Structure and activity relationship in the (S)-N-chroman-3-ylcarboxamide series of voltage-gated sodium channel blockers

Article abstract of DOI:10.1016/j.bmcl.2012.06.105

Recent findings showing a relation between mutations in the Na _V1.7 channel in humans and altered pain sensation has contributed to increase the attractiveness of this ion channel as target for development of potential analgesics. Amido chromanes 1 and 2 were identified as blockers of the Na_V1.7 channel and analogues with modifications of the 5-substituent and the carboxamide part of the molecule were prepared to establish the structure-activity relationship. Compounds 13 and 29 with good overall in vitro and in vivo rat PK profile were identified. Furthermore, 29 showed in vivo efficacy in a nociceptive pain model.

Full text of DOI:10.1016/j.bmcl.2012.06.105

Bioorganic & Medicinal Chemistry Letters 22 (2012) 5618–5624
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Structure and activity relationship in the (S)-N-chroman-3-ylcarboxamide
series of voltage-gated sodium channel blockers
Inger Kers a, , Gabor Csjernyik a, Istvan Macsari a, Martin Nylöf a, Lars Sandberg a, Karin Skogholm a,
⇑
Tjerk Bueters b, Anders B. Eriksson c, Sandra Oerther d, Per-Eric Lund d, Elisabet Venyike d,
Jan-Erik Nyström c, Yevgeni Besidski a
a Medicinal Chemistry, CNSP iMed Science, AstraZeneca R&D, Innovative Medicines, SE-15185 Södertälje, Sweden
b DMPK, CNSP iMed Science, AstraZeneca R&D, Innovative Medicines, SE-15185 Södertälje, Sweden
c CNSP iMed Project Management, AstraZeneca R&D, Innovative Medicines, SE-15185 Södertälje, Sweden
d Neuroscience, CNSP iMed Science, AstraZeneca R&D, Innovative Medicines, SE-15185 Södertälje, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
Recent findings showing a relation between mutations in the NaV1.7 channel in humans and altered pain
sensation has contributed to increase the attractiveness of this ion channel as target for development of
potential analgesics. Amido chromanes 1 and 2 were identified as blockers of the NaV1.7 channel and ana-
logues with modifications of the 5-substituent and the carboxamide part of the molecule were prepared
to establish the structure–activity relationship. Compounds 13 and 29 with good overall in vitro and
in vivo rat PK profile were identified. Furthermore, 29 showed in vivo efficacy in a nociceptive pain
model.
Received 7 June 2012
Revised 28 June 2012
Accepted 29 June 2012
Available online 7 July 2012
Keywords:
(S)-N-Chroman-3-ylcarboxamide
Nav1.7 blocker
Ó 2012 Elsevier Ltd. All rights reserved.
Neuropathic pain
Sodium channel blockers
Voltage-gated channel
Voltage-gated sodium channels (VGSC) play a critical role in
electrical signaling in the nervous system and are responsible for
the initiation and propagation of action potentials caused by vari-
ations in membrane potentials.1 Nerve signal transduction can be
affected by altered rapid opening and closing of VGSCs and these
channels are important targets in the pharmaceutical industry in
regards to finding treatment for cardiac conductance disturbances,
epilepsy and pain disorders.2 Inherited loss of function mutations
of NaV1.7 in humans were reported to cause congenital inability
to experience pain.3,4 In addition, gain of function mutations have
been connected to inheritable pain conditions erythromelalgia and
familial rectal pain.5 These observations make NaV1.7 an attractive
target for development of potential analgesics. Current sodium
channel blocker therapies available have issues with tolerability
and finding more potent compounds with higher subtype selectiv-
ity have potentially an important impact on treatment options for
neuropathic pain.6
initially identified through HTS screening using a Li+ flux atomic
absorption spectroscopy assay.7 Compound 1 showed moderate
potency on NaV1.7 and moderate selectivity over NaV1.5, as mea-
sured in a whole-cell voltage clamp electrophysiology assays.8,9
The NaV1.5 channel is widely expressed in heart muscle and
inhibition leads to ventricular arrhythmia, therefore very high
O
O
O
O
F
N
H
N
H
F
F
N
N
N
N
O
O
1
2
NaV1.7 pIC50 5.7
NaV1.5 pIC50 5.7
NaV1.7 pIC50 6.0
NaV1.5 pIC50 <5.2
As a part of our preclinical NaV1.7 channel blocker program
aimed to discover novel analgesic drug candidates we examined
a series of amido chromanes substituted at C-5 position. The initial
hit series is represented by 1 and 2 (Fig. 1). The compounds were
clogP 4.2
clogP 4.64
hERG pIC50 5.1
hERG pIC50 5.2
Solubility 27 µM
Solubility 1 µM
RLM Clint 18 µL/min/µg
HLM Clint 2.5 µL/min/µg
RLM Clint 82 µL/min/µg
HLM Clint 361 µL/min/µg
⇑
Corresponding author. Tel.: +46 8 553 28609.
