Sequencing of protease inhibitor therapy: insights from an analysis of HIV phenotypic resistance in patients failing protease inhibitors

OBJECTIVE

To characterize the pattern of HIV-1 susceptibility to protease inhibitors in patients failing an initial protease inhibitor-containing regimen.

DESIGN

A cross-sectional analysis of antiretroviral susceptibility.

SETTING

HIV clinics in six metropolitan areas.

PATIENTS

Eighty-eight HIV-infected adults with HIV RNA > 400 copies/ml after > or = 6 months of antiretroviral therapy, including the use of one protease inhibitor for > or = 3 months.

MEASUREMENTS

The frequency and magnitude of decreased susceptibility, measured with a phenotypic assay using recombinant constructs, to five protease inhibitors. Decreased susceptibility was defined as > 2.5-fold increase in the 50% inhibitory concentration (IC50) compared with drug sensitive control virus.

RESULTS

At study entry, patients were being treated with nelfinavir (63%), indinavir (25%), or another protease inhibitor (11%). HIV isolates from these patients were susceptible (fold change < 2.5) to all five protease inhibitors in 18% of patients and to none in 8%. Isolates from patients receiving nelfinavir were less likely to have reduced susceptibility to other protease inhibitors than isolates from patients treated with indinavir (P < 0.001) or one of the other three agents (P < 0.001), even after adjustment for the duration of prior protease inhibitor use. Reduced susceptibility to saquinavir and amprenavir was observed significantly less frequently than for the other protease inhibitors.

CONCLUSION

The frequency of protease inhibitor cross-resistance and the magnitude of changes in susceptibility varied according to the initial protease inhibitor used in the failing treatment regimen. Significantly less protease inhibitor cross-resistance was demonstrated for isolates from patients failing a nelfinavir-containing regimen compared with those from patients receiving other protease inhibitors.

Concentration-targeted phase I trials of atevirdine mesylate in patients with HIV infection: dosage requirements and pharmacokinetic studies. The ACTG 187 and 199 study teams

RATIONALE

To determine the dosage requirements and pharmacokinetics of atevirdine, a non-nucleoside reverse transcriptase inhibitor and its N-dealkylated metabolite (N-ATV) during phase I studies in patients receiving atevirdine alone or in combination with zidovudine.

DESIGN

Two open label, phase I studies conducted by the adult AIDS Clinical Trials Group (ACTG) in which atevirdine was administered every 8 h with weekly dosage adjustments to attain targeted trough plasma atevirdine concentrations.

SETTING

Five Adult AIDS Clinical Trials Units.

PATIENTS

Fifty patients (ACTG 199; n = 20 and ACTG 187; n = 30) with HIV-1 infection and < or =500 CD4+ lymphocytes/mm3.

INTERVENTION

ACTG 199; 12 weeks of therapy with atevirdine (dose-adjusted to achieve plasma trough atevirdine concentrations of 5-10 microM) and zidovudine (200 mg every 8 h). ACTG 187: 12 weeks of atevirdine monotherapy with atevirdine doses adjusted to achieve escalating, targeted trough plasma concentration ranges (5-13, 14-22, and 23-31 microM).

MEASUREMENTS

ACTG 199: atevirdine, N-ATV and zidovudine trough determinations weekly (all patients) and intensive pharmacokinetics (selected patients) prior to and at 6 and 12 weeks during combination therapy. ACTG 187: atevirdine and N-ATV trough concentrations over a 12 week period. Intensive pharmacokinetic studies were conducted prior to and at 4 and/or 8 weeks during atevirdine monotherapy in female patients.

