Safety and tolerability of varenicline tartrate (Champix(®)/Chantix(®)) for smoking cessation in HIV-infected subjects: a pilot open-label study

The prevalence of smoking in HIV-infected subjects is high. As a smoking cessation aid, varenicline (Champix(®), Pfizer, Saint-Laurent, QC, Canada or Chantix(®), Pfizer, Mission, KS) has not been previously evaluated in HIV-infected smokers. In this multicenter pilot open label study, varenicline 1.0 mg was used twice daily for 12 weeks with dose titration in the first week. Adverse events (AEs) during the treatment period were recorded. Changes from baseline in laboratory tests, vital signs, daily cigarette consumption, nicotine dependence, and withdrawal were measured through week 24. Self-reported abstinence was validated by serum cotinine at week 12. We enrolled 36 subjects with a mean of 29 pack-years of smoking and a minimum of 4 cigarettes per day. All but 1 were male, 33 (92%) were white. The most frequently reported AEs were nausea (33%), abnormal dreams (31%), affect lability (19%), and insomnia (19%). Six (17%) subjects discontinued varenicline due to AEs. No grade 3/4 laboratory abnormalities or serious AEs occurred during the study. There was no significant change in HIV viral load. CD4 counts increased by 69 cells/mm3 (p = 0.001) at week 24. Serum cotinine-verified 4-week continuous abstinence rate through weeks 9-12 was 42% (95% confidence interval [CI]: 26-58%). AEs and abstinence rates were comparable to those in published randomized controlled trials conducted in generally healthy HIV-negative smokers. Varenicline was safe and appears effective among HIV-infected smokers in this exploratory study, although AEs were common. The most common AE was nausea, with no adverse effect on HIV treatment outcome. Close monitoring of liver enzymes and blood pressure is recommended for HIV-positive smokers taking varenicline.

Utility of monitoring mycophenolic acid in solid organ transplant patients

OBJECTIVES

To investigate whether monitoring concentrations of mycophenolic acid (MPA) in the serum or plasma of persons who receive a solid organ transplant will result in a lower incidence of transplant rejections and adverse events versus no monitoring of MPA. To investigate whether the incidence of rejection or adverse events differs according to MPA dose or frequency, type of MPA, the form of MPA monitored, the method of MPA monitoring, or sample characteristics. To assess whether monitoring is cost-effective versus no monitoring.

DATA SOURCES

The following databases were searched from their dates of inception (in brackets) until October 2007: MEDLINE (1966); BIOSIS Previews (1976); EMBASE (1980); Cochrane Database of Systematic Reviews (1995); and Cochrane Central Register of Controlled Trials (1995).

REVIEW METHODS

Studies identified from the data sources went through two levels of screening (i.e., title and abstract, full text) and the ones that passed were abstracted. Criteria for abstraction included publication in the English language, study design (i.e., randomized controlled trial [RCT], observational study with comparison group, case series), and patient receipt of allograft solid organ transplant. Additionally, any form of MPA had to be measured at least once in the plasma or serum using any method of measurement (e.g., AUC0-12, C0). Furthermore, these measures had to be linked to a health outcome (e.g., transplant rejection). Certain biomarkers (e.g., serum creatinine, glomular filtration rate) and all adverse events were also considered health outcomes.

RESULTS

The published evidence on MPA monitoring is inconclusive. Direct, head-to-head comparison of monitoring versus no monitoring is limited to one RCT in adult, kidney transplant patients. Inferences about monitoring can be made from some observational studies, although the evidence is equivocal for MPA dose and dose frequency, nonexistent for type of MPA, inconclusive for form of MPA monitored or method of monitoring, and nonexistent for cost-effectiveness. Some studies suggest gender and concomitant use of calcineurin inhibitors will affect pharmacokinetic parameters, but the impact of these findings has not been assessed in relation to monitoring versus no monitoring.

CONCLUSIONS

The state of knowledge about therapeutic drug monitoring of MPA in solid organ transplants is still in its infancy. Until there is more evidence on the utility of routine MPA monitoring in solid organ transplant recipients, patients, clinicians, and other stakeholders (e.g., public and private insurers) will have to decide on a case by case basis whether the possible but uncertain benefits are worth the extra time and expense of monitoring.