E-mail addresses: inger.kers@telia.com, inger.kers@astrazeneca.com (I. Kers).
Figure 1. Profile of initial hits, chromanes 1 and 2.
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.06.105

I. Kers et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5618–5624
5619
Table 1
Chromanes with piperazine or pyridine as R1 substituent
O
O
NaV1.7
pIC50
NaV1.5
pIC50
hERG
pIC50
Solubility
M)
RLM/HLM Clint (
ll/
R1
R2
cLogP
3.82
3.80
R2
(
l
min/ g)
l
N
H
R1
*
*
N
F
F
3
4
6.1
6.2
5.3
5.3
5.1
4.9
82
<10/<10
<10/<10
N
N
N
O
O
N
F
*
*
*
*
F
F
F
N
379
N
*
N
N
N
N
N
5
6
6.5
6.8
5.3
5.6
5.1
5.0
3.53
4.53
211
4/14
N
*
N
N
4
9/stable
N
*
*
*
*
*
*
F
F
F
F
F
7
8
5.8
5.9
NDa
5.5
NDa
NDa
4.86
4.65
NDa
NDa
NDa
N
N
O
O
O
F
F
5
F
F
9
6.
5.4
5.5
5.5
5.6
4.6
5.2
4.65
4.19
4.19
2
NDa/78
64/161
77/59
N
*
*
*
*
F
F
10
11
7.1
7.0
29
9
N
N
N
O
O
O
N
F
F
F
*
F
F
N
*
F
F
12
13
6.4
6.8
5.4
5.2
4.6
5.0
4.99
3.60
1.1
10/19
N
F
O
*
*
F
F
N
O
58
<10/10
N
F
HO
(continued on next page)

5620
I. Kers et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5618–5624
Table 1 (continued)
O
O
NaV1.7
pIC50
NaV1.5
pIC50
hERG
pIC50
Solubility
M)
RLM/HLM Clint (
ll/
R1
R2
cLogP
R2
(
l
min/ g)
l
N
H
R1
*
*
F
F
N
N
O
O
14
6.3
6.8
5.2
5.1
4.8
4.8
3.60
17
54
<10/15
<10/11
N
F
OH
*
*
*
*
*
F
F
F
F
F
O
O
O
15
16
17
18
3.35
3.21
3.80
3.90
N
HO
HO
F
F
N
N
O
O
6.1
6.1
5.9
5.0
NDa
NDa
5.4
18
18
2
<10/12
N
*
F
F
5.3
NDa
N
HO
*
*
*
N
N
NDa
N
N
N
<4.5
N
*
N
N
N
19
4.6
<4.5
NDa
1.67
306
NDa
N
O
*
*
*
*
N
N
N
NDa
1.67
396
NDa
N
N
20
5.5
<4.5
O
N
21
5.4
<4.5
NDa
3.08
393
NDa
a
ND: not determined.
selectivity against this subtype is an absolute requirement for the
progression of a compound.10,11 Moreover, 1 showed moderate
hERG activity, as measured in a whole-cell voltage-clamp electro-
physiology assay.12 Compound 1 displayed poor solubility and
low metabolic stability. In contrast, 2 exhibited medium solubility
and improved metabolic stability, but was slightly less potent in

Table 2
SAR of chromanes with diazine as R1 substituent
O
O
R1
R1
NaV1.7 pIC50
NaV1.5 pIC50
hERG pIC50
c Log P
Solubility (
l
M)
RLM/HLM clint (ll/min/lg) 22
R2
N
H
R1
*
*
F
F
F
22
7.2
5.4
5.2
3.24
23
38/318
N
N
O
O
N
N
N
N
*
*
*
*
F
F
23
24
7.1
7.1
5.2
5.4
5.1
4.9
4.20
4.18
<1
<10/<10
<10/<10
F
O
*
F
F
F
F
N
N
O
3
N
N
N
N
O
*
F
F
O
25
26
27
28
29
6.6
7.0
6.9
7.1
7.1
5.0.
