Chemical space exploration around indolylarylsulfone scaffold led to a novel class of highly active HIV-1 NNRTIs with spiro structural features.

To thoroughly investigate the uncharted chemical space around the entrance channel of HIV-1 reverse transcriptase (RT) and to improve the physicochemical properties, we introduced different spiro ring structures with high Fsp3 values as linkers at indole-2-carboxamide, attaching to various terminal substituents to enhance the interactions with the entrance channel. All the newly designed and synthesized indolylarylsulfone (IAS) derivatives exhibited moderate to excellent potency against wild-type HIV-1 with EC50 values ranging from 0.0053 to 0.19 μM. Among them, compounds SO-7g (EC50 = 0.0053 μM) and SO-7h (EC50 = 0.009 μM, SI > 21552) were identified as the most two potent compounds, which displayed 30- and 16-fold improvement than nevirapine and zidovudine and comparable potency to efavirenz and etravirine. Moreover, SO-7g maintained the promising activity against a variety of mutant strains, especially for L100I (EC50 = 0.047 μM), K103 N (EC50 = 0.056 μM), and E138K (EC50 = 0.040 μM). Notably, the introduction of spiro rings could effectively reduce the cytotoxicity (CC50) and greatly improve the selectivity index compared to lead compound, exemplified by SO-7h (CC50 > 214.4 μM, SI > 21552) and SO-7a (CC50 > 233.2 μM, SI > 20933). Additionally, the preliminary SARs based on antiviral activity and molecular simulation perspective were analyzed with a detailed description, which could point out the direction for further structural optimization.