A 14-Day Dose-Response Study of the Efficacy, Safety, and Pharmacokinetics of the Nonpeptidic Protease Inhibitor Tipranavir in Treatment-Naive HIV-1???Infected Patients

Tipranavir: A Protease Inhibitor for HIV Salvage Therapy

Objective:

TO review the efficacy, safety, pharmacology, virology, pharmacokinetics, and resistance of the nonpeptidic protease inhibitor (PI) tipranavir.

Data Sources and Study Selection:

A PubMed search (1966–February 2006) was conducted using the key words tipranavir or PNU-140690, with the limitation of English-language reports. Pharmacokinetic and randomized clinical trials originating from major HIV conferences, such as the Conference on Retroviruses and Opportunistic Infections, International AIDS Society, European AIDS Conference, and Interscience Conference on Antimicrobial Agents and Chemotherapy, published only in abstract form, from 2000 to February 2006, were reviewed for relevance and included in this review.

Data Synthesis:

Phase III studies have shown that tipranavir is effective in the treatment of PI-resistant HIV compared with other PI-containing regimens. Adverse effects associated with tipranavir/ritonavir therapy include gastrointestinal reactions, hepatotoxicity, and elevations in cholesterol and triglyceride levels. Resistance data suggest that tipranavir/ritonavir should be reserved for salvage therapy in antiretroviral-experienced patients who have previously failed standard PI therapies. The potential for hepatotoxicity and drug interactions and the expense of tipranavir due to required ritonavir boosting may limit its widespread use.

Conclusions:

Tipranavir/ritonavir is an essential addition to the antiretroviral armamentarium for HIV-infected patients with limited treatment options.

Tipranavir/Ritonavir (500/200 mg and 500/100 mg) Was Virologically Non-Inferior to Lopinavir/Ritonavir (400/100 mg) at Week 48 in Treatment-Naïve HIV-1-Infected Patients: A Randomized, Multinational, Multicenter Trial

Ritonavir-boosted tipranavir (TPV/r) was evaluated as initial therapy in treatment-naïve HIV-1-infected patients because of its potency, unique resistance profile, and high genetic barrier. Trial 1182.33, an open-label, randomized trial, compared two TPV/r dose combinations versus ritonavir-boosted lopinavir (LPV/r). Eligible adults, who had no prior antiretroviral therapy were randomized to twice daily (BID) 500/100 mg TPV/r, 500/200 mg TPV/r, or 400/100 mg LPV/r. Each treatment group also received Tenofovir 300 mg + Lamivudine 300 mg QD. The primary endpoint was a confirmed viral load (VL) <50 copies/mL at week 48 without prior antiretroviral regimen changes. Primary analyses examined CD4-adjusted response rates for non-inferiority, using a 15% non-inferiority margin. At week 48, VL<50 copies/mL was 68.4%, 69.9%, and 72.4% in TPV/r100, TPV/r200, and LPV/r groups, respectively, and TPV/r groups showed non-inferiority to LPV/r. Discontinuation due to adverse events was higher in TPV/r100 (10.3%) and TPV/r200 (15.3%) recipients versus LPV/r (3.2%) recipients. The frequency of grade ≥3 transaminase elevations was higher in the TPV/r200 group than the other groups, leading to closure of this group. However, upon continued treatment or following re-introduction after treatment interruption, transaminase elevations returned to grade ≤2 in >65% of patients receiving either TPV/r200 or TPV/r100. The trial was subsequently discontinued; primary objectives were achieved and continuing TPV/r100 was less tolerable than standard of care for initial highly active antiretroviral therapy. All treatment groups had similar 48-week treatment responses. TPV/r100 and TPV/r200 regimens resulted in sustained treatment responses, which were non-inferior to LPV/r at 48 weeks. When compared with the LPV/r regimen and examined in the light of more current regimens, these TPV/r regimens do not appear to be the best options for treatment-naïve patients based on their safety profiles.

Pharmacokinetic Characterization of Different Dose Combinations of Coadministered Tipranavir and Ritonavir in Healthy Volunteers

PURPOSE

To characterize the steady-state pharmacokinetic combination of the nonpeptidic protease inhibitor tipranavir (TPV) with ritonavir (RTV) in 95 healthy adult volunteers, a phase 1, single-center, open-label, randomized, parallel-group trial was conducted.

METHOD

Participants received 250-mg self-emulsifying drug delivery system (SEDDS) capsules of TPV at doses between 250 mg and 1250 mg twice daily for 11 days, then received one or two RTV 100-mg SEDDS capsules, in addition to the TPV capsules, for the next 21 days.

RESULTS

Coadministration of TPV and RTV (TPV/r) resulted in a greater than 20-fold increase in steady-state TPV trough concentrations (Cssmin) as compared with TPV at steady state alone. Mean TPV Cssmin was above a preliminary target threshold of 20 microM with all but one of the RTV-boosted doses; without boosting, none of the TPV-alone doses exceeded the threshold. The average steady-state Cssmin for TPV 500 mg and 750 mg with RTV 100 mg or 200 mg were 20 to 57 times the protein-adjusted TPV IC90R49\CCR418569) for protease inhibitor-resistant HIV-1. An erythromycin breath test, a surrogate marker for cytochrome P450 isoenzyme 3A4 activity, indicated that all TPV/r combinations given provided net inhibition of this isoenzyme. The most frequent treatment-related adverse events were mild gastrointestinal symptoms.

