Potent Anti-human Immunodeficiency Virus Research Articles

Dereplication of 4-Quinolone Alkaloids from Waltheria Indica (Malvaceae) Tissues Using Molecular Network Tools.

Waltheria indica (Malvaceae) is a plant popularly used in folk medicine by traditional African and indigenous communities, and in various countries worldwide, to treat general inflammation. Several biological activities of this plant have been reported, including acetylcholinesterase inhibition and potential anti-human immunodeficiency virus (HIV), antinociceptive, analgesic, antifungal, anticancer, anti-inflammatory, leishmanicidal, trypanocidal, antioxidant, and antibacterial activities. The chemical profile of Waltheria indica was assessed by dereplication analysis using UPLC-MS/MS, and data acquisition was performed using chemoinformatics tools, such as Mass Spectrometry-Data Independent AnaLysis (MS-DIAL) and MS-FINDER softwares. The preprocessed data were sent to the GNPS to build a feature-based molecular network (FBMN). Thirty-three 4-quinolone alkaloids were annotated in the extracts and fractions of stems and roots, whereas 12 were annotated in the extracts and fractions of flowers and leaves. This represents an inaugural chemical investigation study employing UPLC-Q-TOF-MS/MS analysis, along with a molecular network approach, within this species and genus.

Late-Stage Derivatization of Oleanolic Acid-Based Anti-HIV-1 Compounds.

A 12-keto-type oleanolic acid derivative (4) has been identified as a potent anti-human immunodeficiency virus type-1 (HIV-1) compound that demonstrates synergistic effects with several types of HIV-1 neutralizing antibodies. In the present study, we used a common key synthetic intermediate to carry out the late-stage derivatization of an anti-HIV compound based on the chemical structure of a 12-keto-type oleanolic acid derivative. To execute this strategy, we designed a diketo-type oleanolic acid derivative (5) for chemoselective transformation, targeting the carboxy group and the hydroxyl group on the statine unit, as well as the 3-carbonyl group on the oleanolic acid unit, as orthogonal synthetic handles. We carried out four types of chemoselective transformations, leading to identification of the indole-type derivative (16) as a novel potent anti-HIV compound. In addition, further optimization of the β-hydroxyl group on the statine unit provided the R-4-isobutyl γ-amino acid-type derivative (6), which exhibited potent anti-HIV activity comparable to that of 4 but with reduced cytotoxicity.

You Shall Not Pass: MX2 Proteins Are Versatile Viral Inhibitors.

Myxovirus resistance (MX) proteins are pivotal players in the innate immune response to viral infections. Less than 10 years ago, three independent groups simultaneously showed that human MX2 is an interferon (IFN)-stimulated gene (ISG) with potent anti-human immunodeficiency virus 1 (HIV-1) activity. Thenceforth, multiple research works have been published highlighting the ability of MX2 to inhibit RNA and DNA viruses. These growing bodies of evidence have identified some of the key determinants regulating its antiviral activity. Therefore, the importance of the protein amino-terminal domain, the oligomerization state, or the ability to interact with viral components is now well recognized. Nonetheless, there are still several unknown aspects of MX2 antiviral activity asking for further research, such as the role of cellular localization or the effect of post-translational modifications. This work aims to provide a comprehensive review of our current knowledge on the molecular determinants governing the antiviral activity of this versatile ISG, using human MX2 and HIV-1 inhibition as a reference, but drawing parallelisms and noting divergent mechanisms with other proteins and viruses when necessary.

Potent and Selective Activity against Human Immunodeficiency Virus 1 (HIV-1) of Thymelaea hirsuta Extracts.

