Scale-up of Fluid Bed Granulation Using a Scale-Independent Parameter and a Process Model

A practice-based approach for the scale-up of fluid bed granulation in the context of drug product development is presented and evaluated in this work in the context of clinical drug product manufacturing development. The approach is based on the use of a scale-independent parameter, the evaporation energy to drying capacity ratio (EE/DC), and a process model. The EE/DC ratio is used to quantify, in one scale-independent parameter, the combined effect of the most impacting process parameters and to identify the spray rates to be used at different scales to achieve similar granule moisture rate of change. The process model is used to de-risk scale-up, by allowing the consideration of equipment differences across scales and process dynamics, which are aspects not accounted for by the EE/DC ratio. This approach was tested by scaling up the fluid bed granulation process of two formulations, one placebo and one active, from laboratory to pilot scales. This work showed how it was possible to use a simple scale-up approach coupled with a process model to achieve right first-time scale-up of a fluid bed granulation process and show how a placebo formulation could be used instead of active material, first to define the process at laboratory scale and then to de-risk the scale-up, by identifying scale-dependent differences.