Synthesis and Biological Evaluation of New Bisphosphonate- Dextran Conjugates Targeting Breast Primary Tumor Evelyne Migianu-Griffoni,* ,† Ime ̀ ne Chebbi, † Souad Kachbi, † Maelle Monteil, † Odile Sainte-Catherine, † Fre ́ de ́ ric Chaubet, ‡ Olivier Oudar, ‡ and Marc Lecouvey* ,† † Universite ́ Paris 13, Sorbonne Paris Cite ́ , Laboratoire de Chimie, Structure, Proprie ́ te ́ s de Biomate ́ riaux et d’Agents The ́ rapeutiques (CSPBAT), CNRS UMR 7244, 74, Rue Marcel Cachin F-93017 Bobigny, France ‡ Universite ́ Paris 13, Sorbonne Paris Cite ́ , Laboratoire BPC, INSERM U 698, 99, Avenue Jean-Baptiste Cle ́ ment F-93430 Villetaneuse, France * S Supporting Information ABSTRACT: Bisphosphonates (BPs) have interesting anti- tumor effects as well in vitro as in vivo, despite their poor bioavailability in the organism after oral ingestion. To overcome this problem and reduce drug doses and secondary effects, we report the chemical synthesis of new bioconjugates. They were built with a nitrogen-containing BP as the drug covalently coupled to the carboxymethyldextran. This polysaccharide was used as a carrier, in order to increase BP lifetime in bloodstream and to target tumor cells which have a strong affinity with dextran. The efficiency of our vectorization system was biologically proved in vitro and in vivo on mammalian carcinoma models in mice. ■ INTRODUCTION Bisphosphonates (BPs) are bone-targeting agents used for decades in the therapy of bone-related diseases such as osteoporosis and Paget ’ s disease. They mainly inhibit osteoclastic action on bone resorption binding to hydrox- yapatite crystals, the main component of bones. 1 They are synthetic analogs of inorganic pyrophosphate, an endogenous regulator of calcium homeostasis, with a P-C-P linkage instead of a P-O-P one. According to the chemical structure of the two side groups bearing by the central carbon atom, BPs can be distinguished in two classes: (i) the non- nitrogen-containing BPs, which induced apoptosis after metabolization in cytotoxic agents, and (ii) the nitrogen- containing BPs, more efficient than the previous ones, which suppress osteoclastic function by inhibition of mevalonate pathway enzymes as farnesyl pyrophosphate synthase. 2 Inhibition of this enzyme prevents the formation of farnesyl pyrophosphate and geranylgeranyl pyrophosphate. These two isoprenoid ways involved in the cholesterol synthesis are required for the cellular survival and used for the prenylation of proteins as small GTPases including Ras proteins that regulate the proliferation, invasive properties, and proangiogenic activity of human tumor cells. 3 More recently, BPs have shown interesting anticancer activity, 4 and now, they are commonly administered in the treatment of bone metastasis of various malignancies 5 such as breast, prostate, and colon cancer. Indeed, bone metastases increase osteolytic activity resulting in the release of growth factors that stimulate cancerous cell proliferation, and it is widely admitted that BPs can reduce skeletal morbidity (hypercalcemia, pain, pathologic fractures, surgery) for patients with breast cancer 6 and multiple myeloma, 7 for example. Moreover, aside from their direct action on osteoclasts, in vitro studies have also shown that BPs might directly inhibit the proliferation and induce the cell death of the cancer cells themselves, 8 in particular, in the case of breast tumors 9 as well as in prostate tumor cells, 10 melanoma 11 and epidermoid carcinoma, 12 osteosarcoma, 13 and myeloma. 14 At last, they could inhibit tumor angiogenesis. 15 Unfortunately, BPs are poorly absorbed by oral pathway and quickly eliminated from plasma after intravenous administra- tion due to renal excretion and accumulation in bone (about 55% of the administered dose in the case of zoledronate, for example). 16 This therapeutic drawback is due to poor lipophilicity, a highly charged nature, and a propensity to chelate divalent cations (Ca 2+ , Mg 2+ ) in the gastrointestinal tract. BPs have also shown some side effects that could prevent their oral administration as esophagus inflammation, stomach irritation, or abdominal pain due to gastrointestinal toxicity, as well as their intravenous use inducing bone pain, myalgias and fevers, rare ophthalmologic side effects, 17 renal toxicity, 18 and rare osteonecrosis of the jaw in patients treated in cancer IV therapy. 19 Received: July 17, 2013 Revised: November 25, 2013 Published: January 8, 2014 Article pubs.acs.org/bc © 2014 American Chemical Society 224 dx.doi.org/10.1021/bc400317h | Bioconjugate Chem. 2014, 25, 224-230