CONCLUSION

This phase 1 study demonstrated that RTV-boosted TPV achieves concentrations that are expected to be effective in treating drug-experienced patients.

Tipranavir: a novel second-generation nonpeptidic protease inhibitor

Tipranavir is a new nonpeptidic protease inhibitor and belongs to the class of 4-hydroxy-5, 6-dihydro-2-pyrones. Chemically, tipranavir is based on coumarin and sulfonamide compounds, amongst others. It exhibits potent and specific activity against both HIV-1 and -2. Tipranavir 500 mg in combination with ritonavir 200 mg twice daily results in optimum viral load reduction and suppresses both wild-type and protease inhibitor-resistant virus. It is metabolized by the cytochrome P4503A4 enzyme and its pharmacokinetic parameters are enhanced when combined with ritonavir. Tipranavir is excreted primarily in the feces, with minimal excretion in urine. In early trials, tipranavir/ritonavir was demonstrated to be safe and well tolerated, with mild gastrointestinal side effects. Preliminary data indicate pharmacokinetic interaction with nucleotide reverse transcriptase inhibitors; however, no dose adjustments are recommended at this time. Virologic response is not adequate when combined with other ritonavir-boosted protease inhibitors, and is currently not recommended. As with other protease inhibitors, tipranavir interacts with fluconazole, atorvastatin, clarithromycin and rifabutin and absorption is reduced when taken with antacids and didanosine (enteric coated formulation). Phase III trials are underway to compare the efficacy of tipranavir/ritonavir with other antiretroviral agents.

Practical Perspectives on the Use of Tipranavir in Combination With Other Medications: Lessons Learned From Pharmacokinetic Studies

Drug-drug interactions are a major practical concern for physicians treating human immunodeficiency virus (HIV) because of the many medications that HIV-positive patients must take. Pharmacokinetic drug interactions can occur at different levels (absorption, distribution, metabolism, excretion) and are difficult to predict. Of all the processes that give rise to drug interactions, metabolism by cytochrome P450 (CYP3A) is the most frequent. Moreover, medications prescribed to HIV-positive patients may also be CYP3A inhibitors and inducers: Tipranavir, in the absence of ritonavir, is a CYP3A inducer, and ritonavir is a CYP3A inhibitor. Fortunately, the drug interactions between tipranavir coadministered with ritonavir and other antiretroviral medications or with other medications commonly used in HIV therapy are well characterized. This review summarizes the pharmacokinetic interactions between tipranavir/ritonavir and 11 other antiretroviral medications and between tipranavir/ritonavir and drugs used to treat opportunistic infections such as fungal infections, antiretroviral-treatment-related conditions such as hyperlipidemia, and side effects such as diarrhea.

Nuclear receptor-mediated induction of CYP450 by antiretrovirals: functional consequences of NR1I2 (PXR) polymorphisms and differential prevalence in whites and sub-Saharan Africans

BACKGROUND

Antiretroviral therapy including HIV protease inhibitors and nonnucleoside reverse transcriptase inhibitors can both inhibit and induce expression of cytochrome P450s, potentially leading to drug interactions. However, information is lacking on the impact of genetic polymorphism on this interaction.

METHODS

This study examines the prevalence of 33 polymorphisms in NR1I2 (pregnane X receptor [PXR]), CYP3A4, and CYP2B6 in 1013 white and sub-Saharan African patients with HIV; explores the inductive ability of 16 antiretrovirals on CYP3A4 and CYP2B6 promoter activity through nuclear receptors PXR and constitutive androstane receptor (CAR); and evaluates the influence of naturally occurring PXR genetic variants on antiretroviral activation.

RESULTS

Seventeen polymorphisms were present at different frequencies between the two ethnicities. Darunavir, fosamprenavir, lopinavir, nelfinavir, tipranavir, efavirenz, and abacavir increased CYP3A4 and/or CYP2B6 promoter activity, some through constitutive androstane receptor but mainly through PXR. Addition of low-dose ritonavir enhanced levels of CYP promoter activity for several protease inhibitors. Some PXR variants displayed lower fosamprenavir- and lopinavir-induced CYP3A4 promoter activity than the PXR reference sequence, whereas efavirenz and nelfinavir induction was unchanged.

CONCLUSIONS

The presence of NR1I2 polymorphisms can alter the induction of CYP3A4 and CYP2B6 promoter activity, potentially adding to the unpredictable nature of antiretroviral drug interactions. These polymorphisms differ in prevalence between whites and sub-Saharan Africans.

