Multiple Protease Inhibitors Research Articles

In Vitro Selection of Highly Darunavir-Resistant and Replication-Competent HIV-1 Variants by Using a Mixture of Clinical HIV-1 Isolates Resistant to Multiple Conventional Protease Inhibitors

We attempted to select HIV-1 variants resistant to darunavir (DRV), which potently inhibits the enzymatic activity and dimerization of protease and has a high genetic barrier to HIV-1 development of resistance to DRV. We conducted selection using a mixture of 8 highly multi-protease inhibitor (PI)-resistant, DRV-susceptible clinical HIV-1 variants (HIV-1(MIX)) containing 9 to 14 PI resistance-associated amino acid substitutions in protease. HIV-1(MIX) became highly resistant to DRV, with a 50% effective concentration (EC(50)) ∼333-fold greater than that against HIV-1(NL4-3). HIV-1(MIX) at passage 51 (HIV-1(MIX(P51))) replicated well in the presence of 5 μM DRV and contained 14 mutations. HIV-1(MIX(P51)) was highly resistant to amprenavir, indinavir, nelfinavir, ritonavir, lopinavir, and atazanavir and moderately resistant to saquinavir and tipranavir. HIV-1(MIX(P51)) had a resemblance with HIV-1(C) of the HIV-1(MIX) population, and selection using HIV-1(C) was also performed; however, its DRV resistance acquisition was substantially delayed. The H219Q and I223V substitutions in Gag, lacking in HIV-1(C(P51)), likely contributed to conferring a replication advantage on HIV-1(MIX(P51)) by reducing intravirion cyclophilin A content. HIV-1(MIX(P51)) apparently acquired the substitutions from another HIV-1 strain(s) of HIV-1(MIX) through possible homologous recombination. The present data suggest that the use of multiple drug-resistant HIV-1 isolates is of utility in selecting drug-resistant variants and that DRV would not easily permit HIV-1 to develop significant resistance; however, HIV-1 can develop high levels of DRV resistance when a variety of PI-resistant HIV-1 strains are generated, as seen in patients experiencing sequential PI failure, and ensuing homologous recombination takes place. HIV-1(MIX(P51)) should be useful in elucidating the mechanisms of HIV-1 resistance to DRV and related agents.

Protease inhibitor-based antiretroviral therapy in treatment-naive HIV-1-infected patients: the evidence behind the options

The introduction of protease inhibitors (PIs) to HIV treatment combinations in 1996 has significantly reduced morbidity and mortality due to HIV infection. Since the 1990s, multiple PIs have been approved, with several boosted PI regimens recognized as first-line regimens in antiretroviral therapy (ART)-naive patients. While the current guidelines recommend non-nucleoside reverse transcriptase inhibitor-, PI- and integrase inhibitor-based regimens as equal alternatives in ART-naive patients, there are clearly selected patients for whom PI-based regimens appear to be the best option because of specific toxicity or dosing issues. Due to the multiple options of therapy available for ART-naive patients, providers initiating PI-based ART can individualize therapy based on patient characteristics and needs, including pre-treatment resistance, drug-drug interactions, adverse effect profiles and co-morbid conditions. Here, we discuss the current recommendations and recent guidelines, and the evidence available for various PI-based ART regimens in treatment-naive patients. We also discuss adverse effects and the use of PIs in special circumstances.

Abstract 1105: Dysregulated ΔNp63α displaces p73 from the promoter of the tumor suppressor gene maspin in keratinocytes

