The Food and Drug Administration (FDA) has accepted for filing the New Drug Application for ACER-001 (sodium phenylbutyrate) for the treatment of patients with urea cycle disorders.

ACER-001, a nitrogen-binding agent, is a powder formulation of sodium phenylbutyrate designed using a microencapsulation process. The product consists of a core center, a layer of active drug, and a taste-masked coating that quickly dissolves in the stomach allowing for rapid systemic release. 

The investigational treatment is being developed for use as adjunctive therapy in the chronic management of urea cycle disorders involving deficiencies of carbamylphosphate synthetase, ornithine transcarbamylase, or argininosuccinic acid synthetase.

The application is supported by data from 2 bioequivalence trials, which showed similar relative bioavailability for both phenylbutyrate and phenylacetate when compared with Buphenyl (sodium phenylbutyrate).

“With FDA commencing a substantive review of our NDA, ACER-001 is one step closer to potentially providing an alternative treatment option for patients with UCDs,” said Chris Schelling, CEO and Founder of Acer. “We look forward to working with the FDA during their review of our application. In addition, we continue to collaborate with our partners to ensure we are well positioned to support a successful commercial launch of ACER-001, subject to FDA approval.”

A Prescription Drug User Fee target date of June 5, 2022 has been set for the application.


  1. Acer Therapeutics and Relief Therapeutics announce FDA acceptance for Filing of New Drug Application for ACER-001 to treat urea cycle disorders. News release. Acer Therapeutics Inc. and RELIEF THERAPEUTICS. Accessed October 6, 2021.
  2. Acer Therapeutics announces topline results from its bioequivalence trial of ACER-001 compared to Buphenyl® under fed conditions. News release. Acer Therapeutics Inc. February 11, 2021. Accessed October 6, 2021.