Further optimization of the mGlu5 PAM clinical candidate VU0409551/JNJ-46778212: Progress and challenges towards a back-up compound

Article abstract of DOI:10.1016/j.bmcl.2015.06.096

This Letter describes the progress and challenges in the continued optimization of the mGlu₅ positive allosteric modulator (PAM) clinical candidate VU0490551/JNJ-46778212. While many analogs addressed key areas for improvement, no one compound possessed the amalgamation of improvements needed within the (2(phenoxymethyl)-6,7-dihydrooxazolo[5,4-c]pyridine-5(4H)-yl(aryl)methanone scaffold to advance as a back-up clinical candidate. However, many analogs displayed excellent solubility and physiochemical properties, and were active in the amphetamine-induced hyperlocomotion (AHL) model. Moreover, the SAR was robust for this series of PAMs, and both polar and hydrogen-bond donors were found to be tolerated, leading to analogs with overall attractive profiles and good ligand efficiencies. Graphical abstract

Full text of DOI:10.1016/j.bmcl.2015.06.096

Bioorganic & Medicinal Chemistry Letters 25 (2015) 3515–3519
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Further optimization of the mGlu5 PAM clinical candidate
VU0409551/JNJ-46778212: Progress and challenges towards
a back-up compound
Ya Zhou a,b, Chrysa Malosh a,b, Susana Conde-Ceide c, Carlos Manuel Martínez-Viturro c, Jesus Alcázar c,
Hilde Lavreysen d, Claire Mackie e, Thomas M. Bridges a,b, J. Scott Daniels a,b, Colleen M. Niswender a,b
,
Carrie K. Jones a,b, Gregor J. Macdonald d, Thomas Steckler d, P. Jeffrey Conn a,b, Shaun R. Stauffer a,b
,
a,b,
José Manuel Bartolomé-Nebreda c, , Craig W. Lindsley
⇑
⇑
a Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
b Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
c Neuroscience Medicinal Chemistry, Janssen Research and Development, Jarama 75A, 45007 Toledo, Spain
d Neuroscience, Janssen Research and Development, Turnhoutseweg 30, B-2340 Beerse, Belgium
e Discovery Sciences ADME/Tox, Janssen Research and Development, Turnhoutseweg 30, B-2340 Beerse, Belgium
a r t i c l e i n f o
a b s t r a c t
Article history:
This Letter describes the progress and challenges in the continued optimization of the mGlu5 positive
allosteric modulator (PAM) clinical candidate VU0490551/JNJ-46778212. While many analogs addressed
key areas for improvement, no one compound possessed the amalgamation of improvements needed
within the (2(phenoxymethyl)-6,7-dihydrooxazolo[5,4-c]pyridine-5(4H)-yl(aryl)methanone scaffold to
advance as a back-up clinical candidate. However, many analogs displayed excellent solubility and phys-
iochemical properties, and were active in the amphetamine-induced hyperlocomotion (AHL) model.
Moreover, the SAR was robust for this series of PAMs, and both polar and hydrogen-bond donors were
found to be tolerated, leading to analogs with overall attractive profiles and good ligand efficiencies.
Ó 2015 Elsevier Ltd. All rights reserved.
Received 18 May 2015
Revised 24 June 2015
Accepted 26 June 2015
Available online 4 July 2015
Keywords:
mGlu5
Metabotropic glutamate receptor
Positive allosteric modulator (PAM)
Pharmacokinetics
Schizophrenia
We recently disclosed the discovery and development of an
orally bioavailable mGlu5 PAM (1, VU0409551, JNJ-46778212)1,2
for the treatment of schizophrenia (Fig. 1) via a fundamentally
new molecular mechanism,3–6 arising from a unique industrial-
academic collaboration between Janssen Research and
Development and the Vanderbilt Center for Neuroscience Drug
Discovery (VCNDD).7–13 Immediately following its approval as a
clinical candidate, we pursued a multidimensional optimization
campaign (surveying modifications to the eastern and western aryl
moieties as well as the central piperidine ring, Fig. 1) towards the
discovery of a back-up compound within the (2(phenoxymethyl)-
6,7-dihydrooxazolo[5,4-c]pyridine-5(4H)-yl(aryl)methanone
series.1,2 The optimization plan focused on blocking CYP-mediated
aryl oxidation2 and improving physiochemical properties of the
scaffold, all in an effort to identify analogs with increased potency
and increased efficacy in an amphetamine-induced hyperlocomo-
tion (AHL) rodent model.
In order to access analogs of 1 and survey the SAR for the high-
lighted regions depicted in Figure 1, two synthetic routes were
developed. In the first approach (Scheme 1), the 4-fluorophenyl
benzamide of 1 was maintained while alternative aryl and hetero-
aryl phenolic moieties were introduced. Treatment of 1 with BBr3
liberates the primary alcohol 3, which readily participates in
Mitsunobu reactions to deliver analogs 4 in good overall yields.
To access analogs of 1 with greater structural variance, we begin
with various, commercial piperidinones
5
(Scheme 2).
Bromination provides 6 which, upon treatment with cinnamamide
in the presence of silica gel and heat, affords styrenyloxadiazole 7
in 25% yield for the two steps. Then, a three step sequence of oxi-
dation, cleavage and reduction provides alcohol 8 in 40% over the
three steps. Mitsunobu reaction with various phenols and hetero-
aryl alcohols, followed by hydrolysis of the ethyl carbamate, gives
secondary amine 9. Standard acylation chemistry then provides
analogs 10 in good to excellent yields.
⇑
Corresponding authors.
E-mail addresses: jbartolo@its.jnj.com (J.M. Bartolomé-Nebreda), craig.lindsley@
vanderbilt.edu (C.W. Lindsley).
http://dx.doi.org/10.1016/j.bmcl.2015.06.096
0960-894X/Ó 2015 Elsevier Ltd. All rights reserved.

