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# Phathom Gets 2 Complete Response Letters Over Impurity
- URL: https://www.fdaweb.com/phathom-gets-2-complete-response-letters-over-impurity/
- Published: 2023-02-10T12:00:00.000Z
- Updated: 2026-09-14T18:15:28.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5153758

FDA has issued two complete response letters to Phathom Pharmaceuticals — one for an NDA for vonoprazan for treating erosive esophagitis, and the other for a post-approval supplement for Voquezna Triple Pak (vonoprazan, amoxicillin, clarithromycin) and Voquezna Dual Pak (vonoprazan, amoxicillin). Phathom said both letters address specifications and controls for a nitrosamine drug substance-related impurity, *N*\-nitroso-vonoprazan (NVP), that was detected by the company.

“These letters formalize FDA’s request, announced by the company last month, that Phathom provide additional stability data to demonstrate that levels of the impurity previously found in vonoprazan drug product will remain at or below the daily acceptable intake throughout the proposed shelf life of the product,” the company says. “No additional deficiencies were cited by the FDA in either letter.”

Phathom says it has “conducted extensive root cause investigations” on impurity levels since it was detected and has “implemented mitigation measures to control the levels of NVP below the acceptable intake. Phathom expects to meet with the FDA in the first quarter of this year to discuss the resubmission plan and timeline that the company believes will lead to approval and launch of products containing vonoprazan.”