Immunosuppression with aerosolized cyclosporine for prevention of lung rejection in a rat model

Safety and toxicology of cyclosporine in propylene glycol after 9-month aerosol exposure to beagle dogs

BACKGROUND

Cyclosporine inhalation solution (CIS) delivered via nebulization is under evaluation for the prevention of chronic rejection post-lung transplant. A 300-patient randomized, controlled clinical trial (CYCLIST) is expected to be completed late in 2011. In support of this trial, a chronic inhalation toxicology study in dogs has been completed.

METHODS

To mimic the clinical setting, animals (four/sex/dose plus two/sex/dose in the control and high dose recovery groups) were exposed to aerosolized CIS, via nose-only exposure, three times per week for 9 months at targeted inhaled doses of 0 (air), 4, 12, and 24 mg/kg. In addition, the potential for persistence or reversibility of any toxic effects were assessed after a 6-week recovery period. The toxicological endpoints included clinical observations, body-weight, food consumption, toxicokinetics, clinical chemistry, and histopathology.

RESULTS

All dogs receiving CIS completed the study with the only consistent observations being excessive salivation and changes in minute ventilation. There was no limiting lung or systemic toxicity associated with exposure to CIS, and the only possible drug-related effect was an observation of benign fibroadenoma tissue in the mammary glands of the high-dose female recovery group. Toxicokinetic data showed that cyclosporine is initially absorbed rapidly with little drug remaining in lung tissue or blood 24 h after the end of dosing.

CONCLUSION

The study supports the pulmonary and systemic safety of aerosolized CIS at expected lung dose levels/kg of up to 12 times greater than the average dose patients are receiving in the CYCLIST trial.

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.

Inhaled delivery of aerosolized cyclosporine

Aerosolized cyclosporine was the first calcineurin inhibitor to be developed for inhaled administration. Its use as a topical immunosuppressant after lung transplantation is reviewed. Animal studies in transplant and non-transplant models are considered, as is nebulized delivery of the drug, including the results of scintigraphy and pharmacokinetic studies. Open label clinical studies of the drug for the treatment of chronic and acute lung transplant rejection are detailed. Placebo controlled trials for rejection prophylaxis are described and future directions for the drug are considered. Aerosol cyclosporine provides an excellent example of how inhaled aerosol delivery can provide therapeutic concentrations of drug in the lungs while minimizing the side effects associated with high systemic concentrations. In the case of lung transplantation, the drug is delivered directly to the airways, the location of the pathology resulting in most mortality in this population (chronic allograft rejection), maximizing the efficacy of this dose-dependent immunosuppressant.

Ciclosporin aerosol in lung transplantation

The development of ciclosporin as an aerosol for rejection immunosuppression following lung transplantation started as a research idea at the University of Pittsburgh in 1989. In the 17 subsequent years, the development of the aerosol, testing in animals and several protocols testing the drug in patients have all taken place at the University of Pittsburgh and State University of New York. No other medical advances have displaced the potential of the drug during this time in lung transplantation, which still has a dismal 5-year survival of 50%. Therefore, the recent publication of the double-blind, placebo-controlled study of aerosolised ciclosporin for long-term use to significantly improve patient survival was heralded as a breakthrough by the commentary in the New England Journal of Medicine. Nevertheless, multiple problems may prevent this drug from ever receiving FDA approval and reaching the market. These problems include the need for a multi-centre study, a lack of surrogate markers for chronic rejection in lung transplant patients and a drug formulation that will prevent the expansion of the use of aerosolised ciclosporin for other indications.

In the lung aerosol cyclosporine provides a regional concentration advantage over intramuscular cyclosporine

BACKGROUND

Acute rejection remains an almost universal complication among lung transplant recipients. Refractory rejection as well as chronic systemic immunosuppression is associated with significant morbidity and mortality. Recent studies suggest that aerosol cyclosporine may address these issues by effectively preventing acute cellular rejection while maintaining low systemic drug concentrations. This study was designed to evaluate the concentrations of cyclosporine in blood and lung tissue after aerosol and intramuscular administration.