Historically, natural products have been the most successful source of inspiration for the development of new drugs. Members of the Thymelaeaceae family have been of interest owing to their excellent medicinal value. Given the successful history of natural product-based drug discovery, extracts from the aerial parts of Thymelaea hirsuta were evaluated for their potential anti-human immunodeficiency virus type 1 (HIV-1) activity. Ethyl acetate extracts from leaves (71B) and branches (72B) of Thymelaea hirsuta showed potent and selective activity against HIV-1 wt (EC50 = 0.8 µg/mL) at non-cytotoxic concentrations (CC50 > 100 µg/mL). They proved to be active against HIV-1 variants carrying clinically relevant NNRTI and NRTI mutations at low concentration (0.3–4 µg/mL range) and against the M-tropic strain HIV-1 BaL. The 72B extract, chosen as a lead, was not able to inhibit the RT and protease enzymatic functions. Furthermore, it was not virucidal, since exposure of HIV to high concentration did not affect virus infectivity. The pre-clinical safety profile of this extract showed no adverse effect on the growth of Lactobacilli, and non-toxic concentration of the extract did not influence the Caco-2 epithelial cells monolayer integrity. Additionally, extract 72B prevented syncytia formation at low concentration (0.4 µg/mL). The potent inhibitory effect on the syncytia formation in co-cultures showed that 72B inhibits an early event in the replication cycle of HIV. All of these findings prompt us to carry on new studies on Thymelaea hirsuta extracts.

Pharmacophore model and atom-based 3D quantitative structure activity relationship (QSAR) of human immunodeficiency virus-1 (HIV-1) capsid assembly inhibitors

A potential anti-Human Immunodeficiency Virus (HIV) agent with novel mode of action is urgently needed to fight against drug resistance HIV. The HIV capsid protein is important for both late and early stages of the viral replication cycle and emerged as a promising target for the developing of small molecule inhibitors of HIV. We design a Pharmacophore and 3D Quantitative structure activity relationship (QSAR) model for HIV Capsid Protein inhibitors, which helps to identify overall aspects of molecular structure that govern activity and for the prediction of novel HIV Capsid inhibitors. The hypothesis was developed with a survival score of 3.6.The features, that is, two aromatic rings, one hydrophobic site and two acceptor regions were present in all the active compounds with good fitness score. Pharmacophore model was then validated by a partial least square and regression-based PHASE 3D QSAR cross-validation. The leave-n-out cross validation for test set (Q2) of the hypothesis is 0.636, the standard deviation (SD) value is 0.338, and the variance ratio (F-test) value is 74.5. Hypothesis also showed a leave-n-out cross validation for training set (R2, 0.928). Interestingly, the predicted activity of true test set compounds was found in the close vicinity of their experimental activity suggesting the methodology used and models generated can be applied to identify potential new chemical entities with better HIV-1 capsid assembly inhibition.Communicated by Ramaswamy H. Sarma

Design, Synthesis, and Biological Evaluation of EdAP, a 4'-Ethynyl-2'-Deoxyadenosine 5'-Monophosphate Analog, as a Potent Influenza a Inhibitor.

Influenza A viruses leading to infectious respiratory diseases cause seasonal epidemics and sometimes periodic global pandemics. Viral polymerase is an attractive target in inhibiting viral replication, and 4′-ethynyladenosine, which has been reported as a highly potent anti-human immunodeficiency virus (HIV) nucleoside derivative, can work as an anti-influenza agent. Herein, we designed and synthesized a 4′-ethynyl-2′-deoxyadenosine 5′-monophosphate analog called EdAP (5). EdAP exhibited potent inhibition against influenza virus multiplication in Madin–Darby canine kidney (MDCK) cells transfected with human α2-6-sialyltransferase (SIAT1) cDNA and did not show any toxicity toward the cells. Surprisingly, this DNA-type nucleic acid analog (5) inhibited the multiplication of influenza A virus, although influenza virus is an RNA virus that does not generate DNA.

Docking Studies of HIV-1 Reverse Transcriptase and HIV-1 Integrase with Phytocompounds of Carissa Carandas L.

