KNI-577, a potent small-sized HIV protease inhibitor based on the dipeptide containing the hydroxymethylcarbonyl isostere as an ideal transition-state mimic

Full text of DOI:10.1002/(SICI)1521-4184(199803)331:3<87::AID-ARDP87>3.0.CO;2-H

Communication to the Editor
KNI-577, a Potent Small-Sized HIV Protease Inhibitor Based on the
Dipeptide Containing the Hydroxymethylcarbonyl Isostere as an Ideal
[
1]
Transition-State Mimic
,
a)
a)
a)
b)
b)
b)
Yoshiaki Kiso* , Satoshi Yamaguchi , Hikaru Matsumoto , Tsutomu Mimoto , Ryohei Kato , Satoshi Nojima ,
Haruo Takaku , Tominaga Fukazawa , Tooru Kimura , and Kenichi Akaji
b)
b)
a)
a)
a)
Department of Medicinal Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan
Pharmaceutical and Biotechnology Laboratories, Japan Energy Co., Toda 335, Japan
b)
Key Words: HIV protease inhibitors; transition-state mimic; anti-HIV drug; allophenylnorstatine
The development of an effective therapeutic agent for the isostere is an ideal transition-state mimetic. Here, we report
treatment of AIDS continues to be a challenging problem. potent small-sized inhibitors containing the HMC isostere.
Since the discovery that the virally encoded HIV protease is
HIV-1 develops in vitro a high level of resistance to KNI-
vital for propagation, inhibition of this enzyme has become a 272 by acquiring mutations in the protease-encoding gene,
major target for AIDS chemotherapy. Consequently, numer- though it takes a relatively long time to do so. Mutations
ous efforts aimed at the development of potent and selective conferring KNI-272-resistance were V32I, L33F, K45I,
[2]
inhibitors have been undertaken . Based on the substrate F53L, A71V, and I84V. The EC50 values of KNI-272 against
transition state, we designed and synthesized a novel class of wild-type HIV-1 and KNI-272-resistant HIV-1 were 0.04 µM
HIV protease inhibitors containing allophenylnorstatine and 2 µM, respectively. The sensitivity of KNI-272 fell 50-
[
Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid] fold against resistant HIV-1. In order to overcome the resis-
with a hydroxymethylcarbonyl (HMC) isostere. Among tance, the Apns-containing peptides were screened. Among
them, the tripeptide KNI-272 was a highly selective and them, KNI-241 (Fig. 2) was found to be active against both
[
3]
superpotent HIV protease inhibitor (K = 5.5 pM) . KNI-272 wild-type HIV-1 (EC50 = 0.04 µM) and KNI-272-resistant
i
exhibited potent in vitro and in vivo antiviral activities with HIV-1 (EC50 = 0.04 µM). The P3 moiety of KNI-241 inter-
low cytotoxicity[ . The NMR, X-ray crystallography, and acts with both 53-Phe of wild-type protease and 53-Leu of the
4]
[
6]
molecular modeling studies showed that the HMC group in mutant protease
.
KNI-272 interacted excellently with the aspartic acid car-
However, the bioavailability of KNI-241 was low. The
solution, crystalline, and complex structures of KNI-272
[
5]
boxyl groups of the HIV protease active site .
[
7]
The hydroxyl group forms one hydrogen bond to Asp125 were similar except for P3 moiety and we considered that
oxygen and the carbonyl oxygen forms a hydrogen bond to P2-P2′ positions are core moieties for activity. Therefore, P3
the protonated oxygen of Asp25 in essentially the same was removed to improve the pharmacokinetic properties and
manner as the transition state (Fig. 1). The trans conforma- P2 was replaced by several alkyl and hydrophilic groups.
tion of the HMC-peptide bond at the P1-P1′ site of KNI-272 Among them, KNI-413 and -549 containing a dimethyl and
was predominant due to the rigidity of the P1-P1′ amide a carboxyl groups exhibited HIV protease inhibitory activi-
linkage. The trans conformer of KNI-272 fitted favorably to ties (HIV protease inhibition = 76.3% and 77.5% at 50 nM,
HIV-1 protease and was the bioactive conformation. Thus, respectively).
KNI-272 was preorganized to bioactive conformation and the
In order to enhance the inhibitory activity, we carried out
constrained conformation of KNI-272 might well be respon- the optimization study of P2 moiety. At first, we introduced
sible for the high activity. These results imply that the HMC the bulky and hydrophobic dimethylphenoxyacetyl group in
P2 position to give a potent HIV protease inhibitor KNI-727
(HIV protease inhibition = 95.9% at 50 nM; anti-HIV activity
EC50 = 1.73 µM in MT4 cells).
Next, we cyclized the P2 moiety in KNI-549 to get the rigid
form. The resulting KNI-577 was a potent HIV protease
inhibitor (87.6% inhibition at 50 nM) and showed remarkable
anti-HIV-1(IIIB) activity (EC50 = 0.02 µM in CEM-SS cells).
This antiviral activity of KNI-577 was higher than that of the
tripeptide KNI-272. KNI-577 had very low cytotoxicity
(CC50 > 200 µM) and the bioavailability after intraduodenal
administration in rats was 48%. The excellent antiviral activ-
ity and good pharmacokinetic properties of KNI-577 may be
due to the constrained conformation and the good balance
between hydrophilicity and lipophilicity due to the cyclized
P2 moiety. The synthetic scheme of KNI-577 is simple
Fig. 1. Interaction of the transition state (left) and hydroxymethylcarbonyl
isostere (right) with HIV protease active site aspartic acids.
Arch. Pharm. Pharm. Med. Chem.
© WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
0365-6233/98/0303/0087 $17.50 +.50/0

88
Kiso and co-workers
Fig. 2. Design of dipeptide-based HIV protease inhibitors.
Fig. 3. Synthesis of KNI-577, a potent dipeptide-based HIV protease inhibitor.
Arch. Pharm. Pharm. Med. Chem. 331, 87–89 (1998)

HIV Protease Inhibitor
89
and short as shown in Fig. 3. All couplings were perform- References
.
ed by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide HCl
(
[
1] This paper was preliminarily presented at the 15th American Peptide
Symposium in Nashville, Tennessee (June 14–19, 1997), Abstracts,
L023; the 33rd Symposium on Peptide Chemistry in Sapporo, Japan
(October 4–6, 1995), Peptide Chemistry 1995, pp. 373–376; the 34th
Symposium on Peptide Chemistry in Tsukuba, Japan (October 16–18,
1
EDC)/N -hydroxybenzotriazole (HOBt) in N,N-dimethyl-
formamide (DMF) at room temperature (r.t.), and all depro-
tections by HCl.
In conclusion, the hydroxymethylcarbonyl isostere was an
ideal transition-state mimetic in HIV protease inhibitor de-
sign. Small-sized dipeptides containing the hydroxymethyl-
carbonyl isostere exhibited potent HIV protease inhibitory
activities. Among them, a dipeptide-based HIV protease in-
hibitor, KNI-577 exhibited potent antiviral activities, low
cytotoxicity, and good pharmacokinetic properties after in-
traduodenal administration. This study suggests that the
small-sized dipeptide HIV protease inhibitors are good can-
didates for anti-HIV drugs.
1996), Peptide Chemistry 1996, pp. 297–300.
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Acknowledgment
This work was supported in part by grants from the Ministry of Education,
Science and Culture of Japan and Japan Health Science Foundation.
1996, 118, 12287–12290.
[
[
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1
Received: January 5, 1998 [FP272]
Arch. Pharm. Pharm. Med. Chem. 331, 87–89 (1998)