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PubMed2004

Determination of iron absorption from intrinsically labeled microencapsulated ferrous fumarate (sprinkles) in infants with different iron and hematologic status by using a dual-stable-isotope method.

BACKGROUND: The use of microencapsulated ferrous fumarate sprinkles is a new approach for home fortification. Iron and hematologic status may affect the absorption of iron from sprinkles. OBJECTIVE: The objective was to measure the absorption (corrected erythrocyte incorporation of (57)Fe) of 2 different doses of iron from sprinkles added to a maize-based complementary food provided to infants with different iron and hematologic status. DESIGN: Infants aged 6-18 mo were randomly assigned to receive either 30 (n = 45) or 45 (n = 45) mg elemental Fe as (57)Fe-labeled sprinkles added to a maize-based porridge on 3 consecutive days. A (58)Fe tracer (0.2 mg as ferrous citrate) was also infused intravenously (n = 46). Blood was drawn at baseline and 14 d later to determine erythrocyte incorporation of (57)Fe and (58)Fe by using inductively coupled plasma mass spectrometry. On the basis of hemoglobin and soluble transferrin receptor concentrations, subjects were classified as having iron deficiency anemia (IDA), iron deficiency (ID), or sufficient iron status. RESULTS: There was no significant effect of dose on iron absorption (P > 0.05). Geometric mean iron absorption was 8.25% (range: 2.9-17.8%) in infants with IDA (n = 32), 4.48% (range: 1.1-10.6%) in infants with ID (n = 20), and 4.65% (range: 1.5-12.3%) in iron-sufficient infants (n = 20). Geometric mean iron absorption was significantly higher in infants with IDA than in infants with ID or iron-sufficient infants (P = 0.0004); however, there were no significant differences between infants with ID and iron-sufficient infants. CONCLUSION: During infancy, iron absorption from sprinkles in a maize-based porridge meets and surpasses requirements for absorbed iron and is up-regulated in infants with IDA.

Absorption↗
PubMed2005

Long-term renal safety of tenofovir disoproxil fumarate in antiretroviral-naive HIV-1-infected patients. Data from a double-blind randomized active-controlled multicentre study.

BACKGROUND: Tenofovir disoproxil fumarate (TDF) was developed for the treatment of human immunodeficiency virus (HIV) infection. However, controlled data are sparse on the long-term renal tolerability of TDF at the currently approved daily dose of 300 mg in treatment-naive HIV-infected patients. METHODS: Over 144 weeks, this 600 patient, multicentre randomized, placebo-controlled, double-blind trial compared stavudine (301 patients) and TDF (299 patients), both administered in combination with lamivudine and efavirenz, in antiretroviral-naive patients. TDF or placebo and stavudine or placebo were administered in an open-label fashion. All medications were taken orally. At screening, all patients had serum creatinines <1.5 mg/dl, calculated creatinine clearances > or =60 ml/min and a serum phosphorus > or =2.2 mg/dl. RESULTS: The incidences of grades 1 (> or =0.5 mg/dl increase from baseline), 2 (2.1-3.0 mg/dl) and 3 (3.1-6.0 mg/dl) serum creatinine elevations at week 144 were 4, <1 and 0%, respectively, in the TDF group and 2, 0 and <1% in the stavudine control group (P = NS). There were no grade 4 (>6 mg/dl) serum creatinine elevations. At week 144, there was no change from baseline in the mean (0.83 mg/dl) serum creatinine in the TDF group compared with a 0.1 mg/dl decrease from baseline (0.83 mg/dl) in the stavudine control group. The incidences of grades 1 (2.0-2.2 mg/dl), 2 (1.5-1.9 mg/dl) and 3 (1.0-1.4 mg/dl) hypophosphataemia at week 144 were 4, 3 and <1%, respectively, in the TDF group and 4, 2 and <1% in the control group (P = NS). No patient experienced grade 4 (<1.0 mg/dl) hypophosphataemia. At week 144, the decrease (Delta) of mean serum phosphorus levels from baseline in both groups was similar (Delta 0.2 from 3.6 mg/dl for the TDF group, and 0.1 from 3.5 mg/dl for the stavudine control group). No patient developed Fanconi's syndrome or proximal renal tubular dysfunction during the study. CONCLUSION: Through 144 weeks, TDF and stavudine, each administered in combination with efavirenz and lamivudine, had similar renal safety profiles in treatment-naive HIV-infected patients with normal renal function at baseline.

