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BACKGROUND The optimal sequencing ofantiretroviral regimens for the treatment of infection with human immunodeficiency virus type 1 (HIV-1) is unknown. We compared several different antiretroviral treatment strategies. METHODS This multicenter, randomized, partially double-blind trial used a factorial design to compare pairs of sequential three-drug regimens, starting with a regimen including zidovudine and lamivudine or a regimen including didanosine and stavudine in combination with either nelfinavir or efavirenz. The primary end point was the length of time to the failure ofthe second three-drug regimen. RESULTS A total of 620 subjects who had not previously received antiretroviral therapy were followed for a median of 2. 3 years. Starting with a three-drug regimen containing efavirenz combined with zidovudine and lamivudine (but not efavirenz combined with didanosine and stavudine) appeared to delay the failure ofthe second regimen, as compared with starting with a regimen containing nelfinavir (hazard ratio for failure ofthe second regimen, 0.71; 95 percent confidence interval, 0.48 to 1.06), as well as to delay the second virologic failure (hazard ratio, 0.56; 95 percent confidence interval, 0.29 to 1.09), and significantly delayed the failure ofthe first regimen (hazard ratio, 0.39) and the firstvirologic failure (hazard ratio, 0.34). Starting with zidovudine and lamivudine combined with efavirenz (but not zidovudine and lamivudine combined with nelfinavir) appeared to delay the failure of the second regimen, as compared with starting with didanosine and stavudine (hazard ratio, 0.68), and significantly delayed both the first and the second virologic failures (hazard ratio for the firstvirologic failure, 0.39; hazard ratio for the second virologic failure, 0.47), as well as the failure ofthe first regimen (hazard ratio, 0.35). The initial use of zidovudine, lamivudine, and efavirenz resulted in a shorter time to viral suppression. CONCLUSIONS The efficacy ofantiretroviral drugs depends on how they are combined. The combination of zidovudine, lamivudine, and efavirenz is superior to the other antiretroviral regimens used as initial therapy in this study.

The 24-week extension of AIDS Clinical Trials Group Protocol 359, a study of human immunodeficiency virus (HIV)‐infected, indinavir-experienced patients, was designed to study the durability of “salvage” treatment regimens. Patients received saquinavir in combination with either ritonavir or nelfinavir and, in addition, delavirdine, adefovir, or both. Patients who demonstrated a virologic response at weeks 12‐16 were eligible to continue therapy in the extension through week 48. Of the 105 eligible subjects who were enrolled in the extension, 86 (82%) completed 48 weeks, and 49 (57%) of those 86 had HIV RNA levels 500 copies/ mL at week 48. For these 86 subjects who completed 48 weeks, the median change in CD4 cell count from baseline was +72 cells/mm 3 . Greater body weight, higher CD4 cell count, and greater degree of phenotypic susceptibility to indinavir and saquinavir at baseline were significantly associated with durable virologic suppression. These results show that some patients who experience treatment failure can demonstrate durable virologic and immunologic responses with salvage antiretroviral regimens. Current treatment guidelines recommend starting therapy for human immunodeficiency virus (HIV) infection with 2 nucleoside analogue reverse-transcriptase inhibitors in combination with 1 or 2 protease inhibitors or a nonnucleoside analogue reversetranscriptase inhibitor [1, 2]. However, 20%‐63% of patients from clinical cohorts experience virologic treatment failure while receiving combination antiretroviral therapy [3‐7]. Recent prospective studies have attempted to identify strategies for treatment of the treatment-experienced patient [8‐13], but these studies have focused primarily on 8‐24-week virologic responses to treatment. The durability of virologic and immunologic re

This study compared antiretroviral activity among 6 salvage therapy regimens. The study was a prospective, randomized, 2 × 3 factorial, multicenter study of the AIDS Clinical Trials Group. The study enrolled 277 human immunodeficiency virus (HIV)-infected patients naive to nonnucleoside analogues who had taken indinavir >6 months. The patients had 2000-200,000 HIV RNA copies/mL. Patients received saquinavir with ritonavir or nelfinavir together with delavirdine andlor adefovir and were followed for safety and antiretroviral response between baseline and week 16. At week 16, 30% (77/254) of patients had ≤500 HIV RNA copies/mL. Virologic response did not differ significantly between pooled ritonavir and nelfinavir groups (28% vs. 33%; P =.50) or between pooled delavirdine and delavirdine/adefovir groups (40% vs. 33%; P =.42). Pooled delavirdine groups had a greater virologic response rate than did adefovir groups (40% vs. 18%; P =.002). Overall, one-third of patients who experienced virologic failure on an indinavir-containing regimen suppressed virus load levels while they were taking a new salvage regimen.

