Synthesis and biological evaluation of 11′ imidazolyl antiprogestins and mesoprogestins

Article abstract of DOI:10.1016/j.steroids.2014.08.017

Antiprogestins with a 4′ para imidazolylphenyl moiety were synthesized and their biochemical interactions with the progesterone and glucocorticoid receptor were investigated. Depending on the substitution pattern at the 17 position partial progesterone re

Full text of DOI:10.1016/j.steroids.2014.08.017

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Contents lists available at ScienceDirect
Steroids
journal homepage: www.elsevier.com/locate/steroids
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Synthesis and biological evaluation of 110 imidazolyl antiprogestins
and mesoprogestins
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a
a
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Klaus Nickisch a, , Walter Elger , Bindu Santhamma , Robert Garfield , Zachary Killeen ,
⇑
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Olga Amelkina c, Birgitt Schneider a, Reinhard Meister d
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a Evestra, Inc., San Antonio, TX, USA
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b St. Joseph’s Hospital and Medical Center, Phoenix, AZ, USA
c Leibnitz Institute for Zoological- and Wildlife Research, IZW, Berlin, Germany
d Beuth University of Applied Science, Berlin, Germany
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a r t i c l e i n f o
a b s t r a c t
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Antiprogestins with a 40 para imidazolylphenyl moiety were synthesized and their biochemical interac-
tions with the progesterone and glucocorticoid receptor were investigated. Depending on the substitu-
tion pattern at the 17 position partial progesterone receptor (PR)-agonistic derivatives like compounds
EC339 and EC336 or pure antagonists like compound EC317 were obtained. EC317 was investigated
in vivo and found to be significantly more potent than RU 486 in cycling and pregnant guinea pigs. For
testing the biological action progesterone receptor modulators (PRM), guinea pigs appears as a specific
model when compare to pregnant human uterus. This model correlates to human conditions such as soft-
ening and widening of the cervix, the elevation of the uterine responsiveness to prostaglandins and oxy-
tocin, and finally to induction of labor. The use of non-pregnant guinea pigs permitted the simultaneous
assessment of PR-agonistic and PR-antagonistic properties and their physiological interactions with uter-
ine and vaginal environment. These can histologically be presumed from the presence of estrogen or pro-
gesterone dominance in the genital tract tissues. The ovarian histology indicated the effects on ovulation.
Corpora lutea in guinea pigs further reflects inhibitory effects of the progesterone-dependent uterine
prostaglandin secretion. PRMs are initially synthesized as analogues of RU 486. They represent a heter-
ogeneous group of compounds with different ratios of PR-agonistic and-antagonistic properties. PR-ago-
nistic properties may be essential for uterine anti-proliferative effects. In various clinical studies these
were also attributed to RU 486 or Ulipristal [1,2]. Adjusted PR-agonistic PRMs (EC312, EC313) [3] may
be more effective in achieving a mitotically resting endometrium and superior uterine tumor inhibition.
For the use in termination of pregnancy, progesterone-inhibitory effects are essentially needed. Even
minor PR-agonistic properties compromise the therapeutic goals. Pure PR-antagonists, as EC317, clearly
exceeded the gold standard RU 486 with respect to labor inducing effects. Mechanistically it is surprising
that both types of compound may be potent inhibitors of ovulation.
Article history:
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Received 23 March 2014
Received in revised form 25 July 2014
Accepted 17 August 2014
Available online xxxx
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Keywords:
Antiprogestins
Postcoital fertility control
Cervix widening
Ó 2014 Published by Elsevier Inc.
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1. Introduction
abortion and Ulipristal for postcoital fertility control and for pre-
operative treatment for uterine fibroids. Regarding the pharmaco-
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The first progesterone receptor antagonist, RU 486 [4] more
than 30 years ago, has initiated an intense research effort and pro-
spective new treatments in areas like fertility control, gynecologi-
cal diseases such as endometriosis, myomas and hormone
dependent cancers. Some of these studies did not provide
expected results. Two antiprogestins have been approved till date
were, RU 486 for the first widely used non-surgical induction of
dynamic heterogeneity of PRMs [5–8], the key reason for the lack
of additional marketed products in the gynecological therapy
might be the lack of appropriate animal models applicable for
the different needs of given indications. These may require
different, better adapted pharmacodynamic profiles. Compounds
that act as pure progesterone antagonists appear ideal for cervical
ripening and labor induction, whereas compounds with a strong
partial PR-agonist activity may lack labor inducing properties.
They may help to safely achieve improved anti-proliferative
effects in patients with endometriosis and uterine tumors
(fibroid/myoma). It is hypothesized that for the existing and
⇑
Corresponding author.
E-mail address: knickisch@evestra.com (K. Nickisch).
http://dx.doi.org/10.1016/j.steroids.2014.08.017
0039-128X/Ó 2014 Published by Elsevier Inc.
Please cite this article in press as: Nickisch K et al. Synthesis and biological evaluation of 110 imidazolyl antiprogestins and mesoprogestins. Steroids
(2014), http://dx.doi.org/10.1016/j.steroids.2014.08.017

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potential new indications, optimized substances could be devel-
oped, that address the shortcomings of the first generation of
PRM-products.
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2. Experimental
2.1. General
The development of Asoprisnil for indications like uterine fib-
roids and endometriosis proved the predictive value of the guinea
pig model. This applies to the successful selection of this mole-
cule and mechanistic aspects. The simultaneous manifestation
of agonistic and antagonistic activity at the same dose level in
target tissues in animals and in the human [5,6] represents an
analogy of SPRMs to SERMs (Specific Estrogen Receptor Modula-
tor). Due to this, the term SPRM (Specific Progestin Receptor
Modulator) has been coined [5] and reserved to this type of
mixed agonist-/antagonist activity at the receptor level of PR.
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Nuclear magnetic resonance spectra were recorded on a Bruker
ARX (300 MHz) spectrometer as deuterochloroform (CDCl3) solu-
tions using tetramethylsilane (TMS) as an internal standard
(d = 0) unless noted otherwise. ‘Flash column’ chromatography
was performed on 32–64 lM silica gel obtained from EM Science,
Gibbstown, New Jersey. Thin-layer chromatography (TLC) analyses
were carried out on silica gel GF (Analtech) glass plates
(2.5 cm ꢀ 10 cm with 250
lM layer and pre-scored). Most chemi-
cals and solvents were analytical grade and used without further
purification. Commercial reagents were purchased from Aldrich
Chemical Company (Milwaukee, WI).
