Mepyramine-JNJ7777120-hybrid compounds show high affinity to hH 1R, but low affinity to hH4R

Article abstract of DOI:10.1016/j.bmcl.2011.09.001

In literature, a synergism between histamine H₁ and H ₄ receptor is discussed. Furthermore, it was shown, that the combined application of mepyramine, a H₁ antagonist and JNJ7777120, a H ₄ receptor ligand leads to a synergistic effect in the acute murine asthma model. Thus, the aim of this study was to develop new hybrid ligands, containing one H₁ and one H₄ pharmacophor, connected by an appropriate spacer, in order to address both, H₁R and H ₄R. Within this study, we synthesized nine hybrid compounds, which were pharmacologically characterized at hH₁R and hH₄R. The new compounds revealed (high) affinity to hH₁R, but showed only low affinity to hH₄R. Additionally, we performed molecular dynamic studies for some selected compounds at hH₁R, in order to obtain information about the binding mode of these compounds on molecular level.

Full text of DOI:10.1016/j.bmcl.2011.09.001

Bioorganic & Medicinal Chemistry Letters 21 (2011) 6274–6280
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Mepyramine–JNJ7777120-hybrid compounds show high affinity to hH1R,
but low affinity to hH4R
Eva Wagner a, Hans-Joachim Wittmann b, Sigurd Elz a, Andrea Strasser c,
⇑
a Department of Pharmaceutical/Medicinal Chemistry I, Institute of Pharmacy, University of Regensburg, D-93040 Regensburg, Germany
b Faculty of Chemistry and Pharmacy, University of Regensburg, D-93040 Regensburg, Germany
c Department of Pharmaceutical/Medicinal Chemistry II, Institute of Pharmacy, University of Regensburg, Universitätsstraße 31, D-93040 Regensburg, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
In literature, a synergism between histamine H1 and H4 receptor is discussed. Furthermore, it was shown,
that the combined application of mepyramine, a H1 antagonist and JNJ7777120, a H4 receptor ligand
leads to a synergistic effect in the acute murine asthma model. Thus, the aim of this study was to develop
new hybrid ligands, containing one H1 and one H4 pharmacophor, connected by an appropriate spacer, in
order to address both, H1R and H4R. Within this study, we synthesized nine hybrid compounds, which
were pharmacologically characterized at hH1R and hH4R. The new compounds revealed (high) affinity
to hH1R, but showed only low affinity to hH4R. Additionally, we performed molecular dynamic studies
for some selected compounds at hH1R, in order to obtain information about the binding mode of these
compounds on molecular level.
Received 15 June 2011
Revised 31 August 2011
Accepted 1 September 2011
Available online 7 September 2011
Keywords:
Histamine H1 receptor
Histamine H4 receptor
Mepyramine
Ó 2011 Elsevier Ltd. All rights reserved.
JNJ7777120
Hybrid compounds
Molecular dynamics
Histamine H1 receptor antagonists are used in general for the
treatment of allergic reactions, whereas the histamine H4 receptor
is suggested to be involved in allergic diseases, like conjunctivitis,
rhinitis or bronichal asthma as well as in atopic dermatitis and pru-
ritus.1–4 Mepyramine 1 (Scheme 1) is a prominent H1R antagonist,
whereas JNJ7777120 2 (Scheme 1) shows high affinity to the
H4R.4 In 2003 JNJ7777120 2 was described as a potent and selective
H4 antagonist, which has meanwhile established to a H4R standard
antagonist.5 Further studies revealed that JNJ7777120 acts as in-
verse agonist at hH4R but as partial agonist at mH4R.6 Recently, it
was shown experimentally, that the combined application of
mepyramine 1 and JNJ7777120 2 in the acute murine asthma model
leads to a synergistic effect.7 Thus, the development of combined
H1/H4-receptor ligands may be a worthwhile goal for treatment of
allergic reactions,1 since differences in bioavailability are expected
if two drugs are administered. This is not the case, if H1R and H4R
can be addressed with only one drug. Furthermore, ligands address-
ing both H1R and H4R are important pharmacological tools to get
deeper insights with regard to ligand binding and selectivity on
molecular level. One strategy for development of dual H1/H4-recep-
tor ligands is the connection of one H1- and one H4-pharmacophor
by a spacer. This concept was already applied by Schunack with re-
gard to H1R and H2R.8,9 Since the combined application of mepyra-
mine 1 and JNJ7777120 2 lead to the synergistic effect in the acute
murine asthma model,7 the aim of this study was to synthesize and
pharmacologically characterize a number of compounds, combin-
ing mepyramine as H1- and JNJ7777120 as H4-pharmacophor.
