Bioorganic & Medicinal Chemistry Letters 24 (2014) 737–741

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Heteroarylureas with spirocyclic diamine cores as inhibitors of fatty acid amide hydrolase John M. Keith ⇑, William M. Jones, Joan M. Pierce, Mark Seierstad, James A. Palmer, Michael Webb, Mark J. Karbarz, Brian P. Scott, Sandy J. Wilson, Lin Luo, Michelle L. Wennerholm, Leon Chang, Sean M. Brown, Michele Rizzolio, Raymond Rynberg, Sandra R. Chaplan, J. Guy Breitenbucher Janssen Research and Development, L.L.C., 3210 Merryfield Row, San Diego, CA 92121, USA

a r t i c l e

i n f o

Article history: Received 22 November 2013 Revised 23 December 2013 Accepted 27 December 2013 Available online 6 January 2014 Keywords: FAAH Hydrolase Covalent inhibitor Spirocycles

a b s t r a c t A series of mechanism based heteroaryl urea fatty acid amide hydrolase (FAAH) inhibitors with spirocyclic diamine cores is described. A potent member of this class, (37), was found to inhibit FAAH centrally, elevate the brain levels of three fatty acid ethanolamides [FAAs: anandamide (AEA), oleoyl ethanolamide (OEA) and palmitoyl ethanolamide (PEA)], and was moderately efficacious in a rat model of neuropathic pain. Ó 2014 Elsevier Ltd. All rights reserved.

The fatty acid amide hydrolases (FAAH and FAAH-2)1 are responsible for the degradation of a variety of endogenous lipid signaling molecules. FAAH preferentially degrades fatty acid ethanolamide substrates and FAAH-2 more readily breaks down primary amides, though there is some substrate overlap between the two enzymes. These hydrolases are differentially distributed with FAAH being expressed primarily in the brain, liver, and white blood cells while FAAH-2 is found in various peripheral tissues. The preferred substrates of FAAH include N-arachidonyl ethanolamide2 (AEA or anandamide), N-palmitoyl ethanolamide (PEA)3 and Noleoyl ethanolamide (OEA).4 AEA is the most rapidly degraded substrate of the three and is an agonist of the cannabinoid receptor CB1,5 which is likely the source of its analgesic pharmacology. PEA is known to have anti-inflammatory properties and exert analgesic effects through a non-cannabinoid pathway,3 while OEA appears to be involved in regulating satiety.6 Because AEA is synthesized and broken down in a highly localized manner, side-effects associated with the dosing of exogenous CB1 agonists (the so-called cannabinoid tetrad) are not observed. When the mechanism of AEA breakdown is non-functioning, as in FAAH( / ) mice, administration of exogenous AEA led to a side-effects profile similar to that of D8 THC;7 likely a result of non-selective agonism of central CB1 receptors. AEA’s poor pharmacokinetic properties and short half-life in the presence of the

FAAH enzyme, makes it a poor candidate as an analgesic. However, inhibiting the FAAH enzyme should allow the potential pharmacological benefits of localized AEA elevation to be realized while bypassing broad systemic increases that would result from N

O N H

N

N H

N

0960-894X/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.bmcl.2013.12.113

N

S

Pfizer

JNJ-16610 10/Takeda N

O N H

Cl

N N

O

JNJ-40355003

Figure 1. Some known piperazinyl urea FAAH inhibitors.

N O

O

O N H

N

N

Pfizer

N

N H

N

Cl

O

F

Pfizer

O

N

CF 3

O N H

N

O O

E-mail address: [email protected] (J.M. Keith).

N

S N

F

⇑ Corresponding author.

O Me

N

Br

Amgen

Figure 2. Reported spirocyclic FAAH inhibitors.

738

J. M. Keith et al. / Bioorg. Med. Chem. Lett. 24 (2014) 737–741

Boc

n N

n n

n

HN

a, b

n

NH n

N n

O HetAr

levels in the plasma and brains8 of rats and the plasma of humans, thus supporting the hypothesis that the pharmacology associated with raised AEA levels should be in evidence upon administration of a FAAH inhibitor. We were interested in replacing the piperazinyl ring common to a class of FAAH inhibitors reported by us and others9 (Fig. 1) with a spirocyclic diamine template. Non-diamine spirocycles have been prepared by others that act as mechanism based10 and competitive11 inhibitors (Fig. 2). With this in mind, we prepared a series of FAAH inhibitors bearing spirocyclic diamine cores. The preparation of these compounds is described in Scheme 1. Most of the desired spirocyclic diamines were available commercially (mono-Boc or CBz protected) with the exception of 2,6-diazaspiro[3.3]heptanes, which we prepared using the method developed in Erick Carreira’s group.12 In order to efficiently screen spirocyclic cores, we elected to fix the heteroaryl urea functionality as 3-pyridyl and the pendent benzylic group as 3-(4-chlorophenoxy)benzyl, as both of these substituents were well tolerated on a piperazine core (see JNJ-40355003, Fig. 1 above). The results of the screen are shown in Table 1. The initial screen revealed several interesting compounds with reasonable potency at both the human and rat enzymes. We decided to follow up on 3 spirocyclic cores in a total of 4-different arrangements: 3,9-diazaspiro-[5.5]-undecane (5), 2,7-diazaspiro[3.5]-nonane (11 & 12) and 2,6-diazaspiro-[3.3]-heptane (13). With these cores, we retained the 3-(4-chlorophenoxy)benzyl group and varied the heteroaryl urea (Table 2). With each of the