OBJECTIVE To compare the virologic activity of continued lamivudine (3TC) versus a switch to delavirdine (DLV) when initiating protease inhibitor therapy in nucleoside-experienced patients. DESIGN Randomized, open-label, multi-center study. SETTING Adult AIDS clinical trials units. PATIENTS Protease and non-nucleoside reverse transcriptase inhibitor-naive patients who had received 3TC plus zidovudine (ZDV), stavudine (d4T), or didanosine (ddl) for at least 24 weeks. INTERVENTIONS Patients with plasma HIV-1 RNA levels > 500 copies/ml who previously received d4T + 3TC or ddI + 3TC were randomized to ZDV + 3TC + indinavir (IDV) or ZDV + DLV + IDV. MAIN OUTCOME MEASURES Primary endpoints were the proportion of patients with plasma HIV-1 RNA levels < or = 200 copies/ml at 24 weeks, and occurrence of serious adverse events. The proportion of patients with plasma HIV-1 RNA levels < or = 200 copies/ml at week 48 was a secondary endpoint. RESULTS At week 24, 58% of subjects in the ZDV + 3TC + IDV arm and 73% in the ZDV + DLV + IDV arm had plasma HIV-1 RNA levels < or = 200 copies/ml (P = 0.29). At week 48, plasma HIV-1 RNA levels were < or = 200 copies/ml in 48% and 83%, respectively (P = 0.007). Rash and hyperbilirubinemia occurred more frequently in the DLV arm than in the 3TC arm. Steady-state plasma IDV levels were higher among patients in the DLV arm as compared with the 3TC arm. CONCLUSIONS Substituting DLV for 3TC when adding IDV improved virologic outcome in nucleoside-experienced patients. This result might be explained, in part, by the positive effect of DLV on IDV pharmacokinetics.

This paper summarizes the proceedings of an NIAID-sponsored workshop on statistical issues for HIV surrogate endpoints. The workshop brought together statisticians and clinicians in an attempt to shed light on some unresolved issues in the use of HIV laboratory markers (such as HIV RNA and CD4+ cell counts) in the design and analysis of clinical studies and in patient management. Utilizing a debate format, the workshop explored a series of specific questions dealing with the relationship between markers and clinical endpoints, and the choice of endpoints and methods of analysis in clinical studies. This paper provides the position statements from the two debaters on each issue. Consensus conclusions, based on the presentations and discussion, are outlined. While not providing final answers, we hope that these discussions have helped clarify a number of issues, and will stimulate further consideration of some of the highlighted problems. These issues will be critical in the proper assessment and use of future therapies for HIV disease.

Interleukin-2 (IL-2) can increase numbers of absolute CD4 cells in persons infected with the human immunodeficiency virus who are receiving antiretroviral therapy. Twenty-five subjects with400/mm3 absolute CD4 cells received zidovudine and low-dose intravenous or subcutaneous IL-2 (or = 10(6) U/m2). Absolute CD4 cells increased significantly during IL-2 treatment, and 56% of the subjects achieved a maximal increase ofor = 500 cells/mm3. A dose-response relationship favored increasing IL-2 doses, and subcutaneous delivery offered greater increases than intravenous administration. Fifteen subjects had persistent increases ofor = 100 cells/mm3 6 weeks after IL-2 was discontinued. No changes occurred in delayed-type hypersensitivity or helper T cell responses to recall antigens. Cell-mediated cytotoxicities increased against Daudi cells. IL-2 was well tolerated and only 1 subject required dose reduction. Relatively low-dose IL-2 delivered by subcutaneous or intravenous routes may provide an important complement to antiretroviral therapy to increase absolute CD4 cells with the potential for less toxicity than with higher IL-2 doses.

