Antineoplastic activity of bone-targeted nanoparticles loaded with doxorubicin

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ABSTRACTS / Bone 42 (2008) S17–S110

creatinine, serum urea, or urinary excretion of enzymes or proteins). When administered repeatedly the risk of cumulative renal damage is expected to be related to the residual tissue concentration i.e. the amount of bisphosphonate remaining in the kidney from the previous dose. The terminal tissue half-life of ibandronate was determined as 24 days which is about consistent with the treatment interval of 3–4 weeks in the oncology indication. Modeling of tissue concentrations predicts that there should be no relevant accumulation in the kidney when ibandronate is given every 3 weeks. This was experimentally confirmed in a controlled 25-week study of repeated dosing every 3 weeks: Sub-clinical renal damage after a single dose of 1 mg/kg ibandronate did not accumulated to clinicallyrelevant nephrotoxicity. In conclusion, ibandronate has not only a high safety margin based on single doses but also a very low risk of cumulative renal toxicity when given intermittently due to a favourable short renal tissue half-life. Dr. Thomas Pfister; Salary; Employed at F. Hoffmann-La Roche Ltd, pre-clinical research and development. doi:10.1016/j.bone.2007.12.204

195 Antineoplastic activity of bone-targeted nanoparticles loaded with doxorubicin Manuela Salerno a, Sofia Avnet a, Caterina Fotia a, Elisabetta Cenni a, Donatella Granchi a, Francesco Castelli c, Dorotea Micieli c, Rosario Pignatello c, Armando Giunti a,b, Nicola Baldini a,b a Pathophysiology Lab, Istituti Ortopedici Rizzoli, Bologna, Italy b Department of Orthopaedic Surgery, Istituti Ortopedici Rizzoli, Bologna, Italy c Department of Pharmaceutical Sciences, University of Catania, Catania, Italy Bone is the third most common site of incidence of metastasis from different primary tumors, and bone cancer is associated with a high mortality rate. Current therapeutic strategies are unfortunately not effective on the progression of the tumor, and cause a range of systemic side effects. Biocompatible nanocarriers are being investigated as a new therapeutic tool that is able to transport anticancer drugs to specific targets meanwhile reducing the systemic toxicity associated with free drug distribution through the body. The aim of this study was to test the effectiveness of nanoparticles (NPs) engineered to feature a high affinity to bone and loaded with doxorubicin (DXR). NPs were obtained by binding alendronate to PLGA, characterized for their chemical–physical properties and biocompatibility, and then loaded with DXR. The in vitro study was performed on six human cell lines, considered as representative of the spectrum of bone tumors, including osteosarcoma (Saos-2, U2 OS), renal adenocarcinoma (ACHN), breast adenocarcinoma (MDA-MB231, MCF7), and neuroblastoma (SH-SY5Y). To analyze the uptake of the NPs, the cells were observed by confocal microscopy after incubation with the free or loaded DXR. To analyze the antineoplastic effects, the percentage of growth

inhibition was determined after incubation with free or loaded DXR. All the cell lines were able to selectively incorporate both DXR loaded NPs and free DXR. Selective nuclear uptake of the drug, typical of sensitive cells, was observed after 30’ of exposure. The cell lines were sensitive to free DXR, as confirmed by growth inhibition after exposition to the free DXR. NPs-loaded DXR was effective at the equivalent concentration as free DXR. In conclusion, NPs loaded with DXR were able to inhibit cell proliferation in vitro at the same conditions as free DXR. doi:10.1016/j.bone.2007.12.205

196 In vivo effects of zoledronic acid on peripheral γ/δ T lymphocytes in early breast cancer patients Daniele Santini, Federico Martini, Maria Elisabetta Fratto, Sara Galluzzo, Bruno Vincenzi, Chiara Agrati, Federica Turchi, Paola Piacentini, Laura Rocci, Giuseppe Tonini, Fabrizio Poccia Medical Oncology, University Campus Bio-Medico, Rome, Italy Infectious Diseases, National Institute for Lazzaro Spallanzani, Rome, Italy Introduction: Amino-bisphosphonates are potent activators of human γ/δ T cells both in vitro and in vivo. We conducted an observational perspective study aimed to evaluate immunomodulating properties of a single-dose of zoledronic acid on γ/δ T cells in a selected patient subset. Material and methods: 23 disease-free breast cancer patients with diagnosis of osteopenia during inhibitor aromatase treatment received a single-dose (4 mg) of zoledronic acid. Blood samples were obtained before ZA infusion, and 7, 28, 56, 90 and 180 days after. Kinetics of different γ/δ T cells subsets were determined by flow cytometry, as well as γ/δ T cells in vitro response to phosphoantigens. Results: A significant decrease of Naïve Vδ2 T lymphocytes after 180 days (p b 0,01) and a significant progressive decrease of Central Memory subset after 28 (p b 0,05), 90 (p b 0,01) and 180 days (p b 0,01) were observed. ZA induced also a significant reduction of Effector Memory Vδ2 T lymphocytes after 56 (p b 0,01) and 90 days (p b 0,05). Moreover, we observed that patients could be divided in two groups, according to γ/δ T lymphocyte kinetics: “responder patients” showing a significant decrease of γ/δ T lymphocytes total number, and “nonresponder patients” without any significant modulation of γ/δ T lymphocytes. By comparing the two different populations observed during the in vivo study, no significant differences in term of IFN-gamma response by Vdelta2 T cells were recorded after in vitro phosphoantigen stimulation. Conclusions: We describe here for the first time a longlasting activation of effector subsets of γ/δ T lymphocytes in healthy patients after a single dose of ZA. Our results highlight the need to further investigate the clinical significance of the immunomodulating properties of aminobisphosphonates. doi:10.1016/j.bone.2007.12.206