Adenine↗
PubMed1985

Characterization of fumarate reductase from baker's yeast: essential sulfhydryl group for binding of FAD.

Fumarate reductase apoenzyme having the ability to reconstitute active enzyme was obtained by dialyzing the holoenzyme against 1 M KBr. The dissociation constant of the FAD-apoenzyme complex was 2.3 X 10(-8) M. The denatured holoenzyme and apoenzyme possessed seven sulfhydryl (SH) groups as determined with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). In the native apoenzyme, five SH-groups reacted with DTNB, and four of them were completely protected by the addition of FAD, while in the native holoenzyme, one was modified without inactivation. These results indicate that one SH-group is located on the surface of the enzyme molecule, four at or near the FAD-binding site, and two deeply embedded in the molecule. The modification of the apoenzyme caused inhibition of binding of FAD, resulting in loss of the ability to reconstitute enzymatic activity. Analyses of the data by statistical and kinetic methods suggested that a reactive SH-group is involved among the four SH-groups in the binding of FAD to the apoenzyme.

Apoenzymes↗
PubMed2003

Determining the antiviral activity of tenofovir disoproxil fumarate in treatment-naive chronically HIV-1-infected individuals.

OBJECTIVE: To assess the efficacy of tenofovir disoproxil fumarate (TDF) monotherapy by following the initial rate of decline in plasma viral load, which is a measure of the efficacy of therapy in blocking viral replication. DESIGN: An open-label, single-site study of TDF monotherapy in 10 antiretroviral drug-naive chronically HIV-1-infected individuals. METHODS: Antiviral responses were assessed at baseline and during 21 days of monotherapy with TDF by measuring plasma HIV-1 RNA levels. The rate of change in HIV-1 RNA from baseline was determined both by linear regression and by fitting to a published model. Slopes were compared with those previously determined for ritonavir monotherapy. RESULTS: Over 21 days, mean plasma HIV-1 RNA levels in the TDF-treated patients fell 1.5 log(10) copies/ml (range, 0.7-2.0). The initial rates of decline in plasma HIV-1 RNA in the 10 TDF-treated patients and in 25 protease inhibitor-naive subjects treated with ritonavir monotherapy were nearly identical. CONCLUSIONS: The reduction in plasma HIV-1 RNA with TDF monotherapy was comparable with the decline observed in previous studies of protease inhibitor monotherapy. TDF is a potent antiretroviral agent and has comparable inherent antiviral activity with that of ritonavir, a potent protease inhibitor. These data support further study of TDF-based regimens in simplified combinations of antiviral agents as initial treatment for chronic HIV-1 infection.

Adenine↗
PubMed1995

Effects of semotiadil fumarate (SD-3211) and its enantiomer, SD-3212, on the changes in cytosolic Ca2+ and tension caused by KCl and norepinephrine in isolated rat aortas.

Semotiadil fumarate (SD-3211), a Ca2+ channel blocker of benzothiazine derivative and its (S)-(-)-enantiomer (SD-3212), inhibited K(+)- and norepinephrine (NE)-induced contractions in isolated rat aortas. Inhibition of NE contraction induced by both drugs was greater than that induced by diltiazem or bepridil, whereas inhibition of K(+)-contraction was similar to that induced by diltiazem or bepridil. Semotiadil and SD-3212 (10 microM) inhibited the increase in cytosolic Ca2+ ([Ca2+]i) induced by 65.4 mM K+ in fura-2-loaded preparations as well as diltiazem and bepridil (10 microM). On the other hand, semotiadil and SD-3212 (10 microM) inhibited only the early phase of increase in [Ca2+]i induced by 1 microM NE. After 5 min, no significant effect on [Ca2+]i was observed with these compounds despite the significant decrease in the contraction. In contrast to these compounds, diltiazem and bepridil 10 microM affected neither the increase in [Ca2+]i nor the contraction induced by NE. Semotiadil and SD-3212 inhibited the transient contraction induced by 1 microM NE in the absence of external Ca2+. Both compounds partially but significantly inhibited the NE-induced contraction in nifedipine-treated muscles. These results suggest that semotiadil and SD-3212 inhibit contractions of vascular smooth muscle (VSM) not only through blockade of voltage-dependent Ca2+ channels but also through other mechanisms, such as inhibition of Ca2+ release from Ca2+ stores or decrease in sensitivity of the contractile elements to Ca2+.

