Pharmacokinetics and pharmacodynamics of granulocyte-macrophage colony-stimulating factor and zidovudine in patients with AIDS and severe AIDS-related complex

Antiretroviral drug interactions

It has recently been estimated that persons with the acquired immunodeficiency syndrome (AIDS) receive on average 5.6 prescription medications throughout their disease course, and this number may be as high as 9 [1,2]. With the development and testing of new antiretroviral agents and drugs for opportunistic infections associated with human immunodeficiency virus (HIV) disease, the issue of polypharmacy and multiple drug interactions will become increasingly complex. Since antiretroviral therapy and treatment or prophylaxis of opportunistic infections is lifelong, the nature of these interactions requires delineation to provide an optimal pharmacologic strategy for the use of these agents in combination. This article will address antiretroviral drug interactions from a pharmacokinetic and pharmacodynamic perspective. A background on the clinical pharmacology of antiretroviral agents is provided as is a discussion of selected interactions.

Effect of granulocyte/macrophage colony-stimulating factor on vaccination with an allogeneic whole-cell melanoma vaccine

PURPOSE

The availability of a variety of immune response modifiers creates an opportunity for improved efficacy of immunotherapy, but it also leads to uncertainty in how to combine agents and how to assess those combinations. We sought to assess the effect of the addition of granulocyte/macrophage colony-stimulating factor (GM-CSF) to vaccination with a melanoma vaccine.

EXPERIMENTAL DESIGN

Ninety-seven patients with resected melanoma (stage II-IV) were enrolled, stratified by stage, and randomized to receive a cellular melanoma vaccine with or without GM-CSF. The primary endpoint was delayed-type hypersensitivity (DTH) response to melanoma cells. Antibody responses, peripheral leukocyte counts, and survival were also examined.

RESULTS

The GM-CSF arm showed enhanced antibody responses with an increase in IgM titer against the TA90 antigen and increased TA90 immune complexes. This arm also had diminished antimelanoma cell delayed-type hypersensitivity response. Peripheral blood leukocyte profiles showed increases in eosinophils and basophils with decreased monocytes in the GM-CSF arm. These immune changes were accompanied by an increase in early melanoma deaths and a trend toward worse survival with GM-CSF.

CONCLUSION

These data suggest that GM-CSF is not helpful as an immune adjuvant in this dose and schedule and raise concern that it may be harmful. Based on the discordant findings of an immune endpoint and clinical outcome, the use of such surrogate endpoints in selecting treatments for further evaluation must be done with a great deal of caution.

HIV and other lentiviral infections cause defects in neutrophil chemotaxis, recruitment, and cell structure: immunorestorative effects of granulocyte-macrophage colony-stimulating factor

Patients with HIV infection exhibit deficits in bacterial and fungal clearance, and possibly depressed innate immunity. In this study, we observed that neutrophils from HIV-infected patients have a profound defect in chemotaxis in response to endogenous (IL-8) and bacterial (fMLP) chemoattractants, which was directly correlated with peripheral CD4(+) lymphocyte levels but not plasma viral load. A similar chemotactic defect was observed in the feline immunodeficiency virus (FIV) model of HIV infection. Intravital microscopy of FIV-infected animals revealed marked impairment in the in vivo recruitment of leukocytes; specifically integrin-dependent neutrophil adhesion and emigration induced by bacterial products. Treatment of FIV-infected animals with GM-CSF re-established both neutrophil recruitment (rolling, adhesion, and emigration) and in vitro chemotaxis to the levels seen in uninfected animals. This restoration of neutrophil responses was not due to GM-CSF-mediated priming. Rather, HIV and FIV infections resulted in defective neutrophil development, with an ensuing reduction in neutrophil granularity and chemotactic receptor expression. GM-CSF therapy restored neutrophil granularity, implying restoration of normal neutrophil development. Together, our findings underscore the fundamental defects in innate immunity caused by lentivirus infections, while also indicating that GM-CSF may be a potential immunorestorative therapy for HIV-infected patients.