Abstract The p53 homologue p63 is critical for normal epidermal development. While overexpression of p63, in particular ΔNp63α, has been reported in many squamous cell cancers including those of the skin, the role of p63 in cancer pathogenesis remains unclear. We have previously shown that elevated levels of ΔNp63α aberrantly maintain keratinocyte proliferation under differentiating conditions. We performed microarray analyses of primary murine epidermal keratinocytes overexpressing adenoviral (Ad)-driven ΔNp63α vs. β-gal to identify target genes impacted by dysregulated ΔNp63α. Our studies revealed a coordinated downregulation of RNA transcripts for multiple protease inhibitors, including two members of the serine protease inhibitor (serpin) family, maspin (serpinB5) and plasminogen activator inhibitor-2, PAI-2 (serpinB2), in addition to the metalloproteinase inhibitor, tissue inhibitor of metalloproteinase-3 (TIMP-3). Downregulation of all three protease inhibitors was confirmed by RT-PCR and examined further by western analysis. TIMP-3 protein was detected in keratinocyte conditioned medium but not in whole cell lysates, supporting a primarily extracellular function for TIMP-3. PAI-2 and maspin were detected in both whole cell lysates and conditioned medium, consistent with both intracellular and extracellular roles for these proteins. Secreted levels of TIMP-3 and PAI-2 declined in Ad-ΔNp63α-cultures compared to Ad-β-gal-cultures, whereas maspin levels remained stable. Intracellular expression of both PAI-2 and maspin was negatively regulated by ΔNp63α. To investigate the mechanism by which ΔNp63α down-regulates maspin, we performed electrophoretic mobility shift assays (EMSAs) using a known p53 consensus DNA binding sequence in the maspin promoter. An endogenous complex was seen by EMSA in normal keratinocytes that was disrupted in the presence of increasing levels of ΔNp63α. Supershift analysis revealed that this endogenous complex was interrupted by the addition of a p73 antibody, but no supershift or block was seen with antibodies to p63 or p53. EMSA analysis of nuclear extracts prepared from p73(-/-) keratinocytes confirmed that p73 is required for this complex formation. The current data suggest additional roles for ΔNp63α in cancer pathogenesis by disrupting p73 transcriptional activity to down-modulate protease inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1105.

Effects of highly active antiretroviral therapy (HAART) on cholesterol in HIV‐1 infected children: a retrospective cohort study

To determine the extent to which different highly active antiretroviral therapy (HAART) regimens pose risks for hypercholesterolemia in children with perinatal HIV-1. A single center, retrospective cohort study examined different HAART regimens and total cholesterol (TC) levels. The primary outcomes were TC levels > 180, > 200 mg/dl. HAART was defined as multiple nucleoside analog reverse transcriptase inhibitors (NRTI), NRTI and protease inhibitor (PI) combinations (NRTI/PI), and NRTI and non-nucleoside analog reverse transcriptase inhibitor (NNRTI) combinations (NRTI/NNRTI). Controls were HIV-1 infected children while on no medications (No MED). Univariate and multivariable Cox regression models generated hazard ratios for each of the primary outcomes with duration of therapy in the model. Of the 178 HIV-1 infected children eligible for study, 72.4% had TC > 180 mg/dl, 53.4% had TC > 200 mg/dl. For TC > 200, the multivariable analysis showed increased risk with NRTI/NNRTI (HR: 1.86, 95%CI: 1.34-2.19) and NRTI/PI (HR: 3.45, 95%CI: 2.65-4.51) when compared to No MED. Compared to NRTI/NNRTI, NRTI/PI increased the risk for TC > 200 mg/dl (HR: 1.86, 95%CI: 1.45-2.39) in the multivariable model. In vertically acquired HIV-1 infected children, HAART elevates the risk of hypercholesterolemia. NRTI/PI increased risk of TC levels threefold, while NRTI/NNRTI increased risk twofold over No MED.

Proteochemometric Modeling of Drug Resistance over the Mutational Space for Multiple HIV Protease Variants and Multiple Protease Inhibitors

The main therapeutic targets in HIV are its protease and reverse transcriptase. A major problem in treatment of HIV is the ability of the virus to develop drug resistance by accumulating mutations in its targets. Acquiring detailed understanding of the molecular mechanisms for the interactions of drugs with mutated variants of the HIV virus is mandatory to be able to design inhibitors that can evade the resistance. Here we have used proteochemometric modeling to simultaneously analyze the interactions of 21 protease inhibitors with 72 unique protease variants. Inhibition data (pK(i)) were correlated to descriptions of chemical and structural properties of the inhibitors and proteases. The proteochemometric model obtained showed excellent fit and predictive ability (R(2)=0.92, Q(2)=0.83, Q(2)(inh)=0.78) and provided quantitative assessments for the contribution of each mutation and their combinations to the decrease in inhibitor activity, both for the whole compounds series as well as for individual compounds. The model revealed the most deleterious mutations in the protease to be D30N, V32I, G48V, I50V, I54V, V82A, I84V, and L90M. The model was further used to identify molecular properties of chemical compounds that are important for their inhibition of multimutated protease variants. Our results give directions how to design novel improved inhibitors.

