A General Strategy for Targeting Drugs to Bone

Article abstract of DOI:10.1002/anie.201507064

Targeting drugs to their desired site of action can increase their safety and efficacy. Bisphosphonates are prototypical examples of drugs targeted to bone. However, bisphosphonate bone affinity is often considered too strong and cannot be significantly modulated without losing activity on the enzymatic target, farnesyl pyrophosphate synthase (FPPS). Furthermore, bisphosphonate bone affinity comes at the expense of very low and variable oral bioavailability. FPPS inhibitors were developed with a monophosphonate as a bone-affinity tag that confers moderate affinity to bone, which can furthermore be tuned to the desired level, and the relationship between structure and bone affinity was evaluated by using an NMR-based bone-binding assay. The concept of targeting drugs to bone with moderate affinity, while retaining oral bioavailability, has broad application to a variety of other bone-targeted drugs.

Full text of DOI:10.1002/anie.201507064

Angewandte
Chemie
International Edition: DOI: 10.1002/anie.201507064
German Edition: DOI: 10.1002/ange.201507064
Drug Design
Hot Paper
A General Strategy for Targeting Drugs to Bone
Wolfgang Jahnke,* Guido Bold, Andreas L. Marzinzik, Silvio Ofner, Xavier PellØ,
Simona Cotesta, Emmanuelle Bourgier, Sylvie Lehmann, Chrystelle Henry, RenØ Hemmig,
FrØdØric Stauffer, J. Constanze D. Hartwieg, Jonathan R. Green, and Jean-Michel Rondeau
Abstract: Targeting drugs to their desired site of action can
increase their safety and efficacy. Bisphosphonates are proto-
typical examples of drugs targeted to bone. However,
bisphosphonate bone affinity is often considered too strong
and cannot be significantly modulated without losing activity
on the enzymatic target, farnesyl pyrophosphate synthase
(FPPS). Furthermore, bisphosphonate bone affinity comes at
the expense of very low and variable oral bioavailability. FPPS
inhibitors were developed with a monophosphonate as a bone-
affinity tag that confers moderate affinity to bone, which can
furthermore be tuned to the desired level, and the relationship
between structure and bone affinity was evaluated by using an
NMR-based bone-binding assay. The concept of targeting
drugs to bone with moderate affinity, while retaining oral
bioavailability, has broad application to a variety of other
bone-targeted drugs.
Nevertheless, FPPS inhibitors with no or variable affinity to
bone could be therapeutically interesting: For the treatment
of non-bone diseases, such as breast cancer,[5a,b] multiple
myeloma,[5c] progeria[5d] and parasitic diseases,[5e] more lip-
ophilic FPPS inhibitors devoid of any bone affinity would be
useful. On the other hand, for the discovery of improved
drugs to treat bone diseases, FPPS inhibitors with weaker and
tuneable bone affinity could provide an interesting therapeu-
tic option. Such FPPS inhibitors might have several advan-
tages over bisphosphonates: they could have higher oral
bioavailability, they could distribute more evenly into the
skeleton, and they could reduce adverse effects such as
osteonecrosis of the jaw.[6]
For bisphosphonates, the pharmacophores for FPPS
inhibition and bone binding are identical, so bisphosphonates
with significantly reduced bone affinity have not been
identified in spite of tremendous efforts.[7,8] Our recently
discovered allosteric FPPS inhibitors, which bind to a different
site on the enzyme and are devoid of any bone affinity,[9] are
attractive tools for the treatment of FPPS-related non-bone
diseases. For the treatment of bone diseases with compounds
with improved properties, we report herein the attachment of
a monophosphonate functionality as a bone-affinity tag to
allosteric inhibitors of FPPS. Taking advantage of our NMR-
based bone binding assay,[10] we show that, in sharp contrast to
N-BPs, the bone affinity of these compounds can be tuned to
the desired degree, independently from their inhibitory
potency towards FPPS. Targeting a drug to the diseased
