A prospective, randomized trial examining the efficacy and safety of clarithromycin in combination with ethambutol, rifabutin, or both for the treatment of disseminated Mycobacterium avium complex disease in persons with acquired immunodeficiency syndrome

This multicenter, randomized, open-label phase 3 clinical trial compared the safety and efficacy of 3 clarithromycin-containing combination regimens for the treatment of disseminated Mycobacterium avium complex (MAC) disease in persons with acquired immunodeficiency syndrome. A total of 160 eligible patients with bacteremic MAC disease were randomized to receive clarithromycin with either ethambutol (C+E), rifabutin (C+R), or both (C+E+R) for 48 weeks. After 12 weeks of treatment, the proportion of subjects with a complete microbiologic response was not statistically significantly different among treatment arms: the proportion was 40% in the C+E group, 42% in the C+R group, and 51% in the C+E+R group (P=.454). The proportion of patients with complete or partial responses who experienced a relapse while receiving C+R (24%) was significantly higher than that of patients receiving C+E+R (6%; P=.027) and marginally higher than that of patients receiving C+E (7%; P=.057). Subjects in the C+E+R group had improved survival, compared with the C+E group (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.23-0.83) and the C+R group (HR, 0.49; 95% CI, 0.26-0.92).

Effect of simultaneous versus staggered dosing on pharmacokinetic interactions of protease inhibitors

OBJECTIVE

The aim of this study was to determine whether pharmacokinetic interactions between the protease inhibitors saquinavir soft gel, nelfinavir, and ritonavir are affected by the timing of administration.

STUDY DESIGN

We used an open-label, 6-period, incomplete Latin square crossover study in 18 human immunodeficiency virus-negative subjects. Each received single oral doses of 2 of the 3 protease inhibitors during each of 6 periods. Single doses were given either simultaneously or separated by 4 hours. The order of the periods was balanced, and periods were separated by 2 days. We measured protease inhibitor concentrations over a 24-hour period by HPLC and estimated pharmacokinetic parameters by noncompartmental methods.

RESULTS

Median saquinavir area under the curve (AUC) increased by 62-fold when ritonavir was coadministered, by 50-fold when ritonavir was given 4 hours earlier, and by 16-fold when saquinavir preceded ritonavir by 4 hours. Saquinavir AUC increased by 7-fold when nelfinavir was coadministered. Nelfinavir AUC increased by 2.5-fold with coadministration of ritonavir and by 1.8- and 2.1-fold when ritonavir was administered before nelfinavir and after nelfinavir, respectively. Ritonavir AUCs were unaffected by coadministration of the other drugs. The effect of ritonavir on the kinetics of saquinavir persisted for at least 48 hours after a single dose of ritonavir, suggesting the possibility of metabolic intermediates that form inhibitory complexes.

CONCLUSION

Except for saquinavir followed by ritonavir, there is little difference in protease inhibitor exposure for simultaneous or staggered doses. The persistent effect of ritonavir suggests the possibility that lower doses and longer dosing intervals might be effective when ritonavir is used to boost concentrations of other protease inhibitors.

Steady-state pharmacokinetic interaction of modified-dose indinavir and rifabutin

BACKGROUND

Combined administration of the human immunodeficiency virus protease inhibitor indinavir (800 mg every 8 hours) with the antimycobacterial rifabutin (300 mg daily) results in a significant decrease in indinavir concentrations with subsequent risk of treatment failure, as well as a significant increase in rifabutin concentrations with increased toxicity. Therefore this study was designed to evaluate alternative dosing regimens.

METHODS

Eighteen healthy volunteers received 300 mg rifabutin daily alone for 14 days and then 1000 mg indinavir every 8 hours plus rifabutin at a reduced dose of 150 mg daily, given at 8 am or noon in a randomized crossover sequence for 14 days. Ten human immunodeficiency virus-infected subjects received 800 mg indinavir every 8 hours for 14 days and then 1000 mg indinavir every 8 hours plus 150 mg rifabutin daily at 8 am for 14 days. Twenty-four-hour pharmacokinetic sampling was performed at the end of each 14-day study period.

RESULTS

Indinavir, 1000 mg every 8 hours, coadministered with 150 mg rifabutin daily produced an area under the concentration-time curve similar to that of 800 mg indinavir every 8 hours. The mean area under the concentration-time curve values of rifabutin and 25-desacetyl rifabutin, when 150 mg rifabutin every morning was coadministered simultaneously with 1000 mg indinavir every 8 hours, were 70% and 120% higher than with 300 mg rifabutin daily alone. Drug concentrations were not different when rifabutin and indinavir were administered simultaneously at 8 am or staggered by 4 hours.