Asoprisnil permitted for
a chronic use, arresting menstrual
bleeding and leading to a dramatic reduction of the size of uterine
fibroids and the associated dysfunctional bleeding. This was
achieved without unopposed estrogenic effects in the endome-
trium [5,9] (Table 1).
Over the years, knowledge about the structure activity relation-
ship (SAR) of antiprogestins has increased considerably [4,10,11].
Two substitution patterns at the 17 position which attracted con-
siderable interest in recent years are the 17,17spiroether group
[12] and the pentafluoro ethyl group [13]. Both lead to compounds
that bind strongly and selectively to the progesterone receptor,
nothing is however reported about potential determinants of par-
tial PR-agonistic activities.
There are only very few reports about antiprogestins with pro-
ven partial PR-agonistic activity in vitro [14]. Other methods
showed apparent discrepancies of data from in vitro and in vivo
studies showing false negative results in vitro for compounds with
clear cut PR-agonistic effects in vivo (unpublished negative
in vitro data from collaborating laboratories, including Asoprisnil).
The first SPRM was Asoprisnil (Fig. 1) for which a strong partial
agonistic activity was proven in the classical animal models for
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2.2. Chemical synthesis
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Compounds 2 and 10 were synthesized following literature pro-
cedures described by Rao et al. in Steroids; 1998; 63: 523–530 and
by Jiang et al. in Bioorg Med Chem 2006; 14:6726–6732.
2.2.1. 3,3-Ethylenedioxy-5a
-hydroxy-11b-[40-iodophenyl]-estr-9-ene-
17-one (3)
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A solution of 1,4-diiodobenzene (13.2 g, 40 mmol) in anhydrous
THF (80 mL) was cooled to ꢁ10 °C as a 2 M solution of isopropyl
magnesium chloride (20 mL, 40 mmol) was added dropwise over
a period of 15 min. After stirring for 20 min, cuprous chloride
(898 mg, 9.07 mmol) was added as a solid and the reaction mixture
was stirred for 30 min. A solution of the epoxide 2 (6 g, 18 mmol)
in 60 mL of THF was added drop wise and stirred for 2 h slowly
warming to 10 °C. The reaction was quenched with saturated aque-
ous ammonium chloride solution (50 mL) and was extracted with
ethyl acetate (3 ꢀ 50 mL). The combined organic layer was washed
further with water and brine, dried over sodium sulfate and evap-
orated in vacuo to afford the crude product. The crude product was
triturated with di-isopropyl ether (120 mL) to precipitate the pure
product which was filtered, washed with ice cold di-isopropyl
ether (30 mL) and dried under vacuum to afford 6.9 g (72%) of 3
as an off white solid.
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progestational activity [7,15].
A mixed profile progesterone
agonists/antagonists have been described for 11 pyridylphenyl
derivatives [3,16] and 11furanylphenyl derivatives [3].
There is however no systematic investigation on substitution
patterns in the molecules that lead to a full PR-antagonistic or a
partial agonistic profile. The available biological and X-ray data
suggest that substitution pattern at the 11 position determines
the degree of agonistic and antagonistic activity. Small substitutes
like methyl or vinyl lead to potent PR-agonistic properties [4]
whereas substituted phenyl derivatives show different degrees of
antagonistic activity. The most widely used moiety is the 40
dimethyl amino function, present in RU 486 and Ulipristal impart
an antagonistic activity whereas the 3 pyridylphenyl derivative
leads to a partial agonistic profile.
For this study the 11 imidazolyl phenyl moiety was selected,
because it is special arrangement of atoms and the pka’s are
somewhat in between the dimethyl amino and pyridyl group and
combined with moieties at the 17 position that were reported to
lead to potent antiprogestins. All molecules were investigated for
antagonistic and partial agonistic activities.
1H NMR (d, CDCl3, 300 MHz): 0.49 (s, 3H), 3.88–4.04 (m, 4H),
4.26 (d, J = 7.1 Hz), 4.39 (s, 1H), 6.98 (d, J = 8.1 Hz, 2H), 7.57 (d,
J = 8.4 Hz, 2H).
13C NMR (d, CDCl3, 75 MHz): 14.36, 22.10, 23.36, 35.05, 35.51,
37.74, 37.78, 37.97, 39.02, 47.33, 47.43, 50.45, 64.08, 64.71,
69.88, 90.87, 108.43, 121.30, 128.62, 132.86, 135.95, 145.97,
219.48.
2.2.2. 3,3-Ethylenedioxy-5a
-hydroxy-11b-[40-(1-imidazolyl)phenyl]-
estr-9-ene-17-one (4)
A mixture of compound 3 (9.7 g, 18 mmol), imidazole (1.4 g,
20 mmol), cuprous iodide (346 mg, 1.8 mmol), N,N-dimethyl gly-
cine (374 mg, 3.6 mmol) and potassium carbonate (5 g, 36 mmol)
in anhydrous DMSO (10 mL) was degassed three times applying
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Table 1
Current uses of PRMs and hypothesis for future developments.
Target indication
Approved
products
Optimized clinical Goal
Pharmacodynamic profile
Induction of labor and cervical
softening
RU 486
Higher efficacy, faster onset of action
Pure antagonist
Postcoital fertility control
Fibroids/endometriosis
Ulipristal
Ulipristal
Efficacy comparable or superior to classical OCs
Resting endometrium. No time restriction for
treatment
Pure PR-antagonist with anti-ovulatory activity
Strong partial agonistic activity at PR(SPRMs/
mesoprogestins)
Breast cancer
None
High PR-mediated specific cytotoxicity
Pure PR-antagonist with high cytotoxicity
Please cite this article in press as: Nickisch K et al. Synthesis and biological evaluation of 110 imidazolyl antiprogestins and mesoprogestins. Steroids
(2014), http://dx.doi.org/10.1016/j.steroids.2014.08.017

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O
H
N
O
N
N
O
O
O
OMe
OMe
O
O
OAc
F
F
F
F
O
O
Asoprisnil
Ulipristal acetate
CDB2914
EC312
EC313
Q7
Fig. 1.
