A randomized controlled trial of a reduced daily dose of zidovudine in patients with the acquired immunodeficiency syndrome. The AIDS Clinical Trials Group

Treatment of HIV infection: the antiretroviral nucleoside analogues. Nucleoside analogues: adverse effects

The three approved nucleoside analogues are fairly well tolerated, and only a few patients have to discontinue therapy permanently. However, because clinical experience is limited, especially with ddI and ddC, delayed toxicities are likely to emerge over time. In addition, physicians should be vigilant for overlapping toxicities from combination therapy with these and other medications.

Treatment of HIV infection: the antiretroviral nucleoside analogues. Nucleoside analogues: monotherapy

At present, the nucleoside analogues are the cornerstone of therapy for HIV infection. Of the three that have been approved for clinical use, AZT is the only one that has clearly proved to prolong survival. ddI is indicated for patients who develop toxicity or resistance to AZT. Current data do not support ddC monotherapy as first-line treatment.

Compliance with zidovudine therapy in patients infected with human immunodeficiency virus, type 1: a cross-sectional study in a municipal hospital clinic

PURPOSE

To determine the extent of and clinical variables associated with zidovudine compliance.

PATIENTS AND METHODS

A survey of 83 patients infected with human immunodeficiency virus (HIV) followed in a municipal hospital clinic was performed. Compliance histories were validated by serum and urine zidovudine levels. Patient characteristics included 46% white, 63% with a history of intravenous drug use, and 59% reporting a diagnosis of acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). The main outcome measure was greater than 80% compliance with prescribed doses of zidovudine over the previous week.

RESULTS

Sixty-seven percent of the study patients reported greater than 80% compliance with prescribed doses of zidovudine over the previous week. The most common explanations given for missing a dose were "forgot to take zidovudine" and "did not have the medication with me." Five variables were independently associated with greater than 80% compliance as determined by stepwise multiple logistic regression: patient belief that zidovudine prolongs life (odds ratio [OR] 9.3, [95% confidence interval (CI) 2.4, 36.7]), a diagnosis of AIDS or ARC (OR 5.5, [CI 1.5, 20.4]), use of a medication timer (OR 4.4, [CI 1.0, 19.1]), no history of intravenous drug use (OR 3.7, [CI 1.0, 14.2]), and taking one to three other medications with zidovudine.

CONCLUSIONS

High compliance with zidovudine was achieved by HIV-infected patients in a municipal hospital clinic, many of whom had a history of intravenous drug use. Compliance with zidovudine may be enhanced by a patient's belief that it prolongs life and the use of a medication timer for proper dosing.

In vitro inhibition of human immunodeficiency virus (HIV) type 1 replication by C2 symmetry-based HIV protease inhibitors as single agents or in combinations

C2 symmetry-based human immunodeficiency virus (HIV) protease inhibitors were examined in vitro as single agents or in combination with 3'-azido-2',3'-dideoxythymidine (AZT) or 2',3'-dideoxyinosine for activity against HIV type 1 (HIV-1). Ten C2 symmetry-based or pseudo-C2 symmetry-based HIV protease inhibitors were active against a laboratory strain (HIV-1IIIB) in the HIV-1 cytopathic effect inhibition assay. Three inhibitors, A75925, A76928, and A77003, selected to represent a range of aqueous solubility and antiviral activity, were active against four different HIV-1 strains tested. These three inhibitors exhibited a significant inhibition of the cytopathic effect of HIV-1 against the CD4+ ATH8 cell line, with 90% inhibitory concentrations ranging from 0.1 to 4 microM. Cellular toxicity was negligible at up to 20 microM. Furthermore, they completely inhibited the replication of monocytotropic strain HIV-1Ba-L in purified monocytes and macrophages at 0.75 to 2 microM. Potent inhibitory activity against a primary HIV-1 isolate and an AZT-resistant HIV-1 variant was also observed for all three inhibitors in phytohemagglutinin-activated peripheral blood mononuclear cells. When these three HIV protease inhibitors and AZT or 2',3'-dideoxyinosine were used in combinations against a primary HIV isolate in phytohemagglutinin-activated peripheral blood mononuclear cells and the results were analyzed with the COMBO program package, their antiviral activities were identified to be synergistic in some cases and additive in others. The present data warrant further investigations of these compounds as potential antiviral agents for the therapy of HIV infections.

