4074
J. Li et al. / Bioorg. Med. Chem. Lett. 18 (2008) 4072–4074
Table 2
in vivo efficacy in a rat model. Compound 10 also showed a greater
Cmax, systemic exposure (AUC), and oral bioavailability as com-
pared to compound 2, in the preliminary pharmacokinetic study
Pharmacokinetic results of 2 and 10 in rats
IV (n = 3)
PO (n = 3)
in rats. Further application of the (D)-2-tert-butoxycarbonylami-
no-5,5-difluoro-5-phenyl-pentanoic acid 3 in the preparation other
GHS compounds in the program will be reported in due course.
Compound
Dose ( mole/kg)
Cmax (nM)
2
5
10
10
2
10
10
166
1.6
239
l
15
68
0.7
110
Tmax (h)
AUC (nMÃh)
401
0.7
0.5
213
6.4
901
2.4
1.4
183
16
T1/2 (h)
References and notes
MRT (h)
Clearance (ml/min/kg)
Vss (L/kg)
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actions of GHRPs, see: (b) Ghigo, E.; Arvat, E.; Muccioli, G.; Camanni, F. Eur. J.
Endocrinol. 1997, 136, 445. and references therein.
Bioavailability (%)
9.2
26
Values are means of three rats.
2. (a) Smith, R. G. Endocrine Rev. 2005, 26, 346; (b) Smith, R. G.; Ploeg, L. T. V. D.;
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Table 3
In vivo activity of the compounds in the acute anesthetized rat model
Compounds
Increase GHa at 1.74
l
mol/kg (% of vehicle)
Respondersb
2
10
750( 112)
1934 ( 130)
5/5
5/5
a
Values are means of five experiments.
A rat with more than 200% GH increase over vehicle control is considered as a
b
responder.
molecule with the GHS receptor. One possibility is that the fluo-
rines serve as hydrogen bonding acceptors with residues in the ac-
tive sites. However, the detailed mechanism is still not clear since
the fluorine hydrogen bond is a subject of controversy in different
environments.10 In another comparison, the gem-difluorinated
analog 16 of an earlier program lead 15 was found to be substan-
tially more potent as well (33-fold),11 further corroborating the
in vitro enhancement effected by this modification.
We then further evaluated the pharmacokinetic properties of 10
in fasted rats at an oral and IV dose of 10.
PK parameters versus 2 is shown in Table 2. Upon oral dosing at
10 mol/kg, compound 10 afforded a greater Cmax, systemic expo-
sure (AUC), and oral bioavailability as compared to compound 2,
which was orally dosed at 15 mol/kg. The IV arm indicated that
lmol/kg. A comparison of
4. Nargund, R. P.; Patchett, A. A.; Bach, M. A.; Murphy, M. G.; Smith, R. G. J. Med.
Chem. 1998, 41, 3103.
l
5. Li, J.; Chen, S. Y.; Li, J. J.; Wang, H.; Hernandez, A. S.; Tao, S.; Musial, C. M.; Qu, F.;
Swartz, S.; Chao, S. T.; Flynn, N.; Murphy, B. J.; Slusarchyk, D. A.; Seethala, R.;
Yan, M.; Sleph, P.; Grover, G.; Smith, M. A.; Beehler, B.; Giupponi, L.; Dickinson,
K. E.; Zhang, H.; Humphreys, W. G.; Patel, B. P.; Schwinden, M.; Stouch, T.;
Cheng, P. T. W.; Biller, S. A.; Ewing, W. R.; Gordon, D.; Robl, J. A.; Tino, J. A.
J. Med. Chem. 2007, 50, 5890.
6. Burgey, C. S.; Robinson, K. A.; Lyle, T. A.; Sanderson, P. E. J.; Lewis, S. D.; Lucas, B.
J.; Krueger, J. A.; Singh, R.; Miller-Stein, C.; White, R. B.; Wong, B.; Lyle, E. A.;
Williams, P. D.; Coburn, C. A.; Dorsey, B. D.; Barrow, J. C.; Stranieri, M. T.;
Holahan, M. A.; Sitko, G. R.; Cook, J. J.; McMasters, D. R.; McDonough, C. M.;
Sanders, W. M.; Wallace, A. A.; Clayton, F. C.; Bohn, D.; Leonard, Y. M.; Detwiler,
T. J., Jr.; Lynch, J. J., Jr.; Yan, Y.; Chen, Z.; Kuo, L.; Gardell, S. J.; Shafer, J. A.; Vacca,
J. P. J. Med. Chem. 2003, 46, 461.
l
10 also exhibited a longer half-life and slightly reduced clearance
in the rat. These results suggest that the superior PK profile of this
compound, versus 2, may be attributed to the gem-difluoro benzyl
functionality, which replaces the benzyloxy group found in 2.
The efficacy of compounds 10 and 2 was further evaluated in an
acute anesthetized rat model measuring endogenous GH release as
the response. The compounds were administered intravenously at
a dose of 1.74 lmol/kg. After 15 min, blood samples were collected
and the plasma isolated and analyzed for rat growth hormone
(GH). Data are expressed as the percentage of increase GH release
compared with vehicle control animals (Table 3).
In agreement with the in vitro and PK findings, 10 showed im-
proved in vivo activity in the acute anesthetized rat model, increas-
ing rat GH by nearly 3-fold over that of the parent 2.
In summary, a gem-difluoro benzyl group as a replacement of
left-hand O-benzyl side chain of BMS-317180 2 resulted in an ana-
log 10, which significantly improved the in vitro potency as well as
7. Ezquerra, J.; Pedregal, C.; Rubio, A.; Valenciano, J.; Navio, J. L. G.; Alvarez-Builla,
J.; Vaquero, J. J. Tetrahedron Lett. 1993, 34, 6317.
8. York, C.; Prakash, G. K. S.; Olah, G. A. Tetrahedron 1996, 52, 9.
9. In vitro assays see supporting information part in Ref. 5.
10. (a) Barbarich, T. J.; Rithner, C. D.; Miller, S. M.; Anderson, O. P.; Strauss, S. H. J.
Am. Chem. Soc. 1999, 121, 4280; (b) Schlosser, M. Angew. Chem. Int. Ed. 1998,
110, 1496.
11. Hernandez, A. S.; Cheng, P. T. W.; Musial, C. M.; Swartz, S. G.; George, R. J.;
Grover, G.; Slusarchyk, D.; Seethala, R. K.; Smith, M.; Dickinson, K. E.; Giupponi,
L.; Longhi, D. A.; Flynn, N.; Murphy, B. J.; Gordon, D. A.; Biller, S. A.; Robl, J. A.;
Tino, J. A. Bioorg. Med. Chem. Lett. 2007, 30, 5928.