In vitro activity of antiretroviral drugs against Plasmodium falciparum

Malaria and HIV infection are both very common in many developing countries. With the increasing availability of therapy for HIV infection, it was of interest to determine whether antiretroviral drugs exert antimalarial effects. We therefore tested the in vitro activity of 19 antiretroviral drugs against the W2 and 3D7 strains of Plasmodium falciparum at concentrations up to 50 μM. None of 5 tested nucleoside reverse transcriptase inhibitors demonstrated activity. Two nonnucleoside reverse transcriptase inhibitors, efavirenz (mean 50% inhibitory concentration [IC(50)] of 22 to 30 μM against the two strains) and etravirine (3.1 to 3.4 μM), were active; nevirapine was not active. Also active were the fusion inhibitor enfuvirtide (6.2 to 7.9 μM) and the entry inhibitor maraviroc (15 to 21 μM). Raltegravir was not active. However, for all active drugs mentioned above, the IC(50)s were considerably greater than the concentrations achieved with standard dosing. The effects most likely to be clinically relevant were with HIV protease inhibitors. Of the tested compounds, activity was seen with lopinavir (2.7 to 2.9 μM), atazanavir (3.3 to 13.0 μM), saquinavir (5.0 to 12.1 μM), nelfinavir (6.5 to 12.1 μM), ritonavir (9.5 to 10.9 μM), tipranavir (15.5 to 22.3 μM), and amprenavir (28.1 to 40.8) but not darunavir. Lopinavir was active at levels well below those achieved with standard dosing of coformulated lopinavir-ritonavir. Lopinavir also demonstrated modest synergy with the antimalarial lumefantrine (mean fractional inhibitory concentration index of 0.66 for W2 and 0.53 for 3D7). Prior data showed that lopinavir-ritonavir also extends the pharmacokinetic exposure of lumefantrine. Thus, when used to treat HIV infection, lopinavir-ritonavir may have clinically relevant antimalarial activity and also enhance the activity of antimalarials.

Metabolism-mediated drug interactions associated with ritonavir-boosted tipranavir in mice

Tipranavir (TPV) is the first nonpeptidic protease inhibitor used for the treatment of drug-resistant HIV infection. Clinically, TPV is coadministered with ritonavir (RTV) to boost blood concentrations and increase therapeutic efficacy. The mechanism of metabolism-mediated drug interactions associated with RTV-boosted TPV is not fully understood. In the current study, TPV metabolism was investigated in mice using a metabolomic approach. TPV and its metabolites were found in the feces of mice but not in the urine. Principal component analysis of the feces metabolome uncovered eight TPV metabolites, including three monohydroxylated, three desaturated, one dealkylated, and one dihydroxylated. In vitro study using human liver microsomes recapitulated five TPV metabolites, all of which were suppressed by RTV. CYP3A4 was identified as the primary enzyme contributing to the formation of four TPV metabolites (metabolites II, IV, V, and VI), including an unusual dealkylated product arising from carbon-carbon bond cleavage. Multiple cytochromes P450 (2C19, 2D6, and 3A4) contributed to the formation of a monohydroxylated metabolite (metabolite III). In vivo, RTV cotreatment significantly inhibited eight TPV metabolic pathways. In summary, metabolomic analysis revealed two known and six novel TPV metabolites in mice, all of which were suppressed by RTV. The current study provides solid evidence that the RTV-mediated boosting of TPV is due to the modulation of P450-dependent metabolism.

Biotransformation and mass balance of tipranavir, a nonpeptidic protease inhibitor, when co-administered with ritonavir in Sprague-Dawley rats

In this study, tipranavir (TPV) biotransformation and disposition when co-administered with ritonavir (RTV) were characterized in Sprague-Dawley rats. Rats were administered a single intravenous (5 mg kg(-1)) or oral (10 mg kg(-1)) dose of [(14)C]TPV with co-administration of RTV (10 mg kg(-1)). Blood, urine, faeces and bile samples were collected at specified time-points over a period of 168 h. Absorption of TPV-related radioactivity ranged from 53.2-59.6%. Faecal excretion was on average 86.7% and 82.4% (intravenous) and 75.0% and 82.0% (oral) of dosed radioactivity in males and females, respectively. Urinary excretion was on average 4.06% and 6.73% (intravenous) and 9.71% and 8.28% (oral) of dosed radioactivity in males and females, respectively. In bile-duct-cannulated rats, 39.8% of the dose was recovered in bile. After oral administration, unchanged TPV accounted for the majority of the radioactivity in plasma (85.7-96.3%), faeces (71.8-80.1%) and urine (33.3-62.3%). The most abundant metabolite in faeces was an oxidation metabolite R-2 (5.9-7.4% of faecal radioactivity, 4.4-6.1% of dose). In urine, no single metabolite was found to be significant, and comprised <1% of dose. TPV when co-administered with RTV to rats was mainly excreted in feces via bile and the parent compound was the major component in plasma and faeces.

