In this study, 1R,2R-dicamphanoyl-3,3-dimethydihydropyrano[2,3-c]xanthen-7(1H)-one (DCX) derivatives were designed and synthesized as novel anti-HIV agents against both wild-type and nonnucleoside reverse transcriptase (RT) inhibitor-resistant HIV-1 (RTMDR-1) strains. Twenty-four DCX analogs (6-29) were synthesized and evaluated against the non-drug-resistant HIV-1 NL4-3 strain, and selected analogs were also screened for their ability to inhibit the RTMDR-1 strain. Compared with the control 2-ethyl-3′,4′-di-O-(-)-camphanoyl-2′,2′-dimethyldihydropyrano[2,3-f]chromone (2-EDCP, 2), one of the best anti-HIV coumarin derivatives in our prior study, three DCX compounds (7, 12, and 22) showed better activity against both HIV strains with an EC50 range of 0.062 – 0.081 μM, and five additional compounds (8, 11, 16, 18, and 21) exhibited comparable anti-HIV potency. Six DCX analogs (7, 11-12, 18, and 21-22) also showed enhanced selectivity index (SI) values in comparison to the control. Structure-activity relationship (SAR) information suggested that the extended conjugated system of the pyranoxanthone skeleton facilitates the interaction of the small DCX molecule within the viral binding pocket, consequently leading to enhanced anti-HIV activity and selectivity. Compared to DCP compounds, DCX analogs are a more promising new class of anti-HIV agents.
1R,2R-dicamphanoyl-3,3-dimethydihydropyrano[2,3-c]xanthen-7(1H)-one (DCX); Anti-HIV activity; Structure-activity relationship (SAR)
Six 3′R,4′R-di-O-(S)-camphanoyl-2′,2′-dimethyldihydropyrano[2,3-f]chromone (DCP) and two 3′R,4′R-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) derivatives were designed, synthesized, and evaluated for inhibition of HIV-1NL4-3 replication in TZM-bl cells. 2-Ethyl-2′-monomethyl-1′-oxa- and -1′-thia-DCP (5a, 6a), as well as 2-ethyl-1′-thia-DCP (7a) exhibited potent anti-HIV activity with EC50 values of 30, 38 and 54 nM and therapeutic indexes of 152.6, 48.0 and 100.0, respectively, which were better than or comparable to those of the lead compound 2-ethyl-DCP in the same assay. 4-Methyl-1′-thia-DCK (8a) also showed significant inhibitory activity with an EC50 of 128 nM and TI of 237.9.
2′-Monomethyl-1′-oxa-DCP; 2′-Monomethyl-1′-thia-DCP; 2-Ethyl-1′-thia-DCP; 4-Methyl-1′-thia-DCK; Anti-HIV activity
In a continuing study of novel anti-HIV agents with drug-like structures and properties, 30 1′-O-, 1′-S-, 4′-O- and 4′-substituted-2′,3′-seco-3′-nor DCP and DCK analogues (8–37) were designed and synthesized. All newly synthesized seco-compounds were screened against HIV-1NL4-3 and a multiple reverse transcriptase (RT) inhibitor-resistant (RTMDR) strain in the TZM-bl cell line, using seco-DCK (7) and 2-ethyl-DCP (4) as controls. Several compounds (14, 18, 19, 22–24, and 32) exhibited potent anti-HIV activity with EC50 values ranging from 0.93 to 1.93 μM and therapeutic index (TI) values ranging from 20 to 39. 1′-O-Isopropoxy-2′,3′-seco-3′-nor-DCP (12) showed the greatest potency among the newly synthesized compounds with EC50 values of 0.47 and 0.88 μM, and TI of 96 and 51, respectively, against HIV-1NL4-3 and RTMDR strains. The seco-compounds exhibited better chemical stability in acidic conditions compared with DCP and DCK compounds. Overall, the results suggested that seco-DCP analogues with simplified structures may be more favorable for development as novel anti-HIV candidates.
