A selective estrogen receptor modulator designed for the treatment of uterine leiomyoma with unique tissue specificity for uterus and ovaries in rats

Article abstract of DOI:10.1021/jm050723z

The design of a novel selective estrogen receptor modulator (SERM) for the potential treatment of uterine leiomyoma is described. 16 (LY2066948-HCl) binds with high affinity to estrogen receptors α and β (ERα and ERβ, respectively) and is a potent uterine

Full text of DOI:10.1021/jm050723z

6772
J. Med. Chem. 2005, 48, 6772-6775
Chart 1
A Selective Estrogen Receptor Modulator
Designed for the Treatment of Uterine
Leiomyoma with Unique Tissue
Specificity for Uterus and Ovaries in
Rats
Conrad W. Hummel,† Andrew G. Geiser,‡
Henry U. Bryant,‡ Ilene R. Cohen,‡ Robert D. Dally,‡
Kin Chiu Fong,† Scott A. Frank,‡ Ronald Hinklin,†
Scott A. Jones,‡ George Lewis,† Denis J. McCann,‡
Daniel G. Rudmann,‡ Timothy A. Shepherd,‡
Hongqi Tian,† Owen B. Wallace,‡ Minmin Wang,‡
Yong Wang,‡ and Jeffrey A. Dodge*,‡
Lilly Research Laboratories, Eli Lilly and Company,
Lilly Corporate Center, Indianapolis, Indiana 46285, and
Array Biopharma, 2600 Trade Center Avenue,
Longmont, Colorado 80503
ifen has on the hypothalamic-pituitary-ovarian (HPO)
axis; i.e., this SERM acts as an estrogen antagonist at
the hypothalamus, resulting in increased gonadotropins
levels (luteinizing hormone, follicle stimulating hor-
mone) and, ultimately, hyperstimulation of the ovaries.
In fact, inhibition of the HPO axis by SERMs such as
clomiphene has been clinically exploited to induce
ovulation in women.7 Raloxifene, a more complete
uterine antagonist than tamoxifen or clomiphene, sig-
nificantly reduces leiomyoma size in postmenopausal
women8 yet is less efficacious at reducing tumor volume
in premenopausal women.9 This result has been at-
tributed to the poor pharmacokinetic properties of this
compound in which extensive conjugative metabolism
of the phenol(s) limits the circulating levels of the parent
drug. In addition, clinical outcomes in premenopausal
women treated with raloxifene have suggested that this
compound, like tamoxifen and clomiphene, can affect
the ovaries via the HPO axis.10 These data, taken
collectively, indicate that current SERMs lack the
efficacy, pharmacokinetic, and ovarian safety properties
needed to treat leiomyoma in ovulatory women. There-
fore, we sought to improve the potency and efficacy of
this class of molecules while simultaneously addressing
the issue of ovarian safety. We hypothesized that
limiting access of a SERM to the estrogen receptors in
the hypothalamus would diminish their inhibitory ef-
fects on the HPO axis, thereby minimizing unwanted
stimulation of the ovaries. Here, we describe the dis-
covery of such a SERM, 16 (LY2066948-HCl, Chart 1),
a new chemical entity currently under clinical evalua-
tion for the potential treatment of uterine leiomyoma
in premenopausal women.
Initially we investigated the naphthalene SERM 2
(LY326315)11 because this compound has been shown
to reduce the incidence of spontaneous leiomyomas in
the Eker rat model.12 Unfortunately, when 2 was given
to normal female rats for 35 days at doses of 1 mpk and
greater, histologic effects on the ovaries (decreased
corpora lutea and follicular prominence) were seen, as
well as a greater than 3-fold increase in serum estradiol
levels, a sensitive biomarker for ovarian stimulation.
Moreover, the uterine antagonism of 2 in rats is similar
to that of 1 (0.36 vs 0.55 mg/kg, respectively; see Table
1), a result that we felt would be less than optimal for
the treatment of uterine tumors based on the clinical
outcomes observed with 1 in premenopausal women.
Received July 27, 2005
Abstract: The design of a novel selective estrogen receptor
modulator (SERM) for the potential treatment of uterine
leiomyoma is described. 16 (LY2066948-HCl) binds with high
affinity to estrogen receptors R and â (ERR and ERâ, respec-
tively) and is a potent uterine antagonist with minimal effects
on the ovaries as determined by serum biomarkers and
histologic evaluation.
