The purine analog 2',3'-dideoxyinosine (ddI), which has anti-retroviral activity in vitro was administered for up to 42 weeks to 26 patients with acquired immunodeficiency syndrome (AIDS) or severe AIDS-related complex (ARC). Ten of these individuals were AZT-intolerant. Eight dose regimens were studied. The drug was orally bioavailable and penetrated into the cerebrospinal fluid (CSF). Comparatively little evidence of an effect against human immunodeficiency virus (HIV) was seen at the lowest four doses. However, patients in the four highest dose groups (ddI at 1.6 milligrams per kilogram intravenously and then greater than or equal to 3.2 milligrams per kilogram orally at least every 12 hours or higher) had increases in their circulating CD4+ T cells (P less than 0.0005), increased CD4/CD8 T cell ratios (P less than 0.01), and, where evaluable, more than an 80% decrease in serum HIV p24 antigen (P less than 0.05). The patients also had evidence of improved immunologic function, had reduced viremic symptomatology, and gained a mean of 1.6 kilogram with these comparatively infrequent dosing schedules (every 8 or 12 hours). The most notable adverse effects directly attributable to ddI administration at the doses used in this study included increases in serum uric acid (due to hypoxanthine release) and mild headaches and insomnia. These results suggest that serious short-term toxicity at therapeutic doses is not an inherent feature in the profile of agents with clinical anti-HIV activity. Further controlled studies to define the safety and efficacy of this agent may be worth considering.

Because of the probable role of HIV-infected monocyte/macrophages in the pathogenesis and progression of AIDS, it is essential that antiretroviral therapy address viral replication in cells of this lineage. Several dideoxynucleosides have been shown to have potent in vitro and, in the case of 3'-azido-2',3'-dideoxythymidine (AZT) and 2',3'-dideoxycytidine (ddC), in vivo activity against HIV. However, because these compounds must be phosphorylated (activated) in target cells, and because monocyte/macrophages may have levels of kinases that differ from those in lymphocytes, we investigated the capacity of these drugs to suppress HIV replication in monocyte/macrophages using HIV-1/HTLV-IIIBa-L (a monocytotropic isolate). In the present study, we observed that HTLV-IIIBa-L replication in fresh human peripheral blood monocyte/macrophages was suppressed by each of three dideoxynucleosides: 3'-azido-2',3'-dideoxythymidine (AZT), 2',3'-dideoxycytidine (ddC), and 2',3'-dideoxyadenosine (ddA). Similar results were observed in 5-d-cultured monocyte/macrophages, although higher concentrations of the drugs were required. We then studied the metabolism of AZT and ddC in such cells. The phosphorylation of ddC to a triphosphate moiety was somewhat decreased in monocyte/macrophages as compared with H9 T cells. On the other hand, the phosphorylation of AZT in monocyte/macrophages was markedly decreased to 25% or less of the level in T cells. However, when we examined the level of the normal endogenous 2'-deoxynucleoside triphosphate pools, which compete with 2',3'-dideoxynucleoside triphosphate for viral reverse transcriptase, we found that the level of 2'-deoxycytidine-triphosphate (dCTP) was six- to eightfold reduced, and that of 2'-deoxythymidine-triphosphate (dTTP) was only a small fraction of that found in T cell lines. These results suggest that the ratio of dideoxynucleoside triphosphate to normal deoxynucleoside triphosphate is a crucial factor in determining the antiviral activity of dideoxynucleosides in HIV target cells, and that the lower levels of dTTP may account for the antiretroviral activity of AZT in the face of inefficient phosphorylation of this compound.

