Development of novel HEPT analogs featuring significantly improved anti-resistance potency against HIV-1 through chemical space exploration of the tolerant region I.

Our recent great interest in developing 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) analogs for HIV therapy identified a potent non-nucleoside reverse transcriptase inhibitor (NNRTI) 3 (EC50 = 0.01681 µM), but its therapeutic efficacy was limited by its poor anti-resistance potency. This prompted us to search for potential HEPT analogs with broad-spectrum activities, leading to the generation of a series of novel HEPT analogs through exploring the chemical space of the solvent - protein interface. Encouraging improvements in anti-resistance efficacy were observed in some of these analogs, with the most promising compound 7 g being 3 to 26 - fold more potent than 3 against five mutant strains (E138K, Y181C, L100I, K103N, and Y188L). This analog surpassed the activity and selectivity of compound 3 by approximately 2-fold (EC50 = 0.007468 µM, SI = 4260). Furthermore, it was found to demonstrate feeble inhibition of CYP and hERG in vitro, and no in vivo acute toxicity. This study will further enrich the structure-activity relationships (SARs) of the HEPT scaffold, providing new guidance for the development of NNRTIs.

Improving the anti-HIV-1 activity and solubility of poorly water-soluble DAPYs by heteroaromatic replacement strategy: From naphthalene-DAPYs to quinoline-DAPYs.

To enhance the anti-HIV-1 efficacy and solubility of our previously documented NNRTI 1, a collection of innovative quinoline-substituted DAPY derivatives were devised using heteroaromatic replacement strategy. The results of biological evaluation revealed that the representative compound 5h possessed the highest inhibitory activity against wild-type HIV-1 and selectivity index (EC50 = 0.0018 µM, SI > 166667), which were obviously better than that of 1 (EC50 = 0.00978 µM, SI > 37764), NVP (EC50 = 0.059 µM, SI > 158), EFV (EC50 = 0.028 µM, SI > 269), and ETR (EC50 = 0.0029 µM, SI > 1519). The water solubility of compound 5h was remarkably improved, surpassing that of 1, ETR and RPV. Additionally, this compound exerted significantly enhanced anti-resistance potency, compared to 1, and displayed comparable activity to ETR against WT RT of HIV-1 (IC50 = 0.011 µM). To elucidate the underlying molecular mechanisms, molecular docking studies were conducted to investigate the crucial interactions between 5h and WT/mutant strains of HIV-1. These findings provide valuable insights and drive further advancements in the development of DAPYs for HIV therapy.

Structure-guided design of novel HEPT analogs with enhanced potency and safety: From Isopropyl-HEPTs to Cyclopropyl-HEPTs.

Members of the HEPT class are potential non-nucleoside inhibitors of HIV-1 reverse transcriptase. Our previously disclosed one representative HEPT analog 2 produced potent inhibitory activity against wild-type HIV-1 (EC50 = 63.0 nM), but its high cytotoxicity and low selectivity index still needs to be improved (CC50 = 34.0 µM, SI = 565). In this work, a series of novel cyclopropyl-substituted HEPT analogs were developed by substituting a cyclopropyl ring for the isopropyl group at the C-5 position of 2 with the purpose of improving its potency and safety. Of this series, the most potent compound 9h featuring a 2,5-fluoro substitution on the C-6 benzene ring exerted significantly increased inhibitory activity toward wild-type HIV-1 (EC50 = 0.017 µM), which was 4-fold more active than the lead compound 2. The cytotoxicity of 9h was also reduced with much higher selectivity index (SI > 2328). This compound possessed good pharmacokinetics profiles and potential safety: (1) No obvious in vitro inhibition effect toward CYP enzyme and hERG was observed in 9h; (2) The single-dose acute toxicity test did not induce mice death and obvious pathological damage; (3) Excellent oral bioavailability of 9h (F= 86%) in rats was unveiled. These results provide valuable guidance for further development of HEPT anti-HIV-1 drugs.