Discovery of NVP-LEQ506, a second-generation inhibitor of smoothened

Article abstract of DOI:10.1002/cmdc.201300217

First disclosure: Continued optimization provided a novel type of Smoothened (Smo) antagonist based on a pyridazine core. The compound, NVP-LEQ506, currently in phaseI clinical trials, combines high intrinsic potency and good pharmacokinetic properties resulting in excellent efficacy in rodent tumor models of medulloblastoma. Activity against a Smo mutant conferring resistance observed in a previous clinical trial with a competitor compound suggests additional therapeutic potential.

Full text of DOI:10.1002/cmdc.201300217

CHEMMEDCHEM
COMMUNICATIONS
DOI: 10.1002/cmdc.201300217
Discovery of NVP-LEQ506, a Second-Generation Inhibitor
of Smoothened
Stefan Peukert,* Feng He, Miao Dai, Rui Zhang, Yingchuan Sun, Karen Miller-Moslin,
Michael McEwan, Bharat Lagu, Kate Wang, Naeem Yusuff, Aaron Bourret, Arun Ramamurthy,
Wieslawa Maniara, Adam Amaral, Anthony Vattay, Anlai Wang, Ribo Guo, Jing Yuan,
John Green, Juliet Williams, Silvia Buonamici, Joseph F. Kelleher, III, and Marion Dorsch[a]
The Hedgehog (Hh) pathway plays an important role in embry-
onic development and tissue patterning and a lesser role in
adults for tissue maintenance and repair.[1,2] Smoothened
(Smo), a 7-pass transmembrane receptor with a GPCR-like ar-
chitecture, is a key component of the Hh signaling pathway,
the activity of which is suppressed by the 12-pass transmem-
brane protein Patched (Ptch).[3] Binding of secreted proteins of
the Hh family to Ptch results in relief of the suppres-
sion of Smo, initiating downstream signaling and ac-
tivation of Gli transcription factors which lead to cell
proliferation, differentiation and survival. Genetic acti-
vation of the Hh pathway, mostly by Ptch loss-of-
function or Smo gain-of-function mutations, has
been linked to tumorigenesis in cancers such as
basal cell carcinoma (BCC) and medulloblastoma.[4,5]
Furthermore, up-regulation of the pathway has been
linked to tumor growth in pancreatic, prostate, lung,
colorectal, bladder, and ovarian cancers.[6] Recently,
Smo-dependent non-canonical signaling through
a Ca2+-Ampk axis has been implicated in stimulating
glucose uptake, resulting in Warburg-like metabolism
in muscle and brown fat.[7] Smo antagonists such as
vismodegib/GDC-0449 (1)[8,9] and sonidegib/NVP-
LDE225 (2)[10] have demonstrated clinical response in
toward the identification of compounds with further improved
potency to achieve optimal efficacy.
Based on our previously published 1-amino-4-benzylphthala-
zine 3a,[18] we aimed for compounds with better potency, de-
creased hERG activity, and improved aqueous solubility by
truncating the bicyclic phthalazine core to yield compounds of
general structure 4 (Figure 1). Herein we describe our research
Figure 1. Structures of vismodegib, sonidegib, and the strategy used to identify pyrida-
zines 4 based on the previously reported lead compound 3a.
patients with BCC and medulloblastoma.[11,12] Vismo-
degib was approved in January 2012 by the US Food
and Drug Administration (FDA) for the treatment of
adults with metastatic or locally advanced BCC.[13] However, mi-
cromolar concentrations are required in preclinical models for
efficacy,[14,15] and in at least one patient, loss of efficacy oc-
curred from a single point mutation in Smo that prevented the
binding of 1.[16] Furthermore, adverse events of muscle spasms
and weight loss occurred in >50% of the patients,[17] possibly
related to activation of non-canonical Hh signaling.[7] Thus, our
efforts for a second-generation Smo antagonist were directed
resulting in the discovery of NVP-LEQ506 (12b) which is cur-
rently in clinical development.
