Bisphosphonate Moiety Research Articles

Crystal structures of hFPPS in complex with novel anticancer drug leads

Human farnesyl pyrophosphate synthase (hFPPS) produces farnesyl pyrophosphate, an isoprenoid required for a variety of essential cellular processes. Inhibition of hFPPS has been well established as the mechanism of action of the nitrogen-containing bisphosphonate (N-BP) drugs, currently best known for their anti-bone resorptive effects. Recent investigations indicate that hFPPS inhibition also produces potent anticancer effects both in vitro and vivo: N-BPs inhibit proliferation, motility, and viability of tumor cells, and act in synergy with other anticancer agents [1,2]. However, the physicochemical properties of the current N-BP drugs seriously compromise their full anticancer potential in non-skeletal tissues. They show poor membrane permeability and extreme affinity to bone, due mainly to their highly charged bisphosphonate moiety, which mimics the pyrophosphate of the substrates of hFPPS. Both the substrates and N-BPs bind to hFPPS via Mg ion-mediated interactions between their pyrophosphate/bisphosphonate moiety and two aspartate-rich surfaces of the enzyme's active site cavity. Recently, we took a structure-guided approach to develop bisphosphonates with higher lipophilicity for enhanced uptake into non-skeletal tissues. Surprisingly, some of the new compounds were found to bind to hFPPS even in the absence of Mg ions. Crystal structures of hFPPS in complex with a representative compound revealed that this bisphosphonate binds to the enzyme's active site in the presence of Mg ions, but also to a nearby allosteric inhibitory site in their absence. Furthermore, removal of a phosphonate group from the bisphosphonate moiety of this compound resulted in an inhibitor that binds exclusively to the allosteric site. Based on the crystal structures with these lead compounds, we generated of a novel class of non-bisphosphonate, allosteric inhibitors of hFPPS with superior physicochemical properties than those of the current N-BP drugs for broader tissue distribution.

New 3,5-bis(arylidene)-4-piperidones with bisphosphonate moiety: synthesis and antitumor activity

An approach to the synthesis of new conjugates of 3,5-bis(arylidene)-4-piperidone pharmacophore with bisphosphonate moiety separated from the nitrogen atom of piperidone ring by four methylene units has been developed. This approach is based on the reaction of tetraethyl vinylidene-1,1-bisphosphonate with the Grignard reagent containing a dioxolane-protected piperidone ring (4-piperidone ethylene ketal), which is followed by the crotonic condensation of bisphosphonate obtained with aromatic aldehydes. In vitro evaluation of antitumor activity of prepared conjugates 3a,b toward human cancer cell lines Caov3, Scov3, KB3-1, KB8-5, A549, and MCF7 has revealed that these compounds possess moderate antitumor activity and are inferior in cytotoxicity to the analogs 1a,b with one methylene unit between piperidone and bisphosphonate moieties.

Dual carbonic anhydrase/matrix metalloproteinase inhibitors incorporating bisphosphonic acid moieties targeting bone tumors

A set of bisphosphonate matrix metalloproteinase (MMP) inhibitors was investigated for inhibitory activity against several carbonic anhydrase (CA, EC 4.2.1.1) isozymes, some of which are overexpressed in hypoxic tumors. Some of the bisphosphonate revealed to be very potent inhibitors (in the low nanomolar range) of the cytosolic isoform CA II and the membrane-bound CA IX, XII and XIV isozymes, a feature useful for considering them as interesting compounds for bone resorption inhibition applications. We suggest here that it is possible to develop dual enzyme inhibitors bearing bisphosphonate moieties that may target both MMPs and CAs, two families of enzymes involved in tumor formation, growth, and metastasis.

Tetraethyl Vinylidenebisphosphonate: A Versatile Synthon for the Preparation of Bisphosphonates