Animals↗
PubMed2001

Hydroxyurea does not enhance the anti-HIV activity of low-dose tenofovir disoproxil fumarate.

Tenofovir disoproxil fumarate (DF) is an adenosine analogue with significant activity against HIV-1. Hydroxyurea decreases the intracellular concentrations of deoxyadenosine triphosphate, the active metabolite of adenosine. We therefore tested the hypothesis that hydroxyurea could enhance the anti-HIV activity of low-dose tenofovir in vivo. Eight patients received tenofovir DF, 75 mg, plus hydroxyurea, 500 mg bid, for 28 days. Changes in plasma HIV RNA levels were compared with a previously studied cohort of patients treated with tenofovir DF, 75 mg once daily ( n = 8), or tenofovir placebo ( n = 12). The median change in HIV RNA levels after 28 days of continuous treatment was -0.01 log(10) copies/ml for tenofovir placebo, -0.33 log(10) copies/ml for tenofovir 75 mg once daily, and -0.22 log(10) copies RNA/ml for tenofovir plus hydroxyurea. The difference between placebo and tenofovir-treated groups was significant ( p <.05); however, the difference between the tenofovir and tenofovir plus hydroxyurea groups was not significant ( p =.90). We conclude that hydroxyurea does not significantly enhance the antiviral activity of low-dose tenofovir.

Adenine↗
PubMed2003

Extended treatment with tenofovir disoproxil fumarate in treatment-experienced HIV-1-infected patients: genotypic, phenotypic, and rebound analyses.

OBJECTIVE: To study the potential development of genotypic and phenotypic resistance to tenofovir disoproxil fumarate (tenofovir DF) when used as a part of a 96-week HIV-1 treatment regimen for antiretroviral treatment-experienced HIV-infected patients. DESIGN AND METHODS: Clinical trial GS-98-902 was a placebo-controlled, 48-week phase 2 study of three doses of tenofovir DF when added to stable antiretroviral therapy for 189 treatment-experienced HIV-infected patients (mean of 4.6 years of prior antiretroviral treatment; 94% had nucleoside reverse transcriptase [RT] inhibitor [NRTI]-associated mutations). There was a statistically significant reduction in the mean HIV-1 RNA level at week 24 (average change in HIV-1 RNA level of -0.58 log(10) through week 24) with 300 mg of tenofovir DF once daily that was durable through week 48 (average change in HIV-1 RNA level of -0.62 log(10) through week 48). At week 48, 135 patients enrolled in an open-label, 48-week extension phase with 300 mg of tenofovir DF once daily added to their antiretroviral therapy. Genotypic analysis of plasma HIV-1 was performed for all patients after 96 weeks of study or upon early termination. Phenotypic analyses were performed at week 96 for patients with increases in HIV-1 RNA levels of > or =0.5 log(10) from week 48 to week 96. RESULTS: Genotypic results were obtained for 96 of 135 patients. NRTI-associated mutations developed in 41 (30%) of 135 patients from week 48 to week 96. Those mutations were primarily thymidine analog-associated mutations (33/41 patients) and developed while patients were receiving either stavudine or zidovudine. Two patients (1.5%) developed the K65R RT mutation (selected by tenofovir in vitro) but maintained HIV-1 suppression (-0.39 log(10)). These 96-week results were analogous to the 48-week results, in which 33% (n = 63) and 2.1% (n = 4) of patients developed thymidine analog-associated mutations or the K65R mutation, respectively. Although most patients maintained HIV-1 RNA suppression, an analysis of patients with increases in HIV-1 RNA levels of > or =0.5 log(10) (n = 21) from week 48 to week 96 was performed. For eight of 21 patients, development of primary protease inhibitor-associated or non-NRTI-associated resistance mutations was likely responsible for the HIV-1 RNA rebound. The remaining patients developed either no mutation (n = 3) or a new NRTI-associated mutation (n = 10) and were analyzed phenotypically. No phenotypic changes for tenofovir were observed in these analyses. In addition, no new mutations potentially associated with tenofovir DF therapy were identified. Overall, patients had a similar reduction in HIV-1 RNA levels at week 96 and at week 48 compared with baseline (-0.55 and -0.60 log(10), respectively). CONCLUSIONS: Adding tenofovir DF (300 mg) to existing antiretroviral therapy for highly treatment-experienced patients with preexisting resistance mutations showed significant and durable reductions in HIV-1 RNA levels through week 96. Through 96 weeks of tenofovir DF therapy, 48 weeks of which included suboptimal doses of tenofovir DF, there was infrequent development of RT mutations associated with tenofovir DF therapy (K65R mutation, 3%), consistent with the durability of the observed HIV-1 RNA responses.