The preparation and characterization of phthalazines 3 has
been previously described,[18] while compounds of general
structure 4 were synthesized by starting from readily available
3,6-dichloropyridazines 5 (Scheme 1). In the first route, Negishi
coupling[19] with benzylzinc bromides provided the mono-
chloro intermediates 6 which reacted under thermal conditions
with N-arylpiperazines to yield compounds 7. Intermediate 6b
was converted with excess piperazines to afford compounds
10a–c. Piperazines with an alkyl substituent at the 2-position
selectively afforded the regioisomers 10b,c depicted in
Scheme 1. Compound 10d was prepared with the synthetic
steps reversed: First, 5b was heated in the presence of N-Boc-
(R)-2-ethylpiperazine to yield intermediate 9, which was then
submitted to Negishi coupling with benzylzinc bromide to
afford 10d after removal of the Boc protecting group. All com-
pounds 10 were subsequently treated with methyl 5-chloro-
[a] Dr. S. Peukert, Dr. F. He, M. Dai, R. Zhang, Y. Sun, Dr. K. Miller-Moslin,
M. McEwan, Dr. B. Lagu, K. Wang, Dr. N. Yusuff, A. Bourret, A. Ramamurthy,
Dr. W. Maniara, A. Amaral, A. Vattay, A. Wang, R. Guo, J. Yuan, J. Green,
Dr. J. Williams, Dr. S. Buonamici, Dr. J. F. Kelleher, III, Dr. M. Dorsch
Novartis Institutes for Biomedical Research (NIBR)
250 Massachusetts Avenue, Cambridge, MA 02139 (USA)
E-mail: stefan.peukert@novartis.com
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cmdc.201300217.
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1261 – 1265 1261

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
Scheme 1. Synthesis of pyridazines. Reagents and conditions: a) benzylzinc bromide, Pd(PPh3)4, THF, 50–658C; b) 1-aryl piperazine, Et3N, NMP, 190–2108C, mi-
crowave; c) MeMgBr or MeMgI, THF, ꢀ788C!RT; d) piperazine, Et3N, dioxane, NMP, 1908C, microwave; e) chloro arene, Et3N, dioxane, 808C or NMP, 1908C,
microwave; f) N-Boc-(R)-2-ethyl piperazine, K2CO3, DMF, 608C; g) 1. a), 2. TFA, CH2Cl2; h) EtMgI, THF, ꢀ788C!RT; i) (R)-2-methyl piperazine, K2CO3, DMF, 508C;
j) 15a: phenol, K3PO4, tBu-XPhos, toluene, 1008C; 15b: aniline, 1908C, microwave.
pyrazine-2-carboxylate to provide esters 11. Inter-
Table 1. Smo antagonism, solubility, and hERG activity of phthalazines 3.
mediate 13 was prepared by the reaction of (R)-2-
methylpiperazine with 3,6-dichloropyridazine 5b.
Compound 14 was generated by thermal reaction of
13 with methyl 5-chloropyrazine-2-carboxylate. The
phenoxy substituent in compound 15a was installed
under palladium catalysis,[20] whereas the aniline was
introduced in low yield to afford compound 15b in
a non-catalyzed transformation. Tertiary alcohols 8,
12, and 16 were all prepared from the corresponding
methyl esters by reaction with excess MeMgBr/I or
EtMgI.
Gli shift [nm][a]
Compd
R1
1 nm
25 nm
Sol. [mm][b]
hERG IC50 [mm][c]
3a
3b
3c
3d
C(CH3)2OH
C(CH3)2NH2
CO2H
3
1
35
42
>5000
136
<5
731
25
1.5
1.4
>30
8.8
2665
17
C(CH2OH)(CH3)OH
33
[a] See the Supporting Information for a detailed description of the assay. [b] Aqueous
equilibrium solubility at pH 6.8. [c] Values determined in a [3H]dofetilide hERG binding
assay.
