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C. Fischer et al. / Bioorg. Med. Chem. Lett. 25 (2015) 3488–3494
regioisomer was achieved through a wash procedure and subse-
quent purification on silica gel.20
albeit with an improvement in hERG binding. We continued to pro-
file compounds 29–39 in rat PK as well as rodent PK/PD studies to
differentiate them in vivo. Compound 34 was particularly effica-
cious when we profiled it in APP-YAC29 transgenic mice as well
as Sprague-Dawley (SD) rats where an ED50 of 15 mpk was deter-
mined for both models with oral dosing.30 At the highest dose
(100 mpk) of triazole 34 in the SD rat dose–response experiment
Alkynylation of aldehyde 8 with the Bestmann–Ohira reagent
gave the desired alkyne 9 in quantitative yield. A click reaction21
of alkyne
copper(II)sulfate and sodium ascorbate as the reductant, furnished
triazoles 16 in good to excellent yields. The required -azido lac-
tams 15 were generally prepared from the corresponding -halo
lactams 12–14 and sodium azide in polar aprotic solvents, such
as DMF or DMSO, at room temperature. -Halogenation of lactams
9 with azidolactams 15 in ethanol/water, with
a
a
a total brain level of 35 lM 6 h after dosing was observed with a
reduction in brain Ab42 levels of 92% relative to vehicle control.
While other compounds in Table 2 were also efficacious in our
rodent models we found that compound 34 performed most con-
sistently in both rodent species and additionally showed excellent
exposures at higher doses. Chart 1 details some of the in vitro and
in vivo data for compound 34.
Further studies with compound 34 first addressed the concern-
ing hERG binding; in patchXpress the half maximal inhibition of IKr
was 12.9 lM.
a
11 was accomplished using the standard methods described in
Scheme 1; lactams 11 were either commercially available or pre-
pared using conventional two-step ring-expansion chemistry from
commercially available tetralones 10. We found the Beckmann
reaction to provide lactams in reproducibly high yields and regioi-
someric purity. Installation of a substituent on nitrogen was gener-
ally accomplished through alkylation of 16 to give 17 through
standard chemistry.
We first decided to explore the influence of the lactam N-sub-
stituent on cellular potency, Notch selectivity and hERG binding.
In our earlier amide and lactam series we had found a strong influ-
ence on potency and hERG binding and thus explored both broadly
and with our earlier SAR in mind. Cell biochemical data for the
inhibition of Ab42/4022 production and Notch processing23 as well
as binding affinity for the hERG channel24 for our initial set of ben-
zazepinones 18–28 are reported in Table 1.
While stability in hepatocytes was only modest we were able to
establish reasonable PK in SD rats at low doses and excellent expo-
sure at 100 mpk in Wistar-Han rats where a normalized AUC of
8.8
l
MÁhÁkg/mg was calculated. Free fractions were reasonable
across species and compound 34 was also not a substrate for human
Aβ42/40 IC50 (nM):
31/131
39780
2609
Notch IC50 (nM):
hERG (MK_499) IC50 (nM):
Compounds 18–23 were resolved and data for the more active
enantiomer is shown, whereas for compounds 24–28 data for the
racemates is reported. Overall the trends we observed were similar
to our earlier azepinone series, where hydrophobic groups proved
superior in terms of potency but remained challenging when trying
to attenuate off-target activities such as hERG binding. Installation
of polarity on the amide nitrogen side chain was met with consid-
erable loss in potency and only marginal improvements in ion
channel binding. Additionally, the added polarity tended to
increase susceptibility for PgP-mediated efflux (data not shown).
Triazole 22 showed the most promising on-target potency, with
a >500-fold window over Notch processing. Therefore we decided
to continue our exploration, keeping the N-trifluoroethyl group
constant while altering both the azepane and benzo-fused ring.
We continued to utilize the facile ring-expansion using the
Beckmann reaction, which gave exclusively the desired regio-iso-
mer for all benzo-fused tetralone derivatives. Selected compounds
are shown in Table 2 with their respective Ab42/40, Notch and
hERG potencies. All compounds in this table were chirally resolved
and only data for the most active isomer is shown. We saw a pref-
erence for one enantiomer, with the active enantiomer being 5- to
15-fold more potent than its less potent congener.25 Compound 22
had modest metabolic stability (35 min t½ in rat liver microsomes)
and we began to explore the azepane ring first with blocking
attempts on positions that we suspected as metabolic soft spots.
Substitution in the 5-position (e.g., 29)26 was generally tolerated
and the 5-carbon could also be substituted with heteroatoms
(e.g., 30).27 Substitution to form the C3 quaternary carbon (com-
pound 31), however, was met with a significant loss in potency.28
While compound 29 had an improved in vitro metabolic stability
(72 min t½ in rat liver microsomes) its in vivo PK was not
improved over compound 22.
12900
hERG patch Xpress IC50 (nM):
CYP-3A4 (inh):
42% (@ 10 μM)
μ
CYP-2C9 (inh):
68% (@ 10 M)
28% (@ 10 μM)
> 30000
CYP-2D6 (inh):
PXR EC50 (nM):
CYP3A4TDI (%lost @ 50 μM)
Sol pH 7/2 (μM) / logD / PSA:
18%
5.6(180) / 3.3 / 76
Free fraction(%) rat:3.7 dog:5.8 rhesus:5.7 human:3.6
Hepatocyte Stability Half-Lives
rat (36 min), dog (67 min), rhesus (49 min), human (61 min)
PGP and passive permeability
Human mdr1: 1.2
Rat mdr1a: 1.3
P
app: 25x10-6 cm/s
PK Species
SD Rat
Dog
Rhesus
Dose (iv; po) (mg/kg)
Clp (mL/min/kg)
Vdss (L/Kg)
1; 2 0.25; 0.5 0.25; 0.5
38
4.8
0.8
190
1.6
82
14
6.2
<5
17
2.0
1.2
<5
t½ (iv) (h)
%F
0.1
ND
AUCN 0–24 po (μM h kg/mg)
Plasma concentrations (μM) of compound 34 after a 100 mg/kg
p.o. dose in Wistar Han rats
100
10
1
Rat 1
Rat 2
Rat 3
Mean
Next, we turned to exploring the benzo-fused ring and found
that substitution in the 6- and 7-positions as well as 6,8- and
6,7-disubstitution were favored whereas 8- and 9-substitution
led to flat SAR or slight potency loss (data not shown). While 6,7-
disubstitution (e.g., 36) or fused rings such as 32 gave rise to com-
pounds with promising cell potencies, their off target profile as
0.1
0
5
10
15
20
25
30
Time (Hour)
exemplified by sub-lM hERG binding was less than ideal.
Heteroaromatic analogs 37 and 38 showed a loss in cellular activity
Chart 1. Detailed profiling of compound 34.