2′, 3′-Seco-3′-nor-DCPs; Anti-HIV activity; Structure–activity relationship (SAR)
In this study, 19 dicamphanoyl-dihydropyranochromone (DCP) and dicamphanoyl-dihydropyranoxanthone (DCX) derivatives, previously discovered as novel anti-HIV agents, were evaluated for their potential to reverse multi-drug resistance (MDR) in a cancer cell line over-expressing P-glycoprotein (P-gp). Seven compounds fully reversed resistance to vincristine (VCR) at 4 μM, a 20-fold enhancement compared to the first generation chemosensitizer, verapamil (4 μM). The mechanism of action of DCPs and DCXs was also resolved, since the most active compounds (3, 4, and 7) significantly increased intracellular drug accumulation due, in part, to inhibiting the P-gp mediated drug efflux from cells. We conclude that DCPs (3 and 4) and DCXs (7, 11, and 17) can exhibit polypharmacologic behavior by acting as dual inhibitors of HIV replication and chemoresistance mediated by P-gp. As such, they may be useful in combination therapy to overcome P-gp-associated drug resistance for AIDS treatment.
pyranochromone derivatives; chemoresistance; P-glycoprotein (P-gp) inhibitors; anti-HIV agents; dual function inhibitors
Thirteen novel seco-DCK analogs (4–16) with several new skeletons were designed, synthesized and screened for in vitro anti-HIV-1 activity. Among them, three compounds (5, 13, and 16) showed moderate activity, and compound 9 exhibited the best activity with an EC50 value of 0.058 μM and a therapeutic index (TI) of 1000. The activity of 9 was better than that of 4-methyl DCK (2, EC50: 0.126 μM, TI: 301.2) in the same assay. Additionally, 9 also showed antiviral activity against a multi-RT inhibitor-resistant strain (RTMDR), which is insensitive to most DCK analogs. Compared with 2, compound 9 has a less complex structure, fewer hydrogen-bond acceptors, and a reduced log P value. Therefore, it is likely to exhibit better ADME, and appears to be a promising new lead for further development as an anti-HIV candidate.
Seco-DCK analogs; Anti-HIV agents
Based on the favorable antiviral profiles of 4′-substituted nucleosides, novel 1-(2′-deoxy-2′-fluoro-4′-C-ethynyl-β-D-arabinofuranosyl)-uracil (1a), -thymine (1b), and – cytosine (2) analogues were synthesized. Compounds 1b and 2 exhibited potent anti-HIV-1 activity with IC50 values of 86 and 1.34 nM, respectively, without significant cytotoxicity. Compound 2 was 35-fold more potent than AZT against wild-type virus, and also retained nanomolar antiviral activity against resistant strains, NL4-3(K101E) and RTMDR. Thus, 2 merits further development as a novel NRTI drug.
2′-Deoxy-2′-fluoro-4′-C-ethynyl nucleosides; anti-HIV activity
In a continuing investigation into the pharmacophores and structure-activity relationship (SAR) of (3′R,4′R)-3′,4′-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) as a potent anti-HIV agent, 2′-monomethyl substituted 1′-oxa, 1′-thia, 1′-sulfoxide and 1′-sulfone analogs were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. Among them, 2′S-monomethyl-4-methyl DCK (5a) and 2′S-monomethyl-1′-thia-4-methyl DCK (7a) exhibited potent anti-HIV activity with EC50 values of 40.2 and 39.1 nM and remarkable therapeutic indexes of 705 and 1000, respectively, which were better than those of the lead compound DCK in the same assay. In contrast, the corresponding isomeric 2′R-monomethyl-4-methyl DCK (6) and 2′R-monomethyl-1′-thia-4-methyl DCK (8) showed much weaker inhibitory activity against HIV-1 replication. Therefore, the bioassay results suggest that the spatial orientation of the 2′-methyl group in DCK analogs can have important effects on anti-HIV activity of this compound class.