Tetraethyl vinylidenebisphosphonate is a versatile synthetic intermediate that allows access to a variety of highly functionalized compounds bearing the bisphosphonic moiety. As an electron-deficient alkene, this compound is able to undergo conjugate addition with a variety of reagents including strong nucleophiles, such as organometallic reagents and enolates, as well as very mild nucleophiles, such as amines, mercaptans and alcohols. The title compound also possesses the ability to behave as a dipolarophile or dienophile in 1,3-dipolar cycloadditions or Diels–Alder reactions, giving rise to five- or six-membered rings containing the bisphosphonic unit. In summary, tetraethyl vinylidenebisphosphonate is a very useful synthon to have at hand for straightforward syntheses of bisphosphonate derivatives of diverse structures. This bisphosphonate moiety has proven to be very important to impart important pharmacological action. 1 Introduction 2 General Reactivity 3 Michael Addition Reactions 3.1 Reaction with Organometallic Reagents 3.2 Reaction with Mercaptans and Amines 3.3 Reaction with Phosphorus-Containing Nucleophiles 3.4 Epoxidation, Loss of a Phosphonate Unit and Rearrangement Reactions 3.5 Michael Reactions with Enolates 4. Cycloaddition Reactions 4.1 Diels–Alder Reactions 4.2 1,3-Dipolar Cycloadditions 4.2.1 Reaction with Diazo Compounds 4.2.2 Reaction with Nitrones 4.2.3 Reaction with Nitrile Oxides 4.2.4 Grigg Azomethine Ylide Cyclizations 4.2.5 Reaction with Azides 5 Concluding Remarks

Arylamino bisphosphonates: Potent and selective inhibitors of the tumor-associated carbonic anhydrase XII

A set of matrix metalloproteinases (MMPs) inhibitors, containing a bisphosphonate moiety (BP), has been evaluated for the inhibitory activity of carbonic anhydrases (CAs, EC 4.2.1.1). Human (h) isoforms hCA I, II, IX, XII and XIV were included in the study due to their involvement in crucial physiologic and pathologic processes. Some of these molecules selectively inhibited CA XII in the nanomolar range, showing an attractive dual mechanism (anti-MMP and anti-CA) of action as potential antitumor agents. The BP inhibitors investigated in this study are also excellent leads for obtaining even more effective compounds able to selectively target membrane-bound CA XII and having the potential to be used as tools for understanding physiologic processes regulated by this isoform.

1,3-Dipolar Cycloadditions of the Versatile Intermediate Tetraethyl Vinylidenebisphosphonate­

The use of tetraethyl vinylidenebisphosphonate as a dipolarophile in 1,3-dipolar cycloaddition reactions was investigated. In particular, the cycloaddition reactions between tetraethyl vinylidenebisphosphonate and azides and nitrile oxides, and of tetraethyl vinylidenebisphosphonate in the Grigg azomethine 1,3-dipolar cyclization were studied, affording highly functionalized five-membered rings containing the bisphosphonic unit. These straightforward methods allow the preparation of diverse and fairly complex structures bearing the bisphosphonate moiety, which belong to a group of pharmacologically important compounds.

Efficacy of newly developed platinum complexes against osteosarcoma, bone-targeting platinum, and proteasome inhibitory platinum.

10075 Background: Cisplatin is one of the most effective anti-cancer drugs available for the treatment of human solid tumors including osteosarcoma. As we had already reported, we have utilized caffeine in our chemotherapy protocol. And we achieved excellent clinical results. But effectiveness of cisplatin has been limited by side effects, and resistance. Here we developed two novel platinum compounds. 3Pt is trinuclear platinum complex bearing geminal bisphosphonate moieties, 1Pt is mononuclear platinum complex which has proteasome inhibitory activity. We performed comparative studies of our novel platinum compounds with osteosarcoma. Methods: Two novel platinum complexes were synthesized by Prof. Odani at school of pharmaceutical sciences of our university and cisplatin and caffeine were obtained from constructor. Three cell lines (MG63, 143B, and LM8) were used. Cell survival after a 72 hrs exposure to these compounds was assessed by WST-8 assay, and IC50 value was calculated for each compound. Apoptosis was assessed by DNA fragmentation and Annexin V-FITC/propidium iodine assay. Results: Each compound strongly caused concentration-dependent cytocidal effect. IC50 value of trinuclear compound is superior to cisplatin, and both complexes showed caffeine potentiation. Apoptosis induction and acetylation of histon H2AX were observed. In vivo, 1Pt showed almost same, 3Pt showed strong antitumor effect compared to cisplatin. Conclusions: Two novel platinum compounds that we developed showed strong ant-tumor effect in osteosarcoma in vitro and in vivo. As bisphosphonate has high affinity to calcium ions, 3Pt targets bone tissue and expected to reduce side effects at extraskeletal sites and to overcome the drug resistance. Proteasome inhibitory platinum compound has never been reported before, we will investigate its anti-tumor mechanism precisely.

