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At least 19 recordsLinked to original sources

PubMed2003

Enfuvirtide (T-20) cross-reactive glycoprotein 41 antibody does not impair the efficacy or safety of enfuvirtide.

The present study investigated the effect of enfuvirtide cross-reactive glycoprotein 41 (gp41) antibody on the efficacy or safety of enfuvirtide in patients participating in 1 of 2 24-week phase 3 clinical trials (T-20 vs. optimized regimen only [TORO] 1 and TORO 2). Serum samples from human immunodeficiency virus-infected patients receiving enfuvirtide plus optimized background (OB) and from patients receiving OB only were evaluated for enfuvirtide cross-reactive gp41 antibodies. Most patients had detectable levels of antibody at baseline; 78% of patients treated with enfuvirtide plus OB had a > or =30% decrease in level of antibody, compared with 43% of patients treated with OB only. Baseline antibody status did not influence virological responses to enfuvirtide-containing treatment. Favorable virological responses were more common among patients who experienced a > or =30% decrease from baseline than among those who experienced either an increase or a lesser decrease. A decrease in virus load correlated with a decrease in level of antibody. Safety was unaffected by the presence of positive antibody at any time point or change in level of antibody. There was no evidence that enfuvirtide cross-reactive gp41 antibody affects the efficacy or safety of enfuvirtide.

Adolescent↗

PubMedDate not supplied

Enfuvirtide nursing guidelines: a report from the Association of Nurses in AIDS Care Expert Panel on Enfuvirtide.

Enfuvirtide is the first of a new class of antiretrovirals know as fusion inhibitors approved for the treatment of HIV infection. It is administered via a subcutaneous injection. The patient is responsible for reconstitution from a powder and self-injection. Nurses caring for patients using enfuvirtide need a solid knowledge base about enfuvirtide administration and side effects in order to effectively educate and manage patients taking enfuvirtide. Enfuvirtide's safety and efficacy reported from phase III trials are summarized. Nursing guidelines were developed by the Association of Nurses in AIDS Care Expert Panel on Enfuvirtide. The guidelines, including suggestions on assessment, education, and management of side effects are reviewed. Teaching tools and resources are offered to assist in patient management. In addition, suggestions for proper syringe disposal and traveling with enfuvirtide are offered.

Aftercare↗

PubMed2006

Interruption of enfuvirtide in HIV-1 infected adults with incomplete viral suppression on an enfuvirtide-based regimen.

Many antiretroviral drugs continue to exert an anti-human immunodeficiency virus (HIV) benefit in the presence of drug resistance mutations. The degree to which enfuvirtide exerts continued antiviral activity in the presence of incomplete viral suppression has not been defined. To address this question, 25 subjects interrupted enfuvirtide while remaining on a stable background regimen. Enfuvirtide interruption was associated with an immediate but limited increase in plasma HIV-1 RNA levels. Enfuvirtide resistance waned rapidly in the absence of drug pressure and was no longer detectable by week 16 in most individuals. These data indicate that enfuvirtide has measurable antiviral activity in the setting of incomplete viral suppression. Although enfuvirtide resistance mutations are associated with significant fitness defects in vivo, the clinical significance of these mutations remains undefined.

Adult↗

PubMed2006

Development and validation of a quantitative assay for the measurement of two HIV-fusion inhibitors, enfuvirtide and tifuvirtide, and one metabolite of enfuvirtide (M-20) in human plasma by liquid chromatography-tandem mass spectrometry.

