Discovery and structure-activity relationship of imidazolinylindole derivatives as kallikrein 7 inhibitors

Article abstract of DOI:10.1016/j.bmcl.2018.11.011

A series of imidazolinylindole derivatives were discovered as novel kallikrein 7 (KLK7, stratum corneum chymotryptic enzyme) inhibitors. Structure-activity relationship (SAR) studies led to the identification of potent human KLK7 inhibitors. By further modification of the benzenesulfonyl moiety to overcome species differences in inhibitory activity, potent inhibitors against both human and mouse KLK7 were identified. Furthermore, the complex structure of 25 with mouse KLK7 could explain the SAR and the cause of the species differences in inhibitory activity.

Full text of DOI:10.1016/j.bmcl.2018.11.011

Accepted Manuscript
Discovery and structure-activity relationship of imidazolinylindole derivatives
as kallikrein 7 inhibitors
Hidenobu Murafuji, Tsuyoshi Muto, Megumi Goto, Seiichi Imajo, Hajime
Sugawara, Yoshiaki Oyama, Yutaka Minamitsuji, Shuji Miyazaki, Kenichi
Murai, Hiromichi Fujioka
PII:
S0960-894X(18)30865-5
https://doi.org/10.1016/j.bmcl.2018.11.011
BMCL 26122
DOI:
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
27 August 2018
29 October 2018
6 November 2018
Please cite this article as: Murafuji, H., Muto, T., Goto, M., Imajo, S., Sugawara, H., Oyama, Y., Minamitsuji, Y.,
Miyazaki, S., Murai, K., Fujioka, H., Discovery and structure-activity relationship of imidazolinylindole derivatives
as kallikrein 7 inhibitors, Bioorganic & Medicinal Chemistry Letters (2018), doi: https://doi.org/10.1016/j.bmcl.
2018.11.011
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Bioorganic & Medicinal Chemistry Letters
Discovery and structure-activity relationship of imidazolinylindole derivatives as
kallikrein 7 inhibitors
Hidenobu Murafujia, c, Tsuyoshi Mutoa, c,, Megumi Gotoa, c, Seiichi Imajoa, Hajime Sugawaraa, c, Yoshiaki
Oyamaa, d, Yutaka Minamitsujib, Shuji Miyazakib, Kenichi Muraib, Hiromichi Fujiokab
aAsubio Pharma Co., Ltd, 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe 650-0047, Japan
bGraduate School of Pharmaceutical Sciences, Osaka University, Yamada-oka 1-6, Suita, Osaka 565-0871, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
Revised
Accepted
Available online
A series of imidazolinylindole derivatives were discovered as novel kallikrein 7 (KLK7,
stratum corneum chymotryptic enzyme) inhibitors. Structure-activity relationship (SAR)
studies led to the identification of potent human KLK7 inhibitors. By further modification of
the benzenesulfonyl moiety to overcome species differences in inhibitory activity, potent
inhibitors against both human and mouse KLK7 were identified. Furthermore, the complex
structure of 25 with mouse KLK7 could explain the SAR and the cause of the species
differences in inhibitory activity.
Keywords:
Kallikrein 7
2009 Elsevier Ltd. All rights reserved.
inhibitor
Imidazolinylindole
X-ray co-crystal structure
———
Corresponding author.
E-mail address: muto.tsuyoshi.zu@daiichisankyo.co.jp (T. Muto)
cPresent address: Shinagawa R&D Center, Daiichi-Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
dPresent address: Shinagawa R&D Center, Daiichi-Sankyo RD Novare Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan

Human tissue kallikreins (KLKs) are a family of 15 related
serine proteases encoded by the genes KLK1–KLK15, which are
colocalized in a cluster on chromosome 19q13.3–q13.4.1 KLKs
have been implicated in a wide range of physiological and
pathological processes and are attractive drug targets.2,3 In the
skin, some KLKs are associated with skin homeostasis, including
KLK7 (stratum corneum chymotryptic enzyme), which plays an
important role in epidermal desquamation by degrading
corneodesmosome proteins.4-6 In normal epidermis, the activities
of proteases are regulated by their intrinsic inhibitors, which
include lympho-epithelial Kazal-type-related inhibitor (LEKTI).7
However, enhanced protease activity in the epidermis may
disturb skin barrier homeostasis and induce epithelial
dysfunction, leading to enhanced moisture loss and penetration of
microbes and allergens.8 Therefore, skin KLKs, including KLK7,
are potential targets for the treatment of inflammatory skin
diseases related to epithelial dysfunction, such as atopic
dermatitis, psoriasis, and Netherton’s syndrome.
imidazodiazepinone derivatives,12 1,2,4-triazole derivatives,13
and coumarin-3-carboxylate derivatives,14 have been reported,
but most of these have demonstrated low selectivity and
moderate activity upon in vivo evaluation. Recently, we reported
1,3,6-trisubstituted 1,4-diazepan-7-ones (Figure 1), such as
compound 1a, as novel, potent, and selective human KLK7
inhibitors.15,16 Optimization to overcome species differences in
inhibitory potency led to the representative compound 1b, which
showed potent inhibitory activity against both human and mouse
KLK7.17 In parallel with this optimization work, we continued
our efforts to find other scaffolds for KLK7 inhibitors. As a part
of this search, we carried out screening of a compound collection
composed of the intermediates from the synthesis of natural
products owned by the graduate school of Osaka University. As a
result, imidazolinylindole derivative 2 was identified as a hit
compound. Compound 2 showed only weak inhibitory activity
against human KLK7, but its lower molecular weight made it an
attractive candidate for further optimization. Herein, we report
our structure-activity relationship (SAR) study of this scaffold.
We obtained potent KLK7 inhibitors with no species differences.
Furthermore, X-ray crystal structural analysis for a complex of
mouse KLK7 and the representative compound is presented.
Several non-peptide KLK7 inhibitors, including natural
isocoumarins,9
isomannide
derivatives,10
5-amino-2-
mercaptobenzimidazolyl quinazolinone derivatives,11 pyrido-
Figure 1. Chemical structures of reported KLK7 inhibitors 1 and hit compound 2. The stereochemistry of 1b was tentatively
determined by structure-activity relationship studies.17
The imidazolinylindole derivatives listed in Tables 1 and 2
were prepared from commercially available 3a, c, and d (Scheme
1). N-sulfonylation and subsequent Wittig reaction gave olefins
5a-d. Dihydroxylation of 5a-d using K2OsO4·2H2O and N-
methylmorpholine, followed by Mitsunobu reaction with
diphenylphosphoryl azide, afforded diazides 7a-d, which were
reduced by triphenylphosphine to give precursor diamines 8a-d.
Imidazolines 2, 11, and 12, in which R3 was not a methyl group,
were prepared in a one-pot operation from diamine 8a and the
corresponding aldehydes via oxidation of aminal intermediates
by N-bromosuccinimide.18 In the case of R3 = Me, imidazoline
ring formation was carried out using ethyl acetimidate to give
compounds 10, 13, 17, and 18. N-methylation of the imidazoline
part of 13 gave compound 19. Other derivatives were synthesized
from compounds 9a and 9b, which were prepared from
compounds 13 and 17 by Boc protection of the imidazoline part
and subsequent de-sulfonylation. Introduction of
a
4-
chlorobenzyl group to compound 9a and subsequent deprotection
gave compound 15. Compounds 14, 16, and 20–28 were prepared
from compound 9b by sulfonylation and deprotection.