Background Carissa carandas L. is a well-known wild fruit plant distributed through-out the India and also present in other countries. The fruits are rich in nutrients and minerals. A number of medicinally important phytochemicals such as carrisone, carindone, carandinol, lupeol, scopoletin, stigmasterol, β-sitosterol, myo-inositol, β-amyrin, Des-n-methylnoracronycine etc. have been reported from the extract of this plant. Being safe and cost effective molecules, the activity of phytochemicals against HIV-1 enzymes needs to be screened. Objective The aim of this study was to screen the potent phytocompound of C. carandas against human immunodeficiency virus-1 using docking method. Methods Total nine compounds viz. carandinol, caridone, carrisone, lupeol, p-coumaric acid, gallic acid, rutin, scopoletin and ursolic acid were used for in-silico study towards drug development against human immunodeficiency virus-1 reverse transcriptase (HIV-1RT; PDB ID: 1REV) and human immunodeficiency virus-1 protease (PDB ID:1EBY) using Autodock software. Results The qualitative characterization of the extracts showed the presence of a number of phytochemicals such as phenolics, flavonoids, alkaloids, terepnoids, terpenes, steroids, glycosides etc. Carandinol was observed as most effective anti-HIV-1 molecule having lowest binding energy and small inhibition coefficient. Another compound, p-coumaric acid, showed least effectiveness against human immunodeficiency virus- 1 reverse transcriptase or human immunodeficiency virus-1 protease showing highest binding energy and inhibition coefficients among all the evaluated phytocompounds. Conclusion The in-silico study demonstrated that some phytoconstituents of C. carandas exhibit potential anti-human immunodeficiency virus -1 activity and hence can be optimized to develop as a drug candidate in future.

Expanding the Antiviral Spectrum of 3-Fluoro-2-(phosphonomethoxy)propyl Acyclic Nucleoside Phosphonates: Diamyl Aspartate Amidate Prodrugs.

Acyclic nucleosides containing a 3-fluoro-2-(phosphonomethoxy)propyl (FPMP) side chain are known to be moderately potent antihuman immunodeficiency virus (HIV) agents, while being completely devoid of antiviral activity against a wide range of DNA viruses. The derivatization of the phosphonic acid functionality of FPMPs with a diamyl aspartate phenoxyamidate group led to a novel generation of compounds that not only demonstrate drastically improved antiretroviral potency but also are characterized by an expanded spectrum of activity that also covers hepatitis B and herpes viruses. The best compound, the (S)-FPMPA amidate prodrug, exerts anti-HIV-1 activity in TZM-bl and peripheral blood mononuclear cells at low nanomolar concentrations and displays excellent potency against hepatitis B virus (HBV) and varicella-zoster virus (VZV). This prodrug is stable in acid and human plasma media, but it is efficiently processed in human liver microsomes with a half-life of 2 min. The (R) isomeric guanine derivative emerged as a selectively active anti-HIV and anti-HBV inhibitor, while being nontoxic to human hepatoblastoma cells. Notably, the pyrimidine containing prodrug (S)-Asp-FPMPC is the only congener within this series to demonstrate micromolar antihuman cytomegalovirus (HCMV) potency.

Oral and Vaginal Tenofovir for Genital Herpes Simplex Virus Type 2 Shedding in Immunocompetent Women: A Double-Blind, Randomized, Cross-over Trial.

Tenofovir is a potent anti-human immunodeficiency virus (HIV) agent that decreased risk of herpes simplex virus type 2 (HSV-2) acquisition in HIV pre-exposure prophylaxis trials. Whether tenofovir has utility in established HSV-2 disease is unclear. We randomized immunocompetent women with symptomatic HSV-2 infection to oral tenofovir disoproxil fumarate (TDF)/placebo vaginal gel, oral placebo/tenofovir (TFV) vaginal gel, or double placebo (ratio 2:2:1) in a one-way cross-over trial. Women collected genital swabs twice daily for HSV PCR during 4-week lead-in and 5-week treatment phases. The primary intent-to-treat end point was within-person comparison of genital HSV shedding and lesion rates. 64 women completed the lead-in phase and were randomized. Neither TDF nor TFV gel decreased overall shedding or lesion rate in the primary analysis; TFV gel decreased quantity of HSV DNA by -0.50 (-0.86-0.13) log10 copies/mL. In the per-protocol analysis, TDF reduced shedding (relative risk [RR] = 0.74, P = .006) and lesion rates (RR = 0.75, P = .032); quantity of virus shed decreased by 0.41 log10 copies/mL. Oral TDF modestly decreased HSV shedding and lesion rate, and quantity of virus shed when used consistently. Vaginal TFV gel decreased quantity of virus shed by 60%. In contrast to effects on HSV-2 acquisition, tenofovir is unlikely to provide clinically meaningful reductions in the frequency of HSV shedding or genital lesions. NCT01448616.

Molecular Docking and Molecular Dynamics to Identify a Novel Human Immunodeficiency Virus Inhibitor from Alkaloids of Toddalia asiatica.