A method for the quantification of two peptide HIV-1 fusion inhibitors (enfuvirtide, T-20 and tifuvirtide, T-1249) and one metabolite of enfuvirtide (M-20) in human plasma has been developed and validated, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS). The analytes were extracted from plasma by solid-phase extraction (SPE) on vinyl-copolymer cartridges. Chromatographic separation of the peptides was performed on a Symmetry 300 C(18) column (50mmx2.1mm I.D., particle size 3.5 microm), using a water-acetonitrile gradient containing 0.25% (v/v) formic acid. The triple quadrupole mass spectrometer was operated in the positive ion-mode and multiple reaction monitoring (MRM) was used for peak detection. Deuterated (d60) enfuvirtide and (d50) tifuvirtide were used as internal standards. The assay was linear over a concentration range of 20-10,000 ng/ml for enfuvirtide and tifuvirtide and of 20-2000 ng/ml for M-20. Intra- and inter-assay precisions and deviations from the nominal concentrations were </=13%. Stability of the analytes was tested under all relevant conditions for sample handling. The method was capable to measure concentrations of enfuvirtide and its metabolite in plasma samples of human immunodeficiency virus type-1 (HIV-1) infected patients treated with the drug.

Enfuvirtide↗

PubMed2006

A randomized pilot study comparing combination therapy plus enfuvirtide versus a treatment interruption followed by combination therapy plus enfuvirtide.

Most individuals with multidrug-resistant HIV who switch to a new therapeutic regimen containing a single fully effective agent experience incomplete viral suppression. We postulated that interruption of antiretroviral therapy prior to the introduction of such a regimen would improve long-term virological outcomes. Thirty, three-class experienced, enfuvirtide-naive individuals with detectable drug-resistant viraemia were randomized to an immediate enfuvirtide/optimized-background treatment regimen or a 16-week treatment interruption followed by enfuvirtide/optimized-background treatment regimen. The median CD4+ T-cell count and viral load at study entry were 39 cells/mm and 4.72 log10 copies RNA/ml, respectively. There was no evidence of any virological or immunological benefit associated with the interruption. In multivariate analysis, only the baseline phenotypic susceptibility score was predictive of treatment response at week 48 (P=0.009). Only 40% of individuals had evidence of a shift in drug-resistance genotype during the interruption. In summary, interrupting therapy prior to initiating salvage therapy in patients with advanced disease did not result in an improved virological response to enfuvirtide. The collective predictive activity of an enfuvirtide-containing regimen was important in predicting treatment response.

Anti-HIV Agents↗

PubMed2005

Dynamics of enfuvirtide resistance in HIV-infected patients during and after long-term enfuvirtide salvage therapy.

Enfuvirtide (ENF) is the first of a novel class of drugs that blocks HIV fusion to host cells. We analyzed the dynamics of genotypic and phenotypic resistance to ENF during and after long-term ENF therapy and its clinical implications in eight heavily treatment-experienced HIV-infected patients who underwent salvage therapy with enfuvirtide along with other antiretroviral agents. All patients showed a rapid decline in plasma HIV-RNA followed by viral rebound. Changes at codons 36, 42, 43 and/or 44 within the HR1 region of gp41 were selected in all cases, resulting in high-level phenotypic resistance to ENF, ranging from 15- to 445-fold. Both genotypic and phenotypic resistance to ENF rapidly disappeared after discontinuation of the drug, suggesting that ENF-resistant viruses may have an impaired replicative capacity.

Amino Acid Sequence↗

PubMed2003

Uncommon mutations at residue positions critical for enfuvirtide (T-20) resistance in enfuvirtide-naive patients infected with subtype B and non-B HIV-1 strains.

Enfuvirtide (T-20) is the lead compound of the new class of antiretroviral drugs called fusion inhibitors. T-20 resistance-associated mutations located in the heptad repeat 1 (HR-1) domain of gp41 have been described in vitro and in clinical trials. In this study, the authors investigated the primary genotypic T-20 resistance in subtype B and non-B HIV-1 strains from patients at the beginning of their follow-up in the Luxembourg HIV Cohort as well as the emergence of primary resistance to T-20 in patients who had long-term infection with subtype B HIV-1 strains. HR-1 fragments including the gp41 amino acid 36-45, T-20-sensitive region were screened for amino acid variation. No classic T-20 resistance-associated mutations were identified in subtype B or non-B isolates. However, several uncommon mutations were found at residues 37, 39, and 42 for subtype B isolates and at residue 42 for a subtype non-B isolate. The results indicate that primary genotypic T-20 resistance seems to be rare in HIV-1, regardless of subtype or prior antiretroviral therapy (excluding fusion inhibitors). However, episodic variation within HR-1 can occur and needs further phenotypic evaluation in accurate fusion inhibitor resistance assays.

