Aerosolized amphotericin B-liposomes for treatment of systemic Candida infections in mice

Fungal diseases: could nanostructured drug delivery systems be a novel paradigm for therapy?

Invasive mycoses are a major problem for immunocompromised individuals and patients in intensive care units. Morbidity and mortality rates of these infections are high because of late diagnosis and delayed treatment. Moreover, the number of available antifungal agents is low, and there are problems with toxicity and resistance. Alternatives for treating invasive fungal infections are necessary. Nanostructured systems could be excellent carriers for antifungal drugs, reducing toxicity and targeting their action. The use of nanostructured systems for antifungal therapy began in the 1990s, with the appearance of lipid formulations of amphotericin B. This review encompasses different antifungal drug delivery systems, such as liposomes, carriers based on solid lipids and nanostructure lipids, polymeric nanoparticles, dendrimers, and others. All these delivery systems have advantages and disadvantages. Main advantages are the improvement in the antifungal properties, such as bioavailability, reduction in toxicity, and target tissue, which facilitates innovative therapeutic techniques. Conversely, a major disadvantage is the high cost of production. In the near future, the use of nanosystems for drug delivery strategies can be used for delivering peptides, including mucoadhesive systems for the treatment of oral and vaginal candidiasis.

Lipid-based carriers for pulmonary products: preclinical development and case studies in humans

A number of lipid-based technologies have been applied to pharmaceuticals to modify their drug release characteristics, and additionally, to improve the drug loading for poorly soluble drugs. These technologies, including solid-state lipid microparticles, many of which are porous in nature, liposomes, solid lipid nanoparticles and nanostructured lipid carriers, are increasingly being developed for inhalation applications. This article provides a review of the rationale for the use of these technologies in the pulmonary delivery of drugs, and summarizes the manufacturing processes and their limitations, the in vitro and in vivo performance of these systems, the safety of these lipid-based systems in the lung, and their promise for commercialization.

Disease guided optimization of the respiratory delivery of microparticulate formulations

BACKGROUND

Inhalation of microparticulate dosage forms can be effectively used in the treatment of respiratory and systemic diseases.

OBJECTIVE

Disease states investigated for treatment by inhalation of microparticles were reviewed along with the drugs' pharmacological, pharmacokinetic and physical chemical properties to identify the advantages of microparticulate inhalation formulations and to identify areas for further improvement.

METHODS

Microbial infections of the lung, asthma, diabetes, lung transplantation and lung cancer were examined, with a focus on those systems intended to provide a sustained release.

CONCLUSION

In developing microparticulate formulations for inhalation in the lung, there is a need to understand the pharmacology of the drug as the key to revealing the optimal concentration time profile, the disease state, and the pharmacokinetic properties of the pure drug as determined by IV administration and inhalation. Finally, in vitro release studies will allow better identification of the best dosing strategy to be used in efficacy and safety studies.

Safety of aerosolized amphotericin B

Aerosolized delivery of a number of antimicrobial agents has been studied. Despite a theoretical soundness behind this strategy, full consideration of the potential toxicities associated with this mode of administration is imperative. Aerosolized amphotericin B, as both deoxycholate and lipid formulations, has been studied in a variety of high-risk patient populations for prophylaxis and treatment against fungal infections. Although available data remain inconclusive regarding the clinical efficacy of this therapy, variability among results may be due to lack of standardization of administration methods and doses. Akin to the lack of clinical consensus, data regarding the tolerability of this means of amphotericin B delivery are conflicting. This variability may again be accounted for by the lack of standardized means for aerosolized administration. Owing to uncertain clinical benefit and concern for pulmonary toxicities, the use of aerosolized amphotericin B should be limited to clinical investigations at this time.

Liposome-based drug delivery to alveolar macrophages

The recent development of liposomal formulations compatible with aerosol delivery has expanded the potential to utilise chemotherapeutic agents directly targeted to the lungs more effectively. These are agents that would otherwise not be used because of their low solubility or toxicity. Various properties of liposomal carriers, including size, surface charge, composition and the presence of ligands, alter their efficacy and specificity towards alveolar macrophages to a great extent. This editorial summarises the advances in liposome-based drug delivery to alveolar macrophages.