The HDL proteome: a marker–and perhaps mediator–of coronary artery disease

One important cardioprotective function of HDL is to remove cholesterol from lipid-laden macrophages in the artery wall. HDL also exerts anti-inflammatory effects that might inhibit atherogenesis. However, HDL has been proposed to be dysfunctional in humans with established coronary artery disease (CAD), though the underlying mechanisms are unclear. Therefore, we used mass spectrometry to investigate the roles of HDL proteins in inflammation and cardiovascular disease. Shotgun proteomic analysis identified multiple complement regulatory proteins, protease inhibitors, and acute-phase response proteins in HDL, strongly implicating the lipoprotein in inflammation and the innate immune system. Moreover, mass spectrometry and biochemical analyses demonstrated that HDL3 from subjects with clinically significant CAD was selectively enriched in apolipoprotein E, suggesting that it carries a distinctive protein cargo in humans with atherosclerosis. HDL from CAD subjects also contained markedly elevated levels of chlorotyrosine and nitrotyrosine, two characteristic products of myeloperoxidase, indicating that oxidative damage might generate dysfunctional HDL. Aggressive lipid therapy with a statin and niacin remodeled the HDL proteome to resemble that of apparently healthy subjects. Collectively, our observations indicate that quantifying the HDL proteome by mass spectrometry should help identify novel anti-inflammatory and cardioprotective actions of HDL and provide insights into lipid therapy.

Purification and characterization of two novel cysteine protease inhibitors, Eel-CPI-2 and Eel-CPI-3, in the skin mucus of the Japanese eel Anguilla japonica

We have discovered multiple acidic cysteine protease inhibitors, in addition to the known Eel-CPI-1, in the skin mucus extract of the Japanese eel Anguilla japonica by using the two-dimensional gel system of gelatin reverse zymography. Two of the acidic inhibitors, which we have named Eel-CPI-2 and Eel-CPI-3, were purified to homogeneity by anion exchange chromatography on a column of DEAE-Sepharose CL-6B, followed by fast protein liquid chromatography on Superdex 75 10/300 GL and HiTrap Q HP columns. The amino acid compositions of Eel-CPI-2 and Eel-CPI-3 were found to be almost identical and closely similar to that of the eel galectin AJL1. The molecular masses of Eel-CPI-2 and Eel-CPI-3 were elucidated to be 16,089.080 and 16,089.137 Da, respectively, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The apparent dissociation constant of Eel-CPI-2 and Eel-CPI-3 for cysteine protease papain was determined to be 1.79 × 10−7 and 1.05 × 10−7 M, respectively, by a quartz crystal microbalance technique.

Emergence of Multiclass Drug–Resistance in HIV‐2 in Antiretroviral‐Treated Individuals in Senegal: Implications for HIV‐2 Treatment in Resouce‐Limited West Africa

