4068
K. L. G. Jones et al. / Bioorg. Med. Chem. Lett. 20 (2010) 4065–4068
Table 2
Pharmacokinetics in dogs
theinhibitor as to complementarity to the active site. Two novel syn-
thetic routes using N-boc- -glutamic acid alpha-benzyl ester and
2,6-diaminopimelic acid were developed. Further studies optimiz-
ing the other substituents of the lysinol scaffold that resulted in both
improved functional potency and PK will be reported in due course.
L
a
Compound
Oral AUCa
(lM h)
CTrough (nM)
10b
10d
0.32
1.05
2.0
5.1
a
Values are means of at least two experiments.
Acknowledgments
The author gratefully acknowledges Philippe G. Nantermet and
Hemaka A. Rajapakse for many helpful scientific discussions. All
graphics images were created using the PyMol program from
DeLano Scientific LLC.
1000.00
n = 1
n = 2
Mean
100.00
10.00
1.00
References and notes
1. Palella, F. J., Jr.; Delaney, K. M.; Moorman, A. C.; Loveless, M. O.; Fuhrer, J.;
Satten, G. A.; Aschman, D. J.; Holmberg, S. D. N. Engl. J. Med. 1998, 338, 853.
2. Richman, D. D.; Morton, S. C.; Wrin, T.; Hellmann, N.; Berry, S.; Shapiro, M. F.;
Bozzette, S. A. AIDS 2004, 18, 1393.
3. Kohl, N. E.; Emini, E. A.; Schleif, W. A.; Davis, L. J.; Heimback, J. C.; Dixon, R. A.;
Scolnick, E. M.; Sigal, I. S. Proc. Natl. Acad. Sci. U.S.A. 1988, 85, 4686.
4. Stranix, B. R.; Lavallée, J.-F.; Sévigny, G.; Yelle, J.; Perron, V.; LeBerre, N.;
Herbart, D.; Wu, J. J. Bioorg. Med. Chem. Lett. 2006, 16, 3459.
5. Dandache, S.; Coburn, C. A.; Oliveira, M.; Allison, T. J.; Holloway, M. K.; Wu, J. J.;
Stranix, B. R.; Panchal, C.; Wainberg, M. A.; Vacca, J. P. J. Med. Virol. 2008, 80,
2053.
6. Chellappan, S.; Kairys, V.; Fernandes, M. X.; Schiffer, C.; Gilson, M. K. Proteins:
Struct. Funct. Bioinformatics 2007, 68, 561.
7. (a) Halgren, T. A. J. Comput. Chem. 1996, 17, 490; (b) Halgren, T. A. J. Comput.
Chem. 1996, 17, 520; (c) Halgren, T. A. J. Comput. Chem. 1996, 17, 553; (d)
Halgren, T. A.; Nachbar, R. B. J. Comput. Chem. 1996, 17, 587; (e) Halgren, T. A. J.
Comput. Chem. 1996, 17, 616.
8. Wang, R.; Lu, Y.; Fang, X.; Wang, S. J. Chem. Inf. Comput. Sci. 2004, 44, 2114.
9. For synthetic procedures, see: Coburn, C. A.; Vacca, J. P.; Rajapakse, H. A.; Jones,
K. L. G.; Nantermet, P.; Barrow, J. C.; Moore, K. P.; Sharik, S. S.; Theberge, C.;
Walji, A. M. WO 2009042093.
10. R = iPr was prepared from 1-iodo-2-methylpropane and catalytic base,
tetramethylguanidine, see: Kornblum, N.; Ungnade, H. E. Org. Synth. 1963, 4,
724. 1958, 38, 75.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
Time (Hour)
Figure 5. Plasma concentrations (nM) of 10d in 4 mg/kg PO dosed beagle dogs.
ethyl (10d) compounds had potencies comparable to 10a both in
the 10% SPREAD and in the more stringent SPREAD assay in the
presence of 50% normal human serum (NHS).12 In the latter assay
the unsubstituted compound 10a showed a serum adjusted IC95
value of 130 nM, while 10b and 10d were 120 nM and 74 nM,
respectively.
The pharmacokinetic properties of several of these new com-
pounds were measured to further characterize this series of HIV-
1 protease inhibitors (Table 2).
11. S-Moc-diPhe-Osu was prepared with the following two steps:
L-3,3-
diphenylalanine, ClCO2Me, 1 N NaOH, 77%, followed by N-hydroxysuccinimide,
DCC, dioxane, 0 °C.
12. Vacca, J. P.; Dorsey, B. D.; Schleif, W. A.; Levin, R. B.; McDaniel, S. L.; Darke, P. L.;
Zugay, J.; Quintero, J. C.; Blahy, O. M.; Roth, E.; Sardana, V. V.; Schlabac, A. J.;
Graham, P. I.; Condra, J. H.; Gotlib, L.; Holloway, M. K.; Lin, J.; Chen, I.-W.;
Vastag, K.; Ostovic, D.; Anderson, P. S.; Emini, E. E.; Huff, J. R. Proc. Natl. Acad.
Sci. U.S.A. 1994, 91, 4096. 95% Cell culture inhibitory concentrations (CIC95) are
defined as those which inhibited by 95% the spread of HIV-1 infection in
susceptible cell culture. MT-4 human T-lymphoid cells were maintained in
RPMI 1640 medium containing 10% heat inactivated fetal bovine serum. Cells
were infected en masse at low multiplicity (0.01) using HIV-1 strain IIIb and
were incubated for 24 h. At this time, cells were washed and distributed into
96 well microtiter dishes. Cells were resuspended in media containing 50%
normal human serum (Lonza). Serial twofold dilutions of inhibitor were added
to the wells and the cultures were maintained for three additional days. Virus
spread was assessed by HIV-1 p24 core antigen ELISA. Control cultures in the
absence of inhibitor were fully infected at 4 days.
14. Boltzmann population analysis script (Revision 1.16) downloaded from
15. Phenotypic drug susceptibility assay performed by Monogram Biosciences,
see: Petropoulos, C. J.; Parkin, N. T.; Limoli, K. L.; Lie, Y. S.; Wrin, T.; Huang, W.;
Tian, H.; Smith, D.; Winslow, G. A.; Capon, D. J.; Whitcomb, J. M. Antimicrob.
Agents Chemother. 2000, 44, 920.
As a result, the methyl substituted compound 10b and the ethyl
substituted compound 10d were each dosed at 4 mpk in PEG 400
to beagle dogs, and drug levels were measured. Both compounds
showed good overall oral exposure over the course of the experi-
ment and comparable 24 h trough drug levels. Ethyl substituted
inhibitor 10d was calculated to have a 6 h oral half-life (Fig. 5).
In addition to pharmacokinetic studies, the ethyl substituted
compound was subjected to a panel of mutant viruses,15 and this
resulted in a comparable mutation profile to compound 1.
In summary, replacement of the P10 isobutyl substituent in 1 with
an isoamyl substituent, coupled with epsilon substitution of the
lysinol sulfonamide scaffold, yielded potent HIV-1 protease inhibi-
tors. In particular, methyl and ethyl substitution on this position of
the lysinol backbone enabled access to the S2 pocket of the enzyme,
resulting in an increase in intrinsic potency as compared to the P2
unsubstituted compound. Modeling studies and synthetic efforts
attribute the gain in potency as much to conformational bias of