Anti-HIV Agents↗

PubMed2005

Impact of human immunodeficiency virus type 1 gp41 amino acid substitutions selected during enfuvirtide treatment on gp41 binding and antiviral potency of enfuvirtide in vitro.

Enfuvirtide (ENF), a novel human immunodeficiency virus type 1 (HIV-1) fusion inhibitor, has potent antiviral activity against HIV-1 both in vitro and in vivo. Resistance to ENF observed after in vitro passaging was associated with changes in a three-amino-acid (aa) motif, GIV, at positions 36 to 38 of gp41. Patients with ongoing viral replication while receiving ENF during clinical trials acquired substitutions within gp41 aa 36 to 45 in the first heptad repeat (HR-1) of gp41 in both population-based plasma virus sequences and proviral DNA sequences from isolates showing reduced susceptibilities to ENF. To investigate their impact on ENF susceptibility, substitutions were introduced into a modified pNL4-3 strain by site-directed mutagenesis, and the susceptibilities of mutant viruses and patient-derived isolates to ENF were tested. In general, susceptibility decreases for single substitutions were lower than those for double substitutions, and the levels of ENF resistance seen for clinical isolates were higher than those observed for the site-directed mutant viruses. The mechanism of ENF resistance was explored for a subset of the substitutions by expressing them in the context of a maltose binding protein chimera containing a portion of the gp41 ectodomain and measuring their binding affinity to fluorescein-labeled ENF. Changes in binding affinity for the mutant gp41 fusion proteins correlated with the ENF susceptibilities of viruses containing the same substitutions. The combined results support the key role of gp41 aa 36 to 45 in the development of resistance to ENF and illustrate that additional envelope regions contribute to the ENF susceptibility of fusion inhibitor-naïve viruses and resistance to ENF.

Amino Acid Substitution↗

PubMed2004

Enfuvirtide: a fusion inhibitor for the treatment of HIV infection.

BACKGROUND: Drug resistance continues to be a major challenge in the treatment of HIV-1 infection. Virtually all currently available antiretroviral medications inhibit the viral reverse transcriptase or protease. Enfuvirtide is the first fusion inhibitor approved by the US Food and Drug Administration for use in combination with other antiretroviral agents for the treatment of HIV-1 infection in treatment-experienced patients. OBJECTIVE: This paper describes the pharmacologic properties and clinical usefulness of enfuvirtide. METHODS: Relevant information was identified through searches of MEDLINE (1990 to October 2003), International Pharmaceutical Abstracts (1970 to October 2003), and meeting abstracts of major HIV/AIDS conferences (1996-2003) using the search terms enfuvirtide, pentafuside, T-20, DP-178, and fusion inhibitor. RESULTS: In vitro, enfuvirtide exhibits activity against HIV-1 isolates that are resistant to all other classes of anti-retroviral medications. Enfuvirtide blocks the entry of HIV-1 into host cells by interfering with virus-cell fusion, making it unique among licensed antiretroviral medications. In human adults, enfuvirtide has a volume of distribution of 5.48 L, is highly bound to plasma protein (92%), has a plasma elimination half-life of 3.8 hours, and is catabolized by peptidases and proteinases in various tissues. Dose adjustment does not appear necessary on the basis of age, race, or body weight, but may be warranted in women weighing <50 kg. A literature review did not identify any data on the disposition of enfuvirtide in patients with hepatic or renal insufficiency. Clinical trials suggest that enfuvirtide reduces plasma HIV-1 RNA levels in highly treatment-experienced patients taking an optimized antiretroviral regimen. Pivotal trials indicated a mean change in HIV-1 RNA of -1.48 log(10) copies/mL in the enfuvirtide arm at week 48, compared with -0.63 log(10) copy/mL in the control arm ( P<0.001 ). The mean absolute increase on CD4 cell count was 46 cells/mm(3) (91 cells/mm(3)) in the enfuvirtide arm vs 45 cells/mm(3) in the control arm; P<0.001 ). The most commonly reported (>15 cases per 100 patient-years of exposure) adverse events (AEs) in clinical trials included injection-site reactions, diarrhea, nausea, fatigue, insomnia, peripheral neuropathy, headache, vomiting, and fever. The most commonly reported (> or =2%) laboratory abnormalities (grade III or IV) were eosinophilia, anemia, and increases in amylase, lipase, triglycerides, creatine phosphokinase, alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transferase. In clinical trials, serious AEs leading to study discontinuation occurred in 12.9% ( 114/885 ) of patients in the enfuvirtide arm, compared with 10.7% ( 12/112 ) in the control arm ( P = NS ). The recommended dosage of enfuvirtide is 90 mg SC BID in adults and 2 mg/kg SC BID in children. Efficacy studies in children are ongoing. CONCLUSION: Although additional studies are needed, enfuvirtide appears to be a promising agent, in combination with other antiretroviral agents, for the treatment of HIV infection in treatment-experienced patients.