The efficacy of various antiretroviral (ARV) therapy regimens for human immunodeficiency virus type 2 (HIV-2) infection remains unclear. HIV-2 is intrinsically resistant to the nonnucleoside reverse-transcriptase inhibitors and to enfuvirtide and may also be less susceptible than HIV-1 to some protease inhibitors (PIs). However, the mutations in HIV-2 that confer ARV resistance are not well characterized. Twenty-three patients were studied as part of an ongoing prospective longitudinal cohort study of ARV therapy for HIV-2 infection in Senegal. Patients were treated with nucleoside reverse-transcriptase inhibitor (NRTI)- and PI (indinavir)-based regimens. HIV-2 pol genes from these patients were genotyped, and the mutations predictive of resistance in HIV-2 were assessed. Correlates of ARV resistance were analyzed. Multiclass drug-resistance mutations (NRTI and PI) were detected in strains in 30% of patients; 52% had evidence of resistance to at least 1 ARV class. The reverse-transcriptase mutations M184V and K65R, which confer high-level resistance to lamivudine and emtricitabine in HIV-2, were found in strains from 43% and 9% of patients, respectively. The Q151M mutation, which confers multinucleoside resistance in HIV-2, emerged in strains from 9% of patients. HIV-1-associated thymidine analogue mutations (M41L, D67N, K70R, L210W, and T215Y/F) were not observed, with the exception of K70R, which was present together with K65R and Q151M in a strain from 1 patient. Eight patients had HIV-2 with PI mutations associated with indinavir resistance, including K7R, I54M, V62A, I82F, L90M, L99F; 4 patients had strains with multiple PI resistance-associated mutations. The duration of ARV therapy was positively associated with the development of drug resistance (P = .02). Nine (82%) of 11 patients with HIV-2 with no [corrected] detectable ARV resistance had undetectable plasma HIV-2 RNA loads (<1.4 log(10) copies/mL), compared with 3 (25%) of 12 patients with HIV-2 with detectable ARV resistance (P = .009). Patients with ARV-resistant virus had higher plasma HIV-2 RNA loads, compared with those with non-ARV-resistant virus (median, 1.7 log(10) copies/mL [range, <1.4 to 2.6 log(10) copies/mL] vs. <1.4 log(10) copies/mL [range, <1.4 to 1.6 log(10) copies/mL]; P = .003). HIV-2-infected individuals treated with ARV therapy in Senegal commonly have HIV-2 mutations consistent with multiclass drug resistance. Additional clinical studies are required to improve the efficacy of primary and salvage treatment regimens for treating HIV-2 infection.

SC29EK, a Peptide Fusion Inhibitor with Enhanced α-Helicity, Inhibits Replication of Human Immunodeficiency Virus Type 1 Mutants Resistant to Enfuvirtide

Peptides derived from the alpha-helical domains of human immunodeficiency virus (HIV) type 1 (HIV-1) gp41 inhibit HIV-1 fusion to the cell membrane. Enfuvirtide (T-20) is a peptide-based drug that targets the step of HIV fusion, and as such, it effectively suppresses the replication of HIV-1 strains that are either wild type or resistant to multiple reverse transcriptase and/or protease inhibitors. However, HIV-1 variants with T-20 resistance have emerged; therefore, the development of new and potent inhibitors is urgently needed. We have developed a novel HIV fusion inhibitor, SC34EK, which is a gp41-derived 34-amino-acid peptide with glutamate (E) and lysine (K) substitutions on its solvent-accessible site that stabilize its alpha-helicity. Importantly, SC34EK effectively inhibits the replication of T-20-resistant HIV-1 strains as well as wild-type HIV-1. In this report, we introduce SC29EK, a 29-amino-acid peptide that is a shorter variant of SC34EK. SC29EK blocked the replication of T-20-resistant HIV-1 strains and maintained antiviral activity even in the presence of high serum concentrations (up to 50%). Circular dichroism analysis revealed that the alpha-helicity of SC29EK was well maintained, while that of the parental peptide, C29, which showed moderate and reduced inhibition of wild-type and T-20-resistant HIV-1 strains, was lower. Our results show that the alpha-helicity in a peptide-based fusion inhibitor is a key factor for activity and enables the design of short peptide inhibitors with improved pharmacological properties.

Ritonavir-Boosted Darunavir: A Powerful Option for Treatment-Experienced Hiv-1-Infected Patients

Darunavir is a HIV protease inhibitor with potent activity in vitro against a broad range of HIV-1 strains and isolates containing multiple protease inhibitor resistance-associated mutations. Its bioavailability increases when co-administered with low-dose ritonavir, or if taken with a meal. Darunavir (in combination with ritonavir) has been approved for treatment of antiretroviral drug-experienced patients with limited therapeutic options. Clinical trials demonstrated significant efficacy with darunavir/ritonavir 600/100 mg twice daily plus optimized background regimens, with sustained response after 48 weeks and no major safety and tolerability concerns. Clinical trials assessing its efficacy in earlier treatment failure have been favorable, however, its role in the treatment of naive patients has not yet been defined.

