Identification of BRaf-Sparing Amino-Thienopyrimidines with Potent IRE1α Inhibitory Activity

Article abstract of DOI:10.1021/acsmedchemlett.0c00344

Amino-quinazoline BRaf kinase inhibitor 2 was identified from a library screen as a modest inhibitor of the unfolded protein response (UPR) regulating potential anticancer target IRE1α. A combination of crystallographic and conformational considerations were used to guide structure-based attenuation of BRaf activity and optimization of IRE1α potency. Quinazoline 6-position modifications were found to provide up to 100-fold improvement in IRE1α cellular potency but were ineffective at reducing BRaf activity. A salt bridge contact with Glu651 in IRE1α was then targeted to build in selectivity over BRaf which instead possesses a histidine in this position (His539). Torsional angle analysis revealed that the quinazoline hinge binder core was ill-suited to accommodate the required conformation to effectively reach Glu651, prompting a change to the thienopyrimidine hinge binder. Resulting analogues such as 25 demonstrated good IRE1α cellular potency and imparted more than 1000-fold decrease in BRaf activity.

Full text of DOI:10.1021/acsmedchemlett.0c00344

pubs.acs.org/acsmedchemlett
Letter
Identification of BRaf-Sparing Amino-Thienopyrimidines with
Potent IRE1α Inhibitory Activity
Ramsay E. Beveridge,* Heidi Ackerly Wallweber, Avi Ashkenazi, Maureen Beresini, Kevin R. Clark,
́
Paul Gibbons, Elise Ghiro, Susan Kaufman, Alexandre Larivee, Melissa Leblanc, Jean-Philippe Leclerc,
Alexandre Lemire, Cuong Ly, Joachim Rudolph, Jacob B. Schwarz, Sanjay Srivastava, Weiru Wang,
Liang Zhao, and Marie-Gabrielle Braun*
Cite This: https://dx.doi.org/10.1021/acsmedchemlett.0c00344
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ABSTRACT: Amino-quinazoline BRaf kinase inhibitor 2 was identified from a library screen as a modest inhibitor of the unfolded
protein response (UPR) regulating potential anticancer target IRE1α. A combination of crystallographic and conformational
considerations were used to guide structure-based attenuation of BRaf activity and optimization of IRE1α potency. Quinazoline 6-
position modifications were found to provide up to 100-fold improvement in IRE1α cellular potency but were ineffective at reducing
BRaf activity. A salt bridge contact with Glu651 in IRE1α was then targeted to build in selectivity over BRaf which instead possesses
a histidine in this position (His539). Torsional angle analysis revealed that the quinazoline hinge binder core was ill-suited to
accommodate the required conformation to effectively reach Glu651, prompting a change to the thienopyrimidine hinge binder.
Resulting analogues such as 25 demonstrated good IRE1α cellular potency and imparted more than 1000-fold decrease in BRaf
activity.
KEYWORDS: IRE1α, BRaf, kinase, unfolded protein response
conserved branch of the UPR. In the event of unfolded protein
he unfolded protein response (UPR) is a cytoprotective
Tprotein synthesis homeostasis mechanism that is triggered stress in the ER, IRE1α undergoes dimerization/oligomeriza-
tion and autophosphorylation which activates the transcription
factor X-box binding protein 1 (XBP1). The ensuing splicing of
XBP1 results in transcription of UPR genes and expression of ER
chaperone proteins which restore normal cellular protein
synthesis and trigger degradation of excessive unfolded protein.9
For these reasons, it has been proposed that inhibition of IRE1α
dimerization/oligomerization and endonuclease activity could
be an attractive strategy to selectively disrupt the UPR in cancer
cells and trigger the apoptosis cascade.10−12 In particular, IRE1α
by the accumulation of unfolded proteins in the endoplasmic
reticulum (ER).1 In the event of UPR signaling disruption, or
extreme ER unfolded protein stress, the cellular apoptosis
mechanism is activated, leading to cell death.2−4 Many
neoplastic disorders (e.g., multiple myeloma) have a high
protein synthesis burden and rely heavily on specific branches of
the UPR, particularly inositol requiring enzyme 1-alpha
(IRE1α), to avoid the apoptosis cascade and survive.5−7 As a
result, selective interference with the UPR machinery is a
potentially attractive approach to initiate caspase-mediated
death of cancer cells and thus constitutes a promising strategy
toward the discovery of novel cancer therapeutics.8
Received: June 23, 2020
Accepted: October 2, 2020
Management of the UPR is governed by three main branches
which control transcriptional response mechanisms.1 Among
these, IRE1α is a bifunctional ER transmembrane sensor protein
with kinase and RNase activity which regulates the most highly
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Figure 1. X-ray cocrystal structure of ligand 2 (yellow) identified from a Genentech internal kinase library screen (cyan = receptor of 2, PBD code
6XDF, 2.54 Å) overlaid with compound (1) (pink) in hIRE1 (brown = receptor of 1, PDB code 4U6R, 1.90 Å).