Tipranavir (TPV) genotypic inhibitory quotient predicts virological response at 48 weeks to TPV-based salvage regimens

The virological response (VR) to a tipranavir-ritonavir (TPV-RTV)-based regimen had been shown to be associated with a number of mutations in the protease gene, the use of enfuvirtide (T20), and the TPV phenotypic inhibitory quotient (IQ). The role of the TPV genotypic IQ (gIQ) has not yet been fully investigated. The aim of our study was to evaluate the relationship between the TPV gIQ and the VR at 48 weeks to TPV-based salvage regimens. Patients placed on regimens containing two nucleoside reverse transcriptase inhibitors plus TPV-RTV 500/200 mg twice a day with or without T20 were prospectively studied. Regular follow-up was performed over the study period. VR, considered a viral load (VL) decrease of >or=1 log unit and/or the achievement of <50 copies/ml with no VL rebound of >0.5 log unit compared to the maximal VL decrease at week 48, was assessed. Thirty-eight patients who had received multiple drugs were included. At week 48 the VL decrease was -1.48 (interquartile range [IQR], -2.88 to -0.48), 15 patients (39.5%) had VLs of <50 copies/ml, and the CD4+ cell count increase was 37 cells/mm3 (IQR, -30 to +175). Twenty subjects (52.6%) achieved VRs. The TPV gIQ and optimized background score (OBS) were independently associated with higher VL decreases. The TPV gIQ and OBS were also independent predictors of a VR at week 48. TPV gIQ and OBS cutoff values of 14,500 and 2, respectively, were associated with a higher rate of VR. The TPV gIQ was shown to be able to predict the VR at 48 weeks to TPV-containing salvage regimens better than the TPV trough concentration or TPV-associated mutations alone. A possible TPV gIQ cutoff value of 14,500 for reaching a VR at week 48 was suggested. Further studies are needed in order to evaluate the calculation of TPV gIQ as a new tool for the optimization of TPV-based salvage therapy.

Treatment response to ritonavir-boosted tipranavir versus ritonavir-boosted lopinavir in HIV-1 patients with higher lopinavir mutation scores

Week 48 HIV-RNA treatment response to the protease inhibitor tipranavir co-administered with ritonavir was compared with that of lopinavir co-administered with ritonavir in patients whose baseline isolates had varying lopinavir genotypic mutation scores. With increasing lopinavir mutation scores, the proportion of patients achieving a week 48 treatment response was increased in the tipranavir/ritonavir compared with the lopinavir/ritonavir arm. Tipranavir/ritonavir therapy improves treatment response rates compared with lopinavir/ritonavir in patients whose viruses have reduced susceptibility to lopinavir/ritonavir.

Tipranavir: a new option for the treatment of drug-resistant HIV infection

Tipranavir is a recently approved nonpeptidic protease inhibitor specifically developed for the management of human immunodeficiency virus (HIV) infection in treatment-experienced patients with protease inhibitor-resistant infection. It is active against a wide range of drug-resistant laboratory- and patient-derived isolates. Tipranavir requires pharmacokinetic boosting by ritonavir (200 mg) to achieve therapeutic levels with twice-daily dosing and must be administered with food for optimal absorption. It is a potent protease inhibitor with a unique drug-resistance profile that offers advantages in the management of cases of multidrug-resistant HIV infection. Tipranavir (in combination with ritonavir) is both an inhibitor and inducer of cytochrome p450, with significant potential for drug-drug interactions, and therefore, it must be used cautiously when administered to patients who are receiving other drugs. Evolution of drug resistance after treatment failure with tipranavir is complex and is not yet fully understood. There is limited overlap in the resistance mutations that predict response to tipranavir and another new protease inhibitor, darunavir, which is active against drug-resistant isolates. Tipranavir is associated with elevations in alanine aminotransferase and aspartate aminotransferase levels, as well as elevated cholesterol and triglyceride levels, and can cause the typical gastrointestinal adverse effects associated with all protease inhibitors.

Mechanisms of Pharmacokinetic and Pharmacodynamic Drug Interactions Associated with Ritonavir-Enhanced Tipranavir

Tipranavir is a nonpeptidic protease inhibitor that has activity against human immunodeficiency virus strains resistant to multiple protease inhibitors. Tipranavir 500 mg is coadministered with ritonavir 200 mg. Tipranavir is metabolized by cytochrome P450 (CYP) 3A and, when combined with ritonavir in vitro, causes inhibition of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A in addition to induction of glucuronidase and the drug transporter P-glycoprotein. As a result, drug-drug interactions between tipranavir-ritonavir and other coadministered drugs are a concern. In addition to interactions with other antiretrovirals, tipranavir-ritonavir interactions with antifungals, antimycobacterials, oral contraceptives, statins, and antidiarrheals have been specifically evaluated. For other drugs such as antiarrhythmics, antihistamines, ergot derivatives, selective serotonin receptor agonists (or triptans), gastrointestinal motility agents, erectile dysfunction agents, and calcium channel blockers, interactions can be predicted based on studies with other ritonavir-boosted protease inhibitors and what is known about tipranavir-ritonavir CYP and P-glycoprotein utilization. The highly complex nature of drug interactions dictates that cautious prescribing should occur with narrow-therapeutic-index drugs that have not been specifically studied. Thus, the known interaction potential of tipranavir-ritonavir is reported, and in vitro and in vivo data are provided to assist clinicians in predicting interactions not yet studied. As more clinical interaction data are generated, better insight will be gained into the specific mechanisms of interactions with tipranavir-ritonavir.