Treatment of cells with n-alpha-tosyl- l-phenylalanine-chloromethyl ketone induces the proteolytic loss of STAT6 transcription factor

The implication of the STAT6 transcription factor in several human diseases makes the regulation of its activity a topic of great biological interest. The activation of this transcription factor is tightly regulated by kinases, phosphatases, and proteases. The initial aim of this study was to investigate the utility of protease inhibitors in controlling STAT6 activation. Among all inhibitors analyzed, n-alpha-tosyl- l-phenylalanine-chloromethyl ketone (TPCK) was found to inhibit the IL-4-induced STAT6 activation. Unexpectedly, this inhibition was accompanied by a loss of STAT6 protein. Thus, TPCK promoted the loss of STAT6 by a mechanism sensitive to the serine-protease inhibitor 4-(2-aminoetyl)-benzenesulfonyl fluoride. However, the effects of TPCK seemed not to be mediated by its protease inhibitory activity since multiple protease inhibitors tested had no effect on STAT6 expression. The results found suggest that the effect of TPCK was mediated by its alkylating activity. Thus, cysteine reactive and thiol antioxidant compounds prevented the loss of STAT6 induced by TPCK. The reactivity of thiol groups on STAT6 was moreover demonstrated with biotinylated sulfhydryl-reactive compounds. Analysis of other signaling molecules indicated that STAT5, but not other STATs, Shc, or c-Rel, was also affected by TPCK, suggesting a common downregulatory mechanism for STAT6 and STAT5. These results reveal a novel mechanism of action of TPCK in inducing a selective loss of STAT proteins. These findings may have implications for diseases in which STAT proteins are involved.

Second generation HIV protease inhibitors against resistant virus

Background: The AIDS epidemic has spread around the world at an alarming rate. Although the first generation of HIV protease inhibitors, including indinavir, nelfinavir, saquinavir, ritonavir and amprenavir, were initially effective against HIV infection, the fast emerging resistance to these agents has been a substantial and persistent problem in the treatment of AIDS. Attempts to address the resistance issue with ‘salvage therapy’ consisting of high doses of multiple protease inhibitors have only been moderately successful owing to the high level of cross-resistance and toxicities associated with the protease inhibitors. Objective: To study the second generation HIV protease inhibitors against resistant virus. Method: This review highlights new developments achieved by various organizations to address the challenge of high level resistance of current therapies since 2000. Conclusion: All second generation protease inhibitors used in patients who experienced extensive treatment require ritonavir as a pharmacological boosting agent to increase the drug level in the plasma, but there is toxicity associated with such a practice. Accordingly, there remains a need for new protease inhibitors with improved effectiveness against the resistant viral variants. A third generation protease inhibitor will require no boosting agent while maintaining high potency against resistant virus.

Prevalence and impact of HIV-1 protease mutation L76V on lopinavir resistance

Besides I47A, mutation L76V at the HIV protease gene has recently been proposed to cause lopinavir resistance. This change was present in 37 (2.7%) out of 1376 patients failing protease inhibitor containing regimens. Although 26 (70%) were on lopinavir, most had previously failed other protease inhibitors and carried multiple protease inhibitor resistance mutations. Therefore, L76V does not appear to be a primary lopinavir resistance change when the drug is used in combination therapy.

Tipranavir: the first nonpeptidic protease inhibitor for the treatment of protease resistance