Clinical Trials as Topic↗

PubMed2004

Lack of interaction between enfuvirtide and ritonavir or ritonavir-boosted saquinavir in HIV-1-infected patients.

Enfuvirtide (Fuzeon) is an HIV fusion inhibitor, the first drug in a new class of antiretrovirals. The HIV protease inhibitors ritonavir and saquinavir both inhibit cytochrome P450 (CYP450) isoenzymes, and low-dose ritonavir is often used to boost pharmacokinetic exposure to full-dose protease inhibitors. These two studies were designed to assess whether ritonavir and ritonavir-boosted saquinavir influence the steady-state pharmacokinetics of enfuvirtide. Both studies were single-center, open-label, one-sequence crossover clinical pharmacology studies in 12 HIV-1-infected patients each. Patients received enfuvirtide (90 mg twice daily [bid], subcutaneous injection) for 7 days and either ritonavir (200 mg bid, ritonavir study, orally) or saquinavir/ritonavir (1000/100 mg bid, saquinavir/ritonavir study, orally) for 4 days on days 4 to 7. Serial blood samples were collected up to 24 hours after the morning dose of enfuvirtide on days 3 and 7. Plasma concentrations for enfuvirtide, enfuvirtide metabolite, saquinavir, and ritonavir were measured using validated liquid chromatography tandem mass spectrometry methods. Efficacy and safety were also monitored. Bioequivalence criteria require the 90% confidence interval (CI) for the least squares means (LSM) of C(max) and AUC(12h) to be between 80% and 125%. In the present studies, analysis of variance showed that when coadministered with ritonavir, the ratio of LSM for enfuvirtide was 124% for C(max) (90% confidence interval [CI]: 109%-141%), 122% for AUC(12h) (90% CI: 108%-137%), and 114% for C(trough) (90% CI: 102%-128%). Although the bioequivalence criteria were not met, the increase in enfuvirtide exposure was small (< 25%) and not clinically relevant. When administered with ritonavir-boosted saquinavir, the ratio of LSM for enfuvirtide was 107% for C(max) (90% CI: 94.3%-121%) and 114% for AUC(12h) (90% CI: 105%-124%), which therefore met bioequivalence criteria, and 126% for C(trough) (90% CI: 117%-135%). The pharmacokinetics of enfuvirtide are affected to a small extent when coadministered with ritonavir at a dose of 200 mg bid but not when coadministered with a saquinavir-ritonavir combination (1000/100 mg bid). However, previous clinical studies have shown that such increases in enfuvirtide exposure are not clinically relevant. Thus, no dosage adjustments are warranted when enfuvirtide is coadministered with low-dose ritonavir or saquinavir boosted with a low dose of ritonavir.