All compounds were evaluated in a cell-based re-
porter gene assay for their ability to inhibit the Hh
pathway. The ability of compounds to inhibit path-
way activity in a mouse cell line (TM3) was tested by
competition with a Smo agonist at two different con-
centrations: 1 and 25 nm. A shift to a higher IC50 at the higher
agonist concentration in the TM3-Gli-luc IC50 assay (“Gli shift”)
suggested antagonism of Smo.
cessful in achieving both goals simultaneously: Basic ionizable
substituents led to potent hERG inhibition (compound 3b),
whereas acidic ionizable groups resulted in loss of potency
(compound 3c). Polar substituents, as exemplified by com-
pound 3d, typically resulted in a moderate improvement in
hERG inhibition, but also in decreased Smo potency. Therefore,
we pursued the idea of truncating the phthalazine core, which
Our initial attempts to increase aqueous solubility and de-
crease hERG activity while maintaining the good potency of
3a focused on the substituent R1 (Table 1). However, various
approaches, as represented by examples 3b–d, were unsuc-
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1261 – 1265 1262

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
increase in lipophilicity for 12b relative to 12a (clogP=3.1
and 2.6 for 12b and 12a), and we attribute this finding to the
lower melting point of 12b relative to that of 12a (132 vs.
1618C). The R enantiomer 12b is ~2-fold more potent than
the S enantiomer 12c. An analysis of several enantiomeric
pairs shows that the R-configured R2 enantiomers are consis-
tently more potent than the corresponding S-configured R2
enantiomer (data not shown). Further increase in steric bulk
for either substituents R2 or R1 is detrimental for the aqueous
solubility of the compounds (compounds 12d and e) and does
not provide any additional gain in potency. Notably, replace-
ment of the benzylic methylene linker with an oxygen atom
(compound 16a) is well tolerated, whereas replacement with
an NH group (compound 16b) results in a ~10-fold decrease
in inhibition of the Hh pathway. These two compounds dem-
onstrate the sensitive nature of the structure–solubility rela-
tionship. Despite increases in polar surface areas for both com-
pounds 16a and 16b relative to 12b (87.3, 90.3, and 78.3 ꢁ
for 16a, b, and 12b) a drop in solubility is observed.[21]
Overall, compound 12b provided the best combination of
excellent potency in the Gli-luc assay, low hERG channel bind-
ing, which was substantiated in an automated patch clamp
assay, and acceptable aqueous solubility to minimize the po-
tential for solubility-limited absorption. Therefore, 12b was se-
lected for a detailed in vitro evaluation (Table 4). Binding
assays, using both human and mouse receptor, confirmed that
12b targets Smo within the Hh pathway and binds to both re-
Table 2. Smo antagonism of phthalazine 3e versus pyridazines 7.
Gli shift [nm][a]
1 nm
Compd
R1
R2
25 nm
3e
7a
7b
7c
7d
benzo
–(CH2)3–
134
97
90
1327
508
733
>5000
>5000
CH3
H
H
CH3
CH3
H
251
>5000
[a] See the Supporting Information for a detailed description of the assay.
we suspected to be a contributor to the low aqueous solubility
of 3a. Table 2 shows structure–activity relationships developed
for pyridazines 7a–d in comparison with phthalazine 3e. Re-
placement of the annelated benzene ring with either a cyclo-
pentyl ring or two methyl groups afforded compounds with
similar or better potency than the original phthalazine (com-
pounds 7a,b). A further decrease in the size of the pyridazine
substituents R1 and R2 was not tolerated, as demonstrated
with compounds 7c and 7d. We used compound 7b, with its
increased ligand efficiency over 3e, as a starting point for a sys-
tematic optimization of this new scaffold (Table 3). Installment
of the 2-hydroxypropyl group (compound 8) resulted in good
potency, but the compound still suffered from low aqueous
solubility and potent hERG activity. Replacement of the 2-pyr-
idyl ring with a 2-pyrazine ring afforded very good potency
with improved solubility and no significant binding to the
hERG channel (compound 12a). We retained the 2-pyrazine
ring and focused further optimization on the piperazine sub-
stituents. A methyl substituent on the piperazine linker result-
ed in a further increase in aqueous solubility (compound 12b
vs. 12a). Improved solubility was observed despite an overall
Table 4. In vitro potency of 12b in comparison with 2.[a]
IC50 [nm]
Compd
human Smo
mouse Smo
HEPM[b]
Smo D473H
12b
2
2
11
4
12
2
13
96
–
[a] See the Supporting Information for detailed descriptions of all assays.
[b] HEPM=human embryonic palatal mesenchymal.
ceptors with higher affinity than
2. Similarly, 12b inhibited Hh
signaling in a human cell line
(HEPM) as measured by the
amount of Gli mRNA with an IC50
~6-fold lower than that of 2.