CONCLUSIONS

Increasing indinavir's dose to 1000 mg every 8 hours when coadministered with rifabutin at a reduced dose of 150 mg daily compensates for rifabutin induction of indinavir metabolism. Rifabutin concentrations were still higher than with rifabutin alone despite a 50% reduction of rifabutin dose, which is the current recommendation when these 2 drugs are combined. The clinical significance of the increase in rifabutin and 25-desacetyl rifabutin concentrations is not known.

Model-based analysis of the pharmacokinetic interactions between ritonavir, nelfinavir, and saquinavir after simultaneous and staggered oral administration

Eighteen healthy human immunodeficiency virus-negative subjects participated in an open-label, six-period, incomplete Latin-square crossover pharmacokinetic study. Each subject received two of the three possible pair-wise combinations of single-dose oral ritonavir (R) (400 mg), nelfinavir (N) (750 mg), and saquinavir (S) (800 mg), each pair on three occasions (simultaneous or staggered administration), each occasion at least 2 days after the last. A model-based analysis reveals the following major drug interactions under the conditions of this study: 1). R given simultaneously with S decreases S hepatic intrinsic clearance almost 50-fold relative to that predicted for S given alone and increases its gut bioavailability 90% (but decreases its rate of absorption 40%) relative to when N is given simultaneously; 2). N given simultaneously with S decreases S hepatic intrinsic clearance 10-fold relative to that predicted for S given alone; and 3) R inhibits S hepatic intrinsic clearance even after R plasma levels have become undetectable (>48 h after dosing), implying that R, when used as a pharmacokinetic enhancer, can be dosed less frequently than might be predicted from the duration of detectable systemic concentrations.

Differential effects of p-glycoprotein and multidrug resistance protein-1 on productive human immunodeficiency virus infection

P-glycoprotein (P-gp) and multidrug-resistance protein-1 (MRP-1) are adenosine triphosphate-binding cassette proteins that may decrease intracellular concentrations of anti-human immunodeficiency virus (HIV) drugs. After HIV-1(IIIB) infection, HIV-1 protein and infectious virus production were decreased by at least 70-fold in CEM cells overexpressing P-gp but were increased by at least 50-fold in CEM cells overexpressing MRP-1, compared with control CEM cells. After transfection with the HIV-1(IIIB) genome, cells overexpressing P-gp and MRP-1 expressed similar amounts of HIV protein. Selective inhibitors of MRP-1 and P-gp partially reversed the effect of these transporters in a concentration-dependent manner. P-gp preferentially associated with glycolipid-enriched membrane (GEM) domains, which may be an important site for cellular binding and egress of HIV. In contrast, MRP-1 was not preferentially found in GEM domains. These results suggest that the inhibition of HIV productive infection by P-gp and augmentation by MRP-1 occur predominantly at a preintegration step but act through different mechanisms.

Effect of ritonavir/saquinavir on stereoselective pharmacokinetics of methadone: results of AIDS Clinical Trials Group (ACTG) 401

The effect of ritonavir 400 mg/saquinavir 400 mg twice daily on the stereoselective pharmacokinetics of methadone was examined in 12 HIV-infected, methadone-using study subjects.

DESIGN

A 24-hour methadone pharmacokinetic study was performed before antiretroviral therapy was begun and after 15 days of therapy. Methadone concentration was measured by a chiral plasma assay because the drug is administered as a racemic mixture of R- and S-methadone, but only the R-isomer is active. Both changes in plasma protein binding and changes in objective and subjective opioid effect were monitored.

RESULTS

Ritonavir/saquinavir administration was associated with 40% decrease in total S-methadone AUC0-24hr and 32% decrease in R-methadone area under the curve (AUC)0-24hr, and both changes were statistically significant (p =.001 for both). When AUC was corrected for the changes in protein binding induced by ritonavir/saquinavir, R-methadone free AUC0-24hr decreased 19.6% whereas the S-methadone decreased 24.6%, neither of these changes was statistically significant (p =.129 and p =.0537, respectively). This change in methadone exposure was not associated with any evidence of withdrawal from narcotics and no modification of methadone dose was required.

CONCLUSIONS

Our data indicate that ritonavir/saquinavir administration is associated with induction of metabolism of methadone but this is greater for the inactive S-methadone. However, approximately 37% of the decrease in the total R-methadone exposure can be explained by protein binding displacement. Ritonavir/saquinavir can be used in HIV-infected people taking methadone without routine dose adjustments.

Chemotherapy for human immunodeficiency virus-associated non-Hodgkin's lymphoma in combination with highly active antiretroviral therapy

PURPOSE

This study investigated the efficacy, toxicity, and pharmacokinetic interactions resulting from simultaneous combination chemotherapy and highly active antiretroviral therapy (HAART) for patients with human immunodeficiency virus (HIV)-associated non-Hodgkin's lymphoma (NHL). In addition, the effects on viral load, CD4 counts, and opportunistic infections were examined with the use of combination chemotherapy combined with HAART.

