Survival Analysis with nlmixr2

Introduction Survival or time-to-event (TTE) analysis models when something happens, not just whether it happens. The endpoint might be time to tumour progression, time to an adverse event, or time to treatment discontinuation, for instance. In this post we’ll illustrate how to fit parametric TTE models in nlmixr2 using its custom log-likelihood interface. For the purposes of this post, we’re going to simulate a two-arm randomised trial from a known Gompertz model, then recover the parameters with nlmixr2.

Open Source in Regulatory Review: nlmixr2 Developers Meet Regulators

The nlmixr2 development team, represented by Bill Denney, Lisa Hendricks, and I (Matt Fidler), recently gave a invited seminar to the FDA quantitative clinical pharmacology reviewers to discuss nlmixr2 and how open, community-built modeling tools can be helpful in regulatory settings. The conversation was constructive and forward-looking, and a clear theme emerged: anything that lets regulatory reviewers trust, reproduce, and exchange models across tools would be very useful. As we go through these reflections, I must add that these are my takeaways and are not necessarily the views of the FDA, nor are they necessarily the views of the companies or individuals represented by the nlmixr2 working group, or the R Consortium.

State-Dependent Dosing Properties in rxode2

Introduction A long-standing limitation in rxode2 was that the dosing-modifier expressions — rate(), dur(), f(), and alag() — could only reference things that did not depend on state. If you wanted infusion duration, bioavailability, or lag time to depend on the current concentration or any other ODE state variable, you were out of luck. rxode2 5.0.2 lifts that restriction. All four dosing modifiers, as well as model-event times (mtime()), can now reference state variables.

nlmixr2 and tidyvpc

VPCs – a new method for VPCs in nlmixr2 I am excited to announce a new VPC method available in nlmixr2 – tidyvpc. This method can be built on-top of previous code and provides slightly different visualizations than the vpc package. Below is an example that shows the two different methods: library(nlmixr2) ## ── Attaching packages ───────────────────────────────────────────────────────── nlmixr2 5.0.0 ── ## ✔ lotri 1.0.2 ✔ monolix2rx 0.0.6 ## ✔ nlmixr2data 2.

nlmixr2 inter occasion varibility

Inter-occasion variability Happy new year! With the holidays over we had the opportunity to celebrate many special occasions. I invite you to celebrate a new occasion for nlmixr2 – inter-occasion variability. We now support inter-occasion variability estimation in nlmixr2! Implementing inter-occasion variability in models To implement inter-occasion variability in nlmixr2 models you simply have to specify that the variable is an occasion variable, say occ: iov.cl ~ 0.1 | occ The ~ syntax is similar to how between subject variability is specified, the addition of | tells that this a between occ variability.