BACKGROUND We conducted a trial to compare treatment with zidovudine or didanosine in patients with advanced human immunodeficiency virus type 1 (HIV-1) infection who had received little or no previous therapy with zidovudine. METHODS Six hundred seventeen patients with acquired immunodeficiency syndrome (AIDS), advanced AIDS-related complex (CD4 cell count, < or = 0.30 x 10(9)/L [300/microL]), or asymptomatic HIV (CD4 cell count, < or = 0.20 x 10(9)/L) received zidovudine, 500 mg/d of didanosine, or 750 mg/d of didanosine in a randomized, double-blind allocation, with cross-over to alternative medication after development of an end point or serious toxic effect. To be eligible, patients must have received either no or up to 16 weeks of zidovudine therapy before entry into the study. Primary end points were development of a new AIDS-defining event or death. Secondary clinical end points were new or recurrent AIDS-defining events, or death, and survival. RESULTS In the study as a whole, there were no differences in the relative risks (RRs) of the development of end points between treatment groups. However, there was a strong interaction between the relative efficacies of zidovudine and didanosine and previous experience with zidovudine. Among 380 patients with no previous zidovudine therapy, zidovudine was more effective than 750 mg/d of didanosine (RR, 1.43; 90% confidence interval [CI], 1.02 to 2.00), with a similar trend for zidovudine compared with 500 mg/d of didanosine (RR, 1.21; 90% CI, 0.86 to 1.71). However, among 118 patients with more than 8 weeks but no more than 16 weeks of previous zidovudine therapy, 500 mg/d of didanosine was more effective than zidovudine (RR, 0.48; 90% CI, 0.27 to 0.86); there was a similar trend for increased effectiveness of 750 mg/d of didanosine compared with zidovudine (RR, 0.61; 90% CI, 0.36 to 1.03). Among 119 patients who had some but no more than 8 weeks of previous zidovudine therapy, there were no significant differences among the treatment arms. Similar findings were noted in the analysis of the two secondary clinical end points. No significant differences were found in efficacy between the groups receiving 500 and 750 mg/d of didanosine. The major toxic effect associated with zidovudine was hematopoietic (granulocytopenia) and that associated with didanosine was pancreatitis (dosage, 750 mg/d). CONCLUSIONS In patients with advanced HIV disease, zidovudine appears to be more effective than didanosine as initial therapy; however, some patients with advanced HIV disease may benefit from a change to didanosine therapy after as little as 8 to 16 weeks of therapy with zidovudine.

Background. Although zidovudine is effective in patients with human immunodeficiency virus (HIV) infection, its efficacy may decline with prolonged use. Didanosine is another inhibitor of HIV reverse transcriptase. We evaluated the effectiveness of changing anti-HIV treatment from zidovudine to didanosine. Methods. This multicenter, double-blind study involved 913 patients who had tolerated zidovudine for at least 16 weeks. The patients had the acquired immunodeficiency syndrome (AIDS), AIDS-related complex with ≤300 CD4 cells per cubic millimeter, or asymptomatic HIV infection with ≤200 CD4 cells per cubic millimeter. They were randomly assigned to receive 600 mg per day of zidovudine, 750 mg per day of didanosine, or 500 mg per day of didanosine. Results. There were significantly fewer new AIDS-defining events and deaths among the 298 subjects assigned to 500 mg per day of didanosine than among the subjects who continued to receive zidovudine (relative risk, 1.39; 95 percent confidence interval...

Antiretroviral therapy in early HIV infection may enhance outcome and viral control may be better in acute versus recent infection 24 weeks after treatment interruption.A prospective trial of treatment stratified by acute versus recent HIV-1 infection. If HIV viral load50 copies/ml after at least 52 weeks, treatment was interrupted. If viremia rebounded, treatment and interruption were repeated. The primary endpoint was maintaining viral load less than 5000 copies/ml for 24 weeks following treatment interruption.Of the 121 patients enrolled at 15 sites, ninety-five percent were men, median age was 34 years; 69% were white. Median viral load was higher in acute HIV-1 infection (210 000 copies/ml) than recent HIV-1 infection (43 000 copies/ml). The 73 primary endpoint patients (28 acute HIV-1 infection, 45 recent HIV-1 infection) had significantly higher baseline CD4 T-cell counts (P = 0.044) and lower viral load (P = 0.016). The primary endpoint was achieved in 29 (40%) of the 73 and in 24% of the 121 enrolled overall. There was no significant outcome difference (P = 0.81) between the acute HIV-1 infection [43%, 95% confidence interval (CI) 24-63%] and recent HIV-1 infection (38%, 95% CI 24-53%) groups. Differences after longer follow-up can not be ascertained by this trial. Baseline viral load less than 100 000/ml 22/46 (48%) compared with more than 100 000/ml, 7/27 (26%) and higher baseline CD4 immune activation predicted success.Forty percent of patients treated during acute HIV-1 infection or recent HIV-1 infection sustained a viral load less than 5000 copies/ml after 24 weeks of treatment interruption.