The hybrid ligands 16–21 were obtained as described
(Scheme 2). The structures of compounds 26, 38 and 45 are pre-
sented in Scheme 3, whereas the strategy with regard to synthesis
can be found in the supplementary material. Further details with
regard to synthesis, as well as analytics of all hybrid compounds
are given in the supplementary material.
The synthesized compounds were routinely investigated in
competition binding assays. In case of hH1R, Sf9 cell membranes,
coexpressing hH1R and RGS4 were used for competition binding
assays in presence of 5 nM [3H]mepyramine.10 In case of hH4R,
Sf9 cell membranes, coexpressing hH4R-RGS19, Gai2 and Gb1c2
were used for competition binding assays in presence of 10 nM
[3H]histamine.11 Furthermore, some selected compounds were
analyzed at hH4R with the GTPcS-assay in order to determine
the efficacy.12 Additionally, most of the new compounds were
tested routinely on isolated guinea-pig ileum.13 Since only H1R,
but not H4R is expressed on ileum, in organ pharmacology, assays
at guinea-pig ileum are well established in order to study the affin-
ity and functionality at gpH1R. The histamine-induced contraction
of the guinea-pig ileum is measured in presence and absence of an
antagonist.13
Since the new hybrid compounds showed affinity to H1R, but
did not act as (partial) agonists at H1R, a model of hH1R in the inac-
tive conformation was generated by homology modelling, based on
⇑
Corresponding author. Tel.: +49 941 943 4821; fax: +49 941 943 4820.
E-mail address: andrea.strasser@chemie.uni-regensburg.de (A. Strasser).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.09.001

E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
6275
to the Lennard-Jones energy (short-range) interaction energies be-
tween 16 (À252 1 kJ/mol) or 19 (À253 1 kJ/mol) and hH1R (Ta-
ble 2). Thus, the dynamic studies support the hypothesis that the
piperazine moiety disturbs the electrostatic interaction between
16 and hH1R. This difference in the short range coulomb interac-
tion is reflected by the experimentally determined pKi values of
16 and 19 at hH1R (Fig. 1A). However, during the molecular dy-
namic simulations, a stable hydrogen bond interaction could be de-
tected between the carbonyl moiety of 16 and Asn2.61 (Fig. 2).
Additionally, an aromatic interaction between the indole moiety
of 16 and Tyr2.64 was observed during the simulation (Fig. 2). In
compound 19, the amino moiety, suggested to interact with
Asp3.32 is flexible, analogous to mepyramine itself and in contrast
to compounds 16–18. Thus, the interaction between the amine
moiety and Asp3.32 can be established well. This is also confirmed
by the stronger electrostatic interaction between hH1R and 19,
compared to 16 (Fig. 2). However, the elongation of mepyramine
by the JNJ7777120 partial structure did not lead to an increased
affinity at hH1R, compared to mepyramine 1. Since there is a signif-
icant difference in affinity of 19 and 20 at hH1R, it may be sug-
gested, that the additional JNJ7777120 partial structure interacts
specifically with the hH1R. A stable hydrogen bond was detected
during the molecular dynamic simulation between the carbonyl
moiety of 19 and Thr182 (E2-loop) (Fig. 2). The exchange of the
piperazine moiety by a more flexible aminopyrrolidine moiety 26
leads only to a slight decrease in affinity at hH1R, compared to
16. The diphenhydramine—JNJ-hybrid compound 21, analogue to
the mepyramine—JNJ-hybrid compound 16, leads to a decrease in
affinity of about 1 log unit at hH1R, compared to diphenhydramine
3. For the analogoue astemizole–JNJ-hybrid compound 45, only a
slight decrease in affinity was observed at hH1R, compared to
astemizole 4. Thus, the introduction of a JNJ partial structure into
mepyramine and diphenhydramine leads to a stronger decrease
in affinity, compared to the corresponding H1 antagonists. In con-
trast, the JNJ–astemizole hybrid shows an affinity in the same
range as found for astemizole (Fig. 3). Compound 38 shows a sig-
nificant decrease in affinity at hH1R, compared to 19. In 38, the
JNJ partial structure is connected to mepyramine via the indole
moiety, whereas in 19, the JNJ partial structure is connected via
the piperazine moiety to mepyramine. Thus, this switch is sug-
gested to be responsible for the observed differences in affinity.
