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BMS-232632 is an azapeptide human immunodeficiency virus type 1 (HIV-1) protease (Prt) inhibitor that exhibits potent anti-HIV activity with a 50% effective concentration (EC 50 ) of 2.6 to 5.3 nM and an EC 90 of 9 to 15 nM in cell culture. Proof-of-principle studies indicate that BMS-232632 blocks the cleavage of viral precursor proteins in HIV-infected cells, proving that it functions as an HIV Prt inhibitor. Comparative studies showed that BMS-232632 is generally more potent than the five currently approved HIV-1 Prt inhibitors. Furthermore, BMS-232632 is highly selective for HIV-1 Prt and exhibits cytotoxicity only at concentrations 6,500-to 23,000-fold higher than that required for anti-HIV activity. To assess the potential of this inhibitor when used in combination with other antiretrovirals, BMS-232632 was evaluated for anti-HIV activity in two-drug combination studies. Combinations of BMS-232632 with either stavudine, didanosine, lamivudine, zidovudine, nelfinavir, indinavir, ritonavir, saquinavir, or amprenavir in HIV-infected peripheral blood mononuclear cells yielded additive to moderately synergistic antiviral effects. Importantly, combinations of drug pairs did not result in antagonistic anti-HIV activity or enhanced cytotoxic effects at the highest concentrations used for antiviral evaluation. Our results suggest that BMS-232632 may be an effective HIV-1 inhibitor that may be utilized in a variety of different drug combinations.Human immunodeficiency virus type 1 (HIV-1) protease (Prt) specifically processes gag (p55) and gag-pol (p160) viral polyproteins to yield the viral structural proteins (p17, p24, p7, and p6), as well as the viral enzymes reverse transcriptase (RT), integrase, and Prt (23,24,34 (8,9,11,12,13,19,20,30,31,(38)(39)(40)(41)43). However, use of any of these drugs as monotherapy offers only a short-term benefit due to insufficient potency and/or resistance development (3,25,31). Combination drug strategies consisting of RT and Prt inhibitors have proven to be highly effective in suppressing viral replication to unquantifiable levels for a sustained period of time

BMS-488043 is a small-molecule human immunodeficiency virus type 1 (HIV-1

Azaindole derivatives derived from the screening lead 1-(4-benzoylpiperazin-1-yl)-2-(1H-indol-3-yl)ethane-1,2-dione (1) were prepared and characterized to assess their potential as inhibitors of HIV-1 attachment. Systematic replacement of each of the unfused carbon atoms in the phenyl ring of the indole moiety by a nitrogen atom provided four different azaindole derivatives that displayed a clear SAR for antiviral activity and all of which displayed marked improvements in pharmaceutical properties. Optimization of these azaindole leads resulted in the identification of two compounds that were advanced to clinical studies: (R)-1-(4-benzoyl-2-methylpiperazin-1-yl)-2-(4-methoxy-1H-pyrrolo[2,3-b]pyridin-3-yl)ethane-1,2-dione (BMS-377806, 3) and 1-(4-benzoylpiperazin-1-yl)-2-(4,7-dimethoxy-1H-pyrrolo[2,3-c]pyridin-3-yl)ethane-1,2-dione (BMS-488043, 4). In a preliminary clinical study, 4 administered as monotherapy for 8 days, reduced viremia in HIV-1-infected subjects, providing proof of concept for this mechanistic class.

The observed in vitro and in vivo benefit of combination treatment with anti-human immunodeficiency virus (HIV) agents prompted us to examine the potential of resistance development when two protease inhibitors are used concurrently. Recombinant HIV-1 (NL4-3) proteases containing combined resistance mutations associated with BMS-186318 and A-77003 (or saquinavir) were either inactive or had impaired enzyme activity. Subsequent construction of HIV-1 (NL4-3) proviral clones containing the same mutations yielded viruses that were severely impaired in growth or nonviable, confirming that combination therapy may be advantageous. However, passage of BMS-186318-resistant HIV-1 (RF) in the presence of either saquinavir or SC52151, which represented sequential drug treatment, produced viable viruses resistant to both BMS-186318 and the second compound. The predominant breakthrough virus contained the G48V/A71T/V82A protease mutations. The clone-purified RF (G48V/A71T/V82A) virus, unlike the corresponding defective NL4-3 triple mutant, grew well and displayed cross-resistance to four distinct protease inhibitors. Chimeric virus and in vitro mutagenesis studies indicated that the RF-specific protease sequence, specifically the Ile at residue 10, enabled the NL4-3 strain with the triple mutant to grow. Our results clearly indicate that viral genetic background will play a key role in determining whether cross-resistance variants will arise.

