Evaluating the suitability of using rat models for preclinical efficacy and side effects with inhaled corticosteroids nanosuspension formulations.

Inhaled corticosteroids (ICS) are often prescribed as first-line therapy for patients with asthma Despite their efficacy and improved safety profile compared with oral corticosteroids, the potential for systemic side effects continues to cause concern. In order to reduce the potential for systemic side effects, the pharmaceutical industry has begun efforts to generate new drugs with pulmonary-targeted topical efficacy. One of the major challenges of this approach is to differentiate both efficacy and side effects (pulmonary vs. systemic) in a preclinical animal model. In this study, fluticasone and ciclesonide were used as tool compounds to explore the possibility of demonstrating both efficacy and side effects in a rat model using pulmonary delivery via intratracheal (IT) instillation with nanosuspension formulations. The inhibition of neutrophil infiltration into bronchoalveolar lavage fluid (BALF) and cytokine (TNFα) production were utilized to assess pulmonary efficacy, while adrenal and thymus involution as well as plasma corticosterone suppression was measured to assess systemic side effects. Based on neutrophil infiltration and cytokine production data, the ED50s for ciclesonide and fluticasone were calculated to be 0.1 and 0.03 mg, respectively. At the ED50, the average adrenal involution was 7.6 ± 5.3% for ciclesonide versus 16.6 ± 5.1% for fluticasone, while the average thymus involution was 41.0 ± 4.3% for ciclesonide versus 59.5 ± 5.8% for fluticasone. However, the differentiation became less significant when the dose was pushed to the EDmax (0.3 mg for ciclesonide, 0.1 mg for fluticasone). Overall, the efficacy and side effect profiles of the two compounds exhibited differentiation at low to mid doses (0.03-0.1 mg ciclesonide, 0.01-0.03 mg fluticasone), while this differentiation diminished at the maximum efficacious dose (0.3 mg ciclesonide, 0.1 mg fluticasone), likely due to overdosing in this model. We conclude that the rat LPS model using IT administration of nanosuspensions of ICS is a useful tool to demonstrate pulmonary-targeted efficacy and to differentiate the side effects. However, it is only suitable at sub-maximum efficacious levels.

Pharmacokinetic and pharmacodynamic evaluation of the suitability of using fluticasone and an acute rat lung inflammation model to differentiate lung versus systemic efficacy.

Inhaled corticosteroids (ICSs) are often prescribed as the first line therapy for pulmonary diseases such as asthma. The biggest concern of using steroid therapy is the systemic side effects at high dose. To reduce the side effects, the pharmaceutical industry has been putting effort to generate new drugs with maximized topical efficacy. One of the key challenges is to differentiate efficacy from local versus systemic contribution in preclinical animal models. Fluticasone with various formulations was used as a model compound to explore the possibilities to demonstrate lung targeted efficacy by intratracheally instillation in the lipopolysaccharide induced inflammation rat model. Fluticasone formulations contained various surfactant concentrations and particle sizes to achieve lung retention and lower systemic exposure. Neutrophil infiltration in broncoalveolar lavage fluid and cytokine production in whole blood were measured to assess pulmonary efficacy versus systemic efficacy. PK/PD characterization of fluticasone with various formulations in the rat inflammation model provided an integrated approach in preclinical to evaluate lung targeted efficacy for ICS. Our study concluded that the combination of the rat LPS model and fluticasone is not suitable to use for establishing potency and dose requirement for new drug candidate designed for topical only efficacy.

A method for determining whether hypotension caused by novel compounds in preclinical development results from histamine release.

INTRODUCTION: Many therapeutic agents stimulate histamine release from mast cells, which results in a decrease in blood pressure. The purpose of this study is to establish a method to determine if the mechanism of action, or one of the mechanisms, of hypotensive compounds is related to the release of histamine. The method was developed using a novel hypotensive compound, SC-372. METHODS: In Inactin anesthetized rats, after intravenous administration of SC-372 (0.3-7 mg/kg), the 2 and 7 mg/kg resulted in a dose-dependent decrease in blood pressure. Histamine (0.1 and 1 mg/kg) was injected intravenously to establish whether histamine release was the mechanism of action for the hypotension induced by SC-372. Compound 48/80 (0.1 mg/kg, promotes histamine release) and Cromolyn (1 mg/kg/min, [5 min], prevents histamine release from mast cells) were characterized and used intravenously in combination with/or compared to SC-372. RESULTS: Histamine resulted in a decrease in blood pressure that was unaffected by Cromolyn (1 mg/kg). Administration of Compound 48/80 resulted in a rapid reduction of systemic blood pressure. Intravenous infusion of Cromolyn prior to the injection of Compound 48/80 significantly attentuated the hypotensive response and the increase in histamine levels in the plasma. Intravenous administration of SC-372 resulted in a rapid reduction in blood pressure with a profile similar to that of Compound 48/80. When the rats were treated with Cromolyn prior to the administration of SC-372, both the blood pressure and plasma histamine levels were maintained at their pretreatment control levels. DISCUSSION: These data indicate that Compound 48/80 and Cromolyn can be used in rats to screen for histamine release-dependent drug-induced hypotension and suggest that the rapid decrease in blood pressure caused by SC-372 may result from histamine release from mast cells.

Administration of a small molecule tissue factor/factor VIIa inhibitor in a non-human primate thrombosis model of venous thrombosis: effects on thrombus formation and bleeding time.

INTRODUCTION: Pharmacological treatment of deep vein thrombosis (DVT) in the future may target inhibitors of specific procoagulant proteins. This study used a non-human primate model to test the effect of PHA-798, a specific inhibitor of the tissue factor/Factor VIIa complex (TF/VIIa), on venous thrombus formation. MATERIALS AND METHODS: PHA inhibits the TF/VIIa complex with an IC(50) of 13.5 nM (K(i) 9 nM) and is more than 2000-fold selective for the TF/VIIa complex with respect to IC(50)s for factor Xa and thrombin. In the model, a thrombogenic surface was introduced into the vena cava of a primate, and the amount of thrombus accumulated after 30 min was determined. RESULTS: PHA-798 reduced thrombus formation on the thrombogenic surface in a dose-dependent manner (56+/-1.9% and 85+/-0.3% inhibition with 100 and 200 microg/kg/min PHA-798, respectively) indicating that the model is sensitive to TF/VIIa inhibition. Treatment with 1 mg/kg intravenous (IV) acetyl salicylic acid (ASA) resulted in only a slight (4-12%), non-significant inhibition of thrombus formation. However, the combination of 100 microg/kg/min PHA-798 and 1 mg/kg ASA resulted in an 89% inhibition of thrombus formation. Additionally, while ASA alone increased bleeding time (BT) from 3.3 min at baseline to 4.6 min following treatment, addition of PHA-798 (100 microg/kg/min) to ASA did not significantly increase the BT further (4.7 min). CONCLUSIONS: The results of this study indicate that inhibition of TF/VIIa may be safe and effective for the prevention of the proprogation of venous thrombosis and that the combination of ASA and PHA may provide increased efficacy with little change in safety.