5.3
4.8
3.06
3.76
4.41
3.97
3.27
145
6.5
<1
<10/<10
<10/<10
14/14
O
*
*
*
F
F
5.0
N
N
O
O
N
N
N
N
F
F
*
F
F
<4.6
<5.5
4.9
<4.5
<4.5
4.9
O
*
*
*
N
N
F
F
<1
<10/16
<10/<10
N
N
O
N
N
F
*
F
F
F
O
34
O
(continued on next page)

5622
I. Kers et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5618–5624
blocking NaV1.7 and did not show selectivity against the NaV1.5
channel. Chromanes with basic substituents are reported to block
5-HT receptors and, not surprisingly, both compounds were proven
to be potent antagonist of the 5-HT1A and 5-HT1B receptors.13–15
The early findings mentioned above have prompted us to con-
duct further investigations. First, we probed the effect of lowering
the lipophilicity on the NaV1.7 potency by introducing more polar
acyl groups than those represented in 1 and 2. Therefore the phe-
nyl ring was replaced with a pyridine ring (3 and 4, Table 1) which
yielded less lipophilic, consequently more soluble, compounds that
retained the moderate NaV1.7 potency (cf. 1). In case of 5 a phenyl
substituted triazole ring was tried as bioisosteric acyl group. This
modification also proved to be successful since compound 5 exhib-
ited increased potency, demonstrated excellent solubility and high
metabolic stability. When methyl groups were introduced on the
phenyl ring in 6, a more potent NaV1.7 blocker was obtained, how-
ever the NaV1.5 activity was also increased and the solubility dra-
matically decreased.
In general compound 5 exhibited a good overall profile, but
unfortunately potency on the 5-HT receptors was still high which
confirmed that this undesired affinity was caused by the presence
of a basic piperazino moiety. We reasoned that by decreasing the
basicity of the target molecules the potential 5-HT liability could
be eliminated. Thus, we focused our attention on basic heterocyclic
rings to find adequate replacements for the piperazino substituent.
Compounds 7–9 with isomeric pyridines as a 5-substituent were
prepared and we found that 2- and 3-pyridyls (7 and 8) were equi-
potent with the 5-methylpiperazinyl analogue (cf. 2) while the 4-
pyridyl 9 exhibited markedly higher NaV1.7 potency. However,
these highly lipophilic compounds (7–9) were poorly soluble.
Therefore we decided to address this issue by combining the two
above mentioned successful modifications, the introduction of pyr-
idine rings at both C-5 and in the acyl moiety. Indeed, compounds
10 and 11 showed not only high potency and improved selectivity
versus NaV1.5 but were more soluble as well. Unfortunately, those
gains were accompanied by low metabolic stability. We believed
that unsubstituted positions of the pyridine ring potentially were
affected in the metabolic process and decided to introduce substit-
uents at both meta and para positions of the pyridine ring. We were
pleased to see that the metabolic stability of compound 12 signif-
icantly improved, unfortunately, potency and solubility were im-
pacted in an undesirable way.
Since good metabolic stability could be combined with the
desired structural feature of a substituted pyridine as a substituent
on the chromane ring, we continued our studies with the introduc-
tion of the polar hydroxymethyl group onto the pyridine ring (13
and 14). The 3-pyridyl isomer (13) displayed higher solubility and
was markedly more potent than the 4-pyridyl 14, while they were
equipotent on the NaV1.5 channel. In addition, both 13 and 14
exhibited excellent metabolic stability and, more importantly, the
5-HT activity was absent. Even when a longer alkoxy chain was
introduced on the acyl fragment as in case of 15 the good potency,
subtype selectivity, metabolic stability and solubility were still re-
tained, cf. 13. However, further substitution at the 5-pyridyl group,
both branching in the substituent (16) or disubstitution (17) proved
to be unfavorable for potency and solubility.