represents a rational target for multiple myeloma, because it
regulates ER-associated degradation of misfolded proteins as
well as secretion of several cytokines and chemokines known to
be important for survival of malignant plasma cells in the bone
marrow microenvironment.13−15 As a consequence, there has
been considerable interest toward discovery of small molecule
inhibitors of IRE1α endonuclease activity.16−20
BRaf kinase inhibitor program25 with potent ATP-competitive
IRE1α binding affinity (IRE1α-TR-FRET IC50 = 0.0068 μM).
Compound 2 also demonstrated a modest inhibitory effect on
IRE1α endonuclease activity as measured in both an enzymatic
RNase inhibition assay (IRE1α-RNase IC50 = 0.200 μM) and a
cellular X-box binding protein-1 splicing luciferase reporter
assay (XBP1-luc IC50 = 5.58 μM). A crystal structure of 2 bound
to IRE1 was obtained which showed that this ligand binds to the
kinase domain ATP pocket in a similar fashion as ligand 1 with
amino-quinazoline A-ring hinge contacts, sulfonyl urea DFG-
motif binding, and pyrrolidine D-ring occupation of the αC-
helix pocket (Figure 1). Some unique features of 2 include the
absence of a polar headgroup salt bridge contact with Glu651,
the existence of a pseudoring by intramolecular H-bonding
between the N−H proton of the amide group and the one of
nitrogen atoms on the quinazoline, and the presence of a new
pocket close to the P-loop region of the quinazoline B-ring.
Based on compound 2, a program was initiated to improve
cellular potency of this starting point. Our primary goals for this
series were to improve potency for IRE1α and reduce BRaf
kinase binding affinity (BRaf Ki = 0.0023 μM). Using structure
guided variation of core substituents and core replacement
strategies; we were ultimately able to achieve both objectives as
elaborated in the following part.
a
Table 1. 6-Me-Quinazoline Improves XBP1 Potency
IRE1α-TR-
FRET
IC50 (μM)
IRE1α-
RNase
IC50 (μM)
XBP1-luc
IC50 (μM)
BRaf
Ki (μM)
compd
R1
3
4
H
Me
0.0089
0.005
0.056
0.031
12.7
1.1
-
≤0.00008
a
Data represent an average of ≥2 separate determinations. See the
Supporting Information for standard deviations.
To drive our efforts, four assays were routinely used to
evaluate compounds for their IRE1α and BRaf activities: IRE1α-
TR-FRET was used to measure ATP-competitive IRE1α kinase
binding potency; IRE1α -RNase was used to measure enzymatic
endonuclease inhibition via cleavage of the XBP1 stem loop;
XBP1 provided a cellular luciferase read-out of functional
IRE1α-RNase inhibitory activity; and BRaf Ki values were
determined in a kinase activity assay to evaluate potency against
the key BRaf kinase antitarget. While the IRE1α-TR-FRET
binding assay was routinely run to ensure ATP-competitive
binding of new ligands to this kinase, the relatively high enzyme
concentration required in this assay unfortunately resulted in an
inability to discriminate between compound potencies below
the enzyme concentration (less than ∼10 nM). One
consequence of this limitation was that a direct comparison of
BRaf and IRE1α binding potencies could not be used as a
Interestingly, it has been shown that interference of IRE1α
RNase activity can be allosterically controlled through targeting
of the enzyme’s C-terminal kinase domain.21−24 For example,
Harrington and co-workers at Amgen recently disclosed a potent
and selective inhibitor of IRE1α RNase activity which binds to
the IRE1α kinase domain (1, Figure 1).24 Notably, the crystal
structure of (1) in hIRE1α suggests that kinase domain binding
with this ligand results in a conformational shift of the αC-helix
resulting in reduced capacity of the enzyme to undergo crucial
RNase active dimerization and oligomerization.
