Miklos Salgo

Enfuvirtide: the first therapy to inhibit the entry of HIV-1 into host CD4 lymphocytes

Highly active antiretroviral therapy (HAART) based on combinations of drugs that target key enzymes in the life-cycle of human immunodeficiency virus (HIV) has considerably reduced morbidity and mortality from HIV infection since its introduction in the mid-1990s. However, the growing problem of the emergence of HIV strains that are resistant not only to individual drugs, but to whole drug classes, means that agents with new mechanisms of action are needed. Here, we describe the discovery and development of enfuvirtide (Fuzeon), the first drug to inhibit the entry of HIV-1 into host cells.

Ritonavir and saquinavir combination therapy for the treatment of HIV infection.

OBJECTIVE To evaluate the safety and antiretroviral activity of ritonavir (Norvir) and saquinavir (Invirase) combination therapy in patients with HIV infection. DESIGN A multicenter, randomized, open-label clinical trial. SETTING Seven HIV research units in the USA and Canada. PATIENTS A group of 141 adults with HIV infection, CD4 T lymphocyte counts of 100-500 x 10(6) cells/l, whether treated previously or not with reverse transcriptase inhibitor therapy, but without previous HIV protease inhibitor drug therapy. INTERVENTIONS After discontinuation of prior therapy for 2 weeks, group I patients were randomized to receive either combination (A) ritonavir 400 mg and saquinavir 400 mg twice daily or (B) ritonavir 600 mg and saquinavir 400 mg twice daily. After an initial safety assessment of group I patients, group II patients were randomized to receive either (C) ritonavir 400 mg and saquinavir 400 mg three times daily or (D) ritonavir 600 mg and saquinavir 600 mg twice daily. Investigators were allowed to add up to two reverse transcriptase inhibitors (including at least one with which the patient had not been previously treated) to a patients regimen after week 12 for failure to achieve or maintain an HIV RNA level < or = 200 copies/ml documented on two consecutive occasions. MEASUREMENTS Plasma HIV RNA levels and CD4+ T-lymphocyte counts were measured at baseline, every 2 weeks for 2 months, and monthly thereafter. Safety was assessed through the reporting of adverse events, physical examinations, and the monitoring of routine laboratory tests. RESULTS The 48 weeks of study treatment was completed by 75% (106/141) of the patients. Over 80% of the patients on treatment at week 48 had an HIV RNA level < or = 200 copies/ml. In addition, intent-to-treat and on-treatment analyses revealed comparable results. Suppression of plasma HIV RNA levels was similar for all treatment arms (mean areas under the curve minus baseline through 48 weeks were-1.9, -2.0, -1.6, -1.8 log10 copies/ml in ritonavir-saquinavir 400-400 mg twice daily, 600-400 mg twice daily, 400-400 mg three times daily, and 600-600 mg twice daily, respectively). Median CD4 T-lymphocyte count rose by 128 x 10(6) cells/l from baseline, with an interquartile range (IQR) of 82-221 x 10(6) cells/l. The most common adverse events were diarrhea, circumoral paresthesia, asthenia, and nausea. Reversible elevation of serum transaminases (> 5 x upper limit of normal) occurred in 10% (14/141) of the patients enrolled in this study and was associated with baseline abnormalities in liver function tests, baseline hepatitis B surface antigen positivity, or hepatitis C antibody positivity (relative risk, 5.0; 95% confidence interval 1.5-16.9). Most moderate or severe elevations in liver function tests occurred in patients treated with ritonavir-saquinavir 600-600 mg twice daily. CONCLUSIONS Ritonavir 400 mg combined with saquinavir 400 mg twice daily with the selective addition of reverse transcriptase inhibitors was the best-tolerated regimen of four dose-ranging regimens and was equally as active as the higher dose combinations in HIV-positive patients without previous protease inhibitor treatment.

Durable efficacy of enfuvirtide over 48 weeks in heavily treatment-experienced HIV-1-infected patients in the T-20 versus optimized background regimen only 1 and 2 clinical trials.

Background:The T-20 Versus Optimized Background Regimen Only (TORO) 1 and TORO 2 clinical trials are open-label, controlled, parallel-group, phase 3 studies comparing enfuvirtide plus an optimized background (OB) of antiretrovirals (n = 661) with OB alone (n = 334) in treatment-experienced HIV-1-infected patients. Methods:The primary objective at week 48 was to investigate durability of efficacy, as measured by the percentage of patients maintaining their week 24 response or improving. Efficacy analyses used the intent-to-treat population. Results:A total of 73.7% of patients randomized to the enfuvirtide group remained on treatment through week 48 versus 21.3% originally randomized to the control group. At week 48, a higher proportion of week 24 responders maintained their response or were new responders in the enfuvirtide group than in the control group in each responder category: HIV-1 RNA level ≥1.0 log10 change from baseline, <400 copies/mL and <50 copies/mL (37.4%, 30.4%, and 18.3% in the enfuvirtide group vs. 17.1%, 12.0%, and 7.8% in the control group, respectively; P < 0.0001 for all comparisons). CD4 cell count increases from baseline were twice as great in the enfuvirtide group as in the control group. Conclusion:These data demonstrate durable efficacy of enfuvirtide plus OB over 48 weeks.