METHODS

Lewis rats were divided into 4 experimental groups: Groups A (n = 33) and B (n = 30) received aerosol cyclosporine 3 and 5 mg/kg, respectively; Groups C (n = 33) and D (n = 30) received systemic cyclosporine 5 and 15 mg/kg, respectively. We used high-performance liquid chromatography to quantitate blood and lung tissue cyclosporine levels at timed intervals. We used the trapezoidal rule to approximate area under the concentration vs time curve (AUC).

RESULTS

Aerosol delivery of cyclosporine resulted in higher and more rapid peak drug levels in lung tissue samples than did systemic delivery. At an equivalent 5 mg/kg dose, the cyclosporine AUC was 3 times higher with aerosol delivery than with intramuscular delivery in lung tissue (477,965 vs 157,706 ng x hour/g, respectively). The lung tissue: blood AUC ratio was highest in the aerosol groups (27.3:1 and 17.4:1) compared with the intramuscular groups (8.1:1 and 9.4:1).

CONCLUSION

Local aerosol inhalation delivery of cyclosporine provides a regional advantage over systemic intramuscular therapy by providing higher peak concentrations and greater lung tissue exposure.

Aerosol cyclosporine prevents acute allograft rejection in experimental lung transplantation

BACKGROUND

The incidence of acute rejection and the morbidity of systemic cyclosporine (INN: cyclosporine) after lung transplantation is significant. Experimental evidence suggests that the allograft locally modulates the immune mechanisms of acute rejection. The purpose of this study was to determine whether aerosolized cyclosporine would prevent acute cellular rejection, achieve effective graft concentrations with low systemic drug delivery, and locally affect production of the inflammatory cytokines involved in acute rejection.

METHODS

Unilateral orthotopic left lung transplantation was performed in 64 rats (ACI to Lewis), which were divided into eight groups (each group, n = 8): group A, no treatment; groups B to D, aerosol cyclosporine 1 to 3 mg/kg per day, respectively; group E to H, systemic cyclosporine 2, 5, 10, and 15 mg/kg per day, respectively. After the animals were killed on postoperative day 2, 4, or 6, the transplanted lung, native lung, spleen, and blood were collected. Histologic studies, high-pressure liquid chromatography for trough cyclosporine concentrations, and reverse-transcriptase polymerase chain reaction for cytokine gene expression were performed.

RESULTS

Untreated animals showed grade 4 rejection by postoperative day 6. Aerosol cyclosporine prevented acute rejection in a dose-dependent fashion, with group D animals (3 mg/kg per day) showing minimal grade 1 changes. Among animals receiving systemic cyclosporine, only group H (15 mg/kg per day) controlled (grade 1) rejection. However, aerosol cyclosporine, at an 80% lower dose, achieved significantly lower concentrations of cyclosporine in the graft (12,349 vs 28,714 ng/mg, p = 0.002004) and blood (725 vs 3306 ng/ml, p = 0.000378). Group F (systemic 5 mg/kg per day) had higher cyclosporine concentrations in the blood than group D (p = 0.004572) and similar tissue concentrations (p = 0.115180), yet had grade 2 rejection. Reverse-transcriptase polymerase chain reaction demonstrated equivalent suppression of inducible nitric oxide synthase but a 20- to 25-fold higher expression of interleukin-6, interleukin-10, and interferon-gamma in group D versus group H recipient allografts.

CONCLUSION

Local delivery of cyclosporine by aerosol inhalation dose-dependently prevented acute pulmonary allograft rejection. Effective graft levels and low systemic drug delivery required significantly lower doses than systemic therapy alone. The gene expression of proinflammatory cytokines involved in allograft rejection was suppressed by aerosol cyclosporine therapy.

Review of immunosuppression for lung transplantation. Novel drugs, new uses for conventional immunosuppressants, and alternative strategies

The history, pharmacokinetics, mechanisms of action, and experimental as well as clinical data on the immunosuppressive potential of the novel drugs tacrolimus (FK506), sirolimus (rapamycin), mycophenolic acid (mycophenolate mofetil), and leflunomide (and its malononitriloamide analogues) are provided. Novel approaches with the following conventional immunosuppressants are outlined: methotrexate, aerosolized immunosuppression and the implementation of steroid taper. Total lymphoid irradiation and photopheresis for treatment of recurrent rejection are also discussed.