Our interest in exploring IRE1α as an anticancer target
prompted an internal kinase focused screen toward identifying
IRE1α RNase inhibitors. A total of 92K compounds were
screened and these efforts initially identified compound 2
(Figure 1) as a promising hit from a prior amino-quinazoline
B
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a
Table 2. Representative Amino-Quinazoline B-Ring and D-Ring SAR
a
b
Data represent an average of ≥2 separate determinations. See the Supporting Information for standard deviations. The potency was determined
once.
rigorous selectivity metric. Nevertheless, the relative magnitudes
of the BRaf Ki values among compounds still served as a useful
metric to identify features which display BRaf sparing character
toward our goal of identifying an IRE1α-selective ligand. In
addition, IRE1α RNase assay data presents similar limitations in
its ability to discriminate compounds with potencies better than
10 nM. Ultimately, the cellular XBP1 luciferase assay was
deemed the most sensitive discriminator of functional RNase
ligand potency, and as a result, our design efforts toward
improving IRE1α inhibitory activity were guided primarily by
activity in the XBP1 assay.
To further explore the potential impact of αC-helix shift on
IRE1α potency, our attention first turned to examining
additional amino-quinazoline BRaf ligands from our database
with D-ring modifications that could push the αC-helix.
Interestingly, this effort instead revealed a 6-Me-quinazoline
B-ring substituent as a promising lead toward improved cellular
XBP1 potency (Table 1). Structurally, this methyl group
appeared to occupy a previously unexplored pocket close to
C
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the P-loop which we then sought to exploit toward further gains
in IRE1α potency.
To guide our design efforts, analysis of the crystal structure of
2 indicated that this quinazoline B-ring is surrounded by polar
residues and provides sufficient space to accommodate larger
alkyl groups including 5- or 6-membered ring systems.
Moreover, the imidazole ring of the His692 residue on the P-
loop appeared to be ∼4−5 Å away from the quinazoline 6-
position, suggesting incorporation of quinazoline substituents
that could π-stack or hydrogen bond with this imidazole side
chain could improve affinity. Altogether, these observations
prompted an initial design strategy that focused on deploying
heterocycles in this region to match the polar nature of this
pocket while also targeting placement of aryl π-systems and
heteroatoms in close proximity to the His692 imidazole ring.
Specifically, combination of the quinazoline substituted with
heterocycles at the 6-position and containing aryl sulfonamide
D-rings was deemed an attractive strategy toward improving
cellular XBP1 potency since such analogues appeared enabled
for rapid structure−activity relationship (SAR) evaluation and
were not predicted to interfere with the key kinase domain polar
binding contacts.
Figure 2. X-ray cocrystal structure of ligand 13 (yellow) in hIRE1α
showing dimethyl-pyrazole quinazoline substituent interacting with P-
loop residue Leu577 and His579 (PBD = 6XDB, 2.45 Å).
We first explored incorporation of pyridines in this quinazo-
line pocket, which did not lead to improved XBP1 activity but
appeared tolerated, providing an initial validation that aromatic
heterocycles could be accommodated in this space (Table 2,
compounds 5 and 6). As a next step, 5-membered aromatic
heterocycles were investigated leading to the identification of N-
Me pyrazole 8 as a promising hit toward improved cellular
potency and a potential proof-of-concept for interacting
specifically with the His692 imidazole. Other N-Me pyrazole
regioisomers 9 and 10 and desmethyl pyrazole 7 showed poor
XBP1-luc potency which supported the possible existence of a
directionally important hydrogen bond accepting interaction
from His692. Next, further tuning of this 3-methyl pyrazole
group with additional methyl substitutions distinguished the 4-
quinazoline-1,3-dimethyl-pyrazole 11 as optimal for potency
gains. In the end, exploration of the 1,3-dimethyl-pyrazole
quinazoline feature in combination with other D-ring aryl
sulfonamide groups resulted in the identification of compounds
with up to 500-fold improvement in XBP1-luc cellular potency
relative to the initial library hit 2 (Table 2, compounds 12−14).
To rationalize these potency gains, a crystal structure of 4-
quinazoline-1,3-dimethyl-pyrazole ligand 13 in hIRE1α was
obtained, which shows the pyrazole group engaging in a
hydrogen bonding interaction with the imidazole of His692
(Figure 2). In addition, the two methyl groups engage in weak
C−H hydrogen bonding interactions with the backbone
carbonyl oxygen of Leu577 and His579.
