Formulation, stability and pharmacokinetics of sugar-based salmon calcitonin-loaded nanoporous/nanoparticulate microparticles (NPMPs) for inhalation Maria Inês Amaro a, *, Frederic Tewes a, b , Oliviero Gobbo a , Lidia Tajber a , Owen I. Corrigan a , Carsten Ehrhardt a , Anne Marie Healy a a School of Pharmacy and Pharmaceutical Sciences, Trinity College, University of Dublin, Dublin 2, Ireland b INSERM ERI-23, Pôle Biologie-Santé, Faculté de Médecine & Pharmacie, Université de Poitiers, 40 av. du Recteur Pineau,86022 Poitiers Cedex, France ARTICLE INFO Article history: Received 13 November 2014 Accepted 1 February 2015 Available online 3 February 2015 Keywords: Salmon calcitonin Inhalation Non-reducing sugars Stability Pharmacokinetics ABSTRACT A challenge exists to produce dry powder inhaler (DPI) formulations with appropriate formulation stability, biological activity and suitable physicochemical and aerosolisation characteristics that provide a viable alternative to parenteral formulations. The present study aimed to produce sugar-based nanoporous/nanoparticulate microparticles (NPMPs) loaded with a therapeutic peptide – salmon calcitonin (sCT). The physicochemical properties of the powders and their suitability for pulmonary delivery of sCT were determined. Production of powders composed of sCT loaded into raffinose or trehalose with or without hydroxypropyl-b-cyclodextrin was carried out using a laboratory scale spray dryer. Spray dried microparticles were spherical, porous and of small geometric size (2 mm). Aerodynamic assessment showed that the fine particle fraction (FPF) less than 5 mm ranged from 45 to 86%, depending on the formulation. The mass median aerodynamic diameter (MMAD) varied between 1.9 and 4.7 mm. Compared to unprocessed sCT, sCT:raffinose composite systems presented a bioactivity of approximately 100% and sCT:trehalose composite systems between 70–90% after spray drying. Storage stability studies demonstrated composite systems with raffinose to be more stable than those containing trehalose. These sugar-based salmon calcitonin-loaded NPMPs retain reasonable sCT bioactivity and have micromeritic and physicochemical properties which indicate their suitability for pulmonary delivery. Formulations presented a similar pharmacokinetic profile to sCT solution. Hence the advantage of a dry powder formulation is its non-invasive delivery route and ease of administration of the sCT. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction Pulmonary drug delivery using dry powder inhalers (DPIs) is an important research area impacting on the treatment of respiratory diseases such as asthma and chronic obstructive pulmonary disease. The lung is an efficient port of entry for drugs into the bloodstream due to the large and highly vascularised surface area (80–100 m 2 /adult and 5 l blood/min respectively), its thin non- ciliated epithelial barrier (0.1–0.2 mm), relatively low enzymatic activity compared to the stomach, and most importantly, the avoidance of hepatic first pass metabolism (Patton,1996; Telko and Hickey, 2005; Daniher and Zhu, 2008; Pilcer and Amighi, 2010). The main advantage of inhalation is the non-invasive drug targeting. In recent years, inhalation has emerged as a possible alternative to parenteral administration for the systemic delivery of peptides and proteins (Patton, 1996; Patton et al., 2004; Daniher and Zhu, 2008). Exubera TM was a marketed insulin dry powder inhaler that presented good stability and bioavailability, nevertheless it was withdrawn due to poor sales (Kwok and Chan, 2008). In late June 2014 Afrezza 1 , a new DPI insulin product based on the Techno- sphere technology by Mannkind (US) was approved by FDA (Mannkind Corporation, 2014). Studies have demonstrated that aerosol particles must present a specific aerodynamic diameter, i.e., <5 mm, to clear the oropharyngeal impaction barrier, and should be <3 mm, to reach the terminal bronchi and the alveoli (Johnson, 1997; Telko and Hickey, 2005; Chow et al., 2007; Daniher and Zhu, 2008; Pilcer and Amighi, 2010). Hence, the DPI aerosol cloud should be constituted * Corresponding author. Tel.: +353 1 8963317; fax: +353 1 8962810. E-mail address: amarom@tcd.ie (M.I. Amaro). http://dx.doi.org/10.1016/j.ijpharm.2015.02.003 0378-5173/ ã 2015 Elsevier B.V. All rights reserved. International Journal of Pharmaceutics 483 (2015) 6–18 Contents lists available at ScienceDirect International Journal of Pharmaceutics journal homepage: www.elsevier.com/locate/ijpharm