RESULTS

Atevirdine plasma concentrations demonstrated considerable interpatient variability which was minimized by the adjustment of maintenance doses (range: 600-3900 mg/day) to achieve the desired trough concentrations. In ACTG 187, the mean number of weeks to attain the target value, and the percentage of patients who attained the target, was group I (5-11 microM): 2.7+/-2.4 weeks (92%); group II (12-21 microM): 2.6+/-1.8 (64%); and group III (22-31 microM): 7.0+/-5.6 weeks (27%). In ACTG 199 it was 3.2+/-5.2 weeks (95%) to achieve a 5-10 microM trough. Atevirdine demonstrated a mono- or bi-exponential decline among most of the patients studied after the first dose. During multiple-dosing a number of patterns of atevirdine disposition were observed including; rapid absorption with Cmax at 0.5-1 h, delayed absorption with Cmax at 3-4 h; minimal Cmax to Cmin fluctuation and Cmax to Cmin ratios of > 4. N-ATV (an inactive metabolite) patterns were characterized on day one by rapid appearance of the metabolite which peaked at 2-3 h after the dose and declined in a mono- or bi-exponential manner. At steady-state N-ATV patterns demonstrated minimal Cmax to Cmin fluctuations with some of the patients having more stable plasma N-ATV concentrations, while others had greater fluctuations week to week.

CONCLUSIONS

Considerable interpatient variability was noted in the pharmacokinetics of atevirdine. The variation in drug disposition was reflected in the range of daily doses required to attain the targeted trough concentrations. Atevirdine metabolism did not appear to reach saturation during chronic dosing in many of our patients, as reflected by the pattern of N-ATV/ATV ratios in plasma and saturation was not an explanation for the variation in dosing requirements. No apparent differences were noted between males and females, and atevirdine did not appear to influence zidovudine disposition.

Phase I study of atevirdine mesylate (U-87201E) monotherapy in HIV-1-infected patients

The safety, tolerability, and antiviral activity of atevirdine (ATV), a nonnucleoside reverse transcriptase inhibitor, were studied in a phase I/II clinical trial (ACTG 187) of patients with CD4 counts < or =500/mm3. In all, 34 HIV-1-infected patients were randomized to receive ATV for 12 weeks in doses chosen to achieve one of three serum trough levels: 5 to 13 microM, 14 to 22 microM, or 23 to 31 microM. Rash was the most common adverse event, with a grade 3 or 4 rash occurring in 4 patients. No significant change from baseline in HIV-1 plasma RNA mean copy number was detected at week 4 (+0.09 log10 copies/ml; p = .30). However, some evidence indicated moderate antiviral activity at week 4, based on median changes in CD4 count (+23/mm3; p = .05), and viral peripheral blood mononuclear cell (PBMC) titer (-0.68 log10) copies/ml; p = .03). In addition, 2 of 4 patients with detectable baseline serum p24 antigen showed declines of >50%. HIV-1 resistance to ATV was detected in 41% of patients and was most commonly associated with RT mutations K103N and Y181C. In contrast, the Y181C mutation was not detected in ATV-resistant isolates obtained from patients enrolled in ACTG 199, a study of ATV given in combination with zidovudine. Under the conditions of this study, ATV failed to demonstrate significant antiretroviral activity. However, transient in vivo activity might have been obscured by rapid development of resistance coupled with inadequate sampling at early time points following initiation of ATV therapy.

Phase I study of atevirdine, a nonnucleoside reverse transcriptase inhibitor, in combination with zidovudine for human immunodeficiency virus type 1 infection. ACTG 199 Study Team

Twenty patients were enrolled in a phase I clinical trial of atevirdine, a nonnucleoside reverse transcriptase inhibitor (NNRTI), given in combination with zidovudine for treatment of human immunodeficiency virus type 1 (HIV-1) infection. Fifteen patients had received no previous antiretroviral therapy. HIV-1 isolates obtained at 6-week intervals were tested for sensitivity to atevirdine and zidovudine. Two patients developed a rash within 2 weeks of enrollment, and 1 of these developed concomitant fever and hepatitis. No hematopoietic, neurologic, or pancreatic toxicities were observed. Atevirdine had considerable initial interpatient pharmacokinetic variability. Forty-seven percent of patients treated with atevirdine plus zidovudine had increased CD4 lymphocyte counts, and HIV isolates from 62% of patients remained sensitive to atevirdine after 24 weeks of therapy. Atevirdine plus zidovudine was well-tolerated. Additional studies should be done to determine the role of atevirdine in the therapy for HIV infection.

