Semisynthetic cyclopamine analogues as potent and orally bioavailable hedgehog pathway antagonists

Article abstract of DOI:10.1021/jm8008508

Herein is reported the synthesis of a novel class of hedgehog antagonists derived from cyclopamine. The acid sensitive D-ring of cyclopamine was homologated utilizing a sequence of chemoselective cyclopropanation and stereoselective acid-catalyzed rearran

Full text of DOI:10.1021/jm8008508

6646
J. Med. Chem. 2008, 51, 6646–6649
Semisynthetic Cyclopamine Analogues as
Potent and Orally Bioavailable Hedgehog
Pathway Antagonists
Martin R. Tremblay,* Marta Nevalainen, Somarajan J. Nair,
James R. Porter, Alfredo C. Castro, Mark L. Behnke,
Lin-Chen Yu, Margit Hagel,† Kerry White, Kerrie Faia,
Louis Grenier, Matthew J. Campbell, Jill Cushing,
Caroline N. Woodward,‡ Jennifer Hoyt, Michael A. Foley,§
Margaret A. Read, Jens R. Sydor, Jeffrey K. Tong,
Vito J. Palombella, Karen McGovern, and Julian Adams
Infinity Pharmaceuticals, Inc., 780 Memorial DriVe,
Cambridge, Massachusetts 02139
ReceiVed July 10, 2008
Figure 1. Structures of cyclopamine (1), veratramine (2), and 3.
activity in several xenograft models of pancreatic,9 medullo-
blastoma,16 prostate,10 small cell lung,11 and digestive tract7
cancers. Despite the attractive pharmacological profile of
cyclopamine, its use as a systemic treatment may be limited by
its poor aqueous solubility17 (∼5 µg/mL) and stability in acid.
Indeed, cyclopamine readily converts to veratramine (2) as a
result of an acid-catalyzed opening of the spirotetrahydrofuran
E ring followed by rapid aromatization of the D ring.18
Veratramine (2), although structurally related to cyclopamine,
does not act as a Hh antagonist but has been shown to interact
with several other receptors19,20 and cause hemolysis.21 Hence,
derivatives of cyclopamine that do not have these liabilities are
necessary in order to assess the full therapeutic potential of this
natural product. Taipale and co-workers22 reported potent
derivatives of cyclopamine (e.g. 3) having a hydrophobic moiety
attached to the F-ring nitrogen and a 3-ketone instead of the
3-hydroxy group on the A-ring. Additionally, the 4-en-3-one
cyclopamine (10, Scheme 3) was reported to be an orally active
teratogen,23 which mechanistically correlates with its antago-
nistic activity on the hedgehog pathway. These analogues and
others reported24,25 maintain the natural cyclopamine skeleton
and hence are expected to be acid labile. Herein, we report the
chemical synthesis and biological activity of novel skeleton-
modified cyclopamine derivatives26 with improved water solu-
bility and chemical stability.
Our strategy to improve the acid stability of cyclopamine was
to alter the influence of the D-ring allylic ether on the hydrolysis
of the spirotetrahydrofuran E-ring, with minimal change to the
D-ring geometry. It was hypothesized that the oxygen of the
allylic ether could direct the addition of a zinc carbenoid from
the ꢀ-face of the steroid to chemo- and stereoselectively
cyclopropanate the D-ring double bond.
Cyclopamine was extracted and isolated from V. californicum
using a slightly modified procedure originally described by
Keeler14 and more recently by Oatis.27 Fmoc protected cyclo-
pamine was found to be a good substrate for various cyclopro-
panating procedures, such as Furukawa (Et2Zn, CH2I2),28
Denmark (Et2Zn, ClCH2I),29 and Shi (Et2Zn, TFA or TCA,
CH2I2)30 protocols. For instance, N-Fmoc cyclopamine 4
converts to the D-ring cyclopropyl derivative 5 under Furukawa
conditions effectively (55-65% yield). Deprotection of the
Fmoc group of 5 gave cyclopropylcyclopamine 6 (Scheme 1).
The structure of 6 was confirmed by single-crystal X-ray
diffraction analysis, which definitively established that the
Abstract: Herein is reported the synthesis of a novel class of hedgehog
antagonists derived from cyclopamine. The acid sensitive D-ring of
cyclopamine was homologated utilizing a sequence of chemoselective
cyclopropanation and stereoselective acid-catalyzed rearrangement.
Further modification of the A/B-ring homoallylic alcohol to the
conjugated ketone led to the discovery of new cyclopamine analogues
with improved pharmaceutical properties and in vitro potency (EC50)
ranging from 10 to 1000 nM.