Compound 38 was obtained experimentally as racemate, but in
molecular modelling, both enantiomers were analyzed (Fig. 2).
Molecular dynamic simulations revealed a stable binding mode
for both enantiomers. The mepyramine partial structure (for both
enantiomers) is located in the same part of the binding pocket,
as already described for 16 or 19 and the positively charged amino
moiety of 38 (both enantiomers) interacts electrostatically with
Asp3.32. Molecular dynamic simulations revealed a stable hydrogen
bond interaction between the carbonyl moiety of 38 (R- and S-con-
figuration) and Trp7.40. For 38 (S-configuration), the carbonyl
Scheme 1. Structures of H1 (mepyramine, 1; diphenhydramine, 3; astemizole, 4)
and H4 (JNJ7777120, 2; JNJ-derivative, 5; JNJ-derivative, 6) receptor ligands.
the crystal structure 2RH1,14 analogue, as already described.15
A
comparison of our H1R homology model, refined by molecular dy-
namic simulations, with the recently published hH1R crystal16
showed no significant differences. The compounds 16, 19 and 38
were docked manually into the binding pocket of hH1R using the
software package SYBYL 7.0 (Tripos Inc.). Molecular dynamic sim-
ulations, using the software GROMACS 4.0.2 (http://www.gro-
macs.org), were performed, as already described.10 Ligand
parameterization was obtained from the PRODRG server (http://
davapc1.bioch.dundee.ac.uk/prodrg/). For both compounds a 6 ns
productive phase in molecular dynamic simulations was per-
formed subsequent to a 1 ns equilibration phase.
The pharmacological and modeling data of reference com-
pounds and the new hybrid compounds are given in Tables 1–4.
For compounds 16 and 19, the experimental pharmacological data
are shown in Figure 1.
Compared to mepyramine, the affinity of compounds 16–18 is
significantly reduced of about 1.5–2 log units at hH1R. The intro-
duction of one chlorine atom in the indole moiety 17 leads to a
slight decrease in affinity to hH1R, compared to 16. The exchange
of the indole moiety 16 into a benzimidazole 18 leads to a decrease
in affinity at hH1R. For compound 19, an affinity comparable to that
of mepyramine 1 at hH1R could be observed. The introduction of
one chlorine atom on the corresponding position in the
JNJ7777120 partial structure 20 leads to a significant decrease in
affinity at hH1R, compared to 19. In compounds 16–18, the basic
nitrogen atom is embedded in a piperazine moiety, which shows
a higher rigidity than an ethylene spacer. This more voluminous
piperazine moiety is suggested to disturb the electrostatic interac-
tion between the positively charged amine and Asp3.32, leading to a
significantly decreased affinity. Based on the molecular dynamic
studies, a mean coulomb energy (short range) between 16 and
hH1R of about À157 1 kJ/mol was detected (Fig. 2). In contrast,
a coulomb energy (short range) of À197 1 kJ/mol was detected
between 19 and hH1R (Fig. 2, Table 2). Both interaction energies
are, according to a t-test, significant different to each other (p
<0.0001). In contrast, there is no significant difference with regard
moiety establishes an additional hydrogen bond to Asn2.61
.
Aromatic interactions between the indole moiety of 38 and the
receptor were not detected. However, both enantiomers showed
slight differences in conformation in its receptor bound state. The-
ses differences are reflected in the interaction energy between 38
and hH1R. Between the R enantiomer of 38 and hH1R, a coulomb
energy (short range) of À166 3 kJ/mol and a Lennard–Jones
energy (short range) of À285 2 kJ/mol was observed. In contrast,
between the S enantiomer of 38 and hH1R, a coulomb energy (short
range) of À241 2 kJ/mol and a Lennard–Jones (short range) of
À284 1 kJ/mol was observed (Table 2).
As shown in Table 2, a comparison of the calculated ligand-
receptor-interaction energies (C+LJ LR, Table 2) does not reflect
the observed pKi values of 16, 19 and 38. However, this observation
can be explained: During molecular dynamic simulations, the

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E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
Scheme 2. Synthesis of the hybrid compounds 16–21. A detailed information with regard to synthesis and analytic data is available in the Supplementary data.
penetration of water molecules from the extracellular side into the
binding pocket could be observed. These internal water molecules
interact with the ligand and with the receptor and mediate ligand–
receptor-interactions. Thus, a term, quantifying the interaction be-
tween ligand and internal water has to be introduced (Table 2).