PATIENTS AND METHODS

Sixty-five patients with previously untreated and measurable disease at any stage of HIV-associated NHL of intermediate or high grade were entered onto this study at 17 different centers. The first 40 patients entered onto the study received reduced doses of cyclophosphamide and doxorubicin, combined with vincristine and prednisone (modified CHOP [mCHOP]), whereas the subsequent 25 patients entered onto the study received full doses of CHOP combined with granulocyte colony-stimulating factor (G-CSF). All patients also received stavudine, lamivudine, and indinavir.

RESULTS

The complete response rates were 30% and 48% among patients who received mCHOP and full-dose CHOP combined with HAART, respectively. Grade 3 or 4 neutropenia occurred in 25% of patients receiving mCHOP and 12% of those receiving full-dose CHOP combined with G-CSF (25% v 12%). There were similar numbers of patients with grade 3 or 4 hyperbilirubinemia (12% and 17%), constipation and abdominal pain (18% and 17%), and transaminase elevation (48% and 52%) on the modified and full-dose arms of the study, respectively. Doxorubicin clearance and indinavir concentration curves were similar among patients on this study and historical controls, whereas cyclophosphamide clearance was 1.5-fold reduced as compared with control values. Human immunodeficiency virus (HIV) load declined from a median baseline value of 29,000 copies/mL to a median minimum value on therapy of 500 copies/mL.

CONCLUSION

Either modified-dose or full-dose CHOP chemotherapy for HIV-NHL, delivered with HAART, is effective and tolerable.

Suppression of preadipocyte differentiation and promotion of adipocyte death by HIV protease inhibitors

Many human immunodeficiency virus (HIV)-infected patients taking combination antiretroviral therapy that includes HIV protease inhibitors experience atrophy of peripheral subcutaneous adipose tissue. We investigated the effects of HIV protease inhibitors on adipogenesis and adipocyte survival using the 3T3-L1 preadipocyte cell line. Several HIV protease inhibitors were found either to inhibit preadipocyte differentiation or to promote adipocyte cell death. One protease inhibitor, nelfinavir, elicited both of these effects strongly. When induced to differentiate in the presence of nelfinavir, 3T3-L1 preadipocytes failed to accumulate cytoplasmic triacylglycerol and failed to express normal levels of the adipogenic transcription factors CCAAT/enhancer-binding protein alpha and peroxisome proliferator-activated receptor gamma. The level of the proteolytically processed, active 68-kDa form of sterol regulatory element-binding protein-1, a transcription factor known to promote lipogenic gene expression, also was reduced markedly in nelfinavir-treated cells, whereas the level of the 125-kDa precursor form of this protein was unaffected. The inhibitory effect of nelfinavir occurred subsequent to critical early events in preadipocyte differentiation, expression of CCAAT/enhancer-binding protein beta and completion of the mitotic clonal expansion phase, because these events were unaffected by nelfinavir treatment. In addition, nelfinavir treatment of fully differentiated 3T3-L1 adipocytes resulted in DNA strand cleavage and severe loss of cell viability. In contrast, cell proliferation and viability of preadipocytes were unaffected by nelfinavir treatment. Thus, molecular or cellular changes that occur during acquisition of the adipocyte phenotype promote susceptibility to nelfinavir-induced cell death. When considered together, these results suggest that nelfinavir may promote adipose tissue atrophy by compromising adipocyte viability and preventing replacement of lost adipocytes by inhibiting preadipocyte differentiation.

Safety, tolerability, and antiretroviral effects of ritonavir-nelfinavir combination therapy administered for 48 weeks

OBJECTIVE

To evaluate the safety, tolerability, and anti-HIV activity of ritonavir-nelfinavir (RTV-NFV).

DESIGN

Single-site, open-label, nonrandomized, multiple-dose trial of RTV combined with two doses of NFV in protease inhibitor (PI)-naive, HIV-infected patients.

METHODS

Mean baseline HIV RNA was 39,500 copies/ml; mean baseline CD4 count was 323 cells/mm3. All patients received RTV at a dosage of 400 mg twice daily. Cohorts I (N = 10) and II (N = 10) received NFV at a dosage of 500 mg and 750 mg twice daily, respectively, for the initial 12 weeks of the study before allowing intensification with reverse transcriptase inhibitors.

