Estimation and Safety of Aerosolized

In vitro and in vivo studies suggested that aerosolizing E25 would deliver the therapeutic primarily to the ELE with low and limited delivery to the serum. The quantity delivered to lung interstitium could not be determined. To evaluate the potential efficacy of topical delivery to the lung surface and to estimate dose, a suitable animal model would be advantageous. However, no suitable animal model was available. Rodent models of asthma could not be used to evaluate efficacy since E25 does not bind to rodent IgE. Also, although E25 does bind to monkey IgE, at the time of these studies there was no well-characterized monkey model of asthma. We decided that the fastest way to evaluate the efficacy of aerosolized E25 was to use a human bronchoprovocation model of asthma since systemic delivery of E25 was found to be efficacious in this model (21,22). 

To evaluate aerosolized E25 in humans, an estimated dose and the safety of inhaled E25 needed to be determined. Cynomolgus monkeys were used for these estimates. 

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The dose of inhaled E25 was estimated from phamacokinetic studies in cynomol-gus monkeys. Monkeys were exposed to a single dose of aerosolized E25 for 20 minutes by head-only inhalation using a Pari-IS2 nebulizer. Total volume inhaled during the aerosol exposure was measured and the concentration of E25 in the inhaled air was determined by filter sampling. Aerosol droplet size was also measured by cascade impaction. The estimated deposited dose in the lungs from these determinations was 117 p.g. To evaluate the kinetics of E25 deposited on the lung surface, samples of the ELF were taken by BAL and the total E25 concentration measured by ELISA. Samples of BAL were taken at 0, 1, 2, 4, 8, 12, and 24 hours postinhalation. Only two BAL samples were taken from a single animal. Two animals were used for each time point. Urea concentrations in BAL fluid were used for dilution corrections to estimate ELF (23). 

Cynomolgus monkeys were used to evaluate the safety of inhaled E25. Two studies, 7- and 60-day exposure, were performed to evaluate the safety of this novel therapeutic prior to administration to humans. General safety and tissue responses along with potential antigenicity to inhaled E25 were evaluated. Development of antibodies directed against E25 would be expected in these safety studies due to the differing homology between the humanized monoclonal antibody (E25) and monkey IgG (24). 

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