Identification of positron emission tomography ligands for NPY Y5 receptors in the brain

Article abstract of DOI:10.1016/j.bmcl.2009.07.103

A series of trans-3-oxospiro[(aza)isobenzofuran-1(3H),1′-cyclohexane]-4′-carboxamide derivatives were synthesized and profiled for NPY Y5 binding affinity, brain and CSF penetrability in rats, and susceptibility to human and mouse P-glycoprotein transporters in order to develop a PET ligand. Compound 12b exhibited an acceptable profile for a PET ligand, and [¹¹C]12b was successfully utilized in clinical settings as a Y5 PET ligand.

Full text of DOI:10.1016/j.bmcl.2009.07.103

Bioorganic & Medicinal Chemistry Letters 19 (2009) 5436–5439
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Identification of positron emission tomography ligands for NPY Y5 receptors
in the brain
Hirobumi Takahashi, Yuji Haga, Takunobu Shibata, Katsumasa Nonoshita, Toshihiro Sakamoto,
Minoru Moriya, Tomoyuki Ohe, Masato Chiba, Yuko Mitobe, Hidefumi Kitazawa, Hisashi Iwaasa,
*
Akane Ishihara, Yasuyuki Ishii, Akio Kanatani, Takehiro Fukami
Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd, Okubo 3, Tsukuba 300-2611, Japan
a r t i c l e i n f o
a b s t r a c t
A series of trans-3-oxospiro[(aza)isobenzofuran-1(3H),10-cyclohexane]-40-carboxamide derivatives were
synthesized and profiled for NPY Y5 binding affinity, brain and CSF penetrability in rats, and susceptibility
to human and mouse P-glycoprotein transporters in order to develop a PET ligand. Compound 12b exhib-
ited an acceptable profile for a PET ligand, and [11C]12b was successfully utilized in clinical settings as a
Y5 PET ligand.
Article history:
Received 29 May 2009
Revised 21 July 2009
Accepted 22 July 2009
Available online 25 July 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Neuropeptide Y
NPY
Positron emission tomography
PET ligand
Neuropeptide Y (NPY) is a highly conserved C-terminus amidat-
ed peptide consisting of 36 amino acid residues which has been
shown to have potent, centrally mediated orexigenic effects.1–4
At least six receptor subtypes of the NPY family have been charac-
terized based on cloning and/or their pharmacological properties.5–19
Various pharmacological studies, employing receptor deficient
mice and/or subtype-selective agonists and antagonists, have sug-
gested that the Y1 and Y5 receptors are involved in body weight
regulation.14,16,20–32 In diet-induced obese (DIO) mice, treatment
with Y5 antagonists reduced body weight in a fat mass-selective
manner, implying that Y5 receptor antagonists are useful for the
treatment of obesity. Ex vivo receptor occupancy data showed that
long-term (>15 h) Y5 receptor occupancy (>90%) is required for
efficacy in the DIO mouse model.32 We developed potent and orally
bioavailable Y5 receptor antagonists,33–37 some of which advanced
to clinical evaluation. In order to support clinical proof-of-concept
studies, it would be useful to develop a method for assessing Y5
receptor occupancy in the human brain.
clinical dosages required to achieve targeted blockade of the recep-
tor (i.e., occupancy). Studies of this type are done using radiotra-
cers labeled with short-lived positron-emitting radionuclides,
such as 11C or 18F (t1/2 = 20.4 min and 109.8 min, respectively).
The desirable properties for a candidate Y5 radioligand at least in-
clude (1) high binding affinity for the Y5 receptor and selectivity
versus other NPY receptor subtypes; (2) acceptable lipophilicity
generally falling in the log D7.4 range of 1–3 for good brain penetra-
tion and low nonspecific binding; and (3) low susceptibility to P-
glycoprotein (P-gp) transporters.