Improved outcome of Pneumocystis carinii pneumonia in AIDS patients: a multifactorial treatment effect

Factors determining the outcome of an episode of Pneumocystis carinii pneumonia (PCP) in 149 AIDS patients treated at St Mary's Hospital were identified and their importance on improved survival evaluated between 1984 and 1989. The proportion of fatal episodes of PCP decreased over time. Fatal compared with nonfatal episodes had lower mean alveolar-arterial oxygen gradient (82.5 mmHg vs 53.8 mmHg, P less than 0.001), mean haemoglobin level (11.2 g/dl vs 12.1 g/dl, P = 0.01), mean lymphocyte count (0.68 x 10(9)/l vs 0.92 x 10(9)/l, P = 0.05) and more coinfections (31% vs 5%, P less than 0.001). Over time, the most significant change which occurred was a reduction in alveolar-arterial oxygen gradient at time of first presentation with PCP (r = -0.37, P less than 0.001). Mean alveolar-arterial oxygen gradient declined from 79.9 mmHg in 1984 to 45.3 mmHg in 1989 (r = -0.88, P = 0.02), independently of zidovudine therapy or PCP prophylaxis. Patients were being treated at an earlier stage in their disease course as indicated by their reduced alveolar arterial oxygen gradient. This is due either to earlier patient presentation, earlier medical diagnosis or both. The widespread introduction of zidovudine and PCP prophylaxis may further contribute to improve morbidity and mortality patterns in the future.

A theoretical analysis of interval drug dosing for cell-cycle-phase-specific drugs

A formal method is provided for predicting the effect on treatment efficacy of cell-cycle-phase-specific drugs, such as the AIDS drug zidovudine (AZT) or the cancer drug cytosine arabinoside (ara-C). Our analysis shows that the elimination of somatic cells or viruses depends not only on the drug's pharmacokinetic and pharmacodynamic properties, but also the duration of the dosing interval per se and on the life-cycle parameters, that is, the duration of the drug-susceptible life phase, the duration of the whole life cycle, and the proliferation rate. The results support those of simplified models in showing that drug toxicity to the host may be minimized when the dosing interval is an integer multiple of the average cycle time of the host susceptible cells. This prediction has been verified in mice treated with AZT or ara-C.

Antiviral therapy: current concepts and practices

Drugs capable of inhibiting viruses in vitro were described in the 1950s, but real progress was not made until the 1970s, when agents capable of inhibiting virus-specific enzymes were first identified. The last decade has seen rapid progress in both our understanding of antiviral therapy and the number of antiviral agents on the market. Amantadine and ribavirin are available for treatment of viral respiratory infections. Vidarabine, acyclovir, ganciclovir, and foscarnet are used for systemic treatment of herpesvirus infections, while ophthalmic preparations of idoxuridine, trifluorothymidine, and vidarabine are available for herpes keratitis. For treatment of human immunodeficiency virus infections, zidovudine and didanosine are used. Immunomodulators, such as interferons and colony-stimulating factors, and immunoglobulins are being used increasingly for viral illnesses. While resistance to antiviral drugs has been seen, especially among AIDS patients, it has not become widespread and is being intensely studied. Increasingly, combinations of agents are being used: to achieve synergistic inhibition of viruses, to delay or prevent resistance, and to decrease dosages of toxic drugs. New approaches, such as liposomes carrying antiviral drugs and computer-aided drug design, are exciting and promising prospects for the future.

New drug treatments for HIV infection and AIDS. A review following the Seventh International Conference on AIDS, Florence 16-21 June 1991

1. OBJECTIVE--To evaluate the status of clinical development of zidovudine and new drugs for the treatment of Human Immunodeficiency Virus (HIV) infections. 2. METHOD--A critical review of the clinical trial reports and assessment of the design and methodology of the therapeutic trials. Evaluation of the drugs being tested and of the specific difficulties in testing drugs in AIDS. 3. CONCLUSIONS--Drugs are being tested in a unique climate of public opinion characterised by (1) fast track criteria for regulatory approval (2) parallel track (compassionate release) of new drugs before adequate determination of safety and efficacy (3) resistance to the use of placebos in controlled trials.

