Stephen Becker

HIV-Associated Thrombotic Microangiopathy in the Era of Highly Active Antiretroviral Therapy: An Observational Study

The prevalence and predisposing factors of thrombotic microangiopathy (TMA) in the era of highly active antiretroviral therapy (HAART) were evaluated among patients in the Collaborations in Human Immunodeficiency Virus (HIV) Outcomes Research/US cohort. Of 6022 patients, 17 (0.3%) had TMA, with unadjusted incidences per 100 person-years of 0.079 for TMA, 0.009 for thrombotic thrombocytopenic purpura, and 0.069 for hemolytic-uremic syndrome. Compared with patients without TMA, patients with TMA had lower mean CD4(+) cell counts (197 vs. 439 cells/mm(3); P=.0009) and higher mean log(10) HIV-1 RNA levels (4.6 vs. 3.3 copies/mL; P=.0001) at last follow-up and a significantly greater incidence of acquired immune deficiency syndrome (82.4% vs. 55.3%; P=.025), Mycobacterium avium complex infection (17.6% vs. 3.3%; P=.018), hepatitis C (29.4% vs. 11.3%; P=.001), and death (41.2% vs. 7.4%; P<.0001). The prevalence of herpes and use of antiherpetics were slightly higher for patients with TMA, but unadjusted distributions were not statistically significant. TMA in a cohort surveyed after the introduction of HAART was rare and was associated with advanced HIV disease.

Proof of Activity with AMD11070, an Orally Bioavailable Inhibitor of CXCR4-Tropic HIV Type 1

BACKGROUND The X4 Antagonist Concept Trial investigates the safety and antiviral activity of AMD11070, a potent inhibitor of X4-tropic human immunodeficiency virus (HIV) in vitro in HIV-infected patients harboring X4-tropic virus. METHODS Patients enrolled in the study had an X4 virus population 2000 relative luminescence units (rlu; by the Monogram Trofile Assay) and an HIV-1 RNA level 5000 copies/mL. Patients received AMD11070 monotherapy for 10 days. Coreceptor tropism, plasma HIV-1 RNA level, and CD4 cell count were measured at study entry, on day 5, and on day 10. Daily predose and serial samples on the last day of treatment were obtained for determination of plasma AMD11070 concentration. RESULTS Ten patients were given AMD11070 monotherapy (200 mg to 8 patients and 100 mg to 2 patients) twice daily for 10 days. The median baseline CD4 cell count was 160 cells/mm(3), and the median HIV-1 RNA level was 91,447 copies/mL. Four of 9 evaluable patients achieved a reduction in X4 virus population of >or= rlu. The median change in X4 virus population at the end of treatment was -0.22 log(10) rlu (range, -1.90 to 0.23 log(10) rlu). Three of 4 patients who responded to therapy showed a tropism shift from dual- or mixed-tropic viruses to exclusively R5 virus by day 10. There were no drug-related serious adverse events, adverse events of greater than grade 2, or laboratory abnormalities. CONCLUSION These results demonstrate the activity of AMD11070, the first oral CXCR4 antagonist, against X4-tropic HIV-1. The drug was well tolerated, with no serious safety concerns. AMD11070 is on clinical hold because of histologic changes to the liver observed in long-term animal studies; additional preclinical safety assessments are pending.

Liver Toxicity in Epidemiological Cohorts

Hepatotoxicity has been demonstrated to be associated with antiretroviral therapy. Previous studies have included small numbers of patients and, thus, were unable to produce adequate statistical comparisons. I review data analyses from the Amsterdam, CHORUS, ICONA and Target studies (5133 patients), which were conducted by a number of investigators. There were differences between the cohorts with respect to the incidence of viral hepatitis and definitions of hepatotoxicity used. However, in all cohorts, hepatotoxicity in human immunodeficiency virus type 1-infected patients was significantly associated with coinfection with viral hepatitis. In 3 cohorts, elevated baseline alanine aminotransferase levels predicted subsequent hepatotoxicity. Overall, there was a low incidence of long-term hepatotoxicity in these cohorts and no consistent association between a particular drug or drug class. Nevirapine use within the first 12 weeks after initiation of therapy with this drug and ritonavir use are associated with increased risk of antiretroviral-associated hepatotoxicity.