Background:Acquired immunodeficiency syndrome caused by human immunodeficiency virus (HIV) is an immunosuppressive disease. Over the past decades, it has plagued human health due to the grave consequences in its harness.Objective:For this reason, anti-HIV agents are imperative, and the search for the same from natural resources would assure the safety.Materials and Methods:In this investigation we have performed molecular docking, molecular property prediction, drug-likeness score, and molecular dynamics (MD) simulation to develop a novel anti-HIV drug. We have screened 12 alkaloids from a medicinal plant Toddalia asiatica for its probabilistic binding with the active site of the HIV-1-reverse transcriptase (HIV-1-RT) domain (the major contributor to the onset of the disease).Results:The docking results were evaluated based on free energies of binding (ΔG), and the results suggested toddanol, toddanone, and toddalenone to be potent inhibitors of HIV-1-RT. In addition, the alkaloids were subjected to molecular property prediction analysis. Toddanol and toddanone with more rotatable bonds were found to have a drug-likeness score of 0.23 and 0.11, respectively. These scores were comparable with the standard anti-HIV drug zidovudine with a model score 0.28. Finally, two characteristic protein-ligand complexes were exposed to MD simulation to determine the stability of the predicted conformations.Conclusion:The toddanol-RT complex showed higher stability and stronger H-bonds than toddanone-RT complex. Based on these observations, we firmly believe that the alkaloid toddanol could aid in efficient HIV-1 drug discovery.SUMMARY In the present study, the molecular docking and MD simulations are performed to explore the possible binding mode of HIV 1 RT with 12 alkaloids of T. asiatica. Molecular docking by AutoDock4 revealed three alkaloids toddanol, toddanone, and toddalenone with highest binding affinity towards HIV 1 RT. The drug likeness model score revealed a positive score for toddanol and toddanone which is comparable to the drug likeness score of the standard anti HIV drug zidovudine. Results from simulation analysis revealed that toddanol RT complex is more stable than toddanone RT complex inferring toddanol as a potential anti HIV drug molecule. Abbreviations used: HIV: Human immunodeficiency virus, HIV 1 RT: HIV 1 reverse transcriptase, RNase H: Ribonuclease H, MD: Molecular dynamics, PDB: Protein databank, RMSD: Root mean square deviation, RMSF: Root mean square fluctuation.

Naturally Occurring Calanolides: An Update on Their Anti-HIV Potential and Total Syntheses

Calanolides are naturally occurring pyranocoumarins found particularly in Calophyllum species (family Clusiaceae/ Guttiferae), and are well known for their potent anti-human immunodeficiency virus (HIV) activity. Various preclinical and clinical studies with this class of compounds are going on, and the National Cancer Institute (NCI) has been playing an active and supportive role in this regard. The present review covers an up-to-date literature of naturally occurring calanolides in view of their anti-HIV potential and total syntheses including information on related patents.

Synthesis of Novel 3′-Hydroxymethyl 5′-Deoxythreosyl Phosphonic Acid Nucleoside Analogues as Potent Antiviral Agents

A very efficient synthetic route to novel 3′-hydroxymethyl 5′-deoxythreosyl phosphonic acid nucleosides was described. The discovery of threosyl phosphonate nucleoside (PMDTA, EC50 = 2.53 μM) as a potent antihuman immunodeficiency virus (anti-HIV) agent has led to the synthesis and biological evaluation of 3′-modified 5′-deoxy versions of the threosyl phosphonate nucleosides. 3′-Hydroxymethyl 5 ′-deoxythreosyl phosphonic acid nucleoside analogues 15, 19, 24, and 28 were synthesized from 1,3-dihydroxyacetone and tested for anti-HIV activity as well as cytotoxicity. The adenine analogue 19 exhibits moderate in vitro anti-HIV-1 activity (EC50 = 10.2 μM).

