With all samples represented by a feature vector, now it is possible for us to construct our predictor using the machine learning approach. The NN (Nearest Neighbor) algorithm is quite popular in pattern recognition community owing to its good performance and simple-to-use feature. According to the NN rule [88] , the query sample should be assigned to the subset represented by its nearest neighbor. In this study, if the drug-target pair with the shortest distance is a positive sample, meaning that they can interact with each other, the sample for test is seen as a positive drug-target pair. Otherwise, the test sample is seen as a negative one.