SAR studies around a series of triazolopyridines as potent and selective PI3Kγ inhibitors

Article abstract of DOI:10.1016/j.bmcl.2012.06.049

Herein we describe the SAR of a novel series of 6-aryl-2-amino- triazolopyridines as potent and selective PI3Kγ inhibitors. The 6-aryl-triazolopyridine core was identified by chemoproteomic screening of a kinase focused library. Rapid chemical expansion a

Full text of DOI:10.1016/j.bmcl.2012.06.049

Bioorganic & Medicinal Chemistry Letters 22 (2012) 5257–5263
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Bioorganic & Medicinal Chemistry Letters
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SAR studies around a series of triazolopyridines as potent and selective
PI3Kc inhibitors
Kathryn Bell a, , Mihiro Sunose a, Katie Ellard a, Andrew Cansfield a, Jess Taylor a, Warren Miller a,
⇑
Nigel Ramsden a, Giovanna Bergamini b, Gitte Neubauer b
a Cellzome Ltd, Chesterford Research Park, Cambridge, CB10 1XL, United Kingdom
b Cellzome AG, Meyerhofstr. 1, 69117 Heidelberg, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Herein we describe the SAR of a novel series of 6-aryl-2-amino-triazolopyridines as potent and selective
Received 4 May 2012
Revised 14 June 2012
Accepted 15 June 2012
Available online 23 June 2012
PI3K
kinase focused library. Rapid chemical expansion around a bi-functional core identified the key features
required for PI3K activity and selectivity. The series was optimized to afford 43 (CZC19945), a potent
PI3K inhibitor with high oral bioavailability and selectivity over PI3K and PI3Kd. Modification to the
c inhibitors. The 6-aryl-triazolopyridine core was identified by chemoproteomic screening of a
c
c
a
core afforded 53 (CZC24832) which showed increased selectivity over the entire kinome in particular
over PI3Kb.
Keywords:
PI3K
c
Ó 2012 Elsevier Ltd. All rights reserved.
Kinase inhibitor
Inflammation
Triazolopyridine
Collagen induced arthritis
Phosphoinositide 3-kinase
c
(PI3K
c
) is one of four Class I PI3Ks,
identified the 6-aryl-[1,2,4]triazolo[1,5-a]pyrid-2-ylamines 1 and
2 as low micromolar hits for PI3K with 5- to 10-fold selectivity
a family of dual lipid and protein kinases involved in the regulation
of numerous biological processes, including cell growth, differenti-
ation, survival, proliferation and migration.1 Class IA comprises
c
over PI3Kd and up to >30-fold selectivity over PI3K
a and PI3Kb
(Table 1).
PI3K
IB. PI3K
a
, PI3Kb and PI3Kd, while PI3K
c
is the sole member of Class
We hypothesized that the exocyclic NH along with one of the
nitrogen atoms in the triazolopyridine core could form the classical
bi-dentate hydrogen bond donor-acceptor interaction with the
hinge region of the kinase.16,17 The pendant phenyl ring was iden-
tified as a suitable region for initial modification of the molecules,
and a medicinal chemistry program was initiated to explore the
SAR in this region.
Analogues at this position were readily accessible by means of a
Suzuki reaction on the acetylated 6-bromo-[1,2,4]triazolo[1,5-
a]pyrid-2-ylamine core 3. This could be prepared from 2-amino-
5-bromopyridine 4 in 4 steps18 and allowed rapid access to
analogues 5 enabling exploration of the SAR around the aryl ring.
Modification of the synthesis by forming the boronic ester 6
allowed coupling with a wider variety of aryl bromides and
chlorides (Scheme 1).19 The acetyl group could be removed by
treatment of 5 with acid to afford the amines 7. Substitution of
acetyl chloride with different electrophiles in step 1 allowed explo-
ration of alternative groups on the exocyclic amine. Modification to
the core could be achieved by use of alternative amino pyridines 4
as starting materials.
c
plays a key role in immune responses such as immune
cell migration2 and mast cell degranulation,3 and the genetic or
pharmacological inactivation of its kinase activity confers protec-
tion in murine models of inflammatory diseases.4 PI3K
a and PI3Kb
are key mediators of insulin signaling5 and are necessary during
development as genetic inactivation results in embryonic lethal-
ity.6,7 On the other hand, PI3K
c
knock-out mice are viable, fertile
and do not show any adverse phenotype8–10 making selective inhi-
bition of PI3K an attractive target for treatment of inflammatory
c
and autoimmune disorders.