The signal to background window for a PET ligand is approxi-
mated by the ratio of Bmax/Kd, and a Bmax/Kd ratio of more than
10 is generally required. A relatively low concentration of the Y5
receptor was presumed in the brain,38 suggesting that acceptable
ligands should have high affinity of at least a low nM range. In
the course of our medicinal chemistry effort aimed at development
of drug candidates, we identified various high affinity Y5 antago-
nists. The majority of the antagonists, however, suffered from high
lipophilicity, and some of them were good substrates for P-gp
transporters. Of the Y5 antagonists we developed, the spiro[3-
oxoisobenzofurane-1(3H),40-piperidine] derivatives, exemplified
by 1a and 1b, were particularly attractive for their high Y5 binding
Positron emission tomography (PET) is a noninvasive clinical
and research imaging technique that is recognized as a powerful
tool for establishing clinical dosages of CNS drugs. Specifically de-
signed radiotracers with appropriate physical properties as well as
high affinity and selectivity for targeted receptors can be used to
obtain tomography images. In vivo competition studies using PET
tracers and unlabeled drug candidates are performed to determine
affinities (Fig. 1). They inhibited Y5-agonist [D
-Trp34]NPY-induced
food intake in rats with a minimum effective dose of 3 mg/kg po
and showed high brain Y5 receptor occupancy in mice, demon-
strating that these antagonists were active in in vivo.37 In addition,
the 3-oxoisobenzofurane structure can be labeled with 11C by a CO
insertion reaction employing palladium chemistry (Fig. 2). On top
* Corresponding author. Tel.: +81 29 877 2361; fax: +81 29 877 2029.
E-mail addresses: takehiro_fukami@merck.com, fukamith@riken.jp (T. Fukami).
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.07.103

H. Takahashi et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5436–5439
5437
O
N
O
N
10-cyclohexane]-40-carboxylic acids (9a–e). The carboxylic acids
were reacted with 2-amino-5-(substituted)phenylpyrimidines in
the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide
hydrochloride in pyridine to give the desired cold versions of PET
ligand candidates (Scheme 1).
NH
N
NH
N
N
N
O
O
In the course of our structure activity studies of the spiropiperi-
dine Y5 antagonists,36,37 we noticed that urea derivatives of phenyl-
pyrimidine produced a relatively high binding affinity as well as less
lipophilicity. Compound 1b exhibited a high Y5 binding affinity
(IC50 = 1.4 nM) and acceptable lipophilicity (log D7.4 = 2.90), thus
this structure was highlighted as a starting point for further deriva-
tization. Replacement of the urea linkage withan amide produced10
with enhanced Y5 binding affinity; however, the urea to amide
transformation resulted in an increase in lipophilicity
(log D7.4 = 3.73). Incorporation of a nitrogen atom in the benzene
ring of the 3-oxoisobenzofurane moiety was effective to decrease
the lipophilicity as shown in 11a, 13a, and 14, and those compounds
showed Y5 binding affinities in the low nM range. Introduction of a
fluorine atom into the molecules was accomplished by incorpora-
tion of F, CH2F, or OCH2F groups on the phenyl group of the phenyl-
pyrimidine moiety, and those compounds generally showed
acceptable Y5 binding affinities in the low nM range as well as
acceptable lipophilicity with log D7.4 of less than 3 (Table 1).
Based on their relatively high binding affinities and structural
diversity, 12b, 12c, 12f, 13f, and 13g were chosen for further
evaluation. The compounds were evaluated for their brain and
cerebrospinal fluid (CSF) penetrability in rats as well as suscepti-
bility to human and mouse P-gp transporters, and the results are
summarized in Table 2. The compounds showed relatively high
CSF concentrations compared with the brain concentrations. We
hypothesized that the high CSF levels were brought about by high
free fraction levels of the compounds, which may be evidence of
low nonspecific binding in the brain. The compounds seemed to
be attractive candidates for PET ligands in this aspect. In contrast,
the compounds showed brain/plasma ratios in a range of 0.1–0.5,
indicating that these compounds were good to moderate sub-
strates for the rat P-gp transporter. We examined the extent of
O
O
1a
hY5 IC50 = 2.4 nM
1b
hY5 IC50 = 1.4 nM
Figure 1.
of that, incorporation of a fluorine atom into the structure may pro-
vide additional opportunity for 18F-labeled compounds. Here we
describe the synthesis and evaluation of 3-oxoisobenzofurane
derivatives to identify Y5 PET ligands.
