The PMA clock starts at the last module

A modular Premarket Approval Application sounds like it should make a review start sooner — file the parts you have ready, keep working on the rest, let FDA get a head start. Read the guidance and the regulation together, and the opposite is closer to true. Nothing about a modular PMA is filed, in the sense that starts FDA’s statutory clock, until the single module that finishes it arrives.

A shell, then modules, then one application

FDA’s modular review guidance — finalized January 13, 2025, and since that revision available to Humanitarian Device Exemptions as well as PMAs — lets a sponsor and FDA agree in advance on a shell: an outline naming each module the application will eventually contain and what each one will hold. That shell gets an informal look from FDA to confirm modular review even fits the device before anything is submitted under it. From there, modules arrive over time, and FDA reviews each as it comes in against its own clock. None of that is a Refuse to Accept or Refuse to File review, because none of it is a PMA yet — it is pieces of one, arriving on a schedule both sides agreed to.

The application starts existing when the last piece does

21 CFR 814.42 governs filing a PMA, and a modular submission only reaches that section once the final module is in hand. That receipt is the moment FDA converts the accumulated modules into a single original application and runs the acceptance and filing review that every other PMA gets at the start, not partway through. The filing date the agency assigns is the date of the last module, full stop — not the date the shell was agreed, not the date the first module went in, not an average or a midpoint across however many modules a given device needed.

That filing date is the one 21 CFR 814.40 and 21 U.S.C. § 360e(d) both build on. FDA’s statutory 180-day period to act on a PMA — approval order, approvable letter, not approvable letter, or denial — runs from the date of filing. A modular application that spent a year in productive, module-by-module review with FDA has, procedurally, not started that clock for one day of it. The 180 days begin when the last module does, exactly like an ordinary, unmodular PMA that showed up complete on day one.

Where the confusion actually costs something

The trap is not misunderstanding modular review’s existence. It is treating a year of module-by-module engagement as review time already spent, and expecting the 180-day clock to reflect that. It doesn’t, and the guidance does not restructure21 CFR 814.40 to say otherwise — the modules change how the content of the application gets assembled and reviewed piece by piece; they do not change what “filed” means or when it happens. A sponsor tracking a modular PMA’s timeline against an internal launch date needs the actual filing date FDA assigned at the last module, not the date the shell negotiation finished or the date the first module was accepted.

The practice

Confirm the filing date directly rather than inferring it from when module submissions began. FDA Radar’s own pipeline has nothing to offer here either way: its four sources are Federal Register notices, 510(k) clearances, device recalls, and CDRH warning letters — no PMA or HDE feed at all, modular or otherwise. A shell agreement, a module receipt, and the eventual filing date of a modular application never reach this product, or most monitoring built the same way. That timeline belongs to the sponsor and FDA, tracked directly, for as long as it takes the last module to arrive. This is a description of how modular review’s clock is structured, never regulatory advice about when a specific application will, or should, be filed.