Design, Synthesis And Evaluation Of Novel Non-peptide Small Molecule HIV Fusion Inhibitors Targeting HIV-1 Gp41

AIDS has become one of the most serious diseases that threaten human health and life. Although current anti-HIV drugs can prevent AIDS disease from further developing, there are some problems such as rapid emergence of virus-drug resistance, high toxicity and expensive price in clinical use. HIV-1 envelope glycoprotein gp41 is one of the most important targets to inhibit HIV infecting T-cells because it plays a crucial role in mediating virus fusion and entry into host cells. The inhibitors targeting gp41 can effectually inhibit HIV replication and also prevent viral infection. The first HIV fusion inhibitor drug T-20 is targeting HIV-1 gp41, but its peptide structure causes two critical limitations: lack of oral availability and high cost of production. Therefore, to explore small molecules targeting gp41 as novel potent HIV fusion inhibitors is really necessary.Base on the small molecule binding site of HIV-1 gp41, series of N-aryl-2,5-dimethyl pyrrole derivatives and 2-halogen-5-(5-methylfuran-2-yl)benzoic acid derivatives were designed and synthesized by using medicinal chemistry principles and methods. Then under the guides of bioassay and molecular modeling, the modification strategy of prolonging the molecular scaffold was applied in our project to design and synthesize series of linear molecules with three or four aryl-ring compounds, in order to discover new lead compounds with novel scaffolds and especially targeting HIV-1 gp41.29 new compounds have been designed and synthesized and 25 of them were assayed in MT-2 cell line to evaluate their anti-HIV activities. The result indicated that 8 compounds exhibited potent anti-HIV activity. The most promising compound 61 and 62 with a four-ring scaffold showed EC50 values of 0.17μM and 0.19μM and TI values of 46.29 and 46.15 respectively. Compound 63 and 25 also exhibited potent activities with EC50 values of 0.53μMå’Œ0.43μM respectively. Additionally, compound 10,11,16, and 24 are active with a EC50 value range of 63.18μM,30.15μM,3.86μM and 19.58μM. However, all of above active compound showed high cytotoxicity, resulting in their TI values lower. Compound 25 has a methoxy and a chloride on the benzene ring instead of m-carboxyl in most other designed target compounds and also showed very potent activity (EC₅₀=0.43μM). This result suggested that the m-carboxylphenyl moiety in active compounds could be modifiable and worth to do further researches about substituents on the benzene ring to enhance inhibitory activity and decrease molecular cytotoxicity.So far, some new preliminary SAR results are summarized as below: (1) The length of molecule is crucial to enhance anti-HIV activity because of increased combine joints and complementarity between inhibitors and key amino acids on the binding site.(2) Carboxyl or other electronegative groups in the two ends of inhibitors is necessary to form "salt bridge" with the amino acids Lys⁺574 and ARG⁺579. But too strong polarity of small molecules inhibited them to penetrate the cell membrane.(3) The carboxyphenyl moiety will be modifiable to increase molecular activity and decrease cytotoxity. More substituents on the different positions of the benzene ring should be further explored to understand more SAR for this kind of compounds.(4) The cavity of gp41 for small molecule inhibitors is a special shape and requires a conformation steady. Current linear four-ring scaffold would be matched the cavity well and compounds 61 and 62 could serve as new leads for further structure modification and optimization.In conclusion, the design, synthesis and evaluation of 29 new compounds based on hits NB-2 and NB-64 have provided some new structure-activity relationships, discovered new active compounds with a novel four-ring scaffold. Current study results will help us further studies to look for new non-peptide small molecule HIV fusion inhibitor as better lead compounds.