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vacuum and nitrogen and was immersed into a preheated oil bath
at 110 °C. The reaction mixture was heated for 60 h. After cooling
to room temperature, the reaction mixture was diluted with ethyl
acetate (150 mL) and filtered through a Celite pad. The filtrate was
transferred to a separatory funnel and was washed with water,
brine and dried over anhydrous sodium sulfate. The solvent was
removed under vacuum to afford the crude product, which on puri-
fication by chromatography on SiO2 column eluting with 30% ace-
tone in dichloromethane gave 7.6 g (91%) of required product 4 as a
pale yellow solid.
1H NMR (d, CDCl3, 300 MHz): 0.68 (s, 3H), 4.48 (d, J = 6.6 Hz,
1H), 5.79 (s, 1H), 7.18 (s, 1H), 7.23–7.30 (m, 5H), 7.62 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 16.84, 25.13, 25.75, 27.78, 31.11,
33.06, 36.57, 39.33 (d, J = 7.9 Hz), 39.58, 40.59, 50.44, 51.57 (d,
J = 3.6 Hz), 83.94 (t, J = 23 Hz), 118.41, 121.68, 123.31, 128.39,
129.67, 130.15, 134.77, 135.17, 143.64, 145.18, 155.99, 199.17.
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2.2.5. 3,3-Ethylenedioxy-5a,17b-dihydroxy-17-(3,3,3-trifluoro-1-
propynyl)-11b-{40-[10 imidazolyl) phenyl}-estr-9-ene (6)
Freshly prepared lithium diisopropylamide solution made by
the addition of n-BuLi (6.4 mL, 2.5 M, 16 mmol) to diisopropyl-
amine (1.6 g, 16 mmol) in THF (20 mL) at ꢁ78 °C was added to a
solution of 2-bromo-3,3,3-trifluoropropene (2.4 g, 14 mmol) in
THF (15 mL) at ꢁ78 °C. The resulting purple solution was stirred
at this temperature for 20 min. A solution of compound 4 (1.09 g,
2.3 mmol) in THF (10 mL) was introduced into the reaction mix-
ture over a period of 20 min and was stirred for 1 h at ꢁ78 °C
and allowed to warm to r.t. over a period of 16 h. Reaction mixture
was quenched with aqueous ammonium chloride (50 mL) and
extracted with ethyl acetate (3 ꢀ 100 mL). The combined organic
layer was washed further with water and brine, dried over anhy-
drous sodium sulfate and evaporated in vacuo to afford the crude
product. Purification was performed on a silica gel column using
10% acetone in methylene chloride to afford compound 6 (1.55 g,
88%) as a brown amorphous solid.
1H NMR (d, CDCl3, 300 MHz): 0.51 (s, 3H), 3.92–4.04 (m, 4H),
4.37–4.39 (m, 2H), 7.19 (s, 1H), 7.27–7.35 (m, 5H), 7.84 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 14.4, 22.1, 23.4, 35.1, 35.5, 37.7,
37.9, 38, 39.2, 47.4, 47.4, 50.5, 64.1, 64.7, 69.9, 108.4, 121.3,
128.6, 132.9, 136, 146, 219.5.
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2.2.3. 3,3-Ethylenedioxy-5a,17b-dihydroxy-17-(1,1,2,2,2-
pentafluoroethyl)-11b-(4’-(1-imidazolyl) phenyl)-estr-9-ene (5)
Pentafluoroiodoethane (3.9 g, 16 mmol) was condensed into a
solution of compound 4 (1.3 g, 2.7 mmol) in toluene (45 mL) kept
at ꢁ78 °C. A 1.5 M solution of methyl lithium–lithium bromide
complex (8.9 mL, 13.5 mmol) was added dropwise over a period
of 15 min. The resulting reaction mixture was stirred at ꢁ78 °C
for 1 h and allowed to stir at 0 °C for another hour. The reaction
was quenched by the addition of saturated sodium bicarbonate
solution (30 mL). Extracted with ethyl acetate (2 ꢀ 50 mL) and
the combined organic layer were washed once with water, brine
and dried over sodium sulfate. The solvent was removed under
vacuum to obtain the crude product, which on purification by
chromatography on SiO2 column eluting with 10% acetone in
dichloromethane gave 1.28 g (80%) of required product 5 as a pale
yellow solid.
1H NMR (d, CDCl3, 300 MHz): 0.52 (s, 3H), 3.75–4.10 (m, 4H),
4.35–4.50 (m, 2H), 7.16 (s, 1H), 7.27–7.36 (m, 5H), 7.84 (s, 1H).
2.2.6. 11b-(40-(1-Imidazolyl)phenyl)-17b-hydroxy-17-(3,3,3-trifluoro-
1-propynyl)-estra-4,9-diene-3-one (EC335)
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To a solution of compound 6 (800 mg, 1.4 mmol) in methanol
(10 mL) at 0 °C was added 50% sulfuric acid (0.5 mL). After stirring
for 90 min, the reaction mixture was carefully quenched by the
addition of saturated sodium bicarbonate solution. Extracted with
ethyl acetate (2 ꢀ 50 mL) and the combined organic layers were
washed with water, brine and dried over an. sodium sulfate. The
solvent was removed under vacuum to obtain the crude product
which was purified on a silica column eluting with 20% acetone
in methylene chloride to give compound EC335 (600 mg, 84%) as
a light brown amorphous solid.
1H NMR (d, CDCl3, 300 MHz): 0.60 (s, 3H), 3.89–4.04 (m, 4H),
4.37 (s, 2H), 7.18 (s, 1H), 7.27–7.32 (m, 5H), 7.67 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 16.73, 23.31, 24.35, 25.45, 33.38,
35.09, 38.30, 39.37, 39.73, 47.42, 50.37, 51.45, 51.51, 53.39,
64.07, 64.70, 77.20, 108.46, 118.44, 121.37, 128.63, 129.19,
132.27, 134.47, 135.14, 135.49, 147.46.
2.2.4. 11b-(40-(1-Imidazolyl)phenyl)-17b-hydroxy-17-(1,1,2,2,2-
pentafluoroethyl)-estra-4,9-diene-3-one (EC317)
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1H NMR (d, CDCl3, 300 MHz): 0.58 (s, 3H), 4.51 (d, J = 6.5 Hz,
1H), 5.82 (s, 1H), 7.20 (s, 1H), 7.27–7.34 (m, 5H), 7.83 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 13.76, 23.43, 25.84, 27.31, 30.97,
36.57, 38.31, 39.09, 39.20, 39.82, 47.41, 49.99, 73.72 (d,
J = 57 Hz), 90.62 (q, J = 6.6 Hz), 113.63 (d, J = 251 Hz), 118.17,
121.54, 123.52, 128.36, 130.01, 130.38, 135.06, 135.32, 143.46,
144.09, 155.72, 199.11.