In parallel to the development of the dipyridyl chromane
amides we investigated a subclass of compounds with pyridine
as 5-substituent and triazole as a core group in the acyl part of
the molecule (18–21). Theses analogues of 5 with weakly basic
C-5 substituents, in contrast to dipyridine sub-series (like 11),
showed surprisingly low potency against NaV1.7. In addition, the
potency on the NaV1.5 channel was also low.
As a result of the studies described above we considered dipyr-
idyl chromane amide 13
a promising candidate for further
characterization based on the good overall profile of the compound

I. Kers et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5618–5624
5623
O
O
O
O
Ph
Ph
O
iv, v
O
i, ii, iii
vi
Ar-B(OH)2
C
+
N
H
F
+
N
F
F
NH2
HO
Ar
NH2
O
S
O
Ar
O
E
O
F
O
F
D
A
N
B
8
F
iv, ix
O
O
O
O
ii, vii, iii
viii
Ar-X
H
N
H
O
+
N
H
O
O
B
O
O
O
F
S
O
F
F
G
F
Scheme 1. Reagents and conditions: (i) Benzylbromide, K2CO3, CH2Cl2; (ii) BBr3, CH2Cl2, À78 °C; (iii) trifluoromethanesulfonic anhydride, NEt3, CH2Cl2, 0 °C; (iv) PdCl2.dppf,
2 M K2CO3, DMF, heating; (v) 10% Pd/C, ammonium formate, EtOH, heating; (vi) HBTU, NEt3, DMF; (vii) di-tert-butyl dicarbonate, NEt3, CH2Cl2, 0 °C; (viii)
bis(pinacolato)diboron, PdCl2Ádppf, KOAc, dioxane, heating; (ix) TFA, CH2Cl2.
Table 3
Ar: phenyl
Rat in vivo PK for compounds 13 and 29
O
O
Compound
13
0.40
11
3.8
42.2
0.27
0.38
1.5
3.5
29
0.6
4.2
2.2
25
0.3
0.30
2.5
4.8
Ph-triazole
pyridine
AUC/dosea (h⁄kg/L)
N
H
Ar
R2
Vss (L/kg)
R1
a
a
t
(h)
½
CLa (mL/min/kg)
AUC/doseb (h⁄kg/L)
b
R1: Me-piperazine
R2: alkoxy
Cmax
(
lmol/L)
b
tmax (h)
b
t
½
(h)
pyridine
Fb (%)
66.3
44
trifluoroalkoxy
a
Intravenous (iv), dose 3
l
mol/kg.
pyrimidine
pyrazine
b
trifluoroalkoxymethyl
Per oral (po), dose 10
lmol/kg.
(vide infra). However, we were still interested to see how the pyr-
idine ring replacement with other heteroaryl groups at the 5-posi-
tion effects the SAR. The data of the synthesised compounds is
summarized in Table 2.
First, an unsubstituted pyrimidine ring was introduced in 22
which showed as high NaV1.7 blocking activity and poor metabolic
stability as 10. The introduction of a methoxy substituent on the
4-position of the pyrimidine ring (23 and 24) led to retained good
NaV1.7 potency and successfully improved metabolic stability.
Unfortunately, the solubility decreased substantially. On the posi-
tive note, compound 25 exhibited a markedly improved solubility
while the lower lipophilicity was accompanied by a slight decrease
Figure 3. SAR of amido chromanes.
of potency (cf. 24). As was observed for methoxy pyrimidine 23 the
metabolism could also be retarded by introduction of a methyl
group on the pyrimidine ring (26) but, again, this modification
was detrimental for solubility.
We have also introduced 4-methoxy pyrazine (27) as aryl
substituent on the chromane ring. This compound was a potent
blocker of the NaV1.7 channel and exhibited good selectivity versus
NaV1.5 but was poorly soluble. Replacement of the 4-methoxy
group with a methyl moiety in 28 also afforded a potent but poorly
soluble compound (cf. 26). On the positive note both 29 and 30
proved to be more soluble (cf. 27 and 28). Unfortunately, only 29
retained the high NaV1.7 potency and good selectivity over NaV1.5.