RESULTS

The commonest effects of RTV-NFV therapy were study drug-related moderate-to-severe diarrhea (9 patients in cohorts I and II) and drug-related moderate-to-severe nausea (4 patients in cohorts I and II). HIV RNA was suppressed in a biphasic manner. At 48 weeks in cohort I, mean HIV RNA reduction was 2.82 log10 copies/ml (standard error [SE] =.61; p =.001; N = 4); mean CD4 cell count increase was 236 cells/mm3 (SE = 67.1; p =.006; N = 4). In cohort II, mean HIV RNA reduction at Week 48 was 2.21 log10 copies/ml (SE =.430; p =. 001; N = 8); mean CD4 cell count increase was 120 cells/mm3 (SE = 47. 5; p =.03; n = 8). In cohort I patients, 2 of 4 completing Week 48 had HIV RNA <20 copies/ml; and 3 of 4 had HIV RNA <400 copies/ml. In cohort II, 2 of 8 patients completing Week 48 had HIV RNA <20 copies/ml and 4 of 8 had HIV RNA <400 copies/ml. In addition, 3 patients in cohort I withdrew because of virologic failure not thought to be related to poor compliance. Moreover, 15 patients elected to add new reverse-transcriptase inhibitors (RTIs) after week 12.

CONCLUSIONS

RTV-NFV with concomitant reverse transcriptase inhibitors is a potential dual-PI option for PI-naive patients.

Dual protease inhibitor therapy in HIV-infected patients: pharmacologic rationale and clinical benefits

HIV protease inhibitors, as components of combination antiretroviral drug regimens, have substantially reduced the morbidity and mortality associated with HIV infection. They selectively block the action of the virus-encoded protease and stop the virus from replicating. In general, these drugs have poor systemic bioavailability and must be dosed with respect to meals for optimal absorption. Protease inhibitor-containing regimens require ingestion of a large number of capsules, are costly, and produce or are susceptible to metabolic drug interactions. Simultaneous administration of two protease inhibitors takes advantage of beneficial pharmacokinetic interactions and may circumvent many of the drugs' undesirable pharmacologic properties. For example, ritonavir increases saquinavir concentrations at steady state by up to 30-fold, allowing reduction of saquinavir dose and dosing frequency. Ritonavir decreases the systemic clearance of indinavir and overcomes the deleterious effect of food on indinavir bioavailability. These benefits reflect inhibition of presystemic clearance and first-pass metabolism, as well as inhibition of systemic clearance mediated by hepatic cytochrome P450 3A4. Several dual protease inhibitor combination regimens have shown great promise in clinical trials and are now recommended as components of salvage therapy for HIV-infected patients.

Pharmacokinetics and safety of AMD-3100, a novel antagonist of the CXCR-4 chemokine receptor, in human volunteers

AMD-3100, a bicyclam, is a novel agent that uniquely inhibits the entry of human immunodeficiency virus type 1 (HIV-1) into CD4(+) T cells via selective blockade of the chemokine CXCR-4 receptor. Twelve healthy volunteers were given AMD-3100 as a single 15-min intravenous infusion at 10, 20, 40, or 80 microg/kg. Five subjects also received a single subcutaneous injection of AMD-3100 (40 or 80 microg/kg). Three subjects received two escalating oral doses each (80 and 160 microg/kg). All subjects tolerated their dose(s) well without any grade 2 toxicity or dose adjustment. Six subjects experienced mild, transient symptoms, primarily gastrointestinal in nature and not dose related. All subjects experienced a dose-related elevation of the white blood cell count, from 1.5 to 3.1 times the baseline, which returned to the baseline 24 h after dosing. AMD-3100 demonstrated dose proportionality for the maximum drug concentration in serum (C(max)) and the area under the concentration-time curve from 0 h to infinity (AUC(0-infinity)) over the entire dose range. At the highest intravenous dose (80 microg/kg), the median C(max) was 515 (range, 470 to 521) ng/ml and the AUC(0-infinity) was 1,044 (range, 980 to 1,403) ng-h/ml. The median systemic absorption after subcutaneous dosing was 87% (range, 67 to 106%). No drug was detectable in the blood following oral dosing. Using a two-compartment model, the median pharmacokinetic parameter estimates (ranges) were as follows: volume of distribution, 0.34 (0. 27 to 0.36) liter/kg; clearance, 1.30 (0.97 to 1.34) liters/h; elimination half-life, 3.6 (3.5 to 4.9) h. After a single, well-tolerated intravenous dose of AMD-3100, concentrations were sustained for 12 h above the in vitro antiretroviral 90% inhibitory concentrations and for 8 h above antiviral concentrations identified in the SCID-hu Thy/Liv mouse model of HIV infection.