Furthermore, 12b was tested in
Table 3. Smo antagonism, solubility, and hERG activity of pyridazines 8, 12, and 16.
Gli shift [nm][a]
luciferased
C3H10T1/2
cells
Compd
R1
R2
R3
X
Y
1 nm
25 nm
Sol. [mm][b]
hERG IC50 [mm][c]
transfected with a Smo D473H
expression vector. Smo D473H is
the mutation which conferred
resistance to 1 in a medulloblas-
toma patient after an initial re-
sponse.[16] Remarkably, when
tested in this mutant cell line,
12b retained good potency
(IC50 <100 nm).[22]
8
C(CH3)2OH
C(CH3)2OH
C(CH3)2OH
C(CH3)2OH
C(CH3)2OH
C(CH2CH3)2OH
C(CH3)2OH
C(CH3)2OH
H
H
F
CH
N
N
N
N
N
N
N
CH2
CH2
CH2
CH2
CH2
CH2
O
5
2
1
2
4
1
2
13
76
60
10
34
57
18
24
162
<5
11
34
–
1.3
12a
12b
12c
12d
12e
16a
16b
H
H
H
H
H
H
H
>30
30
–
>30
–
(R)-CH3
(S)-CH3
(R)-CH2CH3
(R)-CH3
(R)-CH3
(R)-CH3
7
<5
<5
<5
–
–
NH
[a] See the Supporting Information for a detailed description of the assay. [b] Aqueous equilibrium solubility at
pH 6.8. [c] Values determined in a [3H]dofetilide hERG binding assay.
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1261 – 1265 1263

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
ficacy with a 3–8-fold lower exposure in plasma and
tumor as a result of its higher intrinsic potency (see
Table 4). The higher dose required for 12b is a conse-
quence of its shorter half-life in rodents (t1/2 =1.2–
1.4 h, see Table 5) in comparison with 2 (t1/2 =3.9–
4.2 h). We also measured inhibition of the Hh path-
way in tumors upon treatment with 12b in Ptch+/ꢀ
Hicꢀ/ꢀ medulloblastoma-bearing mice. Tumors were
harvested at various time points after the third
dosing, and expression of Gli1 mRNA as a marker of
Hh pathway activity was analyzed. Almost complete
Table 5. In vivo PK properties of 12b among preclinical species.
[d]
[d]
Species
CL[d]
[mLminꢀ1 kgꢀ1
Vss
t1/2
[h]
AUC0–1/dose[e]
F
[%]
]
[Lkgꢀ1
]
mmh/[mgkgꢀ1
]
mouse[a]
rat[b]
dog[c]
21
29
3
1.5
1.6
0.5
1.2
1.4
2.2
2.83
0.54
>100
41
10.2
77
[a] Dose: 1 mgkgꢀ1 i.v., 10 mgkgꢀ1 p.o., vehicle (i.v., p.o.): 5% NMP/10% PEG400/35%
of 10% ETPGS/50% D5W. [b] Dose: 1 mgkgꢀ1 i.v., 10 mgkgꢀ1 p.o., vehicle (i.v.): 20%
captisol, vehicle (p.o.): 0.5% NaCMC suspension. [c] Dose: 0.1 mgkgꢀ1 i.v., 0.3 mgkgꢀ1
p.o., vehicle (i.v., p.o.): 20% captisol. [d] After i.v. dosing. [e] After p.o. dosing.
Compound 12b shows good bioavailability in pre-
Table 6. PK/efficacy relationship for 12b and 2 in Ptch+/ꢀ Hicꢀ/<M-> rodent models.[a]
clinical species ranging from 41 to >100% (Table 5).
Systemic plasma clearance (CL) is low (dog and
mouse) to moderate (rat), relative to the respective
hepatic blood flow, while the volume of distribution
at steady state (Vss) is low (dog) to moderate (mouse,
Species
Dose
[mgkgꢀ1
Tumor
Regression [%][c]
Tumor Exposure
[AUC0–24h, mmh][d]
Plasma Exposure
[AUC0–24h, mmh][d]
[b]
]
Mouse
12b
2
40
20
85
91
32.1
259.5
45.3
141.5
rat) relative to total body volume. The half-life (t1/2
)
Rat
12b
2
after i.v. dosing ranges from 1.2 to 2.2 h. The com-
pound is able to penetrate the blood–brain barrier as
indicated by a brain/plasma AUC0–1 ratio of 0.69
after a single dose of 20 mgkgꢀ1 in mice, which is an
important requirement for treating brain tumors.
