Systematically Mitigating the p38α Activity of Triazole-based BET Inhibitors

Article abstract of DOI:10.1021/acsmedchemlett.9b00227

The Bromodomain and Extra Terminal (BET) family of proteins recognize post-translational N-?-acetylated lysine modifications, regulating transcription as "reader" proteins. Bromodomain inhibitors are interesting targets for the development of potential cancer, inflammation, and heart disease treatments. Several dual kinase-bromodomain inhibitors have been identified by screening kinase inhibitor libraries against BET proteins. Although potentially useful from a polypharmacology standpoint, multitarget binding complicates deciphering molecular mechanisms. This report describes a systematic approach to mitigating kinase activity in a dual kinase-bromodomain inhibitor based on a 1,2,3-triazole-pyrimidine core. By modifying the triazole substituent and altering the pyrimidine core, this structure-activity relationship study enhanced BET activity while reducing the p38α kinase activity >90,000-fold. A BRD4-D1 cocrystal structure indicates that the 1,2,3-triazole is acting as a N-?-acetylated lysine mimic. A BRD4 sensitive cell line, MM.1S, was used to demonstrate activity in cells, which is further supported by reduced c-Myc expression.

Full text of DOI:10.1021/acsmedchemlett.9b00227

Letter
pubs.acs.org/acsmedchemlett
Cite This: ACS Med. Chem. Lett. XXXX, XXX, XXX−XXX
Systematically Mitigating the p38α Activity of Triazole-based BET
Inhibitors
Angela S. Carlson,† Huarui Cui,† Anand Divakaran, Jorden A. Johnson, Ryan M. Brunner,
William C. K. Pomerantz,* and Joseph J. Topczewski*
Department of Chemistry, University of Minnesota Twin Cities, Minneapolis, Minnesota 55455, United States
S
* Supporting Information
ABSTRACT: The Bromodomain and Extra Terminal (BET)
family of proteins recognize post-translational N-ε-acetylated
lysine modifications, regulating transcription as “reader”
proteins. Bromodomain inhibitors are interesting targets for
the development of potential cancer, inflammation, and heart
disease treatments. Several dual kinase-bromodomain inhibitors
have been identified by screening kinase inhibitor libraries
against BET proteins. Although potentially useful from a
polypharmacology standpoint, multitarget binding complicates
deciphering molecular mechanisms. This report describes a
systematic approach to mitigating kinase activity in a dual kinase-bromodomain inhibitor based on a 1,2,3-triazole-pyrimidine
core. By modifying the triazole substituent and altering the pyrimidine core, this structure−activity relationship study enhanced
BET activity while reducing the p38α kinase activity >90,000-fold. A BRD4-D1 cocrystal structure indicates that the 1,2,3-
triazole is acting as a N-ε-acetylated lysine mimic. A BRD4 sensitive cell line, MM.1S, was used to demonstrate activity in cells,
which is further supported by reduced c-Myc expression.
KEYWORDS: Bromodomains, BET, BRD4, p38α, kinases
romodomains act as “readers” for epigenetic modifica-
Btions. Specifically, they bind N-ε-acetylated lysine residues
on histones and transcription factors through protein−protein
interactions to regulate cellular processes including the cell
cycle, cell proliferation, and cellular differentiation.1 The 61
human bromodomains, which are contained in 46 proteins,
have been subdivided into eight classes based on structural or
sequence similarities.2 The Bromodomain and Extra Terminal
(BET) proteins, which include BRD2, BRD3, BRD4, and
BRDT, all contain a similar domain architecture, including two
tandem bromodomains and an extra-terminal domain.
Inhibiting protein−protein interactions between BET
bromodomains and N-ε-acetylated lysine residues is a potential
method for treating BET related diseases, including cancer,
inflammation, and heart disease.2−5 For example, BRD4 can
recognize N-ε-acetylated K310 in the RelA subunit of NF-κB,
which is important for the activation of NF-κB, following
inflammatory signaling.6 Additionally, the bromodomains of
BRD4 can recognize N-ε-acetylated lysine residues on histones
and recruit transcription factors to superenhancer regions.
Inhibition of BRD4 at superenhancer regions can reduce c-
Myc expression, which could be a therapeutic strategy for
treating cancer.7 Given the significant roles that BET
bromodomains play in oncogene expression and inflammation,
19 clinical trials are underway to assess the therapeutic effects
of BET inhibition.
