas Health Science Center; Jamboor Vishwanatha, University of North Texas Health Science Center
Presenting Author: Amalendu Ranjan
Purpose: Bone metastatic prostate cancer treatments remain a challenge despite an increasing number of newer drugs being approved in recent years. The major challenge for improved treatment outcomes for bone-metastatic prostate cancer originates from the fact that the drugs are unable to reach the bone microenvironment and hence are not able to elicit desired response. These metastatic lesions are difficult to treat and often result in off target cytotoxicity from current chemotherapeutics. Limitations also exist in the drugs that are approved which provide no overall survival benefits or quality of life. We have engineered a novel targeted nanotherapeutic system to target the bone microenvironment in an effort to more efficiently deliver chemotherapeutics, cabazitaxel, to the site of metastasis. The amino-bisphosphonate, alendronate, was used as the bone targeting moiety on the surface of the nanoparticles. The objective of this approach is to increase therapeutic payload at the site of bone metastasis to achieve an improved therapeutic index thereby limiting off-target side effects.
Methods: Nanoparticles (NPs) of poly(lactic-co-glycolic acid) were formulated using a modified water-in-oil-in-water double emulsion solvent evaporation technique followed by binding of alendronate to the surface of the NP using our patented linker technology. Following formulation, we characterized the NPs for size and zeta potential using dynamic light scattering. Encapsulation efficiency, drug loading and release kinetics of Cabazitaxel from the NPs were determined and optimized by quantification with HPLC analysis. In vitro cell viability studies were performed on C4-2B and PC3 prostate cancer cell lines. Ex vivo bone binding studies were used to test nanoparticle affinity for hydroxyapatite structure. Three diemnsional prostate cancer spheroids were generated and utilized to test NP penetration and efficacy in a 3D model which represented the in vivo real-tumor scenario. To determine efficacy of the NPs, In vivo tumor regression studies were carried out with male athymic nude mice implanted with intraosseous tumors consisting of PC3-luciferase cells. After bone tumors were established for 1 week, mice were treated via tail vein injection with either saline, free cabazitaxel, non-targeted NPs, or targeted NPs for one month (starting n=6 per group). Response was measured with in vivo bioluminescence imaging, tumor limb weight at conclusion of experiment, and mouse x-ray monitoring. In addition, animal behavior experiments were performed on all treatment groups to assess functional status through gait analysis. Pain was accessed through von frey filament assay in the earlier mentioned groups.
Results: Our NPs were successfully formulated to mean size of 236 nm with a Polydispersity Index of 0.120. Highest encapsulation of cabazitaxel into nanoparticle was determined at 55.8% with a drug loading of 3.7%. Release kinetics showed a strong burst phase release over the first 8 hours and subsequent sustained release up to 72 hours. Ex vivo bone binding experiment showed targeted NP had a 4-fold increase in binding to bone at 6 hours and an 8-fold increase in bone binding at 72 hours compared to non-targeted NP. In vitro cell viability and 3D spheroid experiment results showed our targeted NPs were able to penetrate the spheroid though the difference between targeted and non-targeted NPs were not found to be statistically significant. Tumor efficacy studies showed targeted NP and non-targeted NP had a statistically significant overall reduction in tumor measured by bioluminescence (P value < 0.005). Interestingly, mice treated with targeted NP had no bone lesions on x-ray, whereas, 100% of mice in saline group, 100% of mice in cabazitaxel group, and 33% of mice in non-targeted NP group had bone lesions. Gait analysis didn’t show a statistically significant difference between groups. However, von frey assay showed a significant reduction in relative response in the targeted NP group (P value < 0.005).
Conclusion: Our results show that our bone targeted NP system offers successful delivery of the payload at the desired site. We have shown that targeted NPs help maintain bone structure in tumor burdened limbs in addition to decreasing tumor size. We have also shown that these targeted NPs reduce the relative response to von frey filament pain stimulation in the tumor limb. Our bone targeted NP system can serve as a novel therapeutic platform for developing improved treatments for bone metastatic prostate cancer wherein not only do we show decrease in tumor burden but also improve the quality of life of such patients.
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