Next, we determined the efficacy of 12b in direct
comparison against our first-generation inhibitor 2 in
a mouse medulloblastoma allograft model. It is well
established that mice heterozygous for a loss-of-func-
tion mutation in Ptch (Ptch+/ꢀ) develop medulloblas-
10
5
98
99
25.0
105.3
30.6
138.4
[a] See the Supporting Information for detailed study conditions. [b] 12b was dosed
p.o. as a 0.5% NaCMC suspension in water, 2 was dosed p.o. as a diphosphate salt
suspension in 0.5% methylcellulose and 0.5% Tween 80 in water; doses expressed as
free base equivalent. [c] Tumor regression after eight days of treatment for mice, nine
days for rat. [d] Exposure after dosing for three days once daily in separate studies.
(>90%) and sustained inhibition of Gli1 mRNA over 24 h was
toma at a frequency of 10–15%.[23] Additional heterozygous
deletion of the tumor suppressor Hypermethylated in cancer
(Hic), a frequent target of epigenetic gene silencing in medul-
loblastoma, was found to increase the incidence of these
tumors fourfold when compared with Ptch+/ꢀ-only mutants.[24]
We used medulloblastoma tumors developed spontaneously in
Ptch+/ꢀ Hicꢀ/ꢀ mice and transferred them subcutaneously to
the flank of nude mice. Treatment with Smo antagonists has
been shown to result in regression of medulloblastoma in
these mice.[25] The mice were treated orally with 2 or 12b for
eight days. After this time the vehicle group had to be sacri-
ficed because of excessive tumor size (data not shown for ve-
hicle group). Similarly, the two compounds were assessed
using the same Ptch+/ꢀ Hicꢀ/ꢀ mouse medulloblastoma tumors
but implanted subcutaneously into nude rats. In this case,
tumor regression was evaluated after nine days of dosing: the
time at which the vehicle group had to be sacrificed because
of excessive tumor growth. To develop the PK/efficacy correla-
tion, separate studies in Ptch+/ꢀ Hicꢀ/ꢀ medulloblastoma-bear-
ing mice and rats were required with a shorter duration of
compound treatment so that sizable tumor remained for analy-
sis of compound exposure. Tumor and plasma samples were
collected after different time points after the third dosing to
calculate compound exposure described as area under the
curves (AUC0–24h). As summarized in Table 6, 12b requires
a ~2-fold higher dose than 2 to achieve similar tumor regres-
sion in both rodent models. However, 12b achieved similar ef-
observed (Figure 2).
In summary, we have discovered potent Smo inhibitors
based on 1-piperazino-4-benzylpyridazines with improved
aqueous solubility and decreased activity toward the hERG
channel, resulting in compound 12b. Compound 12b retains
activity against a Smo mutant (D473H) cell line identified in
a medulloblastoma patient who had relapsed after an initial re-
sponse to vismodegib. The compound shows efficacy in subcu-
Figure 2. Inhibition of Gli mRNA expression upon treatment with 12b.
Tumors were harvested 0, 1, 4, 8, and 24 h after dosing 40 mgkgꢀ1 12b p.o.
once daily for three days. Gli mRNA levels were analyzed by real-time PCR
and normalized to b-actin expression. Data are shown as percent inhibition
relative to vehicle-treated control tumors.
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1261 – 1265 1264

CHEMMEDCHEM
COMMUNICATIONS
www.chemmedchem.org
taneous Ptch+/ꢀ Hicꢀ/ꢀ medulloblastoma models in mice and
rats, and an analysis of its PK/efficacy relationship demon-
strates its high intrinsic potency. This compound is now in clin-
ical development, and its clinical PK, efficacy, and safety are
currently under evaluation.
[12] For a review on Smo inhibitors in clinical trials, see: T. L. Lin, W. Matsui,
OncoTargets Ther. 2012, 5, 47–58.
[13] FDA approval for vismodegib: available at http://www.cancer.gov/
cancertopics/druginfo/fda-vismodegib [last accessed on June 11, 2013].
