By Dawn Downey
Unique challenges arise in the development and scale-up of traditional sterile drug product manufacturing processes. During process development and again during commercial manufacturing, the scope of drug product batch size is often difficult to determine. This presents a great hurdle because key equipment such as tanks and mixing systems must be ordered far in advance to accommodate the long lead times needed to design, build, and qualify the systems. As a result, the project either slows to adjust for more accurate information, or equipment is designed and built based on vague assumptions. Unfortunately, designing and building equipment based on vague assumptions often results in equipment that is either oversized or undersized. A continuous formulation process, whereby the components of the batch are fed continuously until the desired batch size is achieved, can alleviate this dilemma. Thus, the expectation that the batch size is defined during process development or commercial scale-up is eliminated.