Adult↗

PubMed2003

A controlled Phase II trial assessing three doses of enfuvirtide (T-20) in combination with abacavir, amprenavir, ritonavir and efavirenz in non-nucleoside reverse transcriptase inhibitor-naive HIV-infected adults.

Enfuvirtide is a novel antiretroviral that blocks HIV-1 cell fusion and viral entry. This Phase II, controlled, open-label, randomized, multicentre dose-ranging trial explored the safety, antiviral activity and pharmacokinetics of enfuvirtide, administered by subcutaneous (s.c.) injection, in 71 HIV-1-infected, protease inhibitor-experienced, non-nucleoside reverse transcriptase inhibitor (NNRTI)-naive adults for 48 weeks. Study participants were randomized to receive enfuvirtide at a deliverable dose of 45, 67.5 or 90 mg twice daily; the 45 mg twice daily dose required 2 injections/day, while the higher doses required 4 injections/day. A background oral antiretroviral (ARV) regimen of abacavir (300 mg twice daily), amprenavir (1200 mg twice daily), ritonavir (200 mg twice daily) and efavirenz (600 mg once daily) was provided with enfuvirtide. A control group received the background ARV regimen alone. All potential participants underwent an HIV genotype at screen to ensure a homogenous population and to exclude patients with evidence of genotypic resistance to NNRTIs. Overall, the tolerability of the combination of abacavir, amprenavir, ritonavir, efavirenz and enfuvirtide was generally comparable to control through 48 weeks. No enfuvirtide dose-dependent adverse events (AEs) were observed across treatment groups. Injection site reactions (ISRs) occurred at least once in 68.5% of the enfuvirtide-treated population, and most ISRs were mild to moderate in severity, with no apparent dose relationship. Excluding ISRs, the most common treatment-emergent AEs were nausea, diarrhoea, dizziness and fatigue; with no clinically significant differences in the incidence of AEs observed between the control and enfuvirtide groups. Each treatment group benefited from ARV therapy, with a trend of increasing antiviral and immunological activity associated with increasing enfuvirtide dose. At 48 weeks, the median HIV-1 RNA change from baseline for the ITT population was -2.24 log10 copies/ml for the combined enfuvirtide groups compared with -1.87 log10 copies/ml for the control group. In addition, 54.9% of patients in the enfuvirtide group achieved HIV-1 RNA < or = 400 copies/ml versus 36.8% of patients in the control group. These results indicate that enfuvirtide has a favourable safety profile and is a promising new antiviral agent for HIV-infected patients who have been on previously failing ARV regimens.

Adult↗

PubMed2006

Continued evolution in gp41 after interruption of enfuvirtide in subjects with advanced HIV type 1 disease.

Careful examination of viral dynamics during antiretroviral treatment can provide important insights into HIV pathogenesis. We examined viral evolution during and after enfuvirtide (T-20) treatment with an objective of defining the characteristics of viral evolution during advanced HIV immunodeficiency. Specifically, we examined the viral quasispecies from nine patients who experienced incomplete viral suppression on an enfuvirtide-based regimen, and who subsequently interrupted enfuvirtide while remaining on a stable optimized background regimen (enfuvirtide "partial treatment interruption"). On average, eight clones were sequenced from three time points: pre-enfuvirtide, post-enfuvirtide failure, and post-enfuvirtide interruption. We utilized a Bayesian hierarchical phylogenetic model to assess the evolutionary relatedness of the virus that emerged over time. In most subjects, interruption of enfuvirtide was associated with continued viral evolution as enfuvirtide mutations waned; in no subject did we find clear evidence supporting the reemergence of archived wild-type variants (Bayes factor=30.2, p=0.01). Evidence supporting ongoing viral evolution was particularly strong in subjects whose virus remained diverse or became more diverse during enfuvirtide therapy. In contrast to observations when all drugs are interrupted, loss of resistance during enfuvirtide interruption is most likely due to ongoing viral evolution (and back-mutation), rather than emergence of an archived virus.