Scheme 1. Reagents and conditions: (a) NaH, 4-R3-PhSO2Cl, THF, 0 °C; (b) n-BuLi, Ph3PCH3Br, THF, rt; (c) K2OsO4·2H2O, N-
methylmorpholine, THF, H2O, rt; (d) diethyl azodicarboxylate, PPh3, diphenylphosphoryl azide, toluene, rt; (e) PPh3, toluene, reflux,
then H2O, rt; (f) R3-CHO, N-bromosuccinimide, CH2Cl2, rt; (g) ethyl acetimidate, EtOH, rt; (h) n-BuLi, MeI, THF, rt; (i) Boc2O, Et3N,
THF, rt; (j) n-Bu4NF, THF, reflux; (k) NaH, 4-Cl-PhCH2Cl, THF, 0 °C; (l) TFA, CH2Cl2, 0 °C; (m) t-BuOK, Ar-SO2Cl, THF, 0 °C.
The results of the initial SAR study on imidazolinylindole
derivatives for human KLK7 inhibitory activity are shown in
Table 1. First, we focused on the modification of the
characteristic imidazoline part (compounds 2, 10–12). For the R3
substituent, the inhibitory activity decreased as the size was
increased, and compound 10 (with the methyl substituent)
showed the most potent inhibitory activity. Replacement of the 4-
methylbenzenesulfonyl group of compound 10 with a 4-
chlorobenzenesulfonyl group further increased the inhibitory
activity (13), but 3-chloro derivative 14 showed decreased
activity. 4-Chlorobenzyl derivative 15 was also less potent than
compound 13. Given that the activity disappeared for the
methanesulfonyl derivative 16, coupled with the fact that KLK7
is a chymotryptic protease that preferentially cleaves the C-
terminal peptide bonds of aromatic amino acids such as Phe and
Tyr, we predicted that the benzenesulfonyl group would interact
with the S1 site (which is the primary substrate specificity
pocket) of human KLK7. Previously, we reported the crystal
structure of compound 1a bound to human KLK7, and confirmed
that the 5-chloro-2-methoxybenzyl group is placed in the S1 site
of KLK7, while the chlorine atom is located in the deep site of
the S1 pocket (PDB ID: 5Y9L).15 Even in the case of compound
13, the chlorine atom would be located in a similar position as
that of 1a. With the 4-chlorobenzenesulfonyl group at the 1-
position of the indole ring, the introduction of a methyl (17) or
bromo (18) substituent at the 5-position (R1) resulted in a further
increase in the inhibitory activity. N-methylation of the
imidazoline ring (19) markedly diminished the activity.

Table 1. Inhibitory activity of initial screening hit and related compounds against human KLK7.a
Compound
R1
H
R3
iso-Pr
Me
A
X
R4
H
IC50 (M)
70
2
4-Me-Ph
4-Me-Ph
4-Me-Ph
4-Me-Ph
4-Cl-Ph
3-Cl-Ph
4-Cl-Ph
Me
SO2
SO2
SO2
SO2
SO2
SO2
CH2
SO2
SO2
SO2
SO2
10
11
12
13
14
15
16
17
18
19
H
H
10
H
Et
H
24
H
cyclohexyl
Me
H
>100
5.7
H
H
H
Me
H
>30
22
H
Me
H
H
Me
H
>100
1.9
Me
Br
H
Me
4-Cl-Ph
4-Cl-Ph
4-Cl-Ph
H
Me
H
4.7
Me
Me
>30
a: Detailed assay conditions are described in the supplementary content.
With a more potent human KLK7 inhibitor in hand, we
examined the inhibitory activity against mouse KLK7 (Table 2),
because there were species differences between human and
mouse KLK7 inhibitory activity for previously reported
inhibitors, such as compound 1a.17 Unfortunately, none of the
compounds listed in Table 2 showed potent inhibitory activity
against mouse KLK7 even at 100 M concentration, and only
compound 14, with a 3-chlorosulfonyl group at the 1-position,
exhibited weak activity. It has been reported that the differences
between human and mouse KLK7 inhibitory activity can be
attributed to a structural difference in the S1 pocket, derived from
a single amino acid difference (Ala190 for human KLK7 and
Thr190 for mouse KLK7).17 Furthermore, we demonstrated that
modification of the P1 part of inhibitors―that is, the moiety
interacting with the S1 pocket―could overcome the species
differences and lead to compound 1b. Similar to the previous
example, we next focused on varying the benzenesulfonyl
moiety, the supposed P1 part of this series, to overcome the
species differences (Table 3).
Table 2. Species differences in KLK7 inhibition.a
human KLK7
mouse KLK7
Compound
% inhibition @
IC50 (M)
10
100M
10
13
14
17
18
14
17
77
33
35
5.7
>30
1.9
4.7
a: Detailed assay conditions are described in the supplementary content.

