Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Calanolide A, recently discovered in extracts from the tropical rainforest tree, Calophyllum lanigerum, is a novel inhibitor of the human immunodeficiency virus (HIV) type 1. The compound is essentially inactive against strains of the less common HIV type 2. The present study focused on the further characterization of the selective antiviral activity and mechanism of action of calanolide A. The compound inhibited a wide variety of laboratory strains of HIV type 1, with EC50 values ranging from 0.10 to 0.17 microM. The compound similarly inhibited promonocytotropic and lymphocytotropic isolates from patients in various stages of HIV disease, as well as drug-resistant strains. Viral life-cycle studies indicated that calanolide A acted early in the infection process, similar to the known HIV reverse transcriptase (RT) inhibitor 2', 3'-dideoxycytidine. In enzyme inhibition assays, calanolide A potently and selectively inhibited recombinant HIV type 1 RT but not cellular DNA polymerases or HIV type 2 RT within the concentration range tested. Serial passage of the virus in host cells exposed to increasing concentrations of calanolide A yielded a calanolide A resistant virus strain. RT from the resistant virus was not inhibited by calanolide A but retained sensitivity to other nonnucleoside as well as nucleoside RT inhibitors, including 3'-azido-2',3'-dideoxythymidine triphosphate and nevirapine. The study substantially supports the conclusion that calanolide A represents a novel subclass of nonnucleoside RT inhibitor which merits consideration for anti-HIV drug development.
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PMID:Antiviral activity and mechanism of action of calanolide A against the human immunodeficiency virus type-1. 893 Jan 67

Calanolide A, first isolated from the tropical rain forest tree Calophyllum lanigerum, is a potent human immunodeficiency virus type-1 (HIV-1) specific reverse transcriptase (RT) inhibitor, broadly active against diverse HIV-1 strains, including nucleoside and nonnucleoside-resistant variants. We examined the biochemical mechanism of inhibition of HIV-1 RT by calanolide A. Two template/primer systems were examined: ribosomal RNA and homopolymeric rA-dT 12-18. Calanolide A inhibited HIV-1 RT by a complex mechanism involving two calanolide A binding sites. With respect to either deoxynucleotide triphosphate (dNTP) or template/primer binding, one site was competitive and the other was uncompetitive. The data indicated that calanolide A bound near the active site of the enzyme and interfered with dNTP binding. Calanolide A inhibited HIV-1 RT in a synergistic fashion with nevirapine, further distinguishing it from the general class of nonnucleoside RT inhibitors. At certain concentrations, calanolide A bound HIV-1 RT in a mutually exclusive fashion with respect to both the pyrophosphate analog, phosphonoformic acid and the acyclic nucleoside analog 1-ethoxymethyl-5-ethyl-6-phenylthio-2-thiouracil. This indicates that calanolide A shares some binding domains with both phosphonoformic acid and 1-ethoxymethyl-5-ethyl-6-phenylthio-2-thiouracil, presumably reflecting that it interacts with RT near both the pyrophosphate binding site and the active site of the enzyme.
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PMID:Kinetic analysis of inhibition of human immunodeficiency virus type-1 reverse transcriptase by calanolide A. 893 Jan 68

(+)-Calanolide A is a potent inhibitor of reverse transcriptase from human immunodeficiency virus type 1 (HIV-1), which was isolated from an extract of Calophyllum lanigerum, along with seven related compounds. In order to examine the structure-activity relationships of the trans-10,11-dimethyldihydropyran-12-ol ring (designated ring C), a series of structural analogues were prepared and evaluated using a whole cell cytopathicity assay (XTT). Removal of the 10-methyl group resulted in decreased activity, with only one epimer exhibiting anti-HIV activity. Substituting the 10-methyl group with an ethyl chain maintained anti-HIV activity, with only a 4-fold reduction in potency relative to racemic calanolide A. Substitution of the 10-methyl group with an isopropyl moiety completely eliminated the anti-HIV activity. Addition of an extra methyl group at either the 10- or 11-position maintained the basic stereochemical features of the parent calanolide system while removing the chirality at the respective carbon, but resulted in decreased activity relative to calanolide A. In all the above examples, analogues containing a cis relationship between the 10- and 11-alkyl moieties were completely devoid of activity. Synthetic intermediates in which the 12-hydroxyl group was in the ketone oxidation state exhibited suppressing anti-HIV activity, with EC50 values only 5-fold less potent than that of calanolide A for both the 10,11-cis (6) and -trans (5) series. These ketones represent the first derivatives in the calanolide series to exhibit anti-HIV activity while not containing a 12-hydroxyl group. Likewise, ketone derivative 6 was the first example of a compound in the calanolide series having a cis relationship between the 10- and 11-methyl groups found to exhibit anti-HIV activity. Analogues which showed anti-HIV activity in the CEM-SS cytoprotection assay were further confirmed to be inhibitors of HIV-1 reverse transcriptase.
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PMID:Structural analogues of the calanolide anti-HIV agents. Modification of the trans-10,11-dimethyldihydropyran-12-ol ring (ring C). 908 91