A solution of compound 5 (1 g, 1.68 mmol) in methanol (10 mL)
was cooled to 0 °C as 5 N hydrochloric acid (1.6 mL, 8.4 mmol) was
added drop wise. The reaction mixture was stirred for 1 h warming
to room temperature. Quenched by the careful addition of satu-
rated sodium bicarbonate solution and extracted with ethyl ace-
tate (2 ꢀ 25 mL). Combined organic layers were washed with
water, brine and dried over anhydrous sodium sulfate. The solvent
was removed in vacuo to obtain the crude product, which on puri-
fication by chromatography on SiO2 column eluting with 10% ace-
tone in dichloromethane gave 0.8 g (90%) of required compound
EC317 as an off white solid.
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2.2.7. 3,3-Ethylenedioxy-5a,17b-dihydroxy-17-(3,3,3-trifluoroprop-
1(E)-enyl)-11b-{40-[10 imidazolyl) phenyl}-estr-9-ene (7)
A solution of compound 6 (1.8 g, 3.1 mmol) in anhydrous tolu-
ene (30 mL) was cooled to ꢁ78 °C as a 65% solution of Red-Al
Please cite this article in press as: Nickisch K et al. Synthesis and biological evaluation of 110 imidazolyl antiprogestins and mesoprogestins. Steroids
(2014), http://dx.doi.org/10.1016/j.steroids.2014.08.017

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340
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(2.14 mL, 11 mmol) was added drop wise and the reaction mixture
was stirred for 4 h at ꢁ78 °C. Reaction was quenched by the addi-
tion of saturated ammonium chloride. The separated organic layer
was washed with water, brine and dried over anhydrous sodium
sulfate. The solvent was removed in vacuo to afford the crude prod-
uct, which on purification by chromatography on silica column
eluting with 20% acetone in methylene chloride gave compound
7 (1.5 g, 85%) as a brown foam.
2.2.10. 3,3-Ethylenedioxy-5
epoxy-19,24-dinor-17
a
-hydroxy-11b-(40-[iodophenyl)-17,23-
-chola-9,20-diene (11)
a
A solution of 1,4-diiodobenzene (5.14 g, 15.6 mmol) in anhy-
drous THF (50 mL) was cooled to ꢁ10 °C as a 2 M solution of iso-
propyl magnesium chloride (7.8 mL, 15.6 mmol) was added
dropwise over a period of 15 min. After stirring for 20 min, cuprous
chloride (257 mg, 2.6 mmol) was added as a solid and the reaction
mixture was stirred for 30 min. A solution of the epoxide 10 (2 g,
5.2 mmol) in 20 mL of THF was added drop wise and stirred for
2 h slowly warming to 10 °C. Quenched with aqueous ammonium
chloride solution (50 mL) and extracted with ethyl acetate
(2 ꢀ 50 mL). The combined organic layer was washed further with
water and brine, dried over sodium sulfate and evaporated in vacuo
to afford crude product. The crude product was purified on a silica
column eluting with 30% ethyl acetate in hexane to afford 2.81 g
(92%) of 11 as an off white solid.
1H NMR (d, CDCl3, 300 MHz): 0.57 (s, 3H), 3.92–4.03 (m, 4H),
4.30 (d, J = 6.2 Hz, 1H), 4.42 (s, 1H), 5.90–5.98 (m, 1H), 6.52 (dd,
J1 = 15.4 Hz, J2 = 1.8 Hz 1H) 7.16–7.34 (m, 6H), 7.83 (s, 1H).
2.2.8. 11b-(40-(1-imidazolyl)phenyl)-17b-hydroxy-17-(3,3,3-
trifluoroprop-1(E)-enyl)-estra-4,9-diene-3-one (EC339)
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A solution of compound 7 (1 g, 1.5 mmol) in methanol (15 mL)
was cooled to 0 °C as 5 N hydrochloric acid (1.2 mL, 6.22 mmol)
was added drop wise. The reaction mixture was stirred for an hour
warming to room temperature. Quenched by the careful addition
of saturated sodium bicarbonate solution and extracted with ethyl
acetate (2 ꢀ 25 mL). Combined organic layers were washed with
water, brine and dried over anhydrous sodium sulfate. The solvent
was removed in vacuo to obtain the crude product, which on puri-
fication by chromatography on SiO2 column eluting with 10% ace-
tone in dichloromethane gave 1.06 g (67%) of required compound
EC339 as a pale brown solid.
1H NMR (d, CDCl3, 300 MHz): 0.58 (s, 3H), 3.74 (s, 4H), 3.81–3.94
(m, 4H), 4.13 (d, J = 6.2 Hz, 1H), 4.85 (s, 1H), 5.13 (s, 1H), 5.77 (s,
1H), 6.91 (d, J = 8.5 Hz, 2H), 7.58 (d, J = 8.4 Hz, 2H).
13C NMR (d, CDCl3, 75 MHz): 14.99, 23.14, 23.98, 24.08, 31.27,
34.1334.96, 35.01, 38.26, 38.91, 39.35, 39.91, 46.45, 47.38, 48.60,
63.98, 64.63, 69.95, 90.30, 94.70, 107.29, 108.55, 129.38, 133.61,
134.47, 137.11, 137.51, 147.19, 153.77.
-hydroxy-11b-(40-[1-imidazolyl)phenyl)-
-chola-9,20-diene (12)
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366
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368
369
370
371
372
373
374
375
376
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378
379
380
381
382
383
384
2.2.11. 3,3-Ethylenedioxy-5
17,23-epoxy-19,24-dinor-17
mixture of compound 11 (2.7 g, 4.6 mmol), imidazole
a
a
1H NMR (d, CDCl3, 300 MHz): 0.64 (s, 3H), 4.42 (d, J = 6.8 Hz,
1H), 5.80 (s, 1H), 5.98–6.05 (m, 1H), 6.59 (dd, J1 = 15.5 Hz,
J2 = 1.8 Hz 1H) 7.17–7.30 (m, 6H), 7.77 (s, 1H).