De-chlorination of compound 17 decreased human KLK7
inhibitory activity but led to equipotent inhibition of human and
mouse KLK7 (20). This result also implied that the
benzenesulfonyl moiety interacted with the S1 pocket of the
KLK7 enzyme. Isosteric replacement of the benzene ring with a
thiophene ring (21) also resulted in moderate inhibitory activity
against both human and mouse KLK7, but slightly increased the
species difference. Introduction of the smaller fluorine atom at
the 4-position of the benzene ring of 20 increased its inhibitory
activity toward human KLK7 but diminished the mouse KLK7
inhibitory activity (22), suggesting that substituents at the 4-
position are not tolerated for mouse KLK7 inhibition. Both 3-
chloro (23) and 2-chloro (24) derivatives improved mouse KLK7
inhibitory activity. In particular, the 2-chloro derivative 24
exhibited potent inhibition against both human and mouse KLK7.
Given these promising results, we further examined the
substituents at the 2-position of the benzene ring. Each
compound (25–28) showed almost equipotent inhibition of
human and mouse KLK7. The inhibitory activity generally
increased as the size of substituent increased, but the less
lipophilic cyano group (28) was associated with decreased
activity. These results suggested that the 2-substituents were
located in the previously reported lipophilic S1 sub-pocket17
composed of the main chain of Ser195 and the side chain of
Val213 (vide infra). However, in contrast to the case of 1b, the
disubstituted derivative 29 showed decreased inhibitory activity,
indicating that the binding mode in the S1 region is different
between the two inhibitors.
Table 3. Inhibitory activity of sulfonamide derivatives against human and mouse KLK7.a
Human KLK7
IC50 (M)
Mouse KLK7
IC50 (M)
Compound
A
17
20
21
22
23
24
25
26
27
28
29
4-Cl-Ph
Ph
1.9
17
>100
15
2-thienyl
4-F-Ph
11
22
9.4
30
>30
10
3-Cl-Ph
2-Cl-Ph
2-F-Ph
1.2
4.1
1.0
0.39
6.7
14
1.5
6.4
1.3
0.40
11
2-Me-Ph
2-Br-Ph
2-CN-Ph
2,6-diCl-Ph
10
a: Detailed assay conditions are described in the supplementary content.
To confirm the binding mode of this chemotype, we examined
the X-ray crystal structure of 2-chloro derivative 24 bound to
mouse KLK7 (Fig. 2, PDB ID: 6AHS). Compound 24 is a
racemate, but it has been suggested that the R enantiomer was
uniquely bound in this structure, as the methyl group of
imidazoline ring was assigned based on the electron density map
of the crystal structure. Therefore, the crystal structure analysis
was carried out with only this arrangement. Since no covalent
bond was observed between 24 and KLK7 in the complex
structure, it was considered that this series of compounds were
reversible and substrate-competitive inhibitors. 2-Chlorobenzene,
the P1 region of the inhibitor, inserts into the S1 pocket as
expected. The chlorine atom is located in the sub-pocket
composed of Ser195 and Val213 (Fig. 2B), but an empty space
can be observed between the chlorine atom and the surrounding
amino acids constructing the sub-pocket. The increase in the
inhibitory activity of 27 with the more bulky bromine atom may
be attributable to increased structural complementarity in this
region. The methyl group on the imidazoline ring is located at the
S2 site composed of side chains of His99, Asp102, His57, and
Ser214, and makes van der Waals contacts with the imidazole
ring of His99 and Asp102 side chain. This interaction could well
explain the SAR of the substituent at the 2-position of the
imidazoline ring: the potency decreased as the size was

increased. Furthermore, the methyl group on the indole ring
interacts with the imidazole ring of His99, which would
contribute to binding affinity. A hydrogen bond (2.72 Å) was
observed between the imidazoline NH and the main chain
carbonyl of Ser214. Such a hydrogen bond with the Ser214
carbonyl could also be observed in the other complex structures
of human KLK7 and its inhibitors, such as compound 1a
(PDB:5Y9L)15 and substrate-like peptidyl chloromethyl ketone
(PDB:2QXI),19 indicating the importance of this hydrogen bond
for inhibitor binding. N-methylation of the imidazoline NH
considerably decreased the inhibitory activity (13 vs. 19).
Figure 2. (A) Complex structure of 24 around the binding site of mouse KLK7 (PDB ID: 6AHS). The molecular surface of KLK7 is
represented by the gray mesh. The key amino acids are shown in stick form. The inhibitor 24 is shown as a ball-and-stick form (C: green, O:
red, N: blue, S: yellow, Cl: dark green). The red dotted line represents the hydrogen bond between Ser214 and inhibitor. (B) Enlarged view at
the S1 pocket. The molecular surface of the inhibitor 24 is indicated in translucent green. The water molecule that interacts with Thr190 is
represented by a red ball.
The bottom of the S1 pocket of mouse KLK7 was narrowed by
the side chain of Thr190 and a water molecule as compared with
the case of the human protein (Fig. 3). Considering the structure
shown in Fig. 3, the substituent at the 4-position of the
benzenesulfonyl group would cause steric hindrance against
inhibitor binding to mouse KLK7. This steric hindrance can be
considered as the cause of the species difference in the inhibitory
activity for compounds 10, 13, 17, and 18. Since amino acids
constructing S1 sub-pockets are highly conserved between
human and mouse KLK7, as already reported,17 it is quite likely
that compounds having a substituent at the 2-position but not the
4-position, such as 24, would have the same binding pose in
human KLK7. This prediction is supported by the fact that
almost all inhibitors without a 4-substituent shown in Table 3
exhibited equipotent inhibition for human and mouse KLK7.