tissue or organ is an attractive concept for improving efficacy
and reducing adverse effects. The work described herein
provides a practical approach to conferring a suitable degree
of bone affinity on a drug candidate, and it may therefore
become a general strategy to improve the safety and efficacy
of drugs acting on bone.[10,11]
Our research was initially sparked by the serendipitous
discovery that AMP397 (4, Becampanel; Scheme 1), a drug
previously in phase II clinical trials for the treatment of
epilepsy, displayed moderate affinity to bone mineral, as
shown by quantitative whole-body autoradioluminography
and confirmed by our NMR-based hydroxyapatite (HAP)
binding assay (see Figure 1 and Figure S1 in the Supporting
Information). AMP397 is a monophosphonate but it has
a significant oral bioavailability of 22% in mice and
approximately 50% in humans.[12] Furthermore, AMP397
has shown preclinical and clinical efficacy as an anti-epileptic
drug, thus indicating that it can cross biological membranes
and even the blood–brain barrier. In addition, some other
monophosphonates, such as the antibiotic fosfomycin, are
clinically used drugs with oral bioavailability. Taken together,
N
itrogen-containing bisphosphonates (N-BPs) such as
zoledronate (1, ZOL) and pamidronate (3; Scheme 1) are
widely used drugs for treating bone loss associated with
diseases such as osteoporosis, Pagetꢀs disease, and bone
metastases.[1] Their remarkable safety and efficacy stem in
part from their high affinity to bone mineral, which enables
drug accumulation at the desired site of action, where they
specifically inhibit osteoclasts by blocking farnesyl pyrophos-
phate synthase (FPPS).[1] FPPS catalyzes the formation of
geranyl pyrophosphate (GPP) and farnesyl pyrophosphate
(FPP) from isopentenyl pyrophosphate (IPP) and dimethyl-
allyl pyrophosphate (DMAPP) in the mevalonate pathway
(see Scheme S1 in the Supporting Information). Recent
crystallographic analyses of human FPPS have shown that
N-BPs are in fact DMAPP mimetics, with the bisphosphonate
moiety very effectively replacing the pyrophosphate group of
the substrate as an anchor to the three active-site magnesium
ions.[2,3]
Bisphosphonate FPPS inhibitors are generally very safe
and effective drugs that display extremely rapid and strong
binding to bone mineral, with association rates in the order of
minutes and dissociation rates in the order of years.[4]
[*] Dr. W. Jahnke, Dr. G. Bold, Dr. A. L. Marzinzik, Dr. S. Ofner, X. PellØ,
Dr. S. Cotesta, E. Bourgier, S. Lehmann, C. Henry, R. Hemmig,
Dr. F. Stauffer, Dr. J. C. D. Hartwieg, Dr. J. R. Green,
Dr. J.-M. Rondeau
Novartis Institutes for BioMedical Research
Center for Proteomic Chemistry and Oncology Research
4002 Basel (Switzerland)
E-mail: wolfgang.jahnke@novartis.com
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201507064.
Angew. Chem. Int. Ed. 2015, 54, 14575 –14579
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
14575

.
Angewandte
Communications
instead of the phosphonate
group, did not show any evi-
dence of HAP binding, thus
clearly demonstrating that the
monophosphonate functional-
ity is responsible for HAP
affinity (Figure 1B). In the
presence of ZOL and limiting
amounts of HAP (competi-
tion format), AMP397 no
longer showed any HAP bind-
ing (Figure 1C), thus indicat-
ing at least 10-fold weaker
binding of AMP397 compared
to ZOL. However, com-
pound 2,
a ZOL analogue
with reduced bone affinity,
only showed 8-fold stronger
binding to HAP as compared
to AMP397 (Figure 1D).
Since the binding affinity of 2
to HAP is 2.3-fold weaker
than that of ZOL,[10] we con-
cluded that the HAP binding
affinity of AMP397 is about
18-fold weaker than that of
ZOL or other closely related
1-hydroxy bisphosphonates.
Notably, and in spite of this
decrease in bone affinity,
AMP397 accumulation in
bone can still be detected by
quantitative whole-body auto-
radioluminography 72 h after
AMP397 administration (Fig-
ure S1 in the Supporting
Information).
Scheme 1. Structures of the compounds investigated in this study.