A number of publications have disclosed small molecules tar-
geting PI3K
forts in the pharmaceutical industry to develop drugs selectively
targeting the PI3K isoform have been unsuccessful. We have re-
cently disclosed compounds 43 (CZC19945) and 53 (CZC24832)
c
over the Class IA isoforms,11,12 however thus far ef-
c
as potent PI3Kc inhibitors with high selectivity over the other Class
I isoforms.13 This report details their discovery through optimiza-
tion of HTS hits.
Screening of a kinase focused library14 comprising 16,000 com-
pounds in a high throughput chemoproteomics binding assay13,15
An array of molecules with diversely substituted phenyls was
synthesized in the N-acetyl series. The set examined the effect of
changing the regiochemistry and nature of functional group to
⇑
Corresponding author.
E-mail address: ksmelt@onetel.com (K. Bell).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.06.049

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K. Bell et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5257–5263
Table 1
PI3Kc hits from HTS
O
N
NH
N
N
R
Compd #
R
PI3K
c
pIC50
PI3Kd pIC50
PI3K
a
pIC50
PI3Kb pIC50
1
2
2-OMe
3,5-diMe,4-OH
5.4
5.7
4.5
5.2
<4
4.9
<4
4.7
Table 2a
Inhibition of PI3K
c
/d/
a
: aryls
N
N
NH
O
N
R
Compd
#
R
PI3K
pIC50
c
PI3Kd
pIC50
PI3Ka
pIC50
8
9
3-OMe
4-OMe
3,4-diOMe
3-SO2Me
3-NHSO2Me
3-SO2NHMe
3-CONHMe
4-SO2Me
4-SO2NHMe
3-SO2NHnBu
3-SO2NHBn
5-(3-
6.8
6.0
7.4
6.3
6.5
6.6
6.2
<4
<4.3
6.7
6.3
<4.7
<4.1
4.5
5.7
5.5
5.3
6.0
<4
<4
<4
5.9
5.2
<4
<4.1
4.6
6.5
<4.3
5.3
<5
<4.3
<4
<4
10
11
12
13
14
15
16
17
18
19
5.0
<4
NA
Methyl)oxadiazole
3-Ph
3-SO2NHBn,4-OMe
Scheme 1. Reagents and conditions: (a) EtOC(O)NCS, DCM, 5–20 °C, 16 h; (b)
NH2OHÁHCl, DIEA, EtOH, MeOH, 1 h rt then 2 h reflux; (c) CH3COCl, Et3N, 5–20 °C,
16 h; (d) NH3, MeOH, rt, 16 h; (e) aryl-boronic acid, Pd(dppf)2Cl2ÁDCM, Na2CO3,
20
21
<5.4
<4
<4
<5
<4.7
<4
DME, H2O, EtOH, 120 °C (l-wave), 30 min; (f) Bis(pinacolato)diboron, toluene,
Pd(dppf)2Cl2ÁDCM, KOAc, 100 °C, 16 h; (g) Aryl bromide, Pd(dppf)2Cl2ÁDCM, Na2CO3,
DME, H2O, EtOH, 120 °C ( -wave), 30 min; (h) 4 M HCl in dioxane, rt, 18 h.
l
binding. Combination of the potent 3-sulfonamide with a 4-meth-
oxy substituent, 21 afforded an inactive molecule.