(Figure 1A).8−13 In 2014, both Ciceri et al. and Ember et al.
identified several dual kinase-bromodomain inhibitors includ-
ing BI-2536 (1), a PLK1 inhibitor with high affinity for BRD4-
D1.8,11 The dihydropteridinone carbonyl and the methylamino
group function as the N-ε-acetylated lysine mimic. CDK
inhibitor Dinaciclib (2) functions as a BRDT inhibitor.12 The
pyridine oxide serves as the N-ε-acetylated lysine mimic and is
recognized by N109 on BRDT. Although modest in BRDT
affinity, this molecule is of historical note, being the first dual
kinase-bromodomain inhibitor reported. Other p38-BET
inhibitors, including SB-202190 and SB-203580, were likewise
identified. Since these reports, developing bromodomain
inhibitors by kinase library screening has attracted more
attention.8,11,13,14 Urick et al. screened a library of 229 small
molecules by protein-observed fluorine NMR and subse-
quently developed a dual p38α-BET inhibitor named V
(3).13,15 While compounds 1 and 2 are pan-BET inhibitors,
compound 3 was shown to selectively inhibit the N-terminal
BET bromodomains with highest affinity for BRD4. Although
dual kinase-bromodomain inhibitors may produce synergistic
effects in some cases,9,11,14,16 selective inhibition is ideal for
understanding the physiological and pharmacological effect of
BET inhibition as well as minimizing potential side effects.17
Received: May 20, 2019
Accepted: August 2, 2019
Published: August 2, 2019
Several dual kinase-bromodomain inhibitors were discovered
by screening kinase inhibitor libraries against BRD4-D1
© XXXX American Chemical Society
A
DOI: 10.1021/acsmedchemlett.9b00227
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ACS Medicinal Chemistry Letters
Letter
C−H unit (pyridine), which would not be a suitable hydrogen
bond acceptor.
Given the significance of these two interactions, four
inhibitors were synthesized, each with one of the four possible
X/Y substitution combinations (Table 1). Switching from an
Table 1. Systematically Minimizing Binding to M109 in
p38α
a
compound
X
Y
p38α Kd (nM)
4
6
7
8
N
N
CH
CH
NH
O
NH
O
2.2 0.63
120 51
6500 6300
5000 6100
a
Kd values were determined by KINOMEscan. Data represents the
mean and standard error from two independent trials.
Figure 1. Dual kinase-bromodomain inhibitors.
exocyclic amine (4) to an ether (6) led to a ∼50-fold reduction
in p38α binding. A ∼1000-fold reduction in kinase binding was
observed when the analogous change was made to compound
1.17 When the pyrimidine was replaced with a pyridine (4 vs
7), the p38α affinity was reduced by a factor of ∼3,000. Thus,
in this scaffold, removing the pyrimidine nitrogen appears to
be more important to mitigating the p38α activity than
installing an ether linkage. This was supported by examining a
compound with both an ether linkage and a pyridine ring (8).
This compound displayed significantly diminished p38α
binding relative to the pyrimidine (6), but it was on a par
with the analog with the corresponding exocyclic nitrogen (7).
In addition to hydrogen bonding to M109, the p38α binding
affinity is likely enhanced by van der Waals interactions to the
4-fluorophenyl group in compounds 4 and 6−8. An analogous
p38α inhibitor, SB220025, demonstrates this interaction with
the 4-fluorophenyl ring residing in a hydrophobic pocket
between L104 and T106.20−22 A reduction in p38α activity was
observed when the 4-fluorophenyl group was replaced with an
ethyl group.23 Minimizing this van der Waals interaction would
likely further mitigate the p38α activity and produce a selective
BET inhibitor if bromodomain binding could be maintained.
Inhibitors containing a variety of alkyl chains were
synthesized to investigate this hypothesis (Scheme 1). The
sequence began with a CuAAC reaction,24 which afforded
triazole 11. The triazole could be directly coupled to an aryl
halide through a metalation/Negishi cross-coupling reaction.
The direct C−H arylation provided facile access to fully
substituted triazoles in a regiocontrolled manner. The resulting
product 13 could be deprotected to yield amine 14.
