What Regulators Want to See in Surrogate Endpoints Today 

Surrogate endpoints have always played a major role in speeding up drug development, especially in oncology and rare diseases. They use early indicators to demonstrate efficacy earlier or more efficiently than can be acheived with traditional endpoints. But as these accelerated programs have become more common, regulators are looking more closely at how those early signals translate into real patient outcomes. 

Expectations Have Changed 

Expectations have evolved, especially in recent years, as regulators have introduced new guidance and initiatives to ensure surrogate endpoints are scientifically robust and clinically meaningful. Both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) expect surrogate endpoints to do more than suggest possible benefit. They must show a reliable link to meaningful improvement in patient health. 

This higher standard doesn’t change the purpose of the Accelerated Approval pathway, but it does raise the bar for evidence quality. Regulators expect a clear explanation of why the chosen endpoint matters, how it will be measured, and what plan is in place to confirm results once the drug reaches the market. In short, a surrogate endpoint must demonstrate both scientific credibility and practical relevance. 

Proving the Connection 

Examples of surrogate endpoints might include tumor shrinkage, biomarker changes, or measures of disease progression. These indicators can be valuable, but regulators now want stronger proof that what happens in the lab or early clinical stages will actually improve patients’ lives. This creates a “catch 22” for sponsors, particularly when proposing a new surrogate endpoint for an orphan or rare disease: regulators require robust evidence that a surrogate endpoint truly predicts clinical benefit but generating that evidence can be difficult—especially if the endpoint isn’t already well established and/or supporting data is scarce. Sponsors may find themselves unable to move forward quickly because sufficient supporting data for the surrogate endpoint is not yet available, yet unable to generate the necessary evidence without regulatory acceptance of the endpoint. Early and transparent dialogue with agencies can help clarify expectations and identify the most feasible path forward. 

Sponsors can build a stronger case by: 

• Showing how the endpoint ties directly to the drug’s mechanism of action, through small bespoke experiments or collecting data as part of Phase I or II trials.
• Explaining how changes in the endpoint connect to meaningful outcomes in real patients.
• Using data from earlier studies or real-world evidence to reinforce that connection. 
• A surrogate endpoint that looks promising but lacks biological or clinical support can slow review or block approval entirely.

Follow-Through Matters 

Recent updates under the Prescription Drug User Fee Act (PDUFA VII) have made post-approval verification a central focus. Regulators now expect sponsors to have their confirmatory studies underway, or at least fully designed, by the time a product is approved through an accelerated pathway. 

This expectation comes from experience. In the past, some programs delivered early success but took too long to verify benefit after approval. Today, agencies require assurance that sponsors have the resources and structure to deliver those follow-up results on schedule. 

For sponsors, that means planning earlier, aligning teams across functions, and treating post-approval studies as part of the overall development plan, not a separate phase that starts later. 

How Regulators Evaluate Evidence 

When agencies review a proposed surrogate endpoint, they look for three core elements: 

1. Strong scientific rationale – Does the biology make sense? Is there a clear link between the endpoint and how the drug works?
2. Consistent evidence – Have other studies or datasets shown the same pattern between the surrogate and the clinical outcome?
3. Reliable measurement – Are the tools and methods for measuring the endpoint standardized and reproducible?

When all three elements are in place, regulators are more likely to support the proposed endpoint early in development. 

Room for Innovation 

While expectations are higher, there’s also strong support for robust scientific and methodological innovation. Under PDUFA VII, programs like the Rare Disease Endpoint Advancement (RDEA) initiative and the Model-Informed Drug Development pilot give sponsors new ways to propose and validate innovative measures. 

Sponsors exploring novel biomarkers, imaging-based endpoints, or other innovative measures can use these programs to get early input and feedback. The EMA’s Qualification of Novel Methodologies program offers a similar opportunity for European submissions. These pathways show that regulators are open to innovation, when it’s supported by strong science and a clear plan. 

Building Confidence Through Strong Design 

Even the best surrogate endpoint can fail without a solid study design. Sponsors should bring statistical expertise into the process early to ensure the data behind the endpoint will stand up to review. 

That means designing studies with the right sample size, testing for consistency, and documenting data handling and analysis in a transparent way. These steps build confidence and show regulators that conclusions are based on sound evidence, not optimistic interpretation. 

Accountability Defines the New Era 

The world of surrogate endpoints is evolving quickly. Regulators are still eager to help sponsors bring therapies to patients faster, but they expect sponsors to show a clear, evidence-based path from early measurement to lasting benefit. 

The question has shifted from, “Can we measure something early?,” to “Can we prove that what we measure really matters?” 

Sponsors who plan for that level of accountability from the start, by aligning science, statistics, and strategy, will find regulators more receptive and timelines more predictable. 

For a deeper dive into these topics, watch the full “A Practical Guide to Expedited Regulatory Pathways” webinar on demand. The insights in this article are drawn directly from the expert discussion featured in this session. 

 Access the webinar: Click here