Steady-state disposition of the nonpeptidic protease inhibitor tipranavir when coadministered with ritonavir

The pharmacokinetic and metabolite profiles of the antiretroviral agent tipranavir (TPV), administered with ritonavir (RTV), in nine healthy male volunteers were characterized. Subjects received 500-mg TPV capsules with 200-mg RTV capsules twice daily for 6 days. They then received a single oral dose of 551 mg of TPV containing 90 microCi of [(14)C]TPV with 200 mg of RTV on day 7, followed by twice-daily doses of unlabeled 500-mg TPV with 200 mg of RTV for up to 20 days. Blood, urine, and feces were collected for mass balance and metabolite profiling. Metabolite profiling and identification was performed using a flow scintillation analyzer in conjunction with liquid chromatography-tandem mass spectrometry. The median recovery of radioactivity was 87.1%, with 82.3% of the total recovered radioactivity excreted in the feces and less than 5% recovered from urine. Most radioactivity was excreted within 24 to 96 h after the dose of [(14)C]TPV. Radioactivity in blood was associated primarily with plasma rather than red blood cells. Unchanged TPV accounted for 98.4 to 99.7% of plasma radioactivity. Similarly, the most common form of radioactivity excreted in feces was unchanged TPV, accounting for a mean of 79.9% of fecal radioactivity. The most abundant metabolite in feces was a hydroxyl metabolite, H-1, which accounted for 4.9% of fecal radioactivity. TPV glucuronide metabolite H-3 was the most abundant of the drug-related components in urine, corresponding to 11% of urine radioactivity. In conclusion, after the coadministration of TPV and RTV, unchanged TPV represented the primary form of circulating and excreted TPV and the primary extraction route was via the feces.

Efficacy and safety of three doses of tipranavir boosted with ritonavir in treatment-experienced HIV type-1 infected patients

The efficacy, safety, and pharmacokinetics of three doses of tipranavir/ritonavir (TPV/r) in highly treatment-experienced human immunodeficiency virus (HIV)-1-infected patients with protease inhibitor (PI)-resistant isolates were evaluated. A 24-week multicenter, double-blind, randomized, dose-finding trial was conducted. All patients were three-drug class experienced and had taken at least two PI-based regimens. All had at least one primary PI mutation and had plasma HIV-RNA > 1000 copies/ml. Patients remained on their background non-PI antiretroviral medications for the first 14 days. After this 14-day period of functional TPV/r monotherapy, the background antiretroviral medications were optimized based on treatment history and the screening genotype. A total of 216 patients were randomized. All groups [TPV/r 500 mg/100 mg (n = 73), 500 mg/200 mg (n = 72), and 750 mg/200 mg (n = 71) twice daily] achieved an approximate 1 log10 reduction in the median HIV-RNA at week 2. A significant reduction was sustained through 24 weeks in the TPV/r 500 mg/200 mg and 750 mg/200 mg groups. The 500 mg/200 mg dose achieved optimal median TPV trough concentrations and lower interpatient variability. The most frequently reported adverse events (AEs) were diarrhea, nausea, vomiting, fatigue, and headache. The TPV/r 750 mg/200 mg group had the highest rate of grade 3 or 4 laboratory abnormalities and study discontinuations due to AEs. All doses of TPV/r tested in this study were associated with HIV-1 viral load reductions through 24 weeks. The 500 mg/200 mg dose achieved the best efficacy, safety, and pharmacokinetic profile in this highly treatment-experienced population and was selected for the pivotal phase 3 studies.

High-performance liquid chromatography assay for the determination of the HIV-protease inhibitor tipranavir in human plasma in combination with nine other antiretroviral medications

An accurate, sensitive and simple reverse-phase (RP) high-performance liquid chromatography (HPLC) assay has been developed and validated for the simultaneous quantitative determination of tipranavir with nine other antiretroviral drugs in plasma. A liquid-liquid extraction of the drugs in tert-butylmethylether (TBME) from 200 microL of plasma is followed by a reversed phase gradient HPLC assay with UV detection at 210 nm. The standard curve for the drug was linear in the range of 80-80,000 ng/mL for tipranavir; 10-10,000 ng/mL for nevirapine, indinavir, efavirenz, and saquinavir; and 25-10,000 ng/mL for amprenavir, atazanavir, ritonavir, lopinavir, and nelfinavir. The regression coefficient (r(2)) was greater than 0.998 for all analytes. This method has been fully validated and shown to be specific, accurate and precise. Due to an excellent extraction procedure giving good recovery and a clean baseline, this method is simple, rapid, accurate and provides excellent resolution and peak shape for all analytes. Thus this method is very suitable for therapeutic drug monitoring.

Antiretroviral activity of pegylated interferon alfa-2a in patients co-infected with HIV/hepatitis C virus

OBJECTIVES

To evaluate the early anti-HIV activity of pegylated interferon (PEG-IFN) alfa-2a and ribavirin in HIV/hepatitis C virus (HCV) co-infected patients not receiving antiretroviral therapy.

PATIENTS AND METHODS

In 19 patients with baseline plasma HIV load (HIV-RNA) >1000 copies/mL treated with PEG-IFN alfa-2a and ribavirin, HIV-RNA and T-cell subsets were measured at baseline and 2, 4 and 12 weeks after initiation of anti-HCV therapy.

RESULTS

We observed a significant HIV-RNA decrease (>1 log(10) copies/mL) through week 12 of anti-HCV treatment. The magnitude of HIV-RNA decline was associated with baseline HIV-RNA, CD4 count and PEG-IFN weight-adjusted dose.