Alternative administration of camptothecin analogues

In order to improve the therapeutic index of camptothecin (CPT) analogues, alternative administration of CPT analogues is being evaluated. Topotecan, irinotecan, rubitecan, lurtotecan and 9-aminocamptothecin have been administered orally with response rates equivalent to that seen after intravenous administration, where applicable. Oral availability and administration of some of the newer CPT analogues, including diflomotecan (BN80915) and grimatecan (ST1481), have also shown promising results. Aerosolisation of liposomal 9-nitrocamptothecin has been studied in patients with advanced malignancies involving the lung, demonstrating systemic antitumour activity. Intrathecal administration of topotecan has been studied in children with refractory neoplastic meningitis. It is well tolerated and associated with some antitumour activity. Intraperitoneal administration of topotecan as consolidation therapy in patients with ovarian cancer has shown promising results. Transdermal administration of rubitecan has been studied in mice. So far, no CPT has been approved for an alternative route of administration.

9-Nitrocamptothecin liposome aerosol treatment of human cancer subcutaneous xenografts and pulmonary cancer metastases in mice

The purpose of this study was to test the anticancer properties of the water-insoluble derivative of camptothecin, 9-nitrocamptothecin (9NC), administered in a liposome formulation (L-9NC) in aerosol to mice with subcutaneous xenografts of three human cancers and in mice with murine melanoma and human osteosarcoma pulmonary metastases. The drug was formulated with dilauroylphosphatidylcholine and nebulized in particle sizes of 1.2-1.6 microns mass median aerodynamic diameter and a geometric standard deviation of 2.0. The aerosol was generated with the nebulizer flowing at 10 l/min and delivered to mice in sealed plastic cages or in a nose-only exposure chamber. Aerosol was administered for 15 min to 2 hr daily, delivering deposited doses in the respiratory tract of 8.1-306.7 micrograms of 9NC/kg. With subcutaneous tumors, growth was greatly inhibited or tumors were undetectable after several weeks of treatment. We also showed that oral dosage with L-9NC had no detectable effect on cancer growth, and thus the benefit from aerosol treatment was due to pulmonary deposition and not the larger fraction of drug deposited in the nose of mice during aerosol treatment which is promptly swallowed. Intramuscular L-9NC in slightly larger doses than given in the aerosol had detectable anticancer activity, but it was significantly less than in mice receiving the drug by aerosol. With metastatic pulmonary cancers, treated animals showed highly significantly less cancer growth than control animals. L-9NC aerosol showed a major therapeutic benefit in the treatment of subcutaneous human cancer xenografts in nude mice, suggesting that cancers at systemic sites might be responsive to this treatment. In addition, the strong anticancer effect of L-9NC aerosol on pulmonary metastases offers a therapeutic approach for treatment of pulmonary cancers. Thus, L-9NC aerosol may have applicability in the treatment of cancers throughout the body.

Trends in antifungal research

With the increasing use of aggressive immunosuppressive therapies in the management of a variety of patient populations, the continuing presence of the AIDS pandemic and the therapeutic advances employed in critical care settings, an increasing number of serious fungal infections are being encountered by today's practicing clinicians. Traditionally, antifungal drug therapy has been delivered by means of intravenous infusion, oral administration, or topical application. Recently, a number of alternative routes of antifungal drug delivery have been developed and investigated, and the traditional means of antifungal administration have been improved to facilitate the therapeutic use of new and reformulated antifungal agents. Organized based on the route of administration, this chapter reviews these advances in antifungal drug delivery.