Comparison of human immunodeficiency virus type 1 Pr55(Gag) and Pr160(Gag-pol) processing intermediates that accumulate in primary and transformed cells treated with peptidic and nonpeptidic protease inhibitors

Human immunodeficiency virus type 1 (HIV-1) produces two polyproteins, Pr55(Gag) and Pr160(Gag-Pol), that are cleaved into mature functional subunits by the virally encoded protease. Drugs that inhibit this protease are an important part of anti-HIV therapy. We studied the ordered accumulation of Gag and Gag-Pol processing intermediates by variably blocking the protease with HIV-1 protease inhibitors (PIs). Variable protease inhibition caused accumulation of a complex pattern of processing intermediates, which was the same after incubating HIV-1-infected cells with increasing concentrations of either one of the peptidomimetic inhibitors indinavir, saquinavir (SQV), ritonavir (RTV), nelfinavir, and SC-52151 or one of the nonpeptidomimetic inhibitors DMP450, DMP323, PNU-140135, and PNU-109112 for 3 days. The patterns of Gag and Gag-Pol processing intermediate accumulation were nearly identical when the following were compared: cell- versus virion-associated proteins, HIV-1-infected transformed cell lines versus primary human peripheral blood mononuclear cells (PBMCs) and HIV-1(MN) versus HIV-1(IIIB) virus strains. RTV was a more potent inhibitor of p24 production in PBMCs than SQV by approximately 7-fold, whereas SQV was a more potent inhibitor in transformed cells than RTV by approximately 30-fold. Although the antiretroviral potency of HIV-1 PIs may change as a function of cell type, the polyprotein intermediates that accumulate with increasing drug concentrations are the same. These results support sequential processing of Gag and Gag-Pol polyproteins by the HIV-1 protease and may have important implications for understanding common cross-resistance pathways.

Latent infection of CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy

Combination therapy for HIV-1 infection can reduce plasma virus to undetectable levels, indicating that prolonged treatment might eradicate the infection. However, HIV-1 can persist in a latent form in resting CD4+ T cells. We measured the decay rate of this latent reservoir in 34 treated adults whose plasma virus levels were undetectable. The mean half-life of the latent reservoir was very long (43.9 months). If the latent reservoir consists of only 1 x 10(5) cells, eradication could take as long as 60 years. Thus, latent infection of resting CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective anti-retroviral therapy.

The effects of rifampin and rifabutin on the pharmacokinetics and pharmacodynamics of a combination oral contraceptive

BACKGROUND

Rifampin (INN, rifampicin), a CYP34A inducer, results in significant interactions when coadministered with combination oral contraceptives that contain norethindrone (INN, norethisterone) and ethinyl estradiol (INN, ethinylestradiol). Little is known about the effects of rifabutin, a related rifamycin.

OBJECTIVES AND METHODS

The relative effects of rifampin and rifabutin on the pharmacokinetics and pharmacodynamics of ethinyl estradiol and norethindrone were evaluated in a prospective, randomized, double-blinded crossover study in 12 premenopausal women who were on a stable oral contraceptive regimen that contained 35 microg ethinyl estradiol/1 mg norethindrone. Subjects were randomized to receive 14 days of rifampin or rifabutin from days 7 through 21 of their menstrual cycle. After a 1-month washout period (only the oral contraceptives were taken), subjects were crossed over to the other rifamycin.

RESULTS

Rifampin significantly decreased the mean area under the plasma concentration-time curve from time 0 to 24 hours [AUC(0-24)] of ethinyl estradiol and the mean AUC(0-24) of norethindrone. Rifabutin significantly decreased the mean AUC(0-24) of ethinyl estradiol and the mean AUC(0-24) of norethindrone. The effect of rifampin was significantly greater than rifabutin on each AUC(0-24). Despite these changes, subjects did not ovulate (as determined by progesterone concentrations) during the cycle in which either rifamycin was administered. Levels of mean follicle-stimulating hormone increased 69% after rifampin.

CONCLUSION

In this study, rifampin (600 mg daily) was a more significant inducer of ethinyl estradiol and norethindrone clearance than rifabutin (300 mg daily), but neither agent reversed the suppression of ovulation caused by oral contraceptives. The carefully monitored oral contraceptive administration and the limited exposure to rifamycins may restrict the application of this study to clinical situations.

Combination antiretroviral therapy for HIV infection

The primary goal of antiretroviral therapy for human immunodeficiency virus (HIV) infection is suppression of viral replication. Evidence indicates that the optimal way to achieve this goal is by initiating combination therapy with two or more antiretroviral agents. The agents now licensed in the United States for use in combination therapy include five nucleoside analog reverse transcriptase inhibitors (zidovudine, didanosine, zalcitabine, stavudine and lamivudine), two nonnucleoside reverse transcriptase inhibitors (delavirdine and nevirapine) and four protease inhibitors (saquinavir, ritonavir, indinavir and nelfinavir). Current recommendations suggest that antiretroviral therapy be considered in any patient with a viral load higher than 5,000 to 20,000 copies per mL, regardless of the CD4+ count. Selection of the combination regimen must take into account the patient's prior history of antiretroviral use, the side effects of these agents and drug-drug interactions that occur among these agents and with other drugs as well. Because of the potential for viral resistance, nonnucleoside reverse transcriptase inhibitors and protease inhibitors should only be used in combination therapy. Antiretroviral agents are rapidly being developed and approved, so physicians must make increasingly complex treatment decisions about medications with which they may be unfamiliar.