Subsequent guanidinylation (15) and deprotection afforded
inhibitors 19−22. The guanidine motif was added to increase
solubility at the highest concentrations assayed. The key
piperidyl amine (14) can be synthesized in three linear steps.
This allows much quicker access to a wide variety of analogs
relative to the 10-step route required for compound 3.15
The activity of these compounds was determined by
fluorescence anisotropy against BRD4-D1 (Table 2). The 4-
fluorophenyl containing compound (6) was a weak BRD4-D1
In our previous work, a trisubstituted 1,2,3-triazole-based
dual kinase-bromodomain inhibitor was reported (Figure 1b,
compound 4).15 The 1,2,3-triazole is known to engage BET
targets as an N-ε-acetylated lysine mimic.18 This study
describes the systematic removal of the p38α kinase activity
displayed by compound 4. A selective BET inhibitor is
reported (5), which is >15-fold more potent against BRD4-D1
and >90,000-fold less potent against p38α (>1,000,000-fold
̀
change in relative selectivity vis-a-vis compound 4). A BRD4-
D1 cocrystal structure and cellular data are provided that
further support the BET activity of the reported compounds.
This study began by studying how compounds like 4 bind
kinases. Cocrystal structures of p38α and similarly structured
hinge-binding kinase inhibitors provided hypotheses for a
systematic structure−activity relationship (SAR) study aimed
at mitigating p38α activity. Cocrystal structures with p38α
indicate that one of the inhibitor’s pyrimidine nitrogen atoms
serves as a hydrogen bond acceptor, and the exocyclic N−H is
a hydrogen bond donor (Figure 2); both interactions are made
to the M109 peptide backbone in p38α (Figure 2).19−21 If the
exocyclic N−H was replaced by an ether linkage, there would
no longer be a hydrogen bond donor, which would weaken
binding to p38α.21 Hypothetically, binding to M109 could be
further minimized by replacing the pyrimidine nitrogen with a
Figure 2. Hydrogen bonding interactions in p38α cocrystal structure
and proposed analogs.
B
DOI: 10.1021/acsmedchemlett.9b00227
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ACS Medicinal Chemistry Letters
Letter
determining the pyrimidine ring’s significance with regard to
BRD4-D1 binding. This seemed prudent given the findings on
p38α activity in Table 1. Based on a cocrystal structure of
BRD4-D1 and compound 3, the 3,5-dimethylphenyl ring
appears to provide an edge-to-face π−π interaction with W81,
and the pyrimidine ring interacts with the WPF shelf through a
nonspecific van der Waals interaction.15 This analysis indicated
that, unlike binding to p38α, neither nitrogen atom in the
pyrimidine ring provided a key binding interaction. Replacing
the pyrimidine ring (22) with a benzene ring (23) had
minimal impact on BRD4-D1 binding (Table 3), which is
Scheme 1. Synthesis of Inhibitors
Table 3. Effect of Nitrogen Atom(s) on BRD4-D1 Affinity
a
compound
N atom location
BRD4-D1 IC50 (μM)
22
23
5
24
25
26
1,2
none
1
2
3
4
9.7 1.8
12 1.1
3.6 0.05
97 2.6
>100
a
Compound 13d was synthesized through an alternate three-step
route with an overall yield of 35%. See SI for details.
Table 2. Significance of R Group to BRD4-D1 Binding
Affinity
>100
a
IC50 values were determined by fluorescence anisotropy. Data
represents the mean and standard deviation of three independent
trials.
consistent with this analysis. Comparing the pyrimidine to a
pyridine ring provided mixed results. Improved binding was
observed when the nitrogen atom was at the 1 position (5).
Placing a nitrogen atom at the 2 position was tolerated (24),
while placing the nitrogen atom at either the 3 (25) or 4 (26)
position resulted in complete loss of affinity. By comparison to
compound 22, the loss in affinity of compounds 25 and 26
may indicate an unfavorable interaction of the nitrogen lone
pair. The enhanced binding observed with compound 5 was
exciting in light of the diminished p38α binding observed with
the 2,6-disubstituted pyridine (7−8, Table 1).