Alternative administration of camptothecin analogues

The binding of camptothecin (CPT) to the DNA-topoisomerase complex is reversible, but it needs to be maintained for maximal inhibitory activity. It is also dependent on the chemical structure of CPT. The lactone form is thought to be necessary for the activity. In human serum, the equilibrium between lactone and carboxylate is in favor of the latter. For these reasons, alternative administration of CPT analogues is being evaluated. The ideal compound would remain in lactone form and would expose the host for long periods of time to its effects. Oral administration of irinotecan (CPT-11) and topotecan (TPT) is discussed by other investigators. We studied oral rubitecan and reported a low lactone to total drug area under the plasma concentration-time curve (AUCP) ratio (14.7%), with low plasma concentration over time despite repeated administrations and the presence of an enterohepatic cycle. Aerosolization of a liposomal formulation of rubitecan is currently under study. Six patients have been treated once a day for 5 days every 3 weeks. The dose was 6.7 micrograms/kg/day. Plasma levels are dose for dose higher than those after oral administration, but the ratio of lactone versus total drug is low. No toxicity was observed. The study will continue with increasing doses and lengths of administration. Intrathecal administration of topotecan has been studied in a phase I trial in children. Doses of 0.4 mg are tolerated without toxicity, and clinical responses have been seen in patients with refractory meningial carcinomatosis. Phase II studies are planned. Intraperitoneal (i.p.) administration of topotecan has been studied in a phase I trial as a 24-hour infusion in 5% dextrose at pH 3.5 every 21 days. Dose-limiting toxicity is 4 mg/m2. Toxic effects are neutropenia, anemia, emesis, fever, and pain. Five of 10 patients with ascites had symptomatic relief. Pharmacokinetic analysis demonstrates a second-order kinetics with elimination half-lives of 0.49 and 2.7 hours. The peritoneal to plasma AUC ratio was 31.2. Intramuscular, transdermal, and subcutaneous administrations have been extensively studied in the mouse.

Successful treatment of rhinocerebral mucormycosis by a combination of aggressive surgical debridement and the use of systemic liposomal amphotericin B and local therapy with nebulized amphotericin--a case report

A case of mucormycosis involving the nose and paranasal sinuses in a 55-year-old man with recently diagnosed acute promyelocytic leukaemia is reported. It was successfully treated with a combination of aggressive surgical debridement and systemic amphotericin B. In addition, local nebulized amphotericin B was used as an adjunct to therapy. We believe this is only the second documented use of nebulized amphotericin in the management of sinonasal mucormycosis. The need for a high index of suspicion and early aggressive management is emphasized.

Pulmonary delivery of beclomethasone liposome aerosol in volunteers. Tolerance and safety

STUDY OBJECTIVE

To test the tolerance and safety of single doses of beclomethasone dipropionate (Bec)-dilauroylphosphatidylcholine (DLPC) liposome aerosol in volunteers.

DESIGN

Single-dose inhalations of liposome preparations of Bec-DLPC and DLPC alone were administered for 15 min from a jet nebulizer (Puritan-Bennett, modified twin jet; mass median aerodynamic diameter of 1.6 microns) under close clinical and laboratory surveillance. Two dose levels (0.5 mg Bec/12.5 mg DLPC per milliliter, and 1.0 mg Bec and 25 mg DLPC per milliliter in the reservoirs, respectively) were administered. The Bec doses were selected to approximate the dosages of this glucocorticoid used with metered-dose inhalers (MDIs). First, four volunteers were exposed to an initial low dose; the mean (+/-SD) inhaled doses were 0.56 +/- 0.07 mg of Bec and/or 14.0 +/- 1.8 mg of DLPC. Subsequently, a second group of six volunteers was exposed to a higher dose; the mean (+/-SD) inhaled doses were 1.29 +/- 0.14 mg of Bec and/or 34.6 +/- 6.8 mg of DLPC.

SETTING

Outpatient and inpatient.

PATIENTS

Normal male (n = 6) and female (n = 4) adult volunteers.

INTERVENTIONS

Inhalation of Bec-DLPC and DLPC liposome aerosols in a single-dose tolerance study involving 10 normal volunteers.

MEASUREMENTS AND RESULTS

Spirometry, clinical observations, clinical chemistry, and hematology were monitored. No adverse clinical or laboratory events were observed.

CONCLUSIONS

Bec-DLPC liposome aqueous aerosol was well tolerated in doses equivalent to those currently administered by MDIs and dry powder inhalers for treatment of asthma.

