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Biomedical subjects

Graeme Moyle

Publications and source records attributed to Graeme Moyle.

At least 37 records · Page 2Linked to original sources
PubMed2004

Intracellular and plasma pharmacokinetics of saquinavir-ritonavir, administered at 1,600/100 milligrams once daily in human immunodeficiency virus-infected patients.

Ritonavir-boosted saquinavir (SQV/r) is currently licensed as a twice-daily regimen. Reducing the pill burden with once-daily dosing may improve adherence. Intracellular concentrations of drugs must be related to the clinical efficacy of protease inhibitors. The aims of the study were to determine the cellular and plasma saquinavir and ritonavir concentrations, to determine the half-lives (t(1/2)s) of the drugs in each compartment, and to examine relationships between drug accumulation and lymphocyte subset P glycoprotein (P-gp) expression. Venous blood samples from 12 human immunodeficiency virus-infected patients receiving a hard-gel formulation of SQV/r (1,600/100 mg once daily) were collected at 2, 6, 12, and 24 h after dosing. Peripheral blood mononuclear cells were separated by density gradient centrifugation, and P-gp expression was measured by dual-color flow cytometry. Plasma and intracellular (cell-associated) drug concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. The ratio of the intracellular drug area under the concentration-time curve from 0 to 24 h (AUC(0-24 h)) to plasma drug AUC(0-24 h) was calculated to determine cellular drug accumulation. The median (range) AUC(0-24 h) of saquinavir in plasma was 16.2 (5.7 to 39.3) mg. h. liter(-1), and that in cells was 46.3 (24.7 to 114.6) mg. h. liter(-1). Corresponding ritonavir values were 7.5 (1.5 to 14.6) mg. h. liter(-1) and 10.4 (3.2 to 13.7) mg. h. liter(-1), respectively. The median accumulation ratios of cellular AUC to plasma AUC for saquinavir and ritonavir were 3.31 (range, 1.49 to 6.69) and 1.46 (range, 0.83 to 4.15), respectively. Significant differences between the plasma and intracellular saquinavir t(1/2)s (4.5 h [range, 2.5 to 9.3 h] and 5.9 h [range, 4.0 to 17.7 h]; P = 0.034) and between the plasma and intracellular ritonavir t(1/2)s (4.1 h [range, 2.6 to 8.3 h] and 6.2 h [range, 3.9 to 18.6 h]; P = 0.032) were observed. No relationship was observed between the accumulation of saquinavir or ritonavir and lymphocyte subset P-gp expression. The intracellular t(1/2)s of saquinavir and ritonavir were longer than the plasma t(1/2)s, indicating that intracellular drug may be available at a time when concentrations in plasma are below the minimum effective concentration.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Enhanced T-cell maturation, differentiation and function in HIV-1-infected individuals after growth hormone and highly active antiretroviral therapy.

BACKGROUND: Strong virus-specific helper and cytotoxic T-cell responses correlate with non-progression during HIV-1 infection. Administration of antiretroviral therapy (ART) during the chronic phases of HIV-1 infection fails to restore these responses in most patients. DESIGN AND METHODS: We assessed the changes in immune function of 12 HIV-1-positive individuals treated with ART for over 4 years, who received 4 mg/day of recombinant human growth hormone (rhGH) for 12 weeks and were then randomized into groups receiving either placebo, twice weekly or alternate day dosing of rhGH. Peripheral blood was drawn for phenotypic analysis and functional assays at time points 0, 12 and 24 weeks. RESULTS: At week 12, we observed significant increases in naive CD4 T cells (P<0.01) and effector CD8 T cells based on CD45RA and CCR7 expression (P<0.02). In addition, we observed a rise in HIV-1 antigen-specific CD4 (P<0.005) and CD8 (P<0.05) T-cell responses. Twelve weeks post-randomization into placebo, alternate day or twice weekly dosing (24 weeks post-baseline), the phenotype and function of the virus-specific effector CD8 T cells seen at week 12 was maintained in most patients regardless of randomization arm and despite the disappearance of HIV-1-specific CD4 T-cell responses. CONCLUSIONS: Concomitant administration of rhGH at 4 mg/day with highly active ART appears to partially reverse some of the defects exerted on the immune system by HIV-1. This combination may represent a valuable immunotherapeutic intervention aiding in the treatment of chronic HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Does atazanavir cause lipodystrophy?

Atazanavir is a once-a-day non-pepsidic inhibitor of HIV protease which is licensed for use in the UK and the USA. One of its major advantages is that it does not produce lipid abnormalities in patients who receive it. This feature has been widely interpreted as implying that in the future there will be no abnormalities associated with fat redistribution when the drug is administered. This article explores that view.

Antiretroviral Therapy, Highly Active↗
PubMed2004

Mitochondrial toxicity: myths and facts.

Nucleoside analogue reverse transcriptase inhibitors (NRTIs) represent key components of the antiretroviral combinations used to manage HIV infection. A range of nucleoside analogues are currently available which differ in their convenience of administration, frequency of dosing, resistance profile and frequency and severity of adverse effects. Many of the important and treatment limiting side-effects of nucleoside analogues have been suggested to be related to the impact of these agents on mitochondrial DNA polymerase gamma. Depletion of mitochondrial DNA or impacts of these agents on mitochondrial enzymes during chronic nucleoside analogue therapy may lead to cellular respiratory dysfunction and both generalised and tissue specific toxicities. In particular, fatal lactic acidosis represents a rare but clinically important manifestation of nucleoside analogue induced mitochondrial dysfunction. Other potentially severe toxicities which are well-characterised include peripheral neuropathy (PN) and myopathy. Management of potentially mitochondrial toxicity during nucleoside analogue therapy remains a challenge. A range of nutritional supplements, both as treatments and prophylaxes have been proposed and some investigated in vitro but not as yet in vivo. At present, therefore, interruption of nucleoside analogue therapy, or substitution of the probable causative agent with nucleoside analogues which appear better tolerated represent the mainstay of management.

