FDA issues action letters on both tirzepatide KwikPen applications

Newly posted FDA approval letters confirm that the agency issued action letters on the same day — January 29, 2025 — for both of Eli Lilly's tirzepatide KwikPen applications: the Mounjaro KwikPen supplement (NDA 215866/S-009) and the Zepbound KwikPen supplement (NDA 217806/S-002) ^[1][2]. Lilly did not submit amendments that "constituted a complete response" to those letters until December 2, 2025, according to both approval letters ^[1][2].

The timeline in the documents is unusually long for a device-and-labeling supplement. Lilly filed the Mounjaro KwikPen supplement on September 28, 2023 ^[2] and the Zepbound KwikPen supplement on November 15, 2023 ^[1]. FDA acted on both in January 2025, and the final approvals were signed by Lisa B. Yanoff, MD, Deputy Director of the Office of Cardiology, Hematology, Endocrinology, and Nephrology, on January 20, 2026 ^[1][2]. That puts roughly 10 months between the January 2025 action letters and Lilly's complete responses, and more than two years between the original filings and approval.

What the KwikPen actually is

Both supplements cover the same change: "six presentations" of the KwikPen, each containing 4 doses of a fixed volume of tirzepatide formulation for once-weekly administration ^[1][2]. Tirzepatide is the molecule in both Mounjaro (type 2 diabetes) and Zepbound. Until now, the US presentations described in the letters have been single-dose pens and vials — the Zepbound single-dose pen Instructions for Use was previously approved November 8, 2023, its single-dose vial IFU on March 28, 2024, and a multi-dose vial IFU on January 7, 2026 ^[1]. For Mounjaro, the single-dose pen IFU dates to May 13, 2022, with a multi-dose vial IFU also approved January 7, 2026 ^[2].

The approvals also cover revisions to the Prescribing Information, Medication Guide, and new carton and container labeling for each product ^[1][2]. FDA asked Lilly to make one small wording change on cartons: revise "mg/dose" to "mg per dose" "for improved clarity" ^[1][2].

What the letters do not say is why FDA issued the January 2025 action letters in the first place. The approval letters reference the action letters only in passing and give no reason, no deficiency list, and no indication of whether the issues involved manufacturing, the device, or labeling ^[1][2]. Lilly's public explanation, if any, is not in these documents. Both products are regulated as "Part 3 combination products" — drug plus delivery device — and are subject to combination-product postmarketing safety reporting ^[1][2], which is the category where device and manufacturing questions typically arise, but the sources do not attribute the delay to any specific cause.

Why it matters for patients

A four-dose pen changes the physical logistics of a weekly injection. Instead of four separate single-dose pens per month, a KwikPen holds four doses of a fixed volume in one device ^[1][2]. For people using tirzepatide, that can mean less packaging, different refrigerator space needs, and different Instructions for Use to learn — the approval letters list a separate KwikPen IFU alongside the existing single-dose pen, single-dose vial, and multi-dose vial instructions ^[1][2].

The delay also means this presentation was not available in the US for about a year longer than it otherwise might have been. The sources do not say anything about pricing, insurance coverage, launch dates, or whether the KwikPen will replace or sit alongside existing pens and vials. They also do not address supply. Those questions are not answered in the FDA correspondence.

One technical note from the letters: because this supplement was not for a new active ingredient, new indication, new dosage form, new dosing regimen, or new route of administration, FDA determined Lilly was exempt from the pediatric assessment requirement under the Pediatric Research Equity Act ^[1][2].

What happens next

Under the approval letters, Lilly had 14 days from January 20, 2026 to submit the content of labeling in structured product labeling format, and up to 30 days after printing to submit final printed carton and container labeling ^[1][2]. Any patent information for the Orange Book was due within 30 days of approval ^[1][2]. The letters do not state when the KwikPens will reach US pharmacies.