Target-based Design, Synthesis And Activity Evaluation Of Novel Heterocyclic Derivatives As Potent HIV-1Inhibitors

Acquired immune deficiency syndrome (AIDS) which is mainly caused by human immunodeficiency virus type-1(HIV-1), remains to be one of the most leading pandemic disease worldwide.The HIV-1non-nucleoside reverse transcriptase inhibitors (NNRTIs) is a class of specific HIV-1reverse transcriptase (RT) inhibitiors which have diversed chemical structures but share some inherent similarities in their pharmacophoric elements and binding mode with the NNRTI binding pocket (NNIBP), providing valuable information for the lead discovery and drug optimization. Up to now, five NNRTIs have been approved for clinical application by FDA:nevirapine (NVP), delavirdine (DLV), efavirenz (EFV), etravirine (ETV) and rilpivrine (RPV).The HIV-1NNRTIs are the major components of highly active antiretroviral therapy (HAART) regimen, but a major problem is that the long-term efficacy of NNRTIs is limited by the rapid emergence of drug-resistant HIV-1strains. Thus, the discovery of novel NNRTIs chemical entities with improved drug resistance profiles has been a very active research field in recent years.HIV-1integrase (IN) enables HIV genetic material to be integrated into the host DNA in the infected cell. Integrase catalyzes two reactions:1)3’-processing, in which two or three nucleotides are removed from one or both3’ends of the viral DNA to expose the invariant CA dinucleotides at both3’-ends of the viral DNA.2) The strand transfer reaction, in which the processed3’ends of the viral DNA are covalently ligated to the host chromosomal DNA. The integrase is also an attractive target for new anti-HIV drugs design and development.My research work could be divided into three sections, which are summarized as follows:Section One:The Design, Synthesis and Biological evaluation of novel DAPY derivatives as potential HIV-1NNRTIs.According to the crystal structure analysis of DAPYs-RT complexes and molecular modeling studies, the binding conformation of DAPYs resembled a characteristic "U" or horseshoe shape in the NNRTIs binding pocket (NNIBP) of RT, rather than the prototypical butterfly-like binding shape of the first-generation NNRTIs.The DAPY analogues generally contained three pharmacophoric moieties: substituted benzene or substituted piperidine in the protein/solvent interface interaction domain, a heterocycle moiety containing hydrogen bond donor and/or acceptor and a hydrophobic group.In particular, the six-membered or bicyclic heterocycle locating in the center of the NNIBP, not only anchors the functional groups for well engaging with the residues around NNIBP, but also serves as key hydrogen bond acceptor and donor (NH linker) to make key hydrogen bonds with the backbone of K101.These hydrogen bonds are critical for binding affinity of DAPYs especially in the cases of the appearance of K101mutant.More importantly, the X-ray crystallographic structure of piperidine-substituted DAPYs demonstrated that, besides the existing K101backbone hydrogen bond interaction, the piperidine nitrogen could probably make an additional hydrogen bond with the K103backbone (via a bridging water molecule), which has been regarded as an crucial factor for designing inhibitors with resilience to mutations.Moreover, as substituted piperidine points toward the solvent-exposed region, decorating of the right-wing piperidine by introducing suitable groups should be beneficial for the modulation of the aqueous solubility, physicochemical and pharmacokinetics properties of the NNRTIs.The conclusion lays the foundation for our further investigation. On the basis of the analysis and in connection with our previous endeavor to develop new, potent, selective and less toxic antiviral agents from fused heterocycles,we designed and synthesized two series of novel DAPY derivatives: thieno[3,2-d]pyrimidine derivatives and purines derivatives.Preliminary biological evaluation indicated that nearly half of purine derivatives possessed remarkable HIV inhibitory potencies in cellular assays. In particular, FZJ13appeared to be the most notable one, which displayed anti-HIV-1activity compared to3TC. Intriguingly, all of the thieno[3,2-d]pyrimidine derivatives showed high anti-HIV-1activity with EC50 values of3.25-26.56nM, which are more potent than NVP、3TC、ddI and DLV. Compound FF06showed the highest activity with the EC50value of3.25nM. Encouragingly, nearly all the thieno[3,2-d]pyrimidine derivatives showed high activities against K103N+Y181C double mutant HIV-1virus, which worth further investigation and development.Section Two:The Design, Synthesis and Biological evaluation of novel S-DABO derivatives as potential HIV-1NNRTIs.In an effort to explore novel S-DABO derivatives as potent HIV-1NNRTIs, we had designed a series of novel S-DABO analogues with the substituted1,2,3-triazole moiety on the C-2side chain were synthesized by using the simple and efficient the Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) reaction, and biologically evaluated as inhibitors of HIV-1. Generally, some of the synthesized compounds (B5bl, B5B3-B5b7) displayed remarkable anti-HIV-1(WT) activity in low micromolar level. Among these derivatives, the most potent HIV-1inhibitors were compound B5b7, which exhibited similar HIV-1inhibitory activity (EC50=3.22μM) compared with3TC (EC50=2.24μM). Even so, they were less active in comparison with the previously reported C-2substituted S-DABO derivatives and other reference drugs.SARs analysis indicated that substitution at C-6of the pyrimidine ring was the detrimental incident, since the2,6-dichlorobenzyl subseries were generally more active than the corresponding naphthalen-1-ylmethyl subseries. Only compound A5b7in naphthalen-1-ylmethyl series demonstrated weak HIV inhibitory effect. As previous SAR study of S-DABOs, the presence of suitable substituents at the C-5position of uracil ring was closely correlated with the antiviral activity. Optimal anti-HIV-1activity was obtained with compounds bearing a methyl moiety at the C-5site (B5b1-B5b7). There was still one compound (B5al) in C-5unsubstituted subseries (B5a1-B5a7) with EC50value in double-digit micromolar level. Whereas, when an iodine atom was introduced to this position, the bioactivity was completely impaired. Moreover, this study also suggested that the nature of the substituent on the4-position of the phenyl ring (terminal of C-2side chain) significantly influenced on the antiviral activity of these novel S-DABOs. Notably, among compounds B5b1-B5b7, SO2NH2(B5b7) appeared to be the most favorable group, closely followed in the sequence4-COMe>4-OMe>4-CN>4-CONH2>4-H>4-F.It is interesting to note that, in many types of NNRTIs, the optimum activity was often found with substituents containing hydrophilic group SO2NH2, indicating its nature can better accommodate the chemical environment in this region of RT and provide potential interactions with amino acids. Preliminary SAR studies in this paper provided some insights for discovery of more potent NNRTIs.Section Three:The Design, Synthesis and Biological evaluation of novel quinazolinone derivatives as potential HIV-1integrase inhibitors.The third part of this paper, based on the scaffold hopping strategy and taking the drug candidate PF-4776548in preclinical phase as a lead compound, we designed a series of compounds by replacing the pyridine hydroxamic acid groups of the lead compound with quinazolinone heterocyclic in order to simulate its metal chelating capacity. By using the simple and efficient CuAAC reaction, a series of novel and structurally diverse quinazolinone derivatives (M01-M13, E01-E13) were synthesized, and verified by spectral analysis. The synthesized compounds were biologically evaluated against HIV-1(ⅢB), HIV-2(ROD) in vitro by MTT method. Although none of activity was found in this series of compounds, the results provided useful information and implication for further seeking potent HIV-1integrase inhibitors.