“…In the period since the first workshop, there has been significant activity in this area, particularly with the application of physiologically based biopharmaceutics modelling (PBBM), to support the development of CRDSs. In addition to publications describing the use of PBBM to support product development [ 2 , 3 , 4 , 5 , 6 ] and continued dialogue between academic, industrial, and regulatory scientists [ 7 , 8 , 9 ], the FDA has published a Draft Guidance document on the use of physiologically based pharmacokinetic (PBPK) analyses to support oral drug product development, manufacturing changes, and controls [ 10 ]. The aim of the 2021 webinar series was to continue the dialogue from the previous workshop and share and discuss progress and challenges through scientific presentations and Q&A sessions.…”