2′-Monomethyl-4-methyl-(3′R, 4′R)-3′; 4′-di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) analogs; 1′-Thia-4-methyl-(3′R,4′R)-3′; 4′-Di-O-(S)-camphanoyl-(+)-cis-khellactone (DCK) analogs; Anti-HIV activity; Structure-activity relationship (SAR)
1-(3,4,5-Trimethoxyphenyl)ethane-1,2-diyl esters, which share a fragment from (±)-3′-O-4′-O-bis(3,4-dimethoxycinnamoyl)-cis-khellactone (DMDCK) and 3′R,4′R-disubstituted-2′,2′-dimethyldihydropyrano[2,3-f]chromone (DSP), exhibited remarkable chemoreversal activity on multi-drug resistant human nasopharyngeal carcinoma (KB) when combined with three anti-cancer drugs, paclitaxel, vincristine and doxorubicin. Among 15 novel synthesized analogs, bis-trimethoxybenzoyl derivative 15 was the most active (340-fold more active than verapamil when used with vincristine) followed by two di-cinnamoyl derivatives, 10 and 11, and then di-cyclohexanecarbonyl derivative 9. All aliphatic chain derivatives, 3–5, showed no activity. Structure-activity relationship study indicated that a di-ester structure was critical to enhance the activity resulting from the maintenance of the spatial arrangement proposed by the pharmacophore based on the verapamil-binding site. Further mechanism of action study showed 15 inhibited mainly P-glycoprotein efflux pump function, while 13 exhibited an additional multidrug resistance-associated protein efflux pump function.
1-(3,4,5-Trimethoxyphenyl)ethane-1,2-diyl esters; Chemoreversal activity; KB cell line
A novel and efficient microwave-assisted one-pot reaction was developed to synthesize angular 2,2-dimethyl-2H-chromone containing compounds, which is the first and key step in the synthesis of potent DCK and DCP anti-HIV agents. The newly developed microwave synthesis conditions dramatically shortened the reaction time from 2 days to 4 hours with improved yields.
Microwave reaction; Angular 2; 2-dimethyl-2H-chromone; One-pot reaction; Anti-HIV
Two series (4 and 5) of diarylpyridine derivatives were designed, synthesized, and evaluated for anti-HIV-1 activity. The most promising compound, 5e, inhibited HIV-1 IIIB, NL4-3, and RTMDR1 with low nanomolar EC50 values and selectivity indexes of >10,000. The results of this study indicate that diarylpyridine can be used as a novel scaffold to derive a new class of potent NNRTIs, active against both wild-type and drug resistant HIV-1 strains.
diarylpyridine derivatives; HIV-1 NNRTIs; drug resistance
Tuberculosis remains one of the top three leading causes of morbidity and mortality worldwide, complicated by the emergence of drug-resistant Mycobacterium tuberculosis strains and high rates of HIV coinfection. It is important to develop new antimycobacterial drugs and immunomodulatory therapeutics and compounds that enhance antituberculous immunity. Dipterinyl calcium pentahydrate (DCP), a calcium-complexed pterin compound, has previously been shown to inhibit human breast cancer cells and hepatitis B virus (HBV). DCP inhibitory effects were attributed to induction of apoptosis and/or increased production of interleukin 12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF). In this study, we tested the ability of DCP to mediate inhibition of intracellular mycobacteria within human monocytes. DCP treatment of infected monocytes resulted in a significant reduction in viability of intracellular but not extracellular Mycobacterium bovis BCG. The antimicrobial activity of DCP was comparable to that of pyrazinamide (PZA), one of the first-line antituberculosis drugs currently used. DCP potentiated monocyte antimycobacterial activity by induction of the cysteine-cysteine (C-C) chemokine macrophage inflammatory protein 1β (MIP-1β) and inducible nitric oxide synthase 2. Addition of human anti-MIP-1β neutralizing antibody or a specific inhibitor of the l-arginase-nitric oxide pathway (NG-monomethyl l-arginine [l-NMMA] monoacetate) reversed the inhibitory effects of DCP on intracellular mycobacterial growth. These findings indicate that DCP induced mycobacterial killing via MIP-1β- and nitric oxide-dependent effects. Hence, DCP acts as an immunoregulatory compound enhancing the antimycobacterial activity of human monocytes.