Background. The initially tested dose of zidovudine for the treatment of patients with advanced disease caused by the human immunodeficiency virus type 1 (HIV) was 1500 mg. Although this dose is effective, it is associated with substantial toxicity. Methods. To evaluate the efficacy and safety of a reduced dose, we conducted a randomized controlled trial in 524 subjects who had had a first episode of Pneumocystis carinii pneumonia. The subjects were assigned to receive zidovudine in either a dose of 250 mg taken orally every four hours (the standard-treatment group, n = 262) or a dose of 200 mg taken orally every four hours for four weeks and thereafter 100 mg taken every four hours (the low-dose group, n = 262). Results. The median length of follow-up was 25.6 months. At 18 months the estimated survival rates were 52 percent for the standard-treatment group and 63 percent for the low-dose group (P = 0.012 by the log-rank test). At 24 months the estimated survival rates were 27 percent for the st...

Zidovudine delays the progression of human immunodeficiency virus (HIV) infection but is associated with hematologic toxicity at high doses. Regimens are needed that preserve or enhance efficacy and reduce toxicity. Acyclovir has been reported to potentiate the effect of zidovudine on HIV in vitro.We conducted a Phase II open-label, dose-escalating trial to evaluate the clinical and antiviral effects of zidovudine at low (300 mg daily, 28 subjects), medium (600 mg, 24 subjects), and high (1500 mg, 15 subjects) doses, either with or without acyclovir (4.8 g) by random assignment. The subjects had the acquired immunodeficiency syndrome (AIDS)-related complex, but not AIDS. All of them had either HIV p24 antigenemia or plasma viremia and CD4-lymphocyte counts of 200 to 500 per cubic millimeter when they began treatment.Performance scores and fatigue improved the most in the low- and medium-dose zidovudine groups (both P less than or equal to 0.025). Those assigned to low-dose zidovudine gained the most weight and had the greatest improvement in the mean CD4-lymphocyte count (from 321 per cubic millimeter at base line to 412 per cubic millimeter after 12 weeks, P = 0.01). The proportion of subjects in whom HIV antigenemia resolved, the decrease in the level of antigenemia, and the reduction in the plasma virus titers were similar at all three doses. Subjects assigned to receive the low or medium dose who subsequently crossed over to the 1500-mg dose (n = 19) did not have an increase in CD4-cell counts or a decline in levels of HIV antigen, but they did have dose-related toxicity. The addition of acyclovir to zidovudine was well tolerated, but it did not enhance any of zidovudine's antiretroviral effects.In this pilot study a very low dose of zidovudine (300 mg) had clinical and virologic effects similar to those of higher daily doses (600 and 1500 mg). The minimal effective dose of zidovudine for the treatment of HIV infection has yet to be determined, and further studies of very low daily doses are warranted.

Twenty-one patients with AIDS or AIDS-related complex (ARC) received 2',3'-dideoxyinosine (didanosine; ddI) intravenously and then orally (initial dosages of 0.4 mg/kg and 0.8 mg/kg every 12 hours, respectively) for 6-44 weeks in an escalating-dose study. The major dose-limiting effects were peripheral neuropathy (three patients) and pancreatitis (two patients), which were observed at dosages greater than or equal to 20 mg/(kg.d). Hyperuricemia occurred at greater than or equal to 30 mg/(kg.d). No hematologic toxicity developed except for possible sporadic thrombocytopenia (two patients). Significant decreases in serum levels of p24 antigen and increases in CD4+ and CD8+ lymphocytes were noted at 2, 6, and 10-20 weeks and over a wide range of dosages, including the lowest given. Most patients had an increased feeling of well-being and/or a weight gain of greater than or equal to 2 kg at 6 weeks. For this population, ddI has promise as a therapeutic agent, thus warranting further study of this agent in controlled clinical trials.