Figure 3. (a) Model of compound 2 with a trans-diaminocyclohexyl
group attached to the quinazoline A-ring amine in IRE1α (orange)
showing predicted salt bridge formation with Glu651. (b) Model of 2
with a trans-diaminocyclohexyl group attached to the quinazoline A-
ring amine in BRaf (cyan). Green structure = compound 2.
a
Table 3. Quinazoline A-Ring Polar Head Group SAR
While the results in Table 2 illustrate significant IRE1α
cellular potency gains, it was disappointing to observe that these
quinazoline B-ring modifications failed to show any meaningful
decrease in BRaf kinase activity. To address this, we next
considered the potential of targeting a salt bridge contact with a
nonconserved residue Glu651 in IRE1α as a strategy to build in
selectivity over BRaf kinase as this residue is a histidine (His539)
in BRaf. A basic amine, while forming a salt bridge with Glu651,
was expected to be repulsed by His539 in BRaf, or at least not
engage in an attractive interaction. Encouragingly, structural
models which transposed the trans-diaminocyclohexane group
from 1, a compound exhibiting minimal BRaf inhibition, onto
quinazoline 2 in both IRE1α and BRaf appeared to support this
selectivity approach (Figure 3). In IRE1α, we were pleased to
a
Data represent an average of ≥2 separate determinations. See the
b
Supporting Information for standard deviations. The potency was
determined once.
D
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Figure 4. Quinazoline (blue, circle) to thienopyrimidine (green, square) design concept to improve bioactive hinge conformation and improve
potency of polar headgroup incorporation. The quantum mechanical torsional profiles shown represent energies (kcal/mol) of the amino-quinazoline
abcd dihedral angle when scanned from −180° to 0° in compounds 20 and 21. Calculations were performed at the MP2/6-311+G**//HF/6-31G*
level of theory with the PCM water solvent model using the Gaussian software package.26 The crystal structure of 1 has an abcd torsion angle of ∼23°
(labeled in red on plot above) to enable the formation of both a Glu651 salt bridge and a Cys645 hydrogen bond with the amino-quinazoline N−H.
a
Table 4. Thienopyrimidine Hinge SAR
a
b
Data represent an average of ≥2 separate determinations. See the Supporting Information for standard deviations. The potency was determined
once.
observe that incorporating a trans-diaminocyclohexane sub-
stitution off the quinazoline A-ring amine of 2 was predicted to
form a salt bridge contact with Glu651 and retained a similar fit
and binding mode relative as the parent 2 (Figure 3a). A model
of the same compound in BRaf suggests that the cyclohexyl ring
of the newly added motif would clash with the BRaf Trp531 side
chain and would not form a productive contact with the Braf
His539 depending on its charge state and preferred rotamer
(Figure 3b).
resulted in reduced IRE1α-TR-FRET binding potency and
concomitant poor IRE1α cellular potency compared to the
amino-quinazoline ligands in Tables 1 and 2. Nevertheless, we
were encouraged by the trans-diaminocyclohexane containing
compound 19, which retained good IRE1α-TR-FRET binding
potency and showed a substantial 4250-fold drop in BRaf
binding potency and only a 19-fold decrease in XBP1-luc activity
compared to 4. This difference suggested BRaf-sparing was
occurring, and it prompted us to further examine this concept
toward maintaining reduced BRaf activity and improving IRE1α
potency.
To explore this BRaf-sparing concept, a set of amino-
quinazolines with basic amine polar head groups were prepared
and evaluated (Table 3). Unfortunately, efforts in this area
E
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microsomes (CLHLM = 9.5 mL/min/kg; CLMLM = 34 mL/min/
kg) and did not display significant hERG inhibition (1.1%
inhibition at 1 μM; 6.4% inhibition at 10 μM). In addition, the
related BRaf-sparing thienopyrimidine analogue 24 was also
found to display good general kinase selectivity in a 220 member
kinase panel (9/220 kinases inhibited >50% at 1 μM; see the
Supporting Information for details).