The selectivity of compounds 5 and 27 was further
characterized (Table 4). The BRD4-D1 Kd of these two
compounds was determined by BROMOscan and was
consistent with the fluorescence anisotropy assay.25,26 The
methyl triazole demonstrated minimal selectivity for the two
domains in BRD4, which is consistent with other PAN-BET
inhibitors. Minimal binding to SMARCA2 and CBP was
observed (Table 4). SMARCA2 and CBP were selected as
representative non-BET family bromodomains. Prior work
with compound 3 (Figure 1) demonstrated modest binding to
SMARCA2 and CBP.15 Most significantly, compound 5 did
not demonstrate any detectable activity toward p38α (Kd >
200 μM). This indicates that this SAR study was able to
systematically reduce p38α affinity by >90,000-fold (relative to
compound 4, Kd = 2.2 nM) while maintaining BET selectivity
and affinity.
a
compound
R
X
BRD4-D1 IC50 (μM)
bc
,
6
4−F-C6H4
c-hexyl
c-pentyl
t-Bu
H
H
H
H
>100
b
16
17
18
19
20
21
22
>100
>100
>100
>100
>100
b
b
b
b
i-Pr
n-Pr
c-Pr
Me
C(NH)NH2
C(NH)NH2
C(NH)NH2
C(NH)NH2
61 8.1
9.7 1.8
a
IC50 values were determined by fluorescence anisotropy. Data
represents the mean and standard deviation of three independent
trials. The IC50 value was determined to be >100 μM by fluorescence
anisotropy. The IC50 value was determined to be 27 μM by
b
c
AlphaScreen by Reaction Biology.
ligand in this assay (>100 μM). The low solubility of
compounds 6, 16, 17, and 18 was an issue in the fluorescence
anisotropy assay. Herein, the guanidine group was added to
increase the solubility. Most of the alkyl groups yielded little
activity (16−21) with the exception of a methyl group. The
methyl triazole (22) was more potent. This is similar to the
results in a SAR study with compound 1 that demonstrated
methyl was the optimal N-substituent in the N-ε-acetylated
lysine mimic.17
To gain a structural understanding, a BRD4-D1 cocrystal
structure was obtained with compound 27. This information
could be compared to a cocrystal structure of compound 3
Having identified that a methyl substituent significantly
enhanced BRD4-D1 binding, attention was turned toward
C
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ACS Medicinal Chemistry Letters
Letter
ID 4IOR), including the water bridging to Y97.15 This mode of
interaction was used to support the BRD4-D1 selectivity for
compound 3. In the absence of this structured water molecule,
diminished binding affinity would be expected due to (i) the
energy required to displace the bound water and (ii) the loss of
the bridging hydrogen bond. This is consistent with the
increase in potency observed for compound 22 relative to
compound 6 (Table 2). Comparing BRD4-D1 cocrystal
structures containing compound 27 vs 3 demonstrates that
the pyrimidine ring and pyridine ring occupy similar binding
conformations relative to the WPF shelf (Figure 3b). This
supports the notion that while the pyrimidine nitrogen atom in
compound 3 is essential for p38α binding (Table 1), replacing
the nitrogen with a C−H unit only minimally affects the
BRD4-D1 binding.
The inhibitors described above were assayed in MM.1S cells.
Multiple myeloma cell strains from hematological cancers have
a strong dependence on c-Myc.7 The survival of MM.1S cells
are highly BRD4 dependent because of an IgH and MYC
rearrangement.7 Reports have shown that BET inhibitors
effectively decrease c-Myc transcription, which results in
decreased cell viability.15,30 In MM.1S cells, guanidinylated
compounds 22, 5, and 27 displayed weak activity (Table 5,
Table 4. Demonstrating Selectivity for Compound 5 and 27
protein target
X = O (5)
X = NH (27)
a
BRD4-D1 IC50 (μM)
3.6 0.05
1.1 0.63
0.94 0.48
>100
4.5 0.35
1.2 0.62
2.1 1.1
>100
78 48
>25
b
BRD4-D1 Kd (μM)
BRD4-D2 Kd (μM)
b
b
SMARCA2 Kd (μM)
b
CBP (μM)
>100
>200
c
p38α Kd (μM)
a
IC50 values were determined by fluorescence anisotropy. Data
represents the mean and standard deviation of three independent
b
trials. Kd values were determined by BROMOscan. Data represents
c
the mean and standard error from two independent trials. Kd values
were determined by KINOMEscan. Data represents the mean and
standard error from two independent trials.
