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External control arms & single-arm trials

Design an external control arm that survives regulatory scrutiny

Population comparability, comparator selection and pre-specification are where external control arms are weakest, and exactly where reviewers look first. This hub helps teams running single-arm trials design the comparator evidence regulators actually accept.

Get the ECA design checklist

Start here: the ECA Design Checklist

The checks we run before committing to an external control arm design: population, comparator data, endpoint alignment and the matching decisions agencies probe hardest. Most designs are weakest on points 3 and 7. Free, and yours to keep.

Download the checklist

The Estimands Playbook

The E9(R1) framework in plain language, with protocol wording that survives review.

Get the playbook

Brief: Settled before enrolment

Every question FDA asks about a single-arm trial is settled before enrolment. Four pages, free.

Get the brief

More free briefs on this topic: Two bars, not one

Watch: the video series

Latest from this hub

The EMA vs Single-Arm Trials: 10 Lessons from the EMA Reflection Paper

The EMA vs Single-Arm Trials: 10 Lessons from the EMA Reflection Paper

Ten practical lessons from the EMA reflection paper on when single-arm trials hold up, and when regulators push back.

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FDA Guidance on External Control Arms: A Checklist For Drug Developers

FDA Guidance on External Control Arms: A Checklist For Drug Developers

A drug developer's checklist for meeting the FDA's expectations on external control arms, from comparability to pre-specification.

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Randomisation has exactly one job. An external control arm has to do it by hand

Randomisation has exactly one job. An external control arm has to do it by hand

Why an external control arm must reproduce by hand, through matching and weighting, the covariate balance that randomisation delivers automatically.

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The external control arm design checklist: 12 points that survive scrutiny

The external control arm design checklist: 12 points that survive scrutiny

Twelve design points that keep an external control arm credible when regulators pressure-test it.

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Target trial emulation for non-statisticians

Target trial emulation for non-statisticians

A plain-language guide to target trial emulation, the framework that turns messy observational data into a credible external comparison.

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The external control arm that got checked against reality: blinatumomab's acceptance

The external control arm that got checked against reality: blinatumomab's acceptance

How blinatumomab's external control arm held up when its estimates were later checked against a randomised trial, and why regulators accepted it.

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Weighing an external control arm?

This is one of the highest-stakes design calls a program ever makes, and the hardest to unwind once the protocol locks. If you are deciding between arms, data sources or matching approaches, get in touch while the decision is still cheap to change.

Discuss your design
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