In
a second step, we
devised a strategy for grafting
a monophosphonate functionality onto an allosteric inhibitor
of FPPS, such as the benzoindole derivative 6. On the basis of
the available X-ray structures,[9] we identified three options:
1) direct replacement of a carboxylic acid substituent by
a phosphonate group, 2) the same but with a spacer, or
3) attachment of a phosphonate group at a suitable solvent-
exposed position. Only the first two options were pursued in
this project, because the latter would entail an unnecessary
increase in molecular weight as well as in the total negative
charge of the molecule. Figure 2 illustrates these three options
in the context of the crystal structure of the FPPS complex
with 6.
We then synthesized 7, the readily accessible 2-phospho-
nomethylcarbamoyl derivative of 6, and assessed its FPPS
inhibitory activity and HAP binding affinity. Gratifyingly, 7
was only slightly weaker (IC50 = 0.4 mm) as an FPPS inhibitor
than its parent compound 6 (IC50 = 0.2 mm), and it showed
significant HAP binding (Figure S2C). This promising result
prompted us to investigate the generality of this strategy by
testing it with two recently identified, distinct series of
these observations suggested that bone affinity can be
reconciled with oral bioavailability and significant plasma
membrane permeability, and moreover, that a monophosph-
onate functionality could be a suitable bone-affinity tag.
In a first step, we investigated the bone-binding propen-
sity of AMP397 (4) and its carboxylic acid analogue 5, in
comparison to the reference bisphosphonate ZOL (1) and its
dehydroxy analogue 2. To this end, our NMR-based assay
provided a robust and rapid means to detect and quantify
affinity to bone powder or hydroxyapatite (HAP), the main
mineral component of bone.[10] In this study, we used HAP,
since very similar results were obtained with bone powder and
HAP, but the latter showed higher homogeneity and repro-
ducibility.[10] The NMR-based bone binding assay can be run
as a direct binding assay or in a competition format, from
which relative affinities to bone can be determined, as
described.[10,13] Figure 1A shows the direct-binding format
for AMP397, which demonstrates its binding to HAP (see the
Supporting Information for experimental details). By con-
trast, compound 5, an AMP397 analogue with a carboxylate
14576 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 14575 –14579

Angewandte
Chemie
theless showed submicromolar inhibition
of FPPS. In the quinoline series, how-
ever, the vinyl phosphonate 14 (IC50 =
0.04 mm) was significantly more potent
than the parent carboxylate analogue 13
(IC50 = 1 mm). Thus, for each of the three
lead series, we could identify phospho-
nate analogues exhibiting submicromo-
lar inhibitory activity (Scheme 1). X-ray
analysis of the FPPS complexes with 7,
13, and 15, a close analogue of 14,
confirmed that the phosphonate ana-
logues adopt a very similar binding
mode to that of their parent carboxylate,
and explained the observed effects on the
inhibitory potency. In the benzoindole
series, the phosphonate moiety is highly
exposed to bulk solvent and is further
(4.7–5.1 Š) from the side-chain amino
group of Lys57 than its carboxylate
counterpart (4.0–4.3 Š), thus explaining
the marginal reduction in inhibitory
potency (Figure 2C). In the quinoline
series, the vinyl phosphonate group
points towards the binding site of the b-
Figure 1. Quantification and characterization of the bone binding affinity of AMP397 (4) by the
NMR-based HAP binding assay.[10] A) The direct binding assay with increasing amounts of HAP
(red and green spectra) demonstrates AMP397 binding to HAP. B) Replacement of the
AMP397 monophosphonate group with a carboxylate functionality abolishes HAP binding.
C) The competition assay shows no detectable AMP397 binding to HAP in the presence of
ZOL. Hence, AMP397 binding to HAP is at least 10-fold weaker than that of ZOL. D) The
competition assay with 2, the dehydroxy analogue of ZOL with a 2.3-fold reduced affinity to
HAP,[10] shows 9% AMP397 bound to HAP and 69% 2 bound to HAP. The affinity to HAP of
AMP397 is therefore about 8-fold weaker than that of dehydroxy-ZOL 2, or 18-fold weaker than
that of ZOL 1.
