Protein stabilization by cyclodextrins in the liquid and dried state ☆ Tim Serno a, ⁎, Raimund Geidobler b , Gerhard Winter b a Novartis Pharma AG, Biologics Process R&D, Pharmaceutical Development, 4056 Basel, Switzerland b Department of Pharmacy, Ludwig-Maximilians-University, 81377 Munich, Germany abstract article info Article history: Received 11 April 2011 Accepted 23 August 2011 Available online 1 September 2011 Keywords: Protein Cyclodextrin HPβCD Protein aggregation Lyophilization Liquid formulation Protein stabilization Non-ionic surfactant Monoclonal antibody Protein formulation Aggregation is arguably the biggest challenge for the development of stable formulations and robust manufacturing processes of therapeutic proteins. In search of novel excipients inhibiting protein aggregation, cyclodextrins and their derivatives have been under examination for use in parenteral protein products since more than 20 years and significant research work has been accomplished highlighting the great potential of cyclodextrins as stabilizers of therapeutic proteins. Oftentimes, the potential of cyclodextrins to inhibit protein aggregation has been attributed to their capabil- ity to incorporate hydrophobic residues on aggregation-prone proteins or on their partially unfolded inter- mediates into the hydrophobic cavity. In addition, also other mechanisms besides or even instead of complex formation play a role in the stabilization mechanism, e.g. non-ionic surfactant-like effects. In this review a comprehensive overview of the available research work on the beneficial use of cyclodextrins and their derivatives in protein formulations, liquid as well as dried, is provided. The mechanisms of stabili- zation against different kinds of stress conditions, such as thermal or surface-induced, are discussed in detail. © 2011 Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 2. Cyclodextrins for use in parenteral drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 2.1. Structure and physicochemical properties of cyclodextrins and their derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . 1087 2.2. Parenteral biocompatibility of cyclodextrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1088 3. Cyclodextrins as excipients for protein formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1089 3.1. Protein aggregation mechanisms in liquid protein formulations that can be affected by cyclodextrins . . . . . . . . . . . . . . . . 1089 3.2. Cyclodextrin protein interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1090 3.2.1. General molecular mechanism of complex formation between cyclodextrins and guest molecules . . . . . . . . . . . . . 1090 3.2.2. Cyclodextrin–protein interaction: structural aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1091 3.2.3. Stoichiometry and affinity of interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094 3.3. Cyclodextrins as inhibitors of protein aggregation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095 3.3.1. Reduction of aggregation due to binding between CDs and protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095 3.3.2. Reduction of aggregation induced by exposure to the air–water interface . . . . . . . . . . . . . . . . . . . . . . . . . 1095 3.3.3. Further mechanisms of stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098 3.3.4. Increased aggregation rates due to cyclodextrin addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098 3.3.5. No effect of cyclodextrins on protein stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098 3.4. Cyclodextrins as excipients for freeze- and spray-drying of protein solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098 3.4.1. Stresses arising from freeze- and spray drying processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1098 3.4.2. General mechanisms of stabilization by excipients during freezing, drying and in the dried state . . . . . . . . . . . . . . 1099 3.4.3. Possible mechanisms of stabilization provided by cyclodextrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1100 Advanced Drug Delivery Reviews 63 (2011) 1086–1106 ☆ This review is part of the Advanced Drug Delivery Reviews theme issue on “Formulating Biomolecules: Mechanistics Insights in Molecular Interactions”. ⁎ Corresponding author at: Novartis Pharma AG, Biologics Process R&D, Pharmaceutical Development, PO Box, CH-4002 Basel, Switzerland. Tel.: +41 61 6963545; fax: +41 61 3242167. E-mail address: tim.serno@novartis.com (T. Serno). 0169-409X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.addr.2011.08.003 Contents lists available at SciVerse ScienceDirect Advanced Drug Delivery Reviews journal homepage: www.elsevier.com/locate/addr