We compared and evaluated the initial molecule and generated molecule in terms of the similarity given by the Tanimoto coefficient based on the ECFP4 fingerprints, except for the value of the evaluation function. However, in practice, lead optimization is expected to maintain not the similarity but also the potency and selectivity to the target. Although similarity may be correlated to these properties, it is more appropriate to evaluate in terms of the potency and selectivity. Considering the comparison of the initial molecule and generated molecule by such a metric for drug efficacy, this method is not expected to retain a high percentage of the original drug efficacy. The search space of this method is narrowed down to a molecule-like graph by the GCN model, and biased by MCTS toward regions with higher values of the evaluation function. Thus, if specific properties such as drug effects are to be considered, they must be explicitly handled in the evaluation function. Masking the evaluation function to preserve important substructures with respect to the property of interest is also effective.