(PDB ID 6MH1).13 The central triazole nitrogen (N2) in
compound 27 serves as the N-ε-acetylated lysine mimic by
forming a direct hydrogen bond to N140 (Figure 3a). This was
Table 5. Viability of MM.1S Cells Treated with Compounds
BRD4-D1 IC50
MM.1S
EC50 (μM)
a
b
compound
R
X
Y
(μM)
22
5
C(NH)NH2
C(NH)NH2
O
O
N
CH
9.7 1.8
3.6 0.05,
1.7 0.30
>50
>50
c
27
28
29
C(NH)NH2
H
H
NH
O
O
CH
N
CH
4.5 0.35
11 2.5
2.9 0.07,
1.3 0.25
>50
6.6 1.9
2.9 0.6
c
30
H
NH
CH
3.9 0.35
6.3 1.1
a
IC50 values were determined by fluorescence anisotropy. Data
represents the mean and standard deviation of three independent
b
trials. Data reported are mean SEM of three biological replicates,
Figure 3. BRD4-D1 compound 27 cocrystal structure and
comparative analysis to dual p38α-BRD4 inhibitor 3. (A) Cocrystal
structure of 27 with BRD4-D1. Key interactions include a hydrogen
bond of N2 of 27 to the amine of N140 (3.1 Å) and a water-mediated
hydrogen bond of N3 of 27 to the hydroxyl of Y97 (2.9 Å, 2.6 Å). (B)
Overlay of 27 (green) with 3 (gray). (C) Structure of 27. (D)
Structure of 3.
with three technical replicates each. EC50 values were determined
c
using the Nonlinear fit algorithm on GraphPad Prism. IC50 values
were determined by AlphaScreen by Reaction Biology.
EC50 > 50 μM). This weak activity may be due to decreased
cell permeability. To test this hypothesis, several analogs with a
free piperidine NH were assayed. Compounds 28, 29, and 30
demonstrated clear antiproliferative effects in MM.1S cells
(EC50 = 6.6, 2.9, and 6.3 μM, respectively). The observed EC50
values loosely correlate to the BRD4-D1 in vitro fluorescence
anisotropy assay IC50 values. Additionally, decreased levels of
c-Myc were observed by Western blot after treatment with
compounds 28, 29, and 30 for 6 h (see Supporting
Information).
In conclusion, we have successfully reversed the p38α/
BRD4-D1 selectivity observed with compound 4. Originally,
compound 4 demonstrated a >10,000-fold selectivity for p38α
over BRD4-D1. By modifying the hinge binding motif and
somewhat surprising because the terminal nitrogen (N3) has
been calculated to be more basic than the central nitrogen
(N2).27 One explanation for this binding mode is that the
terminal nitrogen (N3) in compound 27 is forming a hydrogen
bond to Y97 via a bridging structured water molecule in the
cocrystal structure (Figure 3a). Similar interactions are
observed for methyl isoxazoles and pyrazoles.26,28,29 In the
cocrystal structure with compound 3, the 4-fluorophenyl group
displaces three of four structured water molecules in this
binding pocket relative to a DMSO cocrystal structure (PDB
D
DOI: 10.1021/acsmedchemlett.9b00227
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ACS Medicinal Chemistry Letters
Letter
(4) Andrieu, G.; Belkina, A. C.; Denis, G. V. Clinical Trials for BET
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p38α by >100-fold. This represents a >1,000,000 relative
difference in binding. A cocrystal structure and cellular assays
further support the binding mode of the triazole inhibitor and
the BET activity. In the future, this molecular design approach
may be applied to other previously reported dual p38-BET
inhibitors including 3, SB-202190, and SB-203580.
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ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acsmedchem-
lett.9b00227.
Experimental procedures and data (PDF)
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: wcp@umn.edu.
*E-mail: jtopczew@umn.edu.
(10) Boehm, J. C.; Bower, M. J.; Gallagher, T. F.; Kassis, S.; Johnson,
S. R.; Adams, J. L. Phenoxypyrimidine Inhibitors of p38α Kinase
Synthesis and Statistical Evaluation of the p38 Inhibitory Potencies of
a Series of 1-(piperidin-4-yl)-4-(4-fluorophenyl)-5-(2-phenoxypyrimi-
dine-4-yl) Imidazoles. Bioorg. Med. Chem. Lett. 2001, 11, 1123−1126.