Mutations of the human immunodeficiency virus type 1 p6Gag domain result in reduced retention of Pol proteins during virus assembly

One of the crucial steps in the assembly of the human immunodeficiency virus type 1 (HIV-1) and other retroviruses is the incorporation and retention of all the key viral enzymes in released virions. The viral enzymes protease, reverse transcriptase, and integrase of HIV-1 are initially synthesized as Gag-Pol fusion polyproteins. It has been shown that the incorporation of Gag-Pol polyproteins during virus assembly requires the Gag domains that are shared by the Gag and Gag-Pol precursors. We now report that truncation of the C-terminal p6 domain of HIV-1 Gag, which is present in the Gag precursor but not in the Gag-Pol precursor, drastically reduced the amount of Pol proteins in the mutant virions. Mutations in the lentivirus conserved motif P(T/S)APP in p6 also drastically reduced the amount of Pol proteins in mutant virions. The steady-state levels of Gag-Pol precursors and cleaved Pol proteins in the transfected cells were not affected by mutations in p6. The incorporation of unprocessed Gag-Pol precursors into p6 mutant virions was detected when the viral protease was mutated, suggesting that the interactions among mutant Gag molecules and Gag-Pol precursors were not significantly affected. These results suggest that the p6 domain of HIV-1 Gag may play an important role in recruiting or retaining cleaved Pol proteins during virus assembly.

Diagnosis of human immunodeficiency virus infection using citrated whole blood

Standard isolation of human immunodeficiency virus type 1 (HIV-1) from peripheral blood mononuclear cells (PBMC) requires 5 to 20 ml of blood, and the centrifugal separation of PBMC is expensive and time-consuming. Whole-blood coculture techniques use small sample volumes, do not require centrifugation, and allow measurement of the total viral burden in peripheral circulation. We compared the results of citrated whole-blood coculture with those obtained by the standard AIDS Clinical Trials Group PBMC semiquantitative culture method and reverse transcription-PCR quantitation of plasma HIV-1 RNA levels. PBMC cocultures were also set up with added erythrocytes (RBCs) to determine if the presence of RBCs affects the replication of HIV-1 in vitro. The mean number of cells required for a p24-positive PBMC coculture was approximately seven times greater than that required for a positive citrated whole-blood coculture (P < 0.01). At volumes of 100, 50, and 25 microl, the sensitivities of the whole-blood coculture were 94.5, 93.6, and 87.3%, respectively. The PBMC culture in the presence of added RBCs was more sensitive than PBMC coculture alone. The citrated whole-blood coculture was simple to perform, produced a reliable diagnosis of HIV infection in adult volunteers, was more sensitive than previously reported techniques even in half the culture time, and showed less variability than the PBMC coculture. Citrated whole-blood coculture may be a useful and efficient tool for diagnosing infection with HIV-1.

Phase I/II study of the toxicity, pharmacokinetics, and activity of the HIV protease inhibitor SC-52151

SC-52151, an HIV-1 protease inhibitor, was developed as an ethanol-based elixir and subsequently as a self-emulsifying drug delivery system (SEDDS) to improve bioavailability. To evaluate formulation and treatment regimen effects, we conducted a four-arm, phase I/II study using the highest previously tested daily dose, 2250 mg. Forty-nine patients received the elixir or SEDDS at a dosage of 750 mg three times daily or 1125 mg twice daily for 14 days. One patient developed hypertriglyceridemia, and one had fever and dyspnea. The SEDDS formulation compared with the elixir resulted in a larger area under the concentration-time curve (AUC, p < 0.001), peak (Cmax, p = 0.041) and trough (Cmin, p = 0.025). Twice-daily administration compared with administration three times daily produced a higher cumulative AUC (p = 0.008). Both SEDDS regimens produced mean plasma concentrations above the 90% inhibitory concentration (IC90) for HIV. A mean decline of 0.03 log10 RNA copies (SEDDS) and an increase of 0.15 log10 (elixir) were observed. Although SC-52151 was well tolerated and the SEDDS formulation resulted in plasma concentrations above the IC90 for viral replication, no antiviral activity was produced.