explore the requirements of the binding pocket. Compounds were
screened for binding affinity to PI3K , along with the closest off-
target PI3Kd and the unwanted PI3K , using a chemoproteomic
binding assay.15 Cellular activity of the more potent compounds
was assessed in a PI3K -dependent cellular C5a-induced AKT
A number of heterocyclic substituents at C-6 of the core were
also explored (Table 2b). The 3-pyridine 22 was identified as a sub-
micromolar inhibitor with greater than 60-fold selectivity over
c
a
PI3Kd and PI3Ka. Other heterocycles such as the pyrimidine 23
c
and isoquinoline 24 were around 10-fold less active as was the
4-pyridine 25. A number of 5-membered heterocycles including
dimethylthiazole 26 and pyrazole 27 were similarly 10- to 30-fold
less active. The only other heterocycle tested which retained high
Ser473 phosphorylation assay (pAKT) and an fMLP neutrophil
migration assay (NeuMig).13
The 3-methoxy and 4-methoxy phenyl regioisomers 8 and 9
showed increased binding affinity for PI3K
c
compared to the
affinity for PI3K
high affinity for the unwanted PI3K
general increased binding affinity to PI3K
logues (Table 2b). The 5-methoxy pyridine, 29 was around fivefold
more potent than its aryl analogue and while the sulfone and sul-
fonamides 30–32 showed a 10- to 30-fold increase in potency.
c
was thiophene, 28 but this analogue also showed
. 5-substituted-3-pyridines in
over the phenyl ana-
screening hit 1, whilst maintaining selectivity over the other
PI3K isoforms (Table 2a). The 3,4-dimethoxy analogue, 10 was
even more potent but showed a decrease in selectivity, particularly
a
c
over the unwanted PI3Ka. When larger functional groups were
investigated a clear preference was shown for C-3 rather than C-
4 substitution. Sub-micromolar activity was achieved with methyl
sulfones, sulfonamides and amides 11–14 at C-3 whereas the 4-
substituted isomers 15 and 16 were completely inactive. Larger
sulfonamides at C-3 such as n-butyl 17 and benzyl 18 could be
A crystal structure of the pyridine sulfone 30 in PI3K
c con-
firmed that it bound to the ATP binding pocket; the exocyclic NH
and N-1 of the triazolopyridine formed a bi-dentate hydrogen
bonding interaction with the protein backbone of Val882 in the
accommodated in the binding pocket but did not increase PI3K
c
hinge region of PI3Kc (Fig. 1). The triazolopyridine core and pen-
activity and as such afforded a decrease in the ligand efficiency
of the molecules. Aromatic rings directly attached to C-3 such as
the oxadiazole 19 and phenyl 20 were not tolerated suggesting
that the vector of the group at this position was important for
dant pyridine extended into a flat hydrophobic pocket achieving
efficient binding by means of multiple hydrophobic contacts. A
possible hydrogen bonding interaction was observed between
the sulfone and catalytic lysine (Lys833). The acetyl group

K. Bell et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5257–5263
5259
Table 2b
Inhibition of PI3Kc/d/a: heterocycles
N
NH
N
N
R
O
Compd #
R
Pyridin-3-yl
Pyrimidin-5-yl
Isoquinolin-4-yl
PI3K
c
pIC50
PI3Kd pIC50
PI3Ka pIC50
22
23
24
25
26
27
28
29
30
31
32
6.6
5.4
5.5
5.8
<4.9
5.4
6.4
7.2
7.1
7.4
8.1
<4.5
<4
<4
<4
<4
<4.0
<4.7
<5
5.3
5.5
<6
4.8
<4.8
<4
5.8
5.2
<4.2
6.7
<5.4
5.4
<5.5
<7
Pyridin-4-yl
2,4-Dimethylthiazol-5-yl
1-Methyl-1H-pyrazol-4-yl
Thiophen-3-yl
5-Methoxypyridin-3-yl
5-(Methylsulfonyl)pyridin-3-yl
5-N-Benzylpyridine-3-sulfonamide
5-(Methanesulfonamide)pyridin-3-yl
extended out towards solvent making it difficult to use the struc-
ture for exploration in this region.
involved in any key binding interactions in 30 we reasoned that
the amino analogue would retain binding affinity to PI3K . The
binding affinity of 33 to PI3K was not significantly different from
that of 30 (Table 3). Further analysis of the SAR on the RHS of the
molecule showed that larger acyl groups such as cylcohexylamide
c
Docking of 8 and 9 into a model built from the 4AOF crystal
structure afforded a very similar binding mode to the native ligand,
30. The small 4-methoxy substituent of compound 9 could be
accommodated within the pocket and was able to make a similar
hydrogen bonding interaction with Lys833 (Fig. 2).