The hedgehog (Hha) signaling pathway is important for tissue
growth and differentiation and plays a pivotal role in embryo-
genesis and tissue homeostasis.1 During development, activation
of the Hh-signal transduction pathway is initiated with the
binding of Hh ligand to the cellular membrane receptor patched
(Ptc), which relieves the Ptc-mediated inhibition of the seven-
transmembrane protein smoothened (Smo). Activated Smo
transduces the signal to the nucleus to regulate gene expression.
The Gli transcription factors, which regulate numerous gene
products involved in tissue growth and differentiation, are the
nuclear executors of the Hh signaling pathway. In adulthood,
the Hh signaling pathway is silent in a great majority of cells.
However, there have been an increasing number of reports over
the past decade documenting the implication of the Hh pathway
in human diseases, such as cancer.2,3 Indeed, aberrant Hh
signaling has been described in numerous cancers such as basal
cell carcinoma,4,5 breast,6 esophagus,7 gastric,7 medulloblas-
toma,8 pancreatic adenocarcinoma,9 prostate,10 and small cell
lung.11 For these reasons, Hh pathway antagonists have been
sought after as potential new treatments for cancer.12,13
Cyclopamine (1, Figure 1), a natural product isolated from
Veratrum californicum,14 has been a tremendously valuable
pharmacological tool to validate the Hh pathway as a promising
target for drug intervention in cancer. Cyclopamine was shown
to be a potent antagonist of the Hh pathway, directly acting on
the protein Smo15 and has since been shown to have antitumor
* To whom correspondence should be addressed. Phone: 617-453-1268.
Fax: 617-682-1418. E-mail: Martin.Tremblay@infi.com.
†
Current address: Avila Therapeutics, Inc., 100 Beaver Street, Waltham,
MA 02453.
‡
Current address: Epix Pharmaceuticals, Inc., 4 Maguire Road, Lex-
ington, MA 02421.
§
Current address: Broad Institute, 320 Charles Street, Cambridge, MA
02141.
a Abbreviations: Hh, hedgehog; Ptc, patched; Smo, smoothened; Fmoc,
fluorenymethoxycarbonyl; SAR, structure-activity relationship; LC, liquid
chromatography; MS, mass spectrometry; Vd, volume of distribution.
10.1021/jm8008508 CCC: $40.75
2008 American Chemical Society
Published on Web 10/09/2008

Letters
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 21 6647
Scheme 1a
Table 1. Cellular Hh Pathway Inhibition of Cyclopamine (1) and
D-Homocyclopamine Analogues
compd
R for analogues of 9
EC50 µM (N)a
1
6
8
9
14
15
16
17
18
19
20
21
22
0.17 ( 0.07 (3)
>2.0 (3)
>2.5 (3)
H
CH3
Ac
0.20 ( 0.08 (9)
0.4 ( 0.1 (3)
0.12 ( 0.02 (3)
>2.5 (3)
0.4 ( 0.2 (3)
>1.0 (3)
>2.0 (3)
0.01 ( 0.002 (3)
0.02 ( 0.01 (3)
0.8 ( 0.1 (3)
CH2CH2Cl
CH2CH2OCH2CH2OCH3
CH2CH2OCH2CH2OH
CH2Ph
CH2CH2NHCO(CH2)5NHCOCH2CH2Ph
CH2CH2NHCOCH2CH2Ph
OH
a Reagents and conditions: (a) Fmoc-OSu, CH2Cl2, 25 °C (80%); (b)
Et2Zn, CH2I2, CH2Cl2, 0-25 °C (55%); (c) diethylamine, CH2Cl2, 25 °C
(90%).
a The number of determinations is shown in parentheses.
