Prophylactic treatment with broadly neutralizing antibody VRC01 selects for escape mutants after infection in Antibody-Mediated Prevention trials.

Broadly neutralizing antibodies (bnAbs) show promise in HIV prevention, yet viral escape remains a challenge. In the Antibody-Mediated Prevention (AMP) trials, the CD4 binding site (CD4bs) bnAb VRC01 blocked acquisition by VRC01-sensitive strains. However, its influence on viral evolution post acquisition is not fully understood. Here we analysed 11,730 HIV envelope sequences generated during the AMP trials from 47 participants, identifying VRC01-mediated de novo escape mutations in 8 of 26 VRC01-treated participants but none in 21 placebo participants. These mutations were found at very low frequencies (<1%) in globally circulating viruses, suggesting that they may confer fitness costs. Escape mutations, primarily located in the Loop-D and β23/V5 regions of Env, conferred cross-resistance to several CD4bs bnAbs; however, more potent CD4bs bnAbs such as N6 and 1-18 largely retained their activity. Our findings demonstrate that prophylactic VRC01 can select for viral escape after infection, underscoring the need for next-generation bnAbs with improved breadth and potency to enhance durability and efficacy of antibody-based HIV prevention.