ORCID
Angela S. Carlson: 0000-0002-6812-4662
Anand Divakaran: 0000-0002-1782-6234
William C. K. Pomerantz: 0000-0002-0163-4078
Joseph J. Topczewski: 0000-0002-9921-5102
(11) Ciceri, P.; Muller, S.; O’Mahony, A.; Fedorov, O.;
̈
Filippakopoulos, P.; Hunt, J. P.; Lasater, E. A.; Pallares, G.; Picaud,
S.; Wells, C.; Martin, S.; Wodicka, L. M.; Shah, N. P.; Treiber, D. K.;
Knapp, S. Dual Kinase-Bromodomain Inhibitors for Rationally
Designed Polypharmacology. Nat. Chem. Biol. 2014, 10, 305−312.
Author Contributions
†A.S.C. and H.C. contributed equally to this study. A.S.C.
synthesized the molecules with H.C. and R.M.B. Biophysical
experiments were performed by H.C. Cellular assays were
performed by A.D. The cocrystal structure was solved by J.A.J.
Research was directed by J.J.T. and W.C.K.P. The manuscript
was written through contributions of all authors. All authors
have given approval to the final version of the manuscript.
̈
(12) Martin, M. P.; Olesen, S. H.; Georg, G. I.; Schonbrunn, E.
Cyclin-Dependent Kinase Inhibitor Dinaciclib Interacts with the
Acetyl-Lysine Recognition Site of Bromodomains. ACS Chem. Biol.
2013, 8, 2360−2365.
(13) Urick, A. K.; Hawk, L. M. L.; Cassel, M. K.; Mishra, N. K.; Liu,
S.; Adhikari, N.; Zhang, W.; dos Santos, C. O.; Hall, J. L.; Pomerantz,
W. C. K. Dual Screening of BPTF and Brd4 Using Protein-Observed
Fluorine NMR Uncovers New Bromodomain Probe Molecules. ACS
Chem. Biol. 2015, 10, 2246−2256.
Notes
The authors declare the following competing financial
interest(s): The authors submitted a provisional patent on
the composition of matter for the compounds disclose here.
(14) Ember, S. W.; Lambert, Q. T.; Berndt, N.; Gunawan, S.; Ayaz,
M.; Tauro, M.; Zhu, J.-Y.; Cranfill, P. J.; Greninger, P.; Lynch, C. C.;
Benes, C. H.; Lawrence, H. R.; Reuther, G. W.; Lawrence, N. J.;
ACKNOWLEDGMENTS
■
̈
Schonbrunn, E. Potent Dual BET Bromodomain-Kinase Inhibitors as
We acknowledge Daniel A. Harki for his helpful discussions
during this project. MM.1S cells were a gift from Dr. Brian Van
Ness at the University of Minnesota. This work was supported
by the NIGMS (Grant R35GM124718), the American Cancer
Society (# 129819-IRG-16-189-58-IRG88), the University of
Minnesota Masonic Cancer Center (Pre-R01 pilot grant), and
the University of Minnesota. J.J. was supported by a National
Institutes of Health Biotechnology training grant
5T32GM008347-23. A.D. was supported by the NIH
chemistry−biology interface training grant at the University
of Minnesota, 5T32GM008700-18.
Value-Added Multitargeted Chemical Probes and Cancer Therapeu-
tics. Mol. Cancer Ther. 2017, 16, 1054−1067.
(15) Divakaran, A.; Talluri, S. K.; Ayoub, A. M.; Mishra, N.; Cui, H.;
Widen, J. C.; Berndt, N.; Zhu, J.-Y.; Carlson, A. S.; Topczewski, J. J.;
̈
Schonbrunn, E.; Harki, D. A.; Pomerantz, W. C. K. Molecular Basis
for the N-Terminal Bromodomain and Extra Terminal (BET) Family
Selectivity of a Dual Kinase-Bromodomain Inhibitor. J. Med. Chem.
2018, 61, 9316−9334.
(16) Watts, E.; Heidenreich, D.; Tucker, E.; Raab, M.; Strebhardt,
K.; Chesler, L.; Knapp, S.; Bellenie, B.; Hoelder, S. Designing Dual
Inhibitors of Anaplastic Lymphoma Kinase (ALK) and Bromodo-
main-4 (BRD4) by Tuning Kinase Selectivity. J. Med. Chem. 2019, 62,
2618−2637.
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