Biosynthesis of Vitamin B1 in Yeast. Derivation of the Pyrimidine Unit from Pyridoxine and Histidine. Intermediacy of Urocanic Acid

Incorporation studies with 13C-, 15N-, and 2H-labeled substrates, followed by NMR analysis, show that the pyrimidine unit of thiamin (Vitamin B1) originates from a C5N fragment, derived from C-2',2,N,C-6,5,5' of pyridoxol (Vitamin B6) and an N-C-N fragment derived from L-histidine. Urocanic acid serves as an intermediate on the route of the N-C-N fragment of histidine into the thiamin pyrimidine.

Biosynthesis of Vitamin B(6) in yeast. Incorporation pattern of trioses

The biosynthetic origin of the C(3) unit, C-6,5,5', of pyridoxamine was investigated in two yeasts, Candida utilis ATCC 9256 and Saccharomyces cerevisiae ATCC 7752. The incorporation patterns within pyridoxamine bishydrochloride derived from variously multiply (13)C- and (2)H-labeled samples of glycerol and glyceraldehyde, established by NMR spectroscopy, indicate that the three-carbon unit C-6,5,5' of pyridoxamine is derived intact from a triose.

2'-hydroxypyridoxol, a biosynthetic precursor of vitamins B(6) and B(1) in yeast

In separate experiments cultures of the yeast Saccharomyces cerevisiae ATTC 7752 were grown in the presence of [5',5'-2H2]- or of [2',2',5',5'-2H4]-3-hydroxy-2,4,5-tri(hydroxymethyl)pyridine (i.e., 2'-hydroxypyridoxol). The 2H NMR spectra of the samples of pyridoxamine dihydrochloride and of thiamin chloride hydrochloride that were isolated from the two experiments showed the presence of deuterium at the corresponding sites. Entry of deuterium from the specifically 2H-labeled samples of 2'-hydroxypyridoxol into the predicted sites of pyridoxamine and of the pyrimidine unit of thiamin provides the first unequivocal evidence that, in yeast, 2'-hydroxypyridoxol is an intermediate on the route from a C5-sugar into vitamin B6, and adds to the evidence that pyridoxol serves as a precursor of the pyrimidine unit of thiamin, supplying the C5N unit, C-2',2,N-1,C-6,5,5' as an intact unit.

Fluorescent tricyclic analogues of acyclovir and ganciclovir. A structure-antiviral activity study

Of a series of new guanine base modified tricyclic analogues of acyclovir (ACV, 1) and ganciclovir (GCV, 2), derivatives of the 3,9-dihydro-9-oxo-5H-imidazo[1,2-a]purine system, evaluated for activity against herpes simplex virus type 1 and 2, several fluorescent analogues, 6-(4-MeOPh)-TACV (8), 7-Me-6-Ph-TACV (17), 6-(4-MeOPh)-TGCV (27), and 7-Me-6-Ph-TGCV (28), were obtained that showed similar potency and selectivity as the parent compounds. The activity was found to be strongly dependent on the nature and steric demands of the substituents in the 6 and/or 7 position.

Biosynthesis of 2-methyl-3-buten-2-ol emitted from needles of Pinus ponderosa via the non-mevalonate DOXP/MEP pathway of isoprenoid formation

The volatile hemiterpene 2-methyl-3-buten-2-ol (MBO) is emitted from the needles of several pine species from the Western United States and contributes to ozone formation in the atmosphere. It is synthesised enzymatically from dimethylallyl diphosphate (DMAPP). We show here that needles of Pinus ponderosa Laws. incorporated [1-2H1]-1-deoxy-D-xylulose (d-DOX) into the emitted MBO, but not D,L-[2-13C]mevalonic acid lactone. Furthermore, MBO emission was inhibited by fosmidomycin, a specific inhibitor of the second enzyme of the mevalonate-independent pathway of isopentenyl diphosphate and DMAPP formation, i.e. the 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) pathway. We thus prove that MBO emitted from needles of P. ponderosa is primarily formed via the DOXP/MEP pathway.

The non-mevalonate isoprenoid biosynthesis of plants as a test system for drugs against malaria and pathogenic bacteria

Two plant test systems are presented in the search for new inhibitors of the non-mevalonate isoprenoid pathway. A derivative of clomazone appears to be an inhibitor of the deoxyxylulose 5-phosphate/methylerythritol 4-phosphate (DOXP/MEP) pathway of isoprenoid formation.