c
maintained PI3Kc affinity 34 but lost selectivity for PI3Kd. Methyl-
ation of the NH 35 resulted in an inactive molecule, as expected
In the case of the 4-sulfonamide 15 and 4-sulfone 16 the steric
bulk of the larger groups forced the pendant phenyl ring out of the
hydrophobic binding pocket resulting in reduced surface burial
and hence lower binding affinity (Fig. 3). Docking of the 2-
methoxyphenyl hit, compound 1, showed that the increased dihe-
dral angle between the phenyl ring and bicyclic core caused by the
ortho substitution, forced the molecule away from the hinge rela-
from the crystal structure of 30. Mono 36 and di-methylation 37
of 33 led to a reduction in PI3Kc activity. A methylsulfonamide
38 was also prepared; however this was completely inactive
against all Class I PI3K isoforms tested.
Testing of compounds 30 and 33 in the pAKT and neutrophil
migration assays showed that the increased binding affinity con-
ferred by the pyridine ring did not translate into a concomitant in-
crease in cellular potency, the pyridine analogues being only
marginally more active in cells than compound 11 (Table 4).
We postulated that the very low clogP values of 30 and 33 of
À0.3 and À0.4, respectively may be limiting the cellular permeabil-
ity. A further array of analogues was prepared in the 2-amino ser-
ies, increasing lipophilicity of the R1 substituent with the aim of
tive to 30 thus accounting for the lower affinity for PI3Kc.
Compound 30 exhibited high in vitro stability in human, rat and
mouse microsomes with a half life >45 min in all species; however
a rat PK study showed it to be rapidly cleared in vivo. Metabolic id
studies in vivo on the related analogue 17 showed loss of the acetyl
group to be a major metabolic pathway. As this group was not
Figure 1. Crystal structure of 30 in PI3Kc (PDB code 4AOF). Hydrogen bonding interactions between the hinge and 30; and Lys833 and 30 are depicted by dashed lines.

5260
K. Bell et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5257–5263
Figure 2. Docking of compound 9 (green) into 4AOF, overlaid with the native ligand, compound 30 (pink).
Figure 3. Docking of compound 15 (blue) 4AOF, overlaid with the native ligand, compound 30 (pink). Compound 15 no longer makes optimal hydrophobic interactions with
the binding pocket.
improving cellular permeability (Table 5). N-linked and S-linked
sulfonamides were chosen for initial investigations in preference
to the sulfones as synthetic tractability enabled a more rapid
exploration of the SAR. The lipophilic N-linked aryl sulfonamides
were typically less potent such as the tert-butyl sulfone 46 which
was almost 10-fold less potent that 43.
Modeling studies of 43 suggested that this may be due to a po-
tential hydrogen bonding interaction between the NH of the sul-
fonamide and conserved Asp964 of the DFG unit which cannot
be achieved in the sulfones (Fig. 4). In addition the docking mode
also showed a potential hydrogen bonding interaction between
the pyridine nitrogen and side chain of Tyr867 not present in the
crystal structure of compound 30.
Both the tert-butylsulfonamide 43 and iso-propylsulfonamide
44 showed high stability in human, mouse and rat microsomes
with a half life >45 min in all species. 43 was further characterized
39 and 40 afforded highly potent PI3Kc binding and showed prom-
ising activity in the pAKT assay however low activity was observed
in the neutrophil migration assay possibly attributable to high
plasma protein binding (>99%). The S-linked aryl sulfonamides 41
and 42 showed only weak PI3K
kyl sulfomanides 43–45 showed intermediate PI3K
c
binding; however the S-linked al-
binding affin-
c
ity and in the case of 43 and 44 sub-micromolar cellular activity in
the neutrophil migration assay. The best alkyl-sulfonamides
groups were prepared as their sulfone analogues; however they
using mass spectrometry based profiling against
a panel of

K. Bell et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5257–5263
5261
Table 3
Inhibition of PI3Kc/d/a: RHS
R2
N
N
N
R3
N
X
R1
Compd #
R1
SO2Me
SO2Me
NHSO2Me
SO2Me
SO2Me
SO2Me
SO2Me
X
R2
R3
PI3K
c
pIC50
PI3Kd pIC50
PI3Ka pIC50
30
33
34
35
36
37
38
N
N
CH
CH
N
H
H
H
Me
H
Ac
H
7.1
7.0
6.5
<4.5
6.5
5.3
5.2
6.3
<4
<4.6
<4
5.4
5.0
<4
<4
<5.4
<4
CO(cyclohexyl)
Ac
Me
Me
N
N
Me
H
5.5
<4.4
SO2Me
<4
<4
Table 4
Cellular data
is not generally considered large enough to force an increase in the
dihedral angle between two aromatic rings.