Characterization of determinants of genotypic and phenotypic resistance to enfuvirtide in baseline and on- treatment HIV-1 isolates

Background: Enfuvirtide (ENF) is the first of a novel class of drugs that block HIV gp41-mediated viral fusion to host cells. Viruses with mutations at positions 36–38 in HIV-1 gp41 and/or reduced susceptibility to ENF have been selected both in vitro and in vivo. Methods: An analysis of baseline and on-treatment ENF susceptibility in virus samples from Phase II clinical trial patients treated with ENF as functional monotherapy for 28 days (TRI-003) or in combination with oral antiretrovirals for ⩾ 48 weeks (T20–205, T20–206 and T20–208). Population sequencing identified amino acid (aa) substitutions at positions 36–45 of gp41 in plasma HIV-1. ENF susceptibility of virus isolates was tested in the cMAGI assay and viral DNA was sequenced for selected isolates. Results: HIV-1 gp41 aa 36–45 were highly conserved in virus from ENF-naive patients, except for a 15% incidence of N42S which did not reduce sensitivity to ENF. Virus from patients experiencing viral load rebound exhibited reduced susceptibility to ENF and substitutions in gp41 aa 36–45. The most common substitutions observed on treatment were at positions 36, 38, 40, 42 and 43. On-treatment changes in the phenotypic susceptibility of virus isolates to ENF were generally associated with genotypic changes in aa 36–45. There was a relatively lower incidence of ENF resistance in patients with baseline sensitivity to more oral antiretrovirals in comparison to patients sensitive to fewer antiretrovirals. Conclusions: These data identify the importance of HIV-1 gp41 aa 36–45 in the emergence of resistance to ENF.

Zalcitabine Compared with Zidovudine in Patients with Advanced HIV-1 Infection Who Received Previous Zidovudine Therapy