Bayes Theorem↗

PubMed2005

Safety of enfuvirtide in combination with an optimized background of antiretrovirals in treatment-experienced HIV-1-infected adults over 48 weeks.

BACKGROUND: Antiretroviral tolerability is a critical factor contributing to treatment outcome. The T-20 Versus Optimized Background Regimen Only (TORO) studies assessed the safety and efficacy of enfuvirtide in treatment-experienced HIV-1-infected patients. METHODS: A total of 997 patients were randomized at a 2:1 ratio to an optimized background antiretroviral regimen plus enfuvirtide (n = 663) or an optimized background regimen alone (control group; n = 334). Control patients could switch to enfuvirtide on virologic failure. RESULTS: In total, 26.5% of patients randomized to enfuvirtide and 36.6% to the control group discontinued study treatment before week 48; the percentage of patients withdrawn for safety reasons (including adverse events [AEs], deaths, and laboratory abnormalities) was 14.0% in the enfuvirtide group and 11.6% in the control group. Injection site reactions (ISRs) occurred in 98% of enfuvirtide patients and led to treatment discontinuation in 4.4%. Treatment-related (defined as possibly, probably, or remotely) AE rates per 100 patient-years were lower with enfuvirtide (96.2) than in the control group (149.9); diarrhea, nausea, and fatigue, the most frequently reported AEs, were significantly less frequent with enfuvirtide than in the control group. Pneumonia was significantly more frequent in patients treated with enfuvirtide (6.7 vs. 0.6 events per 100 patient-years), although the incidence was within expected ranges for this population. Lymphadenopathy was also higher in enfuvirtide-treated patients (7.1 vs. 1.2 events per 100 patient-years) for control patients. CONCLUSION: The addition of enfuvirtide to an optimized background regimen does not exacerbate AEs commonly associated with antiretrovirals. ISRs limited treatment in <5% of patients.

Adult↗

PubMed2006

A cohort study of enfuvirtide immunological and virological efficacy in clinical practice.

The aim of the study was to evaluate, under routine circumstances, the immunological and virological efficacy of antiretroviral regimens containing enfuvirtide in multi-class experienced HIV-1 infected patients. This retrospective monocentric study analyzed the clinical, immunological, and virological data of 18 HIV-1 infected patients who started enfuvirtide and completed at least 3 months of therapy. Following 3 months of enfuvirtide therapy, 11 (61%) patients had HIV-1 RNA below 400 copies/ml, among whom 8 (44%) patients below 50 copies/ml. In the ten patients still receiving enfuvirtide after 12 months, the median increase in CD4 cell count was 159 cells/microl (range, -25 to +301) and the mean decrease in HIV-1 RNA was 2.5 +/- 1.4 log(10) copies/ml; in six of these patients, viral load remained below 50 copies/ml. Five patients discontinued enfuvirtide for virological failure but none as a consequence of adverse event. Mutations located within the 36-45 amino acid domain of HR1 region of gp41 and associated to enfuvirtide resistance were found in all seven patients with persistent viral replication. In addition, a new mutation, A50V, emerged in one patient with late viral rebound. Its disappearance after treatment discontinuation suggests that it could play a role in resistance to enfuvirtide. In conclusion, enfuvirtide may be a good therapeutic option as rescue therapy in treatment-experienced patients. However, the mutations conferring resistance to enfuvirtide develop rapidly when viral load is not controlled confirming that enfuvirtide should be prescribed in association with an active background regimen.

Adult↗

PubMed2004

Long term tolerability and safety of enfuvirtide for human immunodeficiency virus 1-infected children.