In conclusion, we found that through appropriate substitution
at the quinazoline 6-position a new pocket in IRE1α can be
leveraged (through targeting of the P-loop His692 residue) to
provide more than 100-fold improvement in cellular XBP1
potency. After extensive SAR studies at the quinazoline 6-
position, it was determined that this new potency vector was
ineffective toward reducing activity against the key BRaf kinase
antitarget. Structural differences in the hinge regions of IRE1α
and BRaf prompted design of amino-substituted quinazolines
with the goal of targeting a salt bridge with Glu651 in IRE1α as a
strategy to improve their BRaf selectivity profile. Torsional
analyses then directed our attention toward deploying the
related amino-thienopyrimidine hinge scaffold toward improved
accommodation of the desired bioactive conformation. This
strategy ultimately resulted in identification of trans-diamino-
cyclohexane substituted amino-thienopyrimidine 25 with good
XBP1 potency and decreased BRaf binding potency as a
promising lead for further optimization. Overall, this work
exemplifies the importance of torsion profiles and ligand
conformational considerations in design and showcases the
potential of exploiting hinge connected polar head groups to
achieve selectivity in kinase programs.
Figure 5. X-ray cocrystal structure of ligand 23 (yellow) in hIRE1α
showing trans-diaminocyclohexane salt bridge formation with Glu651
(PBD = 6XDD, 2.40 Å).
The reduced IRE1α binding potency of 19 motivated us to
consider conformational effects of the trans-diaminocyclohex-
ane on predicted bioactive hinge conformation. The crystal
structure of 1 with the similar trans-diaminocyclohexane moiety
in the same location as 19 gives insight to the preferred dihedral
angle of this moiety in the IRE1α protein. In this context, we
considered replacing the quinazoline A/B ring system with the
structurally related thienopyrimidine bicycling hinge which
reduces the strain energy that would be expected in the bioactive
conformation of the quinazoline due to the steric clash of the
polar headgroup and the 5-position C−H of the quinazoline
(Figure 4). Indeed, comparison of computed energies over a
torsion scan of the simplified trans-diaminocyclohexane-
quinazoline 20 and trans-diaminocyclohexane-thienopyrimidine
21 suggested that the predicted bioactive conformation of
thienopyrimidine 21 has reduced strain energy compared to the
predicted quinazoline 20 bioactive conformation. In addition,
thienopyrimidines have been previously used as quinazoline
surrogates in BRAF inhibitors and this together with the
structure-based rationale outlined in Figure 4 motivated us to
pursue this scaffold.25
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acsmedchemlett.0c00344.
Assay protocols, assay standard deviations, crystallo-
graphic information, characterization data for compounds
5−19 and 22−25, synthetic procedures for compounds
14, 19, 22, and 24, QM torsion profiles for 20−21, and
kinase selectivity for 24 (PDF)
As the torsion scan profiling provided a new promising
hypothesis to improve IRE1α potency, a set of amino-
substituted thienopyrimidines were synthesized (Table 4). As
an initial validation of this hinge scaffold, the parent amino-
thienopyrimidine 22 displayed similar IRE1α binding, XBP1
potency and BRaf activity as its amino-quinazoline counterpart 4
(Table 1).27 Pleasingly, it was observed that the trans-
diaminocyclohexane group was indeed better accommodated
on the thienopyrimidine hinge compared to the quinazoline
hinge supporting this conformation-based approach to optimize
targeting of the Glu651 salt bridge (e.g., 23). Importantly, we
obtained a crystal structure of compound 23 in hIRE1α which
showed the trans-diaminocyclohexane group engaging Glu651
in a salt bridge (Figure 5) which we presume contributes to the
large gain in selectivity against BRaf, as the equivalent residue in
BRaf is a histidine.
A brief survey of additional sulfonamide D-ring groups was
performed to identify moieties that maintained XBP1 potency
while also continuing to be BRaf sparing in the context of the
trans-diaminocyclohexyl thienopyrimidine hinge system. In the
end, these efforts led to the identification of 25 with good IRE1-
XBP1 cellular potency and >1000-fold decrease in BRaf Ki
potency vs 4 as a promising lead for further optimization.