Adenine↗
PubMed2004

Patterns of resistance emerging in HIV-1 from antiretroviral-experienced patients undergoing intensification therapy with tenofovir disoproxil fumarate.

Study GS-99-907 was a 48-week, phase 3, double-blind, placebo-controlled intensification trial of tenofovir disoproxil fumarate (tenofovir DF). Antiretroviral-experienced patients added tenofovir DF 300 mg once daily to their existing regimen. The patterns of HIV-1 resistance development and the corresponding virologic responses were evaluated in a virology substudy at week 48. Although 94% of these treatment-experienced patients had nucleoside-associated resistance mutations (NAMs) at baseline, addition of tenofovir DF resulted in a mean reduction in viral load of -0.59 log10 copies/mL after 24 weeks that was durable through 48 weeks. Relative to the placebo-controlled arm, patients in the tenofovir DF arm had a reduced frequency of development of resistance mutations to all classes of HIV-1 inhibitors, with reduction in new protease inhibitor (PI)-associated mutations achieving statistical significance. The K65R mutation, which occurred in 8 patients (3%), was the only emergent mutation directly associated with tenofovir DF therapy. New thymidine analogue-associated mutations (TAMs) emerged in 19% of patients by week 48. Other than K65R, the patterns of mutations that developed were not significantly different between the tenofovir DF and placebo control arms, suggesting that the background therapies caused their development. The K65R mutation emerged only in patients with no detectable TAMs at baseline, whereas new TAMs developed similarly between patients with or without TAMs at baseline. Development of K65R was associated with mostly low-level changes in phenotypic susceptibility to tenofovir DF and other nucleoside reverse transcriptase inhibitors and was not associated with viral load rebound. No novel patterns of genotypic or phenotypic resistance to tenofovir were identified. Therefore, intensification with once-daily tenofovir DF therapy resulted in a sustained reduction in HIV-1 viral load and a low risk for development of the K65R mutation in this treatment-experienced patient population.

Acquired Immunodeficiency Syndrome↗
PubMed2005

Long-term hepatitis B virus dynamics in HIV-hepatitis B virus-co-infected patients treated with tenofovir disoproxil fumarate.

