PERSPECTIVES
An Industry Perspective on the Monitoring of Subvisible Particles as a Quality Attribute for Protein Therapeutics

https://doi.org/10.1002/jps.22097Get rights and content

ABSTRACT

Concern around the lack of monitoring of proteinaceous subvisible particulates in the 0.1–10 mm range has been heightened (Carpenter et al., 2009, J Pharm Sci 98: 1202–1205), primarily due to uncertainty around the potential immunogenicity risk from these particles. This article, representing the opinions of a number of industry scientists, aims to further the discussion by developing a common understanding around the technical capabilities, limitations, as well as utility of monitoring this size range; reiterating that the link between aggregation and clinical immunogenicity has not been unequivocally established; and emphasizing that such particles are present in marketed products which remain safe and efficacious despite the lack of monitoring. Measurement of subvisible particulates in the < 10 μm size range has value as an aid in product development and characterization. Limitations in measurement technologies, variability from container/closure, concentration, viscosity, history, and inherent batch heterogeneity, make these measurements unsuitable as specification for release and stability or for comparability, at the present time. Such particles constitute microgram levels of protein with currently monitored sizes ≥ 10 μm representing the largest fraction. These levels are well below what is detected or reported for other product quality attributes. Subvisible particles remain a product quality attribute that is also qualified in clinical trials.

Section snippets

INTRODUCTION

Therapeutic proteins have made an immense contribution to treatment of human diseases and represent an increasingly important part of the armamentarium available for this purpose. The life-saving benefits of products derived from recombinant protein technology, starting from the very first product insulin in 1982, have never been in dispute. However, concerns have always been present about the potential adverse consequences of aggregation of the protein in the product being dosed. Aggregation

AGGREGATION, SUBVISIBLE PARTICULATES, AND IMMUNOGENICITY

Multiple publications have implied that protein aggregates may be one of the factors, if not the major factor, for tolerance reversal and induction of immune response against protein biotherapeutics.1., 9., 10. This conclusion is based on theoretical considerations, circumstantial evidence obtained from investigations conducted on clinical products, as well as data from animal studies using artificially induced and stabilized aggregates.11., 12., 13., 14. Despite the fact that all

STATE OF CURRENT PROTEIN PRODUCTS

The specification for protein oligomers (generally measured by SEC) in the therapeutic proteins on the market are set prior to clinical studies and qualified in these studies. Subvisible particles larger than 10 μm are routinely measured for these products, while the range below 10 μm is not. Despite the lack of a complete picture about subvisible particles/aggregates, it is likely that such particulates/aggregates (including those below 10 μm) existed during clinical studies and are present in

SUBVISIBLE PARTICLES AND THE MEASUREMENT GAP

The current standard limits or specifications for subvisible particles and information about methods in the compendia are summarized in Table 2. The current standards arose to mitigate the risk associated with the presence of extraneous particles in intravenous injection solutions. The particle sizes monitored (≥ 10 and ≥ 25 μm) were set based on the risk for blood vessel occlusion by intravenous administration of small particles. Modern aseptic production technologies have reduced the occurrence

VALUE OF MONITORING SUBVISIBLE PARTICLES OVER A BROAD RANGE

Available observations, albeit limited, suggest that particle counts within the various size ranges are positively correlated. The data presented below (Fig. 6) on a lyophilized product stored under stressed conditions shows that subvisible particles in all size ranges increased concurrently. The number of particles in size range ≥ 10 μm correlated with the counts for the smaller sizes.

A similar correlation between the subvisible particle counts in various size ranges was detected for another

CONCLUSIONS AND RECOMMENDATIONS

  • (1)

    Concerns about aggregation as a potential cause of immunogenicity in human biothera-peutics have been around for a long time. The multiplicity of determinants of immunogenicity in a clinical setting makes the deconvolution of factors very difficult, and no direct evidence from clinical studies has been forthcoming to demonstrate that aggregates are a true dominant risk factor. It is also difficult to determine the immunogenicity potential of naturally occurring aggregates of a particular human

ACKNOWLEDGMENTS

The authors would like to acknowledge a number of people from various organizations who helped to generate the data and/or shape the discussions: Hatsuki Asahara, Nancy Barbour, Shawn Cao, Art Chirino, Adriana Chynoweth, Lisa Erickson, Erwin Freund, Michael Grace, Gino Grampp, Richard Harms, Wenchang Ji, Yijia Jiang, Nancy Jiao, Chulani Karunatilake, Brent Kendrick, Bruce A. Kerwin, Hans Koll, Ian Langdon, Tony Mire-Sluis, David Palmlund, Matt Rhyner, Thomas Schreitmü ller, Deepak Sharma, Li

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