How does the FDA 90-day review clock for a 510k actually work?

## How Does the FDA 90-Day 510(k) Review Clock Actually Work? For medical device sponsors, one of the most frequently discussed timelines is the FDA's 90-day review goal for a 510(k) premarket notification. However, this 90-day target represents "FDA Days"—the time the agency is actively reviewing a file—and is distinct from the total calendar time from submission to a final decision. The total time to clearance is almost always longer than 90 days because the clock can, and often does, stop. Understanding the mechanics of the 510(k) review clock is critical for accurate project planning and managing stakeholder expectations. The process is governed by specific phases and events that pause the review timeline, primarily the Refuse-to-Accept (RTA) hold and the more common Additional Information (AI) request. By dissecting how these holds function, sponsors can better anticipate the true duration of their 510(k) review and build more resilient regulatory strategies. ### Key Points * **90-Day Goal, Not a Guarantee:** The 90-day timeline is an FDA performance goal established under the Medical Device User Fee Amendments (MDUFA). It is the target for the FDA to issue a final decision, not a guaranteed date for clearance. * **"FDA Days" vs. Calendar Days:** The clock only runs when the submission is actively under review by the FDA. It stops when the FDA places the submission on hold and is waiting for information from the sponsor. * **Acceptance Review (First 15 Days):** The FDA first conducts an administrative review. If the submission is incomplete, it can be placed on a Refuse-to-Accept (RTA) hold, stopping the clock at the very beginning. * **Additional Information (AI) Holds Stop the Clock:** The most common reason for a clock-stop is an AI request during the Substantive Review phase. When the FDA issues an AI request, the 90-day clock pauses completely. * **Sponsor's Response Window:** After receiving an AI request, a sponsor typically has up to 180 calendar days to provide a complete response. If this deadline is missed, the submission is considered withdrawn. * **The Clock Resumes, It Doesn't Reset:** When a sponsor submits a complete response to an AI request, the FDA's review clock resumes from where it left off. For example, if a hold was placed on day 65, the FDA has 25 "FDA Days" remaining. * **Interactive Review is On-the-Clock:** Minor questions and clarifications, often handled via email or phone calls during the "interactive review" process, generally do not stop the clock. ### Phase 1: The Acceptance Review and the Refuse-to-Accept (RTA) Hold The 510(k) review process begins with the Acceptance Review. Within the first **15 calendar days** of receiving a submission, the FDA conducts a high-level administrative check to ensure the file is complete and formatted correctly. This is not a scientific review but a verification that all required components, as outlined in FDA guidance, are present. * **What FDA Checks:** The FDA uses a detailed checklist to confirm the presence of essential elements, such as a cover letter, device description, substantial equivalence comparison, proposed labeling, and all necessary testing data (e.g., biocompatibility, performance testing). * **If Accepted:** If the submission passes this check, the sponsor receives an acceptance letter, and the file moves into Substantive Review. The 90-day clock, which started on the day of receipt, continues to tick. * **If Placed on RTA Hold:** If the submission is found to be administratively incomplete, the FDA will issue an RTA letter detailing the deficiencies. At this point, **the 90-day review clock stops**. The sponsor has **180 calendar days** to address all the issues listed in the RTA letter and resubmit the 510(k). The review clock does not restart until the FDA receives the complete response and accepts it for review. ### Phase 2: The Substantive Review and the Additional Information (AI) Hold Once a 510(k) is accepted, it enters Substantive Review. This is the in-depth scientific and regulatory assessment where the FDA reviewer evaluates the device's substantial equivalence to a legally marketed predicate device. During this phase, the reviewer may identify questions or deficiencies that require more data or clarification from the sponsor. This leads to the most common clock-stopping event: the Additional Information (AI) request, also known as an AI hold. #### How the AI Hold Works 1. **FDA Identifies Deficiencies:** The reviewer determines that the information provided is insufficient to make a final decision on substantial equivalence. These deficiencies can range from requests for additional performance data to clarifications on the device's indications for use. 2. **AI Request is Issued:** The FDA consolidates its questions into a formal AI letter and sends it to the sponsor. The moment this letter is sent, **the 90-day review clock stops**. 