Zidovudine (AZT) is a potent inhibitor of the replication of the human immunodeficiency virus (HIV), and it has been shown to improve survival in advanced HIV disease. We conducted a randomized, double-blind trial in adults with asymptomatic HIV infection who had CD4+ cell counts of fewer than 500 per cubic millimeter on entry into the study. The subjects (92 percent male) were randomly assigned to one of three treatment groups: placebo (428 subjects); zidovudine, 500 mg per day (453); or zidovudine, 1500 mg per day (457). After a mean follow-up of 55 weeks (range, 19 to 107), 33 of the subjects assigned to placebo had the acquired immunodeficiency syndrome (AIDS), as compared with 11 of those assigned to receive 500 mg of zidovudine (P = 0.002; relative risk, 2.8; 95 percent confidence interval, 1.4 to 5.6) and 14 of those assigned to receive 1500 mg of zidovudine (P = 0.05; relative risk, 1.9; 95 percent confidence interval, 1.0 to 3.5). In the three treatment groups, the rates of progression (per 100 person-years) to either AIDS or advanced AIDS-related complex were 7.6, 3.6, and 4.3, respectively. As compared with those assigned to placebo, the subjects in the zidovudine groups had significant increases in the number of CD4+ cells and significant declines in p24 antigen levels. In the 1500-mg zidovudine group, severe hematologic toxicity (anemia or neutropenia) was more frequent than in the other groups (P less than 0.0001). In the 500-mg zidovudine group, nausea was the only toxicity that was significantly more frequent (in 3.3 percent) than in the placebo group (P = 0.001). We conclude that zidovudine is safe and effective in persons with asymptomatic HIV infection and fewer than 500 CD4+ cells per cubic millimeter. Additional study will be required to determine whether such treatment will ultimately improve survival for persons infected with HIV.

Background: Pharmacokinetic enhancement of protease inhibitors (PIs) with low-dose ritonavir (RTV) for salvage therapy is increasingly common. The purpose of this study was to compare the pharmacokinetics, safety, and tolerability of indinavir (IDV)/RTV at 800/200 mg (arm A) and 400/400 mg (arm B) administered twice daily in HIV-infected subjects failing their first PI-based regimen. Methods: A phase I/II, randomized, open-label, 24-week study was conducted. Formal 12-hour pharmacokinetic evaluations were performed, and study visits occurred at baseline; at weeks 1, 2, and 4; and every 4 week thereafter for 24 weeks. Clinical symptoms and laboratory assessments were collected. Subjects were allowed to switch arms because of toxicity. Results: Forty-four subjects were enrolled (22 per arm). IDV pre-dose concentration, maximum plasma concentration and area under the curve were significantly higher in arm A. Fifty-five percent and 45% of subjects in arms A and B responded (

Objective To assess the toxicity, efficacy, and pharmacology of combined zidovudine and ganciclovir therapy in patients with the acquired immunodeficiency syndrome (AIDS) and serious cytomegalovirus (CMV) disease. Design Prospective, phase I multicenter trial (ACTG 004) with patients grouped by previous study drug history. Setting Three university-based AIDS Clinical Trials Units sponsored by the National Institute of Allergy and Infectious Diseases (NIAID). Patients Forty-one patients with AIDS-related CMV disease. Previous therapy with either zidovudine or ganciclovir was allowed. Interventions Patients were treated with zidovudine, 600 to 1200 mg/d; or, if on ganciclovir maintenance, ganciclovir, 5 mg/kg body weight; blood was sampled for pharmacokinetic studies. The other drug was then administered to the patient with blood sampling and, finally, the two drugs in combination were given. Patients were continued on both drug therapies with dose reduction of zidovudine only for grade 3 or 4 toxicity. Measurements and main results Forty patients were eligible. Hematologic toxicity was frequent, with 9 of the 10 patients requiring dose reductions for grade 3 or 4 toxicity at zidovudine doses of 1200 mg/d. With zidovudine doses of 600 mg/d, 82% experienced such hematologic toxicity. Median survival was 6 months; 10 patients developed intercurrent infection and 19, progressive CMV disease. Pharmacokinetic variables (alpha and beta half-lives, volume of distribution, clearance) were not affected in combination therapy. Conclusion The combination of zidovudine and ganciclovir is poorly tolerated in patients with AIDS and serious-CMV disease, with 82% developing severe to life-threatening hematologic toxicity. Such toxicity is not a result of pharmacologic interactions, drug metabolism, or excretion.