Phosphonate‐terminated poly(vinyl acetate) synthesized by RAFT/MADIX polymerization

AbstractFour different xanthates containing either phosphonate or bisphosphonate moieties were synthesized with high degree of purity. These xanthates were used as chain transfer agents (CTA) in the RAFT/MADIX polymerization of vinyl acetate (VAc) to prepare end‐capped poly(VAc). The rate of VAc polymerization in the presence of these new CTAs was shown to be similar to that obtained with conventional xanthate, that is, (methyl ethoxycarbonothioyl) sulfanyl acetate. Good control of VAc polymerization was also obtained since the molecular weight increased linearly with monomer conversion for each phosphonate‐containing xanthate. Low‐PDI values were obtained, ascribed to efficient exchange during RAFT/MADIX polymerization. Cex value was therefore calculated to about 25, based on RAFT/MADIX of VAc in the presence of rhodixan A1/VAc adduct. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In Vivo Fluorescence Imaging of Bone-Resorbing Osteoclasts

Osteoclasts are giant polykaryons responsible for bone resorption. Because an enhancement or loss of osteoclast function leads to bone diseases such as osteoporosis and osteopetrosis, real-time imaging of osteoclast activity in vivo can be of great help for the evaluation of drugs. Herein, pH-activatable chemical probes BAp-M and BAp-E have been developed for the detection of bone-resorbing osteoclasts in vivo. Their acid dissociation constants (pK(a)) were determined as 4.5 and 6.2 by fluorometry in various pH solutions. These pK(a) values should be appropriate to perform selective imaging of bone-resorbing osteoclasts, because synthesized probes cannot fluoresce intrinsically at physiological pH and the pH in the resorption pit is lowered to about 4.5. Furthermore, BAp-M and BAp-E have a bisphosphonate moiety that enabled the probes to localize on bone tissues. The hydroxyapatite (HA) binding assay in vitro was, therefore, performed to confirm the tight binding of the probes to the bone tissues. Our probes showed intense fluorescence at low pH values but no fluorescence signal under physiological pH conditions on HA. Finally, we applied the probes to in vivo imaging of osteoclasts by using intravital two-photon microscopy. As expected, the fluorescence signals of the probes were locally observed between the osteoclasts and bone tissues, that is, in resorption pits. These results indicate that our pH-activatable probes will prove to be a powerful tool for the selective detection of bone-resorbing osteoclasts in vivo, because this is the first instance where in vivo imaging has been conducted in a low-pH region created by bone-resorbing osteoclasts.

Platinum(ii) compounds bearing bone-targeting group: synthesis, crystal structure and antitumor activity

Platinum(II) complexes bearing geminal bisphosphonate moieties have excellent solubility in both organic and aqueous solutions and show considerable cytotoxicity against human osteosarcoma (MG-63) and ovarian cancer (COC1) cell lines with different apoptotic pathways from that of cisplatin.

Synthesis of calcium phosphate-binding liposome for drug delivery

Metastatic bone disease is often associated with bone pain, pathologic fractures, and nerve compression syndromes. Effective therapies to inhibit the progression of bone metastases would have important clinical benefits. Therefore, we developed a novel calcium phosphate-binding liposome for a bone-targeting drug delivery system. We synthesized a novel amphipathic molecule bearing a bisphosphonate (BP) head group to recognize and bind to hydroxyapatite (HA). We demonstrated that the liposomes having BP moieties show high affinity for HA. Doxorubicin-loaded liposomes adsorbed on the surface of HA significantly reduce the number of viable human osteosarcoma MG63 cells. This shows that the liposomes can be excellent carriers for anticancer drugs because they specifically target bone tissue. This calcium phosphate-binding liposome system could be used with many drugs for bone-related diseases such as osteoporosis, rheumatoid arthritis, and multiple myeloma.

Inhibition of Geranylgeranyl Diphosphate Synthase by Bisphosphonates: A Crystallographic and Computational Investigation

We report the X-ray structures of several bisphosphonate inhibitors of geranylgeranyl diphosphate synthase, a target for anticancer drugs. Bisphosphonates containing unbranched side chains bind to either the farnesyl diphosphate (FPP) substrate site, the geranylgeranyl diphosphate (GGPP) product site, and in one case, both sites, with the bisphosphonate moiety interacting with 3 Mg (2+) that occupy the same position as found in FPP synthase. However, each of three "V-shaped" bisphosphonates bind to both the FPP and GGPP sites. Using the Glide program, we reproduced the binding modes of 10 bisphosphonates with an rms error of 1.3 A. Activities of the bisphosphonates in GGPPS inhibition were predicted with an overall error of 2x by using a comparative molecular similarity analysis based on a docked-structure alignment. These results show that some GGPPS inhibitors can occupy both substrate and product site and that binding modes as well as activity can be accurately predicted, facilitating the further development of GGPPS inhibitors as anticancer agents.

