Simulx is a R function for easily computing predictions and simulating data from both Mlxtran and PharmML models. Simulx is based on MlxCompute, the model simulation engine developed by Lixoft. MlxCompute combines the Mlxtran language interpreter with the equation solvers to compute efficiently complex systems of ordinary differential equations (ODEs) and delayed differential equations (DDEs). Simulx takes advantage of the modularity of hierarchical models for simulating different components of a model: models for population parameters, individual covariates, individual parameters and longitudinal data, including continuous, count, categorical, and time-to-event data. simulx is also extremely flexible for defining complex dose regimens. Then, simulx will be the core of the next version of the DDMoRe Clinical Trial Simulator.