Structure-activity relationship of orally potent tripeptide-based HIV protease inhibitors containing hydroxymethylcarbonyl isostere.

We designed and synthesized a new class of peptidomimetic human immunodeficiency virus protease inhibitors containing a unique unnatural amino acid, allophenylnorstatine [Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], with a hydroxymethylcarbonyl isostere as the active moiety. From a structure-activity relationship study of HIV-1 protease inhibition, enzyme selectivity for other aspartyl proteases, the antiviral activity and pharmacokinetics in rats, 24c (KNI-227) and 24d (KNI-272, our first clinical candidate) were found to be selective and orally potent HIV protease inhibitors. Moreover, an improvement of the pharmacokinetic features of KNI-272 provided two long-lasting and highly bioavailable compounds (24g: JE-2178, 24h: JE-2179).

Comparison of a new orally potent tripeptide HIV-1 protease inhibitor (anti-AIDS drug) based on pharmacokinetic characteristics in rats after intravenous and intraduodenal administrations.

Recently, a series of KNI compounds such as KNI-227 and KNI-272 has been synthesized and shows potent and selective HIV-1 protease inhibitory activity in vitro. In this study, we developed an HPLC assay system for KNI-227 and KNI-272 in rat plasma and examined the pharmacokinetic characteristics in rats after both intravenous (i.v.) and intraduodenal (i.d.) administrations to obtain the disposition characteristics and bioavailabilities of these new anti-AIDS drugs. After i.v. administration of KNI-227, 10.0 mg kg-1, the mean terminal elimination half-life, t1/2 lambda zeta, was 0.808 +/- 0.161(SE) h, the total body clearance, CLtot, was 11.7 +/- 3.3 ml min-1 and the distribution volume at steady state (Vd,ss) was 1410 +/- 460 ml kg-1. On the other hand, after i.v. administration of KNI-272, 10.0 mg kg-1, t1/2 lambda zeta was 2.86 +/- 0.78 h, CLtot was 15.3 +/- 1.4 ml min-1 and Vd,ss was 3440 +/- 670 ml kg-1. In the case of the i.d. administration of drugs, the mean peak plasma concentrations, Cmax, of KNI-227 and KNI-272 were 0.374 +/- 0.110 microgram ml-1 and 0.900 +/- 0.093 micrograms ml-1, respectively. The bioavailabilities (BA) of KNI-227 and KNI-272 to infinity, BA(0-infinity), were 5.90% and 42.3%, respectively. As compared with the lead compound, KNI-174, the BA of KNI-272 was improved about 10 times. Although the anti-AIDS virus activity of these two drugs has not been investigated in vivo, KNI-272 is expected to be a better candidate for oral anti-AIDS therapies.

Kynostatin (KNI)-227 and -272, highly potent anti-HIV agents: conformationally constrained tripeptide inhibitors of HIV protease containing allophenylnorstatine.

Selective and potent HIV protease inhibitors containing allophenylnorstatine [Apns; (2S, 3S)-3-amino-2-hydroxy-4-phenylbutyric acid] as a transition-state mimic were designed and synthesized. Among them, conformationally constrained tripeptide derivatives, kynostatin (KNI)-227 and -272 (Fig. 1), exhibited highly potent antiviral activities against a wide spectrum of HIV isolates. Ready availability due to the simple synthetic procedure and the excellent antiviral properties indicate that KNI-227 and KNI-272 are promising candidates as selective anti-AIDS drugs.

KNI-102, a novel tripeptide HIV protease inhibitor containing allophenylnorstatine as a transition-state mimic.

HIV-1 protease inhibitors containing allophenylnorstatine [Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid]-Pro (syn diastereomer) as a transition-state mimic were established to be potent and highly selective. Z-Asn-Apns-Pro-NHBut (KNI-102) is the only tripeptide exhibiting substantial anti-HIV activity and may be of minimum size for potent, selective inhibition of HIV protease. Ready availability due to its simple chemical structure and stability should make it valuable for studies of the development of metabolically stable anti-AIDS drugs.

Rational design and synthesis of a novel class of active site-targeted HIV protease inhibitors containing a hydroxymethylcarbonyl isostere. Use of phenylnorstatine or allophenylnorstatine as a transition-state mimic.

A novel class of HIV-1 protease inhibitors containing a hydroxymethylcarbonyl (HMC) isostere were designed from the substrate transition state and synthesized. Phenylnorstatine [Pns; (2R,3S)-3-amino-2-hydroxy-4-phenylbutyric acid] and the 2S diastereomer, (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid, named allophenylnorstatine (Apns) were effective transition-state mimics, and incorporation of Pns-Pro or Apns-Pro at the P1-P1' site gave potent and specific HIV-1 protease inhibitors. In the inhibitory assays, the chemically synthesized [Ala67,95] HIV-1 protease was used.