Liposomal aerosols in the management of pulmonary infections

The combination of liposomes and aerosols has been utilized to directly target the lungs with chemotherapeutic agents that might not have been used because of low solubility or toxicity. There are a variety of antibacterials, antifungals, and antivirals that have good in vitro activity, but are not effective because of their systemic toxicity and/or poor penetration into the lungs. Incorporation of many lipophilic drugs into liposomes decreases their toxicity without affecting effectiveness, thus increasing the therapeutic index. We have focused on aerosol delivery of amphotericin B (ampB) for the treatment of pulmonary and systemic fungal diseases. We have tested a variety of ampB-lipid formulations for the optimal treatment regimen for Cryptococcus and Candida infections in mouse models. The AeroTech II nebulizer (MMADs of 1.8-2.2 microns) produced aerosols with the highest concentrations in the breathable range. Pharmacokinetic studies revealed that pulmonary drug was present for hours to weeks. AmBisome retained its anticryptococcal activity even when animals were challenged 14 days after aerosol treatment. Aerosols may also be effective in systemic diseases. In our Candida-mouse model, systemic candidiasis and mortality were reduced by aerosolized ampB-liposome treatment. The ability to utilize lipophilic drugs, to deliver high concentrations of drug directly to the site of infection, and to reduce toxicity makes aerosol liposomes an attractive, alternative route of administration.

Carrier effects on biological activity of amphotericin B

Amphotericin B (AmB), the drug of choice for the treatment of most systemic fungal infections, is marketed under the trademark Fungizone, as an AmB-deoxycholate complex suitable for intravenous administration. The association between AmB and deoxycholate is relatively weak; therefore, dissociation occurs in the blood. The drug itself interacts with both mammalian and fungal cell membranes to damage cells, but the greater susceptibility of fungal cells to its effects forms the basis for its clinical usefulness. The ability of the drug to form stable complexes with lipids has allowed the development of new formulations of AmB based on this property. Several lipid-based formulations of the drug which are more selective in damaging fungal or parasitic cells than mammalian cells and some of which also have a better therapeutic index than Fungizone have been developed. In vitro investigations have led to the conclusion that the increase in selectivity observed is due to the selective transfer of AmB from lipid complexes to fungal cells or to the higher thermodynamic stability of lipid formulations. Association with lipids modulates AmB binding to lipoproteins in vivo, thus influencing tissue distribution and toxicity. For example, lipid complexes of AmB can be internalized by macrophages, and the macrophages then serve as a reservoir for the drug. Furthermore, stable AmB-lipid complexes are much less toxic to the host than Fungizone and can therefore be administered in higher doses. Experimentally, the efficacy of AmB-lipid formulations compared with Fungizone depends on the animal model used. Improved therapeutic indices for AmB-lipid formations have been demonstrated in clinical trials, but the definitive trials leading to the selection of an optimal formulation and therapeutic regimen have not been done.

Fungal infections in lung and heart-lung transplant recipients. Report of 9 cases and review of the literature

We reviewed the pattern and incidence of fungal infections in patients undergoing lung and heart-lung transplantation at Duke University Medical Center from September 1992 until August 1995, and present here 9 illustrative cases. Of the 73 lung and heart-lung transplant recipients studied, 59 (81%) had positive fungal cultures at some point after transplantation. The cases presented here illustrate that lung transplant recipients are predisposed to a wide variety of fungal infections. The clinical pattern of these infections ranges from asymptomatic to rapidly progressive fatal disease. In addition to the reactivation of previous fungal infections and recent exposure to new environmental sources, the donor lung itself can be the source of fungal infection, as we showed by using molecular epidemiology techniques. Because of the associated morbidity and mortality, efforts should be directed at investigating prophylactic antifungal regimens in lung transplant recipients. Preliminary reports on the use of itraconazole and aerosolized amphotericin B have been encouraging. Prospective randomized studies are needed to assess the safety and cost effectiveness of different regimens. Fungal infections in patients after lung transplantation can significantly impede recovery and lead to substantial mortality.

Recent advances in liposomal drug-delivery systems

Liposomal drug-delivery systems have come of age in recent years, with several liposomal drugs currently in advanced clinical trials or already on the market. It is clear from numerous pre-clinical and clinical studies that drugs, such as antitumor drugs, packaged in liposomes exhibit reduced toxicities, while retaining, or gaining enhanced, efficacy. This results, in part, from altered pharmacokinetics, which lead to drug accumulation at disease sites, such as tumors, and reduced distribution to sensitive tissues. Fusogenic liposomal systems that are under development have the potential to deliver drugs intracellularly, and this is expected to markedly enhance therapeutic activity. Advances in liposome design are leading to new applications for the delivery of new biotechnology products, such as recombinant proteins, antisense oligonucleotides and cloned genes.