The preparation of cold versions of PET ligand candidates com-
prises the synthesis of trans-3-oxospiro[(aza)isobenzofuran-
1(3H),10-cyclohexane]-40-carboxylic acid portions (9a–e) and
subsequent coupling with aromatic amine partners. The carboxylic
acids (2, 4, and 5), the carboxamide (3), and the benzonitrile (6)
were treated with n-BuLi or lithium tetramethylpiperidide to gen-
erate anions, which were subsequently reacted with 1,4-cyclohex-
anedione mono-ethyleneketal followed by acid-mediated
hydrolysis to afford the spiro[(aza)benzofurane-1(3H),10-cyclohex-
ane]-3,40-diones (7a–e). Stereoselective reduction of the ketone by
NaBH4 or LiAl(OtBu)3H yielded the cis-alcohols (8a–e). The alcohols
were reacted with MsCl in the presence of Et3N, and the resulting
mesylates were reacted with Et4NCN followed by hydrolysis to
produce the desired trans-3-oxospiro[(aza)isobenzofuran-1(3H),
11CO
[Pd]
O
O
Y
X
Ar
Ar
N
N
11C
O
H
H
X
O
OH
Figure 2. Possible synthesis of a 11C-labeled ligand.
O
Br
OH
OH
Z
Y
O
2
H
N
X
O
N
W
O
3
a
9a-e
O
a
e, f, g
h
O
OH
b
Z
c or d
Z
N
OH
Y
Y
O
X
X
NH
N
O
O
O
W
W
N
4
7a-e
O
8a-e O
Z
Y
R
X
b
O
W
a
O
7a, 8a, 9a and 10: W, X, Y and Z = CH
7b, 8b, 9b and 11a-g: W = N; X, Y and Z = CH
7c 8c 9c 12a e
N
OH
,
,
and
- : X = N, W, Y and Z = CH
N
Br
CN
10, 11a-g, 12a-e, 13a-h, 14
7d, 8d, 9d and 13a-h: Y = N, W, X
and Z = CH
and : Z = N, W, X and Y = CH
7e 8e 9e
14
,
,
O
5
6
Scheme 1. Synthesis of cold versions of Y5 PET ligand candidates. Reagents and conditions: (a) n-BuLi, 1,4-cyclohexanedione mono-ethyleneketal, THF, ꢀ70 °C; then concd
HCl, H2O, acetone, 80 °C; (b) n-BuLi, 2,2,6,6,-tetramethylpiperidine, 1,4-cyclohexanedione mono-ethylene ketal, THF, ꢀ40 °C; then 6 N HCl, 80 °C; (c) NaBH4, THF, H2O, 0 °C;
(d) LiAl(OtBu)3H, THF, 0 °C; (e) MsCl, Et3N, 0 °C; (f) Et4NCN, DMF, 100 °C; (g) 30% H2SO4, 100 °C; (h) 2-amino-5-(substituted)phenylpyrimidine, 1-(3-dimethylaminopropyl)-3-
ethylcarbodiimide hydrochloride, pyridine.

5438
H. Takahashi et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5436–5439
Table 1
Human Y5 binding affinities
that these compounds were good substrates for the mouse P-gp
transporter. Assuming the rat and mouse P-gp transporters are
highly similar, the in vivo and in vitro data are consistent with
each other. In contrast, the compounds exhibited B-to-A/A-to-B
ratios of between 1 and 2 in the human L-MDR1 assay, which
suggested that these compounds were poor substrates for the hu-
man P-gp transporter. In particular, 12b showed a B-to-A/A-to-B
ratio of 1.11, which indicated that 12b was effectively not a sub-
strate for the human P-gp transporter. In addition, compound 12b
was selective for Y5 over Y1, Y2, and Y4 receptors (human Y1, Y2,
O
NH
N
N
Z
Y
X
R
O
W
O
Compounds
W
X
Y
Z
R
hY5 binding IC50a (nM) Log D7.4
and Y4 IC50 >10
date for a PET ligand.