BACKGROUND: Enfuvirtide, a peptide inhibitor of human immunodeficiency virus (HIV)-1-host cell membrane fusion, is the first of a new class of antiretroviral agents, the entry inhibitors. The safety and antiretroviral activity of enfuvirtide treatment of 24 weeks in HIV-1-infected children has been previously documented. Here we present the long term tolerability and safety of enfuvirtide. METHODS: Fourteen children, 4 to 12 years of age, with incompletely suppressed HIV-1 infection were evaluated. Enfuvirtide was administered twice daily by subcutaneous injection. After the first 24 weeks of enfuvirtide dosing, subjects were evaluated every 8 weeks up to 96 weeks of therapy. At each visit, each subject had a physical examination and an assessment for adverse events with particular attention to evaluation of injection site reactions. Laboratory studies obtained at each visit included hematology and blood chemistry values, plasma HIV-1 RNA concentrations and CD4+ T cell counts. RESULTS: Of 14 subjects, 6 completed at least 96 weeks of treatment. One child discontinued enfuvirtide after 22 days of treatment because of an aversion to injections, and 1 child electively discontinued after week 24 because of surgical complications unrelated to study drug. Four subjects discontinued study because of virologic failure, defined as an increase or persistence of plasma HIV-1 RNA 1.0 copies/mL above baseline, which occurred between >or =log10 weeks 40 and 63. Two children experienced grade 3 adverse events resulting in discontinuation of the study drug; 1 subject developed grade 3 thrombocytopenia and 1 developed grade 3 edema at weeks 65 and 77, respectively. Eleven of 14 children had local injection site reactions during the first 24 weeks of treatment, 4 of the 12 subjects who continued treatment beyond week 24 reported local reactions. Generally, these local reactions were 1- to 3-cm tender nodules that developed after the injections and lasted for 1-2 days. Twelve children developed new diagnoses during treatment with enfuvirtide. None was judged to be definitively related to the study drug. Thirty-six percent of children starting enfuvirtide had HIV-1 RNA levels > 1 log10 copies/mL below baseline levels at week 96. Children remaining on enfuvirtide for the entire 96 weeks had a median of 65 cells/mm and 9% increase in CD4+ T cells. CONCLUSIONS: Enfuvirtide was generally safe and, except for a high rate of injection site reactions, well-tolerated in HIV-1-infected children for as long as 96 weeks.

Child↗

PubMed2003

Lack of enzyme-inducing effect of rifampicin on the pharmacokinetics of enfuvirtide.

The primary objective was to determine whether rifampicin influences the pharmacokinetics of enfuvirtide in HIV-1-infected patients. In a single-center, open-label, one-sequence crossover, clinical pharmacology study, 12 HIV-1-infected adults received enfuvirtide (90 mg, twice daily) on days 1 to 3 and days 11 to 13 (morning dose only on days 3 and 13) and rifampicin (600 mg, once daily) from days 4 to 13. Plasma concentrations were measured for enfuvirtide and its metabolite (days 3 and 13) and rifampicin (day 13 only). The ratios of least squares means (LSM) and 90% confidence intervals for enfuvirtide and enfuvirtide metabolite pharmacokinetic parameters (AUC12h, Cmax, Ctrough) were estimated in the presence and absence of rifampicin. Treatments were compared using an analysis of variance for natural log-transformed variables, with factors patient and treatment. Efficacy and safety were also monitored. Steady-state rifampicin had no appreciable effect on any of the pharmacokinetic parameters assessed for either enfuvirtide or its metabolite. The ratio of LSM for AUC12h, Cmax, and Ctrough for enfuvirtide was 97.5%, 103%, and 84.9%, respectively, and 108%, 112%, and 92.9%, for the enfuvirtide metabolite. Rifampicin did not affect the t1/2 of enfuvirtide or its metabolite. There were no unexpected effects of rifampicin on the short-term antiviral effect or safety of the administered antiretroviral treatment. The pharmacokinetics of enfuvirtide are not induced by a 10-day pretreatment with rifampicin.

Adult↗

PubMed2005

Pharmacokinetics, pharmacodynamics and drug interaction potential of enfuvirtide.

