The concept of quality by design (QbD) initially was outlined in ICH Q8 guidance for drug-product development and later in Q11 for drug-substance development (1, 2). Since then, the QbD concept was further expanded to the development of analytical methods. FDA issued a 2015 guidance on analytical procedures and method validation for drugs and biologics (3). Although the agency did not explicitly state the requirement for implementation of QbD in analytical method development, the concept is embedded in its section…