A controlled trial of early versus late treatment with zidovudine in symptomatic human immunodeficiency virus infection. Results of the Veterans Affairs Cooperative Study

BACKGROUND

Zidovudine is recommended for asymptomatic and early symptomatic human immunodeficiency virus (HIV) infection. The best time to initiate zidovudine treatment remains uncertain, however, and whether early treatment improves survival has not been established.

METHODS

We conducted a multicenter, randomized, double-blind trial that compared early zidovudine therapy (beginning at 1500 mg per day) with late therapy in HIV-infected patients who were symptomatic and had CD4+ counts between 0.2 x 10(9) and 0.5 x 10(9) cells per liter (200 to 500 per cubic millimeter) at entry. Those assigned to late therapy initially received placebo and began zidovudine when their CD4+ counts fell below 0.2 x 10(9) per liter (200 per cubic millimeter) or when the acquired immunodeficiency syndrome (AIDS) developed.

RESULTS

During a mean follow-up period of more than two years, there were 23 deaths in the early-therapy group (n = 170) and 20 deaths in the late-therapy group (n = 168) (P = 0.48; relative risk [late vs. early], 0.81; 95 percent confidence interval, 0.44 to 1.59). In the early-therapy group, 28 patients progressed to AIDS, as compared with 48 in the late-therapy group (P = 0.02; relative risk, 1.76; 95 percent confidence interval, 1.1 to 2.8). Early therapy increased the time until CD4+ counts fell below 0.2 x 10(9) per liter (200 per cubic millimeter), and it produced more conversions from positive to negative for serum p24 antigen. Early therapy was associated with more anemia, leukopenia, nausea, vomiting, and diarrhea, whereas late therapy was associated with more skin rash.

CONCLUSIONS

In symptomatic patients with HIV infection, early treatment with zidovudine delays progression to AIDS, but in this controlled study it did not improve survival, and it was associated with more side effects.

Antiviral agents

In recent years, the antiviral armamentarium has expanded considerably. Currently available agents are virustatic, inhibiting specific steps in the process of viral replication. No agent is active against nonreplicating or latent viruses. Acyclovir is useful in the treatment of genital herpes, herpes simplex encephalitis, mucocutaneous herpetic infection, varicella infection in the immunosuppressed host, and herpes zoster infection in the normal and the immunosuppressed host. It can also be used for prevention of herpesvirus infection in immunocompromised patients. Ganciclovir is indicated for the treatment of cytomegalovirus retinitis in patients with acquired immunodeficiency syndrome (AIDS) and is effective in the management of organ-specific cytomegalovirus infection in other immunocompromised patients. Chronic hepatitis C and condyloma acuminatum due to human papillomavirus respond to therapy with interferon alfa-2b. Patients with human immunodeficiency virus infection and CD4 lymphocyte counts of less than 500 cells/mm3 should be treated with zidovudine. Amantadine is useful in a therapeutic and prophylactic role in the management of influenza A virus infection. With the expanded use of and indications for antiviral therapy, clinically significant resistance to these agents has been encountered with increasing frequency.

Double blind dose-response study of zidovudine in AIDS and advanced HIV infection. Nordic Medical Research Councils' HIV Therapy Group

OBJECTIVE

To compare the efficacy and side effects of 400 mg, 800 mg, and 1200 mg zidovudine daily in patients with AIDS or advanced HIV infection.

DESIGN

Randomised, double blind, parallel group multicentre study.

SETTING

Hospital departments of infectious diseases and dermatology in Denmark, Sweden, Norway, Finland, and Iceland.

SUBJECTS

474 patients: 126 (27%) with AIDS; 248 (52%) with HIV related symptoms; 100 (21%) with low CD4+ cell counts.

INTERVENTIONS

Zidovudine 400 mg (160 patients), 800 mg (158), or 1200 mg (156) daily. All patients received one capsule from each of three bottles four times daily.

MAIN OUTCOME MEASURES

Survival; incidence of new HIV related events; CD4+ cell count; quality of life; incidence of haematological side effects.