3. **Sponsor Response Period:** The sponsor has up to **180 calendar days** to prepare and submit a complete response that addresses every point in the AI letter. This is the sponsor's time to conduct any necessary testing, perform analyses, or revise documentation. 4. **Consequence of Missing the Deadline:** If a sponsor fails to respond within the 180-day window, the submission is automatically considered withdrawn. The sponsor would then need to submit a brand-new 510(k), including paying any associated user fees again. #### Interactive Review vs. AI Holds Not every question from the FDA results in a formal AI hold. The FDA's 510(k) Program guidance encourages an "interactive review" process for minor issues. These are typically handled through informal communication like emails or phone calls and are intended to resolve simple questions quickly without stopping the clock. * **Interactive Review (Clock Continues):** Used for minor clarifications, typos, or easily resolved questions that do not require new data generation. * **AI Hold (Clock Stops):** Used for major deficiencies that require significant effort to address, such as new performance testing, clinical data analysis, or a substantial revision to the substantial equivalence argument. ### A Timeline Example: "FDA Days" vs. Total Calendar Days To illustrate the difference, consider a hypothetical 510(k) submission for a Class II diagnostic software device. * **Day 0:** The sponsor submits the 510(k). The 90-day FDA clock starts. * **Day 14:** The FDA completes its Acceptance Review and accepts the file. **(14 FDA Days elapsed)**. * **Day 15–70:** The submission is in Substantive Review. The FDA's lead reviewer analyzes the software validation, cybersecurity documentation, and clinical performance data. **(56 more FDA Days elapse, for a total of 70)**. * **Day 70:** The FDA determines that additional usability testing data is needed to support the proposed indications for use. They issue a formal AI request. **The FDA clock stops at 70 days.** * **Sponsor's Work (90 Days):** The sponsor takes 90 calendar days to conduct the new usability study, analyze the results, and prepare a comprehensive response. * **Day 160 (Calendar Time):** The sponsor submits the complete AI response to the FDA. **The FDA clock restarts at 70 days.** The FDA now has the remaining 20 days (90 - 70) to complete its review. * **Day 180 (Calendar Time):** The FDA completes its review and issues a substantial equivalence (SE) letter. In this scenario, the total review process took **90 FDA Days**, meeting the agency's performance goal. However, the total time from submission to clearance was **180 calendar days**. ### Strategic Considerations and the Role of Q-Submission The most effective strategy for shortening the total 510(k) review timeline is to prevent or minimize AI holds. A high-quality, comprehensive initial submission that anticipates the FDA's questions is the best way to achieve a more predictable and efficient review. This is where the Q-Submission program becomes invaluable. By engaging with the FDA through a Pre-Submission (Pre-Sub) meeting *before* finalizing testing and submitting the 510(k), sponsors can: * Align with the FDA on the choice of predicate device. * Gain feedback on proposed testing protocols (e.g., performance, biocompatibility, software validation). * Clarify regulatory requirements and confirm that the planned data will be sufficient. Addressing these critical questions upfront significantly reduces the risk of receiving a major AI request during the formal review, leading to a smoother and faster path to a final decision. ### Key FDA References - FDA Guidance: general 510(k) Program guidance on evaluating substantial equivalence. - FDA Guidance: Q-Submission Program – process for requesting feedback and meetings for medical device submissions. - 21 CFR Part 807, Subpart E – Premarket Notification Procedures (overall framework for 510(k) submissions). ## How tools like Cruxi can help Navigating the complexities of a 510(k) submission requires meticulous organization. Regulatory management platforms can help teams structure their submission narrative, manage evidence from testing, and track the completion of all required documents according to FDA checklists. By centralizing documentation and ensuring all components are included before submission, these tools can help reduce the likelihood of an administrative RTA hold and support the development of a more complete and review-ready file. This article is for general educational purposes only and is not legal, medical, or regulatory advice. For device-specific questions, sponsors should consult qualified experts and consider engaging FDA via the Q-Submission program.