phosphate of IPP and is involved in multiple H-bonded
contacts with the BC loop of the enzyme, as well as in strong,
buried electrostatic interactions with Arg60 and Arg113,
which contributes to significantly enhanced potency (Fig-
ure 2D and Figure S4). As shown by X-ray analyses,[9b] the
binding modes of quinoline and salicylic acid derivatives
largely overlap, with the carboxylic acid groups pointing in
the same direction. Therefore, and in contrast to the
benzoindole series, the conversion of these quinoline and
salicylic acid derivatives into phosphonate analogues has
potentially more impact on the inhibitory potency, as
examplified here with 9/10 and 13/14. Taken together, the
allosteric pocket of FPPS can accommodate monophospho-
nate ligands with high affinity, as also recently shown by
Tsantrizos and co-workers.[15]
While an in-depth investigation of the structure–activity
relationships (SAR) of phosphonate derivatives for allosteric
inhibition of FPPS would be needed for their further chemical
elaboration and optimization, a solid understanding of the
SAR for bone binding is equally important if this function-
ality is intended as a bone-targeting tag, so we shall focus on
the latter. Figure 3 presents spectra for NMR-detected HAP
binding for a series of salicylic acid derivatives (9–12; see
Scheme 1 for structures). Figure 3A shows that the parent
carboxylate compound 9 lacks bone affinity, which is in line
with our initial observation with the AMP397 carboxylic acid
analogue 5. If a phosphonate functionality is attached directly
to the aromatic ring system, as in compound 10 (Figure 3B),
bone binding is still not detected. By contrast, when a single
methylene spacer is introduced, as in 11 (Figure 3C), bone
binding is clearly observed. Interestingly, bone affinity
becomes even stronger when the linker is further elongated
and thus made more flexible (12, Figure 3D). A qualitatively
similar SAR for bone binding was observed in the benzoin-
Figure 2. Crystal structure of the binary complex of FPPS with the
allosteric inhibitor 6.[9] A) Overall view of one FPPS subunit showing
the location of the allosteric site (green stick model) in relation to the
DMAPP/ZOL (red) and IPP (yellow) binding sites. Note the different
conformational states adopted by the enzyme in the binary complex
with 6 (open state, blue ribbon) and in the ternary complex with ZOL
and IPP (close state, gray ribbon) B) Close-up view of the allosteric
site in surface representation, showing the solvent accessibility of the
carboxylic acid function in position 2 of the benzoindole tricyclic ring
system. C) Close-up view of the complex with 7 (yellow), a phosphonate
derivative of 6, and structural overlay with 6 (green stick model).
D) Close-up view (same orientation as (C)) of the complex with 15
(yellow), a phosphonate derivative of 13, and structural overlay with 13
(green stick model).
allosteric FPPS inhibitors.[9b,14] In the salicylic acid series, 10
(the phosphonate analogue of 9) was less potent (IC50 =
0.52 mm) than its parent compound (0.021 mm) but never-
Angew. Chem. Int. Ed. 2015, 54, 14575 –14579
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 14577

.
Angewandte
Communications
Figure 3. Affinity to hydroxyapatite (HAP) measured for several mem-
bers of the salicylic acid series by using the NMR-based direct HAP
binding assay.[10] The original allosteric FPPS inhibitor 9 showed no
binding affinity to HAP (A), and nor did 10, which has a phosphonate
group directly replacing the carboxylic acid (B). However, as the length
of the spacer between the aromatic system and the monophosphonate
was increased and the monophosphonate-bearing substituent became
more flexible, bone binding was enhanced (C,D).
Figure 4. Relative affinities to HAP. A,B) Determination by NMR-based
HAP binding assay of the relative affinities of monophosphonates 11
(A, green) and 12 (B, orange) in a competition format with AMP397 4
(blue). Resonances of 4, 11, and 12 are marked by arrows in the
respective color. The asterisks indicate an impurity. C) A graph depict-
ing the relative affinities of the investigated compounds on a logarith-
mic scale.
dole series with 6, 7, and 8 (Figure S2). These data show that
the presence of a phosphonate moiety alone is not sufficient
to confer bone affinity to organic compounds. Furthermore,
they show that the degree of bone affinity can be tuned by
changing the length of the spacer, thus indicating that bone or
HAP binding is limited by steric hindrance. While a single-
atom spacer may provide sufficient flexibility to allow bind-
ing, affinity can be enhanced by using longer, two- to three-
atom spacers. Interestingly, the vinyl phosphonic acid deriv-
ative 14 did not bind to HAP, thus further underscoring the
requirement for flexibility when strong bone binding is
desired. It may thus be possible to adjust bone affinity to
the desired degree by varying both the length and chemical
nature of the linker to the phosphonic acid group.
