Pharmacokinetics of zidovudine and dideoxyinosine alone and in combination in patients with the acquired immunodeficiency syndrome.

The pharmacokinetic profile and biochemical efficacy of idrapril calcium, a novel angiotensin converting enzyme (ACE) inhibitor, were evaluated in healthy volunteers after multiple dosing for 5 days at the doses of 100, 200 and 400 mg twice daily. The study was conducted as a double-blind, cross-over comparison of idrapril calcium against placebo. Plasma concentrations of idrapril were determined by an indirect enzymatic method. Urinary concentrations were measured by reverse phase high performance liquid chromatography (h.p.l.c.). Plasma samples were also analysed for ACE activity. The pharmacokinetics of idrapril calcium did not change significantly between day 1 and day 5. The values of Cmax and AUC were dose-related over the range of doses tested; tmax was 3-4 h and apparent elimination half-life was 1.4-1.6 h. Plasma ACE activity was maximally inhibited (94-96%) at all dose levels and remained more than 80% depressed from 2 to at least 6 h after idrapril calcium. Although the maximum effect was not dose-related, the duration of inhibition showed some dose-dependency, ACE activity returning to 56, 45 and 29% of the basal value 12 h after the 100, 200 and 400 mg doses, respectively. There were no clinically significant adverse events experienced by the volunteers. No dose-related effects on blood pressure or heart rate were observed. There were no changes in clinical pathology tests, urine analyses or electrocardiograms after dosing with idrapril calcium. Idrapril calcium, the prototype of a new class of ACE inhibitors, appears to be well-tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dideoxyinosine and dideoxycytidine on the intracellular phosphorylation of zidovudine in human mononuclear cells.

1. Zidovudine (3'-azido-2',3'-dideoxythymidine; AZT; ZDV) is a dideoxynucleoside analogue active against human immunodeficiency virus (HIV). We are currently investigating the intracellular metabolism of ZDV to its putative active triphosphate form (ZDV triphosphate) in peripheral blood mononuclear cells and a lymphoblastoid cell line (h1A2v2). 2. Optimal conditions for intracellular phosphate formation in peripheral blood mononuclear cells occurred following a 72 h preincubation with the mitogen phytohaemagglutinin at a concentration of 10 micrograms ml-1. ZDV was metabolized predominantly to the monophosphate with smaller amounts of the di- and triphosphate anabolites. There was considerable inter- and intraindividual variability in phosphate formation in peripheral blood mononuclear cells. A similar pattern of phosphorylation was seen with the h1A2v2 lymphoblastoid cell line with ZDV monophosphate being the major metabolite. 3. With increasing interest in combination nucleoside analogue therapy in HIV-positive patients it is important to know if an interaction occurs at the level of phosphorylation. Neither dideoxyinosine (ddI) or dideoxycytidine (ddC) significantly reduced the intracellular phosphorylation of ZDV in either peripheral blood mononuclear cells or h1A2v2 cells. In contrast thymidine always gave marked inhibition (e.g. at 2.0 microM, 89% inhibition of total phosphate formation in peripheral blood mononuclear cells and 79% in h1A2v2 cells). It is, therefore, unlikely that in vivo either ddI or ddC will perturb ZDV phosphorylation.     

Lack of an effect of azithromycin on the disposition of zidovudine and dideoxyinosine in HIV-infected patients

Two studies were conducted in HIV-infected subjects to assess the potential for azithromycin to interact with zidovudine and dideoxyinosine. Both studies used 12 subjects. The zidovudine study dosed subjects with 1200 mg/day of azithromycin (n = 7) (later changed to 600 mg/day [n = 5]) for Days 8 to 21 of a 21-day course of 100 mg, five times/day of zidovudine. Subjects treated with 200 mg of dideoxyinosine twice daily for 21 days received 1200 mg of azithromycin or an equivalent amount of placebo/day for Days 8 to 21. Antiretroviral plasma and urine sampling were conducted on Days 1, 7, and 21 for zidovudine and on Days 7 and 21 for dideoxyinosine. Peripheral mononuclear cells were also collected for quantitation of phosphorylated zidovudine. Azithromycin had no significant impact on the Cmax and AUC of zidovudine, although it significantly decreased the zidovudine tmax by 44% and increased the intracellular exposure to phosphorylated zidovudine by 110%. Azithromycin had no significant effect on dideoxyinosine pharmacokinetics. Based on the results of these studies, it is concluded that azithromycin may be safely coadministered with both zidovudine and dideoxyinosine.     

