PCA plots were based on the method described previously in literature . The 42-dimension MQN fingerprint was calculated with the JChem Library 18.22.0 from ChemAxon (www.chemaxon.com) for each of the molecules in the dataset. Then, without any normalization or standardization, a Principal Component Analysis (PCA) was performed on the 42-dimensional resulting dataset. The two first principal components were selected and normalized to values between 0 and 𝑤 or and molecules were organized in buckets. Each bucket represents a pixel ( , ) in the resulting 𝑤 × plot with a black background. A descriptor was also calculated for all molecules in each bucket and the average and count were calculated and normalized to the range