Scheme 2. Acid Decomposition of 5 and 6 and Proposed
Mechanisma
groups. Such atypical rearrangements have been reported in the
total synthesis of a few sesquiterpenes.32-34
The ability of D-homocyclopamine 8 to inhibit the Hh
pathway was measured by its effect on oxysterol-induced
differentiation of murine progenitor C3H10T1/2 cells into
osteoblasts in culture. Osteoblast differentiation can be moni-
tored by production of alkaline phosphatase, which was used
as the read-out for the assay.35 Unfortunately, D-homocyclo-
pamine 8 was found to be weaker than cyclopamine in this Hh
dependent assay (Table 1). Modifications previously reported22,23
to improve the biological activity of cyclopamine were incor-
porated onto the new D-homocyclopamine scaffold. For
instance, Oppenaeur oxidation of 8 yielded the enone 9, which
is equipotent to cyclopamine (Table 1). To enable further
optimization of 9, a more robust synthetic route was designed
that introduced the enone prior to cyclopropanation and ring
expansion (Scheme 3). This sequence took advantage of the
relative inertness of the electron-poor enone toward
iodoalkylzinc carbenoids and provided a better substrate for
selective cyclopropanation. Oppenauer oxidation of cyclopamine
gave 4-en-3-one cyclopamine 10,36 which was N-protected with
an Fmoc group to give 11. Subsequent cyclopropanation of the
D-ring olefin of 11 was performed using an excess of bis-
(iodomethyl)zinc prepared according to Denmark’s procedure.29
The crude intermediate 12 was treated with BF3-OEt2 to form
the desired ring-expanded product 13. Deprotection of 13
followed by silica gel chromatography and crystallization gave
the desired 9 in 25-30% overall yield from cyclopamine. A
single-crystal X-ray diffraction analysis confirmed the structure
of 9 (Supporting Information).
With ready access to 9, various N-substituted analogues were
prepared via acylation, reductive amination, and direct alkyla-
tion. In addition to the N-alkyl derivatives, hydroxylamine 22
was prepared by benzoyl peroxide oxidation followed by
hydrolysis of the benzoate (Scheme 3). The ability of these new
analogues (9 and 14-22) to inhibit the Hh pathway was
determined in C3H10T1/2 cells (Table 1).
The structure-activity relationship around enone 9 and
cyclopamine was found to closely track.37 Preservation of the
basicity of the F-ring nitrogen has been thought to be a key
element in determining binding to cyclopamine target. However,
the N-acetamide derivative 15 displayed similar potency com-
pared with the parent molecule 9. Relatively bulky alkyl groups
(e.g., CH2CH2Cl, 16; Bn, 19) are detrimental to biological
activity, whereas elongated appendages, such as the glycolate
analogue 17, have potency similar to that of cyclopamine and
9. Interestingly, the des-methyl analogue of 17, compound 18,
has significantly reduced biological activity. More importantly,
a Reagents and conditions: (a) BF3-OEt2, CH2Cl2, 0 °C (70%).
stereoselective incorporation of cyclopropyl occurred from the
ꢀ-face of the steroid (Supporting Information).
The acid stability of cyclopropylcyclopamine derivatives 5
and 6 was studied. Interestingly, treatment of these derivatives
with various Bronsted and Lewis acids caused a rearrangement
forming distinct isomers, which were stable to acids. The newly
formed isomers derived from 5 and 6 were isolated and
characterized as the ring expanded products Fmoc protected
D-homocyclopamine (7) and D-homocyclopamine (8), respec-
tively. This novel D-homocyclopamine skeleton was subse-
quently confirmed by single-crystal X-ray diffraction analysis
of a further modified analog (vide infra). It is noteworthy that
the C17 stereocenter is conserved in the D-homocyclopamine
derivatives. The acid-catalyzed ring expansion presumably
occurs through the formation of a stabilized cyclopropylcarbinyl
cation, subsequent rearrangement, ring opening of the cyclo-
propyl moiety, and finally re-formation of the spirotetrahydro-
furan (Scheme 2).31 We speculate that the formation of the C17
epimer upon reclosure of the spirotetrahydrofuran is sterically
disfavored because of the C21 methyl and the C18 methyl

6648 Journal of Medicinal Chemistry, 2008, Vol. 51, No. 21
Letters
Scheme 3a
a Reagents and conditions: (a) Al(O-i-Pr)3, 2-butanone, 75 °C (85%); (b) Fmoc-Cl, NaHCO3, THF, 25 °C (88%); (c) Et2Zn, CH2I2, CH2Cl2, 0-25 °C; (d)
BF3-OEt2, CH2Cl2, 0 °C (50%, two steps); (e) piperidine, DMF, 25 °C (75%). (f) See Table 1 for R groups and Supporting Information for details.
20, which has the same hydrophobic moiety on the F-ring as
analogue 3, is 20-fold more potent than its congener. A truncated
version of this side chain was installed on 9 to provide analogue
21 and found to provide 10-fold increase in potency. Finally,
hydroxylamine 22 displayed biological activity, albeit with
4-fold decrease in potency compared to enone 9. In summary,
D-homoanalogue 9 possesses equivalent biological activity in
vitro to cyclopamine and its SAR at the F-ring nitrogen
correlates well with what has been reported for cy-
clopamine.
technical assistance that facilitated this work. The authors
also thank Dr. Richard J. Staples for crystallography data of
6 and 9.
