FDA Drafts Rules for Biosimilar Autoinjectors, Syringes

FDA on 3 August 2026 released a new draft guidance telling biosimilar and interchangeable biosimilar sponsors how to prove that their prefilled syringes, autoinjector pens, and other delivery devices hold up against the reference product’s. It is a narrow document about a specific comparison, but delivery-device comparability has become one of the places a biosimilar review can stall — and the guidance fulfills a commitment FDA made to industry under the current round of biosimilar user fees.

What the guidance adds

The new document does not stand alone. FDA frames it as expanding on and clarifying recommendations the agency has already put in writing: Q.I.4 of the "Questions and Answers on Biosimilar Development and the BPCI Act" guidance (issued 20 September 2021), and the agency’s guidance on "Considerations in Demonstrating Interchangeability With a Reference Product." Both touched on delivery devices in passing. This guidance is where FDA sets out, for the first time as a standalone document, what a comparative analysis of a container closure system or device constituent part should actually contain.

That comparison is meant to run on two tracks at once: a technical one and a human-factors one. On the technical side, sponsors are expected to compare the physical characteristics of their device against the reference product’s. On the human-factors side, the guidance asks sponsors to compare the tasks a user actually performs with the device — assembling it, loading it, triggering it — along with its labeling and instructions for use. A syringe or autoinjector that looks equivalent on paper but handles differently in a patient’s hands is the scenario this section is written to catch.

Sorting differences by consequence

The guidance does not ask sponsors to eliminate every design difference from the reference product’s device — it asks them to sort the differences that exist by how much they could matter. A difference classified as minor can rest on the comparative analysis alone. A difference judged more significant needs more: additional supporting evidence beyond the comparison itself, which in practice points toward the kind of usability or human-factors data FDA's device center has long expected for combination products generally. The guidance is, in effect, importing that expectation into the biosimilar CMC review rather than leaving it to be negotiated case by case.

• Physical device comparison — characteristics of the proposed product’s container closure system or device constituent part against the reference product’s.
• User-task comparison — how a patient or caregiver actually operates the device, alongside its labeling and instructions for use.
• Difference classification — sorting design differences by potential impact on user performance and patient safety.
• CMC data — extractables and leachables studies, performance testing, and stability evaluations showing the formulation is compatible with the device.

Why the timing is a BsUFA III story

The guidance is not a freestanding policy choice; FDA is issuing it to fulfill a commitment made under the Biosimilar User Fee Act, the negotiated agreement that funds the agency’s biosimilar review program in exchange for performance goals FDA commits to hitting. Guidance documents tied to a user-fee commitment tend to arrive on a predictable cadence and carry more institutional weight than a guidance FDA issues on its own initiative — industry negotiated for this document to exist, which is part of why sponsors building device-constituent biosimilars should treat it as a preview of what a review division will actually ask for, not just a suggestion.