The tolerance for zidovudine plus thrice weekly or daily trimethoprim-sulfamethoxazole with and without leucovorin for primary prophylaxis in advanced HIV disease. California Collaborative Treatment Group

PURPOSE

Trimethoprim-sulfamethoxazole (TMP/SMX) is the preferred agent for prophylaxis of Pneumocystis carinii pneumonia (PCP) in patients with HIV infection, but frequent adverse events limit its usefulness. Intermittent dosing and supplementation with leucovorin have been tried in attempts to improve tolerance. We evaluated these strategies in persons with advanced HIV disease.

METHOD

One hundred seven patients were enrolled. All had HIV infection, < 200 CD4+ lymphocytes per mm3, and no history of PCP. Fifty-two were randomized to TMP/SMX twice daily (BID); of these, 26 were randomized to leucovorin with each dose. Fifty-five patients were randomized to TMP/SMX (BID) 3 times per week; of these, 27 were randomized to leucovorin with each dose. All patients took zidovudine concurrently.

RESULTS

The 24-week risk of discontinuation due to protocol-defined limiting toxicity was 24% with thrice-weekly TMP/SMX versus 42% with daily TMP/SMX (risk ratio 0.4; 95% CI 0.2 to 1.0). The risks of discontinuation for any reason were 41% and 59% (risk ratio 0.4; 95% CI 0.2 to 0.8). Clinical toxicity, such as headache and gastrointestinal distress, accounted for the observed difference in tolerance between dosing regimens. The 24-week risk of discontinuation due to protocol-defined toxicity was 33% in both the leucovorin and non-leucovorin groups (risk ratio 1.1; 95% CI 0.5 to 2.5). The risks of discontinuation for any reason were 53% and 47% (risk ratio 0.8; 95% CI 0.3 to 1.7).

CONCLUSION

Intermittent therapy with TMP/SMX BID thrice weekly is better tolerated than daily BID therapy. Leucovorin use does not improve tolerance for chronic TMP/SMX dosing in AIDS, even among patients taking tablets daily.

Acetaminophen does not impair clearance of zidovudine

OBJECTIVE

To determine whether concurrent treatment with acetaminophen and zidovudine impairs clearance of zidovudine, thereby increasing the risk for zidovudine-induced hematologic toxicity.

DESIGN

Dose escalation, drug interaction study.

SETTING

University clinical research center.

PATIENTS

Patients with the acquired immunodeficiency syndrome (AIDS) or advanced AIDS-related complex.

INTERVENTIONS

Acetaminophen and 200 mg of zidovudine simultaneously every 4 hours. For 13 patients, the unit dosage of acetaminophen was 325 mg for 3 days; for 8 patients, the dosage was 650 mg for 3 days; and, for 6 patients, the dosage was 650 mg for 7 days.

MEASUREMENTS

Zidovudine clearance and production of the glucuronide conjugate of zidovudine were assessed after acetaminophen treatment.

MAIN RESULTS

Neither zidovudine clearance nor production of the glucuronide conjugate of zidovudine was impaired after treatment with acetaminophen. Clearance of zidovudine was actually accelerated by 5%, 11%, and 33% with the three acetaminophen regimens, respectively (P = 0.002 by analysis of variance; P = 0.04 for linear trend when changes in the area-under-the-curve for zidovudine were compared).

CONCLUSION

Because serum concentrations of zidovudine decrease after the coadministration of acetaminophen, a pharmacokinetic interaction between zidovudine and acetaminophen is unlikely to increase the risk for hematologic toxicity associated with zidovudine.

Treatment of disseminated Mycobacterium avium complex infection in AIDS with amikacin, ethambutol, rifampin, and ciprofloxacin. California Collaborative Treatment Group

OBJECTIVE

To determine the efficacy of combination drug therapy for disseminated Mycobacterium avium complex infection in patients with the acquired immunodeficiency syndrome (AIDS).

DESIGN

Prospective, nonrandomized, before-after comparison.

SETTING

Outpatient clinics at three university medical centers.