Compound 25 was also observed to be moderately stable in liver
AUTHOR INFORMATION
Corresponding Authors
■
Ramsay E. Beveridge − Paraza Pharma Inc., Montreal, QC,
Canada H4S 2E1; Email: ramsay.beveridge@
parazapharma.com
Marie-Gabrielle Braun − Genentech Inc., South San Francisco,
California 94080-4990, United States; orcid.org/0000-
0002-5644-3711; Email: braun.mariegabrielle@gene.com
Authors
Heidi Ackerly Wallweber − Genentech Inc., South San Francisco,
California 94080-4990, United States
Avi Ashkenazi − Genentech Inc., South San Francisco, California
94080-4990, United States
Maureen Beresini − Genentech Inc., South San Francisco,
California 94080-4990, United States
Kevin R. Clark − Genentech Inc., South San Francisco, California
94080-4990, United States
Paul Gibbons − Genentech Inc., South San Francisco, California
94080-4990, United States
Elise Ghiro − Paraza Pharma Inc., Montreal, QC, Canada H4S
2E1
F
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Letter
§Susan Kaufman − Genentech Inc., South San Francisco,
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́
Alexandre Larivee − Paraza Pharma Inc., Montreal, QC,
Canada H4S 2E1
Melissa Leblanc − Paraza Pharma Inc., Montreal, QC, Canada
H4S 2E1
Jean-Philippe Leclerc − Paraza Pharma Inc., Montreal, QC,
Canada H4S 2E1
Alexandre Lemire − Paraza Pharma Inc., Montreal, QC, Canada
H4S 2E1
Cuong Ly − Genentech Inc., South San Francisco, California
94080-4990, United States
Joachim Rudolph − Genentech Inc., South San Francisco,
California 94080-4990, United States
Jacob B. Schwarz − Genentech Inc., South San Francisco,
California 94080-4990, United States
Sanjay Srivastava − Paraza Pharma Inc., Montreal, QC, Canada
H4S 2E1
Weiru Wang − Genentech Inc., South San Francisco, California
94080-4990, United States
Liang Zhao − Paraza Pharma Inc., Montreal, QC, Canada H4S
2E1
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Complete contact information is available at:
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Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
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W.; Clark, K.; Kaufman, S.; Beresini, Maureen H.; Laing, Steven T.;
Sandoval, W.; Lorenzo, M.; Wu, J.; Ly, J.; De Bruyn, T.; Heidersbach,
A.; Haley, B.; Gogineni, A.; Weimer, R. M.; Lee, D.; Braun, M. G.;
Rudolph, J.; Van Wyngarden, M. J.; Sherbenou, D. W.; Gomez-Bougie,
P.; Amiot, M.; Acosta-Alvear, D.; Walter, P.; Ashkenazi, A. Disruption
of IRE1α through its kinase domain attenuates multiple myeloma. Proc.
Natl. Acad. Sci. U. S. A. 2019, 116, 16420−16429.
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Lust, S.; Tam, A.; Solo-Cordero, D. E.; Bouley, D. M.; Offner, F.; Niwa,
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(17) Ranatunga, S.; Tang, C.-H. A.; Kang, C. W.; Kriss, C. L.;
Kloppenburg, B. J.; Hu, C.-C. A.; Del Valle, J. R. Synthesis of novel
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The authors declare no competing financial interest.
§Susan Kaufman tragically passed away on July 29, 2020.
ACKNOWLEDGMENTS
■
We would like to thank the members of the synthetic chemistry
and pharmacology teams at Wuxi Shanghai and Shanghai
ChemPartner. We thank Genentech Analytical, Purification,
DMPK, Pharmacology, Safety Assessment, and in vivo Studies
Group colleagues for their contributions. In particular, we would
like to acknowledge Chris Sneeringer for running BRAf assays.
We thank staff at Advanced Light Source and Stanford
Synchrotron Radiation Lightsource for assistance on data
collection.
ABBREVIATIONS
■
IRE1α inositol requiring enzyme 1-alpha
BRaf serine/threonine-protein kinase BRaf
QM
quantum mechanics
UPR unfolded protein response
XBP1 x-box binding protein-1
ER
endoplasmic reticulum
HLM human liver microsomes
MLM mouse liver microsomes.
(18) Sanches, M.; Duffy, N. M.; Talukdar, M.; Thevakumaran, N.;
Chiovitti, D.; Canny, M. D.; Lee, K.; Kurinov, I.; Uehling, D.; Al-awar,
R.; Poda, G.; Prakesh, M.; Wilson, B.; Tam, V.; Schweitzer, C.; Toro, A.;
Lucas, J. L.; Vuga, D.; Lehmann, L.; Durocher, D.; Zeng, Q.; Patterson,
J. B.; Sicheri, F. Structure and mechanism of action of the hydroxyl-aryl-
aldehyde class of IRE1 endoribonuclease inhibitors. Nat. Commun.
2014, 5, 4202.
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H
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