Effective Delivery of Nef-MPER-V3 Fusion Protein Using LDP12 Cell Penetrating Peptide for Development of Preventive/Therapeutic HIV-1 Vaccine.

BACKGROUND: There is no effective and safe preventive/therapeutics vaccine against HIV-1 worldwide. Different viral proteins such as Nef, and two regions of Env including; variable loop of gp120 (V3) and membrane proximal external region of gp41 (MPER) are particularly important for vaccine development in different strategies and they are also the primary targets of cellular and humoral immune responses. On the other side, LDP12 is a new cell-penetrating peptide (CPP) which is capable of therapeutic application and cargoes delivery across the cellular membrane. OBJECTIVE: In current study, we designed and produced Nef-MPER-V3 fusion protein harboring LDP12 that has the capability of being used in future vaccine studies. METHODS: The CPP-protein was expressed in E. coli Rosseta (DE3) strain and purified through Ni-NTA column. Characterization of cellular delivery and toxicity of the recombinant protein were evaluated by western blotting and MTT assay. RESULTS: Our results showed that the CPP-protein was successfully expressed and purified with high yield of 5 mg/L. Furthermore, non-cytotoxic effect was observed and specific band (~ 37 KDa) in western blotting indicated the capability of LDP12 to improve the rate of penetration into HEK-293T cells in comparison with a control sample. CONCLUSION: Altogether, the data indicated that LDP12 CPP could be utilized to internalize HIV-1 Nef-MPER-V3 protein into eukaryotic cell lines without any toxicity and represented a valuable potential vaccine candidate and this guarantees the further evaluation towards the assessment of its immunogenicity in mice, which is currently under process.

Polyethylene Glycol 40-Modified Peptide with High Therapeutic Efficacy in Simian-Human Immunodeficiency Virus-Acutely Infected Rhesus Monkeys.

Anti-human immunodeficiency virus type 1 (anti-HIV-1) fusion peptides have been studied for nearly 2 decades, but few candidates have found useful clinical applications. One factor underlying the failure of such agents to reach the clinic is their poor pharmacokinetic properties, and many efforts have been made to overcome this problem. In this study, we modified C34, a peptide inhibitor of HIV-1 fusion, at its conserved glycosylation site using polyethylene glycols (PEGs) of different molecular weights. PEG40-NC, a conjugate of C34 and branched PEG 40 kDa (PEG40), which has been previously shown to improve the pharmacokinetic profiles of proteins, showed a significantly extended half-life (t1/2; 10.39 h in rats), which compensated for decreased in vitro activity (50% effective concentration [EC50] of 18.51 nM). PEG40-NC also showed a mechanism of action similar to that of C34. PEG40-NC monotherapy in acutely simian-human immunodeficiency virus (SHIV)-infected rhesus monkeys significantly suppressed viral load compared with a control treatment. Efficacy was linked to the extended half-life and lymphatic exposure conferred by attached PEG40. These results highlight the potential of further clinical investigations of PEG40-NC in combination with antiretroviral therapy or other anti-HIV agents.IMPORTANCE Poor pharmacokinetics have severely hindered the clinical use of anti-HIV peptides. Different small molecules, such as lipid, cholesterol, and small PEG, were designed to modify peptides to improve their pharmacokinetics. In this study, we incorporated large branched PEG to anti-HIV peptide and obtained a conjugate with extended half-life and improved in vivo efficacy. The strategy we developed in this study can also be applicable for the development of other peptide candidates.

In situ depot formation of anti-HIV fusion-inhibitor peptide in recombinant protein polymer hydrogel.