Acidosis, Lactic↗
PubMed2004

Pharmacokinetics of once-daily saquinavir/ritonavir in HIV-infected subjects: comparison with the standard twice-daily regimen.

OBJECTIVE: To evaluate the steady-state pharmacokinetics and safety of two once-daily saquinavir/ritonavir (SQV/RTV) regimens, 1600/100 and 2000/100 mg, in HIV-positive patients. METHODS: Eighteen HIV-infected adults treated with the standard twice-daily SQV/RTV 1000/100 mg regimen were enrolled in this open-label, two-phase, crossover pharmacokinetic study. The steady-state pharmacokinetics of SQV administered with 100 mg RTV were investigated following once-daily doses of 1600 mg or 2000 mg or a twice-daily dose of 1000 mg. Plasma drug concentrations were determined by high performance liquid chromatography-tandem mass spectrometry and pharmacokinetic parameters were calculated using a non-compartmental model. RESULTS: Compared with SQV 1000 mg twice daily, the Cmax of SQV following a 1600 mg and 2000 mg dose increased in a dose-proportional manner [geometric mean (95% CI) 1915 (1656-2850) ng/ml for 1000 mg, 2782 (2249-4330) ng/ml for 1600 mg and 4179 (3429-6105) ng/ml for 2000 mg doses, respectively]. SQV Ctrough values were 539 (453-1011), 106 (76-223) and 231 (75-822) ng/ml, respectively. A SQV Ctrough value greater than 100 ng/ml was achieved in all subjects on the twice-daily regimen, in 9/18 (50%) subjects on the 1600/100 mg once-daily regimen, and in 14/17 (82%) subjects on the 2000/100 mg once-daily regimen. The once-daily regimens were well tolerated, with mild-to-moderate gastrointestinal symptoms being the only events reported by a small number of patients. CONCLUSION: This is the first study to evaluate the pharmacokinetics of once-daily SQV/RTV 2000/100 mg in HIV-infected subjects. Our findings suggest that this regimen may be an alternative to twice-daily 1000/100 mg doses and should be further evaluated in efficacy studies. The data indicate that most patients (14/17) on once-daily 2000/100 mg achieve trough concentrations above target values (determined for HIV wild-type) for efficacy of SQV with the use of just 100 mg RTV/day and with good tolerability.

Adult↗
PubMed2002

Overcoming obstacles to the success of protease inhibitors in highly active antiretroviral therapy regimens.

Success with current protease inhibitors (PIs) is limited by substantial variability in pharmacokinetics, onset of adverse metabolic effects that include sustained lipid elevations and insulin resistance, and increased risk of lipodystrophy. Additionally, poor adherence to the often complex regimens can lead to emergence of PI-resistant human immunodeficiency virus (HIV) variants and treatment failure. Boosting blood levels of current PIs through coadministration of ritonavir can improve the pharmacokinetic characteristics of these agents, increasing the chances of success, but often at the price of additional adverse effects. New PIs in development have the potential to overcome at least some of these obstacles. Tipranavir, mozenavir, and atazanavir have favorable and unique resistance profiles, making them potentially effective in new treatment strategies in both PI-naïve and PI-experienced patients. Atazanavir does not cause the lipid elevations seen with current PIs, and it may improve adherence through once-daily dosing.

Antiretroviral Therapy, Highly Active↗
PubMed2002

Time for T.

Explore the source record for details and available documents.

CD4 Lymphocyte Count↗
PubMed2002

Analysis of virological efficacy in trials of antiretroviral regimens: drawbacks of not including viral load measurements after premature discontinuation of therapy.

OBJECTIVES: To compare two analytic approaches to assess the virological effect of HAART according to the intention-to-treat (ITT) principle. MATERIAL: Data from 2318 patients enrolled in 10 randomised clinical trials (RCTs) and from 3091 patients followed in an observation cohort (EuroSIDA) starting their first HAART regimen. METHODS: Two classifications of defining virological response 48 weeks after starting the therapy to be evaluated were compared: 1) only patients remaining on the therapy and having a plasma viral load (pVL) below a given cut-off level at week 48 were classified as responders (ITT/s=f); and 2) patients with a pVL below a given cut-off at week 48 whether they remained on initial assigned therapy or switched therapy were responders (ITT/s incl). In both analyses, patients with missing data at week 48 were classified as failures (i.e., non-responders). RESULTS: According to ITT/s=f, 22-70% of the patients starting a HAART regimen in a RCT experienced a virological response at week 48. Only two RCTs had complete follow-up data (n=424): between 29 and 62% achieved a virological response at week 48 in the six treatment arms evaluated in the studies according to ITT/s=f, and 41-72% according to ITT/s incl. Among those who discontinued the therapy to be evaluated in these two trials, 13-45% (cohort: 39-74%) subsequently experienced a virological response at week 48. The subsequent response rates were associated with the reason for discontinuation (toxicity versus confirmed virological failure: 63 vs 33%), varied largely across regimens and were not associated with the discontinuation rate. CONCLUSIONS: Discontinuation of follow-up at switch from the therapy to be evaluated remains common in antiretroviral treatment trials, but leads to an imprecise and incomplete assessment of the intrinsic effect of a given regimen. Complete follow-up of all patients should be encouraged strongly as this will allow for several complementary analytic approaches and a focus on optimal treatment strategies rather than specific regimens.

Antiretroviral Therapy, Highly Active↗