Uterine leiomyomas, or fibroids, are the most common
type of solid tumor in adult women, clinically apparent
in at least 25% of those of reproductive age.1-3 In those
women that experience symptoms, abnormal menstrual
bleeding, pelvic pain, and infertility are the most
common. Diagnosis of uterine fibroids is the leading
cause of hysterectomies in the United States, accounting
for over 200,000 of these procedures each year. Other
invasive surgical interventions include myomectomy
and uterine artery embolization. Leiomyomas are es-
trogen responsive tumors that can be treated with
gonadotropin-releasing hormone (GnRH) agonists. These
injectable peptides inhibit estrogen synthesis and result
in the reduction of uterine volume and fibroid size.4
However, GnRH therapy can result in hot flushes and
osteoporosis, a side effect that restricts use for chronic
treatment. Because leiomyomas depend on estrogen for
growth, antagonism of this steroid hormone receptor is
a viable therapeutic approach. Along these lines, selec-
tive estrogen receptor modulators (SERMs) such as
tamoxifen and raloxifene (1) have been clinically evalu-
ated for the treatment of leiomyoma. Tamoxifen lacks
sufficient efficacy to reduce tumor size in premeno-
pausal women, in part because of the uterine agonist
characteristics exhibited by this SERM.5,6 In addition,
treatment with tamoxifen has resulted in ovarian cysts,
an undesired side effect that severely limits the use of
this compound for the treatment of fibroids in ovulatory
women. These stimulatory effects on the ovaries have
been attributed to the inhibitory properties that tamox-
* To whom correspondence should be addressed. Phone: 317-276-
8252. Fax: 317-277-2035. E-mail jdodge@lilly.com.
† Array Biopharma.
‡ Eli Lilly and Company.
10.1021/jm050723z CCC: $30.25 © 2005 American Chemical Society
Published on Web 10/01/2005

Letters
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 22 6773
Scheme 2. Synthesis of 16 and 17a
Table 1. Binding Affinity (Ki), Functional Activity (IC50), and
in Vivo Uterine Antagonist Potency (ED50) for SERMsa
ERR
Ki (nM)
ERâ
Ki (nM)
MCF-7
Ishikawa
rat ED50
(mg/kg)d
IC50 (nM)b IC50 (nM)c
1
2
9
0.37 ( 0.09 2.74 ( 1.37 0.37 ( 0.03 4.32 ( 1.69 0.55 ( 0.15
(n ) 3) (n ) 3) (n ) 2) (n ) 8) (n ) 15)
0.2 ( 0.14 0.70 ( 0.34 0.2 ( 0.02 1.14 ( 0.56 0.36 ( 0.16
(n ) 8)
1.15 ( 0.44 24.1 ( 7.67 3.4
(n ) 2) (n ) 2)
(n ) 8)
(n ) 2)
(n ) 2)
4.78 ( 3.22 0.40 ( 0.09
(n ) 3) (n ) 2)
(n ) 7)
(n ) 1)
16 0.51 ( 0.21 1.36 ( 0.34 0.86 ( 0.27 10.7 ( 6.82 0.07 ( 0.02
(n ) 6) (n ) 6) (n ) 3) (n ) 4) (n ) 3)
17 0.25 ( 0.09 0.30 ( 0.11 0.34 ( 0.14 3.18 ( 1.18 0.02
(n ) 8) (n ) 8) (n ) 3) (n ) 9) (n ) 1)
a Experimental values represent the average for multiple
determinations (n) along with the standard deviation (SD) between
the assay values. Values without SD notation were run once.
Efficacy values were >90% in all cases. b MCF-7 values are half-
maximal inhibition concentrations that block growth stimulation
by 10 pM E2. c Ishikawa IC50 values are the compound concentra-
tion needed to block 50% of 1 nM E2 stimulation as determined
by alkaline phosphatase quantitation. d Female Sprague-Dawley
rats, six per group and 19-21 days of age, were orally treated
with ethynyl estradiol (0.1 mg/kg) and 10, 1.0, 0.1, or 0.01 mg/kg
of SERM for 3 days.
a Reagents: (a) (1) NBS; (2) BnBr; (b) Cu (OTf)2, 12; (c) (1)
Pd(OH)2; (2) Tf2O; (d) Pd(OAc)2, PCy3, 6; (e) (1) HCl; (2) BBr3; (3)
HCl; (f) (1) Pd(OAc)2, PCy3, 4-fluorophenylboronic acid; (2) BBr3;
(3) HCl.