BACKGROUND: The long-term impact of tenofovir disoproxil fumarate (TDF) on hepatitis B virus (HBV) replication has not yet been studied in HIV-HBV-co-infected patients. METHODS: We conducted a prospective study of HBV-DNA decay kinetics in 28 HIV-HBV-co-infected patients treated by TDF. HBV dynamics were studied using mixed linear models, and baseline factors affecting them were analysed using Cox models. RESULTS: The HBV-DNA load declined by a mean of 4.6 log copies/ml during follow-up (mean 71 weeks), and fell below the detection limit (200 copies/ml) in 21 patients. Inhibition of viral replication by TDF was associated with a decrease in alanine aminotransferase levels (125 versus 68 IU, P < 0.05). HBV-DNA decay was biphasic, with an rapid fall followed by a gradual decline. Baseline factors associated with a steeper first slope in the HBV-DNA decrease were high HBV load, positive hepatitis B e antigen (HBeAg) and YMDD mutations. Baseline factors increasing the time to reach an HBV-DNA level less than 200 copies/ml were high HBV load (150 days when HBV-DNA < 10 log, 316 days when HBV-DNA > 10 log) and positive HBeAg. Previous exposure to lamivudine or TDF-lamivudine did not modify HBV-DNA decrease under therapy in this population with a high prevalence of YMDD mutations. CONCLUSION: The long-term decline in HBV DNA under TDF is biphasic and is primarily influenced by the initial HBV load. However, the clinical significance of such an association remains moderate, and TDF can be efficiently included in the highly active antiretroviral therapy regimen of HIV-HBV-co-infected patients, regardless of HBV strains and their degree of replication.

Adenine↗
PubMed2004

Renal dysfunction with tenofovir disoproxil fumarate-containing highly active antiretroviral therapy regimens is not observed more frequently: a cohort and case-control study.

BACKGROUND: Tenofovir disoproxil fumarate (tenofovir DF), the first nucleotide analogue reverse transcriptase inhibitor approved for the treatment of HIV infection, has been associated with renal dysfunction in isolated cases. We investigated the overall incidence and risk of renal dysfunction in individuals receiving tenofovir DF and compared this with other antiretrovirals. METHODS: Data from the Chelsea and Westminster cohort were analyzed to reveal HIV-positive individuals with a creatinine value greater than 120 micromol/L at any time, the upper limit of normal used by our reference laboratory. These individuals were classified according to antiretroviral exposure and time exposed. A matched case-control study was performed comparing patients who had received tenofovir DF and subsequently developed a creatinine value greater than 120 micromol/L against controls who had been treated with tenofovir DF and had not experienced a creatinine elevation. RESULTS: Of 4183 HIV-positive patients, 1175 were identified as having a recorded creatinine value >120 micromol/L. Comparison of antiretroviral-naive patients and patients exposed to tenofovir DF- and non-tenofovir DF-containing regimens revealed a lower rate ratio and probability of developing a creatinine value >120 micromol/L in patients exposed to tenofovir DF (rate ratio vs. no antiretrovirals = 0.22, 95% confidence interval [CI]: 0.07-0.69; P < 0.001) with no significant difference between HAART regimens, corrected for duration of exposure. Of the 1058 individuals who were exposed to tenofovir DF, 84 (8%) patients experienced a creatinine value >120 micromol/L subsequent to exposure. An alternative etiology of renal dysfunction was found in 75 (90%) of these individuals. CONCLUSIONS: Tenofovir DF is not associated with renal dysfunction more frequently than other antiretroviral drugs, and the occurrence of renal dysfunction in this context is usually attributable to other causes.

Adenine↗
PubMed2006

Assessment of drug-drug interactions between tenofovir disoproxil fumarate and the nonnucleoside reverse transcriptase inhibitors nevirapine and efavirenz in HIV-infected patients.

