A dose-ranging study to evaluate the antiretroviral activity and safety of amprenavir alone and in combination with abacavir in HIV-infected adults with limited antiretroviral experience

OBJECTIVE

To evaluate the antiretroviral activity and safety of multiple escalating doses of amprenavir administered alone, and in combination with abacavir in HIV-1-infected adults.

DESIGN

Sixty-two HIV-1-infected subjects were enrolled in a multicentre, open-label, non-randomized, dose-escalating trial.

METHODS

Subjects were assigned to one of six dose groups and received amprenavir 300 mg twice daily, 300 mg three times daily, 900, 1050, or 1,200 mg twice daily for 4 weeks. One dose group received amprenavir 900 mg twice daily in combination with abacavir 300 mg twice daily for 4 weeks. Antiretroviral activity was assessed by measuring changes from baseline in plasma HIV-1 RNA levels and CD4 cell counts. Safety was evaluated by monitoring clinical adverse events and changes in laboratory values. Genotypic and phenotypic analyses were performed using ABI sequencing and the recombinant virus assay, respectively.

RESULTS

At week 4, amprenavir monotherapy (900, 1,050, or 1,200 mg twice daily) resulted in marked decreases in plasma HIV-1 RNA levels (1.3-1.6 log10 copies/ml), and substantial increases in CD4 cell counts in the two dose groups who received 1,050 mg twice daily (118 x 10(6) cells/mm3) or 1,200 mg twice daily (114 x 10(6) cells/mm3). Amprenavir/abacavir resulted in median plasma HIV-1 RNA reductions of 1.8 log10 copies/ml, and median CD4 cell count increases of 138 x 10(6) cells/mm3. Amprenavir was reasonably well tolerated with few treatment-limiting adverse events. No known active site mutations associated with amprenavir resistance were selected in any of the dose groups, and no significant phenotypic resistance to amprenavir developed during 4 weeks of therapy.

CONCLUSIONS

The antiviral effect of amprenavir monotherapy increased with escalating doses, and all amprenavir doses were reasonably well tolerated over 4 weeks of therapy. Amprenavir/abacavir combination therapy elicited a potent antiviral effect. The three highest doses of amprenavir (900, 1,050 and 1,200 mg twice daily) were selected to design subsequent Phase II and III studies that confirmed the safety profile and efficacy of amprenavir in combination regimens and led to the approval of amprenavir in the USA in 1999.

Amprenavir in combination with lamivudine and zidovudine versus lamivudine and zidovudine alone in HIV-1-infected antiretroviral-naive adults. Amprenavir PROAB3001 International Study Team

OBJECTIVES

To compare the antiviral activity and safety of a new protease inhibitor, amprenavir (141W94) in combination with lamivudine and zidovudine, versus lamivudine and zidovudine alone in HIV-1 infected, antiretroviral-naive subjects.

DESIGN

Subjects (n=232) with a CD4 T cell count of > or =200 cells/mm3, plasma HIV-1 RNA levels of > or =10000 copies/ml, and < or =4 weeks of prior nucleoside antiretroviral therapy, were stratified according to baseline plasma HIV-1 RNA level (10000-30000; 30000-100000; or >100000 copies/ml). Subjects received double-blind treatment with either 1200 mg amprenavir twice daily in combination with lamivudine (150 mg twice daily) and zidovudine (300 mg twice daily) (amprenavir/lamivudine/zidovudine) or matched placebo, lamivudine and zidovudine for 16 weeks. Thereafter, subjects with confirmed plasma HIV-1 RNA levels of > or =400 copies/ml could add open-label amprenavir or switch to other antiretrovirals and continue treatment for up to a minimum of 48 weeks. The primary endpoint of the study was defined as the proportion of subjects with plasma HIV-1 RNA of <400 copies/ml at 48 weeks.

RESULTS

At 48 weeks, a significantly greater proportion of amprenavir/lamivudine/zidovudine subjects had plasma HIV-1 RNA levels <400 copies/ml than lamivudine/ zidovudine subjects in the overall population: 41 versus 3% (intent-to-treat missing equals failure analysis) (P<0.001); 93 versus 42% (as-treated analysis) (P<0.001); and within each of the three randomization strata (P<0.001). Subjects on amprenavir/lamivudine/zidovudine experienced longer time to event (permanent discontinuation of randomized therapy or viral rebound) than those on lamivudine/zidovudine (median of 33 versus 13 weeks; P<0.001). A significantly greater incidence of drug-related nausea, vomiting, rash and oral/perioral paresthesia was observed with amprenavir/lamivudine/zidovudine than with lamivudine/zidovudine.