RESULTS

460 (97%) of the 474 patients had not received zidovudine previously. The median follow up period was 19 months, during which the death rates in the three treatment groups were 23% (36/160 patients), 23% (36/158), and 19% (30/156) respectively (p = 0.49; log rank test). One year after the trial was terminated the death rates were 38% (61/160), 41% (64/158), and 44% (68/156) respectively (p = 0.54). There was no significant difference between the groups in time to a new AIDS defining event or death, average number of events per patient, decline in CD4+ cell counts, wellbeing (visual analogue scale), or Karnofsky score. Zidovudine was withdrawn in 132 (28%) patients, mainly because of side effects (71 cases; 15%). The incidences of anaemia and leucopenia, time to first dose reduction, and numbers of patients withdrawn were all dose related.

CONCLUSION

Zidovudine should be limited to 400-600 mg daily in patients with AIDS or advanced HIV infection.

Nail pigmentation associated with zidovudine: a review and report of a case

Zidovudine has become the standard therapy for patients with AIDS and for asymptomatic HIV infected patients with low helper-T-cell levels. As experience with the drug has grown, knowledge of the range of side effects has increased. We describe progressive pigmentation of finger and toe nails in a white patient due to zidovudine therapy, a phenomenon not often described. Nail pigmentation occurs primarily in black patients. It appears to be reversible and relatively dose dependent. The mechanism responsible for the discoloration is unknown. It is important to alert patients to this side effect and to prevent unnecessary investigations and treatment for other diagnoses, such as cyanosis.

The management of HIV-related illness in the emergency department

As the AIDS epidemic progresses, the number of ED patients with HIV-related illness will continue to increase. As reviewed in this article, much of the existing clinical research in HIV-related illness has an impact on the diagnostic and management issues that arise in the ED. Many of the patterns of disease, subtleties of diagnosis, and therapies unique to AIDS patients have already been greatly elucidated. However, as the recognition of this disease goes into only its second decade, many questions remain. Further studies are needed, for example, to improve physician assessment of HIV risk, to further identify discriminators of PCP and bacteremia, and to optimize strategies for disposition and outpatient management. In the future, in the areas of research and clinical care, emergency medicine will play an increasing important role in the front-line attack on this modern epidemic.

Intracellular metabolism of 3'-azidothymidine in isolated human peripheral blood mononuclear cells

Azidothymidine (AZT) inhibits the replication of human immunodeficiency virus and it is the only drug so far licensed for treatment of acquired immunodeficiency syndrome (AIDS). A prerequisite for its antiviral activity is phosphorylation by cellular nucleoside kinases to the mono-, di-, and triphosphate levels. This study determined the capacity of isolated peripheral blood mononuclear cells (PBMC), resting or mitogen stimulated, from 36 different people of whom 5 were HIV+, to phosphorylate and accumulate intracellular AZT nucleotides. We found a large variation in the amount of products formed between PBMC treated at different times from the same individual as well as between the PBMC from different individuals. Resting PBMC showed the largest interindividual variation and their levels of AZT nucleotides were about 60-150-fold lower than in activated PBMC. The intracellular half lives of azidothymidine mono-, di-, and triphosphates, constituting, on the average, 96-99.2, 0.7-1.8, and 0.4-2.7% of total nucleotides at 0.08-1.6 microM AZT, respectively, were also determined. In mitogen-stimulated PBMC it was approximately 2.5 +/- 0.6 h for all the azidothymidine metabolites. The half-life for intracellular azidothymidine monophosphate in resting PBMC from two individuals was determined to 1.5 +/- 0.2 h. There appeared to be no significant difference in the AZT metabolism in PBMC from HIV-positive or-negative persons. A relative decrease in the intracellular formation of AZTDP and AZTTP from AZTMP was observed at concentrations of AZTMP above 1 microM. This fact may explain why lowering the doses of AZT still gives therapeutically efficient levels of the active metabolite AZTTP.