Most peptide drugs have short half-lives, necessitating frequent injections that may induce skin sensitivity reactions; therefore, versatile prolonged-release delivery platforms are urgently needed. Here, we focused on an oxidatively and thermally responsive recombinant elastin-like polypeptide with periodic cysteine residues (cELP), which can rapidly and reversibly form a disulfide cross-linked network in which peptide can be physically incorporated. As a model for proof of concept, we used enfuvirtide, an antiretroviral fusion-inhibitor peptide approved for treatment of human immunodeficiency virus (HIV) infection. cELP was mixed with enfuvirtide and a small amount of hydrogen peroxide (to promote cross-linking), and the soluble mixture was injected subcutaneously. The oxidative cross-linking generates a network structure, causing the mixture to form a hydrogel in situ that serves as an enfuvirtide depot. We fabricated a series of enfuvirtide-containing hydrogels and examined their stability, enfuvirtide-releasing profile and anti-HIV potency in vitro. Among them, hydrophobic cELP hydrogel provided effective concentrations of enfuvirtide in blood of rats for up to 8 h, and the initial concentration peak was suppressed compared with that after injection of enfuvirtide alone. cELP hydrogels should be readily adaptable as platforms to provide effective depot systems for delivery of other anti-HIV peptides besides enfuvirtide. STATEMENT OF SIGNIFICANCE: In this paper, we present an anti-HIV peptide delivery system using oxidatively and thermally responsive polypeptides that contain multiple periodic cysteine residues as an injectable biomaterial capable of in situ self-gelation, and we demonstrate its utility as an injectable depot capable of sustained release of anti-HIV peptides. The novelty of this work stems from the platform employed to provide the depot encapsulating the peptide drugs (without chemical conjugation), which consists of rationally designed, genetically engineered polypeptides that enable the release rate of the peptide drugs to be precisely controlled.

Enfuvirtide-PEG conjugate: A potent HIV fusion inhibitor with improved pharmacokinetic properties.

Enfuvirtide (ENF) is a clinically used peptide drug for the treatment of HIV infections, but its poor pharmacokinetic profile (T1/2 = 1.5 h in rats) and low aqueous solubility make the therapy expensive and inconvenience. In this study, we present a simple and practical strategy to address these problems by conjugating ENF with polyethylene glycol (PEG). Site-specific attachment of a 2 kDa PEG at the N-terminus of ENF resulted in an ENF-PEG (EP) conjugate with high solubility (≥3 mg/mL) and long half-life in rats (T1/2 = 16.1 h). This conjugate showed similar antiviral activity to ENF against various primary HIV-1 isolates (EC50 = 6-91 nM). Mechanistic studies suggested the sources of the antiviral potency. The conjugate bound to a functional domain of the HIV gp41 protein in a helical conformation with high affinity (Kd = 307 nM), thereby inhibiting the gp41-mediated fusion of viral and host-cell membranes. As PEG conjugation has advanced many bioactive proteins and peptides into clinical applications, the EP conjugate described here represents a potential new treatment for HIV infections that may address the unmet medical needs associated with the current ENF therapy.

Continuous intravenous infusion of enfuvirtide in a patient with a multidrug-resistant HIV strain.

Case description To evaluate whether continuous intravenous (i.v.) administration of enfuvirtide (T20) could be a suitable alternative to subcutaneous (s.c.) administration of T20 in a patient with extensively drug-resistant HIV experiencing difficulties administering T20 subcutaneously. T20 was administered to a patient through 100 mL cassettes once daily via a CADD. Plasma samples were drawn and the pharmacokinetic profile compared to that of s.c. twice daily administration of T20. Also, viral replication and CD4+ count were monitored over a period of 9 months for this study. Continuous i.v. administration of T20 resulted in significantly higher T20 plasma levels compared to s.c. administration, continued viral suppression, a rise in CD4+ count and strong patient preference over s.c. administration. Conclusion This method of T20 administration may be a suitable alternative for selected patients who are not able to tolerate it when given subcutaneously. It may even be considered a priori in selected patients with extensive viral resistance who are unable or unwilling to inject T20 subcutaneously.

Sustained release of the candidate antiretroviral peptides T-1249 and JNJ54310516-AFP from a rod insert vaginal ring.

