Efficacy and Safety of Albuvirtide in HIV – 1 Experienced Adults

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Efficacy and Safety of the Long-Acting Fusion Inhibitor Albuvirtide in Antiretroviral-Experienced Adults with Human Immunodeficiency Virus-1: Interim Analysis of the Randomized, Controlled, Phase 3, Non-Inferiority TALENT Study

Introduction

The global fight against HIV-1 infection has seen significant advancements through antiretroviral therapy (ART), which reduces viral load, delays disease progression, and decreases transmission. However, challenges such as drug resistance, toxicity, and adherence persist, particularly in resource-limited settings. The World Health Organization (WHO) recommends second-line regimens for patients failing first-line therapy, typically combining protease inhibitors (PIs) like ritonavir-boosted lopinavir (LPV/r) with two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). Despite these guidelines, the limited availability of alternative drugs and toxicity concerns, particularly renal impairment linked to tenofovir disoproxil fumarate (TDF), highlight the need for novel therapies.

Albuvirtide (ABT), a novel long-acting HIV-1 fusion inhibitor, offers a promising alternative. Derived from the gp41 N-terminal heptad repeat, ABT disrupts viral entry by inhibiting the formation of the fusion-active six-helix bundle. Unlike enfuvirtide (T20), the only FDA-approved fusion inhibitor requiring twice-daily injections, ABT’s conjugation with serum albumin extends its half-life to 10–12 days, enabling once-weekly dosing. Preclinical and early clinical studies demonstrated ABT’s potent antiviral activity, broad resistance barrier, and favorable safety profile. This interim analysis of the phase 3 TALENT trial evaluates ABT’s non-inferiority to WHO-recommended second-line regimens in treatment-experienced adults.

Study Design and Methods

The TALENT study is a multicenter, randomized, open-label, non-inferiority trial conducted across 12 sites in China. Eligible participants were adults aged 16–60 years with HIV-1 RNA >1,000 copies/mL after ≥6 months of first-line ART (two NRTIs + one non-NRTI). Exclusion criteria included prior exposure to PIs or fusion inhibitors, active hepatitis, and severe comorbidities.

Patients were randomized 1:1 to receive either:

  1. ABT + LPV/r: Weekly intravenous ABT (320 mg) plus twice-daily LPV/r (400/100 mg).
  2. NRTI + LPV/r: Optimized NRTIs (TDF/3TC, AZT/3TC, or ABC/3TC) selected based on prior resistance, plus LPV/r.

The primary endpoint was the proportion of patients achieving HIV-1 RNA <50 copies/mL at week 48. Non-inferiority was predefined with a margin of 12%. Secondary endpoints included viral suppression <400 copies/mL, CD4+ T-cell recovery, safety, and resistance development. Viral load, CD4 counts, and genotypic resistance were assessed centrally. Statistical analyses followed modified intention-to-treat (mITT) and per-protocol principles, with missing data imputed as failure.

Results

Patient Characteristics

By December 2015, 347 participants were enrolled. At interim analysis, 208 had completed 24 weeks, with 175 (83 ABT, 92 NRTI) included in efficacy analyses after excluding one site for protocol violations. Baseline demographics were balanced: median age ~40 years, 73% male, median CD4+ count ~235 cells/µL, and median viral load ~3.8 log10 copies/mL. Most harbored subtype B (50.9%) or CRF01_AE (29.6%) viruses. Over 80% had resistance mutations to first-line NRTIs/NNRTIs, while PI resistance was rare (<1.2%).

Efficacy Outcomes

At week 48, the ABT group demonstrated superior virological suppression:

  • Primary endpoint (HIV-1 RNA <50 copies/mL): 80.4% (37/46) in ABT vs. 66.0% (33/50) in NRTI (difference: +14.4%, 95% CI: -3.0–31.9), meeting non-inferiority. Per-protocol analysis reinforced superiority (94.9% vs. 74.4%, P = 0.01).
  • Secondary endpoints: Viral suppression <400 copies/mL was 84.8% (ABT) vs. 74.0% (NRTI). Mean HIV-1 RNA decline was greater with ABT (-2.27 vs. -1.77 log10 copies/mL, P = 0.015). CD4+ recovery was comparable (+120.5 vs. +150.3 cells/µL, P = 0.557).

At week 24, both groups showed similar suppression rates (79.5% vs. 78.3%), but ABT’s advantage emerged by week 48, suggesting durable efficacy.

Resistance and Safety

Resistance mutations were analyzed in patients with viral load >400 copies/mL (5 ABT, 13 NRTI). No gp41 mutations emerged in the ABT group, confirming its high genetic barrier. In contrast, NRTI recipients developed new NRTI (M184V, M41LM, K70KR) and PI (I50V, V82A) mutations.

Safety profiles were comparable:

  • Grade 3–4 adverse events: 14.0% (ABT) vs. 11.1% (NRTI).
  • Common events: Diarrhea (8.6% vs. 14.1%), upper respiratory infections (4.3% vs. 6.1%), hypertriglyceridemia (6.5% vs. 4.0%).
  • Renal function: NRTI recipients receiving TDF showed significant eGFR decline at week 12 (-11.48 vs. -1.22 mL/min/1.73 m², P = 0.02).
  • Serious adverse events: 6.5% (ABT) vs. 3.0% (NRTI), none attributed to ABT.

No deaths or treatment-related discontinuations occurred in the ABT group.

Discussion

This interim analysis demonstrates that once-weekly ABT combined with LPV/r is non-inferior—and potentially superior—to standard NRTI-based second-line regimens. ABT’s virological efficacy, coupled with its favorable safety and renal preservation, addresses critical gaps in HIV management.

The high resistance barrier of ABT is particularly noteworthy. Unlike T20, which frequently selects for gp41 mutations, no envelope mutations arose in ABT-treated patients, aligning with its mechanism of targeting the conserved gp41 hydrophobic pocket. This contrasts sharply with NRTI regimens, where emergent resistance compromises long-term efficacy.

ABT’s pharmacokinetic profile also offers practical advantages. Its prolonged half-life enables weekly dosing, simplifying regimens and improving adherence—a key factor in resource-limited settings. Furthermore, avoiding NRTIs mitigates mitochondrial toxicity, bone marrow suppression, and renal dysfunction, as evidenced by preserved eGFR in ABT recipients.

The TALENT study underscores the potential of long-acting agents to transform HIV care. While integrase inhibitors dominate current guidelines, their high cost and emerging resistance underscore the need for alternatives. ABT’s injectable format could benefit patients with poor oral adherence or salvage therapy needs.

Limitations and Future Directions

This interim analysis has limitations. Only 46% of participants completed week 48, and longer follow-up is needed to confirm durability. Additionally, the open-label design introduces potential bias, though central laboratory blinding mitigates this. Future studies should explore ABT in diverse populations, including ART-naïve patients and those with advanced disease.

Conclusion

The TALENT trial represents a milestone in HIV therapeutics as the first phase 3 study of a long-acting fusion inhibitor. ABT, administered weekly with LPV/r, demonstrates potent efficacy, safety, and tolerability in treatment-experienced adults. Its non-inferiority to WHO-recommended regimens, combined with a simplified dosing schedule and reduced toxicity, positions ABT as a valuable addition to global HIV treatment strategies.

doi.org/10.1097/CM9.0000000000001273

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