The Final Mile of Patient Enrollment

A Site Perspective on Cardiometabolic Trials

By: Tom Kreamer, MD, Chief Medical Officer

As large cardiometabolic trials in areas like diabetes, obesity, MASH/NASH, heart failure, and CVOTs approach their enrollment targets, sponsors, CROs, and sites face a coordination challenge: closing enrollment smoothly, without disrupting participants already in the screening or randomization process. This final stretch — the “final mile” — differs from planned buffers built in for screen failure or attrition. It is the operational work of bringing enrollment to a controlled stop once the target is in sight, and it depends on tight communication across every party involved.

A few features of cardiometabolic trials make coordination more demanding:

• Large, dispersed site networks (150–400 sites, 20+ countries) where closure notices take time to reach every site.
• Competitive, multi-site enrollment structures that reward sites for keeping candidates moving through screening.
• Multistep screening pipelines and central review requirements — HbA1c, BMI, fibrosis stage, ejection fraction — that introduce biologic variability and add time before eligibility can be confirmed, so candidates are often mid-screening when target is reached.

These cardiometabolic trial challenges are compounded by complexity that can arise during closeout, including:

1. Notification lag: Sites continue screening and randomizing in-process candidates while a closure notice is in transit.
2. Participants already in process: Sites work to responsibly complete evaluations already underway for candidates who began screening in good faith.
3. Per-participant payment structures: Can create incentives that aren’t fully aligned with a precise, coordinated closeout.
4. Under-enrollment risk tolerance: Sites and sponsors must weigh the operational risk of finishing slightly under target against completing a small number of in-process candidates.
5. Dual stop triggers (N and events): Event-driven CVOT designs can create genuine ambiguity about which trigger governs closure timing.

What’s at stake?

Scientific integrity

Uncoordinated closeout can complicate pre-specified interim analyses and stopping boundaries, so a predictable, well-communicated process protects the trial’s statistical plan.

Operational and financial planning

Coordinated closeout keeps budget-sensitive costs — imaging, central labs, CGM, drug supply for injectable therapies like GLP-1s — aligned with actual enrollment and reduces last-minute burden on site staff.

Participant protection

The core goal of a well-run closeout is protecting participants: honoring the candidates already in process, avoiding unnecessary exposure beyond scientific need, and giving candidates who won’t be enrolled clear, timely information so they can pursue other options.

Recommendations

To ensure a successful closeout, sponsors, CROs, Sites, and PIs can focus on a handful of strategies.

For Sponsors and CROs, these include:

1. Maintaining real-time enrollment dashboards rather than batch updates.
2. Using a graduated “soft close” — slot-by-slot allocation in the final stretch — rather than a single hard stop.
3. Decoupling site payment structures from raw enrollment volume where feasible.
4. Prospectively defining any enrollment flexibility — and its statistical handling — in the protocol and statistical analysis plan, tailored to the trial’s operational model.
5. Clarifying in advance which stop trigger governs closure in event-driven designs.

Sites and PIs can focus on the following:

1. Set a conservative, sponsor-agreed policy for handling participants already in process as targets approach.
2. Escalate ambiguity immediately, defaulting to pausing new consents while awaiting guidance.
3. Maintain an independent, daily-reconciled enrollment log near closure.
4. Loop in the IRB when closure affects approved study documents or planned participant communications, rather than as a routine step.

Rather than a universal ceiling, any enrollment flexibility should be prospectively defined according to each trial’s protocol, statistical plan, and operational model — and registries should report planned versus actual enrollment to support transparency and shared learning across the field.

The Bottom Line

A well-coordinated enrollment closeout is a shared achievement of sponsors, CROs, and sites working in partnership — not a race to a number. Real-time tracking, graduated closure, aligned incentives, and clearly defined stop-trigger rules protect participants and preserve data integrity while bringing enrollment to a smooth finish. Success means enrolling the right participants — safely, per protocol, with reliable data — not simply maximizing volume.