3516
Y. Zhou et al. / Bioorg. Med. Chem. Lett. 25 (2015) 3515–3519
O
O
CYP
[O]
O
N
O
N
N
N
O
HO
O
F
F
2
1
, M1
mGlu5 EC50 > 10 µM
, VU0409551/JNJ-46778212
mGlu5 EC50 = 260 nM, 74% Glu Max
O
add groups to
block [O]
O
N
alternate benzamides
heterocycles
N
O
heterocycles
F
introduce methyl groups
Figure 1. Structures and mGlu5 PAM activities of the clinical candidate
multidimensional optimization back-up campaign for 1.
1
(VU0409551/JNJ-46778212) and the inactive, primary metabolite 2 (M1). Inset, the
O
O
O
O
N
N
a
b
1
N
(Het)ArO
N
HO
F
F
3
4
Scheme 1. Reagents and conditions: (a) BBr3, DCE, 0 °C, 65%; (b) (Het)ArOH, DBAD, PPh3, THF, 0 °C to rt, 20 min, 35–90%.
R1
R1
R1
O
N
NCO2Et
NCO2Et
NCO2Et
a
b
Ph
O
O
Br
R1 = H or CH3
5
6
7
R1
R1
O
N
O
e
NCO2Et
c
d
NH
HO
N
(Het)ArO
8
9
O
R1
O
N
N
Ar (Het)
(Het)ArO
10
Scheme 2. Reagents and conditions: (a) Br2, HBr (cat), THF, 0 °C to rt, 30 min; (b) cinnamamide, SiO2, 125 °C, 16 h, 25% over two steps; (c) (i) OsO4 (cat), NMO THF/acetone/
H2O, rt 16 h, (ii) NaIO4, THF/MeOH/H2O, rt, 2 h, (iii) NaBH4, MeOH, 0 °C to rt, 30 min, 40% for three steps; (d) (i). (Het)ArOH, DBAD, PPh3, THF, 0 °C to rt, 30 min, (ii) LiOH,
dioxane/H2O, 170 °C, 40 min, mw, 25–44% for two steps; (e) (Het)ArCOCl, DEIPA, DCM, 0 °C to rt or (Het)ArCO2H, PyBrOP, DCE, rt, 56–95%.
With respect to analogs 4, SAR was flat, with most substituted
aryl moieties proving to be inactive, with the notable exception
of fluoro congeners and certain pyridyl isomers (Table 1). Clear
SAR was noted for the fluoro derivatives, with the 3-fluoro phenyl
4b being a clear standout in terms of both mGlu5 PAM potency
(EC50 = 240 nM), efficacy (78% of the maximal response of gluta-
mate) and leftward fold-shift of a full glutamate concentration-re-
sponse curve (13Â). The 4-fluoro analog 4c lost potency, and when
combined, the 3,4-difluoro congener 4d lost significant efficacy.
Similarly, pyridyl regioisomers displayed either no activity (e.g.,
4e, the 3-pyridyl) or a loss of potency as with 4f and 4g. Based
on these data, we further evaluated 4b in a battery of in vitro
DMPK assays.1,2 4b possessed a clean P450 inhibition profile (IC50
>30 lM against 3A4, 2D6, 2C9 and 1A2), displayed acceptable frac-
tion unbound values in human (fu, 0.018) and rat (fu, 0.049) as well
as an attractive cardiovascular safety pharmacology profile (hERG
PX 26%@10
Addition of the 3-fluoromoeity to 1 negatively impacted solubility
(FaSSIF and SGF both 10 g/mL), and quite unexpectedly, this sin-
gle atom modification brought in mGlu3 antagonist activity (mGlu3
IC50 = 410 nM, 8% Glu min, >10
M vs mGlu1,2,4,6,7,8).14,15 Still,
lM, IC50s >10 lM at hERG, Ca and Na channels).
l
l
based on excellent brain penetration (Kp = 2.7), we evaluated 4b
in our standard rodent (rat) pharmacodynamic model for the pro-
gram, and 4b (VU0413846) produced a dose- and concentration-
dependent reversal of amphetamine induced hyperlocomotion
upon oral administration (Fig. 2), displaying a maximum reversal