BACKGROUND: Tenofovir disoproxil fumarate (DF) has been studied in combination with efavirenz in healthy volunteers and no interaction was found. No data are available on the possible interaction of tenofovir DF with nevirapine and efavirenz in HIV-infected patients. In this study the combination of nevirapine 200 mg twice daily with tenofovir DF 300 mg once daily and nevirapine 400 mg once daily with tenofovir DF 300 mg once daily were compared with nevirapine twice daily or once daily without tenofovir DF in HIV-infected patients. Furthermore, the combination of efavirenz 600 mg and tenofovir DF 300 mg once daily was compared with use of efavirenz 600 mg once daily only. METHODS: Data were retrospectively collected from routine therapeutic drug monitoring plasma samples. Nevirapine, efavirenz, and tenofovir plasma levels and tenofovir concentration ratios were analyzed. The concentration ratio represents the measured plasma concentration compared with the time-adjusted average concentration, as measured in a reference population. Six different groups were studied: 200 mg nevirapine twice daily, 400 mg nevirapine once daily, 600 mg efavirenz once daily, all without tenofovir DF (groups 1, 2, and 3, respectively), and the same groups with the drugs combined with tenofovir 300 mg once daily (groups 4, 5, and 6, respectively). RESULTS: Plasma samples were evaluable for 272, 18, 126, 32, 94, and 118 patients in the groups 1-6, respectively. No differences were found in plasma levels for tenofovir, nevirapine, and efavirenz for either of the combinations studied. Addition of tenofovir DF to efavirenz or nevirapine in HIV-infected patients does not influence the plasma levels of nevirapine or efavirenz. Furthermore, nevirapine and efavirenz have no effect on tenofovir plasma levels or tenofovir concentration ratios. CONCLUSION: Efavirenz or nevirapine can be coadministered with tenofovir DF in HIV-infected patients without dose modifications.

Adenine↗
PubMed2006

Evaluation of oral tenofovir disoproxil fumarate and topical tenofovir GS-7340 to protect infant macaques against repeated oral challenges with virulent simian immunodeficiency virus.

Simian immunodeficiency virus (SIV) infection of infant macaques is a useful animal model of pediatric HIV infection to evaluate the potential of chemoprophylactic regimens to reduce mother-to-infant transmission of HIV. Previous studies have demonstrated that short-term subcutaneous administration of the reverse transcriptase inhibitor tenofovir was highly effective in protecting newborn macaques against infection after a single high-dose oral inoculation with virulent SIVmac251. In the current study, we mimicked HIV transmission through breast-feeding by repeatedly feeding infant macaques low doses of SIVmac251. Topical administration of a low dose of the second-generation tenofovir prodrug GS-7340 did not have detectable prophylactic efficacy. Oral administration of tenofovir disoproxil fumarate (DF; 10 mg/kg SID) lowered the infection rate at birth, but had lower efficacy against virus infection at 4 weeks of age, most likely because drug levels became suboptimal relative to those obtained with the current tenofovir DF regimen in humans. These prophylactic results further underscore the relevance of the current tenofovir DF prevention trials in pediatric and adult populations.

Adenine↗
PubMed2006

Pharmacokinetics and safety of tenofovir disoproxil fumarate on coadministration with lopinavir/ritonavir.

OBJECTIVE: Lopinavir/ritonavir (LPV/r) and tenofovir disoproxil fumarate (TDF) are frequently used antiretrovirals. A pharmacokinetic study in healthy volunteers was conducted to assess the potential for a drug interaction between these agents. METHODS: This was a 36-day, multiple-dose, drug-drug interaction study of TDF and lopinavir/ritonavir (LPV/r). Subjects received TDF alone for 7 days, followed by 14 days each of TDF plus LPV/r and LPV/r alone in a randomized manner. Pharmacokinetic assessments were performed over 24 hours on days 7, 21, and 35. LPV/r and tenofovir plasma/serum concentrations were measured by high-performance liquid chromatography/mass spectometry (MS)/MS. Geometric mean ratios and 90% confidence intervals of pharmacokinetic parameters for tenofovir, LPV, and ritonavir (RTV) were estimated using analysis of variance and compared with the no-effect criterion for pharmacokinetic equivalence. RESULTS: Tenofovir measurements with an area under the concentration-time curve over the dosing interval, maximum concentration, and concentration at the end of the dosing interval (Ctau) were 32%, 15%, and 51% higher, respectively, when TDF was coadministered with LPV/r (n = 24). LPV and RTV pharmacokinetics, including Ctau, were unaffected by TDF (n = 24). Clinical estimates of renal function were unaffected by administration of TDF alone or with LPV/r. DISCUSSION: Coadministration of TDF with LPV/r resulted in increased tenofovir exposures at steady state, possibly through increased absorption. This increase is not believed to be clinically relevant based on the safety and efficacy of TDF plus LPV/r-containing regimens in HIV-infected patients in long-term controlled clinical trials.