Preclinical in vivo data are available for AMP397 (4),
which show that this compound accumulates in the skeleton
as seen by quantitative whole-body autoradioluminography
72 h after AMP397 administration (Figure S1). It is thus
interesting to compare the relative HAP affinities of AMP397
and our best-binding allosteric FPPS inhibitors. To this end,
11 and 12, the members of the salicylic acid series with affinity
to HAP, were subjected to the HAP binding assay in
competition with AMP397 (4). As seen in Figure 4A, 11
and AMP397 have almost equal affinity to HAP (52% bound
11 versus 56% bound 4). By contrast, 12 (which showed
stronger bone binding than 11 in the direct-binding format,
Figure 3D) clearly binds to HAP with higher affinity than
AMP397 (Figure 4B: 91% bound 12 versus 51% bound 4).
This result is important because it correlates in vitro bone
binding with in vivo bone accumulation data and allows us to
predict the in vivo bone accumulation of monophosphonate
FPPS inhibitors such as 11 and 12.
herein a rational approach for conferring variable degrees of
bone affinity on drug candidates. Our approach only requires
the attachment of a phosphonate functionality to the drug
molecule via a 1–3 atom spacer. This substituent can be
attached to any suitable position that will not hamper binding
to the target enzyme or receptor, as exemplified by the
benzoindole series of FPPS inhibitors. Alternatively, as
demonstrated with the quinoline series, it might be possible
in favorable cases to confer some degree of bone affinity
while simultaneously enhancing target binding. To this end,
the recently developed NMR-based HAP binding assay is key
for fast and robust assessment of bone affinity during lead
optimization. While a more comprehensive analysis of the
SAR for bone binding remains to be performed, our current
data indicate that it is not very stringent, provided that the
spacer is of sufficient length and flexibility. However, not
every phosphonate moiety confers bone binding, and in fact,
bone affinity has not been reported for phosphate- or
phosphonate-containing prodrugs or metabolites. Still, medi-
cinal chemists should have ample opportunities for tuning the
desired degree of bone binding while maintaining potency
and optimizing the overall physicochemical and pharmaco-
logical properties of the drug candidate.
The examples of the clinical compounds AMP397 and
fosfomycin prove that monophosphonates can be orally
available while exhibiting significant affinity to bone. The
proposed strategy of attaching a phosphonic acid function-
ality as a bone-affinity tag can be useful for enhancing the
safety and efficacy of antiresorptive or bone-anabolic drugs,
such as inhibitors of c-Src,[16,17] cathepsin K,[18] colony stim-
ulating factor-1 receptor (CSF-1R), selective androgen recep-
As a summary of our investigations, the relative HAP
affinities of the compounds discussed here are depicted in
Figure 4C, which shows that monophosphonates such as 11,
12, or AMP397 can have an intermediate degree of HAP
affinity compared to N-BPs such as ZOL. We have outlined
14578 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 14575 –14579

Angewandte
Chemie
[7] J. E. Dunford, A. A. Kwaasi, M. J. Rogers, B. L. Barnett, F. H.
tor modulators (SARMs), selective estrogen receptor mod-
ulators (SERMs), or prostaglandin E2 conjugates.[19] The
clinical development of such compounds is challenging
because the respective targets occur not only in bone-
resorbing or bone-forming cells such as osteoclasts or
osteoblasts, but throughout the body, thus leading to unde-
sired adverse effects. Targeting these modulators to bone thus
has the potential to enhance tolerability and efficacy without
compromising permeability or oral bioavailability. We hope
that this approach will pave the way towards safer and more
effective drugs for the treatment of bone diseases.