CONCLUSIONS

A significant early anti-HIV activity of PEG-IFN alfa-2a was observed. Such an effect warrants further clinical evaluation in the management of co-infected patients.

Efficacy of the Protease Inhibitors Tipranavir plus Ritonavir in Treatment-Experienced Patients: 24-Week Analysis from the RESIST-1 Trial

BACKGROUND

Improved treatment options are needed for patients infected with multidrug-resistant human immunodeficiency virus type 1 (HIV-1). The nonpeptidic protease inhibitor tipranavir has demonstrated antiviral activity against many protease inhibitor-resistant HIV-1 isolates. The Randomized Evaluation of Strategic Intervention in multi-drug reSistant patients with Tipranavir (RESIST-1) trial is an ongoing, open-label study comparing the efficacy and safety of ritonavir-boosted tipranavir (TPV/r) with an investigator-selected ritonavir-boosted comparator protease inhibitor (CPI/r) in treatment-experienced, HIV-1-infected patients.

METHODS

Six hundred twenty antiretroviral-experienced patients were treated at 125 sites in North America and Australia. Before randomization, all patients underwent genotypic resistance testing, which investigators used to select a CPI/r and an optimized background regimen. Patients were randomized to receive TPV/r or CPI/r and were stratified on the basis of preselected protease inhibitor and enfuvirtide use. Treatment response was defined as a confirmed reduction in the HIV-1 load of > or = 1 log10 less than the baseline level without treatment change at week 24.

RESULTS

Mean baseline HIV-1 loads and CD4+ cell counts were 4.74 log10 copies/mL and 164 cells/mm3, respectively. At week 24, a total of 41.5% of patients in the TPV/r arm and 22.3% in the CPI/r arm had a > or = 1-log10 reduction in the HIV-1 load (intent-to-treat population; P<.0001). Mean increases in the CD4+ cell count of 54 and 24 cells/mm3 occurred in the TPV/r and CPI/r groups, respectively. Adverse events were slightly more common in the TPV/r group and included diarrhea, nausea, and vomiting. Elevations in alanine and aspartate aminotransferase levels and in cholesterol/triglyceride levels were more frequent in the TPV/r group.

CONCLUSIONS

TPV/r demonstrated superior antiviral activity, compared with investigator-selected, ritonavir-boosted protease inhibitors, at week 24 in treatment-experienced patients with multidrug-resistant HIV-1 infection.

Ritonavir-Boosted Tipranavir Demonstrates Superior Efficacy to Ritonavir-Boosted Protease Inhibitors in Treatment-Experienced HIV-Infected Patients: 24-Week Results of the RESIST-2 Trial

BACKGROUND

Tipranavir, a novel protease inhibitor, has demonstrated antiviral activity against protease inhibitor-resistant human immunodeficiency virus type 1 (HIV-1) isolates. The Randomized Evaluation of Strategic Intervention in multi-drug reSistant patients with Tipranavir (RESIST-2) trial is an ongoing, open-label, phase III trial comparing ritonavir-boosted tipranavir (TPV/r) plus an optimized background regimen with an individually optimized, ritonavir-boosted protease inhibitor in treatment-experienced, HIV-1-infected patients.

METHODS

Patients at 171 sites in Europe and Latin America who had received > or = 2 previous protease inhibitor regimens, had triple-antiretroviral class experience, had an HIV-1 RNA level > or = 1000 copies/mL, and had genotypically demonstrated primary protease inhibitor resistance were eligible. After genotypic resistance tests were performed, a protease inhibitor and optimized background regimen were selected before randomization. Patients were randomized to receive either TPV/r or comparator protease inhibitor-ritonavir (CPI/r) and were stratified on the basis of preselected protease inhibitor and enfuvirtide use. Treatment response was defined as a confirmed HIV-1 load reduction > or = 1 log10 less than the baseline value without a treatment change at week 24.

RESULTS

A total of 863 patients were randomized and treated. At baseline, the mean HIV-1 load was 4.73 log10 copies/mL, and the mean CD4+ cell count was 218 cells/mm3. The preplanned 24-week efficacy analyses of 539 patients demonstrated treatment response rates of 41% in the TPV/r arm and 14.9% in the CPI/r arm (intent-to-treat analysis; P<.0001). The mean CD4+ cell count increased by 51 cells/mm3 in the TPV/r arm and by 18 cells/mm3 in the CPI/r arm. The most common adverse events were mild-to-moderate diarrhea, nausea, and headache. Grade 3 or greater elevations in serum transaminase, cholesterol, and triglyceride levels were more frequent in the TPV/r arm.

CONCLUSIONS

TPV/r had superior antiviral activity and increased immunologic benefits, compared with CPI/r, at week 24 among treatment-experienced patients infected with multidrug-resistant HIV-1.

Antiviral Activity, Pharmacokinetics, and Dose Response of the HIV-1 Integrase Inhibitor GS-9137 (JTK-303) in Treatment-Naive and Treatment-Experienced Patients

BACKGROUND

GS-9137 is a potent low-nanomolar strand transfer inhibitor of HIV-1 integrase.