High-dose granulocyte-macrophage colony-stimulating factor-producing vaccines impair the immune response through the recruitment of myeloid suppressor cells

Tumor vaccines have shown promise in early clinical trials. Among them, tumor cells genetically engineered to secrete biologically active granulocyte-macrophage colony-stimulating factor (GM-CSF) can generate a systemic antitumor immune response. Although the minimal required GM-CSF dose produced by modified tumor cells to achieve a measurable antitumor effect is well known, no data examined whether an upper therapeutic limit may exist for this vaccination strategy. Because recent data demonstrate an immunosuppressive effect of GM-CSF produced by growing tumors, we thus sought to determine whether high GM-CSF doses administered in a vaccine formulation could impair antitumor immunity. Using a vaccine strategy involving a GM-CSF-producing bystander cell line (B78H1-GM) admixed with autologous tumor, we assessed the impact of varying doses of GM-CSF while maintaining a constant antigen dose. Our results defined a threshold above which a GM-CSF-based vaccine not only lost its efficacy, but more importantly for its clinical implications resulted in substantial immunosuppression in vivo. Above this threshold, GM-CSF induced Gr1+/CD11b+ myeloid suppressor cells that substantially impaired antigen-specific T-cell responses and adversely affected antitumor immune responses in vivo. The dual effects of GM-CSF are mediated by the systemic and not local concentration of this cytokine. Myeloid suppressor cell-induced immunosuppression is mediated by nitric oxide production via inducible nitric oxide synthase (iNOS) because the specific iNOS inhibitor, l-NMMA, restored antigen-specific T-cell responsiveness in vitro. Taken together, our data demonstrated the negative impact of supra-therapeutic vaccine doses of GM-CSF and underscored the importance of identifying these critical variables in an effort to increase the therapeutic efficacy of tumor vaccines.

Enhancement of protective humoral (Th2) and cell-mediated (Th1) immune responses against herpes simplex virus-2 through co-delivery of granulocyte-macrophage colony-stimulating factor expression cassettes

Granulocyte-macrophage colony-stimulating factor (GM-CSF) could in theory attract antigen-presenting cells in muscle following intramuscular DNA immunization, resulting in enhanced antigen-specific immune responses. Thus, such adjuvants could constitute an important addition to a herpes vaccine by amplifying specific immune responses. Here we investigate the utility of GM-CSF cDNA as a vaccine adjuvant for herpes simplex virus (HSV)-2 in a mouse challenge model. GM-CSF cDNA co-injection enhanced levels of specific IgG, IgE and IgA against HSV-2 gD protein significantly higher than gD plasmid vaccination alone. Moreover, GM-CSF co-injection induced a dramatic increase in IgG1 levels, as compared to IgG2a levels, suggesting a Th2 bias in the response. T helper cell proliferation and secretion of cytokines (IL-2 and IFN-gamma) were significantly increased by GM-CSF cDNA co-injection. When challenged with a lethal dose of HSV-2, GM-CSF co-injection increased survival rates to 90%, an improvement as compared to gD vaccination alone (60-63%). Furthermore, GM-CSF cDNA co-injection reduced herpetic lesions and resulted in a faster recovery from lesions. These data indicate that GM-CSF cDNA enhances both humoral and cellular immune responses and enhances vaccine efficacy, resulting in reduced HSV-2-derived morbidity as well as mortality.

Hematologic complications of human immunodeficiency virus infection and the acquired immunodeficiency syndrome

The hematologic manifestations of HIV infection and AIDS are common and may cause symptoms that are life-threatening and impair the quality of life of these patients. The most important of these manifestations are cytopenias. Anemia and neutropenia are generally caused by inadequate production because of suppression of the bone marrow by the HIV infection through abnormal cytokine expression and alteration of the bone marrow microenvironment. Thrombocytopenia is caused by immune-mediated destruction of the platelets, in addition to inadequate platelet production. The incidence and severity of cytopenia are generally correlated to the stage of the HIV infection. Other causes of cytopenia in these patients include adverse effects of drug therapy, the secondary effects of opportunistic infections or malignancies, or other preexisting or coexisting medical problems that may be prevalent in the HIV-infected population. Diagnosis of the mechanism and cause of the cytopenia may allow for specific management. Optimal management of the underlying HIV infection is essential, and mild cytopenia in asymptomatic patients may need no specific management. Supportive care for anemia includes the use of erythropoietin in addition to the judicious use of red blood cell transfusions. Therapy for neutropenia includes the use of the myeloid growth factors G-CSF and GM-CSF. Immune-mediated thrombocytopenia may be treated with a combination of zidovudine, corticosteroids, IVGG, and splenectomy. Platelet transfusions are sometimes needed for the treatment of thrombocytopenia caused by decreased production. Other hematologic manifestations such as hypergammaglobulinemia and lupus anticoagulants are commonly asymptomatic and usually require no specific therapy, but they can rarely cause morbidity and require specific interventions.