Drug interactions in patients infected with human immunodeficiency virus

Patients with AIDS who are receiving optimal medical care, including combination therapy with antiretroviral agents and more effective prophylaxis and therapy for opportunistic infections and neoplasms, are surviving longer. However, the potential for drug interactions in these patients is increased because many of the currently used antibiotics and antiviral agents have profound effects on the hepatic cytochrome P-450 enzyme system, on renal tubular function, and on bone marrow function. In this AIDS Commentary, Dr. Piscitelli and colleagues have succinctly reviewed the current state of our knowledge regarding the potential for additive or synergistic drug interactions that can result in enhanced toxicity or, alternatively, augmented therapeutic benefit. Information on these interactions will become more important as more intensive and effective therapy becomes available for persons with far-advanced infection due to human immunodeficiency virus type 1.

Oral antibiotic treatment of right-sided staphylococcal endocarditis in injection drug users: prospective randomized comparison with parenteral therapy

PURPOSE

To compare the efficacy and safety of inpatient oral antibiotic treatment (oral) versus standard parenteral antibiotic treatment (intravenous) for right-sided staphylococcal endocarditis in injection drug users.

PATIENTS AND METHODS

In a prospective, randomized, non-blinded trial, febrile injection drug users were assigned to begin oral or intravenous (IV) treatment on admission, before blood culture results were available. Oral therapy consisted of ciprofloxacin and rifampin. Parenteral therapy was oxacillin or vancomycin, plus gentamicin for the first 5 days. Antibiotic dosing was adjusted for renal dysfunction. Administration of other antibacterial drugs was not permitted during the treatment or follow-up periods. Bacteremic subjects having right-sided staphylococcal endocarditis received 28 days of inpatient therapy with the assigned antibiotics. Test-of-cure blood cultures were obtained during inpatient observation 6 and 7 days after the completion of antibiotic therapy, and again at outpatient follow-up 1 month later. Criteria for treatment failure and for drug toxicity were prospectively defined.

RESULTS

Of 573 injection drug users who were hospitalized because of a febrile illness and suspected right-sided staphylococcal endocarditis, 93 subjects (16.2%) had two or more sets of blood cultures positive for staphylococci; 85 of these bacteremic subjects (14.8%) satisfied diagnostic criteria for at least possible right-sided staphylococcal endocarditis (no other source of bacteremia was apparent) and entered the trial. Forty-four (oral, 19; IV, 25) of these 85 subjects completed inpatient treatment and evaluation including test-of-cure blood cultures. There were four treatment failures (oral, 1 [5.2%]; IV, 3 [12.0%]; not significant, Fisher's exact test). Drug toxicity was significantly more common in the parenterally treated group (oral, 3%; IV, 62%; P < 0.0001), consisting largely of oxacillin-associated increases in liver enzymes.

CONCLUSIONS

For selected patients with right-sided staphylococcal endocarditis, oral ciprofloxacin plus rifampin is effective and is associated with less drug toxicity than is intravenous therapy.

Inactivation of human immunodeficiency virus type 1 reverse transcriptase by oltipraz: evidence for the formation of a stable adduct

Oltipraz (5-pyrazinyl-4-methyl-1,2-dithiole-3-thione), which is undergoing clinical evaluation as an anticarcinogen, also inhibits HIV-1 replication (IC50 approximately equal to 10 microM). The inactivation of RT appears to be a relevant antiviral mechanism since oltipraz blocks viral replication in acutely infected T-cell lines, but is ineffective in chronically infected ACH-2 cells (H. J. Prochaska, W. G. Bornmann, P. Baron, and B. Polsky (1995) Mol. Pharmacol. 48, 15-20). Since a nucleophilic amino acid is a likely target for oltipraz, we assessed whether the conserved cysteine residues of HIV-1 RT (38Cys or 280Cys) were the target(s) for oltipraz, and we synthesized [Me 14C]oltipraz to determine if oltipraz forms a stable adduct with RT. Thus, HIV-2 RT as well as wild-type, 38Cys-->Ser, 280Cys-->Ser, and the Cys-->Ser double mutant of HIV-1 RT were purified from the lysates of transformed Escherichia coli strain DH5 alpha (A. Hizi, M. Shaharabany, R. Tal, and S. H. Hughes (1992) J. Biol. Chem. 267, 1293-1297) via a purification procedure that included (NH4)2SO4 fractionation followed by gel filtration, dye-ligand, and ion-exchange chromatographies. Procion yellow H4R was chosen as the dye-ligand chromatography since it was the most potent and selective inhibitor of RT among seventy reactive dyes that were screened. Mono Q anion-exchange chromatography with diethanolamine (pH 9) resulted in the generation of heterodimeric RT from a predominantly homodimeric enzyme preparation. Because the instability of dilute RT preparations at room temperature rendered the kinetic evaluation of inactivation difficult, we sought to identify conditions that prevent denaturation of these enzymes. High concentrations (25 mM) of MgCl2 had a stabilizing effect. Oltipraz behaved kinetically as an irreversible inhibitor of all RTs purified, and the kinetic constants for the inactivation of these enzymes were not significantly different from wild-type HIV-1 RT (Ki = 17.0 +/- 4.1 microM; k3 = 0.214 +/- 0.051 h-1). In stark contrast, oltipraz neither inhibited nor inactivated the Klenow fragment of DNA polymerase I, whose subdomain structure is similar to the p66 subunit of RT. Wild-type RT was incubated with 60 microM [Me 14C]oltipraz for 4 h and was then subjected to gel filtration chromatography. The [14C] label comigrated with RT with a stoichiometry of binding of 0.88 +/- 0.05 oltipraz per inactivated RT subunit (N = 3 experiments), and the [14C] label remained bound after treatment with 4 M urea.(ABSTRACT TRUNCATED AT 400 WORDS)