A facile synthesis of aminomethylene bisphosphonates through rhodium carbenoid mediated N–H insertion reaction. Application to the preparation of powerful uranyl ligands

A straightforward procedure ensuring the anchoring of bisphosphonate moiety onto aromatic amines is described. The procedure yields aminoaryl 1,1-bisphosphonates known to display multiple biological activities. The described methodology has also been applied to the synthesis of ligands whose uranyl-binding properties have been studied.

Reaction of Zoledronate with β-Tricalcium Phosphate for the Design of Potential Drug Device Combined Systems

The reaction of aqueous Zoledronate solutions with β-tricalcium phosphate resulted in the precipitation of a crystalline Zoledronate complex on the surface of the calcium phosphate. This complex (CaNa[(HO)(C4H5N2)C(PO3)(PO3H)]·xH2O) was found to be metastable, leading to a pure calcium complex [Ca3[(HO)(C4H5N2)C(PO3)(PO3H)]2·xH2O] upon washing with water. This latter compound was found to release the bisphosphonate in phosphate buffers, in direct proportion to the phosphate concentration, while using a specific in vitro bone resorption model, an inhibition of osteoclastic activity was observed with this material. This suggested that when this composite is implanted in bone tissues, the drug will be released in greater concentration the more the bone is being resorbed, resulting in a decrease of osteoclast activity and making this drug device combination suitable for practical application as a bisphosphonate local delivery system. In addition, the chemical environment of the bisphosphonate moiety in the two reported bisphosphonate/calcium phosphate composites was probed using 31P and 23Na magic-angle-spinning NMR and two-dimensional 31P homonuclear and 31P−1H heteronuclear correlation experiments, thus giving clear evidence that modern high-resolution solid-state NMR is a powerful tool for the characterization of calcium phosphate-based biomaterials.

A Facile Anchoring of the Bisphosphonate Moiety into Alcohols and Phenols Through Copper Carbenoid Mediated O—H Insertion Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Potentiometric and spectrophotometric equilibrium study on Fe(III) and new catechol-bisphosphonate conjugates

The coordination properties of mixed catechol-bisphosphonates towards Fe(III) are presented. From the potentiometric and spectroscopic results it was possible to state that iron coordination takes place only on the bisphosphonate moiety at acidic pH, and involves both catechol and bisphosphonate groups on two different iron(III) ions at higher pH values. Steric constracts keep both groups from chelating the same metal ion. Quantum mechanical calculations confirm this statement and allow to determine the minimum length of the linker for a stable conformation of complexes in which the same iron(III) ion is coordinated by both catechol and bisphosphonate.

A Facile Anchoring of the Bisphosphonate Moiety into Alcohols and Phenols through Copper Carbenoid Mediated O-H Insertion Reaction

A straightforward procedure ensuring the anchoring of bisphosphonate moiety into alcohols or phenols is described. The method uses a bisphosphonate-metal-carbenoid O-H insertion -reaction for which copper(II) triflate was found to be an efficient catalyst.

Synthesis of γ‐Butyrolactones Containing α,α‐Difluoromethylenyl Bisphosphonate Initiated by Na2S2O4.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis of novel phosphonated tripodal ligands for actinides chelation therapy

Efficient synthetic routes for preparation of a new family of aldehyde–bisphosphonate conjugates were presented. These compounds appeared as promising intermediates for incorporation of bisphosphonate moiety in various substrates under mild conditions. We report here a first application to the synthesis of a series of three phosphonated tripods designed for actinides chelation therapy.

Synthesis of γ-butyrolactones containing α,α-difluoromethylenyl bisphosphonate initiated by Na 2S 2O 4

Diethyl iododifluoromethylphosphonate ( 1) reacted with 4-pentenoic acids in the presence of Na 2S 2O 4 in aqueous acetonitrile solution at ambient temperature to afford various γ-butyrolactones containing α,α-difluoromethylenyl bisphosphonate moiety in moderate to good yields.