Y. Zhou et al. / Bioorg. Med. Chem. Lett. 25 (2015) 3515–3519
3517
Table 1
as a potential back-up candidate. However, the 3-flurophenyl moi-
ety was worthy of evaluation in the context of alternate benza-
mides, 10. Here, robust SAR was observed (Table 2), but in all
cases both solubility and efficacy in AHL were greatly diminished
relative to 1.1,2 Therefore, we elected to focus the back-up effort
on analogs of 1 wherein the western, unsubstituted phenoxy moi-
ety was maintained, while surveying heterocyclic amides to
enhance solubility, providing congeners 11 (Table 3). The vast
majority of 5- and 6-membered heterocycles surveyed lost consid-
erable mGlu5 PAM potency, efficacy or both; however, certain
indoles, indazoles and aza-indazoles, proved to be highly interest-
ing compounds. While the 2-indoyl amide 11a was inactive, the N–
Me congener 11b was active (EC50 = 510 nM); in contrast, 3-indoyl
amides, both the N–H (11c) and N–Me (11d) derivatives, were
comparably active (EC50s of 230 nM and 290 nM, respectively).
Moreover, the indazole analog 11e was equipotent to the indole
11c, yet both displayed poor solubility. Surveying azaindole ana-
logs, 11f–h, led to the discovery of 11h, an mGlu5 PAM with mod-
erate potency (EC50 = 546 nM) and good efficacy (73% Glu Max),
Structures and activities of analogs 4
O
O
N
N
(Het)ArO
F
4
a
a
Entry
R
pEC50 ( SEM)
EC50 (nM)
Glu max%a ( SEM)
F
4a
5.92 0.06
1200
78
3
F
4b
4c
6.62 0.02
6.18 0.03
240
660
78
73
2
4
F
F
but with exceptional solubility (FaSSIF of 381
ranted further characterization.
lg/mL) which war-
4d
6.19 0.09
640
40
6
5
mGlu5 PAM 11h showed comparable activity at both human
and rat receptors, along with fold-shifts of equal magnitude (7.3–
9.3Â) with modest ago-PAM activity. 11h was a low molecular
weight compound (375), possessed a favorable log P (2.4) and high
ligand efficiency (0.31). Unlike 4b, 11h was inactive against all the
mGlus (>30 lM versus mGlu1–4,6–8) and displayed improved
plasma protein binding (fu (h,r): 0.04, 0.11). Other in vitro DMPK
properties were also favorable, including clean P450 inhibition
profile (IC50 P30 lM against P4503A4, 2D6 and 1A2; 14.8 lM at
F
N
4e
4f
5.61 0.05
<5b
2460
75
40
N
N
>10,000
4g
5.76 0.03
1700
71
2
2C9), and a moderate predicted hepatic clearance (CLhep (h,r);
a
Calcium mobilization assay using HEK293 expressing human mGlu5; values are
the average of three or more independent determinations.
b
Data obtained from a single experiment; not replicated.
Table 2
Structures and activities of analogs 10
O
F
O
N
N
Ar
O
10
a
a
Entry
R
pEC50 ( SEM)
EC50 (nM)
290
Glu max%a ( SEM)
10a
6.53 0.07
73
75
5
3
F
10b
10c
6.85 0.05
6.21 0.10
139
620
F
F
F
72
71
4
5
10d
10e
6.65 0.06
6.82 0.04
220
150
F
F
Figure 2. 4b (VU0413846) has antipsychotic-like activity in male, Sprague Dawley
rats. 4b dose-dependently (3–100 mg/kg, po) reverses AHL. Vehicle is 20% beta-
cyclodextrin (homogeneous solutions).
42
82
3
4
F
F
of 37% at 56.6 mg/kg (terminal (1.5 h) plasma and brain concentra-
tions in this study were linear by dose from 3 to 30 mg/kg, sublin-
ear from 30 to 56.6 mg/kg, and flat from 56.6 to 100 mg/kg).
With a relatively high minimum effective dose (of (30 mpk),
diminished solubility (3Â lower than 1),1,2 lack of mGlu selectivity
and modest in vivo efficacy precluded further advancement of 4b
10f
6.49 0.06
370
F
a
Calcium mobilization assay using HEK293 expressing human mGlu5; values are
the average of three or more independent determinations.