Pharmacokinetics of zidovudine and dideoxyinosine alone and in combination in children with HIV infection.

The pharmacokinetics of zidovudine (ZDV) and dideoxyinosine (ddI) were investigated following administration alone and in combination to children with symptomatic HIV disease. The children were studied on three separate occasions and received ZDV 200 mg m-2, ddI 100 mg m2 or a combination of ZDV 200 mg m-2 plus ddI 100 mg m-2. The administration of ddI did not significantly alter ZDV pharmacokinetics. The area under the curve (AUC) was 14.2 +/- 4.9 and 15.8 +/- 7.2 mumol l-1 h and elimination half-life (t1/2, z) was 1.4 +/- 0.4 and 1.2 +/- 0.2 h in the absence and presence of ddI respectively. The peak concentration (Cmax), time to peak (tmax) and apparent oral clearance (CL/F) were also unchanged. The administration of ZDV had no significant effect on ddI Cmax, tmax, t1/2,z, or CL/F, however the AUC was reduced by 19% (5.9 +/- 2.9 to 4.8 +/- 2.7 mumol l-1 h; P < 0.05). This study suggests that ZDV and ddI may be co-administered to children with symptomatic HIV disease without concern of a clinically relevant pharmacokinetic drug interaction.     

Effects of zidovudine (AZT) and dideoxyinosine (ddI) on human trophoblast cells

The anti-HIV agents AZT (zidovudine) and ddI (dideoxyinosine) are being used clinically during pregnancy. The toxicity of these agents to the fetus and placenta remains a concern because few human pregnancy exposure data are available, and pregnant rodent studies with AZT indicate increased embryonic resorptions and developmental arrest. The current study used a human choriocarcinoma cell line (JAr), which exhibits many characteristics of the early placenta, to assess the effects of a single 24 h exposure of 7.6 or 0.076 mM AZT, and the effects of a single 24 h exposure of 7.6 or 0.076 mM ddI upon cell proliferation and hormone production of human chorionic gonadotropin (hCG), estradiol (E₂), and progesterone (P₄). The higher concentration of AZT and ddI produced significant (P < 0.025) reductions in cell numbers and growth rate while producing significant increases in hormone production (hCG, E₂, and P₄). The lower concentration of AZT and ddI produced significant increases in E₂ production, but no changes in cell numbers, hCG, or P₄. Because placental cells require androgen precursor for E₂ synthesis, exogenous androstenedione was added to confirm observations of increased estradiol synthesis after AZT or ddI exposure. These results demonstrate that single 24 h high dose exposures of AZT or ddI produce significant inhibition of cell proliferation and alterations in hormone production in this paradigm of human placental cells.     

Pharmacokinetics of zidovudine phosphorylation in patients infected with the human immunodeficiency virus.

The relationship between zidovudine phosphorylation inside mononuclear cells and plasma zidovudine pharmacokinetic was assessed in six subjects. Plasma and intracellular concentrations were measured by radioimmunoassay over an 8-h period after administration of 100 or 200 mg of zidovudine. Plasma pharmacokinetics followed expected patterns, with considerable interpatient variability in area under the concentration-versus-time curve (AUC), and a terminal half-life of 1.5 h. Intracellular AUC was even more variable than plasma AUC, but the data suggested a crude linear relationship between these parameters. The intracellular half-life of 3.5 h was consistently longer than the plasma half-life, and varied little between patients. The prolonged intracellular half-life suggested that total phosphorylated zidovudine, as measured by the method described, is not greatly dominated by the 5'-monophosphate as predicted from the in vitro studies reported in the literature. Plasma concentrations of zidovudine have shown little correlation with clinical effect. Study of the relationship between phosphorylated zidovudine and clinical outcome could lead to a more effective management of therapy.     