A sensitive nonisotopic method for the determination of intracellular azidothymidine 5'-mono-, 5'-di-, and 5'-triphosphate

In order to analyze the efficacy of azidothymidine (AZT), it is important to know intracellular concentrations of AZT metabolites. However, it has been impossible to measure intracellular AZT 5'-monophosphate (AZT-MP), AZT 5'-diphosphate (AZT-DP), and AZT 5'-triphosphate (AZT-TP) without using isotopes. In the present study, we developed a new method to measure intracellular AZT metabolites without radiolabeled compounds. The method employed was a high-performance liquid chromatography (HPLC) system programmed for column switching technique, in which two columns were used: column 1 (TSK-G2000-SW, 300 x 7.5 mm) to preseparate AZT metabolites from major cell components, and column 2 (YMC-A-312-ODS, 150 x 6 mm) to determine the metabolites. The limit of detectability of this system was 3.3 pmol/injection. When MT-4 cells were incubated with various concentrations of AZT, intracellular concentrations of AZT-MP increased in parallel with extracellular AZT. Those of AZT-DP and AZT-TP, however, reached plateaus at 5 and 2 microM of AZT, respectively. In MT-4 and Molt-4 cells incubated with 5 microM AZT, concentrations of AZT-MP increased time dependently, while the AZT-DP/AZT-MP ratios decreased with time. These data suggest that high dose of AZT may not necessarily increase intracellular concentration of AZT-TP. The concentrations of AZT metabolites in peripheral blood mononuclear cells in a patient with AIDS and an asymptomatic carrier were measured; the concentrations were comparable to those in cultured cells. Quantitative analysis of intracellular AZT metabolites without the use of isotopes will increase safety and convenience of measurement, and take an effective step in studying pharmacokinetics of AZT in clinical materials.

HIV/AIDS pathogenesis and treatment: new twists and turns

This review focuses on some new insights into human immunodeficiency virus pathogenesis, as it affects CD4 lymphocytes and other key cells in the immune system. It also critically reviews recent progress in anti-retroviral therapy.

Remarkable improvement of neuropsychiatric symptoms in HIV-infected patients after AZT therapy

Treatment of neuropsychiatric symptoms with AZT (Azidothymidine) seems to be effective in many AIDS patients. In earlier studies, 204 of 525 patients treated with AZT showed neuropsychiatric improvement. In this presentation, two patients with affective disorder and dementia are described. Both patients showed remarkable improvement of their severe psychiatric symptoms after AZT. The authors recommend treatment of AIDS-associated dementia and psychoorganic symptoms with AZT.

Inhibition of immune functions by antiviral drugs

Immune functions were evaluated in vitro for PBMC isolated from healthy donors and cultured with the antiviral agents, 3'-azido-3'-deoxythymidine (AZT), ribavirin, ganciclovir, 2'3'-dideoxyinosine (ddI), or acyclovir. To identify methods for assessing the effects of antiviral drugs on immune cells, the PBMC response to mitogens, Con A, or phytohemagglutinin was evaluated from measurements of [3H]thymidine and [14C]-leucine incorporation, cell growth, cellular RNA, DNA, and protein levels, and the PBMC proliferative cycle (i.e., progression from G0----G1----S----G2 + M). At clinically relevant concentrations, AZT, ribavirin, or ganciclovir diminished PBMC responsiveness to mitogen. The numbers of proliferating cells in G1, S, and G2 + M phases of the cell cycle, DNA content, and [3H]thymidine uptake were decreased in cultures treated with AZT, ribavirin, or ganciclovir. AZT or ribavirin but not ganciclovir reduced RNA and protein in the cultures and inhibited cell growth. Whereas AZT, ribavirin, or ganciclovir were antiproliferative, ddI or acyclovir had little, if any, effect on PBMC mitogenesis. The inhibitory effects of antivirals on immune cells may contribute to the immune deterioration observed in patients following prolonged use of the drugs.

Synergistic inhibition of human immunodeficiency virus type 1 (HIV-1) replication in vitro by 1-[(2-hydroxyethoxy)methyl]-6-phenylthiothymine (HEPT) and recombinant alpha interferon

1-[(2-Hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) has recently proved to be a potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) in vitro. Combinations of HEPT and recombinant alpha interferon (IFN-alpha) synergistically inhibit the replication of HIV-1 in MT-4 cells at non-toxic concentrations. Synergistic inhibition of HIV-1 replication has also been observed in peripheral blood lymphocytes. These results indicate that the combination of HEPT with IFN-alpha should be further pursued in the treatment of retrovirus infections [i.e. acquired immune deficiency syndrome (AIDS)].