METHODS

The antiviral activity, tolerability, pharmacokinetics, and pharmacodynamics of GS-9137 were evaluated in a randomized, double-blind, placebo-controlled monotherapy study in 40 HIV-1- infected patients not receiving antiretroviral therapy with an HIV-1 RNA between 10,000 and 300,000 copies/mL and a CD4 count of 200 cells/microL or greater. GS-9137 or matching placebo was administered with food for 10 days at 5 dosage regimens (200, 400, or 800 mg BID, 800 mg QD, or 50 mg+100 mg ritonavir QD; 6 active, 2 placebo per dose level). The primary end point was the maximum reduction from baseline in log10 HIV-1 RNA.

RESULTS

Forty patients were enrolled, with a mean baseline viral load of 4.75 log10 copies/mL and a CD4 count of 442 cells/microL. Each GS-9137 dosing regimen exhibited significant, exposure-dependent (mean reductions, -0.98 to -1.99 log10 copies/mL) antiviral activity compared with placebo (P<0.01). Twice-daily administrations of GS-9137 at doses of 400 or 800 mg or once-daily dosing of 50 mg with ritonavir demonstrated mean reductions from baseline in HIV-1 RNA of 1.91 log10 copies/mL or greater, with all patients exhibiting 1 log10 or greater and 50% having 2 log10 or greater reductions. No patient developed evidence of integrase resistance. GS-9137 showed an adverse event profile similar to placebo, and there were no study drug discontinuations.

CONCLUSIONS

GS-9137 demonstrated substantial short-term antiviral activity and was well tolerated as monotherapy, thus warranting further study.

Durable efficacy of tipranavir-ritonavir in combination with an optimised background regimen of antiretroviral drugs for treatment-experienced HIV-1-infected patients at 48 weeks in the Randomized Evaluation of Strategic Intervention in multi-drug reSistant patients with Tipranavir (RESIST) studies: an analysis of combined data from two randomised open-label trials

BACKGROUND

Treatment options for HIV-1 infected individuals who have received extensive previous antiretroviral therapy are limited. We compared efficacy and safety of the novel non-peptidic protease inhibitor tipranavir co-administered with ritonavir plus an optimised background regimen with that of an investigator-selected ritonavir-boosted comparator protease inhibitor (CPI-ritonavir) in such patients.

METHODS

We did a combined analysis of 48-week data from two ongoing, randomised, open-label, multinational, phase III, RESIST studies. HIV-1-infected adults with 3 months or longer previous triple antiretroviral class experience, two or more previous protease inhibitor regimens, HIV-1 RNA 1000 copies per mL or greater, and genotypically demonstrated primary resistance to protease inhibitor, were eligible. Primary endpoints were proportion of treatment responders (with reduction in viral load of 1 log(10) copies per mL or greater below baseline without treatment change) at 48 weeks and time to treatment failure through 48 weeks (intention-to-treat analysis). The RESIST studies are registered with ClinicalTrials.gov, numbers NCT00054717 (RESIST-1) and NCT00144170 (RESIST-2).

FINDINGS

3324 patients were screened; 746 received tipranavir-ritonavir and 737 CPI-ritonavir. 486 (65.1%) patients on tipranavir-ritonavir and 192 (26.1%) on CPI-ritonavir remained on assigned treatment until week 48. At week 48, more patients achieved and maintained treatment response in the tipranavir-ritonavir group than in the CPI-ritonavir group (251 [33.6%] vs 113 [15.3%]; p<0.0001). Median time to treatment failure was significantly longer in the tipranavir-ritonavir group than in the CPI-ritonavir group (113 days vs 0 days; p<0.0001). Gastrointestinal system disorders and raised transaminase, cholesterol, and triglycerides were more frequent in the tipranavir-ritonavir group than in the CPI-ritonavir group.

INTERPRETATION

Compared with CPI-ritonavir, tipranavir-ritonavir with an optimised background regimen provides better virological and immunological responses over 48 weeks in patients who have received extensive previous antiretroviral treatment.

Interaction of ritonavir-boosted tipranavir with loperamide does not result in loperamide-associated neurologic side effects in healthy volunteers

Loperamide (LOP) is a peripherally acting opioid receptor agonist used for the management of chronic diarrhea through the reduction of gut motility. The lack of central opioid effects is partly due to the efflux activity of the multidrug resistance transporter P-glycoprotein (P-gp) at the blood-brain barrier. The protease inhibitors are substrates for P-gp and have the potential to cause increased LOP levels in the brain. Because protease inhibitors, including tipranavir (TPV), are often associated with diarrhea, they are commonly used in combination with LOP. The level of respiratory depression, the level of pupil constriction, the pharmacokinetics, and the safety of LOP alone compared with those of LOP-ritonavir (RTV), LOP-TPV, and LOP-TPV-RTV were evaluated in a randomized, open-label, parallel-group study with 24 healthy human immunodeficiency virus type 1-negative adults. Respiratory depression was assessed by determination of the ventilatory response to carbon dioxide. Tipranavir-containing regimens (LOP-TPV and LOP-TPV-RTV) caused decreases in the area under the concentration-time curve from time zero to infinity for LOP (51% and 63% decreases, respectively) and its metabolite (72% and 77% decreases, respectively), whereas RTV caused increases in the levels of exposure of LOP (121% increase) and its metabolite (44% increase). In vitro and in vivo data suggest that TPV is a substrate for and an inducer of P-gp activity. The respiratory response to LOP in combination with TPV and/or RTV was not different from that to LOP alone. There was no evidence that LOP had opioid effects in the central nervous system, as measured indirectly by CO2 response curves and pupillary response in the presence of TPV and/or RTV.