17-Dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG) and 17-allylamino-17-demethoxygeldanamycin (17-AAG) are two derivatives of geldanamycin (GA) that are currently undergoing clinical evaluation as anticancer agents. These agents bind to heat shock protein 90 (hsp90), resulting in the destabilization of client proteins and inhibition of tumor growth. In a search for the mechanism of hepatotoxicity, which is a dose-limiting toxicity for these agents, we found that GA and its derivatives, 17-AAG and 17-DMAG, react chemically (i.e., nonenzymatically) with glutathione (GSH). A combination of liquid chromatography/electrospray ionization/mass spectrometry and nuclear magnetic resonance analyses were used to identify the product of this reaction as a GSH adduct in which the thiol group of GSH is substituted in the 19-position of the benzoquinone ring. The reaction proceeds rapidly with GA and 17-DMAG (half-lives of approximately 1.5 and 36 min, respectively) and less rapidly with 17-AAG and its major metabolite, 17-AG (half-lives of approximately 9.8 and 16.7 h). The reaction occurs at pH 7.0, 37 degrees C, and a physiological concentration of GSH, indicating that cellular GSH could play a role in modulating the cellular toxicity of these agents and therefore be a factor in their mechanism of differential toxicity. Moreover, reactions with thiol groups of critical cellular proteins could be important to the mechanism of toxicity with this class of anticancer agents.

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This article describes the pharmacokinetics of 2',3'-dideoxyadenosine (ddA) and 2',3'-dideoxyinosine (ddI) as determined during phase I clinical trials in patients with acquired immunodeficiency syndrome and acquired immunodeficiency syndrome-related complex. Drug levels were determined by HPLC in plasma, cerebrospinal fluid, and urine after administration of the drugs either intravenously or as an oral liquid given with antacid. ddA was metabolized rapidly and quantitatively to ddI to such an extent that ddA was undetectable in the plasma even during continuous intravenous administration of ddA. The plasma kinetics of ddI were generally monoexponential and were characterized by a half-life of 38 minutes. This probably does not accurately reflect the kinetics of the active species of ddI, which appears to be 2',3'-dideoxyadenosine triphosphate, formed intracellularly. Oral bioavailability was 38% for oral liquid given with antacid. The total body clearance averaged 1.00 L/kg/hr, with a volume of distribution of 1.01 L/kg. Approximately 36% of the intravenous dose could be recovered unchanged in the urine. The level of ddI in the cerebrospinal fluid 1 hour after drug infusion averaged 21% of that of the simultaneous plasma level. It is concluded that ddI has pharmacokinetic properties that are amenable to its clinical use.

We have investigated the influence of granulocyte-macrophage CSF (GM-CSF) on the replication of HIV-1 in cells of monocyte/macrophage (M/M) lineage, and its effect on the anti-HIV activity of several 2'3'-dideoxynucleoside congeners of thymidine in these cells in vitro. We found that replication of both HTLV-IIIBa-L (a monocytotropic strain of HIV-1) and HTLV-IIIB (a lymphocytotropic strain) is markedly enhanced in M/M, but not in lymphocytes exposed to GM-CSF in culture. Moreover, GM-CSF reduced the dose of HIV required to obtain productive infection in M/M. Even in the face of this increased infection, GM-CSF also enhanced the net anti-HIV activity of 3'-azido-2'3'-dideoxythymidine (AZT) and several related congeners: 2'3'-dideoxythymidine (ddT), 2'3'-dideoxy-2'3'-didehydrothymidine (D4T), and 3'-azido-2'3'-dideoxyuridine (AZddU). Inhibition of viral replication in GM-CSF-exposed M/M was achieved with concentrations of AZT and related drugs, which were 10-100 times lower than those inhibitory for HIV-1 in monocytes in the absence of GM-CSF. Other dideoxynucleosides not related to AZT showed unchanged or decreased anti-HIV activity in GM-CSF-exposed M/M. To investigate the possible biochemical basis for these effects, we evaluated the metabolism of several drugs in M/M exposed to GM-CSF. We observed in these cells markedly increased levels of both parent and mono-, di-, and triphosphate anabolites of AZT and D4T compared with M/M not exposed to GM-CSF. By contrast, only limited increases of endogenous competing 2'-deoxynucleoside-5'-triphosphate pools were observed after GM-CSF exposure. Thus, the ratio of AZT-5'-triphosphate/2'-deoxythymidine-5'-triphosphate and 2'3'-dideoxy-2'3'-didehydrothymidine-5'-triphosphate/2'-deoxythymi dine- 5'-triphosphate is several-fold higher in GM-CSF-exposed M/M, and this may account for the enhanced activity of such drugs in these cells. Taken together, these findings suggest that GM-CSF increases HIV-1 replication in M/M, while at the same time enhancing the anti-HIV activity of AZT and related congeners in these cells. These results may have implications in exploring new therapeutic strategies in patients with severe HIV infection.

