Activity of Posaconazole Combined with Amphotericin B against Aspergillus flavus Infection in Mice: Comparative Studies in Two Laboratories

Abstract

Posaconazole and/or amphotericin B was given to mice pretreated with a steroid and then infected by inhalation of Aspergillus flavus conidia. Two laboratories conducted studies using almost identical protocols to evaluate both survival and lung tissue burdens 8 days after infection. The results of the in vivo studies performed at both laboratories were consistent. We found that (i) up to 5 mg of amphotericin B per kg of body weight was poorly effective in treating invasive aspergillosis; (ii) posaconazole at 2 or 10 mg/kg/dose prolonged survival and reduced lung tissue CFU; and (iii) there was generally no antagonistic interaction of the drugs in combination, even when the experiments were designed to maximize the likelihood of antagonism. These studies do not confirm the antagonistic interaction of triazoles and polyenes reported by others.Acute invasive aspergillosis (AIA) is one of the most feared infections of immunosuppressed patients. Both corticosteroids and neutropenia predispose to this infection, which almost invariably occurs after inhalation of infectious conidia (1). The speed of dissemination or pulmonary spread of the infection, and ultimately survival, depend in large part on the nature and severity of the predisposing host immune defect(s). In patients with the most fulminating forms of AIA, it has been difficult to demonstrate efficacy of antifungal therapy (7, 11). To date, there have been three approaches in the management of aspergillosis. The first is reversal of the predisposing conditions if possible. The second is antifungal therapy, and the third is resection when possible (18). Animal studies have been increasingly used to help determine whether a particular antifungal drug is effective against invasive aspergillosis. Some advantages of animal studies include (i) information in ascertaining the relative efficacy and dose-dependent toxicity of antifungal agents; (ii) assessing the contributions of immune deficiency to the outcome of aspergillosis; (iii) evaluating combinations of antifungals; and (iv) controlling for a variety of conditions that are thought to contribute to human invasive aspergillosis and its outcome but that cannot be controlled in clinical studies.The experiment quoted most often, an experiment using amphotericin B and ketoconazole, was conducted by Schaffner and Frick (15) some years ago. When mice with AIA were treated with ketoconazole before amphotericin B, Schaffner and Frick noted a marked decrease in the efficacy of amphotericin B (15). They theorized that the azole blocked the synthesis of the ergosterol target necessary for the binding of amphotericin B. Polak et al. also found somewhat similar results (13,14). These studies led to the concern that azole antifungal agents would antagonize the effects of amphotericin B in humans and that therefore they should not be used in combination with amphotericin B clinically.In a large review of 595 cases of aspergillosis, Patterson et al. found that patients treated with amphotericin B and then with itraconazole fare...

Combination Treatment of Invasive Fungal Infections

“…ITRA preexposure was associated with poorer mycological efficacy and survival in mice treated subsequently with AmB for invasive pulmonary aspergillosis (130). However, in a recent study, Najvar et al (154) investigated the interlaboratory variations in determining the in vivo efficacy of the AmB-plus-POSA combination in a murine model of A. flavus infection and reported consistent results from both sites. These investigators found that no antagonism existed between AmB and POSA in vivo, even when the experiments were designed to maximize the likelihood of antagonism.…”

“…The following criteria are commonly followed: synergy, a Ն2-log 10 decrease in CFU/ ml compared to the most active constituent; antagonism, a Ն2-log 10 increase in CFU/ml compared to the least active agent; additivity, a Ͻ2-but Ͼ1-log 10 decrease in CFU/ml compared to the most active agent; and indifference, a Ͻ2-but Ͼ1-log 10 increase in CFU/ml compared to the least active agent. (97,98,130,154,156,211), rats (140), or rabbits (172). Factors that need to be considered while performing in vivo studies include variable drug absorption, distribution, and metabolism among animal species.…”

Novel antifungal agents as salvage therapy for invasive aspergillosis in patients with hematologic malignancies: posaconazole compared with high-dose lipid formulations of amphotericin B alone or in combination with caspofungin

“…10 However, studies have shown that orally administered posaconazole can achieve plasma concentrations that exceed the minimum inhibitory concentration for Aspergillus. 29,30 In addition, Krishna et al 31 have shown that oral posaconazole in allogeneic stem cell transplant patients with graft-versus-host disease achieves efficacious plasma concentrations and is not affected by variables such as body weight or grade of graftversus-host disease. In the patient population evaluated in this study, almost half of whom underwent stem cell transplant, with the majority of those having graft-versus-host disease, posaconazole was not expected to demonstrate superiority in terms of response and survival to parenteral antifungal therapy.…”

In Vivo Synergy of Amphotericin B plus Posaconazole in Murine Aspergillosis

“…Since the efficacies of different antifungal combinations have been demonstrated by several studies in patients with aspergillosis (6,7,12), we were interested in evaluating the in vivo efficacy of the combination of amphotericin B (AMB) plus PSC against A. fumigatus. This combination had already been tested in a murine model of invasive aspergillosis caused by Aspergillus flavus (13), although no improvement over the PSC monotherapy was observed. Another study demonstrated the efficacy of suboptimal doses of VRC plus anidulafungin in a murine model of A. fumigatus infection (14), suggesting that combined therapies might have an important role as alternative treatments against systemic aspergillosis, allowing a reduction of the doses administered.…”