(+)-Calanolide A, a novel dipyranocoumarin from the Malesian tree Calophyllum lanigerum var. austrocoriaceum, and a closely related compound, (-)-calanolide B, isolated from Calophyllum teysmannii var. inophylloide, are representatives of a distinct class of nonnucleoside HIV-1 specific reverse-transcriptase inhibitor under development as an AIDS chemotherapeutic. NCI repository specimens totalling 315 organic extracts from 31 taxa of Calophyllum were analyzed for related pyranocoumarins using a simple TLC system. A total of 127 extracts was initially classified as "positive"; eight out of the 31 taxa examined, representing perhaps 28 species already described (1/7-1/8 of all the species in this genus), contained prenylated coumarins, suggesting that these compounds, while sometimes abundantly present, are not widespread in the genus. Representative members of the TLC-positive extracts were partitioned between CH2C12 and 25% aqueous MeOH; the CH2C12-soluble materials were then analyzed by TLC and 1H NMR to confirm the presence of pyranocoumarins. The anti-HIV activity of the partitioned extracts are also presented. This study suggested that there are several distinctive coumarin chemotaxonomic markers distinguishing species of this genus.
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PMID:Pyranocoumarins from tropical species of the genus Calophyllum: a chemotaxonomic study of extracts in the National Cancer Institute collection. 978 62

The natural product (+)-calanolide A, a unique non-nucleoside reverse transcriptase inhibitor (NNRTI) of HIV-1 replication, is currently being evaluated in clinical trials in the USA. (+)-Calanolide A, the congeners costatolide and dihydrocostatolide, and (+)-12-oxo(+)-calanolide A, were evaluated in combination with a variety of mechanically diverse inhibitors of HIV replication to define the efficacy and cellular toxicity of potential clinical drug combinations. These assays should be useful in prioritizing the use of different combination drug strategies in a clinical setting. The calanolides exhibited synergistic antiviral interactions with other nucleoside and non-nucleoside reverse transcriptase inhibitors and protease inhibitors. Additive interactions were also observed when the calanolides were used with representative compounds from each of these classes of inhibitors. No evidence of either combination toxicity or antagonistic antiviral activity was detected with any of the tested compounds. The combination antiviral efficacy of three-drug combinations involving the calanolides, and the efficacy of two- and three-drug combinations using a (+)-calanolide A-resistant challenge virus (bearing the T139I amino acid change in the reverse transcriptase), was also evaluated in vitro. These assays suggest that the best combination of agents based on in vitro anti-HIV assay results would include the calanolides in combination with lamivudine and nelfinavir, since this was the only three-drug combination exhibiting a significant level of synergy. Combination assays with the (+)-calanolide A-resistant strain yielded identical results as seen with the wild-type virus, although the concentration of the calanolides had to be increased.
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PMID:Anti-HIV-1 activity of calanolides used in combination with other mechanistically diverse inhibitors of HIV-1 replication. 1114 30

(+)-Calanolide A is a novel, naturally occurring, nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase first isolated from a tropical tree (Calophyllum lanigerum) in the Malaysian rain forest. Previous studies have demonstrated that (+)-calanolide A has specific activity against the reverse transcriptase of HIV-1 and a favorable safety profile in animals. In addition, (+)-calanolide A exhibits a unique HIV-1 resistance profile in vitro. The safety and pharmacokinetics of (+)-calanolide A was examined in four successive single-dose cohorts (200, 400, 600, and 800 mg) in healthy, HIV-negative volunteers. In this initial phase I study, the toxicity of (+)-calanolide A was minimal in the 47 subjects treated. Dizziness, taste perversion, headache, eructation, and nausea were the most frequently reported adverse events. These events were not all judged to be related to study medication nor were they dose related. While 51% of subjects reported mild and transient dizziness, in many cases this appeared to be temporally related to phlebotomy. Calculation of the terminal-phase half-life (t(1/2)) was precluded by intrasubject variability in the 200-, 400-, and 600-mg dose cohorts but was approximately 20 h for the 800-mg dose group. (+)-Calanolide A was rapidly absorbed following administration, with time to maximum concentration of drug in plasma (T(max)) values occurring between 2.4 and 5.2 h postdosing depending on the dose. Plasma levels of (+)-calanolide A at all dosing levels were quite variable; however, both the mean concentration in plasma (C(max)), and the area under the plasma concentration-time curve increased proportionately in relation to the dose. Although raw plasma drug levels were higher in women than in men, when doses were normalized for body mass, the pharmacokinetic profiles were virtually identical with those observed for males. In general, levels of (+)-calanolide A in human plasma were higher than would have been predicted from animal studies, yet the safety profile remained benign. In conclusion, this study demonstrated the safety and favorable pharmacokinetic profile of single doses of (+)-calanolide A in healthy, HIV-negative individuals.
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PMID:Safety and pharmacokinetics of single doses of (+)-calanolide a, a novel, naturally occurring nonnucleoside reverse transcriptase inhibitor, in healthy, human immunodeficiency virus-negative human subjects. 1130 99