Antiretroviral therapy in combination with interferon for AIDS-related Kaposi's sarcoma

In vitro studies have shown that 3'-azido-3'-deoxythymidine (zidovudine, AZT) and interferon synergistically inhibit the replication of the human immunodeficiency virus type 1 (HIV) in peripheral blood mononuclear cells at concentrations achievable in patients. Interferon alfa can cause lesions to regress in patients with acquired immunodeficiency syndrome (AIDS)-related Kaposi's sarcoma (KS). Although zidovudine has no significant effect on the regression of these lesions, it does have antiviral activity in these patients as manifested by a decline in serum HIV antigen. However, when used separately, the two drugs can have serious side effects in some patients. In addition, the development of zidovudine-resistant strains has been noted in patients with advanced HIV disease receiving zidovudine for nine months or longer. Three in vivo trials have been initiated to assess possible advantages of combination therapy with zidovudine and interferon alfa in patients with AIDS-related KS. The incidence of serious adverse reactions, therapeutic efficacy, and the rate of emergence of zidovudine-resistant strains of HIV were evaluated. Preliminary results indicate that combination therapy with interferon alfa and zidovudine can safely be administered to patients with AIDS-related KS in doses that elicit antitumor and antiviral responses and discourage the potential emergence of zidovudine-resistant HIV strains.

Low-dose co-trimoxazole for prevention of Pneumocystis carinii pneumonia in human immunodeficiency virus disease

The efficacy and tolerability of low, intermittent doses of co-trimoxazole (160 mg trimethoprim and 800 mg sulfamethoxazole given Monday, Wednesday, Friday) for prophylaxis against Pneumocystis carinii pneumonia (PCP) was assessed retrospectively in 116 patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex at high risk of PCP. 92% were receiving concomitant zidovudine. 71 with previous episode(s) of PCP were followed a mean of 18.5 months (range 3-42). 45 without past PCP but with depletion of CD4 cells to less than 200/microliters were observed for a mean of 24.2 months (range 9-40). PCP did not develop in any patient on co-trimoxazole. 33 (28%) had side-effects, mainly rash, pruritus, and nausea. 15 discontinued co-trimoxazole, but only 11 (9%), who withdrew in the first month, were clearly drug-intolerant. Thus, low-dose, thrice weekly co-trimoxazole completely prevents AIDS-associated PCP, is cost-effective, and well tolerated by more than 85% of patients. Controlled comparisons of this regimen with other prophylactic agents are warranted.

How can epidemiology assist in guiding interventions for the acquired immunodeficiency syndrome/human immunodeficiency virus?

In a single decade, the pandemic of human immunodeficiency virus (HIV) infection has become an international health, social, and economic emergency. Early and effective intervention is urgently needed for both prevention of HIV infection and for the amelioration of clinical disease. Results of therapeutic trials have suggested expanding the population for which chemotherapy is indicated. In this paper, we first review the findings from selected recent drug trials, using zidovudine and pentamidine as examples. We then discuss six issues that we believe to be crucial for future epidemiologic research in the service of vaccine and drug development: 1. To identify which complications of HIV infection most urgently require development of new therapies, we must characterize the frequency and severity of specific medical events (outcomes) in persons taking a variety of treatments. 2. Currently, acquired immunodeficiency syndrome (AIDS) therapeutic trials gauge the effectiveness of new therapies by their impact on such clinical parameters as the time to development of AIDS or death. These approaches take too long to provide information. We urgently need to identify surrogate markers of clinical outcome that will be useful in the early assessment of treatment efficacy. 3. Progress in vaccine development is being retarded because we do not have enough data from natural history studies on host immunologic responses to suggest that a given response is protective. We therefore need to identify natural correlates of immunity, which can help set priorities in vaccine development. 4. Discovery that a therapy works in the setting of a clinical trial is only a first step in intervention. We must also assess the impact of new therapies on the health of the public, evaluating access to health care, compliance, and other barriers to treatment. 5. Clinical trials are usually associated with the effort to prevent disease in infected persons. However, other trials are needed to assess efforts to interrupt viral transmission through use of condoms, use of virucides, and treatment of sexually transmitted diseases, and by effecting specific behavioral changes. 6. Traditional methods of conducting clinical therapeutic research may not be adequate to address urgent questions in the AIDS/HIV epidemic. We must develop innovative clinical research methods, including better use of data from observational studies, to infer what we can about the effect of treatment on the clinical course.

A pilot study of low-dose zidovudine in human immunodeficiency virus infection

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.