A randomized trial of the activity and safety of Ro 24-7429 (Tat antagonist) versus nucleoside for human immunodeficiency virus infection. The AIDS Clinical Trials Group 213 Team

Ro 24-7429, a Tat antagonist, dosed at 75, 150, or 300 mg/day, was compared with nucleoside analogue (zidovudine or didanosine) for 12 weeks in 96 human immunodeficiency virus (HIV)-infected patients to assess safety and activity. The primary adverse effect of Ro 24-7429 was rash, which necessitated treatment discontinuation in 6 of 71 patients. Nucleoside analogue treatment produced an average increase in CD4 cell count of 28 cells/mm3 at week 8 versus a decrease of 27 cells/mm3 in recipients of Ro 24-7429 (P < .001). Serum HIV p24 antigen levels decreased by an average of 111 pg/mL in nucleoside recipients at week 8 compared with an increase of 41 pg/mL in recipients of Ro 24-7429 (P = .007). Nucleoside-treated patients had a mean 0.66 log10 reduction in infectious peripheral blood mononuclear cells, while Ro 24-7429 recipients had a mean 0.02 log10 reduction (P = .02). No dose-response relationships were observed in the Ro 24-7429 groups. In this study, Ro 24-7429 treatment showed no evidence of antiviral activity.

High-dose pentoxifylline in patients with AIDS: inhibition of tumor necrosis factor production. National Institute of Allergy and Infectious Diseases AIDS Clinical Trials Group

Tumor necrosis factor-alpha (TNF) may activate human immunodeficiency virus (HIV), antagonize zidovudine activity, and contribute to AIDS wasting syndrome. Pentoxifylline decreases TNF production. In cell culture, pentoxifylline decreases HIV replication and gene expression. Since an AIDS Clinical Trial Group study suggested that pentoxifylline (400 mg thrice daily) is safe in AIDS patients and decreases TNF mRNA levels in peripheral blood mononuclear cells (PBMC), a second cohort received 800 mg thrice daily for 8 weeks. During treatment, the median decrease in TNF production by PBMC cultured with 0.1 microgram/mL lipopolysaccharide (LPS) was 40%. The median change in TNF mRNA was a 34% decrease. Pentoxifylline did not affect HIV levels as detected by quantitative microculture or serum p24 antigen measurements, nor did it alter zidovudine pharmacokinetics. The most common toxicity was gastrointestinal. Pentoxifylline at dosages of less than thrice-daily 800 mg is well tolerated and may decrease TNF mRNA levels and LPS-induced TNF production.

Relationship between plasma concentrations of 3'-deoxy-3'-fluorothymidine (alovudine) and antiretroviral activity in two concentration-controlled trials

Two concentration-controlled trials (CCTs) defined the relationship between plasma concentrations of 3'-deoxy-3'-fluorothymidine (alovudine) and changes in surrogate markers of antiretroviral activity. In an initial open-label CCT involving 14 subjects infected with human immunodeficiency virus (HIV), unacceptable hematologic toxicity occurred when the area under the concentration-time curve during a 12-h dosing interval (AUC12) was > or = 300 ng*h/mL. Consequently, 46 subjects were assigned to AUC12s of 50, 100, or 200 ng*h/mL for up to 16 weeks in a prospective, randomized, double-blind CCT. Alovudine caused a concentration-dependent reduction in p24 antigen and peripheral blood mononuclear cell HIV titers within 4 weeks of start of treatment. The AUC12 producing a 50% reduction in p24 (108 ng*h/mL) had a trough concentration identical to the reported IC50 of alovudine in HIV-infected H9 cells. It may be possible to predict the antiretroviral activity of certain nucleoside analogues as a function of plasma drug concentration.