2',3'-Dideoxyinosine (ddI) is a purine analogue that after intracellular metabolic conversion suppresses the replication of the human immunodeficiency virus (HIV). We conducted a Phase I dose-escalation study of ddI in 17 patients with the acquired immunodeficiency syndrome (AIDS) and 20 patients with AIDS-related complex. The drug was administered twice daily over a dose range of 0.4 to 66 mg per kilogram of body weight per day for 2 to 44 weeks. The maximal tolerated oral dose of ddI was estimated to be 12 mg per kilogram per day. The major dose-limiting toxic effects were a painful peripheral neuropathy (in eight patients) and pancreatitis (in five). Asymptomatic elevations of the serum aminotransferase levels (in 13 patients) and the serum urate level (in 10) were also noted, but there was no dose-related hematologic toxicity. At the maximal tolerated dose, the peak plasma levels of ddI were 6.3 to 9.6 mumol per liter 0.6 to 1 hour after oral administration; the mean plasma half-life was 1.5 hours. The administration of ddI was associated with statistically significant decreases in serum level of p24 antigen and increases in the numbers of CD4 cells at 2, 6, 10, and 20 weeks. These changes were seen at all dose levels studied. Either a clinical improvement or a weight gain of greater than or equal to 2 kg was observed in 25 of 34 patients at six weeks. We conclude that ddI is a promising therapeutic agent in patients with AIDS or AIDS-related complex. Its efficacy is currently being evaluated in large-scale, controlled clinical trials.

Objective : To study the addition of a third human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor, nevirapine, to the combination of zidovudine and didanosine. Design : A 48-week, randomized, double-blind, placebo-controlled trial at 16 AIDS (acquired immunodeficiency syndrome) Clinical Trials Units. Patients : 398 adults who had HIV-1 infection, had 350 or fewer CD4 + T lymphocytes/mm 3 , and had had more than 6 months of previous nucleoside therapy. Intervention : 1) Either nevirapine or placebo (200 mg/d for 2 weeks, then 400 mg/d thereafter) and 2) open-label zidovudine (600 mg/d) and didanosine (400 mg/d for patients weighing ≥60 kg). Measurements : CD4 + T lymphocyte counts, time to first HIV-1 disease progression event or death, adverse events, and nevirapine levels in plasma samples taken at random were measured in all patients. Plasma levels of HIV-1 RNA ; HIV-1 infectivity titer in peripheral blood mononuclear cells ; serum p24 antigen levels ; and plasma levels of zidovudine and didanosine were measured in patients enrolled at half the study sites. Results : After 48 weeks of study treatment, the patients assigned to the triple-combination regimen (nevirapine, zidovudine, and didanosine) had an 18% higher mean absolute CD4 cell count (95% CI, 7% to 29% ; P = 0.001), a 0.32 log 10 lower mean infectious HIV-1 titer in peripheral blood mononuclear cells (CI, 0.05 to 0.59 log 10 infectious units per million cells ; P = 0.023), and a 0.25 log 10 lower mean plasma HIV-1 RNA level (CI, 0.03 to 0.48 log 10 RNA copies/mL ; P = 0.028) than did patients assigned to the double-combination regimen (zidovudine and didanosine). Severe rashes were more common among patients assigned to receive the triple combination (9% compared with 2% ; P = 0.002). Risk for disease progression did not differ between the two groups (relative hazard of the triple-combination group, 1.24 [CI, 0.75 to 2.06] ; P > 0.2), although the study had only moderate power to detect a major difference. Conclusions : Adding nevirapine to zidovudine and didanosine improved the long-term immunologic and virologic effects of therapy and was associated with severe rash among the patients studied, who had had extensive previous therapy. These results support 1) the continuing development of combinations of more than two antiretroviral drugs to increase and prolong HIV-1 suppression and 2) the potential utility of nevirapine in combination regimens.

Background: We conducted a trial to compare treatment with zidovudine or didanosine in patients with advanced human immunodeficiency virus type 1 (HIV-1) infection who had received little or no previous therapy with zidovudine. Methods: Six hundred seventeen patients with acquired immunodeficiency syndrome (AIDS), advanced AIDS-related complex (CD4 cell count, ≤0.30× 10 9 /L [300/μL]), or asymptomatic HIV (CD4 cell count, ≤0.20× 10 9 /L) received zidovudine, 500 mg/d of didanosine, or 750 mg/d of didanosine in a randomized, double-blind allocation, with cross-over to alternative medication after development of an end point or serious toxic effect. To be eligible, patients must have received either no or up to 16 weeks of zidovudine therapy before entry into the study. Primary end points were development of a new AIDS-defining event or death. Secondary clinical end points were new or recurrent AIDS-defining events, or death, and survival. Results: In the study as a whole, there were no differences in the relative risks (RRs) of the development of end points between treatment groups. However, there was a strong interaction between the relative efficacies of zidovudine and didanosine and previous experience with zidovudine. Among 380 patients with no previous zidovudine therapy, zidovudine was more effective than 750 mg/d of didanosine (RR, 1.43; 90% confidence interval [CI], 1.02 to 2.00), with a similar trend for zidovudine compared with 500 mg/d of didanosine (RR, 1.21; 90% CI, 0.86 to 1.71). However, among 118 patients with more than 8 weeks but no more than 16 weeks of previous zidovudine therapy, 500 mg/d of didanosine was more effective than zidovudine (RR, 0.48; 90% CI, 0.27 to 0.86); there was a similar trend for increased effectiveness of 750 mg/d of didanosine compared with zidovudine (RR, 0.61; 90% CI, 0.36 to 1.03). Among 119 patients who had some but no more than 8 weeks of previous zidovudine therapy, there were no significant differences among the treatment arms. Similar findings were noted in the analysis of the two secondary clinical end points. No significant differences were found in efficacy between the groups receiving 500 and 750 mg/d of didanosine. The major toxic effect associated with zidovudine was hematopoietic (granulocytopenia) and that associated with didanosine was pancreatitis (dosage, 750 mg/d). Conclusions: In patients with advanced HIV disease, zidovudine appears to be more effective than didanosine as initial therapy; however, some patients with advanced HIV disease may benefit from a change to didanosine therapy after as little as 8 to 16 weeks of therapy with zidovudine. (Arch Intern Med. 1995;155:961-974)

