Bis(heteroaryl)piperazine Research Articles

Progress of Bis(heteroaryl)piperazines (BHAPs) as Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) against Human Immunodeficiency Virus Type 1 (HIV-1)

Since the first case of acquired immunodeficiency syndrome (AIDS) was reported in 1981, AIDS, as the global disease affecting 33.2 million people in 2007, has always been an unsolved problem worldwide. Reverse transcriptase (RT) is a crucial enzyme in the life cycle of human immunodeficiency virus type 1 (HIV-1), and thereby has been the prime drugs target for antiretroviral (ARV) therapy against AIDS. To date, two classes of RT inhibitors (RTIs), e.g., nucleoside reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), and a lot of compounds tested as RTIs have been described. To our knowledge, bis(heteroaryl)piperazines (BHAPs) have been considered as one class of promising NNRTIs, such as structurally and chemically related NNRTI delavirdine, which was approved by the U. S. Food and Drug Administration (FDA) for the treatment of HIV-1 infection in 1997. In this mini-review, we make attempts to report the progress of synthesis and structure-activity relationship (SAR) of BHAPs, in the meantime, the synergistic inhibition of HIV-1 replication by combining delavirdine with other HIV-1 inhibitors is also discussed. It will pave the way for the design and development of BHAPs as anti-HIV-1 agents in AIDS chemotherapy in the future.

Synthesis of bis‐heteroaryl piperazine derivatives as potential reverse transcriptase inhibitors

AbstractVinylogous analogs of non‐nucleoside reverse transcriptase inhibitors belonging to the bis‐(hetero‐aryl)piperazine (BHAP) series were synthesized by coupling a piperazine derivative with (E)‐propenoyl derivatives of heterocyclic moieties.

Unique features in the structure of the complex between HIV-1 reverse transcriptase and the bis(heteroaryl)piperazine (BHAP) U-90152 explain resistance mutations for this nonnucleoside inhibitor.

The viral reverse transcriptase (RT) provides an attractive target in the search for anti-HIV therapies. The nonnucleoside inhibitors (NNIs) are a diverse set of compounds (usually HIV-1 specific) that function by distorting the polymerase active site upon binding in a nearby pocket. Despite being potent and of generally low toxicity, their clinical use has been limited by rapid selection for resistant viral populations. The 2.65-A resolution structure of the complex between HIV-1 RT and the bis(heteroaryl)piperazine (BHAP) NNI, 1-(5-methanesulfonamido-1H-indol-2-yl-carbonyl)-4- [3-(1-methyl-ethylamino) pyridinyl] piperazine (U-90152), reveals the inhibitor conformation and bound water molecules. The bulky U-90152 molecule occupies the same pocket as other NNIs, but the complex is stabilized quite differently, in particular by hydrogen bonding to the main chain of Lys-103 and extensive hydrophobic contacts with Pro-236. These interactions rationalize observed resistance mutations, notably Pro-236-Leu, which occurs characteristically for BHAPs. When bound, part of U-90152 protrudes into the solvent creating a channel between Pro-236 and the polypeptide segments 225-226 and 105-106, giving the first clear evidence of the entry mode for NNIs. The structure allows prediction of binding modes for related inhibitors [(altrylamino)piperidine-BHAPs] and suggests changes to U-90152, such as the addition of a 6 amino group to the pyridine ring, which may make binding more resilient to mutations in the RT. The observation of novel hydrogen bonding to the protein main chain may provide lessons for the improvement of quite different inhibitors.

ChemInform Abstract: Synthesis and Bioactivity of Novel Bis(heteroaryl)piperazine (BHAP) Reverse Transcriptase Inhibitors: Structure‐Activity Relationships and Increased Metabolic Stability of Novel Substituted Pyridine Analogues.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and bioactivity of novel bis(heteroaryl)piperazine (BHAP) reverse transcriptase inhibitors: structure-activity relationships and increased metabolic stability of novel substituted pyridine analogs.