Taking into account both, interaction of the ligand with the recep-
tor and with the internal water leads to a good correspondence
with the experimentally observed pKi values. Additionally, before
establishing the ligand–receptor-complex, the ligand is solved in
aqueous solution. Thus, for transfer of the ligand from aqueous
solution into the binding pocket of the receptor, changes in solva-
tion energies have to be taken into account. Changes in Gibbs en-
ergy of solvation for the ligand can be calculated by molecular
dynamic studies.18
The predicted changes in Gibbs energy of solvation for the
transfer of 16, 19 and 38 from aqueous phase into binding pocket
of hH1R (D
G0sol (water?hH1R)) exhibit a quite well correlation with
the experimentally determined pKi values (Table 3). Furthermore,
these data reveal also the importance to take into account the
Gibbs energy of solvation for the ligand in aquous solution (
D
G0sol
(L, wat)). Only looking onto
D
G0sol (L, hH1R) would lead to wrong
predictions. However, calculations of Gibbs energies of solvation
for the transfer of a ligand from aqueous phase into binding pocket
of a GPCR are rarely found in literature. Thus, more data have to be
obtained in future on different GPCRs in order to judge the predic-
tive quality of such calculations.
None of the hybrid compounds revealed (partial) agonism at
gpH1R. Exemplary for compounds 16 and 19, the dose-response

E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
6277
For compounds 16–21, 26, 38 and 45, the pA2 values are found
in a range from about 7.7 up to 8.4, whereas the pKi values at
hH1R are found in a range from about 6.1 up to 8.3. There might
be two reasons for these differences: First, the data at gpH1R are
functional data obtained from isolated organ experiments, whereas
the data at hH1R are binding data. Secondly and more importantly,
species differences between hH1R and gpH1R should be taken into
account. Asn2.61, for example, was identified to be responsible for
species differences between hH1R and gpH1R, especially in case
of long and bulky ligands.20
All analyzed hybrid compounds 16–21, 26, 38 and 45 exhibit
only low affinity to hH4R in a range of about 4.5 to 5.2. Thus, com-
pared to JNJ7777120 or to the corresponding JNJ-analogues 5 and 6,
the affinity is significantly decreased (Fig. 3). The introduction of a
chlorine into the indole moiety of 5, leading to JNJ7777120 (compd
2), results in a significant increase in affinity at hH4R.11 Correspond-
ing structure-activity relationships could not be observed for the
analogue series 16?17 and 19?20 (Fig. 3). Two reasons may ex-
plain the experimental data: The hH4R does not tolerate any linker
and/or linked groups. Furthermore, it can be speculated that the
binding mode of the JNJ-partial structures in the hybrid compounds
at hH4R might be different to the JNJ-derivatives itself. In literature,
two completely different binding modes for JNJ-derivatives at H4R
are described. Within a modelling study, an interaction of the in-
dole-NH with Asp3.32 and an interaction of the positively charged
piperazine moiety with Glu5.46 is suggested.21 A different binding
mode, the positively charged piperazine moiety interacting with
Asp3.32, was found within an other modelling study.11 In this case,
the indole moiety is embedded in a small pocket between Glu5.46
Scheme 3. Structures of compounds 26, 38 and 45. A detailed information with
regard to synthesis and analytic data is available in the Supplementary data.
Table 1
and Trp6.48 11
With the latter binding mode, structure-activity rela-
.
Binding affinities and functional data of the reference compounds and the hybrid
compounds determined in the competition binding assay and on the isolated guinea
pig ileum
tionships of JNJ-derivatives with different substitution patterns in
the indole moiety could be explained.11 In compounds 19 and 38,
the mepyramine partial structure is connected differently to the
JNJ partial structure. Compound 19 should show affinity to hH4R,
if the binding mode of JNJ7777120 presented by Schneider et al is
energetically preferred.11 Here, the piperazine moiety is suggested
to interact with Asp3.32. Thus, there is space left in the binding pock-
et in direction to TM II for a ligand elongation at the piperazine moi-
ety. In contrast, compound 38 should show affinity to hH4R, if the
binding mode of JNJ7777120 presented by Jojart et al. is energeti-
cally preferred.21 Here, the indole moiety is suggested to interact
with Asp3.32. Thus, there is space left in the binding pocket in direc-
tion to TM II for a ligand elongation at the indole moiety. Unfortu-
nately, both compounds, 19 and 38, exhibit only poor affinity to
hH4R. One reason for the poor affinity of 38 to hH4R, might be a
wrong connection point of the mepyramine with the indole moiety.