Liver microphysiological systems (MPSs) are promising models for predicting hepatic drug effects. Yet, after a decade since their introduction, MPSs are not routinely used in drug development due to lack of criteria for ensuring reproducibility of results. We characterized the feasibility of a liver MPS to yield reproducible outcomes of experiments assaying drug toxicity, metabolism, and intracellular accumulation. The ability of the liver MPS to reproduce hepatotoxic effects was assessed using trovafloxacin, which increased lactate dehydrogenase (LDH) release and reduced cytochrome P450 3A4 (CYP3A4) activity. These observations were made in two test sites and with different batches of Kupffer cells. Upon culturing equivalent hepatocytes in the MPS, spheroids, and sandwich cultures, differences between culture formats were detected in CYP3A4 activity and albumin production. Cells in all culture formats exhibited different sensitivities to hepatotoxicant exposure. Hepatocytes in the MPS were more functionally stable than those of other culture platforms, as CYP3A4 activity and albumin secretion remained prominent for greater than 18 days in culture, whereas functional decline occurred earlier in spheroids (12 days) and sandwich cultures (7 days). The MPS was also demonstrated to be suitable for metabolism studies, where CYP3A4 activity, troglitazone metabolites, diclofenac clearance, and intracellular accumulation of chloroquine were quantified. To ensure reproducibility between studies with the MPS, the combined use of LDH and CYP3A4 assays were implemented as quality control metrics. Overall results indicated that the liver MPS can be used reproducibly in general drug evaluation applications. Study outcomes led to general considerations and recommendations for using liver MPSs. WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Microphysiological systems (MPSs) have been designed to recreate organ‐ or tissue‐specific characteristics of extracellular microenvironments that enhance the physiological relevance of cells in culture. Liver MPSs enable long‐lasting and stable culture of hepatic cells by culturing them in three‐dimensions and exposing them to fluid flow. WHAT QUESTION DID THIS STUDY ADDRESS? What is the functional performance relative to other cell culture platforms and the reproducibility of a liver MPS for assessing drug development and evaluation questions, such as toxicity, metabolism, and pharmacokinetics? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? The liver MPS systematically detected the toxicity of trovafloxacin. When compared with spheroids and sandwich cultures, this system had a more stable function and different sensitivity to troglitazone, tamoxifen, and digoxin. Quantifying phase II metabolism of troglitazone and intracellular accumulation of chloroquine demonstrated the potential use of the liver MPS for studying drug metabolism and pharmacokinetics. Quality control criteria for assessing chip function were key for reliably using the liver MPS. HOW MIGHT THIS CHANGE CLINICAL PH...

We administered radiolabeled dextran sulfate (3H labeled on the reducing end, MW approximately 8000) [( 3H]DS) to rats. High-performance liquid chromatography (HPLC) analysis of plasma from animals that were given [3H]DS intravenously revealed an initial plasma half-life of about 30 min. Eleven percent of [3H]DS administered was recovered in the urine in 24 h; this material represented minor breakdown with a molecular weight of 4000 as determined by size exclusion HPLC analysis. When administered orally, the apparent bioavailability of [3H]DS was 6.8%, based on the recovered radioactivity; however, the molecular weight of the radioactive material obtained from the plasma was all less than 200, indicating that no detectable intact dextran sulfate was absorbed upon oral administration. Only 2% of orally administered [3H]DS was found in the 24-h urine; this material also had a molecular weight less than 200. Further less than 2300 had no anti-HIV effect and that in the presence of higher concentrations of human serum, more DS was required for antiviral effect. Although the pharmacokinetics of dextran sulfate in rats can differ from those in humans to some extent, these data suggest that oral administration of DS is unlikely to produce significant antiretroviral effect against HIV in vivo and higher plasma levels of DS may be necessary than those inferred from earlier in vitro data.