11C]12b can be synthesized by the reaction of a tertiary alcohol
lM). Thus, 12b was selected as a primary candi-
10
CH CH CH CH
H
H
0.64 0.28
2.1b
3.73
2.32
NT
2.48
NT
11a
11b
11c
11d
11e
11f
N
N
N
N
N
N
CH CH CH
CH CH CH o-F
CH CH CH m-F
CH CH CH p-F
CH CH CH o-OCH2F
CH CH CH m-
OCH2F
3.0b
[
2.2b
precursor 19 and 11CO in the presence of Pd(PPh3)4.41,42 The ter-
tiary alcohol precursor 19 was synthesized according to the meth-
od described in Scheme 2. 3-Bromopyridine was reacted with LDA
followed by 1,4-cyclohexanedione mono-ethyleneketal and acid-
mediated hydrolysis to afford 16. The ketone was stereoselectively
reduced by NaBH4 to afford the cis-alcohol 17. Mesylation of the
alcohol, followed by reaction with NEt4CN and acid-mediated
hydrolysis gave the trans carboxylic acid 18, which was coupled
with 2-amino-5-o-fluorophenylpyrimidine to produce the precur-
sor 19.
7.5b
4.5b
NT
NT
3.1b
11g
12a
12b
12c
12d
12e
12f
N
CH CH CH m-CH2F
2.3b
NT
NT
2.79
2.78
NT
CH
CH
CH
CH
CH
CH
N
N
N
N
N
N
CH CH
H
2.0b
CH CH o-F
CH CH m-F
CH CH p-F
CH CH o-OCH2F
CH CH m-
OCH2F
1.5 0.3
1.5 0.2
2.2b
2.2b
NT
2.71
1.8 0.4
In preliminary studies in rhesus monkeys, images of [11C]12b
binding were obtained in the brain, and a Y5 receptor-specific sig-
nal was achieved in the striatum region as reported separately.42
Therefore, the ligand subsequently was studied in humans where
it also produced the Y5 receptor-specific signal in the human brain.
In clinical trials of the Y5 receptor antagonist MK-0557, [11C]12b
was used to assess the receptor occupancy produced by oral
administration of MK-0557.43 The receptor occupancy data as-
sessed by using the PET ligand [11C]12b was consistent with the
efficacy data obtained in the dose-ranging study, confirming the
dosage employed in the long-term weight-loss study. Thus, this li-
gand was useful to support clinical proof-of-concept studies of the
Y5 antagonist MK-0557.
13a
13b
13c
13d
13e
13f
13g
13h
14
CH CH
CH CH
CH CH
CH CH
CH CH
CH CH
CH CH
CH CH
N
N
N
N
N
N
N
N
CH
CH o-F
CH m-F
CH p-F
CH o-OCH2F
CH mOCH2F
CH o-CH2F
CH m-CH2F
H
1.8b
2.65
2.79
2.80
NT
2.71
2.75
2.54
2.65
2.71
1.8 0.4
1.8 0.3
2.7b
2.6b
1.9 0.1
2.0 0.3
1.8 0.2
2.9b
CH CH CH
N
H
a
[
125I]PYY binding to human recombinant Y5 receptors in LMtk-cells (see Ref.
39). Values represent mean standard deviation of at least three separate
experiments.
b
n = 2 IC50 determination.
In summary, we synthesized
a series of trans-3-oxospi-
ro[(aza)isobenzofuran-1(3H),10-cyclohexane]-40-carboxamide deri-
vatives as candidates for a Y5 PET ligand. The compounds were
evaluated for their Y5 binding affinities as well as lipophilicity,
brain and CSF penetrability in rats, and in vitro P-gp susceptibility
in humans and mice. Of the compounds synthesized, 12b was po-
tent as a Y5 receptor and selective over Y1, Y2, and Y4 receptors.
