3112 - Ligand-Directed Liposomal Carfilzomib as a Radiosensitizer for Non-Small Cell Lung Cancer

Purpose/Objective(s): Carfilzomib (CFZ) is an FDA approved proteasome inhibitor for treatment of refractory multiple myeloma (MM). Preclinical studies have demonstrated CFZ’s effectiveness on a variety of non-hematological malignancies including non-small cell lung cancer (NSCLC) and breast cancer. However, dose-limiting toxicities of CFZ have halted clinical expansion beyond MM. Given the limitations with current systemic administration, it is unlikely CFZ chemoradiotherapy would ever be adopted clinically in its current small molecule form. Aiming to address this need, this study aims to improve efficacy and systemic toxicity by using CFZ as a radiosensitizer and a liposomal delivery method. CFZ pretreatment will sensitize human NSCLC to radiotherapy and liposomal delivery of CFZ will improve efficacy and decrease toxicity in vivo compared to current clinical methods of CFZ administration. We also hypothesized that a pre-administration of clodronate liposomes will transiently suppress liver macrophage, a key player in the clearance of systemically administered nanoparticles and increase tumor uptake.

Materials/Methods: Liposomal CFZ was synthesized via thin film hydration method. For active tumor targeting and penetration, liposomes were functionalized with tLYP-1 peptide (CGNKRTR), a ligand with strong binding to neuropilin 1 (NRP-1), a receptor that is over expressed on a variety of malignant cells. Nanoparticle delivery was investigated with in vitro cellular uptake experiments (NSCLC A549 and H1975 cells, ATCC) as well as dose response assays. Radiosensitization was studied using clonogenic assay and ?-H2AX staining. An in vivo model of human NSCLC was used to determine preclinical efficacy. Athymic nude mice were intravenously injected with saline, standard CFZ, PEGylated liposomal CFZ or ligand-guided liposomal CFZ. A subsection of mice (n=20) was injected with clodronate liposomes 48 hours prior to the administration of CFZ liposomes (10 PEGylated and 10 targeted). From each subgroup, mice (n=5) were given 5Gy of radiation. Biodistribution studies included systemic administration of fluorescent liposomes in both targeted and non-targeted formulations as well as with and without clodronate liposome pretreatment.

Results: In vitro experiments demonstrated improved uptake for ligand-directed liposomes as well as CFZ mediated radiosensitization. The in vivo studies corroborated with the in vitro results. Clodronate liposomes transiently depleted liver macrophages allowing for increased tumor accumulation of liposomes.

Conclusion: CFZ liposomes were successfully synthesized and demonstrated active targeting and radiosensitizing capabilities. This is the first time CFZ has been used for radiosensitization. The application of CFZ liposomes as radiosensitizers may expand the clinical role of CFZ to a broad range of malignancies.