The FDA has extended its review of Phathom Pharmaceuticals’ new drug application (NDA) for vonoprazan, an acid-blocking drug used to treat erosive esophagitis, a severe form of acid reflux that damages the lining of the esophagus.

The agency will neither be issuing an approval nor a complete response letter by the targeted action date of Jan. 11, a company spokesperson told FDAnews.

The absence of a decision is the result of the company’s discovery of nitrosamine impurities (N-nitroso-vonoprazan) in batches of the drug. The FDA has established that 96 nanograms per day is an acceptable daily intake limit and has requested additional stability data that demonstrate nitrosamine levels in the drug remain below that limit for the proposed shelf-life of the product.

“While we are disappointed in FDA’s decision to extend the review of our NDA, we are confident we are on the path to generating the data requested,” the company said.