Evaluation of the in vitro antiretroviral potential of some Biginelli-type pyrimidines

Despite the success of highly active antiretroviral therapy, AIDS still remains as one of the most important world health problems. Toxicity of current available drugs and inevitable emergence of multi-drug resistant strains makes things worse. In the present study a series of novel Biginelli-type pyrimidine compounds were evaluated as potential anti-human immunodeficiency virus (HIV)-1 agents using green fluorescence protein (GFP) reporter single round HIV-1 infection assay. The rate of infected cells was monitored by flowcytometry. The effect of compounds on the cellular proliferation was considered as the cyotoxicity. The anti-HIV-1 active compounds were selected for HIV-1 replication and syncytium formation assays. The antiretroviral activity of compounds was measured against luciferase reporter A murine leukemia virus (AMLV) virions as the retrovirus control. Compounds 2, 5, 6, 8, 11, 12, 13, 17, 18, 20, and 21 were the most potent against HIV-1. Compound 8 had the 50% inhibitory concentration (IC50) of 100 nmol/l for inhibiting HIV-1 replication and 50% cytotoxic concentration (CC50) was up to 100 μmol/l (therapeutic index (TI) >1000). Results show that the active compounds were able to inhibit the retrovirus control as well. Analysis of structure of the studied compounds proved relationships with their anti-HIV-1 effects. Some of the studied compounds seem to be promising anti-HIV-1 drug candidates. Structural manipulation based on the well-defined structure-activity relationships might propose some new leads for anti-HIV-1 drug discovery programs.

Discovery of 5,6-Dihydro-indolo[1,2-a]quinoxaline Derivatives as New HIV-1 Inhibitors In Vitro

In continuation of our program to find compounds with potent anti-human immunodeficiency virus type 1 (HIV-1) activities, seventeen 5,6-dihydro-indolo[1,2-a]quinoxaline derivatives (1-17) were preliminarily evaluated as HIV-1 inhibitors in vitro. Among all the derivatives, especially compounds 10 and 17 showed the most potent anti-HIV-1 activities with EC50 values of 2.42 and 3.39 μg/mL, and TI values of 63.76 and 53.60, respectively. Keywords: 5,6-Dihydro-indolo[1,2-a]quinoxaline, Acquired immunodeficiency syndrome, Human immunodeficiency virus-1, Inhibitor, AIDS, quinoxaline, HIV-1, Syncytia Assay, MTT-based Cytotoxicity Assay, TCID50, calf serum, Anti-HIV-1 Activity Assay, HIV-1 IIIB, Reed and Muench method

Expression analysis of the nucleocytoplasmic lectin ‘Orysata’ from rice in Pichia pastoris

The Oryza sativa lectin, abbreviated Orysata, is a mannose-specific, jacalin-related lectin expressed in rice plants after exposure to certain stress conditions. Expression of a fusion construct containing the rice lectin sequence linked to enhanced green fluorescent protein in Bright Yellow 2 tobacco cells revealed that Orysata is located in the nucleus and the cytoplasm of the plant cell, indicating that it belongs to the class of nucleocytoplasmic jacalin-related lectins. Since the expression level of Orysata in rice tissues is very low the lectin was expressed in the methylotrophic yeast Pichia pastoris with the Saccharomyces α-factor sequence to direct the recombinant protein into the secretory pathway and express the protein into the medium. Approximately 12 mg of recombinant lectin was purified per liter medium. SDS/PAGE and western blot analysis showed that the recombinant lectin exists in two molecular forms. Far western blot analysis revealed that the 23 kDa lectin polypeptide contains an N-glycan which is absent in the 18.5 kDa polypeptide. Characterization of the glycans present in the recombinant Orysata revealed high-mannose structures, Man9-11 glycans being the most abundant. Glycan array analysis showed that Orysata interacts with high-mannose as well as with more complex N-glycan structures. Orysata has potent anti-human immunodeficiency virus and anti-respiratory syncytial virus activity in cell culture compared with other jacalin-related lectins.

Identification of Specific Determinants of Human APOBEC3F, APOBEC3C, and APOBEC3DE and African Green Monkey APOBEC3F That Interact with HIV-1 Vif