Pharmacokinetics of recombinant human granulocyte-macrophage colony-stimulating factor: the effects of zidovudine

Recombinant human granulocyte-macrophage colony-stimulating factor (rHu GM-CSF) enhances bone marrow production of and stimulates granulocytes, macrophages, and eosinophils. Granulocyte-macrophage colony-stimulating factor may be used concomitantly with zidovudine in human immunodeficiency virus (HIV)-positive patients to minimize zidovudine-associated neutropenia. This open-label, randomized, placebo-controlled study was performed to evaluate the pharmacokinetic disposition of rHu GM-CSF in HIV-positive, asymptomatic patients in the absence and presence of concomitant zidovudine administration. Eight participants received rHu GM-CSF (5 micrograms/kg subcutaneously) daily for 4 days in combination with placebo or zidovudine (200 mg orally every 8 hours) in a randomized, crossover fashion, with each study period separated by a 3-day washout phase. Pharmacokinetic blood sampling was performed over 16 hours on days 1 and 4 of both treatment periods, and subsequent analysis of serum was performed using an enzyme-linked immunosorbent assay. Pharmacokinetic results of rHu GM-CSF at steady state (days 4 of periods I and II) in the absence (placebo) and presence of zidovudine included apparent total body clearance, half-life, and apparent volume of distribution, all of which were not significantly altered with concomitant administration of zidovudine. Mean pharmacokinetic results of rHu GM-CSF after the first dose (days 1 of periods I and II) were similar to steady-state values; however, total body clearance was significantly increased at steady state compared with the results of the first dose. Concurrent administration of zidovudine does not influence the pharmacokinetic disposition of rHu GM-CSF after single or multiple doses.

Lack of in vivo effect of granulocyte-macrophage colony-stimulating factor on human immunodeficiency virus type 1

Neutropenia complicates HIV disease or its treatment in a large proportion of patients. Hematopoietic growth factor support has been tested in a number of clinical settings in HIV disease and has been demonstrated to be of benefit for specific parameters. One consideration regarding the use of hematopoietic growth factors in HIV disease is their potential effect on HIV viral burden, since alterations in HIV expression have been documented with certain cytokines in vitro. It has also been reported that some cytokines, notably GM-CSF, potentiate the antiviral properties of thymidine analogs such as zidovudine (AZT) in vitro. We tested these observations in vivo. Twelve HIV-positive patients with a CD4 cell count < or = 200/mm3 or HIV plasma viremia who were receiving a stable dose of zidovudine were enrolled into three dose cohorts of yeast-derived GM-CSF at 50, 125, or 250 micrograms/m2 daily by subcutaneous self-injection for 28 days. Measurements of HIV activity included serum acid-dissociated HIV p24 antigen levels, plasma and peripheral blood mononuclear cell (PBMC) limiting dilution HIV culture, and plasma HIV quantitative competitive polymerase chain reaction (PCR). Serum and intracellular zidovudine levels were measured as well as hematologic, immunologic, and toxicity parameters. Virologic measures showed neither significant upregulation nor downregulation of serum acid-dissociated HIV p24 antigen, plasma and PBMC HIV culture, or PCR in association with GM-CSF administration. A trend toward increased intracellular AZT levels was noted, but this did not achieve statistical significance (p = 0.073). CD4 and CD8 lymphocytes were essentially unaffected while absolute neutrophil counts increased with GM-CSF administration as expected. These data suggest that administration of GM-CSF does not perturb HIV activity or immunologic parameters in patients receiving AZT for advanced HIV disease. No potentiation of AZT antiviral effect was demonstrated.