It can be speculated that a different aromatic substitution position
might lead to higher affinities at hH4R. However, it is noteworthy,
that a JNJ derivative with an amino moiety in 5-position ((5-ami-
no-1H-indol-2-yl)(4-methylpiperazin-1-yl)methanon) is described
in literature5 with an pKi value of about 7.8 at hH4R. In contrast,
pKi (hH1R)
pKi (hH4R)
pA2
(Sf9)a
(Sf9)b
(gp-ileum)c
Mepyramine, 1
JNJ7777120, 2
Diphenhydramine, 3
Astemizole, 4
JNJ derivative, 5
JNJ derivative, 6
16
17
18
19
20
21
26
38
45
8.35 0.0317
4.33 0.12
7.83 0.0317
8.68 0.05
n.d.
<47
9.07 0.0313
5.80 0.13
7.93 0.04d
8.42 0.10
n.d.
7.73 0.0411
4.37 0.107
5.10 0.067
6.86 0.0511
6.54 0.0411
5.23 0.09
4.80 0.29
4.65 0.04
5.05 0.11
5.17 0.09
4.75 0.14
4.56 0.09
4.85 0.09
4.98 0.04
n.d.
n.d.
6.77 0.05
6.11 0.08
6.22 0.07
8.15 0.10
7.00 0.03
6.65 0.06
6.34 0.10
6.67 0.09
8.26 0.17
7.97 0.08
7.69 0.09d
8.14 0.09
8.31 0.08d
8.12 0.11d
n. d.
8.07 0.06
7.90 0.06d
8.42 0.08d
a
Affinities at hH1R, coexpressed with RGS4 in Sf9 cell membranes in the
[3H]mepyramine competition binding assay. KD(mepyramine) at hH1R:
4.49 0.35 nM.10
b
Affinities at hH4R-RGS19, coexpressed with Gai2 and Gb1 in Sf9 cell mem-
c
2
branes in the [3H]histamine competition binding assay. KD(histamine) at hH4R:
9.8 0.9 nM.6
in our competition binding assay,
a pKi of 6.80 0.13 was
c
Incubation time: 15 min. For most analyzed compounds, a depression in his-
determined. In general, the data within this study show that more
experimental and modeling studies at hH4R have to be performed,
in order to get a more detailed insight into interaction of ligands
with hH4R on molecular level.
In order to obtain information, if the hybrid compounds act as
partial agonists, antagonists or inverse agonists at hH4R, we per-
tamine induced contractile effect was observed for higher ligand concentrations. A
more detailed description of experimental methods is described by Elz et al.13
d
Slope in Schild plot analysis was set to 1. Results of Schild plot analysis with
observed slope m (cpd., m, pA2): 3, 0.8, 8.37; 17, 1.3, 7.50; 19, 1.3, 7.88; 20, 1.8, 7.46;
38, 1.3, 7.56; 45, 1.7, 7.83.
formed for two selected compounds 16 and 19 a GTPcS-assay
(Fig. 1B, Table 4).
curves at gpH1R are shown (Fig. 1C). For some ligands, for example,
19, the dose-response curves show a strong depression at higher
ligand concentrations. A reason for this partially insurmountable
antagonism may be a slow rate of dissociation kinetics of the
antagonist, resulting in hemi-equilibrium conditions.19 In general,
the pA2 values at gpH1R are higher, than the pKi values at hH1R.
The data revealed, that 16 acts as a partial agonist at hH4R,
whereas 19 shows inverse agonism (Fig. 1B). The partial agonism
of 16 at hH4R is unexpected, since mepyramine and JNJ7777120
were identified as inverse agonists at hH4R.7,22
A comparison of the pharmacological data between hH1R and
hH4R shows, that the H1R tolerates the linking of an H1R antagonist

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E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
Table 2
Calculated interaction energies between ligand and hH1R or ligand and internal water for compounds 16, 19 and 38
C LR (kJ/mol) LJ LR (kJ/mol) C LW (kJ/mol) LJ LW (kJ/mol) C+LJ LR (kJ/mol)
C+LJ LW (kJ/mol)
C+LJ LR+LW (kJ/mol)
16
19
38 (R)
38 (S)
À157
À197
À166
À243
1
1
1
1
À252
À253
À286
À286
1
1
1
1
À119
À186
À94
1
1
1
1
À32
À47
À51
À33
1
1
1
1
À409
À450
À452
À529
2
2
2
2
À151
À233
À145
À76
2
2
2
2
À560
À683
À597
À605
2
2
2
2
À43
The interaction energies were calculated with GROMACS. C: Coulomb (short range); LJ: Lennard–Jones (short range); LR: interaction between ligand and hH1R; LW:
interaction between ligand and internal water.