The stereochemistry of the amido group seemed to be very
important to achieve high potency in the series. In order to verify
this significance the corresponding R-enantiomer of 29, compound
31, was also prepared. We have found that the R-enantiomer did
not exhibit NaV1.7 channel blocking activity in the measured con-
centration range.
The general synthesis of amido chromanes is outlined in
Scheme 1. The starting materials were either commercially avail-
able or could readily be prepared according to published meth-
ods.16–18 Aminochromane A was benzyl protected and then the
methyl group was removed to furnish a phenolic intermediate
which was transformed to B by reaction with trifluoromethanesul-
fonic anhydride. Thereafter B was subjected to Suzuki reaction
with the corresponding aryl boronic acid C followed by deprotec-
tion to give aminochromane D. The final product, represented by
8, was obtained by coupling D with the appropriate acid E.
125
100
75
50
25
0
10000
1000
100
phase I
Cplasma
*
*
ns
16
10
vehicle
49
99
Dose (µmol/kg)
Figure 2. Dose–response effect of 29 in phase 1 of the rat formalin model after p.o.
administration. The effect (histogram) is expressed as the percentage in comparison
to vehicle treated group and total plasma concentration (line) is expressed as
mean SD, n = 9 per group). One Way ANOVA was used as statistic in comparison to
vehicle group per phase, followed by unpaired one-tailed t-test.⁄p <0.05.

5624
I. Kers et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5618–5624
The commercial availability of heteroaryl boronic acids or esters
A. Supplementary data
(C) is limited and therefore we devised an alternative route to D
which allowed the use of heteroaryl halides as coupling partners
in the Suzuki reaction. The methyl group of A was removed and
the resulting phenolic intermediate was converted to F in a one-
pot procedure where the amino group was BOC protected followed
by introduction of the triflate moiety. Thereafter F was converted
in a palladium promoted reaction to boronic ester G which after
a Suzuki reaction with aryl halide H and subsequent deprotection
provided aminochromane D.
Compounds 13 and 29 presented attractive overall profiles in
terms of high NaV1.7 potency and selectivity versus NaV1.5 and
hERG, low lipophilicity, good solubility and high in vitro metabolic
stability. A more comprehensive in vitro profiling, in enzyme and
radioligand binding assays, of 13 and 29 was conducted on a panel
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2012.06.
105.
References and notes
1. Sulayman, D. D. H.; Cummins, T. R.; Black, J. A.; Waxman, S. G. Annu. Rev.
Neurosci. 2010, 33, 325.
2. Chahine, M.; Chatelier, A.; Babich, O.; Krupp, J. J. CNS Neurol. Disord. - Drug Targ.
2008, 7, 144.
3. Cox, J. J.; Reimann, F.; Nicholas, A. K.; Thornton, G.; Roberts, E.; Springell, K.;
Karbani, G.; Jafri, H.; Mannan, J.; Raashid, Y.; Al Gazali, L.; Hamamy, H.; Valente,
E. M.; Gorman, S.; Williams, R.; Mchale, D. P.; Wood, J. N.; Gribble, F. M.;
Woods, C. G. Nature 2006, 444, 894.
4. Ahmad, S.; Dahllund, L.; Eriksson, A. B.; Hellgren, D.; Karlsson, U.; Lund, P-E.;
Meijer, I. A.; Meury, L.; Mills, T.; Moody, A.; Morinville, A.; Morten, J.; O’Donnell,
D.; Raynoschek, C.; Salter, H.; Rouleau, G. A.; Krupp, J. J. Hum. Mol. Genet. 2007,
16, 2114.
5. Yang, Y.; Wang, Y.; Li, S.; Xu, Z.; Li, H.; Ma, L.; Fan, J.; Bu, D.; Liu, B.; Fan, Z.; Wu,
G.; Jin, J.; Ding, B.; Zhu, X.; Shen, Y. J. Med. Genet. 2004, 41, 171.
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2010, 20, 755.