Figure 3. Enlarged view at the S1 site with superimposition of the surface structures of mouse KLK7 with 24 and human KLK7 with 1a (PDB
ID: 5Y9L). The surface of each KLK7 is represented as colored mesh (gray for mouse and pink for human). The key amino acids are shown in
stick form, and the water molecule that interacts with Thr190 is represented by a red ball. Only inhibitor 24 bound for mouse KLK7 is shown as
a ball-and-stick model (C: green, O: red, N: blue, S: yellow, Cl: dark green).
In the comparison of compounds 1b and 24 in the X-ray
crystal structures of mouse KLK7 (Fig. 4), the benzene ring of
each inhibitor was observed to be in almost the same position in
the S1 pocket to avoid steric hindrance caused by the Thr190 side
chain and water molecule. On the other hand, the insertion
direction of the benzene ring into S1 site differed between the
two compounds. As a result, the position of the chlorine atom at
the ortho position of each inhibitor was slightly different,
although both interacted with the S1 sub-pocket and would
contribute to increasing potency. Furthermore, the carbon atom at
the other ortho position of 24 was located in nearly the same
position of the meta-carbon atom of 1b, and was in contact with
the main chain of Thr217. The introduction of a substituent at the
other ortho position of 24 would cause steric hindrance for
inhibitor binding.
These findings explain the result that the inhibitory activity of
the di-ortho substituted derivative 29 was decreased compared
with
that
of
24,
unlike
the
case
of
1b.

