Least burdensome changes the ask, not the bar.

“Just argue least burdensome” gets said in submission strategy meetings the way “just ask for an extension” gets said about deadlines — as if the phrase itself were a lever. It is a real statutory term, and it does real work. It does not do the work most people reach for it to do.

What the statute actually constrains

Section 513(i)(1)(D) of the FD&C Act (21 U.S.C. 360c(i)(1)(D)) governs what FDA may ask for in a 510(k) review of a device with differing technological characteristics from its predicate:

“Whenever the Secretary requests information to demonstrate that devices with differing technological characteristics are substantially equivalent, the Secretary shall only request information that is necessary… In making such request, the Secretary shall consider the least burdensome means of demonstrating substantial equivalence and request information accordingly.”

The parallel provision for PMAs — Section 515(c)(5) (21 U.S.C. 360e(c)(5)) — binds FDA the same way when it requests additional information toward a reasonable-assurance-of-safety-and-effectiveness finding. Both provisions constrain a request. Neither touches the finding it supports. The statute says so itself, in nearly identical language attached to each: nothing in the 510(k) provision alters the standard for determining substantial equivalence, and nothing in the PMA provision “alters the standards for premarket approval of a device.” That sentence is not guidance color. It is in the law, next to the least-burdensome instruction, on purpose.

Three statutes built the current version

“Least burdensome” entered the FD&C Act in 1997, through Section 205 of the FDA Modernization Act (Public Law 105-115) — language about collaborative determinations of device data requirements, aimed at early-stage disagreements over what a device would need to show. FDASIA revisited it in 2012: Section 602, titled “Clarification of Least Burdensome Standard,” is where Congress went back in and pinned down what “necessary” means — the minimum information that would support the determination in question, not the minimum information a sponsor would prefer to supply. The 21st Century Cures Act added an institutional layer in 2016: Section 3058 required every CDRH reviewer working premarket submissions to be trained on what least burdensome means, required the CDRH Ombudsman to audit that training within eighteen months and interview industry about their actual experience of it, and required FDA to publish the findings and report them to Congress. Congress treated inconsistent application as a compliance problem worth auditing, not a phrase worth leaving to interpretation.

The argument that actually works

A least-burdensome argument that holds up names the specific determination FDA is trying to reach — substantial equivalence on a particular technological characteristic, or reasonable assurance for a particular condition of use — and shows that a smaller or different dataset reaches it. “This bench test is sufficient because it addresses the same failure mode as the requested clinical data” is a least-burdensome argument. “A full study would be expensive and slow” is not one; it never touches what the statute actually asks FDA to consider. The provision aims at the request, not the reviewer’s sympathy.

The practice

Treat least burdensome as a targeting question, not a closing argument: for each piece of information a reviewer asks for, what determination does it actually feed, and does a lighter version of it still feed that determination completely? That question gets answered against your own device and your own file — the accepted-evidence record for a comparable clearance is not public, and FDA Radar’s clearance data stops at what FDA discloses: K-number, applicant, product code, and decision, not the underlying submission. This is regulatory intelligence and method, never regulatory advice about what a specific reviewer will accept from a specific file; that argument gets built by the regulatory professional who has to defend it.