Granulocyte-macrophage colony-stimulating factor and zidovudine in the treatment of neutropenia and human immunodeficiency virus infection.

Granulocyte-macrophage colony-stimulating factor (GMCSF) is a hematopoietic protein that has been studied both in vitro and in vivo in human immunodeficiency virus (HIV) infection. Since both HIV infection primarily and zidovudine (formerly AZT) treatment secondarily may result in neutropenia, administration of GMCSF to persons with HIV infection is generating considerable interest. Despite in vitro studies demonstrating that the agent may stimulate HIV replication, in the presence of zidovudine a synergistic inhibition of replication occurs. Early clinical studies in patients with the acquired immunodeficiency syndrome indicate that GMCSF can raise neutrophil counts with or without concurrent zidovudine treatment. The long-term safety and tolerance of the combination has to be established.     

Immunohematotoxicity studies with combinations of dapsone and zidovudine

We investigated the immunohematoxicities of the antiparasitic drug dapsone (DDS) and the antiretroviral drug zidovudine (ZDV, AZT) given alone or in combination in BALB/c mice. DDS is used for prophylaxis and treatment of Pneumocystis carinii infection in AIDS patients. We examined the impact of concurrent administration of these drugs on the immune and hematopoietic systems because DDS causes hematotoxicity and ZDV therapy results in bone marrow toxicity. Daily oral administration of DDS at 25 and 50 mg/kg for 28 days caused a slight anemia, marked methemoglobinemia, reticulocytosis, and a moderate leukopenia (P < 0.01 for all parameters) but had no discernible effect on platelet count. In DDS-treated mice, the proliferative response of splenic T cells to concanavalin A was > or = 35% higher than that manifested by splenocytes from vehicle-treated control mice. ZDV at 240 and 480 mg/kg was not immunosuppressive but caused low-grade macrocytic anemia, thrombocytosis, and neutropenia; these effects were drug dose-dependent and statistically significant (P < 0.01). Concurrent administration of DDS and ZDV augmented the severity of ZDV-mediated macrocytic anemia, and 7 of 12 (58%) mice did not survive treatment with the high doses of DDS and ZDV (50 and 480 mg/kg, respectively). On the other hand, co-administration of ZDV mitigated DDS-induced methemoglobinemia and the DDS-associated elevation in lymphoproliferative response. These data suggest interaction between DDS and ZDV in mice and indicate a need for caution in using DDS as long-term therapy in AIDS patients receiving ZDV.     

Transfer of dideoxyinosine across the human isolated placenta.

1. The metabolism of imipramine (N-demethylation and 2-hydroxylation) was studied in relation to the activity of S-mephenytoin 4'-hydroxylase in human liver microsomes. 2. Eadie-Hofstee plots for the formation of despiramine and 2-hydroxyimipramine were biphasic, suggesting that at least two enzymes are involved in both the N-demethylation and 2-hydroxylation of imipramine by human liver microsomes. 3. The respective mean (+/- s.d.) kinetic parameters for the N-demethylation and 2-hydroxylation of imipramine derived from a two-enzyme kinetic analysis were: Km1 = 1.1 +/- 0.4 and 1.6 +/- 0.6 microM, Vmax1 = 0.11 +/- 0.03 and 0.15 +/- 0.07 nmol mg-1 min-1, and Vmax1/Km1 = 0.10 +/- 0.02 and 0.09 +/- 0.04 ml mg-1 min-1; Km2 = 214 +/- 84 and 257 +/- 148 microM, Vmax2 = 2.22 +/- 0.69 and 0.53 +/- 0.15 nmol mg-1 min-1, and Vmax2/Km2 = 0.011 +/- 0.001 and 0.003 +/- 0.002 ml mg-1 min-1. 4. With regard to imipramine N-demethylation and 2-hydroxylation at 2 microM (representing high-affinity reactions) and at 400 microM (representing low-affinity reactions), only N-demethylation at 2 microM showed a close correlation with the 4'-hydroxylation of S-mephenytoin (rs = 0.952, P < 0.01; n = 10 livers). 5. Concentrations up to 250 microM S-mephenytoin inhibited the N-demethylation of imipramine (2 microM), but no further inhibition was observed using concentrations from 250 to 750 microM. 6. Imipramine inhibited S-mephenytoin 4'-hydroxylation competitively with a Ki value of 12.5 microM.(ABSTRACT TRUNCATED AT 250 WORDS)     