Adenine↗
PubMed2006

Virologic response of zidovudine, lamivudine, and tenofovir disoproxil fumarate combination in antiretroviral-naive HIV-1-infected patients.

BACKGROUND: High rates of virologic failure have been reported in antiretroviral-naive patients receiving triple-nucleoside reverse transcriptase inhibitor (NRTI) combinations containing tenofovir disoproxil fumarate (TDF) with lamivudine (3TC) and didanosine or 3TC and abacavir (ABC). A regimen of once-daily zidovudine (ZDV), 3TC, ABC, and TDF showed an acceptable virologic success rate, however. METHODS: This was a pilot prospective cohort study. Treatment-naive subjects were offered a fixed-dose combination of ZDV/3TC (300 mg/150 mg) twice daily and 300 mg of TDF once daily. RESULTS: Fifty-one patients were enrolled between April 2002 and March 2005. At baseline, the median CD4 count was 230 cells/microL (range: 23-425 cells/microL), 20 (39%) of 51 subjects had CD4 counts of < 200 cells/microL, the median HIV-1 viral load was 4.89 log (3.14 to >5.87 log), and 24 (47%) of 51 subjects had a viral load >5 log. The median follow-up was 12 months (range: 1 week to 38 months). On-treatment analysis showed a median HIV RNA load decrease of -1.7 log after 1 to 2 weeks of treatment and -2.41 log after 1 month, and 34 (89%) of 38 subjects had a viral load < 50 copies/mL at month 6, 21 (78%) of 27 at month 12, and 13 (81%) of 16 after 18 months (intent-to-treat results were 34 [72%] of 47 subjects, 21 [56%] of 36 subjects, and 13 [50%] of 25 subjects at months 6, 12, and 18, respectively). The median CD4 count increase at month 18 was 142 cells/microL. Nine (17.6%) of 51 treatment interruptions for adverse effects were seen. Six viral failures occurred, including 2 with K65R mutations (alone or associated with Y115F and M184V). CONCLUSION: The combination of ZDV/3TC + TDF in treatment-naive HIV-infected subjects induces a rapid and sustained HIV-1 RNA decrease and is associated with a good immunologic response. No severe adverse events occurred. This triple-NRTI combination needs to be evaluated further.

Adenine↗
PubMed2006

Tenofovir disoproxil fumarate, emtricitabine, and efavirenz versus fixed-dose zidovudine/lamivudine and efavirenz in antiretroviral-naive patients: virologic, immunologic, and morphologic changes--a 96-week analysis.

BACKGROUND: In antiretroviral-naive patients, tenofovir disoproxil fumarate (TDF), emtricitabine (FTC), and efavirenz (EFV) demonstrated superior outcomes compared with fixed-dose zidovudine (ZDV)/lamivudine (3TC) and EFV through 48 weeks. Results through a 96-week extension phase are presented. METHODS: In this randomized, open-label, noninferiority trial, 517 antiretroviral-naive HIV-infected patients received TDF, FTC, and EFV (TDF + FTC + EFV) or ZDV/3TC and EFV (ZDV/3TC + EFV). The primary endpoint was the proportion of patients with an HIV RNA level <400 copies/mL in patients without baseline nonnucleoside resistance. RESULTS: Through week 96, significantly more patients receiving TDF + FTC + EFV achieved and maintained an HIV RNA level <400 copies/mL (75% receiving TDF + FTC + EFV vs. 62% receiving ZDV/3TC + EFV; P = 0.004). There was a trend toward greater virologic suppression to <50 copies/mL in the TDF + FTC + EFV group (67% vs. 61%; P = 0.16). The TDF + FTC + EFV group demonstrated a significantly greater increase in CD4 count (270 vs. 237 cells/mm; P = 0.036). No patient developed the K65R mutation. Limb fat at week 96 was significantly greater in the TDF + FTC + EFV group versus the ZDV/3TC + EFV group (7.7 vs. 5.5 kg; P < 0.001). CONCLUSION: Over 96 weeks, the combination of TDF, FTC, and EFV was superior to fixed-dose ZDV/3TC + EFV for achieving and maintaining an HIV RNA level <400 copies/mL and an increase in CD4 cells.