The major route of metabolism of the bis(heteroaryl)piperazine (BHAP) class of reverse transcriptase inhibitors (RTIs), atevirdine and delavirdine, is via oxidative N-dealkylation of the 3-ethyl- or 3-isopropylamino substituent on the pyridine ring. This metabolic pathway is also the predominant mode of metabolism of (alkylamino)piperidine BHAP analogs (AAP-BHAPs), compounds wherein a 4-(alkylamino)piperidine replaces the piperazine ring of the BHAPs. The novel AAP-BHAPs possess the ability to inhibit non-nucleoside reverse transcriptase inhibitor (NNRTI) resistant recombinant HIV-1 RT and NNRTI resistant variants of HIV-1. This report describes an approach to preventing this degradation which involves the replacement of the 3-ethyl- or 3-isopropylamino substituent with either a 3-tert-butylamino substituent or a 3-alkoxy substituent. The synthesis, bioactivity and metabolic stability of these analogs is described. The majority of analogs retain inhibitory activities in enzyme and cell culture assays. In general, a 3-ethoxy or 3-isopropoxy substituent on the pyridine ring, as in compounds 10, 20, or 21, resulted in enhanced stabilities. The 3-tert-butylamino substituent was somewhat beneficial in the AAP-BHAP series of analogs, but did not exert a significant effect in the BHAP series. Lastly, the nature of the indole substitution sometimes plays a significant role in metabolic stability, particularly in the BHAP series of analogs.

Simultaneous mutations at Tyr-181 and Tyr-188 in HIV-1 reverse transcriptase prevents inhibition of RNA-dependent DNA polymerase activity by the bisheteroarylpiperazine (BHAP) U-90152s

The replacement of either Tyr-181 or Tyr-188 of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) by the corresponding HIV-2 RT amino acids Ile-181 or Leu-188 is known to result in active mutant enzymes (Y181I; Y188L) with virtual loss of sensitivity towards three structural classes of nonnucleoside RT inhibitors; L-697,661, nevirapine, and TIBO R82913. The bisheteroarylpiperazine (BHAP) U-90152S, a highly specific inhibitor (IC 50, 0.29 ± 0.01 μM) of HIV-1 RT, inhibited the recombinant Y181I and Y188L HIV-1 RT mutants with IC 50 values of 3.6 ± 0.15 μM and 0.71 ± 0.02 μM, respectively. Construction and in vitro analysis of double mutants Y181I/Y188L and Y181C/Y188L of HIV-1 RT showed > 150-fold resistance to U-90152S. An HIV-2 mutant containing amino acids 176–190 from HIV-1 RT acquired full sensitivity to U-90152S (IC 50, 0.29 ± 0.01 μM). It is concluded tha simultaneous mutations at Tyr-181 and Tyr-188 of HIV-1 RT promotes resistance to U-90152S.

Design and synthesis of a conformationally constrained analog of the bis(heteroaryl)piperazine (BHAP) HIV-1 reverse transcriptase inhibitor atevirdine

The design and synthesis of a novel conformationally constrained spiro analog of the BHAP class of HIV-1 reverse transcriptase inhibitors, based on the molecular modeling and the X-ray crystal structure of the clinical candidate atevirdine, is described.

Suppression of the breakthrough of human immunodeficiency virus type 1 (HIV-1) in cell culture by thiocarboxanilide derivatives when used individually or in combination with other HIV-1-specific inhibitors (i.e., TSAO derivatives).

Five structurally related thiophene and furane analogues of the oxathiin carboxanilide derivative NSC 615985 (UC84) (designated UC10, UC68, UC81, UC42, and UC16) were identified as potent inhibitors of HIV-1 replication in cell culture and HIV-1 reverse transcriptase activity. These compounds were markedly active against a series of mutant HIV-1 strains, containing the Leu-100-->Ile, Val-106-->Ala, Glu-138-->Lys, or Tyr-181-->Cys mutations in their reverse transcriptase. However, the thiocarboxanilide derivatives selected for mutations at amino acid positions 100 (Leu-->Ile), 101 (Lys-->Ile/Glu), 103 (Lys-->Thr/Asp) and 141 (Gly-->Glu) in the HIV-1 reverse transcriptase. The compounds completely suppressed HIV-1 replication and prevented the emergence of resistant virus strains when used at 1.3-6.6 microM--that is, 10- to 25-fold lower than the concentration required for nevirapine and bis(heteroaryl)piperazine (BHAP) U90152 to do so. If UC42 was combined with the [2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)]-beta-D-pentofuranosyl (TSAO) derivative of N3-methylthymine (TSAO-m3T), virus breakthrough could be prevented for a much longer time, and at much lower concentrations, than if the compounds were used individually. Virus breakthrough could be suppressed for even longer, and at lower drug concentrations, if BHAP was added to the combination of UC42 with TSAO-m3T, which points to the feasibility of two- or three-drug combinations in preventing virus breakthrough and resistance development.