Figure 4. Enlarged view at S1 site with superimposition of X-ray crystal structures of mouse KLK7 and its inhibitors, 1b (PDB ID: KZFI) and
24 (PDB ID: xxxx). The molecular surface of the KLK7 is represented by a gray mesh. The key amino acids are shown in stick form, and the
water molecule that interacts with Thr190 is represented by a red ball. The inhibitors are shown in a ball-and-stick form (C: purple for 1b and
green for 24, O: red, N: blue, S: yellow, Cl: dark green).
In conclusion, imidazolinylindole derivative 2 was identified
as a novel KLK7 inhibitor via screening of a small compound
collection. The initial SAR study led to the identification of
potent human KLK7 inhibitors such as 17, but these showed
significantly decreased potency for mouse KLK7. To overcome
these species differences in inhibitory activity, the
benzenesulfonyl moiety was modified, and potent inhibitors
against both human and mouse KLK7, such as 27, were
eventually identified. X-ray crystal structure analysis of 24 bound
to mouse KLK7 revealed the structural basis of KLK7 inhibition,
and sufficiently explained the SAR for this series of inhibitors
and the cause of the species differences in inhibitory activity. The
inhibitors identified in this study, such as 27, have smaller
molecular weights than previously reported inhibitors and
showed potent inhibitory activity against mouse KLK7; hence,
they are expected to be useful tools for studying the
pathophysiological role of KLK7.
Acknowledgments
We are grateful to Dr. H. Annoura for his helpful support with this study.
Supplementary Material
Supplementary content associated with this article can be found, in the online version, at
References
1. Yousef GM, Diamandis EP. The new human tissue kallikrein gene family: structure, function, and association to disease. Endocr Rev. 2001;22(2):184–
204.
2. Prassas I, Eissa A, Poda G, Diamandis EP. Unleashing the therapeutic potential of human kallikrein-related serine proteases. Nat Rev Drug Discov.
2015;14(3):183–202.
3. Sotiropoulou G, Pampalakis G. Targeting the kallikrein-related peptidases for drug development. Trends Pharmacol Sci. 2012;33(12):623–634.
4. Caubet C, Jonca N, Brattsand M, et al. Degradation of corneodesmosome proteins by two serine proteases of the kallikrein family, SCTE/KLK5/hK5
and SCCE/KLK7/hK7. J Invest Dermatol. 2004;122(5):1235–1244.
5. Brattsand M, Stefansson K, Lundh C, Haasum Y, Egelrud T. A proteolytic cascade of kallikreins in the stratum corneum. J Invest Dermatol.
2005;124(1):198–203.
6. Borgono CA, Michael IP, Komatsu N, et al. A potential role for multiple tissue kallikrein serine proteases in epidermal desquamation. J Biol Chem.
2007;282(6):3640–3652.
7. Deraison C, Bonnart C, Lopez F, et al. LEKTI fragments specifically inhibit KLK5, KLK7, and KLK14 and control desquamation through a pH-
dependent interaction. Mol Biol Cell. 2007;18(9):3607–3619.
8. Cork MJ, Danby SG, Vasilopoulos Y, et al. Epidermal barrier dysfunction in atopic dermatitis. J Invest Dermatol. 2009;129(8):1892–1908.
9. Teixeira TS, Freitas RF, Abrahao O, Jr., et al. Biological evaluation and docking studies of natural isocoumarins as inhibitors for human kallikrein 5 and
7. Bioorg Med Chem Lett. 2011;21(20):6112.
10. Oliveira JP, Freitas RF, Melo LS, et al. Isomannide-based peptidomimetics as inhibitors for human tissue kallikreins 5 and 7. ACS Med Chem Lett.
2014;5(2):128–132.
11. Tan X, Bertonati C, Qin L, et al. Identification by in silico and in vitro screenings of small organic molecules acting as reversible inhibitors of
kallikreins. Eur J Med Chem. 2013;70:661–668.
12. Arama DP, Soualmia F, Lisowski V, et al. Pyrido-imidazodiazepinones as a new class of reversible inhibitors of human kallikrein 7. Eur J Med Chem.
2015;93:202–213.
13. Tan X, Furio L, Reboud-Ravaux M, Villoutreix BO, Hovnanian A, El Amri C. 1,2,4-Triazole derivatives as transient inactivators of kallikreins
involved in skin diseases. Bioorg Med Chem Lett. 2013;23(16):4547–4551.
14. Tan X, Soualmia F, Furio L, et al. Toward the first class of suicide inhibitors of kallikreins involved in skin diseases. J Med Chem. 2015;58(2):598–
612.
15. Murafuji H, Sakai H, et al. Discovery and structure-activity relationship study of 1,3,6-trisubstituted 1,4-diazepane-7-ones as novel human kallikrein 7
inhibitors. Bioorg. Med Chem Lett. 2017;27(23): 5272–5276.
16. Murafuji H, Sakai H, et al. Structure-based drug design of 1,3,6-trisubstituted 1,4-diazepane-7-ones as selective human kallikrein 7 inhibitors. Bioorg.
Med Chem Lett. 2018;28(8):1371–1375.
17. Murafuji H, Sugawara H, et al. Structure-based drug design to overcome species differences in kallikrein 7 inhibition of 1,3,6-trisubstituted 1,4-
diazepane-7-ones. Bioorg Med Chem. 2018;26(12):3639–3653.

18. Fujioka H, Murai K, et al. One-pot synthesis of imidazolines from aldehydes: detailed study about solvents and substrates. Tetrahedron
2007;63(3):638–643.
19. Debela, M, Hess, P, et al. Chymotryptic specificity determinants in the 1.0 Å structure of the zinc-inhibited human tissue kallikrein 7. Proc Natl Acad
Sci U. S. A. 2007;104(41):16086–16091.

Graphical Abstract
Discovery and structure-activity relationship
of imidazolinylindole derivatives as
kallikrein 7 inhibitors
Leave this area blank for abstract info.
Hidenobu Murafujia,c, Tsuyoshi Mutoa,c,, Megumi Gotoa,c, Seiichi Imajoa, Hajime Sugawaraa,c, Yoshiaki
Oyamaa,d, Yutaka Minamitsujib, Shuji Miyazakib, Kenichi Muraib, Hiromichi Fujiokab
a Asubio Pharma Co., Ltd., 6-4-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
b Graduate School of Pharmaceutical Sciences, Osaka University, Yamada-oka 1-6, Suita, Osaka 565-0871, Japan

Highlights
 Novel imidazolinylindole derivatives as KLK7
inhibitor are disclosed, and their SAR is
discussed.
 The position of substituent on the
benzenesulfonyl moiety strikingly affected the
inhibitory activity against mouse KLK7.
 X-ray crystal structure analysis of compound
24 bound to mouse KLK7 revealed the
structural basis of KLK7 inhibition.