We perform molecule generation using REINVENT , an algorithm employing an RNN for SMILES sequence generation and policy-gradient RL to guide the generation towards new SMILES that exhibit the desired properties according to a flexible scoring function, s(x) (Equation ), that can include various scoring components. In this work, we specifically address the case where s(x) includes at least one QSAR or QSPR model as a scoring component (i.e., K > 0).