Chemotherapy combined with zidovudine and GM-CSF in human immunodeficiency virus-related non-Hodgkin's lymphoma

OBJECTIVE

The treatment of patients with non-Hodgkin's lymphoma related to the human immunodeficiency virus (HIV-NHL) is complicated by the underlying acquired immunodeficiency syndrome (AIDS). Patients without adverse prognostic factors (no AIDS prior to lymphoma, CD4+ lymphocyte counts greater than 100 x 10(6)/l and good performance status) can be cured of lymphoma and experience long-term survival. Our previous study with the intensive chemotherapy LNH84 regimen yielded a 63% complete response (CR) rate but median survival was only nine months, half of the patients died of AIDS and the other half of their lymphoma. We report here the results of a phase II study combining the same chemotherapy with zidovudine and GM-CSF. Our goal was to improve the treatment outcome over that of our previous study; GM-CSF was expected to decrease the hematological toxicity of chemotherapy and thus permit a dose intensity increase, while zidovudine was supposed to slow down the evolution of AIDS.

DESIGN AND SETTING

A phase II non-randomized prospective clinical trial in 7 centres.

PATIENTS AND METHODS

Thirty-two consecutive adult patients presenting HIV-NHL and performance status of less than three without active opportunistic infection underwent three cycles of doxorubicin 75 mg/m2, cyclophosphamide 1,200 mg/m2, vindesine 2 mg/m2 for two days, bleomycin 10 mg for two days and prednisolone 60 mg/m2 for five days (ACVB). Chemotherapy was associated with zidovudine (5 mg/kg/d) and GM-CSF (5 mu g/kg/d). The induction phase was followed by a four-month consolidation phase.

RESULTS

CR and PR > 75% were observed in 56% of patients; 25% of the patients died during the induction phase. These results were analogous to those of the previous study (63% and 14%, respectively). Neither hematological tolerance nor dose intensity were improved. With a mean follow-up of 23.5 months, median survival was 6.7 months. The rate of non-NHL AIDS-related death during CR was not reduced (22% in our study vs. 16% in our previous one).

CONCLUSIONS

GM-CSF failed to reduce significantly the cumulative hematological toxicity of chemotherapy and zidovudine. New antiviral agents without hematological toxicity would perhaps be useful in this setting.

Oral and intravenous zidovudine pharmacokinetics: the effect of granulocyte-macrophage colony stimulating factor

Combination therapy with zidovudine and recombinant human granulocyte-macrophage colony stimulating factor (rHu GM-CSF) may be warranted, owing to the bone marrow suppressive effects of zidovudine. A study of 16 patients, 8 of whom had acquired immune deficiency syndrome (AIDS) and 8 of whom were infected with human immunodeficiency virus (HIV) but were asymptomatic, was conducted. The effect of 4 days of rHU GM-CSF versus placebo on intermittent zidovudine therapy (200 mg every 8 hours) was evaluated using a randomized, cross-over study design. Pharmacokinetics of oral and intravenous zidovudine were determined on days 1 (oral), 3 (oral), and 4 (intravenous) of rHu-GM-CSF (placebo) administration. After intravenous dosing, zidovudine plasma clearance for placebo and rHu GM-CSF averaged 1.4 +/- 0.2 and 1.3 +/- 0.2 L/hr/kg, respectively (P = 0.017), mean residence time averaged 1.5 +/- 0.5 and 1.9 +/- 0.6 hours, respectively (P = 0.012), and the steady-state volume of distribution was 2.0 +/- 0.7 and 2.3 +/- 0.7 L/kg, respectively (P = 0.027) for the two treatment arms. Stratified data for patients with AIDS and those with asymptomatic HIV infection revealed no significant difference in plasma clearance or mean residence time between the two patient groups. These pharmacokinetic results indicate that dosage adjustments for zidovudine are not warranted when administered with rHu GM-CSF owing to the small changes observed. However, the statistically significant increase in Vss suggests the possibility of enhanced zidovudine cellular uptake in the presence of rHu GM-CSF.