A
(531 mg, 4.6 mmol), cuprous iodide (87 mg, 0.5 mmol), N,N-
dimethyl glycine (94 mg, 0.9 mmol) and potassium carbonate
(1.3 g, 9.2 mmol) in anhydrous DMSO (5 mL) was degassed three
times applying vacuum and nitrogen and was immersed into pre-
heated oil bath at 110 °C. The reaction mixture was heated for 60 h.
After cooling to room temperature, the reaction mixture was
diluted with ethyl acetate (100 mL) and filtered through a Celite
pad. The filtrate was transferred to a separatory funnel and was
washed with water, brine and dried over anhydrous sodium sul-
fate. The solvent was removed under vacuum to afford the crude
product, which on purification by chromatography on SiO2 column
eluting with 10% acetone in ethyl acetate gave 2.4 g (98%) of
required product 12 as a pale yellow amorphous solid.
13C NMR (d, CDCl3, 75 MHz): 15.40, 23.81, 25.79, 27.49, 30.95,
36.56, 36.90, 38.83, 39.26, 39.89, 47.30, 50.10, 83.12, 116.12 (q,
J = 33 Hz), 118.13, 121.43, 123.57 (d, J = 294 Hz), 128.31, 129.99,
130.28, 134.98, 135.27, 143.84, 144.20, 155.75, 199.01.
2.2.9. 11b-(40-(1-Imidazolyl)phenyl)-17b-hydroxy-17-(1,1-
difluoroprop-2-enyl)-estra-4,9-diene-3-one (EC340)
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
To a solution of compound 4 (1.9 g, 4 mmol) in pyridine (15 mL)
was added DMAP (98 mg, 0.8 mmol) followed by acetic anhydride
(2.86 g, 28 mmol) and the resulting mixture was heated at 60 °C for
30 h. The solvents were removed under vacuum and the crude was
quickly passed through a short pad of silica and concentrated to
obtain compound 8 (1.82 g, 3.9 mmol), which was dissolved in
THF–ether–pentane (4:1:1, 80 mL) mixture and was cooled to
ꢁ100 °C. 3-Bromo 3,3-difluoro-1-propene (3.12 g, 20 mmol) was
added followed by the dropwise addition of n-BuLi (8 mL, 2.5 M,
20 mmol). The reaction mixture was allowed to stir for 90 min at
ꢁ95 °C and allowed to warm to room temperature over 3 h.
Quenched with ammonium chloride solution (50 mL) and
extracted with ethyl acetate (3 ꢀ 50 mL). The combined organic
layer was concentrated under vacuum and the crude obtained
was dissolved in methanol (20 mL) and treated with 5 N hydro-
chloric acid (1.7 mL) at 0 °C. Reaction was allowed to stir at room
temperature for 2 h and was carefully quenched with saturated
sodium bicarbonate solution (25 mL). Organic materials were
extracted with ethyl acetate (3 ꢀ 30 mL) and the combined organic
layers were dried over sodium sulfate, concentrated under vac-
uum. Purification was effected on a silica gel column using 10%
acetone in methylene chloride to afford EC340 (400 mg, 20%) as
a pale yellow amorphous solid.
1H NMR (d, CDCl3, 300 MHz) 0.54 (s, 3H), 3.74–4.04 (m, 8H),
4.24 (d, J = 6.8 Hz, 1H), 4.83 (s, 1H), 5.10 (s, 1H), 7.19 (s, 1H),
7.27–7.36 (m, 5H), 7.84 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 15.13, 23.22, 24.01, 24.11, 34.22,
35.08, 38.30, 38.9639.36, 40.03, 46.49, 47.42, 48.65, 64.04, 64.69,
64.73, 69.97, 94.73, 107.45, 108.54, 121.21, 128.68, 129.35,
133.62, 134.48, 134.72, 153.75.
2.2.12. 11b-(40-[1-Imidazolyl]phenyl)-17,23-epoxy-19,24-dinor-17
chola-4,9,20-triene-3-one (EC336)
a-
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
A solution of compound 12 (2.29 g, 4.33 mmol) in methanol
(20 mL) was cooled to 0 °C as 5 N hydrochloric acid (1.7 mL,
8.7 mmol) was added drop wise. The reaction mixture was stirred
for 3 h warming to room temperature. Quenched by the careful
addition of saturated sodium bicarbonate solution (30 mL) and
extracted with ethyl acetate (2 ꢀ 50 mL). Combined organic layers
were washed with water, brine and dried over anhydrous sodium
sulfate. The solvent was removed in vacuo to obtain the crude
product, which on purification by chromatography on SiO2 column
eluting with 10% acetone in dichloromethane gave 1.63 g (81%) of
required compound EC336 as a white solid.
1H NMR (d, CDCl3, 300 MHz): 0.62 (s, 3H), 4.44–4.46 (m, 1H),
5.56 (5.80 (s, 1H), 5.98–6.05 (m, 1H), 6.59 (dd, J1 = 15.5 Hz,
J2 = 1.8 Hz 1H) 7.17–7.30 (m, 6H), 7.77 (s, 1H).
1H NMR (d, CDCl3, 300 MHz) 0.60 (s, 3H), 4.35 (d, J = 7 Hz, 1H),
4.86 (s, 1H), 5.15 (s, 1H), 5.78 (s, 1H), 7.19 (s, 1H), 7.22–7.36 (m,
5H), 7.84 (s, 1H).
13C NMR (d, CDCl3, 75 MHz): 17.09, 24.60, 25.85, 27.70, 31.11,
33.70, 36.74, 39.38, 40.41, 48.20, 51.03, 60.36, 85.1 (t, J = 27 Hz),
118.15, 120.4, 121.52, 123.35, 128.33, 130.02, 130.32, 135.09,
135.47, 144.19, 144.43, 156, 199.12.
13C NMR (d, CDCl3, 75 MHz): 15.19, 23.61, 25.22, 25.66, 32.28,
34.13, 34.87, 36.63, 38.82, 39.70, 40.06, 48.87, 64.71, 94.44,
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404
443
444
445
446
447
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450
451
452
453
454
455
456
457
458
459
460
461
462
463
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469
470
471
472
473
474
475
476
477
107.29, 118.04, 121.43, 123.52, 128.28, 129.24, 130.28, 134.53,
135.41,143.31, 144.82,153.62, 157.24, 199.23.
functional state of the old corpora lutea. Fresh corpora lutea
confirm a recent ovulation. Persisting large functional old corpora
lutea indicate a pure PR-antagonist [6,8] (Fig. 2). Progesterone
secretion of these corpora lutea leads to high progesterone values
in the circulation. The basis of this is the inhibitory effects on the
405
2.3. Biological assays
luteolytic uterine PGF2a-secretion which is progesterone-driven
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
2.3.1. In vitro studies
[8,15]. Typically, beyond uterine growth ‘‘pure’’ PR-antagonists
also lead a proliferation and cornification of the vaginal epithelium
(Table 2/Fig. 3). An advanced stage of shedding of the cornified lay-
ers of the vaginal epithelium prevailed in ovulating controls at this
stage of cycle (metestrus). On rare occasion controls were found in
the process of ovulation on day 18 of the treatment cycle, in this
case showing vaginal proliferation and cornification of the vagina
(Figs. 3 and 4).