7. Trivedi, S.; Dekermendjian, K.; Julien, R.; Huang, J.; Lund, P. E.; Krupp, J.;
Kronqvist, R.; Larsson, O.; Bostwick, R. Assay Drug Dev. Technol. 2008, 6, 167.
8. Harmer, A. R.; Abi-Gerges, N.; Easter, A.; Woods, A.; Lawrence, C. L.; Small, B. G.;
Valentin, J.-P.; Pollard, C. E. J. Pharm. Tox Methods 2008, 57, 30.
of 98 different targets at MDS pharma. At 10
l
M concentration
2B receptor
compound 13 showed 55% inhibition at the Adrenergic
a
with [3H] Rauwolscine as radioligand, 80% inhibition at the Dopa-
mine Transporter (DAT) with [125I] RTI-55 as radioligand and 98%
inhibition of [125I] Ghrelin at the Growth Hormone Secretagogue
(GHS) receptor. Subsequently, IC50 values for 13 were determined
to 2 lM for DAT and 0.2 lM for the GHS receptor. At 10 lM com-
pound 29 showed 66% inhibition at the Adenosine Transporter
(AT) with [3H] Nitrobenzylthioinosine as radioligand, 55% inhibi-
tion at the Cannabinoid B1 (CB1) receptor with [3H] SR141716A
as radioligand and 127% increased binding of [125I] Macrophage
9. NaV1.7 currents were recorded from HEK293cells stably expressing the
a-
subunit of the human channel (Millipore) with the perforated whole-cell
configuration using IonWorksTM Quattro planar patch clamp automated
electrophysiology system (Molecular Devices, Inc.). The external recording
solution (D-PBS, Gibco) contained (in mM) NaCl (138), KCl (2.7), KH2PO4 (1.5),
Na2HPO4 (8), CaCl2Á2H2O (0.9) and MgCl2Á6H2O (0.5) and glucose (5.5). The
internal recording solution contained (in mM) K-gluconate (100), KCl (40),
MgCl2 (3), EGTA (3) and HEPES (5). KOH was used adjust pH to 7.25, and the
final osmolarity was set at 290 mOsm. Amphotericin B was used at a final
Inflammatory Protein-1
1 (CCR1). The IC50 values for 29 were determined to 1.8
and 5 M for the CB1 receptor. Importantly, compound 29 was
inactive when analysed for agonistic properties at the CB1 receptor
in a GTP[
35S incorporation assay. In addition, both compounds
a
(MIP-1
a
to the CC Chemokine Receptor
l
M for AT
l
concentration of 150 lg/ml. A steady-state protocol was used where the cells
c
]
were clamped to À65 mV and the sodium currents were evoked by a voltage
train consisting of eight 30 ms depolarizing steps to À20 mV, at a frequency of
3 Hz. In order to recover a fraction of the channels from slow inactivation a
20 ms hyperpolarizing step to À100 mV was executed prior to the activation
step. The fraction of inactivated channels in the assay was estimated to be
40À50%. The protocol was activated twice, pre-scan and post-scan compound
addition and the degree of inhibition for each well was assessed for the eight
pulse. Half log serial dilutions of the compounds were prepared in DMSO, with
a concentration in the external recording solution of 0.3%.
were inactive in the 5HT1A and 5-HT1B assays.
Rat in vivo pharmacokinetics (PK) measurements were per-
formed for 13 and 29 and the results are summarized in Table 3.19
The similar in vitro metabolic stability of 13 and 29 is reflected well
in their in vivo PK profile, particularly long half life and high oral bio-
availability. In vivo efficacy of 29 was studied in the rat formalin
model, which is a peripherally driven model with components of
central sensitization.20–22 As shown in Figure 2, the compound dis-
played a dose dependent antinociceptive effect in the phase 1 of
the formalin test. A statistically significant antinociceptive effect
10. Goldin, A. L. Annu. Rev. Physiol. 2001, 63, 871.
11. Tfelt-Hansen, J.; Winkel, B. G.; Grunnet, M.; Jespersen, T. J. Cardiov.
Electrophysiol. 2010, 21, 107.