3518
Y. Zhou et al. / Bioorg. Med. Chem. Lett. 25 (2015) 3515–3519
Table 3
Structures and activities of analogs 11
O
O
N
Het
N
O
11
pEC50 ( SEM)
a
a
Entry
R
EC50 (nM)
Glu max%a ( SEM)
40
11a
<5b
>10,000
510
N
H
11b
11c
6.29 0.1
57
71
4
6
N
Me
6.63 0.06
230
N
H
11d
11e
11f
6.53 0.09
6.53 0.06
<5b
290
70
68
29
53
73
3
4
N
Me
290
N
N
H
N
>10,000
1400
546
N
N
H
N
11g
11h
5.85 0.10
6.26 0.02
5
2
N
N
H
N
N
N
H
a
Calcium mobilization assay using HEK293 expressing human mGlu5; values are the average of three or more independent determinations.
Data obtained from a single experiment not replicated.
b
9.1, 36 mL/min/kg). These attractive in vitro properties translated
in vivo, with 11h displaying low plasma clearance in rat
(CLp = 12.8 mL/min/kg), a moderate half-life (3.6 h), excellent oral
bioavailability (%F = 85) and CNS penetration (Kp = 1.2). In our
standard rodent AHL pharmacodynamic model (Fig. 3),1,2 11h
demonstrated efficacy with oral dosing, but the MED was 30 mg/kg
p.o. (3-fold higher than for 1, and the same as 4d). The ED50 was
17.7 mg/kg, and the maximum reversal was 48.8% at a dose of
56.6 mg/kg (terminal (1.5 h) plasma and brain concentrations in
this study were linear by dose from 3 to 30 mg/kg and sublinear
from 30 to 56.6 mg/kg). Thus, like 4d, 11h proved to not possess
the profile necessary to advance as a clinical back-up to 1.
Before abandoning the (2(phenoxymethyl)-6,7-dihydrooxa-
zolo[5,4-c]pyridine-5(4H)-yl(aryl)methanone series, we elected to
evaluate the impact of the addition of methyl groups to the core
piperidine nucleus as outlined in Figure 1, via the route depicted
in Scheme 1. For this exercise, we employed 1 as our scaffold of
reference (Fig. 4). Only one analog (15) proved more potent than
Figure 3. 11h (VU0457481) has antipsychotic-like activity in male, Sprague Dawley
rats. 11h dose-dependently (3–56.6 mg/kg, po) reverses AHL. Vehicle is 20% beta-
cyclodextrin (homogeneous solutions).
1
(EC50 = 170 nM, pEC50 = 6.76 0.01, 73 2%); however, this
structural modification did not lead to improvements in

Y. Zhou et al. / Bioorg. Med. Chem. Lett. 25 (2015) 3515–3519
3519
O
O
N
N
O
F
F
12, mGlu5 EC50 = 750 nM, 70%
O
O
N
N
O
O
13, mGlu5 EC50 = 510 nM, 61%
O
N
N
O
O
F
O
N
1, VU0409551/JNJ-46778212
mGlu5 EC50 = 260 nM, 74%
N
O
F
F
14, mGlu5 EC50 = 520 nM, 72%
O
O
N
N
O
15, mGlu5 EC50 = 170 nM, 73%
Figure 4. Impact of incorporation of either a racemic methyl or gem-dimethyl moiety into the piperidine core of 1, providing analogs 12–15.
Menges, A.; Niswender, C. M.; Jones, C. K.; Macdonald, G. J.; Steckler, T.; Conn, P.
J.; Stauffer, S. R.; Bartolome-Nebreda, J. M.; Lindsley, C. W. ACS Med. Chem. Lett.
2015, 6, 716.
physicochemical or DMPK properties, and thus, future efforts in
this subseries were not pursued.
In summary, we have detailed our initial efforts towards a
back-up compound for the mGlu5 PAM clinical candidate (1,
VU0409551/JNJ-46778212) while working within the (2(phe-
noxymethyl)-6,7-dihydrooxazolo[5,4-c]pyridine-5(4H)-yl(aryl)-
methanone series. Robust SAR was observed within this series,
which led to the discovery of two putative contenders, 4b and
11h, that individually addressed some of the areas targeted for
improvement with 1. Despite some notable advances, both 4b
and 11h displayed diminished MEDs in our pivotal AHL model
and were deemed not suitable for further advancement as back-
up candidates. Efforts have shifted toward other chemical series
and chemotypes from which to develop a back-up candidate, and
these efforts will be reported in due course.
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We thank William K. Warren, Jr. and the William K. Warren
Foundation who funded the William K. Warren, Jr. Chair in
Medicine (to C.W.L.).
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