Properties and inhibition of the first two enzymes of the non-mevalonate pathway of isoprenoid biosynthesis

Enzymes of the 1-deoxy-D-xylulose 5-phosphate/2-C-methylerythritol 4-phosphate (DOXP/MEP) pathway are targets for new herbicides and antibacterial drugs. Until now, no inhibitors for the DOXP synthase have been known of. We show that one of the breakdown products of the herbicide clomazone affects the DOXP synthase. One inhibitor of the non-mevalonate pathway, fosmidomycin, blocks the DOXP reductoisomerase (DXR) of plants and bacteria. The I(50) values of plants are, however, higher than those found for the DXR of Escherichia coli. The DXR of plants, isolated from barley seedlings, shows a pH optimum of 8.1, which is typical for enzymes active in the chloroplast stroma.

Substituent--directed aralkylation and alkylation reactions of the tricyclic analogues of acyclovir and guanosine

Aryl or tert-butyl substituent in the 6 position of 3,9-dihydro-3-[(2-hydroxyethoxy)methyl]-9-oxo-6-R-5H-imidazo[1,2-a]purine (6-R-TACV) 1 partly directs aralkylation reactions into unusual positions: N-4 to give 3 and C-7 to give N-5,7-disubstituted or N-4,7-disubstituted derivatives. In the case of alkylation the effect is limited to aryl substituent and position N-4. Replacement of acyclic moiety of 1 with a ribosyl one like in 7 prevents N-4 substitution. Cleavage of the third ring of 3b to give 3-benzylacyclovir 10 is an example of a new short route to 3-aralkyl-9-substituted guanines.

The non-mevalonate isoprenoid biosynthesis of plants as a test system for new herbicides and drugs against pathogenic bacteria and the malaria parasite

Higher plants and several photosynthetic algae contain the plastidic 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate pathway (DOXP/MEP pathway) for isoprenoid biosynthesis. The first four enzymes and their genes are known of this novel pathway. All of the ca. 10 enzymes of this isoprenoid pathway are potential targets for new classes of herbicides. Since the DOXP/MEP pathway also occurs in several pathogenic bacteria, such as Mycobacterium tuberculosis, and in the malaria parasite Plasmodium falciparum, all inhibitors and potential herbicides of the DOXP/MEP pathway in plants are also potential drugs against pathogenic bacteria and the malaria parasite. Plants with their easily to handle DOXP/MEP-pathway are thus very suitable test-systems also for new drugs against pathogenic bacteria and the malaria parasite as no particular security measures are required. In fact, the antibiotic herbicide fosmidomycin specifically inhibited not only the DOXP reductoisomerase in plants, but also that in bacteria and in the parasite P. falciparum, and cures malaria-infected mice. This is the first successful application of a herbicide of the novel isoprenoid pathway as a possible drug against malaria.

Inhibitors of the nonmevalonate pathway of isoprenoid biosynthesis as antimalarial drugs

A mevalonate-independent pathway of isoprenoid biosynthesis present in Plasmodium falciparum was shown to represent an effective target for chemotherapy of malaria. This pathway includes 1-deoxy-D-xylulose 5-phosphate (DOXP) as a key metabolite. The presence of two genes encoding the enzymes DOXP synthase and DOXP reductoisomerase suggests that isoprenoid biosynthesis in P. falciparum depends on the DOXP pathway. This pathway is probably located in the apicoplast. The recombinant P. falciparum DOXP reductoisomerase was inhibited by fosmidomycin and its derivative, FR-900098. Both drugs suppressed the in vitro growth of multidrug-resistant P. falciparum strains. After therapy with these drugs, mice infected with the rodent malaria parasite P. vinckei were cured.

Cloning and heterologous expression of a cDNA encoding 1-deoxy-D-xylulose-5-phosphate reductoisomerase of Arabidopsis thaliana

Various plant isoprenoids are synthesized via the non-mevalonate pathway of isopentenyl diphosphate formation. In this pathway, 1-deoxy-D-xylulose 5-phosphate (DOXP), the first intermediate, is transformed to 2-C-methyl-D-erythritol 4-phosphate (MEP) by an enzyme which was recently cloned from Escherichia coli. In order to find a plant homologue of this 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) we cloned a cDNA fragment from Arabidopsis thaliana which has high homology to the E. coli DXR. By expression of this fragment in E. coli we could demonstrate that it encodes a protein which transforms DOXP to MEP. The antibiotic fosmidomycin specifically inhibits this DXR enzyme activity.