CONCLUSIONS

Amprenavir, in combination with lamivudine and zidovudine, has potent and durable antiviral activity in antiretroviral-naive subjects over 48 weeks. Amprenavir was safe and generally well tolerated.

Effect of subcutaneous naratriptan on forearm blood flow

This randomized, double-blind, placebo-controlled, four-way crossover study was conducted on an in-clinic basis to assess forearm perfusion after subcutaneous (s.c.) naratriptan and placebo by reserve volume (hyperemic/baseline) and basal forearm blood flow (FBF) measured by strain gauge plethysmography. Nineteen male and female volunteer migraine subjects (International Headache Society criteria) received s.c. naratriptan 1 mg, 5 mg, 10 mg, and placebo on four separate study days outside a migraine attack. FBF was recorded at baseline, at 7-min intervals post-dose up to 1 h (basal) and once after sublingual glyceryl trinitrate administered at 1 h (hyperemic). Vital signs and electrocardiograms were recorded at baseline and 15, 30, 45, and 60 min post-dose. There were no statistically significant differences in reserve volume (hyperemic/baseline) between any dose of s.c. naratriptan and placebo. The naratriptan to placebo ratio was 102% (95% CI: 87-120%; p = 0.789) for 1 mg; 97% (95% CI: 83-114%, p = 0.737) for 5 mg; and 92% (95% CI: 79-108%; p = 0.325) for 10 mg. There were no statistically significant differences in basal FBF for any dose compared to placebo. The naratriptan to placebo ratio was 95% (95% CI: 87-104%; p = 0.263) for 1 mg; 94% (95% CI: 86-102%; p = 0.142) for 5 mg; and 94% (95% CI: 86-103%; p = 0.157) for 10 mg. The percentage of patients reporting adverse events was 53% with placebo, 53% with s.c. naratriptan 1 mg, 89% with 5 mg and 89% with 10 mg. In conclusion, these results suggest that s.c. naratriptan doses similar to and above the oral therapeutic dose equivalent (single oral dose 2.5 mg) have no significant effect on peripheral blood flow as measured by FBF. S.c. naratriptan doses 1 mg, 5 mg, and 10 mg were well tolerated.

Effect of once daily and twice daily sustained release theophylline formulations on daytime variation of bronchial hyperresponsiveness in asthmatic patients

BACKGROUND

Previous studies evaluating spirometric values and symptoms have shown that once daily theophylline administered in the evening produces greater stabilisation of the airway function in asthmatic patients than the prototype theophylline given twice a day. The aim of this study was to compare the effects on bronchial responsiveness to methacholine of an ultrasustained release theophylline formulation (Diffumal-24, Malesci, Florence, Italy) administered once a day, a sustained release theophylline formulation (Theo-Dur, Recordati, Milan, Italy) administered twice a day, and placebo.

METHODS

The study was performed in 12 adult patients with asthma using a randomised, double blind, three phase, cross-over design. Each phase lasted seven days and was followed or preceded by at least three days of theophylline washout. Diffumal-24 was administered once a day at 20.00 hours whereas Theo-Dur was given twice a day at 08.00 hours and 20.00 hours. In each patient the total daily dose of theophylline was the same during both phases. The dose of the two active preparations was titrated to individual needs before the beginning of the study and then given in divided or once daily doses. At 08.00, 14.00, and 20.00 hours on day 7 of each phase serum theophylline concentrations were measured and spirometric tests (FEV1) and bronchial challenge with methacholine were also performed.

RESULTS

When the administration of Diffumal-24 was compared with that of Theo-Dur, a higher serum theophylline concentration of the former was seen in the morning whereas at 20.00 hours the reverse was true. Compared with placebo, at 08.00 hours Diffumal-24 improved FEV1 whereas Theo-Dur did not (difference between treatments 0.29 1, 95% CI 0.12 to 0.45). At 08.00 hours Diffumal-24 decreased bronchial sensitivity to methacholine, expressed as a natural logarithm of PD20, to a greater extent than Theo-Dur (difference between treatments 0.54 log units, 95% CI 0.016 to 1.08). The morning advantage observed with Diffumal-24 administration was not associated with a deterioration in the state of the airway during the daytime, the protective activity against methacholine during the 12 hours of the monitoring period being constant. Furthermore there was no difference in the mean FEV1 between the two treatments at 14.00 and 20.00 hours.

CONCLUSIONS

In adults with stable bronchial asthma treatment with a single dose of Diffumal-24 administered in the evening improved airflow obstruction and reduced bronchial hyperresponsiveness.