Compound 12b had acceptable lipophilicity and moderate brain
penetrability as well as excellent CSF penetrability. In addition,
12b was not a substrate for the human P-gp transporter although
it was a good substrate for the mouse P-gp transporter. Thus,
12b was selected as a candidate for the Y5 PET ligand, and
P-gp-mediated transport by using the polarized pig kidney epi-
thelial cell lines (LLC-PK1) transfected with human P-gp cDNA
(L-MDR1) or mouse P-gp (mdr1a) cDNA. For P-gp substrate, the
transcellular transport of compound in the direction of basolat-
eral-to-apical (B-to-A) compartment exceeds that in the opposite
direction (A-to-B), since P-gp is located inside cell on the apical
membrane catalyzing efflux transport of substrate from inside
cell to apical compartment. Therefore, the value of relative rate
of polarized transport (B-to-A/A-to-B) serves as an index for the
extent of P-gp substrate susceptibility in P-gp-expressing cell
monolayers.40 In the in vitro P-gp transporter assay, these com-
pounds exhibited relatively high basal-to-apical (B-to-A)/apical-
to-basal (A-to-B) ratios of >4 in mouse L-mdr1a, which suggested
[
11C]12b proved to be an acceptable PET ligand for imaging of brain
Y5 receptors in humans.
Table 2
Plasma, brain, and CSF level data in rats and susceptibility to P-gp transporters
Compounds
Plasma, brain and CSF levels after 3 mg/kg iv in ratsa
Susceptibility to P-gp transportersb (B-to-A/A-to-B ratio)
Plasma (
l
M)
Brain (lM)
CSF (lM)
Brain/plasma ratio
CSF/brain ratio
Human L-MDR1c
Mouse L-mdr1ad
12b
12c
12f
13f
13h
3.10
3.45
1.50
2.04
1.22
1.55
1.42
0.15
0.74
0.37
0.288
0.308
0.064
0.095
0.079
0.50
0.41
0.11
0.37
0.30
0.19
0.22
0.42
0.13
0.22
1.11
1.41
1.52
1.37
1.69
4.43
7.78
9.51
8.23
7.90
a
Results represent the average of three animals.
Transcellular transport across the monolayers of L-MDR1 or L-mdr1a. Values represent the ratio of basal-to-apical (B-to-A) versus apical-to-basal (A-to-B) at 3 h.
Human MDR1 transfectants.
Mouse mdr1a transfectants.
b
c
d

H. Takahashi et al. / Bioorg. Med. Chem. Lett. 19 (2009) 5436–5439
5439
O
O
OH
HO
Br
HO
OH
a
b
c, d, e
HO
N
N
N
15
Br
Br
N
16
Br
17
18
O
O
NH
NH
N
N
g
f
N
N
HO
F
F
N
O
11C
O
Br
N
11
19
12b
C]
[
Scheme 2. Synthesis of [11C]12b. Reagents and conditions: (a) LDA, 1,4-cyclohexanedione mono-ethyleneketal, MTBE-DME, <ꢀ70 °C; then p-TsOH, H2O, acetone, reflux; (b)
NaBH4, THF, H2O, <0 °C; (c) MsCl, NEt3, THF, 0 °C; (d) NEt4CN, 1,4-dioxane, 100 °C; (e) 30% H2SO4, 95 °C; (f) 2-amino-5-(2-fluorophenyl)pyrimidine, DMC, pyridine, CHCl3; (g)
See Refs. 41 and 42.
D. A.; Simmons, R. M. A.; Swanson, S.; Zarrinmayeh, H.; Zimmerman, D. M.;
Gehlert, D. R. J. Med. Chem. 1997, 40, 3712.
