Bioorganic & Medicinal Chemistry Letters
Discovery of potent, selective small molecule inhibitors of
of type III phosphatidylinositol-4-kinase (PI4KIII
a-subtype
a
)
a
b
a
a,c
Piotr Raubo a, , David M. Andrews , Jennifer C. McKelvie , Graeme R. Robb , James M. Smith
,
⇑
Martin E. Swarbrick c, Michael J. Waring a
a AstraZeneca, Mereside, Alderley Park, Macclesfield SK10 4TG, UK
b Cancer Research Technology, London BioScience Innovation Centre, 2 Royal College Street, London NW1 0NH, UK
c Cancer Research Technology, Jonas Webb Building, Babraham Research Campus, Cambridge CB22 3AT, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The discovery and optimisation of novel, potent and selective small molecule inhibitors of the
of type III phosphatidylinositol-4-kinase (PI4K ) are described. Lead compounds show cellular activity
consistent with their PI4K potency inhibiting the accumulation of IP1 after PDGF stimulation and reduc-
ing cellular PIP, PIP2 and PIP3 levels. Hence, these compounds are useful in vitro tools to delineate the
complex biological pathways involved in signalling through PI4K
Ó 2015 Elsevier Ltd. All rights reserved.
a-isoform
Received 16 March 2015
Revised 28 May 2015
Accepted 29 May 2015
Available online 4 June 2015
a
a
a.
Keywords:
PI4K
a
In vitro tools
IP1
Oncology
Phosphatidylinositol-4-kinases (PI4Ks) catalyse the phosphory-
on cellular concentration of PI4P and PI(4,5)P2 and cellular prolifer-
ation in a panel of cancer cell lines.13 In this communication we
report the results of our work that led to the identification of
lation of phosphatidylinositol (PI) at the D4 position of the inositol
head-group to form phosphatidylinositol-4 phosphate (PI4P).1 PI4P
acts as a binding partner for a wide range of proteins with pleck-
strin homology (PH) or related lipid-binding domains.2,3 PI4P is
also an important signalling molecule as a precursor to other phos-
phoinositides such as phosphatidylinositol-4,5-diphosphate
PI(4,5)P2 and phosphatidylinositol-3,4,5-triphosphate PI(3,4,5)P3
(Scheme 1).3,4 Four PI4K isoforms have been identified in mammals
potent and selective small molecule inhibitors of PI4K
To optimise for suitable probe compounds that would allow us
to evaluate the effect of PI4K inhibition on the PI signalling
pathway, we first screened compounds against PI4K and b
Compounds active in PI4K were subsequently evaluated against
other related enzymes on the PI pathway, including PI3K /b/ /d
and PIP5K /b/ . Finally, with potent and selective PI4K inhibitors
a.
a
a
a
a
c
and are classified as type II (PI4KII
a
and b) and type III (PI4KIII
a
a
c
a
and b, hereafter referred to as PI4K
a
and b). PI4K is the main iso-
a
in hand, we assessed their effect on accumulation of inositol-1-
form responsible for PI4P generation at the plasma membrane and
is localised at the endoplasmic reticulum. PI4Kb is mainly associ-
ated with the Golgi complex where it functions in the generation
of Golgi-derived carriers.5 Recent reports suggest the implication
phosphate (IP1) in NIH3T3-PDGFRb cells.13
We identified the original PI4Ka-selective hit from a screen
against recombinant PI4Kb of approximately 100,000 compounds
selected from the AstraZeneca compound collection based on
structures known to have lipid kinase activity. Active compounds
from the screen then had their IC50 values determined against
of PI4Ka
and PI4P in viral replication.3,6
Pharmacological manipulation of cellular PI4P levels has been a
challenge due to the non-specificity and low potency of known
PI4K inhibitors such as wortmannin, LY294002 and phenylarsine
oxide7; although more recently, reports have emerged describing
PI4K inhibitors from several groups.8–12
PI4Kb and PI4Ka 14
From this screening campaign we identified a
.
moderately selective 2-aminobenzothiazole derivative 1 (Table 1)
as a promising starting point for further evaluation. To get more
detailed insight into structure activity relationships (SAR)
of 2-aminobenzothiazoles, we first investigated the effect of sub-
Recently, we disclosed two distinct series of potent and selec-
tive
a
- and b-subtype PI4K inhibitors and described their effect
stitution of the pyridine ring in 1 on PI4Ka potency and selectivity
(Table 1). Replacement of the ethoxy group with smaller
substituents such as 6-methoxy (2) or 6-methyl (10) led to
⇑
Corresponding author.
reduction of PI4Ka potency and selectivity over PI4Kb and PI3Ks.
0960-894X/Ó 2015 Elsevier Ltd. All rights reserved.