Assessment of unopposed estrogenic effects of pure PR-antago-
nists: As uterine growth, vaginal proliferation and cornification
reflect the unopposed effects of the basal ovarian estrogen secre-
tion of the ovary-intact animals. These indicators of estrogen dom-
inance may occur despite the presence of very high levels of
progesterone in the circulation, which is brought about by the
maintenance of corpora lutea (‘‘antiluteolytic effect’’). Estrogen
dominance in the presence of high progesterone shows that the
PR-activation is blocked [8,15].
Assessment of PR-agonistic properties: In the vaginal epithe-
lium these lead to various degrees of inhibition of the ER-stimu-
lated proliferation and cornification. Stronger PR-dominance is
indicated by a fundamental morphological change, the mucifica-
tion of the vaginal epithelium. Ovary: Corpora lutea regress in a
non-fertile cycle. If degeneration of corpora lutea is seen under
an otherwise active PRM, this indicates the presence of PR-agonis-
tic properties as a very sensitive indicator (Fig. 2).
Effects on ovulation: Antiovulatory effects are indicated by
the absence of fresh corpora lutea on cycle day 18, these
effects may result from both PR-agonistic and PR-antagonistic
properties.
Antiprogestational and antiglucocorticoid activity were deter-
mined as previously described using select screen assay system
(Invitrogen-Life Technologies) [3,17,18]. Briefly, PR-UAS-bla HEK
293T and GR-UAS-bla HEK 293T cells were used for the PR antag-
onist screen and the GR antagonistic screen, respectively. Cells
were activated by R5020 (PR agonist) and dexamethasone (GR ago-
nist) for anti-PR and anti-GR screening. 0.032 mL of cell suspension
was added to the wells and pre-incubated at 37 °C/5% CO2 in a
humidified incubator with compounds and control antagonists
for 30 min. 4
l
L of 10ꢀ control agonist R 5020 at the pre-deter-
mined EC80 concentration was added to wells containing the con-
trol antagonist or compounds. The plate was incubated for 16–24 h
at 37 °C/5% CO2 in a humidified incubator. 8 lL of 1 lL substrate
solution was added to each well and the plate was incubated for
2 h at room temperature. The plate was read on a fluorescence
plate reader.
423
2.4. In vivo studies
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
2.4.1. The guinea pig model for the assessment of PR-agonistic and
antagonistic properties of PRMs in non-pregnant animals (Luteolysis
inhibition test)
Dunkin–Hartley Guinea Pigs (400–500 g body weight) were
purchased from Charles River Laboratory. Animals were kept in
an automatically climatized (21 °C) and illuminated (12:12
light/dark cycle) facilities. Tap water was available ad libitum from
sipper tubes; the provided pelleted food fortified with Vitamin C
and supplemented with fruits (oranges).
The studies were performed in cycling guinea pigs for the spe-
cific assessment of both PR-agonistic and PR-antagonistic activity
and the interaction of corresponding properties. The studies were
performed in the second half of the guinea pig cycle which is about
16 days long. The treatment was from cycle day 10–17by daily s.c.
injection of test compounds in 0.2 mL vehicle (benzylbenzoate/cas-
tor oil, ratio 1:4 v/v). Control animals were treated with 0.2 mL
vehicle. The time of autopsy (day 18) is 24–48 h after the expected
ovulation of the next cycle. This timing permits the study of the
effects of the tested compounds on the ovulation and also on the
478
479
480
481
482
483
484
485
2.4.2. Pregnant guinea pig model for the assessment of PR antagonistic
properties
Experiments were done as described earlier [6,8,19]. Female
guinea pigs weighing around 500 g were tested for their cycle stage
by checking the vaginal opening every day. Female animals were
co-caged with a fertile male on day 15 after the vaginal opening.
Day 16 of this cycle was counted as first day of pregnancy if mating
occurred and later on a pregnancy was confirmed by palpation of
(c)
(a)
(b)
Fig. 2. Ovarian histology on day 18 of treatment cycle, (a) 10.0 mg EC339/day s.c.: 3 degenerated corpora lutea (CL), no formation of new ones, (b) 10.0 mg EC317/day s.c.: 3
large functional old CL, no formation of new ones, (c) vehicle control: one degenerated old CL, fresh bulging CL and bursting follicle with ocyte (right).
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Table 2
Summary of molecular properties of new PRM as orientating study concerning the ratio of PR-agonistic and antagonistic and antiovulatory properties in cycling guinea pigs
(treatment from day 10–17 of the cycle, sacrifice day 18, s.c. injection of dose in 0.2 mL vehicle).
⁄⁄
⁄⁄
Code
PR-ant.
GR-ant.
Ovulation inhibition
Uterine weight
ER-/PR balance vagina
Ovary (CL)
Classification
At max. dose (10 mg/day s.c.)
RU 486
CDB 4124
CDB 2914
EC317
EC312
EC313
EC335
EC336
EC339
EC340
100
186
349
267
244
79
34
163
54
100
n.t.
n.t.
9
27
6
83
5
31
13
P3.0 mg
610.0
P10.0 mg
P0.1 mg
P0.1 mg
P0.1 mg
n.t.
10.0 mg inhibitory
610.0 mg
n.t.
1.26
1.41
1.01
2.28
1.03
1.13
n.t.
0.90
0.82
n.t.
ER-domin (P1.0 mg)
ER-domin
ER-domin
ER-domin (P0.1 mg)
PR-domin P0.1 mg
PR-domin (P0.1 mg)
n.t.
PR-domin
PR-domin
deg. and funct. CL
deg. and funct. CL
deg. CL
Large funct. CL (!)
deg. CL
deg. CL
n.t.
deg. CL
deg. CL
PR-antagonist
PR-antagonist
Blunted PR-antagonist
Pure PR-antagonist
Mesoprogestin
Mesoprogestin
n.t.