[14] K. D. Robarge, S. A. Brunton, G. M. Castanedo, Y. Cui, M. S. Dina, R. Gold-
smith, S. E. Gould, O. Guichert, J. L. Gunzner, J. Halladay, W. Jia, C. Kho-
jasteh, M. F. Koehler, K. Kotkow, H. La, R. L. La Londe, K. Lau, L. Lee, D.
Marshall, J. C. Marsters, L. J. Murray, C. Qian, L. L. Rubin, L. Salphati, M. S.
Stanley, J. H. A. Stibbard, D. P. Sutherlin, S. Ubhayaker, S. Wang, S. Wong,
M. Xie, Bioorg. Med. Chem. Lett. 2009, 19, 5576–5581.
Experimental Section
Synthetic protocols for all compounds, analytical data, and proce-
dures and methods for in vitro and in vivo assays are available in
the Supporting Information. All in vivo research was reviewed and
approved by the Novartis Institute of Biomedical Research Institu-
tional Animal Care and Use Committee (IACUC) in accordance with
all local, state, and federal regulations.
[15] S. Pan, X. Wu, J. Jiang, W. Gao, Y. Wan, D. Cheng, D. Han, J. Liu, N. P. En-
glund, Y. Wang, S. Peukert, K. Miller-Moslin, J. Yuan, R. Guo, M. Matsu-
moto, A. Vattay, Y. Jiang, J. Tsao, F. Sun, A.-M. C. Pferdekamper, S. Dodd,
T. Tuntland, W. Maniara, J. F. Kelleher III, Y. Yao, M. Warmuth, J. Williams,
M. Dorsch, ACS Med. Chem. Lett. 2010, 1, 130–134.
[16] R. L. Yauch, G. J. P. Dijkgraaf, B. Alicke, T. Januario, C. P. Ahn, T. Holcomb,
K. Pujara, J. Stinson, C. A. Callahan, T. Tang, J. Bazan, Z. Kan, S. Seshagiri,
C. L. Hann, S. E. Gould, J. L. Low, C. M. Rudin, F. J. de Sauvage, Science
2009, 326, 572–574.
[17] A. Sekulic, M. R. Migden, A. E. Oro, L. Dirix, K. D. Lewis, J. D. Hainsworth,
J. A. Solomon, S. Yoo, S. T. Arron, P. A. Friedlander, E. Marmur, C. M.
Rudin, A. L. S. Chang, J. A. Low, H. M. Maceky, R. L. Yauch, R. A. Graham,
J. C. Reddy, A. Hauschild, N. Engl. J. Med. 2012, 366, 2171–2179.
[18] K. Miller-Moslin, S. Peukert, R. K. Jain, M. A. McEwan, R. Karki, L. Llamas,
N. Yusuff, F. He, Y. Li, Y. Sun, M. Dai, L. Perez, W. Michael, T. Sheng, H.
Lei, R. Zhang, J. Williams, A. Bourret, A. Ramamurthy, J. Yuan, R. Guo, M.
Matsumoto, A. Vattay, W. Maniara, A. Amaral, M. Dorsch, J. F. Kelleher III,
J. Med. Chem. 2009, 52, 3954–3968.
Acknowledgements
Authors gratefully acknowledge Dr. Xu Wu and Dr. Shifeng Pan
(both Genomics Institute of the Novartis Foundation, La Jolla,
California) as well as Dr. Tim Ramsey (NIBR, Cambridge), Dr.
Yung-mae Yao, and Dr. Christoph Lengauer for many stimulating
discussions throughout the program.
[19] For a related reaction with pyridazines, see: D. S. Chekmarev, A. E. Ste-
panov, A. N. Kasatkin, Tetrahedron Lett. 2005, 46, 1303–1305.
[20] For a related reaction with pyridazines using copper catalysis, see: D.
Peters, G. M. Olsen, E. O. Nielsen, T. D. Jorgensen, D. B. Timmermann
(Neurosearch A/S), WO 2005074940, 2005.
[21] For a positive correlation between polar surface area and aqueous solu-
bility, see: J. R. Votano, M. Parham, L. H. Hall, L. B. Kier, Mol. Diversity
2004, 379–391.
