MFDS vs FDA: Comparing Pathways for Class II Medical Devices

Same Words, Different Systems

Both MFDS and FDA use the phrase "Class II," both run substantial-equivalence-style comparisons against predicate devices, and both require a technical file structured around safety and performance. That surface similarity hides three structural differences that catch first-time applicants in either direction: classification rule sets, technical file format, and review-clock conventions. Treating one path as a translation of the other inflates timelines by months.

Classification: Rule 11 Behaves Differently

The FDA's classification is procedure-anchored — a device is Class II largely because of how it functions and what it intends to do. Korea applies the Korean Medical Device Item Code system, where the same intended use can map to different classes depending on whether the device is "active" or "in vitro" and on whether software is a primary or accessory component.

A practical consequence: an FDA Class II AI/ML imaging device with PCCP coverage may register in Korea as Class II under the SaMD framework — but its accessory hardware can be coded separately as Class I, requiring two parallel filings rather than one. The FDA single-filing assumption breaks down here.

Technical File: 510(k) vs Korean STED

The 510(k) summary is short, predicate-anchored, and built around substantial equivalence statements with a comparison table at the core. The Korean equivalent is a STED-style technical file with full performance test reports, biocompatibility data, and clinical performance data inline — not by reference. Even if both regulators reviewed the same physical test reports, the 510(k) summary is 30 pages and the Korean dossier is 300 pages.

A common error: shipping the 510(k) summary to MFDS and assuming the underlying lab reports will be requested only on deficiency. They will not. The Korean reviewer expects the full dossier on day one and will reject for incompleteness rather than issue a request for additional information.

Review Clock: Calendar Days vs Review Days

The FDA's 510(k) clock pauses on every request for additional information (RAI). The Korean MFDS clock for Class II also pauses on supplementary requests, but it includes an administrative pre-review phase of 5–10 business days that does not exist on the FDA side. The MFDS clock often appears to start late because the file sits in administrative review before substantive review begins.

For planning purposes:

• FDA 510(k): 90 calendar days target, often 4–6 months with one or more RAIs
• MFDS Class II: 80 working days from substantive review start, often 5–8 months end-to-end including pre-review and clinical/test gap requests

Predicate vs Equivalent: A Vocabulary Trap

The 510(k) world centers on predicate devices — a single legally marketed device the new product compares against. MFDS uses equivalent product comparison, which can be a more flexible cross-reference to multiple already-approved Korean products. A single FDA-predicate comparison rarely transfers cleanly. Expect to rebuild the equivalence table with Korean reference products.

Cybersecurity Documentation: Where the Two Are Closest

This is the area with the strongest convergence. MFDS adopted cybersecurity submission requirements that closely mirror the FDA's 2023 final guidance — threat modeling, SBOM, vulnerability management plan. A well-built FDA cybersecurity submission package transfers to MFDS with translation and minor reformatting, not a rewrite. For details, see our Korea Cybersecurity 2026 Update.

When to Run Both in Parallel

Manufacturers entering both the US and Korea benefit from a shared technical file core built once and reformatted twice. The risk-management file, biocompatibility, software documentation, and verification/validation reports are reusable. Only the predicate/equivalence table and the regulatory cover sections are jurisdiction-specific.

A staged sequence — FDA first, MFDS within 90 days — also lets the Korean reviewer benefit from the FDA letter as a supporting (not equivalent) reference. The reverse sequence works less well; FDA reviewers do not credit MFDS clearance as predicate evidence.

What to Plan For

1. Two predicate tables, not one translated table.
2. Full inline test reports on the Korea side; references are not enough.
3. Two cybersecurity packets with shared technical content but jurisdiction-specific cover documents.
4. A 60-day buffer on the Korean clock for pre-review and any item-code disputes.

Leanabl runs both pathways through the Submissions service, with Korea Device Registration handling MFDS specifics and Regulatory Foundations maintaining the shared technical file core.