Human APOBEC3F (hA3F) and human APOBEC3G (hA3G) are potent anti-human immunodeficiency virus (anti-HIV) host factors that suppress viral replication by hypermutating the viral genome, inhibiting reverse transcription, and hindering integration. To overcome hA3F and hA3G, HIV-1 encodes Vif, which binds and targets these host proteins for proteasomal degradation. Previously, we reported that the hA3F-Vif interactions that lead to hA3F degradation are located in the region comprising amino acids 283 to 300. We have now performed mutational analysis of this region and found that the (289)EFLARH(294) amino acids contribute to hA3F-Vif binding and are critical for A3F's sensitivity to Vif. Mutants in which E289 is mutated significantly increase hA3F's ability to inhibit viral infectivity in the presence of Vif, and coimmunoprecipitation assays show that binding of Vif to the E289K mutant is decreased. We examined the role of the EFLARH sequence in other A3 proteins, including human A3C (hA3C), human A3DE (hA3DE), African green monkey A3F (agmA3F), and rhesus macaque A3F (rhA3F). hA3C, hA3DE, and agmA3F were all susceptible to degradation induced by HIV-1 Vif, while rhA3F was not. Mutagenesis of the glutamate in the EFLARH sites of hA3C, hA3DE, and agmA3F decreases the susceptibilities of these proteins to Vif-induced degradation. Together, these results indicate that the EFLARH region in hA3F, hA3C, hA3DE, and agmA3F interacts with HIV-1 Vif and that this interaction plays a role in the Vif-mediated proteasomal degradation of these A3 proteins. These studies identify a conserved region in 3 of 7 human A3 proteins that is critical for degradation mediated by HIV-1 Vif and provide structural insights into the hA3F-Vif interactions that could facilitate the development of a novel class of anti-HIV agents.

Microvirin, a Novel α(1,2)-Mannose-specific Lectin Isolated from Microcystis aeruginosa, Has Anti-HIV-1 Activity Comparable with That of Cyanovirin-N but a Much Higher Safety Profile

Microvirin (MVN), a recently isolated lectin from the cyanobacterium Microcystis aeruginosa PCC7806, shares 33% identity with the potent anti-human immunodeficiency virus (HIV) protein cyanovirin-N (CV-N) isolated from Nostoc ellipsosporum, and both lectins bind to similar carbohydrate structures. MVN is able to inhibit infection by a wide variety of HIV-1 laboratory-adapted strains and clinical isolates of different tropisms and subtypes in peripheral blood mononuclear cells. MVN also inhibits syncytium formation between persistently HIV-1-infected T cells and uninfected CD4(+) T cells and inhibits DC-SIGN-mediated HIV-1 binding and transmission to CD4(+) T cells. Long term passaging of HIV-1 exposed to dose-escalating concentrations of MVN resulted in the selection of a mutant virus with four deleted high mannose-type glycans in the envelope gp120. The MVN-resistant virus was still highly sensitive to various other carbohydrate binding lectins (e.g. CV-N, HHA, GNA, and UDA) but not anymore to the carbohydrate-specific 2G12 monoclonal antibody. Importantly, MVN is more than 50-fold less cytotoxic than CV-N. Also in sharp contrast to CV-N, MVN did not increase the level of the activation markers CD25, CD69, and HLA-DR in CD4(+) T lymphocytes, and subsequently, MVN did not enhance viral replication in pretreated peripheral blood mononuclear cells. Therefore, MVN may qualify as a useful lectin for potential microbicidal use based on its broad and potent antiviral activity and virtual lack of any stimulatory properties and cellular toxicity.

Long-lasting enfuvirtide carrier pentasaccharide conjugates with potent anti-human immunodeficiency virus type 1 activity.

Enfuvirtide (also known as Fuzeon, T-20, or DP-178) is an antiretroviral fusion inhibitor which prevents human immunodeficiency virus type 1 (HIV-1) from entering host cells. This linear 36-mer synthetic peptide is indicated, in combination with other antiretroviral agents, for the treatment of HIV-1-infected individuals and AIDS patients with multidrug-resistant HIV infections. Although enfuvirtide is an efficient anti-HIV-1 drug, its clinical use is limited by a short plasma half-life, i.e., approximately 2 h, which requires twice-daily subcutaneous injections, often resulting in skin sensitivity reaction side effects at the injection sites. Ultimately, 80% of patients stop enfuvirtide treatment within 6 months because of these side effects. We report on the development of long-lasting enfuvirtide conjugates by the use of the site-specific conjugation of enfuvirtide to an antithrombin-binding carrier pentasaccharide (CP) through polyethylene glycol (PEG) linkers of various lengths. These conjugates showed consistent and broad anti-HIV-1 activity in the nanomolar range. The coupling of the CP to enfuvirtide only moderately affected the in vitro anti-HIV-1 activity in the presence of antithrombin. Most importantly, one of these conjugates, enfuvirtide-PEG(12)-CP (EP40111), exhibited a prolonged elimination half-life of more than 10 h in rat plasma compared to the half-life of native enfuvirtide, which was 2.8 h. On the basis of the pharmacokinetic properties of antithrombin-binding pentasaccharides, the anticipated half-life of EP40111 in humans would putatively be about 120 h, which would allow subcutaneous injection once a week instead of twice daily. In conclusion, EP40111 is a promising compound with strong potency as a novel long-lasting anti-HIV-1 drug.

