Mixing energy as an adjustment tool for aerodynamic behaviour of an inhaled product: In-vitro and in-vivo effects

This paper describes the development of a fixed dose dry powder combination of indacaterol maleate (Inda) and glycopyrronium bromide (Glyco) in Easyhaler® inhaler for a comparative pharmacokinetic (PK) study, as well as the outcome of such a study. The development aim was to produce formulations with three different in vitro dispersibility profiles for both Inda and Glyco. This so-called ‘rake’ approach allows for quantitation of the candidate formulations relative to the reference product Ultibro® Breezhaler® in terms of the key PK parameters. Three formulations (A, B and C) were produced based on the mixing energy concept. For both APIs, formulation A (lowest mixing energy) displayed the highest fine particle fractions and formulation C (highest mixing energy) the lowest. GMP manufacturing confirmed the performance of the three formulations. The candidate formulations were tested against the reference product in a single dose PK study in healthy volunteers. Clear differences in Inda plasma concentration profiles were observed between the treatments when administered concomitantly with charcoal, with Easyhaler A showing the highest C_max value and Easyhaler C the lowest. Easyhaler B was bioequivalent to Ultibro Breezhaler with regard to the primary PK parameters of Inda, C_max and AUC_72h. For Glyco, Easyhaler formulations A, B and C provided lower peak concentrations than Ultibro Breezhaler. For AUC_72h of Glyco_, Easyhaler B was bioequivalent to the reference product. Additional measures for adjustment of formulation performance can be foreseen, whose effects can be predicted based on mixing energy theory.