Ebetino, R. G. G. Russell, U. Oppermann, K. L. Kavanagh, J.
Med. Chem. 2008, 51, 2187 – 2195.
[8] M. S. Marma, Z. Xia, C. Stewart, F. Coxon, J. E. Dunford, R.
Baron, B. A. Kashemirov, F. H. Ebetino, J. T. Triffitt, R. G. G.
Russell, C. E. McKenna, J. Med. Chem. 2007, 50, 5967 – 5975.
[9] a) W. Jahnke, J. M. Rondeau, S. Cotesta, A. Marzinzik, X. Pelle,
M. Geiser, A. Strauss, M. Gotte, F. Bitsch, R. Hemmig, C. Henry,
S. Lehmann, J. F. Glickman, T. P. Roddy, S. J. Stout, J. R. Green,
Nat. Chem. Biol. 2010, 6, 660 – 666; b) A. L. Marzinzik, R.
Amstutz, G. Bold, E. Bourgier, S. Cotesta, J. F. Glickman, M.
Gçtte, C. Henry, S. Lehmann, J. C. D. Hartwieg, S. Ofner, X.
PellØ, T. P. Roddy, J.-M. Rondeau, F. Stauffer, S. J. Stout, A.
Widmer, J. Zimmermann, T. Zoller, W. Jahnke, ChemMedChem
2015, DOI: 10.1002/cmdc.201500338.
[10] W. Jahnke, C. Henry, ChemMedChem 2010, 5, 770 – 776.
[11] S. Zhang, G. Gangal, H. Uludag, Chem. Soc. Rev. 2007, 36, 507 –
531.
Acknowledgements
We thank Dr. Yves Auberson, Novartis, for helpful discus-
sions about AMP397, and A. Schweizer for the quantitative
whole-body autoradioluminography experiment with
AMP397. We also thank Thomas Roddy and Steven J. Stout
for biochemical assay data, Martin Geiser, AndrØ Strauss, and
Sebastien Rieffel for protein cloning and expression, and
Michael Wright, Martin Gunzenhauser, Marjorie Bourrel,
Mathilde Schindler, Werner Beck, Andrey Quantinet, Ursula
Dürler, Mario Madçrin, and Aurelio Maissen for synthetic
work. The coordinates of the crystal structures presented here
have been deposited at the RCSB protein data bank (www.
rcsb.org; PDB IDs: 5DGM (FPPS + 7), 5DGN (FPPS + 13),
and 5DGS (FPPS + 15))
[12] a) Y. P. Auberson, P. Acklin, S. Bischoff, R. Moretti, S. Ofner, M.
Schmutz, S. J. Veenstra, Bioorg. Med. Chem. Lett. 1999, 9, 249 –
254; b) Y. P. Auberson, Book of Abstracts 2000, 219th ACS
National Meeting, San Francisco, CA, March 26 – 30, 2000; c) H.
Mattes, D. Carcache, H. O. Kalkman, M. Koller, J. Med. Chem.
2010, 53, 5367 – 5382; d) Y. P. Auberson 21st international
Symposium on Medicinal Chemistry 2010, Brussels, Belgium,
Sept 9, 2010.
[13] X. Zhang, A. Sanger, R. Hemmig, W. Jahnke, Angew. Chem. Int.
Ed. 2009, 48, 6691 – 6694; Angew. Chem. 2009, 121, 6819 – 6822.
[14] a) R. Amstutz, G. Bold, S. Cotesta, W. Jahnke, A. Marzinzik,
J. C. D. Hartwieg, S. Ofner, F. Stauffer, J. Zimmermann,
WO2009106586, 2009; b) S. Cotesta, J. F. Glickman, W. Jahnke,
A. Marzinzik, S. Ofner, J.-M. Rondeau, T. Zoller,
WO2010043584, 2010.
[15] J. W. De Schutter, J. Park, C. Y. Leung, P. Gormley, Y.-S. Lin, Z.
Hu, A. M. Berghuis, J. Poirier, Y. S. Tsantrizos, J. Med. Chem.
2014, 57, 5764 – 5776.
