Bisphosphonate conjugates and methods of making and using the same

#The present invention is directed to bisphosphonate compounds, and in particular, bisphosphonate conjugates that are useful in the treatment of soft tissues surrounding bone and bone-related diseases, such as bone cancer and osteoporosis.

#Bone degeneration diseases, including Paget's Disease and osteoporosis have proven difficult to treat because the mechanisms involved in the development and progression of these diseases are not well understood. Bisphosphonates are synthetic analogs of pyrophosphates characterized by a phosphorus-carbon-phosphorus backbone that renders them resistant to hydrolysis and are known to be useful in the treatment of these degenerative bone disorders. The chemical properties of the bisphosphonates vary based on different substitutions at the carbon atom of the phosphorus-carbon-phosphorus backbone.

#Bisphosphonates bind strongly to hydroxyapatite on the bone surface and act to reduce and inhibit the activity of osteoclasts; cells functioning in the absorption and removal of osseous tissue. The anti-resorptive effect of bisphosphonates is also mediated through effects on osteoblasts; cells that function in the production of bone. Thus, biophosphonates are used clinically to inhibit bone resorption in disease states such as Paget's disease, osteoporosis, metastatic bone diseases, and malignant and nonmalignant hypercalcemia. Bisphosphonates are also used to mediate anti-cancer effects by modifying the bone surface, altering the bone microenvironment, inhibiting specific enzymatic pathways and inducing apoptosis in osteoclast and tumor cells.

#FIG. 1 is the scheme for the synthesis of vitamin B6-bisphosphonate conjugates.

#FIG. 2 is the scheme for the preparation of nucleoside-5′-triphosphate analogs.

#FIG. 3 demonstrates the stability of a bisphosphonate fluorouracil conjugate in human serum.

#The present invention relates to novel bisphosphonate conjugates that are capable of delivering therapeutic compounds such as antibacterial and/or anti-neoplastic (cytotoxic) compounds or peptide or protein compounds having growth stimulating properties to bone and soft tissues surrounding bone. The conjugates release the therapeutic components upon binding to the bone tissue and are therefore useful in the treatment and prevention of primary bone tumors, metastases to bone tissues, bone inflammation, bone infections and disorders of the growth of bone and bone marrow.

#Bisphosphonates are synthetic compounds containing two phosphonate groups bound to a central (geminal) carbon (the P—C—P backbone) that are used to prevent bone resorption in a number of metabolic and tumor-induced bone diseases including multiple myeloma. Bisphosphonate treatment is associated with an increase in patient survival, indicating that these compounds have a direct effect on the tumor cells.

#Bisphosphonates may contain two additional chains bound to the central geminal carbon. The presence of these two side chains allows numerous substitutions to the bisphosphonate backbone and therefore the development of a variety of analogs with different pharmacological properties. The activity varies greatly from compound to compound, the newest bisphosphonates being 5,000 to 10,000 times more active than etidronate, the first bisphosphonate described. The mechanism of action of bisphosphonates includes a direct effect exerted on osteoclast activity, direct and indirect effects on osteoclast recruitment mediated by cells of the osteoblastic lineage and involving the production of an inhibitor of osteoclastic recruitment and a shortening of osteoclast survival by apoptosis.