Mesoprogestin
Mesoprogestin
n.t.
90
n.t.
n.t.
Controls
10/11 ovulation
1.05
Metestrus (9/11) estrus (2/11)
Fresh CL
n.a.
Abbreviations: CL, corpora lutea; deg., degenerating; n.t., not tested; n.a., not applicable.
Signs of ER-dominance: High uterine weight, vaginal epithelium proliferation of basal layers and cornification of upper layers; Signs of PR-dominance: absence of ER-
dominance, mucification of vaginal epithelium.
2.5
2
1.5
1
(n=3)
(n=10)
(n=3)
(n=6)
(n=6)
(n=3)
(n=12)
(n=3)
0.5
0
RU 486 CDB 4124 CDB 2914
10.0mg 10.0mg 10.0mg
EC317
10.0mg
EC312
10.0mg
EC336
10.0mg
EC339
10.0mg
Vehicle
Fig. 3. Uterine weights on day 18 of treatment cycle. The effects of EC317 are statistically significant stronger vs controls and all shown compounds. Effects of RU 486 and CDB
4124 are statistically significant vs controls. Abbreviations: () = n animals/dose.
(b)
(c)
(a)
Fig. 4. Vaginal mucosa on day 18 of treatment cycle: (a) vehicle treated control. Proliferation of squamous epithelium, cornification of upper layers (in desquamation, animal
at ovulation); (b) EC317 10.0 mg/day s.c. unopposed ER-dominance: proliferation and cornification of epithelium, (c) EC339 PR-dominance: non-proliferating and mucified
epithelium.
486
487
488
489
490
491
492
493
494
the abdomen. The pregnant animals were allocated to the different
treatment groups by randomization and were treated on day 43
and 44 of the pregnancy. The test substances were dissolved in
vehicle (benzyl benzoate/castor oil (1:4 v/v)) and subcutaneously
injected (0.2 mL). Animals were checked for vaginal bleeding and
the expulsion of fetuses and placentae until day 50 of pregnancy.
The animals were sacrificed at this time point. Both uterine horns
were inspected with respect to the presence of fetuses, placentae,
and former nidation sites.
495
2.5. Statistical evaluation
496
497
As described in [3], Uterine weights: t-test analysis (unpaired, 2
value, 2 tail, unequal variances).
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523
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525
EC340 was prepared following the Scheme 3.
498
499
3. Results and discussion
Intermediate 4 was dehydrated at 5 position using excess acetic
anhydride and pyridine to afford intermediate 8. Due to its insta-
bility, crude 8 was used as such for the 17-difluoroallyl-lithium
addition at ꢁ100 °C to generate compound 9, which was quickly
hydrolyzed under acidic conditions to afford EC340.
3.1. Chemistry
500
501
The following compounds have been synthesized:
502 Q6
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
526
527
528
529
530
531
532
533
534
535
EC317 was prepared by following the scheme outlined below
(Scheme 1).
Synthesis of EC336 was accomplished following the procedure
outlined in Scheme 4.
Intermediate 2 was synthesized following a literature procedure
[20]. Addition of the aryl cuprate reagent generated by the reaction
of 1,4-diiodo benzene, isopropyl magnesium chloride and catalytic
amounts of cuprous chloride on intermediate 2 afforded compound
3. The aryl iodo derivative 3 obtained was coupled with imidazole
following Ullman reaction conditions employing cuprous iodide
as the copper catalyst and N,N-dimethyl glycine as the ligand to
give compound 4. Pentafluorolithium addition on the 17-keto
group of compound 4 followed by hydrolysis afforded EC317.
EC335 and EC339 were synthesized according to the Scheme 2.
3,3,3-Trifluoropropynyl lithium, generated by treating 2-
bromo-3,3,3-trifluoropropene with LDA at ꢁ78 °C was added to
the 17-ketone of intermediate 4 to form compound 6 which on
acid hydrolysis afforded the compound EC335. Red-Al reduction
of intermediate 6 gave compound 7, which on hydrolysis using
4 N hydrochloric acid furnished EC339.
Intermediate 10 was prepared following the procedure
reported by [21]. An aryl cuprate addition on epoxide 10 using
1,4-diiodo benzene, isopropyl magnesium chloride and cuprous
chloride afforded compound 11. Ullman coupling of intermediate
11 with imidazole using cuprous iodide as the catalyst, N,N-
dimethyl glycine as the ligand and potassium carbonate as the
base furnished intermediate 12 which on acid hydrolysis affor-
ded EC336.
536
3.2. Biological results
537
538
539
540
541
3.2.1. In vitro studies: antiglucocorticoid and antiprogestational
activity
For the determination of the dissociation between antiglucocor-
ticoid and antiprogestational activity transactivation studies were
performed. RU 486 served as standard substance for antiglucocor-
Scheme 1.
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Scheme 2.
Scheme 3.
Scheme 4.
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(a)
(b)
Fig. 5. Effect of pure vs PR-agonistic PRMs on the vaginal epithelium of guinea pigs on day 18 of the treatment cycle-, (a) EC317, 10.0 mg/day s.c., proliferation of squamous
epithelium and cornification of upper layers, (b) EC339, 10.0 mg/day s.c., no basal proliferation, mucification of upper cell layer.
100
80
60
40
20
0
100
80
60
40
20
0
43
44
45
46
47
48
49
50
43
44
45
46
day post coitum
Mifepristone 30mg/a/d
47
48
49
50
day post coitum
vehicle
Mifepristone 3mg/a/d
vehicle
EC 317 30mg/a/d
EC 317 3mg/a/d
Fig. 6. Termination of pregnancy by induction of labor. Treatment of guinea pigs on day 43–44 of pregnancy by s.c. injection of dose in 0.2 mL vehicle
(benzylbenzoate + castor oil 1+4 v/v), controls are vehicle treated. Observation of expulsion of fetuses and placentae until day 50 (autopsy), N = 5/dose).
542
543
544
545
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547
548
570
571
572
573
574
ticoid and antiprogestational activity. Inhibitory activities were
estimated (% of standard compound) (Table 2).
Uterine weight: EC317 elevated the uterine weight more than
two-fold whereas EC336, EC339, EC312, EC313, and CDB 2914
had no or minor effects on uterine weight (Table 2 and Fig. 3).