Scheme 1. Synthesis of 9a
boron trichloride followed by conversion to the triflate
gave 5. Treatment of 5 with 4-methanesulfonylphenyl-
boronic acid 6 under Suzuki cross-coupling conditions
gave 7 in quantitative yield. Reduction of the ketone
followed by treatment of the resulting alcohol with
triethylsilane/trifluoroacetic acid gave 8. Deprotection
of the aryl methyl ether using pyridine hydrochloric acid
followed by salt formation delivered 9.
In addition to modifying the 4′-position, we also
replaced the diarylmethylene group with an ether
linker. This was accomplished as shown in Scheme 2.
Bromination of 2-hydroxy-6-methoxynaphthalene (10)
by treatment with N-bromosuccinimide led to selective
bromination of the 1-position in high yield. Protection
of the phenol with benzyl bromide gave 11 in 86% yield.
Copper-mediated Ullman diaryl ether coupling with
catalytic quantities of copper triflate and 1.2 equiv of
1215 gave 13 in low (30%) but reproducible yields.
Hydrogenolysis of the benzyl group of 13 followed by
triflate formation delivered 14 in good yield. Palladium-
catalyzed Suzuki cross-coupling of this triflate with 6
gave 15. Removal of the aryl methyl ether with boron
tribromide gave the free base, which was treated with
HCl to give compound 16.
Compounds 1, 2, 9, and 16 were evaluated in a series
of estrogen-dependent in vitro and in vivo assays that
measured their affinity to the estrogen receptors and
their ability to act as functional agonists or antagonists
of estrogen. As shown in Table 1, sulfone analogue 9
binds with good affinity to estrogen receptor R (ERR)
(Ki ) 1.15 nM), is moderately selective versus ERâ (Ki
) 24.1 nM), and inhibits estrogen-induced proliferation
of breast (MCF-7, IC50 ) 3.4 nM) and uterine cells
(Ishikawa, IC50 ) 4.8 nM). In addition, 9 is not an
agonist in uterine cells in the absence of exogenous 17â-
estradiol (E2, data not shown). In immature rats treated
with ethynyl estradiol, 9 blocks the uterine weight gain
in a dose-dependent manner with an ED50 of 0.40 mg/
kg after oral administration. Subsequent structure-
activity studies led to replacement of the diarylmeth-
ylene linker in 9 with an oxygen.15 This diaryl ether
a Reagents: (a) AlCl3, 3; (b) (1) BCl3; (2) CF3SO2Cl; (c) Pd(OAc)2,
PPh3, 6; (d) (1) LAH; (2) Et3SiH, TFA; (e) (1) pyridine‚HCl; (2)
HCl.
To identify a SERM with the desired profile on the
uterus and ovaries, we initiated structure-activity
studies that included the para (4′) position of the 2-aryl
ring in 2.13 A primary strategy was to replace the 4′-
phenol with a single group that would serve two
purposes: render the molecule less susceptible to meta-
bolic conjugation and limit brain penetration. As part
of this broad SAR effort, we identified analogues such
as 9 in which the 4′-phenol has been replaced with a
methyl sulfone moiety. The sulfone group, unlike a
phenol, cannot undergo conjugative metabolism to the
glucuronide and/or sulfate ester, a characteristic that
we felt could enhance the pharmacokinetic properties
ultimately resulting in more potent in vivo uterine
antagonism. Moreover, we felt the relatively polar
nature of the sulfone group might limit the brain
penetration of this molecule.14
The synthesis of 9 is shown in Scheme 1. Friedel-
Crafts acylation of 2,6-dimethoxynaphthalene with acid
chloride 313 provided intermediate 4. Selective cleavage
of the methoxy group proximal to the carbonyl with

6774 Journal of Medicinal Chemistry, 2005, Vol. 48, No. 22
Letters
analogue (16) binds with higher affinity than 9 to both
estrogen receptors and is a potent inhibitor of MCF-7
cell proliferation (IC50 ) 0.86 nM). The effects on uterine
tissue were assessed at the in vitro level in Ishikawa
cells in the presence (antagonism) and absence (ago-
nism) of E2. In the antagonist mode, 16 blocks the
effects of 1 nM E2 by >90% with an IC50 of 10.7 nM
(Table 1). The agonist activity of 16 was similar to that
of 1 (29.0 ( 3.7% over control versus 28.6 ( 8.50% for
1) and significantly less than that of 4-hydroxytamoxifen
(123 ( 24%), a known uterine agonist. When tested in
rodents, 16 proved to be a highly potent, orally active
uterine antagonist with an ED50 of 0.07 mg/kg at
blocking estrogen-induced uterine hypertrophy in im-
mature, ovary-intact rats. Significantly, this analogue
is >5-fold more potent than 1 or 2 as a uterine
antagonist. In addition, 16 does not have agonist
properties in the uterus when administered to ovariec-
tomized (OVX) rats for 4 days at all doses examined
(0.01-10.0 mg/kg, data not shown) based on eosinophil
peroxidase activity, a sensitive marker for determining
the uterine agonist properties of SERMs.16 Long-term
treatment (42 days) of 16 to OVX rats does not cause
uterine weight gain.17 Taken together, the uterine data
indicate that 16 is a potent estrogen antagonist without
significant agonist properties in the uterus.