Compd #
PI3K
c
pIC50
pAKT pIC50
NeuMig pIC50
High microsomal stability and good Caco2 data for 43 and 53
translated to low clearance and high bioavailability in a rat
in vivo PK study (Table 7); In addition compound 43 and 53
11
30
33
6.3
7.1
7.0
<4.9
<4.2
5.7
5.4
5.7
5.7
showed no inhibition in a hERG assay up to 100 l
M,22 nor CYP
inhibition up to 25 lM for CYP1A, 2C19, 2C9, 2D6 and 3A4 and
were negative in an Ames assay.23
kinases.20 High selectivity was observed across the protein kinases;
however the compound was shown to have only 10-fold selectivity
over PI3Kb.21
When evaluated in a mouse Collagen Induced Arthritis (CIA)
model 43 and 53 significantly reduced the severity and develop-
ment of arthritis. Mice treated orally with 10 mg/kg test compound
showed a reduction in the average clinical score of 53% and 38% for
43 and 53, respectively.13,24 53 exhibited poor thermodynamic sol-
We explored the SAR around the [1,2,4]triazolo[1,5-a]pyridine
core by addition of methyl groups in the 5, 7 and 8 positions to
identify where substituents could be tolerated in order to further
modify the physical properties of the molecules. Methyl groups
were tolerated at C-8 47 but not ortho to the pyridyl ring at C-7
48 or C-5 49 (Table 6). This fitted with our binding hypothesis
for compound 1 in which ortho substituents increase dihedral an-
gle between the bicyclic core and pyridyl ring meaning the mole-
cule cannot not be readily accommodated in the binding pocket.
Lipophilic substituents were subsequently explored at C-8 position
with the aim of increasing cellular permeability. The more lipo-
philic groups, trifluoromethyl 50 and chloro 51 resulted in a loss
of binding activity; however the 8-fluoro analogue 52 retained
sub micromolar activity. The fluorine was combined with our pre-
ferred tert-butyl sulfonamide to afford 53. The addition of the fluo-
rine did not increase cellular potency however the molecule did
show unexpected improved selectivity over PI3Kb. The 7-fluoro
analogue 54 was completely inactive despite the fact that fluorine
ubility (<5
lg/mL) and its measured pKa’s of 11 and 1.4 precluded
salt formation which made pre-clinical development problematic;
however 43 showed improved solubility (9 lg/mL) and its calcu-
lated pKa’s of 10 and 4.225 suggested that salt formation would
be feasible and thus despite its limited PI3Kb selectivity it may
have potential for further development as a PI3K
In summary, we have described the identification and SAR
around a new class of PI3K inhibitors. The 6-aryl triazolopyridines
43 (CZC19945) and 53 (CZC24832) have been shown to be potent
inhibitors of PI3K with good in vivo PK profile and have demon-
strated efficacy in chronic model of inflammation. Both
compounds show high selectivity over PI3K and 53 is almost
c inhibitor.
c
c
a
a
100-fold selective over PI3Kb and PI3Kd, making them important
compounds for investigating the effects of inhibiting the various
Class I PI3Ks in vivo.
Table 5
Inhibition of PI3Kc/d/a, cellular data and clogP vaules: amines
N
NH2
N
N
N
R1
Compd #
R1
PI3Kc
pIC50
PI3Kd pIC50
PI3K
a
pIC50
pAKT pIC50
NeuMig pIC50
clogP
39
40
41
42
43
44
45
46
Naphthalene-1-sulfonamide
NHSO2(4-ClPh)
SO2NH(4-ClPh)
SO2NHBn
8.1
8.2
6.2
6.6
7.6
7.5
7.8
6.8
6.9
6.4
5.2
5.1
5.8
5.8
<5.2
5.5
<7.0
6.8
5.4
<4.7
5.6
5.6
6.3
5.7
<4.9
5.9
5.7
5.8
5.7
<5
4.7
4.8
NA
5.1
6.0
6.2
5.8
NA
2.8
2.5
2.9
2.2
1.7
1.3
1.4
0.8
SO2NHtBu
SO2NHiPr
SO2NHCH2Cyclopropyl
5.5
<4.8
SO2tBu

5262
K. Bell et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5257–5263
Figure 4. Docking of compound 43 into PI3Kc (4AOF). Hydrogen bonding interactions are shown with dashed lines.