Zidovudine and stavudine sequencing in HIV treatment planning: Findings from the CHORUS HIV Cohort

Background: Optimal sequencing of zidovudine and stavudine in antiretroviral therapy has not been elucidated. Objective: To examine the impact of the sequence of therapeutic regimens containing zidovudine and stavudine on HIV‐1 RNA and CD4 lymphocyte counts over 12 months. Design: Observational, multicenter, longitudinal cohort study. Setting: Four large outpatient, HIV practices participating in the community‐based Collaborations in HIV Outcomes Research—U.S. (CHORUS) cohort study. Participants: 940 HIV‐infected patients. Methods: Comparison of HIV‐1 RNA and CD4 lymphocyte responses in patients sequenced from zidovudine to stavudine or from stavudine to zidovudine using repeated measures regression models fit to outcomes by application of generalized estimating equation (GEE) methodology. Results: Patients treated with zidovudine prior to stavudine (n = 834) achieved a greater mean drop from baseline HIV‐1 RNA (p = .01) and higher proportion of undetectable HIV‐1 RNA results (p = .05) over 12 months than those sequenced from stavudine to zidovudine (n = 106). CD4+ lymphocyte increases did not differ between the groups (p = .6). Conclusions: Prior zidovudine therapy was not associated with long‐term attenuation of HIV‐1 RNA or CD4 response to subsequent stavudine‐containing regimens. Zidovudine before stavudine may have benefit in a strategic long‐term therapeutic plan.

Pharmacokinetic Effect of AMD070, an Oral CXCR4 Antagonist, on CYP3A4 and CYP2D6 Substrates Midazolam and Dextromethorphan in Healthy Volunteers

Background:Many antiretroviral drugs used in HIV care involve complex drug metabolism by CYP3A4 and CYP2D6 enzymes, and drug interactions are problematic clinically. AMD070, a novel entry inhibitor, is an inhibitor of X4-tropic HIV virus. In vitro data suggested that it is a CYP3A4 substrate and may inhibit CYP2D6 and CYP3A4. Methods:Twelve healthy subjects were given a single oral dose of 5 mg of midazolam and 30 mg of dextromethorphan on day 1 and 9, and 200 mg of AMD070 twice daily on days 2 through 9 (inclusive). Pharmacokinetic parameters of midazolam and dextromethorphan were assessed alone and in the presence of AMD070. Results:The mean AUC0-24 and Cmax of dextromethorphan increased 2.86-fold (2.20 to 5.10, 90% confidence interval [CI]) and 2.52-fold (1.99 to 4.24, 90% CI), respectively, in the presence of AMD070. Plasma AUC0-12 of midazolam increased 1.33-fold (1.15 to 1.61, 90% CI) without change in Cmax. The half-life did not change for both drugs, but significant, parallel decrease in apparent oral clearance and volume of distribution was observed. Conclusions:The data support an alteration in bioavailability due to an AMD070-mediated inhibition of presystemic metabolism, though an intestinal P-glycoprotein effect could also be contributing. Interactions between AMD070 with CYP3A4 and, especially, 2D6 substrates of clinical importance in HIV care should be further explored.

Disease progression in HIV-infected patients treated with stavudine vs. zidovudine

BACKGROUND AND OBJECTIVES This prospective, observational study compared disease progression and death in HIV-1 patients treated with stavudine vs. zidovudine in the Collaborations in HIV Outcomes Research/U.S. (CHORUS) cohort. METHODS Patients with a first occurrence of CD4 count <500 cells/microL (n=3301) were grouped as: no nucleoside reverse transcriptase inhibitor (NRTI) use; other NRTI without stavudine or zidovudine; stavudine with no zidovudine, with or without other NRTIs; and zidovudine with no stavudine, with or without other NRTIs. The risk for death or disease progression was evaluated in unadjusted analyses and using a Cox proportional hazards model, adjusting for: study site, age, gender, race, route of HIV infection, previous AIDS-defining conditions, number of previous antiretroviral regiments, CD4 count, HIV-1 RNA, and treatment variables. Sensitivity analyses were conducted to determine the sensitivity of the results to major modeling assumptions. A landmark analysis was conducted to determine the absolute difference in time to event. RESULTS During a median follow-up of 2.4 years, there were 57 deaths and 348 AIDS-defining conditions in 405 patients. Stavudine treatment compared with zidovudine resulted in a greater percentage of patients with AIDS-defining events (14.5 vs. 10.9%; P=.013), and an increased risk of disease progression (HR=1.30; 95% CI: 1.01,1.7; P=.04). This result was not sensitive to modeling assumptions. Landmark analysis demonstrated an absolute difference in time to 95% event-free survival of 2.7 months for those with a CD4< or =200 cells/microL and 11 months for those 6 months after model entry. CONCLUSIONS In unadjusted and adjusted analyses of 3301 HIV-1 infected patients, stavudine containing combination therapy was associated with an increased risk of disease progression or death compared to therapy containing zidovudine. Most of the difference was attributable to new cases of wasting.

Defining Antiviral Potency: IC

For several decades, the potency of antimicrobial agents has been measured primarily by the 50% inhibitory concentration (IC50; the drug concentration

Exploring Once-Daily Tenofovir + 3TC + Abacavir: An Argument for Clinical-Trials-Based Data

In the first formally presented data on once-daily tenofovir + 3TC + abacavir, the regimen is shown to be suboptimal. Problem is, clinicians have already been using it.