A molecular model of pokeweed antiviral protein (PAP)-RNA interactions was used to rationally engineer FLP-102(151AA152) and FLP-105(191AA192) as nontoxic PAPs with potent anti-human immunodeficiency virus (anti-HIV) activities. FLP-102 and FLP-105 have been produced in Escherichia coli and tested both in vitro and in vivo. These proteins depurinate HIV type 1 (HIV-1) RNA much better than rRNA and are more potent anti-HIV agents than native PAP or recombinant wild-type PAP. They are substantially less toxic than native PAP in BALB/c mice and exhibit potent in vivo activities against genotypically and phenotypically nucleoside reverse transcriptase inhibitor-resistant HIV-1 in a surrogate human peripheral blood lymphocyte (Hu-PBL) SCID mouse model of human AIDS. Rationally engineered nontoxic recombinant PAPs such as FLP-102 and FLP-105 may provide the basis for effective salvage therapies for patients harboring highly drug-resistant strains of HIV-1. The documented in vitro potencies of FLP-102 and FLP-105, their in vivo antiretroviral activities in the HIV-infected Hu-PBL SCID mouse model, and their favorable toxicity profiles in BALB/c mice warrant the further development of these promising new biotherapeutic agents.
β-D-3′-Azido-2′,3′-dideoxyguanosine (3′-azido-ddG) is a potent inhibitor of HIV-1 replication with a superior resistance profile to zidovudine. Recently, we identified five novel 6-modified-3′-azido-ddG analogs that exhibit similar or superior anti-HIV-1 activity compared to 3′-azido-ddG in primary cells. To gain insight into their structure–activity–resistance relationships, we synthesized their triphosphate (TP) forms and assessed their ability to inhibit HIV-1 reverse transcriptase (RT). Steady-state and pre-steady-state kinetic experiments show that the 6-modified-3′-azido-ddGTP analogs act as adenosine rather than guanosine mimetics in DNA synthesis reactions. The order of potency of the TP analogs against wild-type RT was: 3′-azido-2,6-diaminopurine >3′-azido-6-chloropurine; 3′-azido-6-N-allylaminopurine > 2-amino-6-N,N-dimethylaminopurine; 2-amino-6-methoxypurine. Molecular modeling studies reveal unique hydrogen-bonding interactions between the nucleotide analogs and the template thymine base in the active site of RT. Surprisingly, the structure–activity relationship of the analogs differed in HIV-1 RT ATP-mediated excision assays of their monophosphate forms, suggesting that it may be possible to rationally design a modified base analog that is efficiently incorporated by RT but serves as a poor substrate for ATP-mediated excision reactions. Overall, these studies identify a promising strategy to design novel nucleoside analogs that exert profound antiviral activity against both WT and drug-resistant HIV-1.
In prior investigation, we discovered that (3'R,4'R)-3-cyanomethyl-4-methyl-3',4'-di-O-(S)-camphanoyl-(+)-cis-khellactone (4, 3-cyanomethyl-4-methyl-DCK) showed promising anti-HIV activity. In these current studies, we developed and optimized successfully a practical ten-step synthesis for scale-up preparation to increase the overall yield of 4 from 7.8% to 32%. Furthermore, compound 4 exhibited broad-spectrum anti-HIV activity against wild-type and drug-resistant viral infection of CD4+ T cell lines as well as peripheral blood mononuclear cells by both laboratory-adapted and primary HIV-1 isolates with distinct subtypes and tropisms. Compound 4 was further subjected to in vitro and in vivo pharmacokinetic studies. These studies indicated that 4 has moderate cell permeability, moderate oral bioavailability and low systemic clearance. These results suggest that 4 should be developed as a promising anti-HIV agent for development as a clinical trial candidate.