Enfuvirtide, the first fusion inhibitor approved for the treatment of HIV-1 infection, is a synthetic peptide that binds to HIV-1 glycoprotein 41, blocking the fusion of viral and cellular membranes. When administered subcutaneously at the recommended dose of 90 mg twice daily with optimised background antiretroviral therapy, enfuvirtide significantly reduces plasma HIV-1 RNA levels up to 48 weeks compared with optimised background therapy alone. Enfuvirtide exhibits a small volume of distribution (5.48 L), low systemic clearance (1.4 L/h) and high plasma protein binding (92%). Less than 17% of enfuvirtide is converted to a minimally active deaminated form of the parent drug. Both enfuvirtide and its metabolite are primarily eliminated via catabolism to amino acid residues. Following subcutaneous administration, enfuvirtide is almost completely absorbed, and exposure increases almost linearly with dose over the range 45-180 mg. When administered at the recommended dose in adults, subcutaneous absorption is slow and protracted, resulting in relatively flat steady-state plasma concentration-time profiles. Bioavailability is high (84.3%) and the elimination half-life (3.8 hours) supports twice-daily administration. Comparable absorption was observed from three different anatomical injection sites. The pharmacokinetic-pharmacodynamic relationship indicates that the recommended dose, in combination with other active antiretrovirals, is optimal. Enfuvirtide clearance is influenced to a small extent by sex and bodyweight but this does not necessitate dosage adjustment. In vitro and in vivo studies indicate that enfuvirtide has a low potential to interact with concomitantly administered drugs. Enfuvirtide did not influence concentrations of drugs metabolised by cytochrome P450 (CYP) 3A4, CYP2D6 or N-acetyltransferase, and had only minimal effects on those metabolised by CYP1A2, CYP2E1 or CYP2C19. Coadministration of ritonavir, ritonavir-boosted saquinavir or rifampicin (rifampin) did not result in clinically significant changes in enfuvirtide pharmacokinetics. In HIV-1-infected paediatric patients, subcutaneous dosages based on bodyweight (2 mg/kg twice daily) produce pharmacokinetics broadly similar to those observed in adults administered 90 mg twice daily.

Age Factors↗

PubMed2004

Enfuvirtide: first fusion inhibitor for treatment of HIV infection.

PURPOSE: The mechanism of action, pharmacokinetics, clinical efficacy, adverse effects, and availability of enfuvirtide are discussed. SUMMARY: To date, 20 antiretrovirals have been approved by FDA for the treatment of HIV infection. The recent approval of enfuvirtide offers a new and fourth class of antiretroviral agents called fusion inhibitors. Enfuvirtide is indicated for use in treatment-experienced patients who have evidence of viral replication despite receiving current therapy. The drug is a 36-amino-acid synthetic peptide that prevents completion of the HIV fusion sequence. Absolute bioavailability after subcutaneous injection is 84%. Clinical trials indicate that adding enfuvirtide to a salvage regimen in heavily treated patients may lead to an improved virologic response. Up to a 1.48 log decrease in the viral load was seen at 48 weeks when enfuvirtide was combined with an optimized background regimen. Patients who have at least two or more active drugs in the regimen, a CD4+ cell count of >100 cells/mm3, and previous exposure to two or more antiretrovirals prior to starting enfuvirtide appear to respond best. The most common adverse effect, occurring in 98% of all enfuvirtide recipients, is an injection-site reaction that generally can be managed nonpharmacologically. A much less common but more significant concern is an increased risk of bacterial pneumonia. Enfuvirtide is available through the Fuzeon Progressive Distribution Program. The annual cost of therapy is about 24,000 dollars. CONCLUSION: Enfuvirtide is the first fusion inhibitor available for the treatment of HIV infection. The drug is indicated for use with other antiretroviral agents in treatment-experienced patients who have evidence of HIV replication despite ongoing antiretroviral treatment.

Drug Resistance↗