Administration of biomacromolecular drugs in effective quantities from conventional vaginal rings is hampered by poor drug permeability in the polymers from which rings are commonly constructed. Here, we report the formulation development and testing of rod insert rings for sustained release of the candidate antiretroviral peptides T-1249 and JNJ54310516-AFP (JNJ peptide), both of which have potential as HIV microbicides. Rod inserts were prepared comprising antiviral peptides T-1249 or JNJ peptide in combination with a hydrophilic excipient (sodium chloride, sodium glutamate, lactose or zinc acetate) dispersed at different loadings within a medical grade silicone elastomer. The inserts were tested for weight change and swelling when immersed in simulated vaginal fluid (SVF). Dye migration into the inserts was also assessed visually over 28 days. In vitro release of T-1249 and JNJ peptide from rings containing various insert types was tested. Weight change and degree of swelling of rods immersed in SVF was dependent on the type and concentration of excipient present. The rods displayed the following rank order in terms of weight change: sodium glutamate > zinc acetate ≈ sodium chloride > lactose. The weight change and degree of swelling of the inserts did not correlate with the level of dye uptake observed. In vitro release of T-1249 was improved through addition of lactose, sodium chloride and sodium glutamate, while release of JNJ peptide was improved through addition of sodium chloride or sodium glutamate. Sustained release of hydrophobic peptides can be achieved using a rod insert ring design formulated to include a hydrophilic excipient. Release rates were dependent upon the type of excipient used. The degree of release improvement with different inserts partially reflects their ability to imbibe surrounding fluid and swell in aqueous environments.

Half-life extension of the HIV-fusion inhibitor peptide TRI-1144 using a novel linker technology.

We have previously developed a linker technology for half-life extension of peptides, proteins and small molecule drugs (1). The linkers undergo ß-elimination reactions with predictable cleavage rates to release the native drug. Here we utilize this technology for half-life extension of the 38 amino acid HIV-1 fusion inhibitor TRI-1144. Conjugation of TRI-1144 to 40 kDa PEG by an appropriate ß-eliminative linker and i.v. administration of the conjugate increased the in vivo half-life of the released peptide from 4 to 34 h in the rat, and the pharmacokinetic parameters were in excellent accord with a one-compartment model. From these data we simulated the pharmacokinetics of the PEG-TRI-1144 conjugate in humans, predicting a t1/2,ß of 70 h for the released peptide, and that a serum concentration of 25 nM could be maintained by weekly doses of 8 µmol of the conjugate. Using a non-circulating carrier (2) similar simulations indicated a t1/2,ß of 150 h for the peptide released from the conjugate and that dosing of only 1.8 µmol/week could maintain serum concentrations of TRI-1144 above 25 nM. Hence, releasable ß-eliminative linkers provide significant half-life extension to TRI-1144 and would be expected to do likewise for related peptides.

Enfuvirtide and cutaneous injection-site reactions.

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.

In situ forming implant for controlled delivery of an anti-HIV fusion inhibitor.

An injectable, phase sensitive, in situ forming, implantable delivery system was developed for enfuvirtide, a therapeutic peptide used in the treatment of HIV infection. The development studies were carried out using poly (D,L-lactide-co-glycolide), a smart, biodegradable polymer. Different formulations were designed, prepared and evaluated by employing response surface, optimal design of experiment technique. The optimized formulation was identified and validated for its performance by using numerical optimization technique. The in vitro evaluation parameters included rheology, compatibility studies, drug release as well as conformational and physicochemical stability studies. In vivo pharmacokinetic parameters and biocompatibility studies were determined in rat models and were statistically analyzed. It was found that the optimized formulation extended the enfuvirtide release and maintained the drug plasma concentration within therapeutically effective range up to 48 h. The optimized formulation maintained physicochemical and conformational stability for at least 6 months and was biocompatible with the animal tissue.