Keywords: AMP397 (becampanel) · bone-affinity tag ·
drug delivery · NMR spectroscopy · tissue targeting
[16] W. Shakespeare, M. Yang, R. Bohacek, F. Cerasoli, K. Stebbins,
R. Sundaramoorthi, M. Azimioara, C. Vu, S. Pradeepan, C.
Metcalf III, C. Haraldson, T. Merry, D. Dalgarno, S. Narula, M.
Hatada, X. Lu, M. R. van Schravendijk, S. Adams, S. Violette, J.
Smith, W. Guan, C. Bartlett, J. Herson, J. Iuliucci, M. Weigele, T.
Sawyer, Proc. Natl. Acad. Sci. USA 2000, 97, 9373 – 9378.
[17] Y. Wang, C. A. Metcalf III, W. C. Shakespeare, R. Sundara-
moorthi, T. P. Keenan, R. S. Bohacek, M. R. van Schravendijk,
S. M. Violette, S. S. Narula, D. C. Dalgarno, C. Haraldson, J.
Keats, S. Liou, U. Mani, S. Pradeepan, M. Ram, S. Adams, M.
Weigele, T. K. Sawyer, Bioorg. Med. Chem. Lett. 2003, 13, 3067 –
3070.
[18] J. A. Eisman, H. G. Bone, D. J. Hosking, M. R. McClung, I. R.
Reid, R. Rizzoli, H. Resch, N. Verbruggen, C. M. Hustad, C.
DaSilva, R. Petrovic, A. C. Santora, B. A. Ince, A. Lombardi, J.
Bone Miner. Res. 2011, 26, 242.
[19] L. Gil, Y. Han, E. E. Opas, G. A. Rodan, R. Ruel, J. G. Seedor,
P. C. Tyler, R. N. Young, Bioorg. Med. Chem. 1999, 7, 901 – 919.
How to cite: Angew. Chem. Int. Ed. 2015, 54, 14575–14579
Angew. Chem. 2015, 127, 14783–14787
[1] a) R. G. G. Russell, Bone 2011, 49, 2 – 19; b) M. J. Rogers, J. C.
Crockett, F. P. Coxon, J. Monkkonen, Bone 2011, 49, 34 – 41;
c) J. E. Dunford, Curr. Pharm. Des. 2010, 16, 2961 – 2969.
[2] J.-M. Rondeau, F. Bitsch, E. Bourgier, M. Geiser, R. Hemmig,
M. Kroemer, S. Lehmann, P. Ramage, S. Rieffel, A. Strauss, J. R.
Green, W. Jahnke, ChemMedChem 2006, 1, 267 – 273.
[3] K. L. Kavanagh, K. Guo, J. E. Dunford, X. Wu, S. Knapp, F. H.
Ebetino, M. J. Rogers, R. G. Russell, U. Oppermann, Proc. Natl.
Acad. Sci. USA 2006, 103, 7829 – 7834.
[4] S. Cremers, S. Papapoulos, Bone 2011, 49, 42 – 49.
[5] a) P. ClØzardin, I. Benzaïd, P. I. Croucher, Bone 2011, 49, 66 – 70;
b) M. Gnant, P. ClØzardin, Cancer Treat. Rev. 2012, 38, 407 – 415;
c) N. Giuliani, B. Dalla Palma, M. Bolzoni, Clin. Rev. Bone Min.
Metab. 2013, 11, 113 – 121; d) I. Varela, S. Pereira, A. P. Ugalde,
C. L. Navarro, M. F. Suµrez, P. Cau, J. CadiÇanos, F. G. Osorio, N.
Foray, J. Cobo, F. de Carlos, N. LØvy, J. M. P. Freije, C. López-
Otín, Nat. Med. 2008, 14, 767 – 772; e) R. Docampo, S. N.
Moreno, Curr. Drug Targets Infect. Disord. 2001, 1, 51 – 61.
[6] S. Paulo, A. M. Abrantes, M. Laranjo, L. Carvalho, A. Serra,
M. F. Botelho, M. M. Ferreira, Oncol. Rev. 2014, 8, 254 – 259.
Received: July 30, 2015
Published online: October 12, 2015
Angew. Chem. Int. Ed. 2015, 54, 14575 –14579
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 14579