The global market for biotherapeutics has expanded extensively over the past decade and is projected to account for more than a quarter of the pharmaceutical market by 2020, with sales exceeding US$290 billion (1). Continued expansion of the biosimilar marketplace has led to many commercial opportunities and technical challenges. The biological systems used to manufacture such drug products are inherently variable — a feature that has important consequences for the reproducibility, safety, and efficacy of the resulting products. Therefore, a…