Jain Chung

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.

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.

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.

Prognostic Staging of Extensively Pretreated Patients with Advanced HIV-1 Disease

Abstract Purpose: Determinants of therapeutic success are poorly characterized in patients with extensive HAART experience. Positive prognostic factors (PPFs) in the TORO trials could serve as the basis for a prognostically meaningful staging of treatment-experienced patients initiating a new antiretroviral regimen. Method: In TORO, triple-class-experienced patients with viral load (VL) ≥5,000 copies/mL received an optimized background regimen of 3-5 antiretrovirals (based on treatment history and baseline resistance testing) ± enfuvirtide (n = 995). Clinically relevant baseline PPFs that were predictive of 48-week virologic outcomes were identified via multiple regression analyses. Results: The likelihood of VL <400 copies/mL at 48 weeks (ITT analysis) was greater for those patients who had baseline CD4 count ≥100 cells/mm3 (odds ratio [OR] 2.1; 95% confidence intervals [CIs] 1.5, 3.1); baseline VL <5 log10 copies/mL (OR 1.8; 95% CIs 1.2, 2.6); received ≤10 prior antiretrovirals (OR 2.4; 95% CIs 1.6, 3.4); or received ≥2 active antiretrovirals in their background treatment regimen (OR 2.3; 95% CIs 1.6, 3.3). Overall, 67% of triple-class-experienced patients who met all four prognostic criteria and received enfuvirtide achieved VL <400 copies/mL at 48 weeks vs. 43% for non-enfuvirtide patients (p < .05). Similar results were obtained when the analysis was done separately in each of the randomization arms of the study. Conclusion: Our findings provide guidance for physicians on expected outcomes in treatment-experienced patients and should be of value in their clinical management, as well as in stratifying participants in clinical trials involving treatment-experienced patients.

The effects of enfuvirtide therapy on body composition and metabolic parameters over 48 weeks in the TORO body imaging substudy

The aim of the study was to compare the metabolic and morphological effects of enfuvirtide plus an optimized background (OB) regimen vs. OB alone (control group) in treatment‐experienced patients in the T‐20 vs. Optimized Regimen Only (TORO) studies.

Efficacy and Safety of 48 Weeks of Enfuvirtide 180 mg Once-Daily Dosing Versus 90 mg Twice-Daily Dosing in HIV-Infected Patients

Abstract 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.