A

O

O c

N H

Cl

n

HetAr

OPh

n N H

N

Cl

n n n

N

d e, a

O HetAr

n N H

N

n n

N n Boc

Scheme 1. Reagents and conditions: (a) spirocyclic diamine core (specifically defined in Table 1) 1.1 equiv 3-(4-chlorophenoxy)benzaldehyde, 2.0 equiv NaBH(OAc)3, 1.0 equiv Et3N (when amine
HCl salt is used), THF, 0 °C to rt, 15– 24 h, 44–99%; (b) 5 equiv 4 N HCl/1,4-dioxane, DCM, rt, overnight, 79–99%; (c) 1.0 equiv heteroaryl phenyl carbamate (heteroaryl groups specifically defined in Table 2), 2.0 equiv Et3N, DMSO, 55 °C, 15–24 h, 6–98%; (d) 2.0 equiv Et3N, 1.0 equiv Boc(or CBz)-diamine, DMSO, 55 °C, 15–24 h, 17–100% (e) 5.0 equiv 4 N HCl/1,4dioxane, DCM, rt, 15–24 h, 99–100%.

administration of a CB1 agonist. Indeed, prior reports have robustly demonstrated that inhibition of FAAH leads to an increase in AEA Table 1

N

O N H

Compd

rFAAH apparenta IC50s (nM)b

N

93 ± 36

493 ± 153

2

N

N

1333 ± 408

413 ± 20

3

N

2600 ± 1471

320 ± 117

1300 ± 141

710 ± 166

27 ± 1.2

287 ± 57

>10,000

8667 ± 1633

8667 ± 1633

1367 ± 163

>10,000

>10,000

N

>10,000

610 ± 252

N

6333 ± 2041

8000 ± 1414 243 ± 50

N

N N

5

N

6

N

N

N

N N

8

N

9

N

10

N

N

11

N

N

80 ± 34

12

N

N

265 ± 110

13

c

hFAAH apparenta IC50s (nM)b

N

7

b

O

1

4

a

Diamine Core

Cl

diamine core

N

N

Values obtained after a 60 min preincubation with the enzyme. Values are with n P 3 ± SEM. N = 2.

c

125 ± 5

148 ± 66 1367 ± 82

Table 2

O HetAr

Compd

14

HetAr group

N

N N

H N

N

N

Diamine Core N

N

N

N N

N

N

17

18

N

19

N N

N

N N

N

H N

N

N

N

N

HetAr group HN N N N

26 ± 4

38 ± 9

27

47 ± 4

86 ± 13

28

50 ± 6

30 ± 10

29

123 ± 15

5.3 ± 1.1

30

N

N

N

31 ± 10

30 ± 5

31

43 ± 3

133 ± 29

32

38 ± 13

33

N

N

900 ± 57

22 ± 1.8

N

N

N

N

N

151 ± 68

6000 ± 1414

5567 ± 1559

23 ± 7

38 ± 12

247 ± 94

225 ± 125

275 ± 75

333 ± 163

173 ± 53

535 ± 85c

127 ± 28

81 ± 28

553 ± 92

235 ± 29

393 ± 22

16 ± 5

8±2

9±0

18 ± 8c

42 ± 12c

N

N

N

F

N

N

260 ± 109

N

Cl

N

56 ± 6

N

N

Cl

N

21

N

N

rFAAH apparenta IC50s (nM)b

N

N

N

hFAAH apparenta IC50s (nM)b

3250 ± 750

N

Ph

Diamine Core N

N

N

N

66 ± 24

N

O

Compd

N

20 O N

rFAAH apparenta IC50s (nM)b

N

N

34 Me

O N

N

N

N

22

177 ± 47

20 ± 7

N N

23

N

N

35

J. M. Keith et al. / Bioorg. Med. Chem. Lett. 24 (2014) 737–741

O N

N

Cl

diamine core

N

15

16

hFAAH apparenta IC50s (nM)b

N H

CF3

N

N

N

300 ± 57

N

28 ± 8

N

N

36 CN

N

24

N

N O N

N

N

N N

333 ± 11

11 ± 2.8

N

N

37 Cl

N

N

N

840 ± 228

25

807 ± 207

38

N

N

Cl HN N

26 a

c

N

5800 ± 2581

Values obtained after a 60 min preincubation with the enzyme. Values are with n P 3 ± s.e.m. N = 2.