Adenine↗
PubMed1982

Location and nucleotide sequence of frdB, the gene coding for the iron-sulphur protein subunit of the fumarate reductase of Escherichia coli.

The frdB gene, encoding the iron-sulphur protein subunit of fumarate reductase, has been located and its complete nucleotide sequence determined. The identity of the gene was confirmed by protein chemical studies and determination of the NH2-terminal sequence of the FrdB protein. The frdB gene is situated distal to and partially overlapped by frdA which codes for the flavoprotein subunit of the reductase. Its reading frame contains 244 codons and predicts a protein of Mr 27092. In composition, the FrdB protein is strikingly similar to the corresponding subunit of the related flavoenzyme, succinate dehydrogenase. Analysis of the protein's primary structure revealed several features characteristic of iron-sulphur proteins.

Base Sequence↗
PubMed1990

Bovine hemoglobin pseudo-crosslinked with mono(3,5-dibromosalicyl)-fumarate.

Under oxygenated conditions bovine hemoglobin reacts with mono(3,5-dibromosalicyl)-fumarate which specifically acylates the EF5 lysines in the beta-cleft of the protein. The chemical modification introduces in the molecule a pseudo-crosslink which hinders the dissociation of the hemoglobin molecule into dimers. Retention time in circulation of the chemically modified bovine hemoglobin, measured in the rat, is increased fivefold with respect to untreated bovine hemoglobin. The oxygen affinity at 37 degrees C and at pH 7.4, has a P50 = 5.4 kPa and a value of n = 1.9. Under the same experimental conditions the oxygen affinity is not sensitive to anions and polyanions whereas it is sensitive to CO2. The Bohr effect is shifted toward the alkaline pH range by 0.5-1: the maximum number of protons released is 1.5/tetramer, similar to normal bovine hemoglobin (1.8 protons/tetramer). Analysis of the binding isotherms, using the two-state Monod-Wyman-Changeux model and fixing the value of the allosteric constant L = 10(5), shows that the oxygen affinity of the T structure is not modified, and that the low oxygen affinity of the system is due to a decrease of the oxygen affinity of the R structure. Analysis using the sequential Adair model shows a modification of the overall binding constants and suggests a redistribution of the intermediate species of oxygenation.

Animals↗
PubMed2006

Minor changes in calculated creatinine clearance and anion-gap are associated with tenofovir disoproxil fumarate-containing highly active antiretroviral therapy.

BACKGROUND: Tenofovir disoproxil fumarate (Tenofovir DF, TDF), the first nucleotide reverse transcriptase inhibitor approved for the treatment of HIV disease, has been associated with renal dysfunction in isolated cases. The aim of this study was to assess changes in renal parameters in individuals receiving TDF- and non-TDF-containing highly active antiretroviral therapy (HAART). METHODS: All individuals on HAART attending our clinic were included in the analysis. Time-weighted changes in serum creatinine, calculated creatinine clearance (CCrCl) and anion-gap were assessed for individuals on TDF- and non-TDF HAART. RESULTS: Of 948 individuals on HAART, 290 (31%) and 618 (65%) were on TDF- and non-TDF HAART, with 40 (4%) having ceased TDF HAART. Baseline values for serum creatinine, CCrCl and anion-gap were similar for those on TDF- and non-TDF HAART. In a multivariate analysis, statistically significant differences were observed in time-weighted change from baseline in anion-gap and CCrCl between individuals on TDF- and non-TDF HAART [mean difference in change between groups: anion-gap 0.78 mmol/L (standard error, 0.19) and CCrCl-6.80 (standard error 2.2); P = 0.005 and P = 0.032, respectively] after adjusting for baseline anion-gap and CCrCl, respectively. Two cases of TDF-associated renal failure were observed. CONCLUSION: Overt renal failure with TDF HAART is rare. However, subtle but statistically significant changes in anion-gap and CCrCl were observed which were associated with TDF HAART. These parameters may be of use in monitoring individuals on HAART.

Acid-Base Equilibrium↗