Table 6
Inhibition of PI3K
c/d/
a
/b: core substituents
R1
8
5
R3
NH
N
N
7
N
N
O
S
R2
O
Compd #
R1
R2
R3
PI3K
c
pIC50
PI3Kd pIC50
PI3K
a
pIC50
PI3Kb pIC50
47
48
49
50
51
52
53
54
8-Me
7-Me
5-Me
8-CF3
8-Cl
8-F
Me
Me
Me
Me
Ac
Ac
Ac
H
H
Ac
H
7.0
<4
6.0
<4
5.7
6.9
7.6
4.6
<5.3
<4
<4.4
<4
<4.4
<4
<4
<4
<4
<4.7
<5
<4
4.7
3.7
4.6
NA
<4
4.7
5.9
<4
Me
<4
Me
<4.7
5.1
<4
8-F
7-F
NHtBu
NHtBu
H
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37
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Acknowledgements
We are grateful to the biology and biochemistry groups for as-
say development and screening, Thilo Werner and the MS group
for compound profiling; Dave Middlemiss for medicinal chemistry
advice and Tammy Ladduwahetty for advice on the preparation of
the manuscript.
References and notes
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5263
14. The hits 1 and 2 were included in a library purchased from BioFocus.
15. Bergamini, G.; Cansfield, A.; Ramsden, N.; Neubauer, G. PCT Int. Appl.
WO2008015013.
22. Herg testing was performed at Neurosolutions, Cambridge in a Q-patch assay.
23. Neither toxicity nor mutagenic activity has been observed at 1667 g/plate
l
(compound precipitation observed at higher concentrations) in 3 Samonella
typhimurium strains (TA100, TA1537, TA98 liver S9 fraction).
16. Liao, J-L. L. J. Med. Chem. 2007, 50, 409.
17. Backes, A. C.; Zech, B.; Felber, B.; Klebl, B.; Müller, G. Expert Opin. Drug Discov.
2008, 3, 1409.
24. The Collagen Induced Arthritis (CIA) mouse model was carried out at Bolder
BioPath (Colorado). Male mice of DBA/B10 strain were injected intradermally
18. Wilson, F.; Ramsden, N.; Bell, K.; Cansfield, A.; Burckhardt, S.; Taylor, J.; Sunose,
M.; Middlemiss, D. PCT Int. Appl. WO2008025821.
with bovine type II collagen at day
inflammation 3–5 weeks after the first collagen injection.
0
(boost at day 21). Mice develop
chronic
A
19. Ramsden, N.; Bell, K.; Cansfield; Taylor, J.; Sunose, M.; Middlesmiss, D.;
Neubauer, G. PCT Int. Appl. WO2009068482.
20. Bantscheff, M.; Eberhard, D.; Abraham, Y.; Bastuck, S.; Boesche, M.; Hobson, S.;
Mathieson, T.; Perrin, J.; Raida, M.; Rau, C.; Reader, V.; Sweetman, G.; Bauer, A.;
Bouwmeester, T.; Hopf, C.; Kruse, U.; Neubauer, G.; Ramsden, N.; Rick, J.;
Kuster, B.; Drewes, G. Nat. Biotechnol. 2007, 1035, 25.
inflammation in the joints of the animals is achieved within 7–10 days after
disease onset. The quantification of the clinical inflammation is done by scores
(0–5) which combines the measurement of the volume of several body parts,
for example digits, hind and fore limbs (pads and ankles/wrists swelling). The
compound was administered orally twice per day every 12 h (po, bid).
25. Calculation using ACD labs software.
21. Compound 44 was tested against an off-target panel which includes >150
kinases and other proteins. Lipid kinases: PIP4K2C, PIP4K2A and PI3Kb <30-
fold; Protein kinases: AAK1 <100-fold.