“Pseudosubstrate Envelope”/Free Energy Perturbation-Guided Design and Mechanistic Investigations of Benzothiazole HIV Capsid Modulators with High Ligand Efficiency

Based on our proposed “pseudosubstrate envelope”
concept, 25 benzothiazole-bearing HIV capsid protein (CA) modulators
were designed and synthesized under the guidance of free energy perturbation
technology. The most potent compound, IC-1k, exhibited
an EC50 of 2.69 nM against HIV-1, being 393 times more
potent than the positive control PF74. Notably, IC-1k emerged as the highest ligand efficiency (LE = 0.32) HIV CA modulator,
surpassing that of the approved drug lenacapavir (LE = 0.21). Surface
plasmon resonance assay and crystallographic analysis confirmed that IC-1k targeted HIV-1 CA within the chemical space of the “pseudosubstrate
envelope”. Further mechanistic studies revealed a dual-stage
inhibition profile: IC-1k disrupted early-stage capsid–host-factor
interactions and promoted late-stage capsid misassembly. Preliminary
pharmacokinetic evaluations demonstrated significantly improved metabolic
stability in human liver microsomes for IC-1k (T1/2 = 91.3 min) compared to PF74 (T1/2 = 0.7 min), alongside a favorable safety profile.
Overall, IC-1k presents a promising lead compound for
further optimization.