Acknowledgments
23. Kanatani, A.; Ito, J.; Ishihara, A.; Iwaasa, H.; Fukuroda, T.; Fukami, T.; MacNeil,
We thank Dr. Lex H. T. Van der Ploeg, Dr. Douglas J. MacNeil, Dr.
Raymond E. Gibson, Dr. Donald Burns and Dr. Terence G. Hamill for
their suggestions and discussion on the NPY Y5 receptor antagonist
program and PET ligand development. We are grateful to Dr. Peter
T. Meinke, Merck Research Laboratories, for his critical reading of
the manuscript.
D. J.; Van der Ploeg, L. H. T.; Ihara, M. Regul. Pept. 1998, 75, 409.
24. Kask, A.; Rago, L.; Harro, J. Br. J. Pharmacol. 1998, 124, 1507.
25. Marsh, D. J.; Hollopeter, G.; Kafer, K. E.; Palmiter, R. D. Nat. Med. 1998, 4, 718.
26. Pedrazzini, T.; Seydoux, J.; Kunstner, P.; Aubert, J. F.; Grouzmann, E.; Beermann,
F.; Brunner, H. R. Nat. Med. 1998, 4, 722.
27. Wieland, H. A.; Engel, W.; Eberlein, W.; Rudolf, K.; Doods, H. N. Br. J. Pharmacol.
1998, 125, 549.
28. Inui, A. Trends Pharmacol. Sci. 1999, 20, 43.
29. Kanatani, A.; Kanno, T.; Ishihara, A.; Hata, M.; Sakuraba, A.; Tanaka, T.;
Tsuchiya, Y.; Mase, T.; Fukuroda, T.; Fukami, T.; Ihara, M. Biochem. Biophys. Res.
Commun. 1999, 266, 88.
References and notes
30. Kanatani, A.; Mashiko, S.; Murai, N.; Sugimoto, N.; Ito, J.; Fukuroda, T.; Fukami,
T.; Morin, N.; MacNeil, D. J.; Van der Ploeg, L. H. T.; Saga, Y.; Nishimura, S.;
Ihara, M. Endocrinology 2000, 141, 1011.
31. Kanatani, A.; Hata, M.; Mashiko, S.; Ishihara, A.; Okamoto, O.; Haga, Y.; Ohe, T.;
Kanno, T.; Murai, N.; Ishii, Y.; Fukuroda, T.; Fukami, T.; Ihara, M. Mol. Pharmacol.
2001, 59, 501.
32. Ishihara, A.; Kanatani, A.; Mashiko, S.; Tanaka, T.; Hidaka, M.; Gomori, A.;
Iwaasa, H.; Murai, N.; Egashira, S.; Murai, T.; Mitobe, Y.; Matsushita, H.;
Okamoto, O.; Sato, N.; Jitsuoka, M.; Fukuroda, T.; Ohe, T.; Guan, X. M.; MacNeil,
D. J.; Van der Ploegn, L. H. T.; Nishikibe, M.; Ishii, Y.; Ihara, M.; Fukami, T. Proc.
Natl. Acad. Sci. U.S.A. 2006, 103, 7154.
33. Sato, N.; Takahashi, T.; Shibata, T.; Haga, Y.; Sakuraba, A.; Hirose, M.; Sato, M.;
Nonoshita, K.; Koike, Y.; Kitazawa, H.; Fujino, N.; Ishii, Y.; Ishihara, A.; Kanatani,
A.; Fukami, T. J. Med. Chem. 2003, 46, 666.
34. Takahashi, T.; Sakuraba, A.; Hirohashi, T.; Shibata, T.; Hirose, M.; Haga, Y.;
Nonoshita, K.; Kanno, T.; Ito, J.; Iwaasa, H.; Kanatani, A.; Fukami, T.; Sato, N.
Bioorg. Med. Chem. 2006, 14, 7501.
35. Sato, N.; Jitsuoka, M.; Shibata, T.; Hirohashi, T.; Nonoshita, K.; Moriya, M.; Haga,
Y.; Sakuraba, A.; Ando, M.; Ohe, T.; Iwaasa, H.; Gomori, A.; Ishihara, A.;
Kanatani, A.; Fukami, T. J. Med. Chem. 2008, 51, 4765.