Pharmacokinetic analysis of 16 in rats following a
single intravenous dose at 1 mg/kg or a single oral dose
at 10 mpk indicated an oral bioavailability of 27%. The
brain-to-plasma ratio of 16 was determined after a
single oral dose of 10 mg/kg to female rats (n ) 3). In
this study we found that after 6 h, the concentration of
16 is >6-fold higher in rat plasma, 660 ( 82.8 ng/mL,
than whole brain, 102 ( 28.0 ng/g. Overall, we felt that
the potent uterine antagonist effects of 16 coupled with
the favorable brain/plasma ratio provided an appropri-
ate window for investigating whether this compound
would antagonize the uterus at concentrations that
minimally affect the ovaries
The effects of 16 on the uterus and ovaries were
studied in 6-month-old ovary-intact female rats.17 Oral
administration of 16 for 35 days at doses of 0.05, 0.5,
1.0, and 3.0 mg/kg results in a dose-dependent decrease
in uterine weight with a maximal inhibitory dose of 1
mg/kg (51% reduction in uterine wet weight) and an
ED50 of 0.15 mg/kg. Morphometric measurements at the
0.5 mg/kg dose group compared to the control group
show that the total area of the uterine wall was
significantly reduced by 53% with nearly equal contri-
butions in reduction of endometrial (54%) and myome-
trial (51%) compartments. These data confirm substan-
tial antagonist activity in both compartments of the
uterus in the presence of circulating levels of E2 over
several estrous cycles in the rat. The effects on the
ovaries in this study were determined by measuring
serum estradiol levels and histologic evaluation of
ovarian cross sections. As shown in Figure 1, treatment
with 16 results in serum E2 levels that are similar to
vehicle-treated animals at doses that exceed the inhibi-
tory effects on the uterus by greater than 60-fold.
Statistically significant increases in serum E2 levels are
observed at the high dose but are within the normal
proestrus range for Sprague-Dawley rats. Histological
evaluation of the ovaries of the rats treated with 16
Figure 1. Serum E2 levels in rats treated with 16 for 35
days: error bars ) SEM; (/) ) p < 0.05 vs control, Dunett’s
t-test.
indicates minimal ovarian stimulation relative to un-
treated controls, i.e., ovarian weights are decreased at
doses >0.5 mg/kg, there are no ovarian cysts, and
granulosa cell hyperplasia is observed in only a few
animals and generally at a mild level. These data
collectively indicate that 16 is a potent uterine antago-
nist with minimal ovarian stimulation in rats.
The origin for the uterine-ovarian selectivity is not
clear. One leading possibility is that the relatively low
brain-to-plasma ratio (0.16) observed with 16 limits this
compound’s ability to act as an antagonist of the HPO
axis at doses that also inhibit uterine growth. The
higher brain-to-plasma ratio (0.9) observed for 2, which
is ovarian stimulatory, supports this hypothesis. To
more fully test this hypothesis, we prepared (Scheme
2) and evaluated fluorine analogue 17. This compound
has a significantly lower polar surface area value (42
Å) than 16 (84 Å) and a correspondingly higher brain-
to-plasma ratio, i.e., 18 versus 0.16, respectively. In
addition, the overall concentration in rat brain is
>25-fold higher for 17 than 16, 2692 ( 211 ng/g
compared to 102 ( 28.0 ng/g, respectively. As shown in
Table 1, these SERMs have similar binding, functional,
and in vivo uterine antagonist potencies. However, oral
administration of 17 for 10 days to ovary-intact rats
results in elevated estradiol levels that are > 4-fold that
of 16 (4.6 over control compared to 1.1, respectively),
indicating that 17 is causing stimulation of the ovaries.
