The National Library of Medicine (NLM), which operates ClinicalTrials.gov, is retiring the Classic Protocol Registration and Results System (PRS) in favor of the Modernized PRS. The transition is happening in stages across 2026 and 2027, and NLM has now published concrete dates rather than a general “coming soon” notice. For clinical trial administrators, regulatory affairs staff, and anyone who registers or updates study records, this is an actionable compliance timeline, not a routine software update.
The confirmed timeline
Per NLM’s own Technical Bulletin notice on the Classic PRS phase-out and the ClinicalTrials.gov News and Updates page, three dates matter:
- July 2026 — New record creation in Classic PRS ends. Users who navigate to the classic site to register a new study are redirected to the Modernized PRS instead; Classic PRS remains usable for editing records already in progress there, but no new protocol can be started in it.
- Fall 2026 — A hard deadline: all protocol submissions must be completed in the Modernized PRS. NLM’s language is unambiguous on this point — this is not a soft preference but a stated cutoff for protocol-side work.
- 2027 (target) — The Classic PRS Results Section modules and the legacy XML upload feature are targeted for discontinuation as Modernized PRS adoption targets are met. NLM notes it will continue publishing timeline updates as this date firms up, and has separately clarified that PRS API features are expected to remain in place even as the legacy interface is retired.
Read literally, that means protocol registration moves first (by Fall 2026) and results reporting follows on a slightly longer runway (targeted for 2027). Sponsors managing both an active registration and pending results submission should not assume the same deadline applies to each.
What’s actually changing for registrants
The Modernized PRS is not a cosmetic redesign layered over the same workflow — NLM has been building it out with capability the Classic system did not have, including:
- Combined XML upload. Users can now upload a single XML file covering both the Protocol and Results Section modules, rather than handling protocol and results data separately.
- Field-level validation on Results Section modules. The Modernized PRS surfaces validation issues at the field level for results data, which is intended to make it easier for registrants to catch and fix problems before submission rather than after a Quality Control review bounce.
- A single interface going forward. Once the Fall 2026 deadline passes, protocol-side work has effectively one home. Institutions that have built internal SOPs, training material, or CTMS-integration workflows around the Classic PRS interface need those updated before that date, not after.
Action items before each deadline
For research administrators and regulatory staff responsible for a site’s or sponsor’s ClinicalTrials.gov registrations, the practical checklist is:
- Confirm which staff have active Modernized PRS accounts and access now, rather than after the redirect forces the issue. Account and role-permission migration between the two systems is not necessarily automatic for every user.
- Update internal SOPs, training materials, and any CTMS or eTMF integration documentation that references the Classic PRS workflow, screenshots, or field names — the Modernized PRS interface differs from the classic one.
- If your organization has a backlog of not-yet-submitted new protocol registrations, plan to complete them via the Modernized PRS rather than starting them in the classic interface, since new-record creation there already redirects.
- For results reporting under FDAAA 801 / the Final Rule obligations, monitor NLM’s timeline updates on the Results Section module retirement rather than assuming the 2027 target date is final — NLM has explicitly flagged it as subject to adjustment based on adoption.
- Watch the official PRS “What’s New” page and the News and Updates page directly; this is a live migration and NLM is the only authoritative source for schedule changes.
Why this matters beyond an interface swap
ClinicalTrials.gov registration and results reporting are not optional formalities for applicable clinical trials — they are statutory obligations under FDAAA 801, and NIH-funded trials carry separate reporting expectations under the NIH Policy on Dissemination of NIH-Funded Clinical Trial Information. A migration that changes where and how that reporting happens is, functionally, a change to the compliance workflow itself. Missing the Fall 2026 protocol-submission cutoff because a team was still trying to work in the Classic interface is an avoidable, entirely process-level failure — not a data or scientific one — and it is the kind of gap an institution’s clinical trials office or regulatory team can close simply by updating account access and internal documentation ahead of the deadline rather than after it.
Related CASRAI resources
- ClinicalTrials.gov — what the registry is and how it fits the broader trial-registry landscape.
- Clinical Trial Registration and Reporting Compliance — the FDAAA 801 / Final Rule obligations this migration sits inside.
- How to Write a Research Protocol for IRB Submission
- Designing a Clinical Trial: Endpoints, Sample Size, Randomization, SAP
Sources
NLM Technical Bulletin, Phasing Out the Classic PRS: Timeline, Features, and User Support, May-June 2026, nlm.nih.gov/pubs/techbull/mj26/mj26_ctg_prs.html. ClinicalTrials.gov, News and Updates. Protocol Registration and Results System, What’s New.