Mechanism of resistance to U-90152S and sensitization to L-697,661 by a proline to leucine change at residue 236 of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase

Bisheteroarylpiperazines (BHAPs) are highly specific inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). BHAP-resistant HIV-1 is sensitized to other classes of nonnucleoside RT inhibitors and this has been primarily attributed to a proline-to-leucine substitution at amino acid 236 (P236L) of HIV-1 RT. To understand the basis for the in vitro sensitization-resistance phenomenon, single base pair mutations at amino acid P236 in HIV-1 RT were introduced to obtain P236L, P236T, P236H, P236R, and P236A HIV-1 RT mutants. Active HIV-1 RT mutants H235W, D237T, and H235W/D237T/T240K, containing substitutions from HIV-2 RT, were also cloned, expressed, and purified. Three BHAPs (U-88204E, U-87201E, and U-90125S) and the pyridinone L-697,661 were selected to quantitatively assess the effects of these amino acid substitutions on sensitization to L-697,661 and resistance to the BHAPs. The HIV-1 RT mutants bearing single (H235W; D237T) or multiple (H235W/D237T/T240K) HIV-2 RT substitutions around the conserved P236 conferred little resistance or sensitization to these RT inhibitors. The inhibition profiles of the P236 HIV-1 RT mutants demonstrated a direct correlation between sensitization to L-697,661 and resistance to the BHAPs. These results suggest alterations in the shape of the binding pocket as the mechanism by which the P236L mutation confers resistance to the BHAPs and sensitization to L-697,661.

Human immunodeficiency virus 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors may suppress the replication of specific drug-resistant (E138K)RT HIV-1 mutants or select for highly resistant (Y181C-->C181I)RT HIV-1 mutants.

Mutant HIV-1 that expresses a Glu138-->Lys substitution in its RT [(E138K)RT] is resistant to the HIV-1-specific RT inhibitor 2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)pyrimidine (TSAO). However, cell cultures infected with this mutant were completely protected against virus-mediated destruction by micromolar concentrations of the HIV-1-specific RT inhibitors tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), nevirapine, and bis(heteroaryl)piperazine (BHAP). In contrast, cells infected with a virus mutant that expresses a Tyr181-->Cys substitution in its RT [(Y181C)RT] were not protected by nevirapine and TIBO and were only temporarily protected by BHAP. HIV-1 mutant that emerged under the latter conditions contained a Cys181-->Ile substitution in their RT [(LC181I)RT]. This mutant proved highly resistant to all HIV-1-specific RT inhibitors tested, except for several 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) derivatives. When recombinant (C181I)RT was evaluated for susceptibility to the HIV-1-specific RT inhibitors, it was resistant to all inhibitors except the HEPT compounds. Since a (Y181F)RT HIV mutant strain was isolated from cells infected with (Y181C)RT HIV-1 and treated with BHAP, we postulate that the Ile codon was derived from a Cys-->Phe transversion mutation (TGT-->TTT), followed by a Phe-->Ile transversion mutation (TTT-->ATT).

Discovery, synthesis, and bioactivity of bis(heteroaryl)piperazines. 1. A novel class of non-nucleoside HIV-1 reverse transcriptase inhibitors.