36. Sakamoto, T.; Moriya, M.; Haga, Y.; Takahashi, T.; Shibata, T.; Okamoto, O.;
Nonoshita, K.; Kitazawa, H.; Hidaka, M.; Gomori, A.; Iwaasa, H.; Ishihara, A.;
Kanatani, A.; Fukami, T.; Gao, Y. D.; MacNeil, D. J.; Yang, L. Bioorg. Med. Chem.
Lett. 2009, 19, 1564.
37. Takahashi, T.; Haga, Y.; Sakamoto, T.; Moriya, M.; Okamoto, O.; Nonoshita, K.;
Shibata, T.; Suga, T.; Takahashi, H.; Hirohashi, T.; Sakuraba, A.; Gomori, A.;
Iwaasa, H.; Ohe, T.; Ishihara, A.; Ishii, Y.; Kanatani, A.; Fukami, T. Bioorg. Med.
Chem. Lett. 2009, 19, 3511.
1. Tatemoto, K.; Mutt, V. Nature 1980, 285, 417.
2. Tatemoto, K.; Carlquist, M.; Mutt, V. Nature 1982, 296, 659.
3. Clark, J. T.; Kalra, P. S.; Crowley, W. R.; Kalra, S. P. Endocrinology 1984, 115, 427.
4. Mccarthy, H. D.; Mckibbin, P. E.; Holloway, B.; Mayers, R.; Williams, G. Life Sci.
1991, 49, 1491.
5. Eva, C.; Oberto, A.; Sprengel, R.; Genazzani, E. FEBS Lett. 1992, 314, 285.
6. Herzog, H.; Hort, Y. J.; Ball, H. J.; Hayes, G.; Shine, J.; Selbie, L. A. Proc. Natl. Acad.
Sci. U.S.A. 1992, 89, 5794.
7. Krause, J.; Eva, C.; Seeburg, P. H.; Sprengel, R. Mol. Pharmacol. 1992, 41, 817.
8. Larhammar, D.; Blomqvist, A. G.; Yee, F.; Jazin, E.; Yoo, H. Y.; Wahlestedt, C. J.
Biol. Chem. 1992, 267, 10935.
9. Bard, J. A.; Walker, M. W.; Branchek, T. A.; Weinshank, R. L. J. Biol. Chem. 1995,
270, 26762.
10. Gerald, C.; Walker, M. W.; Vaysse, P. J. J.; He, C. G.; Branchek, T. A.; Weinshank,
R. L. J. Biol. Chem. 1995, 270, 26758.
11. Lundell, I.; Blomqvist, A. G.; Berglund, M. M.; Schober, D. A.; Johnson, D.;
Statnick, M. A.; Gadski, R. A.; Gehlert, D. R.; Larhammar, D. J. Biol. Chem. 1995,
270, 29123.
12. Rose, P. M.; Fernandes, P.; Lynch, J. S.; Frazier, S. T.; Fisher, S. M.; Kodukula, K.;
Kienzle, B.; Seethala, R. J. Biol. Chem. 1995, 270, 22661.
13. Gehlert, D. R.; Beavers, L. S.; Johnson, D.; Gackenheimer, S. L.; Schober, D. A.;
Gadski, R. A. Mol. Pharmacol. 1996, 49, 224.
14. Gerald, C.; Walker, M. W.; Criscione, L.; Gustafson, E. L.; BatzlHartmann, C.;
Smith, K. E.; Vaysse, P.; Durkin, M. M.; Laz, T. M.; Linemeyer, D. L.; Schaffhauser,
A. O.; Whitebread, S.; Hofbauer, K. G.; Taber, R. I.; Branchek, T. A.; Weinshank,
R. L. Nature 1996, 382, 168.
15. Gregor, P.; Millham, M. L.; Feng, Y.; Decarr, L. B.; McCaleb, M. L.; Cornfield, L. J.
FEBS Lett. 1996, 381, 58.
