The first finding is the strong correlation (R 2 = 0.82) between CACO-2 and MDCK (Fig. ). This correlation is expected because both methods are cell-based methods, and their strong correlation was described by Irvine et al. From the previous section, we know the PAMPA dataset contains a mixture of apparent and intrinsic permeabilities that need to be differentiated if the data are to be compared. Fig. is the correlation among CACO-2 & MDCK vs intrinsic PAMPA. This correlation is very weak (R 2 = 0.03) because, in contrast to PAMPA, the CACO-2 and MDCK methods can provide only apparent permeability. On the other hand, Fig. shows the correlation (R 2 = 0.44) between CACO-2 & MDCK vs apparent PAMPA. This correlation is unsurprisingly stronger because the PAMPA apparent permeabilities correlate well with CACO-2 and MDCK data. This observation is consistent with the literature because the correlation among these methods was already described in the literature (PAMPA and CACO-2 were described by Zhu et al. , MDCK and PAMPA were published by von Richter et al. ). However, in addition to the membranes, the cell-based methods CACO-2 and MDCK also have membrane transport proteins, which can influence the transport of molecules through the membrane, and thus lower the correlation. However, the correlation between CACO-2 and PAMPA and MDCK and PAMPA indicates passive diffusion as a dominant transport mechanism in the case of both cell monolayers . A good correlation between CACO-2 & MDCK vs apparent PAMPA can indicate a smaller role of membrane transporters in this dataset.