BMS-232632 is an azapeptide human immunodeficiency virus (HIV) type 1 (HIV-1) protease inhibitor that displays potent anti-HIV-1 activity (50% effective concentration [EC 50 ], 2.6 to 5.3 nM; EC 90 , 9 to 15 nM). In vitro passage of HIV-1 RF in the presence of inhibitors showed that BMS-232632 selected for resistant variants more slowly than nelfinavir or ritonavir did. Genotypic and phenotypic analysis of three different HIV strains resistant to BMS-232632 indicated that an N88S substitution in the viral protease appeared first during the selection process in two of the three strains. An I84V change appeared to be an important substitution in the third strain used. Mutations were also observed at the protease cleavage sites following drug selection. The evolution to resistance seemed distinct for each of the three strains used, suggesting multiple pathways to resistance and the importance of the viral genetic background. A cross-resistance study involving five other protease inhibitors indicated that BMS-232632-resistant virus remained sensitive to saquinavir, while it showed various levels (0.1-to 71-fold decrease in sensitivity)-of cross-resistance to nelfinavir, indinavir, ritonavir, and amprenavir. In reciprocal experiments, the BMS-232632 susceptibility of HIV-1 variants selected in the presence of each of the other HIV-1 protease inhibitors showed that the nelfinavir-, saquinavir-, and amprenavir-resistant strains of HIV-1 remained sensitive to BMS-232632, while indinavir-and ritonavirresistant viruses displayed six-to ninefold changes in BMS-232632 sensitivity. Taken together, our data suggest that BMS-232632 may be a valuable protease inhibitor for use in combination therapy. , integrase, and Prt) (18). The Prt functions at the late stages of viral replication during virion maturation and has proved to be an effective target for antiviral intervention. Currently, five peptidic Prt inhibitors, saquinavir (SQV), indinavir (IDV), ritonavir (RTV), nelfinavir (NFV), and amprenavir (APV), are approved for clinical use (7,19,30,32,41). This class of drugs suppresses viral replication to a greater extent than the RT inhibitors in HIV-1-infected patients (12,13,24,25,27,28,42). Today, the standard care for AIDS patients involves the use of two RT inhibitors and one Prt inhibitor to reduce viremia to unquantifiable levels for an extended period of time (2, 13, 14, 27, 29; M. Markowitz, Y. Cao, A. Hurley, R. Schluger, S. Monard, R. Kost, B. Kerr, R. Anderson, S. Eastman, and D. D. Ho, 5th Conf. Retrovir. Opportunistic Infections, abstr. 371, 1998). Despite such a remarkable result, 30 to 50% of patients ultimately fail therapy, presumably due to patient nonadherence to drug schedules (as a consequence of inconvenient dosing and side effects) (43), insufficient drug exposure, and resistance development. Therefore, additional Prt inhibitors that display greater potency, improved bioavailability, fewer side effects, and distinct resistance profiles are needed.The emergence of resistant variants results from the larg...

Bis(pivaloyloxymethyl) [bis(pom)J derivatives of various acyclic nucleoside phosphonates-9-(2-phosphonylmethoxyethyl)adenine (PMEA), 9-(2-phosphonylmethoxypropyl)adenine (PMPA), and 9-(2-phosphonylmethoxypropyl)diaminopurine (PMPDAP)-were found to exhibit 9-to 23-fold greater antiviral activity than their corresponding unmodified compounds. The cytotoxicity of the bis(pom) analogs was also increased by various degrees, thus altering the therapeutic indexes of these compounds. Metabolic studies using [3H]bis-(pom)PMEA and [3H]PMEA as model compounds suggested a > 100-fold increase in the cellular uptake of the bis(pom) derivative and formation of active diphosphorylated metabolite. However, the bis(pom) derivatives were chemically unstable and highly susceptible to serum-mediated hydrolysis, factors which limit their potential utility for intracellular drug delivery.Acyclic nucleoside phosphonate analogs of both purine and pyrimidine bases show a broad-spectrum antiviral activity against several RNA and DNA viruses (reviewed in reference 4). The adenine analog, 9-(2-phosphonylmethoxyethyl)adenine (PMEA), is active against human immunodeficiency virus type 1 (HIV-1) and other retroviruses, including HIV-2, simian immunodeficiency virus, feline immunodeficiency virus, and Moloney murine sarcoma virus. PMEA is also active against various herpesviruses, including herpes simplex virus type 1 (HSV-1), HSV-2, cytomegalovirus, and Epstein-Barr virus. Thus, PMEA is of interest both as a potential antiretroviral drug for HIV-1 infections and also for the treatment of some of the opportunistic infections associated with AIDS, and it is currently undergoing a phase I and II trial for the evaluation of its toxicity and/or efficacy in AIDS patients. The related phosphonate analogs 9-(2-phosphonylmethoxypropyl)adenine (PMPA) and 9-(2-phosphonylmethoxypropyl)diaminopurine (PMPDAP) exhibit potent anti-HIV activity, although these compounds are less effective against herpesviruses. The phosphonyl groups exhibit a negative charge at the physiological pH, and hence the cellular uptake and bioavailability (in rats) of these molecules with oral drug administration are relatively poor (8). Recently, bis(pivaloyloxymethyl) [bis-(pom)] esters of the antitumor nucleotide analogs 5-fluoro-2'-deoxyuridine were shown to function as membrane-permeable prodrugs and inhibit proliferation of both wild-type and thymidine kinase-deficient murine leukemia cells (5, 9). Similarly, a bis(pom) ester of PMEA was found to have increased anti-herpes simplex virus activity in vitro compared with PMEA (11). However, the mechanisms involved in the increased activity of the bis(pom) derivative were not determined. In addition, little is known about the stability of the bis(pom) derivatives or their bioconversion to the active * Corresponding author. intracellular metabolites. In this study, we have evaluated the anti-HIV activity of bis(pom) esters of PMEA, PMPA, and PMPDAP and their metabolism in human lymphoid cell lines. Table 1 summarizes the anti-HIV ...