The additive in vitro anti-HIV-1 effect of chloroquine, when combined with zidovudine and hydroxyurea

The 4-aminoquinoline chloroquine and its analogue hydroxychloroquine are endowed with anti-HIV-1 activity both in vitro and in vivo. We previously reported that the addition of CQ (chloroquine) to the combination of HU (hydroxyurea) and ddI (didanosine) provides additive anti-HIV-1 activity. We here extended this in vitro investigation by studying whether the addition of CQ also resulted in additive anti-HIV-1 activity when combined with HU plus AZT (zidovudine). The same effect was found, whether CQ was added to HU plus AZT or to HU plus ddI, in recently infected H-9 and U-937 cells or primary T cells and monocytes, as well as in immunologically or oxidatively stimulated ACH-2 and U-1 cells. At concentrations where CQ exerts its anti-HIV-1 effect in combination with the other drugs, CQ addition does not result in either cell toxicity or apoptosis.     

尿多酸肽对人胃癌细胞SGC7901增殖的体外抑制作用

目的：研究肿瘤细胞分化诱导剂尿多酸肽（CDA—Ⅱ）对人胃癌细胞的体外抑制作用．方法：将CDA—Ⅱ胃癌细胞株SGC7901进行体外培养，观察CDA—Ⅱ对人胃癌细胞生长曲线及形态学等方面的影响。以四唑盐（MTT）比色法测定培养板中加入CDA—Ⅱ后，人胃癌细胞SGC7901的生物活性。结果：CDA—Ⅱ可减缓胃癌细胞的生长和增殖能力，体外实验中CDA—Ⅱ剂量为1—5mg／ml，对人胃癌细胞SGC7901的作用最佳剂量为1mg／ml。结论：在体外实验中CDA-Ⅱ可抑制胃癌细胞的增殖能力，对人胃癌细胞SGC7901有显著的抑制作用。     

Influence of probenecid and paracetamol (acetaminophen) on zidovudine glucuronidation in human liver in vitro.

The effects of probenecid and paracetamol on zidovudine glucuronidation were investigated, in vitro, using human liver microsomal preparations. The presence of probenecid in the incubation medium significantly reduced the maximum reaction velocity for zidovudine glucuronide formation by more than 60 per cent, and the Km was reduced by 47 per cent, suggesting an uncompetitive inhibition of zidovudine glucuronidation. In contrast, paracetamol had no significant effect on zidovudine glucuronidation. The maximum reaction velocity for zidovudine glucuronide formation and the Km were unchanged when paracetamol (5 mM) was present in the incubation medium. The effects of probenecid and paracetamol on zidovudine metabolism in vitro correlates closely with those observed in vivo. The in vitro system of human liver microsomes may have a useful role in predicting the possible interaction of other drugs with zidovudine metabolism.     

P1-substituted symmetry-based human immunodeficiency virus protease inhibitors with potent antiviral activity against drug-resistant viruses

Because there is currently no cure for HIV infection, patients must remain on long-term drug therapy, leading to concerns over potential drug side effects and the emergence of drug resistance. For this reason, new and safe antiretroviral agents with improved potency against drug-resistant strains of HIV are needed. A series of HIV protease inhibitors (PIs) with potent activity against both wild-type (WT) virus and drug-resistant strains of HIV was designed and synthesized. The incorporation of substituents with hydrogen bond donor and acceptor groups at the P1 position of our symmetry-based inhibitor series resulted in significant potency improvements against the resistant mutants. By this approach, several compounds, such as 13, 24, and 29, were identified that demonstrated similar or improved potencies compared to 1 against highly mutated strains of HIV derived from patients who previously failed HIV PI therapy. Overall, compound 13 demonstrated the best balance of potency against drug resistant strains of HIV and oral bioavailability in pharmacokinetic studies. X-ray analysis of an HIV PI with an improved resistance profile bound to WT HIV protease is also reported.