Various bnAb combinations and bispecific Abs , enabling consecutive targeting of different epitopes , are in clinical development for HIV-1 prevention 16,17 . Predicted potency - breadth curves have suggested that a triple combination consisting of one CD4bs - targeting bnAb , one V2 glycan - targeting bnAb and one V3 glycan - targeting bnAb would have the best neutralization coverage against a panel of clade C viruses 7 . One such combination , VRC07 - 523LS ( CD4bs ) , PGT121 ( V3 glycan ) and PGDM1400 ( V2 glycan ) , has been predicted to have 99 % neutralization breadth ( IC 80 < 10 μg ml -1 ) and a geometric mean IC 80 of 0.09 μg ml -1 against a diverse panel of viruses , compared with 76 % neutralization breadth and a geometric mean IC 80 of 2.64 μg ml -1 for VRC01 alone 17 . ( LS refers to a Fc - modified version to extend half - life . ) This specific triple - bnAb combination is in development for potential efficacy testing and has been safely administered to adults without HIV in a recent phase 1 study 18 . We therefore decided to apply PT 80 to predict PE of 20 or 40 mg kg -1 each of PGT121.414.LS , PGDM1400LS and VRC07 - 523LS delivered together IV . Using available serum concentration data 18,19 , steady - state serum concentrations of each bnAb over 16 weeks were simulated based on popPK modeling ( Methods ) . Because data from the LS forms of PGT121 and PGDM1400 are not yet available , the predictions considered a possible increase of 2.5 - fold in elimination half - life conferred by the LS mutation , with 2.5 - fold being a conservative assumption based on the previously reported fourfold increase 20 . Our results suggest that PT 80 > 200 of a bnAb regimen to a given exposing virus would provide 90 % or higher efficacy to block HIV-1 acquisition with that virus . We applied this threshold ( PT 80 > 200 ) in our definition of neutralization coverage . Neutralization coverage by at least one bnAb in the regimen , averaged over time for a 16 - weekly regimen , and to the 47 viruses ( all subtype C ) acquired by 29 placebo recipients from 703/081 was 71 % ; neutralization coverage averaged over time and to the 70 viruses ( 90 % subtype B ) acquired by 35 placebo recipients from 704/085 was 73 % ( Fig . 6a , b ) . In contrast , neutralization coverage of VRC01 ( at 30 mg kg -1 ) averaged over time and to the 703/081 or 704/085 viruses was 8 % .