Background: Despite the availability of a growing number of potent antiretroviral agents, efforts to completely suppress viral replication in patients with HIV-1 infection are limited because of the increasing risk of resistance. Tipranavir (TPV) is the first in a class of antiretroviral agents known as nonpeptidic protease inhibitors (PIs). TPV exhibits a resistance profile distinct from that of other currently available PIs, making it a potential option for treatment experienced patients with resistance to multiple Pls. Objective: This article discusses the clinical pharmacology and efficacy of TPV in the treatment of HIV-1 infection in patients who are highly treatment experienced or harbor PI-resistant virus. Methods: A search was conducted of English language, peer-reviewed articles and abstracts indexed on the MEDLINE and Current Contents databases (1966-May 2007) using the terms tipranavir, Aptivus, nonpeptidic protease inhibitor, human immunodeficiency virus, and protease resistance. Product information and abstracts from national and international AIDS and retrovirus meetings (2005-2006) were also reviewed. Results: Use of TPV in combination with ritonavir (TPV/r) was approved by the US Food and Drug Administration based on 2 Phase III studies. In these studies, HIV-infected patients with extensive treatment experience with antiretroviral agents, including PIs, nucleoside analogues, and nonnucleoside reverse transcriptase inhibitors, were randomized to receive TPV/r or a ritonavir-boosted comparator PI. All patients had evidence of resistance to multiple PIs. The specific comparator (amprenavir, indinavir, lopinavir, or saquinavir) was selected for each patient with the aid of resistance testing. Each patient also received an optimized background regimen of antiretroviral agents, which could include enfuvirtide. At 24, 48, and 96 weeks, the TPV/r group had higher rates of virologic response (defined as ≥1 log10 decrease in HIV RNA) and viral suppression (to <400 and <50 copies/mL) than did the comparator group. Conclusions: Although TPV has a mechanism of action similar to that of earlier-generation PIs, it has activity against HIV-1 strains with resistance to multiple PIs. Currently, TPV/r is indicated for use in highly treatment experienced patients with multiple PI resistance.

A Multidrug-Resistant (MDR) HIV Type 1 Infection in a Homosexual Man and Identified Source Patient

We report a case (IC) of multidrug-resistant (MDR) HIV-1 infection in which the identification of the source patient (S) was supported by phylogenetic analysis of the pol gene and by the similarity of env sequences. HIV isolates from IC and S were characterized as non-syncytium viruses: a X4 variant (R(11) E(26)) was identified in both cases according to the V3 loop sequence. The pol mutational profile of IC included multiple protease and reverse-transcriptase inhibitor mutations similar to those in S. The lamivudine/tenofovir/tipranavir/ritonavir/enfuvirtide association was effective for IC but not for S.

Myeloperoxidase and inflammatory proteins: Pathways for generating dysfunctional high-density lipoprotein in humans

High-density lipoprotein (HDL) inhibits atherosclerosis by removing cholesterol from artery wall macrophages. Additionally, HDL is anti-inflammatory in animal studies, suggesting that this property might also be important for its cardioprotective effects. Recent studies in subjects with established cardiovascular disease (CVD) demonstrate that myeloperoxidase targets HDL for oxidation and blocks the lipoprotein's ability to remove excess cholesterol from cells, raising the possibility that the enzyme provides a specific mechanism for generating dysfunctional HDL in humans. Shotgun proteomic analysis of HDL identified multiple complement regulatory proteins, protease inhibitors, and acute-phase response proteins, supporting a central role for HDL in inflammation. Mass spectrometry and biochemical analyses demonstrated that HDL(3) from CVD subjects was selectively enriched in apolipoprotein E, suggesting that it carries a unique cargo of proteins in humans with clinically significant CVD. Thus, oxidative modifications to HDL and changes in its protein composition might be useful biomarkers-and perhaps mediators-of CVD.

High-Dose Lopinavir/Ritonavir in Highly Treatment-Experienced HIV-1 Patients: Efficacy, Safety, and Predictors of Response

Objective: To investigate the efficacy and safety of high-dose lopinavir/ritonavir (LPV/r) therapy in multiple protease inhibitor, non-nucleoside reverse transcriptase inhibitor (NNRTI)-experienced subjects. Method: Thirty-six HIV-1-infected subjects were randomized to LPV/r 400/300 mg or 667/167 mg bid in a 48-week, open-label study. Subjects also received investigator-selected nucleoside reverse transcriptase inhibitors (NRTIs). Primary outcomes were the proportion of subjects with HIV-1 RNA levels <50 copies/mL at week 24 and time until loss of virologic response through week 48. Results: Six of 17 (35%) and 10 of 19 (53%) subjects in the 400/300 and 667/167 groups, respectively, completed 48 weeks of treatment. Median durations of follow-up in discontinued subjects and all subjects were 15 weeks and 32 weeks, respectively. Forty-four percent of subjects achieved HIV-1 RNA <50 copies/mL at least once; 18% (400/300 mg) and 21% (667/167 mg) of subjects achieved HIV-1 RNA <50 copies/mL at week 24 (intent-to-treat analysis). Corresponding results at week 48 were 18% (400/300 mg) and 26% (667/167 mg). No statistically significant differences in adverse event incidence occurred between treatment groups, except for a higher vomiting rate in the 400/300 mg dose group. Predictors of response included baseline LPV inhibitory quotient and number of active NRTIs. Conclusion: Higher doses of LPV/r may provide substantial antiviral activity in multiple class-experienced subjects.

