External Control Borrowing for Rare Disease Trials

Implements causal inference methods for incorporating external control data into randomized controlled trials (RCTs) with longitudinal outcomes. Provides an analysis module supporting weighting-based methods such as inverse probability weighting (IPW) and augmented inverse probability weighting (AIPW), difference-in-differences (DID), and synthetic control approaches for borrowing external control information, as well as a simulation module for generating trial and external control data, evaluating estimator performance via Monte Carlo studies, and conducting power analyses for sample size determination. Methods are based on Zhou et al. (2025) and Zhou et al. (2024) .

rdborrow

Installation

Install the released version from CRAN:

install.packages("rdborrow")

Or install the development version from GitHub:

# install.packages("pak")
pak::pak("Genentech/rdborrow")

Documentation

• Package website
• Getting started
• Function reference

How to cite the manuscript

Shi L, Pang H, Chen C, Zhu J. rdborrow: an R package for causal inference incorporating external controls in randomized controlled trials with longitudinal outcomes. J Biopharm Stat. 2025 Oct;35(6):1043-1066. doi: 10.1080/10543406.2025.2489283. PMID: 40296214.

@article{shi2025rdborrow,
  title = {rdborrow: an R package for causal inference incorporating external controls in randomized controlled trials with longitudinal outcomes},
  author = {Lei Shi and Herbert Pang and Chen Chen and Jiawen Zhu},
  journal = {Journal of Biopharmaceutical Statistics},
  year = {2025},
  volume = {35},
  number = {6},
  pages = {1043--1066},
  doi = {10.1080/10543406.2025.2489283}
}

How to cite the package

Shi L, Secrest MH, Pang H, Chen C, Zhu J (2026). rdborrow: An R package for Causal Inference Incorporating External Controls in Randomized Trials with Longitudinal Outcomes. R package version 0.0.5.0, https://genentech.github.io/rdborrow/.

@Manual{,
  title = {rdborrow: An R package for Causal Inference Incorporating External Controls in Randomized Trials with Longitudinal Outcomes},
  author = {Lei Shi and Matthew H Secrest and Herbert Pang and Chen Chen and Jiawen Zhu},
  year = {2026},
  note = {R package version 0.0.5.0},
  url = {https://genentech.github.io/rdborrow/}
}