A new generation of protease inhibitors is entering studies. Abbott Lab's ABT-378 and Pharmacia/Upjohn's PNU-140690 are beginning clinical studies and both are designed to overcome resistance problems. Several companies are developing new compounds to inhibit reverse transcriptase, such as Bristol-Myers Squibb's lobucavir and Hoechst/Bayer's HBY097. Calanolide A, which will soon begin trials, has a different resistance pattern than other non-nucleoside reverse transcriptase inhibitors, which may be an important advantage. Several groups are developing compounds to inhibit the HIV zinc finger, such as Parke-Davis' compound, CI-1012; and a Dutch company who is developing Azodicarbonamide, a drug currently in phase I/II trials for people with advanced disease in Europe. HIV drugs to date have not been successful in blocking viral fusion. However, three new fusion inhibitors are showing promise within the laboratory: Pentafuside (currently in phase I trials), Fuji ImmunoPharmaceuticals' FP-21399 (currently in phase I trials), and ISIS Pharmaceuticals' ISIS 5320. A new class of drugs known as integrase inhibitors has been of interest to pharmaceutical companies for the past several years; only one drug, Aronex Pharmaceuticals' Zintevir, has reached phase I/II trials.
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PMID:Protease inhibitors and beyond. 1136 10

Naturally occurring anti-HIV-1 agent (+)-calanolide A was found to be active against all of the strains of Mycobacterium tuberculosis tested, including those resistant to the standard antitubercular drugs. Efficacy evaluations in macrophages revealed that (+)-calanolide A significantly inhibited intracellular replication of M. tuberculosis H37Rv at concentrations below the MIC observed in vitro. Preliminary mechanistic studies indicated that (+)-calanolide A rapidly inhibits RNA and DNA synthesis followed by an inhibition of protein synthesis. Compared with known inhibitors, this scenario is more similar to effects observed with rifampin, an inhibitor of RNA synthesis. Since (+)-calanolide A was active against a rifampin-resistant strain, it is believed that these two agents may involve different targets. (+)-Calanolide A and its related pyranocoumarins are the first class of compounds identified to possess antimycobacterial and antiretroviral activities, representing a new pharmacophore for anti-TB activity.
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PMID:Anti-HIV natural product (+)-calanolide A is active against both drug-susceptible and drug-resistant strains of Mycobacterium tuberculosis. 1498 Jun 31

The coumarins represent a unique class of non-nucleoside reverse transcriptase inhibitors (NNRTIs) that were isolated from tropical plants. (+)-Calanolide A, the most potent compound of this class, selects for the T139I resistance mutation in HIV-1 reverse transcriptase (RT). Seven RTs mutated at amino acid position 139 (Ala, Lys, Tyr, Asp, Ile, Ser, and Gln) were constructed by site-directed mutagenesis. The mutant T139Q enzyme retained full catalytic activity compared with wild-type RT, whereas the mutant T139I, T139S, and T139A RTs retained only 85 to 50% of the activity. Mutant T139K, T139D, and T139Y RTs had seriously impaired catalytic activities. The mutations in the T139I and T139D RTs were shown to destabilize the RT heterodimer. (+)-Calanolide A lost inhibitory activity (up to 20-fold) against the mutant T139Y, T139Q, T139K, and T139I enzymes. All of the mutant enzymes retained marked susceptibility toward the other NNRTIs, including nevirapine, delavirdine, efavirenz, thiocarboxanilide UC-781, quinoxaline GW867420X, TSAO [[2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)] derivatives, and the nucleoside inhibitor, ddGTP. The fact that the T139I RT 1) proved to be resistant to (+)-calanolide A, 2) represents a catalytically efficient enzyme, and 3) requires only a single transition point mutation (ACA-->ATA) in codon 139 seems to explain why mutant T139I RT virus strains, but not virus strains containing other amino acid changes at this position, predominantly emerge in cell cultures under (+)-calanolide A pressure.
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PMID:The role of Thr139 in the human immunodeficiency virus type 1 reverse transcriptase sensitivity to (+)-calanolide A. 1596 74

(+)-Calanolide A ( 1) as a natural product was previously found as an inhibitor of HIV-1 reverse transcriptase. In our further investigation of its template, racemic 11-demethyl-12-oxo calanolide A ( 15), which had two fewer chiral carbon centers at the C-11 and C-12 positions than (+)-calanolide A, had a comparably inhibitory activity and better therapeutic index (EC 50 = 0.11 microM, TI = 818) against HIV-1 in vitro. A library based on its structural core was then designed and synthesized with introduction of nine diversity points in this article. The evaluations of anti-HIV-1 activity in vitro concluded their structure-activity relationships (SARs). A novel compound (10-bromomethyl-11-demethyl-12-oxo calanolide A, 123) was identified to have much higher inhibitory potency and therapeutic index (EC 50 = 2.85 nM, TI > 10,526) than those of the class compound against HIV-1. This finding provided a very important clue that modifications of the C ring at the C-10 position may be conducted to obtain drug candidates with better activity against HIV-1.
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PMID:Chemical library and structure-activity relationships of 11-demethyl-12-oxo calanolide A analogues as anti-HIV-1 agents. 1828 87


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