16. Gregor, P.; Feng, Y.; Decarr, L. B.; Cornfield, L. J.; McCaleb, M. L. J. Biol. Chem.
1996, 271, 27776.
17. Hu, Y. H.; Bloomquist, B. T.; Cornfield, L. J.; Decarr, L. B.; FloresRiveros, J. R.;
Friedman, L.; Jiang, P. L.; LewisHiggins, L.; Sadlowski, Y.; Schaefer, J.; Velazquez,
N.; McCaleb, M. L. J. Biol. Chem. 1996, 271, 26315.
18. Matsumoto, M.; Nomura, T.; Momose, K.; Ikeda, Y.; Kondou, Y.; Akiho, H.;
Togami, J.; Kimura, Y.; Okada, M.; Yamaguchi, T. J. Biol. Chem. 1996, 271, 27217.
19. Weinberg, D. H.; Sirinathsinghji, D. J. S.; Tan, C. P.; Shiao, L. L.; Morin, N.; Rigby,
M. R.; Heavens, R. H.; Rapoport, D. R.; Bayne, M. L.; Cascieri, M. A.; Strader, C.
D.; Linemeyer, D. L.; MacNeil, D. J. J. Biol. Chem. 1996, 271, 16435.
20. Daniels, A. J.; Matthews, J. E.; Slepetis, R. J.; Jansen, M.; Viveros, O. H.; Tadepalli,
A.; Harrington, W.; Heyer, D.; Landavazo, A.; Leban, J. J.; Spaltenstein, A. Proc.
Natl. Acad. Sci. U.S.A. 1995, 92, 9067.
21. Kanatani, A.; Ishihara, A.; Asahi, S.; Tanaka, T.; Ozaki, S.; Ihara, M. Endocrinology
1996, 137, 3177.
22. Hipskind, P. A.; Lobb, K. L.; Nixon, J. A.; Britton, T. C.; Bruns, R. F.; Catlow, J.;
DieckmanMcGinty, D. K.; Gackenheimer, S. L.; Gitter, B. D.; Iyengar, S.; Schober,
38. Dumont, Y.; Jacques, D.; Bouchard, P.; Quirion, R. J. Comp. Neurol. 1998, 402,
372.
39. Kanatani, A.; Ishihara, A.; Iwaasa, H.; Nakamura, K.; Okamoto, O.;
Hidaka, M.; Ito, J.; Fukuroda, T.; MacNeil, D. J.; Van der Ploeg, L. H.
T.; Ishii, Y.; Okabe, T.; Fukami, T.; Ihara, M. Biochem. Biophys. Res.
Commun. 2000, 272, 169.
40. Yamazaki, M.; Neway, W. E.; Ohe, T.; Chen, I. W.; Rowe, J. F.; Hochman, J. H.;
Chiba, M.; Lin, J. H. J. Pharmacol. Exp. Ther. 2001, 296, 723.
41. Burns, H. D.; Gibson, R. E.; Hamill, T. G.; Fukami, T. WO 2003010175, 2002;
Chem. Abstr. 2002, 138, 137598.
42. Hostetler, E.; Sanabria, S.; Krause, S.; Ryan, C.; Francis, B.; Eng, W. S.;
Hargreaves, R.; Burns, D. Neuroimage 2006, 31, T16.
43. Erondu, N.; Gantz, I.; Musser, B.; Suryawanshi, S.; Mallick, M.; Addy, C.; Cote, J.;
Bray, G.; Fujioka, K.; Bays, H.; Hollander, P.; Sanabria-Bohórquez, S. M.; Eng,
W.; Långströ, B.; Hargreaves, R. J.; Burns, H. D.; Kanatani, A.; Fukami, T.;
MacNeil, D. J.; Gottesdiener, K. M.; Amatruda, J. M.; Kaufman, K. D.; Heymsfield,
S. B. Cell Metab. 2006, 4, 275.