12. Bridgland-Taylor, M. H.; Hargreaves, A. C.; Easter, A.; Orme, A.; Henthorn, D. C.;
Ding, M.; Davis, A. M.; Small, B. G.; Heapy, C. G.; Abi-Gerges, N.; Persson, F.;
Jacobson, I.; Sullivan, M.; Albertson, N.; Hammond, T. G.; Sullivan, E.; Valentin,
J. P.; Pollard, C. E. J. Pharm. Tox Methods 2006, 54, 189.
13. Berg, S.; Linderberg, M.; Ross, S.; Thorberg, S-O.; Ulff, B. WO 9914213, 1999;
PCT Int. Appl.,
of 66% was detected at a dose of 49
lmol/kg, corresponding to a total
plasma concentration of 5 M. No significant antinociceptive ef-
1
l
fects were seen in phase 2 (data not shown).
In summary, we established the structure-activity relationship
in the 5-heteroaryl 3-amido chromane class of NaV1.7 blockers,
see Figure 3 for summary of key-steps in optimization process.
We started from the moderately potent but poorly soluble and
metabolically unstable methylpiperazines (1–6) which also pos-
sessed 5-HT activity. We have shown that the combination of the
less basic pyridine (7–21) and diazine rings (22–30) on the chro-
mane ring with alkoxy pyridine acyl group could give more potent
and subtype selective compounds which neither showed activity
on the 5-HT1A or 5HT1B receptors, nor on the hERG channel. Com-
pounds 13 and 29 showed the best overall in vitro profile, that
translated well to rat in vivo PK. Furthermore, compound 29
showed significantly dose-dependent efficacy in the phase 1 of
the formalin model of pain, whereas no effects were seen in phase
2.
14. Preparation of compounds 1 and 2: Berg, S.; Nylöf, M.; Ross, S.; Thorberg, S-O.
WO 9914212 A1 19990325, 1999. PCT Int. Appl.
15. Ahlgren, C.; Eriksson, A.; Tellefors, P.; Ross, S. B.; Stenfors, C.; Malmberg, Å. Eur.
J. Pharmacol. 2004, 499, 67.
16. Preparation of compounds 7–13, 15, 18, 20–26: Besidski, Y.; Kers, I.; Nylöf, M.;
Sandberg, L.; Skogholm, K. WO2008130320, 2008, PCT Int. Appl.
17. Preparation of compounds 5 and 6: Besidski, Y.; Kers, I.; Macsari, I.; Nylöf, M.;
Rotticci, D. WO2008130321, 2008, PCT Int. Appl.
18. Preparation of compound 29: Aurell, C-J.; Besidski, Y.; Kers, I.; Nylöf, M.
WO2012039657, 2012; PCT Int. Appl.
19. Formulation of compound 13 for both iv and po studies: 5% dimethylamine
(DMA), 95% hydroxypropyl-b-cyclodextrine (HPbCD) (200 mg/ml). In case of
29 3% DMA, 10% HPbCD (100 mg/ml), 2.35% glycerol were used for iv studies
and 5% DMA, 10% HPbCD (100 mg/ml), 2.35% glycerol for po studies. In all cases
fasted, Sprague–Dawley, male rats were used, Three animals/administration/
compound.
20. The formalin test was performed by injecting 100 lL of 2.0% formalin
subcutaneously on the dorsal side of the left hind paw of Sprague Dawley
rats (n = 9 per group). Three hours prior to the formalin injection, compound
29, at doses 0, 19, 49 and 99 lmol/kg, was administered per oral gavage. The
behavior of the animals was recorded for 35 minutes after formalin injection
and time spent to licking the injected paw was analyzed to represent
nociceptive behavior. The response to formalin injection is biphasic; phase 1
(0–5 min after formalin injection) and phase 2 (15–35 min after formalin
injection). Formulation: nanosuspension done of 1% PVP K30 and 0.2% SDS.
21. Gustafsson, H.; Sandin, J. Eur. J. Pharmacol. 2009, 605, 103.
Acknowledgments
The authors wish to thank colleagues at Physical Chemistry
Characterization Team for providing solubility data, and the Safety
Screening Centre for providing NaV1.5 and hERG data. In addition,
Dr. Alexander Minidis is acknowledged for fruitful discussions.
22. Tjolsen, A.; Berge, O. G.; Hunskaar, S.; Rosland, J. H.; Hole, K. Pain 1992, 51, 5.