Pharmacokinetics of antiretroviral drugs in anatomical sanctuary sites: the fetal compartment (placenta and amniotic fluid).

HIV resides within anatomical 'sanctuary sites' where local drug exposure and viral dynamics may differ significantly from the systemic compartment. Widespread implementation of antiretroviral therapy has seen a significant decline in the incidence of mother-to-child transmission (MTCT) of HIV. In addition to suppression of maternal plasma/genital viral loads, antiretroviral agents that cross the placenta and achieve adequate concentrations in the fetal compartment may exert a greater prophylactic effect. Penetration of antiretrovirals in the fetal compartment is expressed by accumulation ratios derived from the measurement of drug concentrations in paired maternal plasma and umbilical cord samples. The nucleoside analogues and nevirapine accumulate extensively in cord blood and in the surrounding amniotic fluid, whereas the protease inhibitors (PIs) exhibit low-to-moderate placental accumulation. Early data suggest that high placental/neonatal concentrations are achieved with raltegravir, but to a lesser extent with etravirine and maraviroc (rank order of accumulation: raltegravir/nucleoside reverse transcriptase inhibitor [tenofovir > zidovudine/lamivudine/emtricitabine/stavudine/abacavir] > non-nucleoside reverse transcriptase inhibitor [nevirapine > etravirine] > PI > maraviroc/enfuvirtide). More comprehensive in vivo pharmacokinetic data are required to justify the potential use of these agents as safe and effective options during pregnancy.

Switch from enfuvirtide to raltegravir lowers plasma concentrations of darunavir and tipranavir: a pharmacokinetic substudy of the EASIER-ANRS 138 trial.

We compared tipranavir and darunavir concentrations measured at steady state in 20 human immunodeficiency virus (HIV)-infected patients enrolled in the EASIER-ANRS 138 clinical trial who switched from enfuvirtide to raltegravir while maintaining the same background regimen. The geometric mean ratios of the observed predose concentration (C(trough)), maximum concentration of drug observed in plasma (C(max)), and area under the plasma concentration-time curve (AUC) before (day 0) and after (week 24) the switch were 0.49, 0.76, and 0.67 and 0.82, 0.68, and 0.64 for tipranavir and darunavir, respectively. The virologic consequences of these drug interactions have yet to be determined.

Pharmacokinetic profile in late pregnancy and cord blood concentration of tipranavir and enfuvirtide.

The data on the use of tipranavir and enfuvirtide in pregnancy are very limited. We performed a pharmacokinetic profile in a pregnant woman with multidrug-resistant HIV-1 infection at 37 weeks gestation. Tipranavir levels were in the therapeutic range and the cord blood concentration at delivery was relatively high when compared with other protease inhibitors. No enfuvirtide was detected in the fetal compartment. Tipranavir and enfuvirtide were successfully used in pregnancy, but possible toxicities must be kept in mind.

Enfuvirtide: from basic investigations to current clinical use.

IMPORTANCE OF THE FIELD: Drug resistance is a major challenge in the treatment of HIV infection. Enfuvirtide is the first entry inhibitor to have been approved for clinical use. AREAS COVERED IN THIS REVIEW: Relevant information through searches of MEDLINE (1998 to June 2010) and meeting abstracts of major HIV/AIDS conferences (2003 - June 2010) using the search terms 'enfuvirtide', 'T-20' and 'fusion inhibitor'. WHAT THE READER WILL GAIN: Enfuvirtide blocks HIV fusion to host cells. It works against the different HIV-1 variants but is not active against HIV-2. The recommended dosage of enfuvirtide is 90 mg b.i.d. subcutaneously. The two large Phase III pivotal clinical trials TORO 1 and 2 showed that enfuvirtide is an effective therapeutic option as rescue therapy in combination with other active antiretroviral drugs. Resistance to enfuvirtide is conferred by mutations in the HR1 region of gp41. Single and double mutations have been shown to result in high-level resistance to enfuvirtide. Postmarketing studies have been helpful to define more precisely the place of enfuvirtide in the sequence of antiretroviral therapy. TAKE HOME MESSAGE: The emergence of new compounds and new classes of drugs, highly active against multiresistant virus but more convenient to administer than enfuvirtide, will probably prevent the extensive use of enfuvirtide. This drug remains attractive in some subgroups of patients because of its excellent systemic tolerance and the lack of interactions with the major cytochrome P450 isoenzymes.