Retention of Metabolites of 2′,3′-Didehydro-3′-Deoxy-4′-Ethynylthymidine, a Novel Anti-Human Immunodeficiency Virus Type 1 Thymidine Analog, in Cells

2',3'-Didehydro-3'-deoxy-4'-ethynylthymidine (4'-Ed4T), a novel thymidine analog, has more potent anti-human immunodeficiency virus type 1 (HIV-1) activity than its progenitor, stavudine (d4T). The profile of the intracellular metabolites of 4'-Ed4T was qualitatively similar to that of zidovudine (AZT) but not to that of d4T, while after drug removal it showed more persistent anti-HIV activity than AZT or d4T in cell culture. When CEM cells were exposed to various concentrations of 4'-Ed4T, 4'-Ed4T was efficiently taken up by the cells and was readily phosphorylated to 4'-Ed4T monophosphate (4'-Ed4TMP), 4'-Ed4T diphosphate (4'-Ed4TDP), and 4'-Ed4T triphosphate (4'-Ed4TTP). Most importantly, 4'-Ed4TTP, the active metabolite of 4'-Ed4T, persisted significantly longer than 4'-Ed4TDP and 4'-Ed4TMP after drug removal. We further investigated the efflux profiles of 4'-Ed4T in the comparison with those of AZT in CEM cells. After drug removal, both 4'-Ed4T and AZT were effluxed from the cells in a time- and temperature-dependent manner. However, the efflux of 4'-Ed4T from cells was much less efficient than that of AZT. 4'-Ed4T was effluxed from cells only in its nucleoside form, while AZT was effluxed from cells in both its nucleoside and monophosphate forms. The mechanism-of-action study showed that the efflux of 4'-Ed4T or AZT nucleoside might be due to unknown nucleoside transporters which were not related to the equilibrative nucleoside transporters, while the efflux of AZT monophosphate might be due to multidrug resistance protein 4 (MRP4/ABCC4). The results demonstrated that no detectable 4'-Ed4TMP efflux and the less efficient efflux of 4'-Ed4T nucleoside from cells might be one of the biochemical determinants of its persistent antiviral activity in cell culture.

Anti-AIDS Agents. 78. Design, Synthesis, Metabolic Stability Assessment, and Antiviral Evaluation of Novel Betulinic Acid Derivatives as Potent Anti-Human Immunodeficiency Virus (HIV) Agents

In a continuing study of potent anti-HIV agents, seventeen 28,30-disubstituted betulinic acid (BA, 1) derivatives and seven novel 3,28-disubstituted BA analogues were designed, synthesized, and evaluated for in vitro antiviral activity. Among them, compound 21 showed an improved solubility and equal anti-HIV potency (EC(50) = 0.09 microM) when compared to HIV entry inhibitors 3b (IC9564, (3R,4S)-N'-[N-[3beta-hydroxy-lup-20(29)-en-28-oyl]-8-aminooctanoyl]-4-amino-3-hydroxy-6-methylheptanoic acid) and 4 (A43-D, [[N-[3beta-O-(3',3'-dimethylsuccinyl)-lup-20(29)-en-28-oyl]-7-aminoheptyl]carbamoyl]methane). Using a cyclic secondary amine to form the C-28 amide bond increased the metabolic stability of the derivatives significantly in pooled human liver microsomes. The most potent compounds 47 and 48 displayed potent anti-HIV activity with EC(50) values of 0.007 and 0.006 microM, respectively. These results are slightly better than that of bevirimat (2, 3',3'-dimethylsuccinylbetulinic acid), which is currently in phase IIb clinical trials. Compounds 47 and 48 should serve as attractive promising leads to develop next generation, metabolically stable, 3,28-disubstituted bifunctional HIV-1 inhibitors as clinical trials candidates.