Supporting Information Available: Detailed experimental
procedures and full characterization of 4-22, detailed protocols
for biological tests in vitro and pharmacokinetic studies, and ORTEP
representations of 6 and 9. This material is available free of charge
via the Internet at http://pubs.acs.org.
References
The pharmaceutical properties of the free base of 9 and some
of its analogues were next evaluated. Compound 9 was found
to have much greater aqueous solubility than cyclopamine at
pH 7.4 (>20-fold), whereas the more lipophilic analogues 20
and 21 (albeit more potent) were less soluble. In addition,
stability of the newly formed D-homocyclopamine analogue 9
in simulated gastric fluid was found to be greatly enhanced in
comparison to cyclopamine (98% vs 60% remaining after 60
min incubation, respectively). Encouraged by these data, phar-
macokinetic properties of analogue 9 were determined. To this
end, the hydrochloride of 9 was dissolved in sterile water for
injection containing 30% (w/w) of 2-hydropropyl-ꢀ-cylodextrin
and administered to CD-1 mice intravenously and orally. Plasma
was collected at selected time points, and samples were analyzed
by LC-MS/MS after protein precipitation. Compound 9 shows
very good exposure (80% oral bioavailability) after oral
administration in mice, is cleared from plasma with an elimina-
tion half-life of 3.2 h, and has a large Vd of about 18 L/kg.
(1) Ruiz i Altaba, A.; Sanchez, M. P.; Dahmane, N. Gli and Hedgehog in
Cancer: Tumours, Embryos and Stem Cells. Nat. ReV. Cancer 2002,
2, 361–372.
(2) di Magliano, M. P.; Hebrok, M. Hedgehog Signalling in Cancer
Formation and Maintenance. Nat. ReV. Cancer 2003, 3, 903–911.
(3) Beachy, P. A.; Karhadkar, S. S.; Berman, D. M. Tissue Repair and
Stem Cell Renewal in Carcinogenesis. Nature 2004, 432, 324–331.
(4) Dahmane, N.; Lee, J.; Robins, P.; Heller, P.; Ruiz i Altaba, A.
Activation of the Transcription Factor Gli1 and the Sonic Hedgehog
Signalling Pathway in Skin Tumours. Nature 1997, 389, 876–881.
(5) Hutchin, M. E.; Kariapper, M. S. T.; Gratchtchouk, M.; Wang, A.;
Wei, L.; Cummings, D.; Liu, J.; Michael, L. R.; Glick, A.; Dlugosz,
A. A. Sustained Hedgehog Signaling Is Required for Basal Cell
Carcinoma Proliferation and Survival: Conditional Skin Tumorigenesis
Recapitulates the Hair Growth Cycle. Genes DeV. 2004, 19, 214–
224.
(6) Kubo, M.; Nakamura, M.; Tasaki, A.; Yamanaka, N.; Nakashima, H.;
Nomura, M.; Kuroki, S.; Katano, M. Hedgehog Signaling Pathway Is
a New Therapeutic Target for Patients with Breast Cancer. Cancer
Res. 2004, 64, 6071–6074.
(7) Berman, D. M.; Karhadkar, S. S.; Maitra, A.; Montes de Oca, R.;
Gerstenblith, M. R.; Briggs, K.; Parker, A. R.; Shimada, Y.; Eshleman,
J. R.; Watkins, D. N.; Beachy, P. A. Widespread Requirement for
Hedgehog Ligand Stimulation in Growth of Digestive Tract Tumors.
Nature 2003, 425, 846–851.
(8) Goodrich, L. V.; Scott, M. P. Hedgehog and Patched in Neural
Development and Disease. Neuron 1998, 21, 1243–1257.
(9) Thayer, S. P.; Pasca di Magliano, M.; Heiser, P. W.; Nielsen, C. M.;
Roberts, D. J.; Lauwers, G. Y.; Qi, Y. P.; Gysin, S.; Fernandez-del
Castillo, C.; Yajnik, V.; Antoniu, B.; McMahon, M.; Warshaw, A. L.;
Hebrok, M. Hedgehog Is an Early and Late Mediator of Pancreatic
Cancer Tumorigenesis. Nature 2003, 425, 851–856.