Elevations in estradiol levels have been observed for
tamoxifen (2.2-fold) and raloxifene (4.5-fold) in this
model.17 In longer-term studies (35 days), daily oral
administration of 17 (0.45 mg/kg) results in clear
ovarian stimulation as indicated by a 43% increase in
ovarian weight and nearly 3-fold increase in granulosa
cell hyperplasia. While we cannot rule out the possibility
that 17 has direct stimulatory effects on the ovaries,
our data are consistent with the hypothesis that de-
creased brain concentrations of 16 at the hypothalamic
loci responsible for gonadotropin production may be
responsible for limiting HPO stimulation in 16 relative
to 17. However, because at least part of the hypothala-
mus is outside the blood-brain barrier, other factors
that can lead to neutral HPO effects cannot be elimi-
nated.
Another possibility for the selectivity observed with
16 is that the interaction of this ligand with the estrogen
receptors may induce a unique receptor-ligand confir-
mation that results in tissue-specific pharmacology. To

Letters
Journal of Medicinal Chemistry, 2005, Vol. 48, No. 22 6775
information. This material is available free of charge via the
Internet at http://pubs.acs.org.
References
(1) Stewart, E. A. Uterine fibroids. Lancet 2001, 357, 293-298.
(2) Cramer, S. F.; Patel, A. The frequency of uterine leiomyomas.
Am. J. Clin. Pathol. 1990, 94, 435-438.
(3) Buttram, V. C., Jr.; Reuter, R. C. Uterine leiomyomata: etiology,
symptomatology, and management. Fertil. Steril. 1981, 36, 433-
445.
(4) Lethaby, A.; Vollenhoven, B.; Sowter, M. Efficacy of pre-operative
gonadotrophin hormone releasing analogues for women with
uterine fibroids undergoing hysterectomy or myomectomy:
a
systematic review. Br. J. Obstet. Gynecol. 2002, 109, 1097-1108.
(5) Lumsden, M. A.; West, C. P.; Baird, D. T. Tamoxifen prolongs
luteal phase in premenopausal women but has no effect on the
size of uterine fibroids. Clin. Endocrinol. 1989, 31, 335-343.
(6) Sadan, O.; Ginath, S.; Sofer, D.; Rotmensch, S.; Debby, A.;
Glezerman, M.; Zakut, H. The role of tamoxifen in the treatment
of symptomatic uterine leiomyomata. A pilot study. Eur. J.
Obstet. Gynecol. Reprod. Biol. 2001, 96, 183-186.
(7) Huppert, L. C. Induction of ovulation with clomiphene citrate.
Fertil. Steril. 1979, 31, 1-8.
(8) Palomba, S.; Sammartino, A.; Di Carlo, C.; Affinito, P.; Zullo,
F.; Nappi, C. Effects of raloxifene treatment on uterine leiomyo-
mas in postmenopausal women. Fertil. Steril. 2001, 76, 38-43.
(9) Palomba, S.; Orio, F.; Morelli, M.; Russo, T.; Pellicano, M.; Zupi,
E.; Lombardi, G.; Nappi, C.; Panici, P. L. B.; Zullo, F. Raloxifene
administration in premenopausal women with uterine leiomyo-
mas: a pilot study. J. Clin. Endocrinol. Metab. 2002, 87, 3603-
3608.
(10) Plouffe, L.; Siddhanti, S. The effect of selective estrogen receptor
modulators on parameters of the hypothalamic-pituitary-
gonadal axis. Ann. N. Y. Acad. Sci. 2001, 949, 251-158.
(11) Dodge, J. A.; Ellis, K. K.; Hay, L. A.; Koenig, T. M.; Lugar, C.;
Strouse, E. E.; Mitchell, D. Practical convergent synthesis of
SERM 2. ACS Symp. Ser. 2002, 817, 133-140.