PATIENTS

Seventeen patients with at least two consecutive blood cultures positive for M. avium complex who had not been previously treated with antituberculous medications. Fifteen of the seventeen patients completed at least 4 weeks of treatment.

INTERVENTION

Patients received daily intravenous amikacin (7.5 mg/kg body weight) for the first 4 weeks plus the following oral medications for at least 12 weeks: ciprofloxacin, 750 mg twice daily; ethambutol, 1000 mg daily; and rifampin, 600 mg daily.

MEASUREMENTS AND MAIN RESULTS

The baseline geometric mean colony count from blood cultures decreased from 537/mL to 14/mL (P less than 0.001) after 4 weeks of therapy. The microbiologic suppression was sustained while on treatment and was associated with a decrease in systemic symptoms related to M. avium complex infection. Premature withdrawal from treatment (less than 12 weeks) occurred in 7 of 17 patients. The commonest reasons for early withdrawal were gastrointestinal intolerance and hepatic toxicity.

CONCLUSIONS

Mycobacterial load and systemic symptoms in patients with AIDS and disseminated M. avium complex infection can be effectively reduced by a regimen containing amikacin, ethambutol, rifampin, and ciprofloxacin.

Clinical features of 100 human immunodeficiency virus antibody-positive individuals from an alternate test site

We evaluated 100 human immunodeficiency virus (HIV) antibody-positive persons from the only alternate test site in Los Angeles. Thirty-five subjects complained of systemic symptoms suggestive of HIV infection and 65 were completely asymptomatic. Irrespective of symptoms, the group as a whole demonstrated clinical and laboratory evidence of immunodeficiency. Eighty had generalized lymphadenopathy, 16 onychomycosis, six oral candidiasis, and two biopsy-proved Kaposi's sarcoma. Seventy-seven were anergic to seven intradermal antigens. Despite normal white blood cell counts in most subjects, the T-helper-cell count was less than 300/mm3 in 48% of asymptomatic and 46% of symptomatic subjects. The degree of immune depression was less severe but approximated that of patients with acquired immunodeficiency syndrome after Pneumocystis carinii pneumonia. We believe these findings justify the need for comprehensive medical evaluation and follow-up care for seropositive persons from alternate test sites.

Bactericidal studies of penicillin-gentamicin combinations against group B streptococci

The bactericidal activity of penicillin-aminoglycoside combinations was studied in 16 strains of Group B streptococci. Minimal inhibitory concentrations (MIC) against kanamycin or gentamicin were greater than 50 microgram/ml, whereas ampicillin or penicillin inhibitory concentrations were uniformly less than 0.1 microgram/ml. Although all strains had bactericidal concentrations (MBC) less than 0.1 microgram penicillin/ml, penicillin at a concentration equal to each strains respective MBC reduced inoculum colony forming units (CFU) 2 logs in only 6 of 16 strains in bactericidal kinetic studies. However, the addition of gentamicin in concentrations of 5.0 or 10.0 microgram/ml to penicillin markedly enhanced bactericidal activity in all strains tested. The addition of lower concentrations of gentamicin (1.0 microgram/ml) had minimal advantage over penicillin alone. No distinct advantage was noted for combinations including either ampicillin or kanamycin. The theoretical advantage of penicillin-aminoglycoside combinations in experimental conditions, suggests that the use of antibiotic combinations in clinical infections due to Group B streptococci, may result in a more rapid eradication of these organisms.

Cerebrospinal fluid endotoxin concentrations in gram-negative bacterial meningitis

The limulus lysate assay was utilized to detect and quantitate endotoxin in cerebrospinal fluid from 232 patients with suspected meningitis. The assay was positive in initial specimens of CSF from all 86 patients with gram-negative bacterial meningitis and was uniformly negative in the remaining 146 patients with a variety of infectious and noninfectious processes. Endotoxin concentrations in initial specimens of CSF from patients with gram-negative meningitis ranged from 4 to 2,000 ng/ml. No correlation between initial CSF levels of endotoxin and initial clinical or laboratory variables of infection was noted. With antibiotic therapy, CSF concentrations of endotoxin fall rapidly to undetectable levels after five days.