THURSDAY, March 18, 2021 (HealthDay News) — Infusion of a broadly neutralizing antibody (bnAb) does not prevent overall HIV-1 acquisition more effectively than placebo, according to a study of two trials published in the March 18 issue of the New England Journal of Medicine.

Lawrence Corey, M.D., from the Fred Hutchinson Cancer Research Center in Seattle, and colleagues randomly assigned 2,699 at-risk cisgender men and transgender persons in the Americas and Europe in the HVTN 704/HPTN 085 trial and 1,924 at-risk women in sub-Saharan Africa in the HVTN 703/HPTN 081 trial to receive either infusions of a bnAb (VRC01; low dose [10 mg/kg] or high dose [30 mg/kg]) or placebo for 10 infusions.

The researchers found that within each trial, adverse events were similar in number and severity among the treatment groups. In the HVTN 704/HPTN 085 trial, the incidence of HIV-1 infection was 2.35 and 2.98 per 100 person-years in the pooled VRC01 groups and the placebo group, respectively (estimated prevention efficacy, 26.6 percent; 95 percent confidence interval, −11.7 to 51.8; P = 0.15); in the HVTN 703/HPTN 081 group, the corresponding incidences were 2.49 and 3.10 (estimated prevention efficacy, 8.8 percent; 95 percent confidence interval, −45.1 to 42.6; P = 0.70). In prespecified analyses pooling data across trials, the incidence of infection with VRC01-sensitive isolates was 0.20 and 0.86 per 100 person-years among VRC01 and placebo recipients, respectively (estimated prevention efficacy, 75.4 percent; 95 percent confidence interval, 45.5 to 88.9).

“Passive immunization with VRC01 indeed protected against acquisition of HIV-1, but only against viruses that were highly sensitive to the antibody. And even for these sensitive viruses, the protection was not absolute,” write the authors of an accompanying editorial.

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