5794
D. L. Aubele et al. / Bioorg. Med. Chem. Lett. 21 (2011) 5791–5794
shown in Table 3. Thus, favorable modulation of the pharmacoki-
netic parameters through alteration of the physiochemical proper-
ties was realized only at the expense of potency and Notch/APP
selectivity with this particular series of compounds. Compounds
21 and 25 displayed modest potency, but demonstrated a ꢀfour-
fold loss in selectivity when compared to their respective –F ana-
logs, 19 and 20. Compounds 22–24 displayed excellent metabolic
stability, but lacked the desired level of potency and demonstrated
a ꢀfive-fold decrease in selectivity when compared to their respec-
tive –F analog, 20.
Further exploration of the C-6 position of the bicyclic core re-
vealed that heteroaryl substitutions in this position generally
exhibited good oxidative metabolic stability. However, wide fluc-
tuations in potency and Notch/APP selectivity were observed, as
shown in Table 4. Additionally, this series suffered from moder-
ate to high P-gp efflux ratios. Larger fused heterocycles, such as
benzimidazole 26, and six-membered heterocycles such as pyri-
dine 27, were detrimental towards both potency and selectivity.
Alkyl substitution in the 5-position of heterocycles, like that
displayed by 28–30, were not well tolerated in terms of potency
or selectivity. However, these compounds generally displayed
excellent metabolic stability. Compounds 32 and 33 displayed
excellent potency and moderate selectivity, but suffered from a
high P-gp liability. Protic heterocycles like 34 were not well tol-
erated and resulted in a dramatic decrease in selectivity. Com-
pound 31 exhibited the best combination of potency, oxidative
metabolic stability and Notch/APP selectivity, with a moderate
P-gp liability.
The in vivo efficacy of compounds 20 and 31 were evaluated in
wild type FVB mice by administration of a single 10 mg/kg PO
dose. A statistically significant reduction in Abx-40 of 21% in the
cortex 3 h post dose with compound 20 was observed. Whereas,
a non-statistically significant reduction in Abx-40 of 3% in the cor-
tex 3 h post dose with compound 31 was observed. The lack of
efficacy observed with compound 31 is likely due to its poor plas-
ma exposure and poor brain penetration (B/P ratio = 0.08), stem-
ming from its moderate P-gp liability (P-gp efflux ratio = 4). The
observed efficacy of compound 20 can be attributed to its
moderate brain penetration (B/P ratio = 0.3). Compound 20 exhib-
ited a P-gp Efflux ratio = 1, indicating that it little to no P-gp
liability.
Acknowledgment
We would like to thank Jennifer Marugg, Brian Peterson, Lany
Ruslim, Ferdie Soriano, Grace Kwong, David Chian, Pamela Santi-
ago, Anna Liao, Michael Lee, Kang Hu, Jacek Jagodzinski, David
Quincy, Michael Dappen and Lee Latimer for their contributions
to this work.
References and notes
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14. Compound, initially diluted with DMSO, was incubated with gamma secretase
prepared from IMR-32 cell membranes. The reaction, at 37 °C, was initiated by
the addition of MBPC-125 Swedish substrate for 2 h, and then was quenched
by the addition of SDS. Quantification of cleaved substrate was determined by
an Ab40 specific ELISA assay.
15. Compound, initially diluted with DMSO, was incubated with SNC-204B8 cells
at 37 °C for 18 h. Conditioned media was then aspirated from the cells for
determination of Ab1–X levels by ELISA, and cells were lysed for determination
of Notch signaling by luciferase reporter gene activity (Promega) per
manufacturer’s protocol.
In conclusion, we have identified a novel series of sulfonamide-
pyrazoles that attenuate b-amyloid peptide synthesis via c-secre-
tase inhibition with potential utility as a therapy for Alzheimer’s
disease. This series is not only potent, metabolically stable, and
exhibits >190-fold selectivity for inhibition of APP versus Notch
16. Percentage of compound (1 lM) remaining after 30 min incubation in liver
microsomes (0.5 mg/mL protein) supplemented with 1 mM NADPH at 37 °C in
phosphate buffer. (m = mouse, h = human).
17. Compounds (5 lM) in mHBSS (pH 7.4) were incubated with MDR1-MDCK cell
monolayers for 120 min at 37 °C with and without a P-gp inhibitor. Samples
were taken from apical (A) and basolateral (B) chambers, and analyzed using
LC/MS/MS. The efflux ration was determined by dividing the rate of A to B
direction with and without a P-gp inhibitor.
processing by
c-secretase, but is also efficacious in reducing the
cortical Abx-40 levels in wild type FVB mice via a single pharma-
ceutically relevant oral dose.