Figure 1. (A) Competition binding isotherms for compounds 16 and 19 at hH1R, coexpressed with RGS4 in Sf9 cell membranes. (B) Functional GTP
cS binding assay for
compounds 16 and 19 at hH4R-RGS19 coexpressed with G i2 and Gb1 2 in Sf9 cell membranes. (C) Contraction of guinea-pig ileum (whole segments) by histamine in absence
a
c
and presence of the inhibitors 16 and 19. Inset: Schild plot for the corresponding inhibitor.
to JNJ7777120. But affinity is dependent from linker length. In con-
trast, the hH4R does not tolerate linked pharmacophores, since the
affinity of all analyzed hybrid compounds was significantly de-
creased compared to JNJ7777120. All hybrid compounds were
antagonists at gpH1R. In contrast, the hH4R is sensitive with regard
tolinkerlengthconcerningtheefficiency. Here, thelinkerlengthacts
as a partial (16)–inverse (19) agonism switch at hH4R. Thus, linker
length has completely different influences onto pharmacology of
hH1R and hH4R.
Within this study we presented new hybrid compounds with
different H1- and H4-pharmacophores. These compounds showed
(high) affinity to hH1R, but rather low affinity to hH4R. However,

E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
6279
Figure 2. Binding mode of 16, 19 and 38 at hH1R and interaction energy between 16, 19 or 38 with hH1R or internal water, obtained by molecular dynamics.
similar studies with regard to H1/H2-hybrid compounds showed
that high affinity to both receptors is only achieved for distinct
H1/H2-pharmacophores.8,9 Thus, the connection of H1-antagonis-
tic pharmacophores with H4-pharmacophores, different from
the JNJ partial structure may lead to compounds with high
affinity to both, H1R and H4R. However, this study revealed

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E. Wagner et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6274–6280
Table 4
Efficacies of selected compounds 16 and 19 in the GTP
c
S-assay at hH4R
Efficacy Emax (%)
Potency pEC50
histamine
JNJ7777120, 2
16
19
n.d.
n.d.
1.00a
À0.74 0.19b
0.88 0.18
<À1c
3.98 0.31
<4c
a
The efficacy of histamine was determined at a concentration of 10
l
M and set
to 1.00 (pEC50 = 7.86 0.2022
)
b
The efficacy of JNJ7777120 was determined at a concentration of 10
lM and
was determined relative to the efficacy of histamine (pEC50 = 7.80 0.21,
Emax = À0.5922
)
c
A rapid decrease in [35S]GTP
c
S binding was observed for concentrations of 19
greater than 100
exactly.
lM, thus, neither potency nor efficacy could be determined
Acknowledgments
We are grateful to Christine Braun, Kerstin Röhrl and Gertraud
Wilberg for expert technical assistance. This work was supported
by the Deutsche Forschungsgemeinschaft (Project STR 1125/1-1
and the Graduate Training Program (Graduiertenkolleg) GRK 760,
‘Medicinal Chemistry: Molecular Recognition—Ligand–Receptor
Interactions’).
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.09.001.
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Figure 3. Trends in affinities at hH1R and hH4R.
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Table 3
Calculated Gibbs energy of solvation for compounds 16, 19 and 38 in water and in the
binding pocket of hH1R
D
G0sol (L, wat)
D
G0sol (L, hH1R)
DDG0sol (water?hH1R)
16
19
38 (R)
38 (S)
À171
À145
À248
À243
2
3
4
3
À446 21
À436 16
À515 18
À507 16
À275 23
À291 19
À267 22
À264 19
The calculations were performed, based on the thermodynamic integration method,
using the coupling parameter k, switching on, respectively off the interaction
between ligand and surrounding, as described previously.18
D
G0sol (L, wat) corre-
sponds to the Gibbs energy of solvation of the ligand L in water,
D
G0sol (L, hH1R)
corresponds to the Gibbs energy of solvation of the ligand L in the binding pocket of
hH1R and DDG0sol (water?hH1R) corresponds to the change in Gibbs energy of
solvation for transferring the ligand from water into binding pocket of hH1R
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Seifert, R.; Schneider, G.; Stark, H. Bioorg. Med. Chem. 2009, 17, 7186.
important insights into structure–activity relationships at hH1R
and hH4R.