A variety of analogues of 1-[4-methoxy-3,5-dimethylbenzyl]-4-[3-(ethylamino)-2-pyridyl]piperazine hydrochloride (U-80493E) were synthesized and evaluated for their inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). Replacement of the substituted aryl moiety with various substituted indoles provided bis(heteroaryl)piperazines (BHAPs) that were 10-100-fold more potent than U-80493E. The pyridyl portion of the lead molecule was found to be very sensitive to modifications. Extensive preclinical evaluations of several of these compounds led to the selection of 1-[(5-methoxyindol-2-yl)carbonyl]-4-[3-(ethylamino)-2- pyridyl]piperazine methanesulfonate (U-87201E, atevirdine mesylate) for clinical evaluation.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs)

Various non-nucleoside reverse transcriptase inhibitors (NNRTIs) have been reported to specifically inhibit human immunodeficiency virus type 1 (HIV-1): for example, tetrahydroimidazobenzodiazepinone (TIBO), hydroxyethoxymethylphenylthiothymine (HEPT), dipyridodiazepinone (i.e. nevirapine), pyridinone, bis(heteroaryl)piperazine (BHAP), tert-butyldimethylsilylspiroaminooxathioledioxide (TSAO), α-anilinophenylacetamide (α-APA) and quinoxaline derivatives. These compounds interact allosterically (i.e. non-competitively with respect to the natural substrate (dNTPs)) with a specific non-substrate binding site ‘pocket’ of the HIV-1 reverse transcriptase (RT). The most potent NNRTIs have been found to inhibit HIV-1 replication at nanomolar concentrations. These compounds therefore offer great potential for the treatment of HIV-1 infections. Yet, the virus may rapidly develop resistance to these drugs. The mutations conferring resistance have been mapped at the RT positions 100 (Leu × lle), 103 (Lys × Asn), 106 (...

Knocking-Out Concentrations of HIV-1-Specific Inhibitors Completely Suppress HIV-1 Infection and Prevent the Emergence of Drug-Resistant Virus

Treatment of HIV-1-infected cells with the HIV-1-specific inhibitors hydroxyethoxymethylphenylthiothymine (HEPT), tetrahydroimidazobenzodiazepinones (TIBO), nevirapine, pyridinone, bis(heteroaryl)piperazines (BHAP), and tert -butyl-dimethylsilylspiroaminooxathioledioxide (TSAO) at a concentration of 0.1 μg/ml resulted in a rapid breakthrough of resistant virus within three to four subcultivations. At drug concentrations of 0.5 to 1 μg/ml, emergence of resistant virus was delayed. The drug-resistant HIV-1 strains that originated under these conditions were genetically and phenotypically characterized and showed differential sensitivities against the different classes of HIV-1-specific inhibitors depending on the amino acid substitutions in their reverse transcriptase. Novel amino acid substitutions were found in the reverse transcriptase of BHAP- and pyridinone-resistant mutant HIV-1 strains that had not been reported so far. At 2.5 to 10 μg/ml, that is at a concentration 100- to 250-fold higher than the 50% effective concentration (EC 50), HEPT, TIBO, nevirapine, pyridinone, and BHAP prevented virus breakthrough after 15 subcultivations. In contrast, 3′-azido-2′,3′-dideoxythymidine (AZT), even when administered at a 1000-fold higher concentration (i.e., 1.3 μg/ml) than its EC 50 failed to prevent virus breakthrough after the second subcultivation. HIV-1-infected cell cultures could apparently be cleared from virus by the HIV-1-specific inhibitors when used at the "knocking-out" concentrations (2.5-10 μg/ml), as evidenced by (i) the lack of viral cytopathicity, (ii) the lack of virus-specific envelope glycoprotein expression, (iii) the lack of viral p24 antigen production, and (iv) the apparent absence of proviral DNA in the cells. Moreover, uninfected CEM cell cultures to which HIV-1-infected CEM cells (including syncytia) had been added were protected from destruction by high-concentration treatment with the HIV-1-specific inhibitors, but not with AZT and DDI (2′,3′-dideoxyinosine).

Treatment of human immunodeficiency virus type 1 (HIV-1)-infected cells with combinations of HIV-1-specific inhibitors results in a different resistance pattern than does treatment with single-drug therapy.