This document summarizes recommendations from a state-of-the-art conference convened to evaluate the role of nucleoside analogue reverse transcriptase inhibitors in the treatment of human immunodeficiency virus (HIV) infection. Data from controlled clinical trials of zidovudine, didanosine, and zalcitabine were reviewed by an expert panel, which then formulated guidelines to assist clinicians and HIV-infected patients in the use of these agents. Recommendations were framed in the context of clinical scenarios for patients with asymptomatic HIV infection who have not had prior antiretroviral therapy; those with signs and symptoms of HIV-related disease who have not received prior therapy; clinically stable patients who are tolerating initial zidovudine therapy; patients experiencing clinical progression while on zidovudine therapy; and those who are intolerant of antiretroviral therapy. The panel concluded that physicians need to integrate up-to-date scientific knowledge with other relevant needs to improve the care of HIV-infected patients. ( JAMA . 1993;270:2583-2589)

• Background.— Protocol 019 of the AIDS Clinical Trails Group is a multicenter, double-blind, placebo-controlled trial of zidovudine (3'-azido-3'-deoxythymidine; formerly AZT) in human immunodeficiency virus-infected asymptomatic individuals. The initial results in the stratum of subjects entering with CD4 + cell counts of 0.50×10 9 /L or less have been reported, but without a detailed a analysis of toxic effects. Methods.— This detailed and updated report analyzes the toxic effects that occurred in 1567 subjects (91% men; 89% white) in this stratum of protocol 019 who received placebo (494 subjects), a 500-mg daily dose of zidovudine (544 subjects), or a 1500-mg daily dose of zidovudine (529 subjects). Hematologic, hepatic, and renal effects and patientreported symptoms and clinical signs were monitored. Results.— Severe anemia (hemoglobin level, 6 /L) did not occur significantly more often in the 500-mg zidovudine group but did in the 1500-mg zidovudine group. Moderate neutropenia (absolute neutrophil count, 6 /L did develop significantly more often in the 500-mg zidovudine group (165 subjects) than in the placebo group (71 subjects). Mild (or worse) elevations of bilirubin levels were uncommon but occurred more often with zidovudine. Severe nausea (and/or vomiting) was rare (2.8% of subjects) but was associated with zidovudine. Milder patientreported events were common, and a number were associated with zidovudine. Conclusion.— Zidovudine at the 500-mg/d dosage appears to be tolerable in many patients with asymptomatic human immunodeficiency virus infection and CD4 + cell counts of 0.50 × 10 9 /L or less. Increased clinical surveillance for anemia may be warranted in certain patients. ( Arch Intern Med . 1992;152:2286-2292)