Phenotypic and Structural Analyses of Hepatitis C Virus NS3 Protease Arg155 Variants: SENSITIVITY TO TELAPREVIR (VX-950) AND INTERFERON α

Phenotypic and Structural Analyses of Hepatitis C Virus NS3 Protease Arg155 Variants: SENSITIVITY TO TELAPREVIR (VX-950) AND INTERFERON α

Long-Term Efficacy and Safety of Tipranavir Boosted With Ritonavir in HIV-1-Infected Patients Failing Multiple Protease Inhibitor Regimens

BI 1182.2, an open-label, randomized, multicenter, phase 2 study, evaluated efficacy and tolerability of the protease inhibitor (PI) tipranavir (TPV; 500 mg twice daily or 1000 mg twice daily) administered with ritonavir (100 mg twice daily) in combination with 1 nucleoside reverse transcriptase inhibitor and 1 nonnucleoside reverse transcriptase inhibitor in multiple PI-experienced HIV-1-infected patients. Forty-one patients were evaluated in 2 arms: low-dose (19 patients) or high-dose (22 patients) ritonavir-boosted tipranavir (TPV/r). Primary endpoints were change from baseline in HIV-1 RNA concentrations at weeks 16, 24, 48, and 80 and percentage of patients with plasma HIV-1 RNA levels lower than the limit of quantitation. Safety was evaluated by adverse events (AEs), grade 3/4 abnormalities, and serious AEs. Of all patients, 59% were still receiving TPV/r (14 in low-dose arm and 10 in high-dose arm) at week 80. Patients in both arms had a median >2.0-log10 reduction in plasma viral load. Intent-to-treat analysis demonstrated that a similar proportion of patients in the high-dose and low-dose groups achieved plasma HIV-1 RNA levels <50 copies/mL at week 80 (43% vs. 32%; P = 0.527). The most frequently observed AEs were diarrhea, headache, and nausea. TPV/r combined with other active antiretroviral agents can provide a durable treatment response for highly treatment-experienced patients.

In Vitro Antiviral Activity and Cross-Resistance Profile of PL-100, a Novel Protease Inhibitor of Human Immunodeficiency Virus Type 1

Despite the success of highly active antiretroviral therapy, the current emergence and spread of drug-resistant variants of human immunodeficiency virus (HIV) stress the need for new inhibitors with distinct properties. We designed, produced, and screened a library of compounds based on an original l-lysine scaffold for their potentials as HIV type 1 (HIV-1) protease inhibitors (PI). One candidate compound, PL-100, emerged as a specific and noncytotoxic PI that exhibited potent inhibition of HIV-1 protease and viral replication in vitro (K(i), approximately 36 pM, and 50% effective concentration [EC(50)], approximately 16 nM, respectively). To confirm that PL-100 possessed a favorable resistance profile, we performed a cross-resistance study using a panel of 63 viral strains from PI-experienced patients selected for the presence of primary PI mutations known to confer resistance to multiple PIs now in clinical use. The results showed that PL-100 retained excellent antiviral activity against almost all of these PI-resistant viruses and that its performance in this regard was superior to those of atazanavir, amprenavir, indinavir, lopinavir, nelfinavir, and saquinavir. In almost every case, the increase in the EC(50) for PL-100 observed with viruses containing multiple mutations in protease was far less than that obtained with the other drugs tested. These data underscore the potential for PL-100 to be used in the treatment of drug-resistant HIV disease and argue for its further development.