Enfuvirtide Research & Studies

Human immunodeficiency virus (HIV) increasing molecular diversity and emergence of drug resistant mutants remain a major concern in China. Enfuvirtide (ENF/T-20) is the first entry inhibitor used in patients failing highly active antiretroviral therapy (HAART). However, data on HIV-1 gp41genetic diversity and primary ENF resistance-associated mutations among treatment-naïve patients in China is limited. The objective was to identify molecular diversity and ENF resistance patterns of HIV-1 in southern China, using envelope (env) gp41 sequences and bioinformatics tools, which may help optimize antiretroviral therapy.

Ultrasound-mediated transdermal delivery is a promising parenteral administration method for large-molecule or unstable medications. This study evaluated skin health and systemic delivery when administering enfuvirtide, an injectable anti-retroviral medication, over a 1-mo period in a porcine model using a low-frequency cymbal transducer. Three groups received twice-daily treatments: (i) enfuvirtide injection control (n = 12); (ii) saline ultrasound control (n = 6); and (iii) enfuvirtide ultrasound treatment (n = 13). Ultrasound parameters were as follows: 30-min exposure, 90 mW/cm², 24-26 kHz and 15% duty cycle. No statistical difference in trans-epidermal water loss, a measure of skin health and function, was seen between ultrasound-treated and control skin sites for either saline (p = 0.50) or enfuvirtide (p = 0.29) groups. Average trough plasma concentrations of enfuvirtide were 0.6 ± 0.2 and 2.8 ± 0.8 μg/mL for ultrasound and injection, respectively. Tolerability and efficacy results indicate that chronic, low-frequency ultrasound exposure can be a practical means for transdermal delivery of medications such as enfuvirtide.

Enfuvirtide belongs to a newer class of antiretroviral (ARV) agents called fusion inhibitors for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. Enfuvirtide blocks attachment, binding, and entry of the viral capsid into the host CD4+ cell. Administration is only available subcutaneously in a twice-daily regimen particularly for those patients who have previously failed more than one ARV regimen. Common side effects of enfuvirtide administration include fatigue, insomnia, nausea, and diarrhea; however, injection-site reactions are the most common side effect and present in nearly all individuals undergoing treatment. The spectrum of cutaneous manifestations ranges from little to no reaction to cysts, nodules, induration, or sclerodermalike lesions. These reactions are mostly variants of iatrogenically induced hypersensitivity and are self-limited.

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.

Enfuvirtide is the first fusion inhibitor to be approved by the Food and Drug Administration for the treatment of chronic human immunodeficiency virus (HIV) infection in adults and children 6 years and older. The drug is a synthetic peptide derived from a naturally occurring amino acid sequence known as heptad repeat 2 (HR2) found in gp41, a viral transmembrane glycoprotein that facilitates fusion with host cells. By mimicking the activity of HR2 and competitively binding to a second region of gp41, heptad repeat 1 (HR1), enfuvirtide prevents interaction between HR1 and HR2 and inhibits the conformational change of gp41 that is necessary for fusion of virions to host cells. The safety and efficacy of enfuvirtide have been studied only in antiretroviral-experienced persons. Preliminary data from two multicenter phase III clinical trials (T-20 versus Optimized Regimen Only [TORO 1, TORO 2]) suggest that the drug is safe and efficacious in heavily pretreated subjects through 24 weeks. By week 24, in TORO 1 and TORO 2, respectively, mean changes in HIV RNA concentrations of -1.7 and -1.4 log10 copies/ml were observed in subjects receiving enfuvirtide plus an optimized background (OB) regimen, compared with changes of -0.8 and -0.7 log10 copies/ml in subjects receiving an OB regimen alone. Resistance to enfuvirtide has been identified in vitro and in vivo. Most resistant variants contain mutations in the HR1 region of gp41 (positions 36-45). In phase III clinical trials, numerous substitutions within this critical region were associated with faster time to virologic failure over 24 weeks. Overall, enfuvirtide appears to be well tolerated and acceptable to patients despite a high rate of injection site reactions (> 90%). Bacterial pneumonia and eosinophilia occurred more frequently in subjects taking enfuvirtide than in those taking an OB regimen alone in phase III trials; however, no causal relationship was established. Like most drugs with peptide structures, enfuvirtide appears to have a low potential for metabolic drug-drug interactions. The approved dosage is 90 mg twice/day by subcutaneous injection in adults and 2 mg/kg twice/day in children older than 6 years. Enfuvirtide is an addition to antiretroviral therapy since it targets a new step in the HIV life cycle. Given the complexity of its production and administration, however, it is likely to be most useful in antiretroviral-experienced patients.

The T-20 vs. Optimized Regimen Only Study 1 (TORO 1) was a randomized, open-label, phase 3 study of enfuvirtide (T-20), a human immunodeficiency virus type 1 (HIV-1) fusion inhibitor.

The FDA approved enfuvirtide (Fuzeon) in spring 2003 to use with other anti-HIV drugs in children age six and older and in adults who have used anti-HIV therapy before. Enfuvirtide is in a new class of drugs called entry inhibitors. The drug works at the start of HIV's reproduction cycle by blocking its ability to infect an immune cell. This occurs at the point when HIV fuses to the cell's outer wall in order to gain entry into it.