Discovery Of Piperidine-linked Quinazoline Derivatives As Potent HIV-1 NNRTIs And HIV-1 Latent Reservoir Activators

Acquired immune deficiency syndrome(AIDS),mainly caused by human immunodeficiency virus type-1(HIV-1),is still one of the leading causes of death worldwide.The highly active antiretroviral therapy(HAART)regimens,a combination of three or more HIV-1 antiretroviral targeting different steps of active viral replication,is used as the most efficient treatment regimen in controlling HIV-1 replication in infected individuals.Non-nucleoside reverse transcriptase inhibitors(NNRTIs)comprise an important component of HAART,owing to their potent antiviral activity,high selectivity and generally good tolerance.However,the efficacy of NNRTIs is compromised by the emergence of drug-resistant mutations,poor pharmacokinetic properties and severe toxic side effects over long-term treatment.These impose the development of new NNRTIs with broader antiviral spectrum and better pharmacokinetic properties.NNRTIs induce conformational change of the active site by binding to HIV-1 reverse transcriptase at a site distinct from the DNA polymerase active site of the enzyme,and inhibit retroviral reverse transcription step of HIV-1 replication in a non-competitive manner.Over the past few years,diarylpyrimidine(DAPY)-based NNRTIs,represented by etravirine(ETR)and rilpivirine(RPV),have attracted considerable attention because of their exceptional characteristics such as positional adaptability and conformational flexibility,which might serve to minimize the loss of binding stabilization caused by mutations.In addition,the key hydrogen bonds and specifically targeting conserved residues of reverse transcriptase provide important avenues for further optimization and development of anti-HIV drug candidates.This thesis has two parts.Part Ⅰ.Design,Synthesis and Biological Evaluation of Piperidine-linked Quinazoline Derivatives as Potent HIV-1 NNRTIsBy employing molecular hybridization and scaffold hopping strategy,the two tolerant regions of non-nucleoside inhibitory binding pocket(NNIBP)were explored to generate structurally distinct and potent DAPY-like antiviral inhibitors.The right-wing p-cyanoaniline of ETR was replaced by benzyl-linked piperidine,and quinazoline was introduced instead of the central pyrimidine ring to the tolerant region II of NNIBP,where as the left wing(trisubstitutedphenoxy ring)was retained.Accordingly,20 new piperidine-substituted quinazoline derivatives were synthesized by successive nucleophilic substitution reaction,introducing some hydrophilic groups on the aryl moiety directed toward tolerant region I to improve physicochemical properties.The bioactivity assay of newly synthesized compounds against HIV-1 wild type NL4-3 strain in TZM-bl cells demonstrated that HIV-1 was generally quite sensitive to these compounds,with EC50 values ranging from 1.4-38.2 nM.Among them,several new compounds yielded a single digit nanomolar inhibitory activity.The four most potent compounds against NL4-3 strain were selected to further evaluate their activity against NNRTI "super resistant" strain,NL4-3-(K101P,K103N,V108I),and interestingly,all of them exhibited impressive activity over RPV,the latest clinically used NNRTI.Particularly,SKC1 was identified to be exceptionally potent with EC50 value 0.10 μM,being about 3-fold more potent than RPV(EC50>0.27 μM).In addition,structural activity relationships(SARs)and molecular simulation studies were discussed suggesting a high potential for further optimization of these compounds.Part Ⅱ.Discovery of HIV-1 Latent Reservoir Activators:Design,Synthesis,and EvaluationAlthough HAART effectively suppresses HIV-1 replication,the persistence of HIV-1 in the latent viral reservoirs is the major obstacle to cure AIDS.This is due to ability of viral genome to establish state of latent infection in a long lived cells,mainly a resting memory CD4+ T cells,and can efficiently initiate viral replication should HAART be discontinued.One proposed cure strategy for HIV-1 involves ’shocking’ these viruses out of latent reservoir using latency reversing agents(LRAs)so that they can be eliminated through immune clearance and/or viral replication-induced cytopathic effects.Histone deacetylase inhibitors(HDACIs)and G9a histone methyl tranferase inhibitors(G9a HMTIs)are among drug candidates for reactivation of a HIV-1 latent virus.Discovery of HIV-1 latent reservoir activators were discussed in the third chapter.Anticipating that concurrent inhibition of G9a and HDAC may enhance histone protein to maintain the transcriptional activity via targeting two pathways,G9a-HDAC dual inhibitors were designed by fusing zinc-binding group of HDACIs currently under clinical study(hydroxamic acid or o-phenylenediamine)at the protein-solvent interface of substituted 6,7-dimethoxyquinazoline pharmacophore of G9a inhibitor BIX-01294.Unfortunately,among a dozen of novel compounds synthesized and evaluated,only two compounds activated HIV-1 replication in U1 cell latent HIV-1 model at a single-digit micromolar concentration(LC4,EC50>8 μM and LC10,EC50>6.65 μM),which is still lower than that of reference drug,vorinostat(SAHA,EC50= 0.98 μM).Even though the activity of this series of compounds was not high,the findings will provide a clue for further development of HIV-1 latency reversing agents with the ultimate goal of achieving HIV-1 cure.