Interactive Pharmacometric Simulations and Model Exploration with e-Campsis
Authors: Lindauer Andreas , Luyckx Nicolas , Van Schaick Erno , Hénin-Devessiere Emilie , Shah Sajid Ali , Blaizot-Besse Stéphanie , Lobet Sarah , Noguine Pierre-Alexandre , Laveille Christian 
Published: February 2025

Objectives: Develop a web app to easily setup PK/PD simulations. Enable online model code editing and simulation datasets generation. Include a library with 100+ models (PK, PD, TMDD, etc.) for immediate simulation without pharmacometrics programming knowledge. Automatically generate downloadable R code for documentation and offline execution to maintain full reproducibility.Methods: The e-Campsis simulator is built on the open-source packages campsis [1] and campsismod [2], using the S4 object system in R to structure pharmacometric models and simulation datasets. Campsis provides an abstraction layer delegating simulation work to mrgsolve [3] or rxode2 [4].The e-Campsis graphical user interface comprises the following key sections:Model: Users select a model from the library or upload a Campsis model, which is displayed with syntax highlighting in an editor window. Parameters appear in dynamic JavaScript tables for modification.Trial Design: Users define the study design (amounts, times, intervals) and observation times, specify covariates, and enter dose adaptation formulas if needed.Simulation: e-Campsis runs the simulation and plots results for any desired outputs in the model code. The tab has three graphical components: parameter values and scenarios, settings configuration (variability components, seed number, simulation engine), and plot customization using ggplot2 or plotly.Post-processing: (pro version only) Simulation results can be further analyzed per individual by e.g. deriving non-compartmental PK metrics, such as AUC, Cmax or Tmax, as well as the percentage above/below a threshold level. User-defined functions as R-code enable full customization. Summary statistics (geometric mean, CV%, etc.) are derived from individual metrics and displayed in an HTML table using gtsummary [5].Download: This tab allows the user to preview the generated R code and to download the entire project. Using this download, the user is able to reproduce the simulation results offline in R using Campsis.Results: e-Campsis was released to the pharmacometrics community in June 2023 and is freely accessible at www.e-campsis.com. An advanced version with additional features like saving/loading the state of the application (input fields, etc.), automatic import and translation of NONMEM code, and replicate simulations was first released in December 2023 and is under active development.Conclusion: The web-based application e-Campsis was developed to satisfy different needs: It allows the user to explore models, simulate different designs and analyze the output. The automatic generation of human readable R-code ensures reproducibility and consistency within an organization. e-Campsis can greatly support the communication of modelling and simulation results with clinical teams by interactive simulations in meetings.Citations: [1] https://github.com/Calvagone/campsis [2] https://github.com/Calvagone/campsismod [3] https://github.com/metrumresearchgroup/mrgsolve [4] https://github.com/nlmixr2/rxode2[5] https://www.danieldsjoberg.com/gtsummary/