[22] Smo antagonist LY-2940680 has been reported to inhibit its activity in
C3H10T1/2 cells with IC50 =400 nm: M. H. Bender, P. A. Hipskind, A. R.
Capen, M. Cockman, K. M. Credille, H. Gao, J. A. Bastian, J. M. Clay, K. L.
Lobb, D. J. Sall, M. L. Thompson, T. Wilson, G. N. Wishart, B. K. R. Patel,
102nd Annual Meeting, American Association for Cancer Research, April
2–6, 2011, Orlando, FL (USA).
[23] L. V. Goodrich, l. Milenkovic, K. M. Higgins, M. P. Scott, Science 1997, 277,
1109–1113.
[24] K. J. Briggs, I. M. Corcoran-Schwartz, W. Zhang, T. Harcke, W. L. Dever-
eux, S. B. Baylin, C. G. Eberhart, D. N. Watkins, Genes Dev. 2008, 22, 770–
785.
[25] S. Buonamici, J. Williams, M. Morrisey, A. Wang, R. Guo, A. Vattay, K.
Hsiao, J. Yuan, J. Green, B. Ospina, Q. Yu, L. Ostrom, P. Fordjour, D. L. An-
derson, J. E. Monahan, J. F. Kelleher, S. Peukert, S. Pan, X. Wu, S.-M.
Maira, C. Garcia-Echeverria, K. J. Briggs, D. N. Watkins, YM. Yao, C. Lenga-
uer, M. Warmuth, W. R. Sellers, M. Dorsch, Sci. Transl. Med. 2010, 2,
51ra70.
Keywords: antitumor agents · hedgehog signaling · medicinal
chemistry · pyridazines · smoothened inhibitors
[1] A. P. McMahon, P. W. Ingham, C. J. Tabin, Curr. Top. Dev. Biol. 2003, 53,
1–114.
[2] P. W. Ingham, A. P. McMahon, Genes Dev. 2001, 15, 3059–3087.
[3] M. Murone, A. Rosenthal, F. J. de Sauvage, Curr. Biol. 1999, 9, 76–84.
[4] L. L. Rubin, F. J. de Sauvage, Nat. Rev. Drug Discovery 2006, 5, 1026–
1033.
[5] M. P. di Magliano, M. Hebrok, Nat. Rev. Cancer 2003, 3, 903–911.
[6] J.-W. Theunissen, F. J. de Sauvage, Cancer Res. 2009, 69, 6007–6010.
[7] R. Teperino, S. Amann, M. Bayer, S. L. McGee, A. Loipetzberger, T.
Connor, C. Jaeger, B. Kammerer, L. Winter, G. Wiche, K. Dalgaard, M. Sel-
varaj, M. Gaster, R. S. Lee-Young, M. A. Febbraio, C. Knauf, P. D. Cani, F.
Aberger, J. M. Penninger, J. A. Pospisilik, H. Esterbauer, Cell 2012, 151,
414–426.
[8] D. D. Von Hoff, P. M. LoRusso, C. M. Rudin, J. C. Reddy, R. L. Yauch, R.
Tibes, G. J. Weiss, M. J. Borad, C. L. Hann, J. R. Brahmer, H. M. Howard,
B. L. Lum, W. C. Darbonne, J. C. Marsters, Jr., F. J. de Sauvage, J. A. Low,
N. Engl. J. Med. 2009, 361, 1164–1172.
[9] C. M. Rudin, C. L. Hann, J. Laterra, R. L. Yauch, C. A. Christopher, L. Fu, T.
Holcomb, J. Stinson, S. E. Gould, B. Colman, P. M. LoRusso, D. D. Von H-
off, F. J. de Sauvage, J. A. Low, N. Engl. J. Med. 2009, 361, 1173–1178.
[10] J. R. Ahnert, J. Baselga, H. A. Tawbi, Y. Shou, C. Granvil, J. Dey, M. M.
Mita, A. L. Thomas, D. D. Amakye, A. C. Mita, J. Clin. Oncol. 2010, 28,
2500.
Received: May 15, 2013
[11] For a chemistry-centric review on Smo antagonists, see: S. Peukert, K.
Miller-Moslin, ChemMedChem 2010, 5, 500–512.
Published online on July 2, 2013
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemMedChem 2013, 8, 1261 – 1265 1265