In a continuing structure-activity relationship study of potent anti-HIV agents, seven new triterpene derivatives were designed, synthesized, and evaluated for in vitro antiviral activity. Among them, moronic acid derivatives 19, 20 and 21 showed significant activity in HIV-1 infected H9 lymphocytes. Compounds 19 and 20 were also evaluated against HIV-1 NL4−3 and drug resistant strains in the MT-4 cell line. Compounds 19 and 20 showed better antiviral profiles than the betulinic acid analog 8 (PA-457), which has successfully completed a Phase IIa clinical trial. Compound 20 showed potent anti-HIV activity with EC50 values of 0.0085 μM against NL4−3, 0.021 μM against PI-R (a multiple protease inhibitor resistant strain), and 0.13 μM against FHR-2 (an HIV strain resistant to 8), respectively. The promising compound 20 has become a new lead for modification, and further development of 20-related compounds as clinical trial candidates is warranted.
The current optimization of 2,4-diarylaniline analogs (DAANs) on the central phenyl ring provided a series of new active DAAN derivatives 9a–9e, indicating an accessible modification approach that could improve anti-HIV potency against wild-type and resistant strains, aqueous solubility, and metabolic stability. A new compound 9e not only exhibited extremely high potency against wild-type virus (EC50 0.53 nM) and several resistant viral strains (EC50 0.36 – 3.9 nM), but also showed desirable aqueous solubility and metabolic stability, which were comparable or better than those of the anti-HIV-1 drug TMC278 (2). Thus, new compound 9e might be a potential drug candidate for further development of novel next-generation NNRTIs.
Diarylaniline; NNRTIs; lead optimization; anti-HIV agents
Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are one of the key components in highly active anti-retroviral therapy because of their high specificity and less toxicity. NNRTIs inhibit reverse transcriptase enzyme by binding to the allosteric site, which is 10Å away from the active site. Rapid emergence of resistance is the major problem with all anti-HIV agents. Hence, there is continuous need to develop novel anti-HIV agents active against both drug sensitive and resistance strains.
All the 16 synthesized 2-(1,3-dioxo-3a,4-dihydro-1H-isoindol-2(3H,7H,7aH)-yl)-N-(substitutedphenyl) acetamide 4(a-p) analogs were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, mass spectroscopy, and elemental analysis. Lipinski rule of five parameters and molecular parameters like solubility, drug likeness, and drug score were derived for designed analogs using online servers like Molinspiration and Osiris property explorer. Synthesized compounds were evaluated for their HIV-1 reverse transcriptase inhibitor activity by HIV-1 RNA-dependent DNA polymerase activity assay at 2 and 20 μM concentrations.
Among the 16 synthesized compounds, 4a, 4b, 4f, 4g, 4k, and 4l showed weak reverse transcriptase inhibitor activity at 20 μM concentration. For the designed compounds, there was no correlation observed between molecular modeling and in vitro studies.
NNRTIs; HAART; HIV-1 reverse transcriptase; Docking; Molecular properties; Autodock; Tetrahydrophthalimide
Bevirimat (1, BVM) is an anti-HIV agent that blocks HIV-1 replication by interfering with HIV-1 Gag-SP1 processing at a late stage of viral maturation. However, clinical trials of 1 have revealed a high baseline drug resistance that is attributed to naturally-occurring polymorphisms in HIV-1 Gag. To overcome the drug resistance, 28 new derivatives of 1 were synthesized and tested against compound 1-resistant (BVM-R) HIV-1 variants. Among them, compound 6 exhibited much improved activity against several HIV-1 strains carrying BVM-R polymorphisms. Compound 6 was at least 20-fold more potent than 1 against the replication of NL4-3/V370A, which carries the most prevalent clinical BVM-R polymorphism in HIV-1 Gag-SP1. Thus, compound 6 merits further development as a potential anti-AIDS clinical trial candidate.
