Structural basis of lenacapavir-induced HIV-1 capsid defects during virion maturation.

Long-acting lenacapavir (LEN) has emerged as a highly effective, potentially game-changing therapy for HIV treatment and prevention. Its mechanism of action in the early phase of HIV-1 replication, when the capsid directs key post-entry steps such as reverse transcription, nuclear import, and integration, has been well characterized. In contrast, its effects during the late phase of replication, when the capsid assembles and matures within budding virions, remain poorly understood. Here, we determine the cryo-electron microscopy structure of the mature HIV-1 capsid lattice assembled within virus-like particles in the presence of LEN. Our structural analyses reveal that LEN alters interhexamer interactions, perturbs the capsid lattice curvature, and thereby prevents the formation of a functional cone-shaped capsid. Biochemical analyses further demonstrate that LEN-containing cores lose reverse transcriptase because of compromised capsid integrity, whereas integrase and viral RNA remain associated. Functionally, viruses produced in the presence of LEN exhibit markedly reduced infectivity, low reverse transcription activity, and poor integration. Taken together, these findings provide mechanistic insights into the late-phase action of LEN and provide key directions for the design of future inhibitors.