The weight increase under RU 486 and CDB 4124 was statistically
significant versus controls (Fig. 3).
Clearly, compounds EC317 and EC336 stick out not only
because of a superior inhibition of the progesterone receptor but
also because of the rather low antiglucocorticoid activity indicating
a more than 10-fold dissociation between PR-mediated and GR
mediated activity in vitro.
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
3.2.2.2. Histology of ovaries/corpora lutea, and vaginal epithe-
lium. Out of the 11 vehicle-treated control animals, 10 had fresh
corpora lutea in their ovaries on day 18. This confirms reliable con-
trol of the cycle in the laboratory. According to the postovulatory
stage on day 18, most controls showed a completed shedding of
the cornified layers of the vaginal epithelium (metestrus) at this
time point. Only two control animals showed a natural estrus
(see Figs. 3 and 4). Ovulation: All tested compounds led to the
absence of fresh corpora lutea in the ovaries at 10.0 mg/day which
indicates the inhibition of ovulation at this dose. Some compounds
inhibited the ovulation also at much lower doses (Table 2).
Old CL showed a substance-specific histological appearance.
Large functional CL were seen at 10.0 mg/day EC317 and a wider
range of lower doses (data of latter not shown). Some persisting
CL were also seen after 10.0 mg/day in case of RU 486 and CDB
4124 (Fig. 2, Table 2). The other PRMs including all mesoprogestins
did not interfere with the degeneration of the corpora lutea.
Under the different compounds, different states of the vaginal
mucosa from ER- to PR-dominance, were seen. Pure PR-antagonists
showed strong proliferation of the basal squamous cell layer and a
thick cornified upper layer without any signs of mucification were
seen after treatment with EC317 (Figs. 4 and 5).
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
3.2.2. In vivo characterization
3.2.2.1. PRM-Classification and antiovulatory effects. The plateau of a
dose response curve in case of mixed agonists-/antagonists is
lower compared to an agonist at the respective receptor. This dif-
ference reflects the dynamic balance of opposing agonistic and
antagonistic properties. By the use of a single very high (‘‘plateau’’)
screening dose (10.0 mg/animal s.c.) in cycling guinea pigs this
interference was tested and used for a first classification of com-
pounds. Lower doses were only tested for the more interesting
compounds, and also in order to determine the threshold of antiov-
ulatory activity (see Table 2).
The evaluation of this high dose of the test compounds led in all
cases to distinct and compound-specific results, reflecting the
dynamic balance of PR-agonistic and PR-antagonistic properties.
Both, compounds classified as pure PR-antagonist (see EC317)
and PR-agonistic PRMs (mesoprogestins, e.g. EC312, EC313) [3]
may exert very potent antiovulatory effects. As a rule, the com-
pound-specific effects on genital tract and on ovulation are lost
in the same range of the tested lower doses. All compounds
described were assessed with different dose dependent concentra-
tions of 0.1, 3.0 and 10 mg/animal.
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598
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667
RU 486 induces strong proliferation and cornification of the
vaginal epithelium; however, the mucification of the upper layers
of the vaginal epithelium indicates a disturbance of the cornifica-
tion process by PR-agonistic activity. RU 486 may thus not be clas-
sified as ‘‘pure’’ antagonist in this animal model.
Diminished ER-dominance: Compared to EC317 CDB 2914 led
to a reduced and/or atypical cornification of the vaginal epithe-
lium. After treatment with EC336 and EC339 there was no cornifi-
cation of the upper layers of the epithelium. Mucification of the
epithelium indicates that these compounds are mesoprogestins
(Fig. 5). This also applies to EC312 and EC313.
erative and antiovulatory effects but lacking labor inducing proper-
ties. These mesoprogestins may open new avenue for therapies for
chronic gynecologic disorders such as endometriosis and fibroid
disease [3].The avoidance of unopposed estrogenic effects in the
human endometrium is the key safety issue of this kind of chronic
treatment. The lack of labor inducing properties (data not shown)
will be important with respect to the careful elimination of a mis-
use potential. The absence of abortifacient properties may also
open new options for the treatment of infertility which is an appar-
ent issue in case of endometriosis.
668
Acknowledgements
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4. Clinical significance
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We thank Dr. Katarina Jewgenow (IZW) for valuable advice and
help performing the morphological evaluation, Mario Moreno for
performing the animal studies and Monika Blankenburg for skillful
help during the preparation of the manuscript. Dr. Harald Schubert
and Dr. Sabine Bischoff from the Institute of Animal Science and
Animal Welfare, Friedrich-Schiller-University Jena, were helpful
supporting the animal studies in the ethical committee and provid-
ing the facilities for their performance, which is gratefully
acknowledged.
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EC317 shows all attributes of a complete progesterone receptor
antagonist lacking partial agonistic activity. Such a pharmacologi-
cal profile might offer advantages in indications like postcoital fer-
tility control [2] and induction of labor [22]. Ulipristal has been
approved for the indication of postcoital fertility control. It is cur-
rently believed that Ulipristal’s activity in this indication is based
on the inhibition of ovulation [23]. The antiovulatory potency of
EC317 and Ulipristal was therefore assessed in the guinea pig
model (Table 2). EC317 clearly shows superior antiovulatory activ-
ity being 3–10 times as potent as Ulipristal. It is superior PR-antag-
onistic properties may further contribute to the efficacy of
postcoital treatment.
RU 486 has been approved for the induction of abortion up to
pregnancy of week 20. Data concerning human pregnancy are
available for this compound when given alone and in combination
with prostaglandins. A major issue of both approaches is a certain
rate of failures to terminate the pregnancy. Incomplete abortions
and strong bleedings were particularly seen after the use of RU
486 without a prostaglandin [1,2,24].
The inferior efficacy of RU 486 concerning the induction of labor
may partly be explained by a counter-productive PR-agonistic
action in the myometrium. Therefore, studies with RU 486 and
EC317 were performed with respect to their ability to induce labor.
This might be the key mechanism of PRMs action in the termina-
tion of pregnancy in the human and the guinea pig. If this assump-
tion is correct compounds lacking partial PR-agonistic activity
should exhibit a higher labor inducing activity than RU 486 or Uli-
pristal. Data of the performed comparative studies at different dose
levels support this view. Fig. 6 shows that EC317 indeed induces
labor much faster and in a higher rate of animals than RU 486.
678
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Synthesis and biological characterization of new 11 imidazolyl-
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