Human immunodeficiency virus type 1 (HIV-1)-infected CEM cells were treated by the HIV-1-specific inhibitors bis-heteroarylpiperazine (BHAP), 4,5,6,7-tetrahydro-5-methylimidazo[4,5,1-jk][1,4]benzodiazepin-2(1 H)-on e (TIBO) R82913, nevirapine, and the N3-methylthymine derivative of [2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro- 5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide) (TSAO-m3T), as single agents or in combination, at escalating concentrations. When used individually, the compounds led to the emergence of drug-resistant virus strains within two to five subcultivations. The resulting strains were designated HIV-1/BHAP, HIV-1/TIBO, HIV-1/Nev, and HIV-1/TSAO-m3T, respectively. The mutant viruses showed the following amino acid substitutions in their reverse transcriptase (RT): Leu-100-->Ile for HIV-1/BHAP; Lys-103-->Asn for HIV-1/TIBO; Val-106-->Ala for HIV-1/Nev; and Glu-138-->Lys for HIV-1/TSAO-m3T. Both the Tyr-181-->Cys and Val-106-->Ala mutations were found in another mutant emerging following treatment with nevirapine at escalating concentrations. The BHAP-resistant virus remained fully sensitive to the inhibitory effects of nevirapine and TSAO-m3T, whereas the TSAO-m3T-resistant virus remained fully sensitive to the inhibitory effects of nevirapine and BHAP. When different pairs of nonnucleoside RT inhibitors (i.e., BHAP plus TSAO-m3T, nevirapine plus TSAO-m3T, TIBO plus TSAO-m3T, nevirapine plus TIBO, and BHAP plus nevirapine) were used, resistant virus emerged as fast as with single-drug therapy. In all cases the Tyr-181-->Cys mutation appeared; the virus showed markedly reduced sensitivity to all HIV-1-specific inhibitors but retained sensitivity to 2',3'-dideoxynucleoside analogs such as zidovudine, ddC, and ddI. Our findings argue against simultaneous combination of two different nonnucleoside RT inhibitors that are unable to inhibit HIV-1 mutant strains containing the Tyr-181-->Cys mutation when administered as single drugs.

Can resistance to anti-HIV drugs be advantageous?

Rather than being problematic, drug resistance may be crucial to the development of anti-HIV combination therapies. Like most of the non-nucleoside reverse transcriptase inhibitors, the bisheteroarylpiperazines (BHAPs) were thought to be of minor importance as anti-HIV drugs because of the rapidity with which resistant strains developed. However, trials co-ordinated by the US National Institute of Allergy and Infectious Disease (NIAID) have set out to demonstrate that this property may be an advantage in combination therapies.

A mutation in reverse transcriptase of bis(heteroaryl)piperazine-resistant human immunodeficiency virus type 1 that confers increased sensitivity to other nonnucleoside inhibitors.

Several nonnucleoside inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) have been described, including Nevirapine, thiobenzimidazolone (TIBO) derivatives, pyridinone derivatives such as L-697,661, and the bis(heteroaryl)piperazines (BHAPs). HIV-1 resistant to L-697,661 or Nevirapine emerges rapidly in infected patients treated with these drugs, and the resistance is caused primarily by substitutions at amino acids 181 and 103 of RT that also confer cross resistance to the other nonnucleoside inhibitors. We describe derivation and characterization of two BHAP-resistant HIV-1 variants that differ from this pattern of cross resistance. With both variants, HIV-1 resistance to BHAP RT inhibitors was caused by a RT mutation that results in a proline-to-leucine substitution at amino acid 236 (P236L). Rather than conferring cross resistance to other RT inhibitors, this substitution sensitized RT 7- to 10-fold to Nevirapine, TIBO R82913, and L-697,661 without influencing sensitivity to nucleoside analogue RT inhibitors. This sensitization caused by P236L was also observed in cell culture with BHAP-resistant HIV-1. The effects of the P236L RT substitution suggest that emergence of BHAP-resistant virus in vivo could produce a viral population sensitized to inhibition by these other nonnucleoside RT inhibitors.

Prevention of the spread of HIV-1 infection with nonnucleoside reverse transcriptase inhibitors