Zidovudine (3-azido-3-deoxythymidine [AZT]) prolongs survival and decreases the frequency of and time to development of the acquired immunodeficiency syndrome (AIDS) [1-3]. Anemia and neutropenia are the most common serious toxicities associated with zidovudine therapy and may limit treatment in some patients with advanced disease [2-4]. In patients with advanced human immunodeficiency virus type 1 (HIV) infection, long-term treatment with zidovudine is associated with a progressive decline in CD4 lymphocyte counts, disease progression, increasing fatality, and emergence of virus isolates with reduced in vitro susceptibility to zidovudine [1, 5-7]. Therefore, alternative treatments for patients with progressive HIV disease are needed. Zalcitabine (dideoxycytidine [ddC]) is another deoxynucleoside analog that inhibits the in vitro replication of HIV [8] and improves certain measures of HIV infection, including the CD4 lymphocyte count and the p24 antigen level [9, 10]. In addition, zidovudine-resistant isolates are susceptible to zalcitabine in vitro [11]. The major toxicity associated with zalcitabine differs from that seen with zidovudine and includes a dose-limiting peripheral neuropathy [9, 10]. These observations prompted us to study the safety and efficacy of zalcitabine among patients with advanced HIV disease who had received previous zidovudine therapy for 48 weeks or more. Figure 1. Estimated distributions of the time to the first critical event, including AIDS-defining opportunistic infection, malignancy, or death. Methods Patients The study sample consisted of patients who had tolerated 48 weeks or more of zidovudine therapy (total daily dose 500 mg) and who had a first episode of Pneumocystis carinii pneumonia or advanced AIDS-related complex at the time of initiation of zidovudine therapy. All patients had to be receiving and tolerating zidovudine at the time of enrollment in the study. Advanced AIDS-related complex was defined by the presence of oral candidiasis, oral hairy leukoplakia, herpes varicella infection, unintentional weight loss exceeding 10% of body weight or 4.5 kg (10 lb), unexplained diarrhea (defined as two or more liquid stools per day persisting for 30 days or more) or unexplained fever (defined as a temperature greater than 38.5 C occurring for more than 14 consecutive days or for more than 15 days in a 30-day period), and a CD4-lymphocyte count of less than 200 cells/mm3. The criteria for eligibility also included a hemoglobin concentration of 95 g/L or more, a total granulocyte count of 0.750 109/L or more, a platelet count of 75 109/L or more, serum transaminase levels no higher than five times the upper limit of normal, a Karnofsky performance score of 60 or more, and seropositivity for HIV antibody as determined by any licensed enzyme-linked immunosorbent assay. At least 20% of the patients were also required to have a serum HIV p24 antigen level of 70 pg/mL or more. Patients were also excluded from the study for the following reasons: interruption of previous zidovudine therapy for more than 30 consecutive days or a total of 90 days, development of a serious toxicity during zidovudine therapy, previous zalcitabine therapy, the presence of visceral or symptomatic Kaposi sarcoma requiring therapy, the presence of peripheral neuropathy, or pregnancy. All patients received inhaled pentamidine isethionate, 300 mg every 4 weeks, for the prevention of P. carinii pneumonia. Maintenance therapy for other AIDS-related opportunistic infections was allowed. The use of other antiretroviral drugs, biologic-response modifiers, systemic corticosteroids, drugs that could cause peripheral neuropathy other than isoniazid, and experimental drugs was not allowed. The patients were recruited from four AIDS Clinical Trials Units, five university-affiliated medical centers, and private practice groups. The study was approved by institutional review boards at each center, and all patients gave written informed consent. Study Design and Treatment Regimen The study was an open-label, randomized trial. Patients were stratified according to a diagnosis of AIDS or advanced AIDS-related complex at the time of initiation of zidovudine therapy and according to the dose of zidovudine that they were receiving at study entry. The intended sample size was 160 patients per treatment arm, the number required to detect a 15% difference in survival outcome with a power of 80% and a two-sided significance level of 0.05. After the enrollment of only 115 patients, the study was closed to enrollment in July 1991 because of slow accrual. A blocked randomization procedure was used to assign patients in each center to zalcitabine or zidovudine. Zalcitabine (Hivid, Hoffmann-La Roche, Nutley, New Jersey) was given in two 0.375-mg tablets every 8 hours. Zidovudine (Retrovir, Burroughs Wellcome, Inc., Research Triangle Park, North Carolina) was initially given in two 100-mg capsules every 4 to 5 hours and then in one 100-mg capsule every 4 to 5 hours. Management of Toxicity If a serious toxicity occurred, therapy with the study medication was interrupted. After abnormal values returned to levels indicating a lower-grade toxicity or to pretreatment values, therapy with the study medication was restarted at half the dose. If severe anemia developed, red-cell transfusions or therapy with recombinant erythropoietin was administered. If patients had a toxicity that was persistent, recurred after reduction of study medication, or was life threatening, their study medication was permanently withdrawn. Zalcitabine therapy was permanently discontinued in patients who developed severe treatment-related peripheral neuropathy. Severe peripheral neuropathy was defined as moderate discomfort associated with the loss of a deep tendon reflex, the presence of paresthesias, or pain that either was refractory to non-narcotic analgesics, amitriptyline, or clonazepam or worsened during a 1-week period. Evaluation of Patients The pretreatment evaluation included a medical history, a physical examination, a signs-and-symptoms questionnaire, an evaluation for peripheral neuropathy, a Karnofsky performance score, and laboratory studies. Lymphocyte phenotyping was done by flow cytometry at the same laboratory at each center on peripheral blood mononuclear cells prepared on a Ficoll-Hypaque gradient or by the whole-blood lysis method with monoclonal reagents. The serum specimens collected for HIV p24 antigen determinations were frozen for batch testing with a commercial test kit (Abbott, North Chicago, Illinois). All patients were re-evaluated every 2 weeks for the first 12 weeks and every 4 weeks thereafter. Patients who discontinued therapy with the study medication were followed for survival only. Clinical measures of efficacy were survival and time to a first critical event, which was defined as any AIDS-related condition or death. Secondary measures of efficacy were increases in CD4 lymphocyte counts, reduction of serum p24 antigen levels, weight gain, and changes in Karnofsky performance scores. Statistical Analysis Differences in proportions were assessed using the Fisher exact test. Time-to-event distributions were estimated using the method of Kaplan and Meier and compared using the Cox proportional-hazards regression model. To assess changes in the CD4 lymphocyte count, the serum p24 antigen level, weight, and Karnofsky performance score, parametric analyses of covariance were used. Subgroup analyses were carried out, with patients stratified according to diagnosis (AIDS or AIDS-related complex) and pretreatment CD4 lymphocyte count ( 100 cells/mm3 or >100 cells/mm3). All analyses were based on an intent-to-treat approach, using clinical data available through 15 June 1991 and survival data collected through 31 December 1991. The hazard ratio expressed as relative risk and 95% two-sided CIs are given when appropriate. All P values were two sided. Results Patient Sample Between January 1990 and June 1991, 111 patients were enrolled in the study. Patients included 110 men and 1 woman (mean age, 36 years). Most patients were white and non-Hispanic. One hundred six patients were homosexual or bisexual, 7 had a history of intravenous drug use, 12 had a history of receipt of blood products, and 8 had heterosexual contact with a person at risk for HIV infection. Twenty-two patients had AIDS and 89 had AIDS-related complex at the time zidovudine therapy was first instituted. Fifty-nine patients were randomly assigned to receive zalcitabine and 52 to receive zidovudine. No significant differences were noted between the two treatment groups regarding pretreatment characteristics (Table 1). The median duration of study treatment was 279 days (range, 16 to 437 days) for the zalcitabine group and 174.5 days (range, 8 to 400 days) for the zidovudine group. The time to discontinuation of study medication was statistically shorter in the zidovudine group compared with the zalcitabine group (P = 0.001). Table 1. Patient Characteristics by Treatment Group* Of the 111 patients enrolled, 56 were withdrawn from the study medication, 20 completed the study, and 35 were still receiving study medication when the database was closed for analysis on 15 June 1991. The reasons for discontinuation of study medication included treatment with nonallowed medications (5 patients in the zidovudine group); death (2 patients in the zalcitabine group and 1 patient in the zidovudine group); toxicity (12 patients in the zalcitabine group and 5 in the zidovudine group); self-withdrawal (6 patients in the zalcitabine group and 18 in the zidovudine group); loss to follow-up (2 patients in the zalcitabine group and 3 in the zidovudine group); and administrative reasons (2 patients in the zidovudine group). Significantly more patients were withdrawn from the zidovudine group than from the zalcitabine group (34 patients compared with 22 patients; P = 0.004). For patients who complet