Short communication safety, tolerability and pharmacokinetics of enfuvirtide administered by a needle-free injection system compared with subcutaneous injection.

BACKGROUND: Injection site reactions (ISRs) can present a challenge to patients when using enfuvirtide (ENF). This study compared ISRs associated with use of a needle-free injection device (NFID) with those associated with a standard 27-gauge half-inch needle/syringe (NS). METHODS: In this single-blind, crossover study, 58 ENF-naive participants were randomized to self-administer ENF with the NFID for 4 weeks (followed by 4 weeks using NS) or with the NS for 4 weeks (followed by 4 weeks using the NFID). A primary composite endpoint of painful ISR was defined as the combination of grade 1-3 ongoing pain plus either associated grade 3-4 (> or =25 mm) induration or grade 2-4 nodules/cysts (>20 mm). An ISR summary score described ISR frequency/severity. Self-reported device preference was also evaluated at baseline and at study completion. RESULTS: Fewer participants using NFID experienced the primary composite endpoint of painful ISRs (10/28; 35.7%) compared with NS (20/28; 71.4%) (P=0.004). There was a trend towards a reduced incidence/severity of ISR signs and symptoms with NFID, with significant reductions seen in pain/discomfort and pruritus (P<0.05 and P<0.01, respectively). At the end of the study, most participants (22/25; 88%) expressed a preference for NFID. Haematoma was the sole NFID-related serious adverse event, but this did not lead to discontinuation. CONCLUSIONS: Compared with a standard NS, use of an NFID to administer ENF was associated with a substantially lower incidence of painful ISRs, was generally safe and well-tolerated, and was preferred by most participants in the study.

Reassessment of enfuvirtide's role in the management of HIV-1 infection.

BACKGROUND: The development of new protease inhibitors, new non-nucleoside reverse transcriptase inhibitors and novel therapeutic drug classes has dramatically changed the approach to managing HIV-1 patients with multidrug resistant virus. This has led many clinicians to reevaluate the clinical utility of enfuvirtide. OBJECTIVES: To summarize recent literature on enfuvirtide and to reassess enfuvirtide's role in the management of HIV-1 infection. METHODS: MEDLINE (1990 to February Week 2 2008) and EMBASE (1990 to 2008 week 8) databases were searched using the following terms: 'enfuvirtide', 'Fuzeon', 'T20', 'HIV fusion inhibitors', and 'HIV entry inhibitor'; limits: English language. Reference lists of articles deemed relevant were hand searched for additional publications. Significant abstracts from recent international HIV conferences were also identified. CONCLUSION: Enfuvirtide can optimize the response to new combinations of HIV-1 drug regimens in multiresistant patients. Its inclusion as an active agent is effective but use is impacted by its high cost, inconvenient route of administration and cosmetic side-effect profile.

Enfuvirtide cerebrospinal fluid (CSF) pharmacokinetics and potential use in defining CSF HIV-1 origin.