Betulinic acid; Bevirimat; HIV-1; Maturation inhibitors; Bevirimat-resistance
Based on the structures and activities of our previously identified non-nucleoside reverse transcriptase inhibitors (NNRTIs), we designed and synthesized two sets of derivatives, diarylpyridines (A) and diarylanilines (B), and tested their anti-HIV-1 activity against infection by HIV-1 NL4-3 and IIIB in TZM-bl and MT-2 cells, respectively. The results showed that most compounds exhibited potent anti-HIV-1 activity with low nanomolar EC50 values, and some of them, such as 13m, 14c, and 14e, displayed high potency with subnanomolar EC50 values, which were more potent than etravirine (TMC125, 1) in the same assays. Notably, these compounds were also highly effective against infection by multi-RTI-resistant strains, suggesting a high potential to further develop these compounds as a novel class of NNRTIs with improved antiviral efficacy and resistance profile.
Non-nucleoside inhibitors of HIV reverse transcriptase (NNRTIs) are being pursued with guidance from molecular modeling including free energy perturbation (FEP) calculations for protein-inhibitor binding affinities. The previously reported pyrimidinylphenylamine 1 and its chloro analog 2 are potent anti-HIV agents; they inhibit replication of wild-type HIV-1 in infected human T-cells with EC50 values of 2 and 10 nM. However, they show no activity against viral strains containing the Tyr181Cys (Y181C) mutation in HIV-RT. Modeling indicates that the problem is likely associated with extensive interaction between the dimethylallyloxy substituent and Tyr181. As an alternative, a phenoxy group is computed to be oriented in a manner diminishing the contact with Tyr181. However, this replacement leads to a roughly 1000-fold loss of activity for 3 (2.5 μM). The present report details the efficient, computationally-driven evolution of 3 to novel NNRTIs with sub-10 nM potency towards both wild-type HIV-1 and Y181C-containing variants. The critical contributors were FEP substituent scans for the phenoxy and pyrimidine rings and recognition of potential benefits of addition of a cyanovinyl group to the phenoxy ring.
The previously reported CXCR4 antagonist KRH-1636 was a potent and selective inhibitor of CXCR4-using (X4) human immunodeficiency virus type 1 (HIV-1) but could not be further developed as an anti-HIV-1 agent because of its poor oral bioavailability. Newly developed KRH-3955 is a KRH-1636 derivative that is bioavailable when administered orally with much more potent anti-HIV-1 activity than AMD3100 and KRH-1636. The compound very potently inhibits the replication of X4 HIV-1, including clinical isolates in activated peripheral blood mononuclear cells from different donors. It is also active against recombinant X4 HIV-1 containing resistance mutations in reverse transcriptase and protease and envelope with enfuvirtide resistance mutations. KRH-3955 inhibits both SDF-1α binding to CXCR4 and Ca2+ signaling through the receptor. KRH-3955 inhibits the binding of anti-CXCR4 monoclonal antibodies that recognize the first, second, or third extracellular loop of CXCR4. The compound shows an oral bioavailability of 25.6% in rats, and its oral administration blocks X4 HIV-1 replication in the human peripheral blood lymphocyte-severe combined immunodeficiency mouse system. Thus, KRH-3955 is a new promising agent for HIV-1 infection and AIDS.
Since the emergence of drug-resistant mutants has limited the efficacy of non-nucleoside reverse transcriptase inhibitors (NNRTIs), it is essential to develop new antivirals with better drug-resistance and pharmacokinetic profiles. Here we designed and synthesized a series of 1-[(2-benzyloxyl/alkoxyl)methyl]-5-halo-6-aryluracils, the HEPT analogues, and evaluated their biological activity using Nevirapine and 18 (TNK-651) as reference compounds. Most of these compounds, especially 6b, 7b, 9b, 11b and 7c, exhibited highly potent anti-HIV-1 activity against both wild-type and NNRTI-resistant HIV-1 strains. The compound 7b, that had the highest selectivity index (SI = 38,215), is more potent than Nevirapine and 18. These results suggest that introduction of halogen at the C-5 position may contribute to the effectiveness of these compounds against RTI-resistant variants. In addition, m-substituents on the C-6 aromatic moiety could significantly enhance activity against NNRTI-resistant HIV-1 strains. These compounds can be further developed as next-generation NNRTIs with improved antiviral efficacy and drug-resistance profile.