Human immunodeficiency virus type 1 RNA level and CD4 count as prognostic markers and surrogate end points: A meta-analysis

Objective: To evaluate treatment-mediated changes in HIV-1 RNA and CD3 count as prognostic markers and surrogate end points for disease progression (AIDS/death). Methods: Data from 13,045 subjects in all 16 randomized trials comparing nucleoside analogue reverse transcriptase inhibitors and having HIV-1 RNA measurements at 24 weeks were obtained. A total of 3146 subjects had HIV-1 RNA and CD3 count determinations at 24 weeks after starting treatment. Results: At Week 24, the percentage of subjects experiencing an HIV-1 RNA decrease of >1 log(10) copies/ml or a CD4 count increase of >33% was similar (22% vs 25%). Changes in both markers at Week 24 mere significant independent predictors of AIDS/death: across trials, the average reduction in hazard was 51% per 1 log(10) HIV-1 RNA copies/ml decrease (95% confidence interval: 41%, 59%) and 20% per 33% CD4 count increase (17%, 24%). In univariate analyses, the hazard ratio for AIDS/death in randomized treatment comparisons was significantly associated with differences between treatments in mean area under the curve of HIV-1 RNA changes to Weeks 8 and 24 (AUCMB) and mean CD3 change at Week 24, but, in multivariate analysis, only mean CD4 change was significant. Conclusions: Change in HIV-1 RNA, particularly using AUCMB, and in CD4 count should be measured to aid patient management and evaluation of treatment activity in clinical trials. However, short-term changes in these markers are imperfect as surrogate end points for long-term clinical outcome because two randomized treatment comparisons may show similar differences between treatments in marker changes but not similar differences in progression to AIDS/death.

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.

The Copper Intrauterine Device and Its Mode of Action

Copper bearing intrauterine devices have become the most reputable effective and safe IUDs available. The reaction between the copper and the body prevents fertilization. An infiltration of polymorphonuclear leukocytes occur in the uterine lumen as a result of the IUD. The daily released copper is equivalent to 1% of the copper taken orally by day. Alpha amylase activity is depressed; cyclic increase in glycogen synthetase is eliminated. Copper can inhibit enzyme activity even if cupric ions from the metal are at a low concentration. The effect of copper on the myometrium accounts for the lower initial expulsion rates for copper bearing devices. The uterus loses its ability to contract after prolonged exposure to copper. The chemical breakdown between cuprous oxide and saline produces a cuprous complex which yields cupric ion and free radicals. The inhibition of the implantation process of the copper may lead to an explanation. Metallic copper liquifies endometrial mucoids. Cupric ions increase the biosynthesis of certain prostaglandins. Prostaglandins may be another explanation of implantation inhibition. Further research on implantation is needed.

Guillain-Barré Syndrome Associated with Immune Reconstitution

We report a case of acute Guillain-Barré syndrome (GBS) associated with a prompt and vigorous immune reconstitution and decrease in the virus load noted during treatment with a potent regimen of highly active antiretroviral therapy. We hypothesize that GBS may have been due to an aberrant immune response or an adverse drug reaction in association with preexisting peripheral neurologic disease.

Pharmacokinetics, Pharmacodynamics and Drug Interaction Potential of Enfuvirtide

AbstractEnfuvirtide, 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 90mg 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 (5.48L), 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 45–180mg.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 90mg twice daily.