(10) Karhadkar, S. S.; Bova, G. S.; Abdallah, N.; Dhara, S.; Gardner, D.;
Maitra, A.; Isaacs, J. T.; Berman, D. M.; Beachy, P. A. Hedgehog
Signalling in Prostate Regeneration, Neoplasia and Metastasis. Nature
2004, 431, 707–12.
In conclusion, synthetic modifications of cyclopamine resulted
in the identification of a novel D-homocyclopamine scaffold
that retains biological activity on the Hh pathway. Although
various analogues were synthesized, 9 (also referred to as IPI-
269609) stood out as having the most desirable pharmaceutical
properties and pharmacokinetic profile. Compound 9 has shown
efficacy in several xenograft models.38,39 The full potential for
the development of systemic Hh pathway antagonists related
to this promising new class of compounds is currently being
evaluated.
(11) Watkins, D. N.; Berman, D. M.; Burkholder, S. G.; Wang, B.; Beachy,
P. A.; Baylin, S. B. Hedgehog Signalling within Airway Epithelial
Progenitors and in Small-Cell Lung Cancer. Nature 2003, 422, 313–
317.
Acknowledgment. The authors are grateful to all past and
current members of the hedgehog team at Infinity Pharma-
ceuticals, Inc. for preliminary results, scientific guidance, and

Letters
Journal of Medicinal Chemistry, 2008, Vol. 51, No. 21 6649
(12) Rubin, L. L.; de Sauvage, F. J. Target the Hedgehog Pathway in
Cancer. Nat. ReV. Cancer 2006, 5, 1026–1033.
Cyclopamine Prodrugs for Advanced Prostate Cancer. Bioorg. Med.
Chem. 2008, 16, 2764–2768.
(26) Adams, J.; Castro, A. C.; Foley, M. A.; Nair, S. N. J.; Nevalainen,
M.; Cyclopamine Analogs and Methods of Use Thereof. US 7,230,004
B2, June 12, 2007.
(27) Oatis, J. E.; Brunsfeld, P.; Rushing, J. W.; Moeller, P. D.; Bearden,
D. W. Isolation, Purification, and Full NMR Assignments of Cyclo-
pamine from Veratrum californicum. Chem. Cent. J. 2008, 2, 12.
(28) Furukaya, J.; Kawabata, N.; Nishimura, J. A Novel Route to
Cyclopropanes from Olefins. Tetrahedron Lett. 1966, 7, 3353–3354.
(29) Denmark, S. E.; Edwards, J. P. A Comparison of (Chloromethyl)-
and (Iodomethyl)zinc Cyclopropanation Reagents. J. Org. Chem. 1991,
56, 6974–6981.
(30) Yang, Z.; Lorenz, J. C.; Shi, Y. Exploring New Reactive Species for
Cyclopropanation. Tetrahedron Lett. 1998, 39, 8621–8624.
(31) Wong, H. N. C.; Hon, M.-Y.; Tse, C.-W.; Yip, Y.-C.; Tanko, J.;
Hudlicky, T. Use of Cyclopropanes and Their Derivatives in Organic
Synthesis. Chem. ReV. 1989, 89, 165–198.
(32) DeBernadi, M.; Vidari, G.; Vita-Finzi, P.; Fiasson, K. G. Biogenesis-
like Conversion of Marasmane to Lactarane and seco-Lactarane
Skeleton. Tetrahedron Lett. 1982, 23, 4623–4624.
(33) Paquette, L. A.; Ham, W. H. Total Synthesis of the Marine Sesquit-
erpenes Dactylol and Africanol. De Novo Construction of a Cyclooc-
tanoid Natural Product from Cycloheptane Precursors. J. Am. Chem.
Soc. 1987, 109, 3025–3036.
(34) Thompson, S. K.; Heathcock, C. H. Total Synthesis of Some
Marasmane and Lactarane Sesquiterpenes. J. Org. Chem. 1992, 57,
5979–5989.
(13) Hoff, D. D. V.; Rudin, C. M.; LoRusso, P. M.; Borad, M. J.; Korn,
R. L.; Efficacy Data of GDC-0449, a Systemic Hedgehog Pathway
Antagonist, in a First-in-Human, First-in-Class Phase I Study with
Locally Advanced, Multifocal or Metastatic Basal Cell Carcinoma
Patients. Presented at the AACR Annual Meeting, San Diego, CA,
2008.
(14) Keeler, R. F. Teratogenic Compounds of Veratrum californicum
(Durand)-IV. First Isolation of Veratramine and Alkaloid Q and a
Reliable Method for Isolation of Cyclopamine. Phytochemistry 1968,
7, 303–306.