(12) Walker, C. L.; Burroughs, K.; Davis, B.; Sowell, K.; Everitt, J.;
Fuchs-Young, R. Preclinical evidence for therapeutic efficacy of
selective estrogen receptor modulators for uterine leiomyoma.
J. Soc. Gynecol. Invest. 2000, 7, 249-256.
(13) Grese, T. A.; Cho, S.; Finley, D.; Godfrey, A. G.; Jones, C. D.;
Lugar, C. W.; Martin, M. J.; Matsumoto, K.; Pennington, L. D.;
Winter, M. W.; Adrian, M. D.; Cole, H. W.; Magee, D. E.; Phillips,
D. L.; Rowley, E. R.; Short, L. L.; Glasebrook, A. L.; Bryant, H.
U. Structure-activity relationships of selective estrogen receptor
modulators: modifications to the 2-arylbenzothiophene core of
raloxifene. J. Med. Chem. 1997, 40, 146-167.
(14) Kelder, J.; Grootenhuis, P. D. J.; Bayada, D. M.; Delbressine, L.
P. C.; Ploemen, J.-P. Polar molecular surface as a dominating
determinant for oral absorption and brain penetration of drugs.
Pharm. Res. 1999, 16, 1514-1519.
(15) Palkowitz, A. D.; Glasebrook, A. L.; Thrasher, K. J.; Hauser, K.
L.; Short, L. L.; Phillips, D. L.; Muehl, B. S.; Sato, M.; Shetler,
P. K.; Cullinan, G. J.; Pell, T. R.; Bryant, H. U. Discovery and
synthesis of [6-hydroxy-3[4-[2-(1-piperidinyl)ethoxy]phenoxy]-2-
(4-hydroxyphenyl)]benzo[b]thiophene: a novel, highly potent,
selective estrogen receptor modulator. J. Med. Chem. 1997, 40,
1407-1416.
Figure 2. (A) Superimposed crystal structures of 16 (yellow)
and 17 (teal) bound to the ligand binding domain of ERR. (B)
Orientation of 16 in ERR.
investigate this possibility, we independently crystal-
lized 16 and 17 in the ligand binding domain of ERR.
As shown in the overlay for these two crystal structures
(Figure 2A), the overall protein-ligand architectures of
the ligand-bound monomers are very similar, including
the position of helix 12, indicating that at the crystal-
lographic level 16 does not induce a conformation that
is substantially different from that of 17. One particular
note of interest (Figure 2B) is that the methyl sulfone
in 16 interacts with the His 524 side chain via a H-bond
(3.3 Å) and thus represents a novel phenol mimic among
ER ligands.
In summary, we have identified a novel ovarian
selective SERM (16) that demonstrates a wide thera-
peutic window between the desired antagonistic effects
on the uterus and the undesirable side effects on the
ovaries. In addition, bone studies demonstrate that 16
prevents ovariectomy-induced bone loss in OVX rats and
does not cause bone loss in ovary-intact rats, data which
support estrogen agonist effects on skeletal tissue.17 As
such, this compound has therapeutic potential for the
treatment of leiomyomas in premenopausal women and
is currently in clinical development.
(16) Lyttle, C. R.; DeSombre, E. R. Uterine peroxidase as a marker
for estrogen action. Proc. Natl. Acad. Sci. U.S.A. 1977, 74, 3162-
3166.
(17) Geiser, A. G.; Hummel, C. W.; Draper, M. W.; Henck, J. W.
Cohen, I. R.; Rudmann, D. G.; Donnelly, K. B.; Adrian, M. D.;
Shepherd, T. A.; Wallace, O. B.; McCann, D. J.; Oldham, S. W.;
Bryant, H. U.; Sato, M.; Dodge, J. A. A new selective estrogen
receptor modulator (SERM) with potent uterine antagonist
activity, agonist activity in bone, and minimal ovarian
stimulation Endocrinology 2005, 10.1210/en2005-0024. See
http://endo.endojournals.org for manuscript in Rapid Electronic
Publication format.
Acknowledgment. We thank Lead Optimization
Biology, M. Dee Adrian, Harlan Cole, Cassandra Gauth-
ier, Norman Hughes, Sam Oldham, Ellen Rowley, Pam
Shetler, and Tim Richardson.
Supporting Information Available: Experimental pro-
cedures for 9, 16, and 17, elemental analysis results, protocols
for all in vitro and in vivo assays, and crystallographic
JM050723Z