Tipranavir

Tipranavir is a novel nonpeptidic protease inhibitor (PI) with activity against wild-type and multidrug-resistant HIV-1 both in vitro and in HIV-infected patients. Tipranavir/ritonavir 500 mg/200 mg administered twice daily for 3 weeks to healthy volunteers produced a median (range) maximum plasma concentration and minimum plasma concentration of 79.1 (34.9-111.7) mg/L and 19.5 (0.43-42.8) mg/L, respectively. Concomitant administration with low-dose ritonavir significantly increases tipranavir plasma concentrations; therefore, the recommended dose is tipranavir 500 mg and ritonavir 200 mg twice daily. Tipranavir is a substrate and inducer of cytochrome P450 3A4 isoenzyme, thus is predisposed to interactions with other agents that are substrates, inducers or inhibitors of this enzyme family. Significant drug-drug interactions have been reported with co-administration of tipranavir/ritonavir and other PIs but not with the non-nucleoside reverse transcriptase inhibitors, efavirenz and nevirapine. Tipranavir/ritonavir 500 mg/200 mg twice daily in combination with an optimised background regimen was more effective than a ritonavir-boosted comparator PI plus an optimised background regimen. The adverse effect profile for tipranavir is similar to other boosted PI regimens and most commonly includes gastrointestinal complaints. Severe adverse events that require close monitoring include hepatotoxicity and lipid abnormalities. Tipranavir retains activity in many highly treatment-experienced patients with a large number of protease mutations. Therefore, this novel PI in combination with ritonavir represents an important new choice in the treatment of multiple-PI-experienced patients.

Tipranavir: a protease inhibitor for multi-drug resistant HIV-1

Since the mid-1990s, combination therapies to treat HIV-1 infection have greatly reduced morbidity and mortality from AIDS in developed countries with access to the medications. However, the development of viral resistance to available antiretrovirals is one of the many limitations to therapy that has emerged. Of the 24 licensed antiretroviral medications and medication combinations in the US, tipranavir is one of the few agents to specifically target highly treatment-experienced patients with multi-drug resistant HIV-1. It displays activity against the virus that is cross-resistant to other protease inhibitors. In this review, issues in treating multi-drug resistant HIV-1 and the potential clinical utility of tipranavir in the US will be discussed.

Efficacy of short-term monotherapy with maraviroc, a new CCR5 antagonist, in patients infected with HIV-1

We assessed the efficacy and safety of 10-d monotherapy with the orally administered CCR5 antagonist maraviroc in 63 HIV-1-positive individuals prescreened for the absence of CXCR4-using virus. Maximum reduction in viral load occurred at a median of 10-15 d, with a mean reduction of >or=1.6 log(10) copies/ml at all twice daily doses >or=100 mg. These results provide proof of concept that CCR5 antagonism is a viable antiretroviral therapeutic approach.

[Therapeutic strategies for HIV infection: early response to antiretroviral treatment, predictive factor for the longer term response]

Despite the wide armamentarium available against the human immunodeficiency virus, the efficacy of therapeutic molecules is reduced by the selection of resistant viral strains. Several data argue in favour of an early control of viral replication ever since the first treatment: the intensity of the initial viral replication, as well as results of studies on antiretroviral drugs given as first line treatment and on the early inhibitory response of viral replication. Although an early control is essential for long-term antiviral success, the optimal time limit for the virologic response still needs to be established early knowledge of the virologic response could prove useful in the evaluation of new and more successful therapeutic combinations. Nevertheless, the impact of an earlier control of viral replication on long-term treatment efficacy and on the prevention of resistance emergence deserves further investigation.

Review: mixing new cocktails: drug interactions in antiretroviral regimens

Current highly active antiretroviral therapy (HAART) for the treatment of HIV infection requires the concomitant administration of three or four different agents, often with a high potential for drug-drug interactions. Additionally, some HIV-positive patients still require concomitant treatment with drugs for opportunistic infections, some require medication to treat unrelated medical conditions and/or the metabolic complications of antiretroviral therapy, others may self-medicate with herbal formulations and/or over-the-counter drugs, and still others many take drugs for recreational reasons or to manage addiction. Therefore, the virtually limitless number of drug combinations that may be taken by patients undergoing treatment of HIV infection makes drug-drug interactions almost inevitable. Managing these interactions is one of the major challenges associated with the multidrug regimens used for HIV therapy. This paper provides an overview of the most common interactions between antiretrovirals in the same and different classes-nucleoside analogue reverse transcriptase inhibitors (NRTI), protease inhibitors (PI), and non-nucleoside reverse transcriptase inhibitors (NNRTI)-by focusing on principles rather than specific interactions. The paper also addresses interactions between these antiretrovirals and other commonly used medications that may be prescribed concomitantly.