(15) Chen, J. K.; Taipale, J.; Cooper, M. K.; Beachy, P. A. Inhibition of
Hedgehog Signaling by Direct Binding of Cyclopamine to Smooth-
ened. Genes DeV. 2002, 16, 2743–2748.
(16) Berman, D. M.; Karhadkar, S. S.; Hallahan, A. R.; Pritchard, J. I.;
Eberhart, C. G.; Watkins, D. N.; Chen, J. K.; Cooper, M. K.; Taipale,
J.; Olson, J. M.; Beachy, P. A. Medulloblastoma growth inhibition
by hedgehog pathway blockade. Science 2002, 297, 1559–1561.
(17) Keeler, R. F.; Baker, D. C. Oral, Osmotic Minipump, and Intramuscular
Administration to Sheep of the Veratrum Alkaloid Cyclopamine. Proc.
Soc. Exp. Biol. Med. 1989, 192, 153–156.
(18) Keeler, R. F. Teratogenic Compounds in Veratrum californicum
(Durand) IX. Structure-Activity Relation. Teratology 1970, 3, 169–
174.
(19) Thron, C. D.; McCann, F. V. Pharmacological Tests of the Mechanism
of the Periodic Rhythm Caused by Veratramine in the Sinoatrial Node
of the Guinea Pig. Gen. Pharmacol. 1998, 32, 81–89.
(20) Nagata, R.; Izumi, K. Veratramine-Induced Behavior Associated with
Serotonergic Hyperfunction in Mice. J. Pharmacol. 1991, 55, 129.
(21) Badria, F. A.; McChesney, J. D.; Halim, A. F.; Zaghloul, A. M.; El
Sayed, K. A. Time Course and Inhibition of Stavaroside K, Veratra-
mine and Cevine-Induced Hemolysis by Other Pregnane Glycosides
and Veratrum Alkaloids. Pharmazie 1995, 50, 421–423.
(22) Taipale, J.; Chen, J. K.; Cooper, M. K.; Wang, B.; Mann, R. K.;
Milenkovic, L.; Scotts, M. P.; Beachy, P. A. Effects of Oncogenic
Mutations in Smoothened and Patched Can Be Reversed by Cyclo-
pamine. Nature 2000, 406, 1005–1009.
(23) Brown, B.; Keeler, R. F. Structure-Activity Relation of Steroid
Teratogens. 1 Jervine Ring System. J. Agric. Food Chem. 1978, 26,
561–563.
(24) Zhang, J.; Garrossian, M.; Gardner, D.; Garrossian, A.; Chang, Y.-
T.; Kim, Y. K.; Chang, C. W. T. Synthesis and Anticancer Activity
Studies of Cyclopamine Derivatives. Bioorg. Med. Chem. Lett. 2008,
18, 1359–1363.
(35) Dwyer, J. R.; Sever, N.; Carlson, M.; Nelson, S. F.; Beachy, P. A.;
Parhami, F. Oxysterols Are Novel Activators of the Hedgehog
Signaling Pathway in Pluripotent Mesenchymal Cells. J. Biol. Chem.
2007, 282, 8959–8968.
(36) Masamune, T.; Sato, N.; Kobayashi, K.; Yamazaki, I.; Mori, Y.
Syntheses and NMR Spectra of 22,27-Imino-17,23-oxidojervane
Derivatives. Tetrahedron 1967, 23, 1591–1612.
(37) Beachy, P. A. Regulators of the Hedgehog Pathway, Compositions
and Use Related Thereto. WO 01/27135 A2, April 19, 2001.
(38) McGovern, K. J.; Pien, C. S.; Wright, J. L. Dosing Regimen for the
Treatment of Cancer. WO 2007/123511 A2, November 1, 2007.
(39) Feldmann, G.; Fendrich, V.; McGovern, K.; Bedja, D.; Bisht, S.;
Alvarez, H.; Koorstra, J.-B. M.; Habbe, N.; Karikari, C.; Mullendore,
M.; Gabrielson, K. L.; Sharma, R.; Matsui, W.; Maitra, A. An Orally
Bioavailable Small-Molecule Inhibitor of Hedgehog Signaling Inhibits
Tumor Initiation and Metastasis in Pancreatic Cancer. Mol. Cancer
Ther. 2008, 7, 2725–2735.
(25) Kumar, S. K.; Roy, I.; Anchoori, R. K.; Fazli, S.; Maitra, A.; Beachy,
P. A.; Khan, S. R. Targeted Inhibition of Hedgehog Signaling by
JM8008508