HIV-1; Non-nucleoside reverse transcriptase inhibitors (NNRTIs); Drug-resistance
There is still an urgent need to develop nonnucleoside reverse transcriptase (RT) inhibitors (NNRTI) with a high-genetic barrier to resistance that facilitate patient adherence and allow durable suppression of HIV-1 replication. In this study, we describe the synthesis of a novel series of N-aminoimidazole (NAIM) analogs. Each of the NAIM analogs display potent activity against wild-type recombinant purified HIV-1 RT as well as RTs containing the K103N or Y181C resistance mutations. The analogs, however, do not exhibit significant antiviral activity in cell culture and were, in general, cytotoxic. Nevertheless, these data suggest that the NAIM backbone may provide a suitable scaffold from which inhibitors active against NNRTI-resistant HIV-1 could be developed.
N-aminoimidazole; NNRTI; HIV; reverse transcriptase; synthesis; molecular modeling
SDZ NIM 811 is a cyclosporin A analog that is completely devoid of immunosuppressive capacity but exhibits potent and selective anti-human immunodeficiency virus type 1 (HIV-1) activity. The mechanism of action of SDZ NIM 811 is clearly different from those of all other anti-HIV agents described so far. In cell-free assays, it is not an inhibitor of reverse transcriptase, protease, integrase, and it does not interfere with Rev or Tat function. SDZ NIM 811 does not down-regulate CD4 or inhibit fusion between infected and uninfected, CD4-expressing cells. p24 production from chronically HIV-infected cells is not impaired either. To elucidate the mode of action of SDZ NIM 811, we performed DNA PCR analysis in HIV-1 IIIB-infected MT4 cells in one cycle of virus replication. The effects of SDZ NIM 811 on the kinetics of viral DNA synthesis, appearance of two-long terminal repeat circles (2-LTR circles), and integration of DNA were studied. SDZ NIM 811 inhibited 2-LTR circle formation in a concentration-dependent manner, which is indicative of nuclear localization of preintegration complexes. Half-maximal inhibition was achieved at 0.17 microgram/ml; this concentration is close to the 50% inhibitory concentrations (0.01 to 0.2 microgram/ml) for viral growth inhibition. As expected, integration of proviral DNA into cellular DNA was also inhibited by SDZ NIM 811. Analysis of the viral particles produced by SDZ NIM 811-treated, chronically infected cells revealed amounts of capsid proteins, reverse transcriptase activity, and viral RNA comparable to those of the untreated control. However, these particles showed a dose-dependent reduction in infectivity (50% inhibitory concentration of 0.028 microgram/ml) which indicates that the assembly process is also impaired by SDZ NIM 811. Gag proteins are postulated to play a role not only in assembly but also in early steps of viral replication, e.g., nuclear localization of the preintegration complex. Recently, it was reported that HIV-1 Gag protein binds to cyclophilin A, the intracellular receptor for cyclosporin A. Interference with Gag-cyclophilin interaction may be the molecular basis for the antiviral activity of cyclosporin A and its analogs.
In this study, various 3′R,4′R-disubstituted-2′,2′-dimethydihydropyrano[2,3-f]chromone (DSP) derivatives were discovered as potent chemosensitizers in the treatment of multidrug resistant cancer cells. Twenty-four DSP analogs (5–28) were synthesized and evaluated against a multi-drug resistant (MDR) cell line (KB-Vin) with and without vincristine (VCR). All DSP analogs exhibited low intrinsic cytotoxicity. However, in combination treatment, most DSPs reversed resistance to VCR and lowered the GI50 value of VCR by 12–349-fold. At a concentration of 1μg/mL, three compounds, 11, 14 and 21, fully reversed resistance to VCR in KB-Vin cancer cells, a twofold increase compared to verapamil, a first generation chemosensitizer. Detailed structure-activity relationship (SAR) conclusions were established based on 3′ and 4′ substitutions. Moreover, a preliminary mechanism study indicated that the chemosensitizing activity of DSP analogs results from inhibition of P-glycoprotein (P-gp) over-expressed in MDR cancer cells.1