Certain bisheteroarylpiperazines (BHAPs) directly inhibit the replication of human immunodeficiency virus type 1 (HIV-1) and block the spread of infection to susceptible populations of cells. At a 1 μM concentration three analogs, U-87201, U-88204, and U-89674, inhibited the replication of HIV-1 in MT-2 cells by 83, 100, and 93%, respectively. At the same concentration, U-88204 completely inhibited replication of primary HIV-1 isolates in peripheral blood mononuclear cells. Replication of 3′-azido-2′,3′-dideoxythymidine (AZT)-resistant strains of HIV-1 was also inhibited by U-88204. When MT-2 cells that were lytically infected with HIV-1 were mixed with uninfected MT-2 cells, U-88204 provided complete protection to the uninfected cells. Integrated proviral DNA sequences were not detected by the polymerase chain reaction technique in this culture after 15 days in the presence of drug. The resultant healthy cell culture was subsequently maintained without drug with no evidence of latent proviral DNA. Serial passage of a laboratory strain and a primary isolate of HIV-1 in cell culture in the presence of increasing concentrations of U-88204 yielded virus populations which were at least 100-fold resistant to the drug. These resistant viruses also showed cross-resistance to the pyridinone class of nonnucleoside inhibitors but were sensitive to AZT. Analysis of the nucleotide sequence of resistant viruses revealed mutations at conserved regions of the reverse transcriptase (RT) gene. The results presented here suggest the therapeutic potential of U-88204 in the combination therapy for HIV-1 infection.

The binding of a novel bisheteroarylpiperazine mediates inhibition of human immunodeficiency virus type 1 reverse transcriptase.

The bisheteroarylpiperazines (BHAPs) are potent inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and specifically block HIV-1 replication (Romero, D. L., Busso, M., Tan, C.-K., Reusser, F., Palmer, J. R., Poppe, S. M., Aristoff, P. A., Downey, K. M., So, A. G., Resnick, L., and Tarpley, W. G. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 8806-8810). Here we show that the radiolabeled BHAP [3H]U-88204 binds specifically to HIV-1 RT with high affinity (KD of 50 nM) and a stoichiometry of 1 mol of U-88204 per 1 mol of p66/p51 RT heterodimer. Binding of [3H]U-88204 to RT is unaffected by the presence of saturating poly(rC).oligo (dG)12-18 template-primer. Direct measurement of competition between [3H]U-88204 and other RT inhibitors for binding to RT reveals mutually exclusive competition between [3H]U-88204 and the non-nucleoside RT inhibitor BI-RG-587 (Kopp, E. B., Miglietta, J. J., Shrutkowski, A. G., Shih, C.-K., Grob, P. M. and Skoog, M.T. (1991) Nucleic Acids Res. 19, 3035-3039), indicating that both share the same binding site. Phosphonoformate in concentrations up to 50 microM shows no competition with [3H]U-88204 for binding to RT either alone or in the presence of template-primer. Dideoxynucleotide RT inhibitors affect the binding of [3H]U-88204 to RT when complementary template-primer is present. [3H]U-88204 and the dideoxynucleotide ddGTP can bind RT simultaneously, but the presence of one ligand decreases the affinity of RT for the second. Inasmuch as ddGTP approximates the nucleotide substrate of RT, the direct demonstration of an RT-dideoxynucleotide-[3H]U-88204 complex validates the use of indirect kinetic methods to assess the strength of BHAP interaction with RT and suggests that RT inhibition by U-88204 is achieved via effects on nucleotide substrate binding.

Nonnucleoside reverse transcriptase inhibitors that potently and specifically block human immunodeficiency virus type 1 replication.

Certain bis(heteroaryl)piperazines (BHAPs) are potent inhibitors of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) at concentrations lower by 2-4 orders of magnitude than that which inhibits normal cellular DNA polymerase activity. Combination of a BHAP with nucleoside analog HIV-1 RT inhibitors suggested that together these compounds inhibited RT synergistically. In three human lymphocytic cell systems using several laboratory and clinical HIV-1 isolates, the BHAPs blocked HIV-1 replication with potencies nearly identical to those of 3'-azido-2',3'-dideoxythymidine or 2',3'-dideoxyadenosine; in primary cultures of human peripheral blood mononuclear cells, concentrations of these antiviral agents were lower by at least 3-4 orders of magnitude than cytotoxic levels. The BHAPs do not inhibit replication of HIV-2, the simian or feline immunodeficiency virus, or Rauscher murine leukemia virus in culture. Evaluation of a BHAP in HIV-1-infected SCID-hu mice (severe combined immunodeficient mice implanted with human fetal lymph node) showed that the compound could block HIV-1 replication in vivo. The BHAPs are readily obtained synthetically and have been extensively characterized in preclinical evaluations. These compounds hold promise for the treatment of HIV-1 infection.