BACKGROUND: Enfuvirtide is a potent inhibitor of systemic HIV-1 replication, but its penetration into the human central nervous system (CNS) has not been analysed. Here, we define cerebrospinal fluid (CSF) enfuvirtide pharmacokinetics and present a case illustrating the use of enfuvirtide as a probe to trace the origins of CSF HIV-1 quasispecies. METHODS: Enfuvirtide CSF pharmacokinetics were assessed in 18 CSF and plasma sample pairs from four HIV-1-infected individuals. Enfuvirtide levels were measured by liquid chromatography tandem mass spectrometry using known standards and controls that included spiked CSF samples from untreated, HIV-negative individuals. A segment of the gp41 coding region encompassing the heptad repeat HR-1 and HR-2 domains was amplified from selected CSF and plasma samples and independent clones sequenced to assess resistance-associated mutations. RESULTS: CSF and plasma samples obtained between 2 and 20 h after enfuvirtide injection showed plasma concentrations similar to previous reports (mean 3.687 SD +/- 1.828 mg/ml) with prolonged decay. By contrast, enfuvirtide in all CSF samples was below the assay detection limit of 0.025 mg/ml. In one individual, who developed a transient increase in CSF HIV-1 RNA, seven of seven CSF and plasma clones had identical enfuvirtide resistance-associated V38A mutations, suggesting that the CSF quasispecies derived from that of blood. CONCLUSIONS: Enfuvirtide penetration into CSF is negligible; thus, in clinical settings, where direct CNS drug exposure is crucial, this drug Is not likely to directly contribute to the local therapeutic effect. Enfuvirtide can be used as a tool to dissect the origin of the CNS virus.

Efficacy and safety of 48 weeks of enfuvirtide 180 mg once-daily dosing versus 90 mg twice-daily dosing in HIV-infected patients.

PURPOSE: To evaluate the safety and antiviral activity of once-daily (qd) enfuvirtide (ENF) compared with twice daily (bid) ENF. METHOD: T20-401 was a phase 2, open-label, randomized, 48-week pilot study comparing ENF 180 mg qd versus ENF 90 mg bid, added to an optimized background (OB) regimen. Patients were randomized 1:1 to receive ENF 180 mg qd given as two 90-mg injections (n = 30) or one 90-mg injection bid (n = 31), plus OB. The primary efficacy endpoint was the proportion of patients achieving a HIV-1 RNA viral load <400 copies/mL. Adherence, pharmacokinetics, safety, and tolerability parameters, including injection site reactions (ISRs), were compared between treatment arms. RESULTS: At Week 48, 23.3% of patients on once daily versus 22.6% on twice daily (p = .969) reached <400 copies/mL and 13.3% and 22.6% (p = .323), respectively, reached <50 copies/mL. The proportion reporting 1 adverse event or ISRs was comparable between arms, despite an increased incidence of grade 4 erythema (13% vs. 0%), induration (33% vs. 12%), and ecchymosis (7% vs. 0%) on twice daily versus once daily. ENF adherence (95% of prescribed doses) was higher on once daily (80.0%) versus twice daily (58.1%). CONCLUSION: The antiviral efficacy, safety, and tolerability of 180 mg ENF qd appeared comparable with that of 90 mg ENF bid at Week 48, although the study was not powered to demonstrate the noninferiority of once daily versus twice daily.

Pharmacokinetic and pharmacodynamic determinants of early virological response to enfuvirtide-based regimens in HIV-positive patients.

BACKGROUND: Early virological response (VR) to enfuvirtide-based salvage regimens at week 12 has been described as a predictor of long-term therapeutic success. The relationship between enfuvirtide plasma exposure and VR has not yet been investigated in the clinical setting. Our aim was to investigate the role of enfuvirtide plasma exposure as a determinant of early VR in the clinical setting. METHODS: Forty-two multidrug-experienced patients starting a salvage enfuvirtide-based regimen were prospectively evaluated over a 12 week period. HIV-RNA levels and enfuvirtide C(trough) were regularly measured. VR was considered as achievement of viral load (VL) undetectability and/or a decrease of more than 1 log at week 12. RESULTS: Optimized background score (OBS) and enfuvirtide C(trough) concentrations were associated with VL decrease at week 12. An OBS > or =2 and enfuvirtide C(trough) >2100 ng/mL were associated with VR. The pharmacokinetic/pharmacodynamic (PK/PD) analysis confirmed this exposure-response relationship both in the total population and in different groups according to OBS <2 or > or =2. Higher estimates of IC(50) were calculated for the OBS <2 group when compared with the OBS > or =2 group (7551 versus 2330 ng/mL, respectively), without a marked difference in I(0) (0.31 versus 0.21 log) and I(max) (-2.64 versus -3.33 log). CONCLUSIONS: Enfuvirtide plasma exposure and OBS were found to significantly influence the magnitude and rate of early VR. The PK/PD modelling of enfuvirtide concentrations was different in our clinical setting, compared with previous data obtained under trial conditions. Therefore, optimization of enfuvirtide plasma exposure could deserve further evaluation as a determinant of therapeutic response in HIV-positive patients.