Objective To evaluate the efficacy and safety of zidovudine early in the treatment of human immunodeficiency virus type 1 (HIV) infection. Design A double-blind, randomized, placebo-controlled trial with subject stratification by pretreatment CD4 T lymphocyte counts. Setting Multicenter trial at AIDS Clinical Trial units. Subjects Seven hundred eleven subjects with mildly symptomatic HIV infection. Intervention Three hundred fifty-one subjects were assigned to placebo and 360 to zidovudine, 200 mg orally every 4 hours. The median duration of follow-up was 11 months. Measurements and main results Fifty-one subjects developed the acquired immunodeficiency syndrome (AIDS), advanced AIDS-related complex, or death as a first critical event. For the stratum of subjects with more than 200 but less than 500 CD4 T lymphocytes/mm3 before treatment, 34 events occurred in placebo recipients and 12 in zidovudine recipients (P = 0.0002; relative risk [RR] estimate, 3.23 [95% CI, 1.67 to 6.24]). For the stratum of subjects with 500 to 799 CD4 T lymphocytes/mm3 before treatment, 2 events occurred in placebo recipients and 3 in zidovudine recipients. Candidiasis at study entry independently increased the risk for having an event (P = 0.005; RR estimate, 2.3 [95% CI, 1.29 to 4.12]); HIV antigenemia at study entry also increased this risk (P = 0.01; RR estimate, 2.1 [95% CI, 1.2 to 3.8]). Significant differences between the treatment groups in CD4 T-lymphocyte counts occurred in subjects with more than 200 but less than 500 CD4 T lymphocytes/mm3 after 4 weeks of therapy (P = 0.002). Differences persisted through week 52. Less prominent changes occurred in subjects with 500 or more CD4 T lymphocytes/mm3. Serum levels of HIV antigen decreased significantly in zidovudine recipients. Serious anemia and neutropenia occurred in 5% and 4% of zidovudine recipients, respectively, and in 0% and 1% of placebo recipients, respectively. Conclusion Zidovudine delayed progression of HIV disease and produced little toxicity in subjects with mildly symptomatic HIV disease and less than 500 CD4 T lymphocytes/mm3.

Publisher Summary This chapter highlights the generation of trinitrophenyl (TNP) specific H-2-restricted murine cytotoxic cells as a function of TNP-cell surface presentation. The generation of the cytotoxic effectors sensitized by the addition of trinitrobenzene sulfonate-modified cells on TNP proteins is dependent on the presence of both T lymphocytes and a population of glass-adherent, radio resistant cells. The chemically modified H-2-restricted CML model may not depend on actual covalent conjugation of the TNP group to H-2-coded cell surface products and, therefore, could be similar to the H-2 -restricted viral and minor transplantation antigen models. These findings could also raise the possibility that H-2 -restricted cytotoxic immune reactions involving autoimmunity may be generated by soluble components associated with autologous cells. The analysis of the antigenicity and the immunogenicity of TNP-presenting cells as a target or stimulator for TNP-specific, H-2-restricted T-cell mediated cytotoxicity is summarized as a function of the mode of presentation of the TNP moiety on the cell surface.

To determine whether alternating regimens consisting of zidovudine and 2',3'-dideoxycytidine (ddC) reduce the toxicity and maintain or increase the antiretroviral effect associated with each drug alone.An unblinded, randomized (phase II) clinical trial in which seven treatment regimens were compared.Outpatient clinics of 12 AIDS Clinical Trials Units.One hundred thirty-one patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex and serum p24 antigenemia (or = 70 pg/mL).Treatments included weekly or monthly alternating zidovudine (200 mg every 4 hours) and ddC (0.01 or 0.03 mg/kg body weight every 4 hours); weekly intermittent zidovudine, 200 mg every 4 hours, or ddC, 0.03 mg/kg every 4 hours; and continuous zidovudine.Toxicity, CD4 cell counts, serum p24 antigen levels, and clinical end points. Data were analyzed for the first 48 weeks of therapy (median follow-up, 40 weeks).Hematologic toxicity was significantly less frequent in patients who received zidovudine therapy every other week (11% to 15%) or every other month (11% to 14%) than in those who received continuous zidovudine therapy (33%) (P0.02). Weekly alternating therapy with zidovudine and ddC, 0.03 mg/kg, or intermittent therapy with ddC, 0.03 mg/kg, produced high rates of peripheral neuropathy (41% and 50%, respectively). Neuropathy occurred in 10% to 21% of patients in the other three alternating-therapy limbs and in 17% of patients receiving zidovudine alone (intermittently or continuously). Initial increases in CD4 cell counts were sustained in three alternating-therapy limbs, but counts returned to baseline by week 28 in the remaining limbs. The median weight gain at week 48 was significantly greater in patients treated with alternating regimens (0.9 to 3.8 kg) compared with those treated with continuous zidovudine therapy (-0.7 kg) (P = 0.008). Patients treated with alternating regimens and those treated with continuous zidovudine had similarly sustained decreases in p24 antigen levels.These findings suggest that alternating therapy with zidovudine and ddC reduces the toxicity associated with each drug alone while maintaining strong antiretroviral activity.