1700 ± 300

739

b

N

740

J. M. Keith et al. / Bioorg. Med. Chem. Lett. 24 (2014) 737–741

Table 3

JNJ-42119779 Spinal Nerve Ligation Mechanical Allodynia

a

11 16a 18a 5b

Cl (L/kg/h)

Vss (L/kg)

T1/2 (h)

F (%)

10.4 2.55 1.0 2.26

21.8 11.3 2.21 18.0

1.68 3.35 1.81 5.69

32 62 71 69

JNJ-42119779 (p.o., 20 mg/kg, n=6) Vehicle (p.o., water, 2 mL/kg, n=6) JNJ-40355003 (p.o., 60 mg/kg, n=3) 100

p < 0.05 overall 75

PK data for selected compounds: male Sprague–Dawley rats 0.5 mg/kg iv, 2.0 mg/kg p.o. (n = 3 each). a 1:4:15 pharmasolve/cremaphore, D5W. b 50% peg 400/water.

MPE (%)

Compd

50 25 0 -25 Baseline

1

2

3

4

Post-treatment time (hrs)

Compound exposure of JNJ-42119779 after oral dosing

Figure 5. Profile of JNJ-42119779 (37) in the spinal nerve ligation (Chung) model of neuropathic pain.

(20 mg/kg in H2O, n=3)

Compound (µM)

3

Plasma Brain

2

1

0 0

1

2

3

4

Time post-dose (hrs) Figure 3. Brain and plasma exposures for JNJ-42119779 (37) after a 20 mg/kg oral dose (vehicle = water).

Ex vivo brain FAAH activity after oral dosing of JNJ-42119779 (20 mg/kg in H 20, n=3) 125

% of Control

100 75 50 25

e os

e po

st -d

os s hr

hr

4

1

s in 30

m

po

po

le ic Ve h

st -d

st -d

co n

os

tr ol

e

0

125

Pre-dialysis Post-dialysis at 4°C Post-dialysis at room temperature

100 75 50 25

21 19 77 9 JN

nM 10 0

12 0

nM

JN

J-

nM

O

L-

To 50

J4

13 5

16 61 01 0

0 ta l

% activity of vehicle control

Figure 4. Ex vivo central FAAH activity after a 20 mg/kg oral dose of JNJ-42119779 (37).

cores, we were able to prepare compounds with low double-digit nM apparent IC50s for both h- and rFAAH, though large potency differences between species was common. Several compounds were profiled in standard iv & p.o. PK experiments (Table 3). Two of the compounds, (16) and (18), possessed reasonable PK parameters, but both also had a 6-(2H-1,2,3-triazol2-yl)pyridin-3-amino group as a component of the urea, which we subsequently found to be mutagenic in the Ames II assay. This is a concern as this functionality would be liberated in the course of inhibiting FAAH. As a result of the mutagenicity data, compounds (16) and (18) were not profiled further. As some of the compounds in Table 3 had very large volumes of distribution, we elected to assess the ability of the potent analog (37, JNJ-42119779) to cross the blood brain barrier (BBB) (Fig. 3), inhibit FAAH centrally (Fig. 4), and increase the levels of the FAAs AEA, OEA and PEA. From this experiment, we found that overall exposure was low, but much higher in the brain than in the plasma. Interestingly, there was less than 10% residual brain FAAH activity between the 0.5 and 4 h time points post dosing, and the levels of AEA, OEA and PEA were all greatly elevated at the 4 h time point relative to the controls (AEA: 150%; PEA: 700%; OEA: 500%). In sharp contrast, the potent bis-azatidine derivative (38) had very low exposure, minimally inhibited brain FAAH and didn’t raise the levels of AEA, PEA or OEA centrally. The increases in FAA levels and the degree of central FAAH inhibition observed with (37) encouraged us to profile the compound in the spinal nerve ligation (Chung) model of neuropathic pain13 (Fig. 5). The compound was dosed at 20 mg/kg p.o. and compared to a positive control, JNJ-40355003,14 a potent FAAH inhibitor. From Figure 5, it is clear that (37) is not strongly efficacious at this dose, but the effect does reach significance overall.

Figure 6. Percentage FAAH activity following overnight dialysis of JNJ-42119779 (37) at 4 °C & room temperature.

J. M. Keith et al. / Bioorg. Med. Chem. Lett. 24 (2014) 737–741

The reversibility of binding of compound (37) to the FAAH enzyme was tested via a dialysis experiment. The compound was compared to the reversible binder OL-13515 and to the slow-off substrate JNJ-1661010 (Fig. 6). The lack of return of enzymatic activity after 24 h of dialysis suggest (37) is an irreversible binder of the FAAH enzyme and is consistent with the findings for other aryl ureas.16 In conclusion, we have discovered a series of spirocyclic heteroaryl ureas that demonstrate potent irreversible inhibition of the FAAH enzyme. Despite strong engagement of the target in vivo, only modest efficacy was observed in the spinal nerve ligation model of neuropathic pain. The PK properties of these compounds were found to be generally inferior to piperazinyl derivatives.

9.

10.

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