Does iatrogenic scleroderma due to injection-site reaction to enfuvirtide impair absorption of the drug?

BACKGROUND: Chronic iatrogenic scleroderma is a possible obstacle to the absorption of subcutaneously administered drugs. This study correlated the clinical and histopathological pattern of injection-site reactions (ISRs) to the pharmacokinetics of enfuvirtide in patients with HIV. METHODS: Fourteen patients treated with an enfuvirtide-based antiretroviral regimen for a median of 45 weeks were enrolled and their ISRs were evaluated. Twelve patients with evidence of ISRs underwent cutaneous biopsies using a 4-mm punch. The maximum plasma enfuvirtide concentration (Cmax) and the area under the enfuvirtide concentration-time curve (AUC) were assessed using blood sampling. RESULTS: Four different macroscopic patterns of ISR were identified: A--no evidence of cutaneous lesions; B--transient infiltrative lesions that auto-resolved within 24 hours; C--transient nodular lesions that auto-resolved within 7-15 days; and D--stable lesions after more than 30 days. Histological examination showed three morphological patterns: (1) acute urticaria/vasculitis-like pattern, (2) subacute pattern and (3) chronic scleroderma-like pattern. No differences among patients with the various patterns of ISRs were observed, except for a higher Cmax and AUC in patients with pattern 1. CONCLUSIONS: These results confirm that although iatrogenic scleroderma is not related to impaired enfuvirtide absorption, higher Cmax and AUC values are observed in patients with urticaria/vasculitis-like patterns.

Mechanism-based model of the pharmacokinetics of enfuvirtide, an HIV fusion inhibitor.

We present a model of the pharmacokinetics of enfuvirtide, a potent inhibitor of the fusion of human immunodeficiency virus type 1 (HIV-1) with target cells. We assume that subcutaneously administered enfuvirtide accumulates in the injection region, diffuses locally, and gets absorbed into blood, where it reversibly associates with lipidic cell membranes and is eventually eliminated. We develop mathematical descriptions of each of these processes and predict the time-evolution of the concentration of enfuvirtide in plasma, C(p). We find, interestingly, that diffusion of enfuvirtide in the subcutaneous region is decoupled from absorption, which enables deduction of analytical expressions for C(p) following single dose administration and ordinary differential equations following multiple dose administration and renders our model amenable to data analysis. Model predictions provide excellent fits to observed plasma concentration-time profiles of enfuvirtide following the intravenous and subcutaneous administration of a single dose and without any adjustable parameters capture quantitatively concentration-time profiles following the administration of multiple doses. Our model thus presents a robust description of the pharmacokinetics of enfuvirtide and may be applied in conjunction with models of viral dynamics to assess responses of HIV-1 patients to alternative enfuvirtide-based therapies. Further, our model reveals that key pharmacokinetic characteristics of enfuvirtide, viz., steady state values of peak and trough concentrations and area under the concentration-time curve, vary nearly linearly with dosage over a broad range of dosages and for different dosing regimens, which enables a priori estimation of enfuvirtide exposure levels for different treatment protocols and may serve to establish guidelines for therapy optimization.