Acer Therapeutics & Relief Therapeutics Announce FDA Acceptance for Filing of NDA

Acer Therapeutics Inc. and its collaboration partner, Relief Therapeutics Holding SA recently announced the US FDA has accepted for filing the New Drug Application (NDA) for ACER-001 (sodium phenylbutyrate) for the treatment of patients with Urea Cycle Disorders (UCDs). The FDA has assigned a Prescription Drug User Fee Act (PDUFA) target action date of June 5, 2022.

Acer’s 505(b)(2) NDA is supported by results from two previously announced bioequivalence (BE) trials in which ACER-001 showed similar relative bioavailability for both phenylbutyrate (PBA) and phenylacetate (PAA), the active metabolite of sodium phenylbutyrate, compared to the reference listed drug, 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, Chief Executive Officer 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.”

Jack Weinstein, Chief Financial Officer and Treasurer of Relief, added “Our collaboration with Acer is thriving, and we are pleased with the progress they have made in advancing ACER-001. In parallel with Acer’s activities, we continue to execute on our global commercial strategy for ACER-001 which includes our intended submission of a Marketing Authorization Application (MAA) for the treatment of patients with UCDs in Europe in Q2/Q3 2022.”

Parties interested in the ACER-001 program for UCDs may sign up for updates at:

ACER-001 is an investigational product candidate which has not been approved by FDA, the European Medicines Agency (EMA), or any other regulatory authority. There is no guarantee that this product candidate will receive regulatory authority approval in any territory or become commercially available for the indications under investigation.

UCDs are a group of disorders caused by genetic mutations that result in a deficiency in one of the six enzymes that catalyze the urea cycle, which can lead to an excess accumulation of ammonia in the bloodstream, a condition known as hyperammonemia. Acute hyperammonemia can cause lethargy, somnolence, coma, and multi-organ failure, while chronic hyperammonemia can lead to headaches, confusion, lethargy, failure to thrive, behavioral changes, and learning and cognitive deficits. Common symptoms of both acute and chronic hyperammonemia also include seizures and psychiatric symptoms. The current treatment of patients with UCDs consists of dietary management to limit ammonia production in conjunction with medications that provide alternative pathways for the removal of ammonia from the bloodstream. Some patients may also require individual branched-chain amino acid supplementation.

Current medical treatments for patients with UCDs include nitrogen scavengers, RAVICTI and BUPHENYL, in which the active pharmaceutical ingredients are glycerol phenylbutyrate and sodium phenylbutyrate, respectively. According to a 2016 study by Shchelochkov et al., published in Molecular Genetics and Metabolism Reports, while nitrogen scavenging medications have been shown to be effective in helping to manage ammonia levels in some patients with UCDs, non-compliance with treatment is common. Reasons referenced for non-compliance associated with some available medications include unpleasant taste, frequency with which medication must be taken, required number of pills, and the high cost of the medication.

ACER-001 (sodium phenylbutyrate) is being developed for the treatment of various inborn errors of metabolism, including UCDs and Maple Syrup Urine Disease (MSUD). ACER-001 is a nitrogen-binding agent in development for use as adjunctive therapy in the chronic management of patients with UCDs involving deficiencies of carbamylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), or argininosuccinic acid synthetase (AS). The formulation is a multi-particulate dosage formulation for oral administration consisting of a core center, a layer of active drug, and a taste-masked coating designed to avoid the bitter taste of sodium phenylbutyrate in the mouth while quickly dissolving in the low pH of the stomach. Acer is also being developed for MSUD and has been granted orphan drug designation by the FDA for this indication. ACER-001 is an investigational product candidate which has not been approved by FDA, the European Medicines Agency (EMA), or any other regulatory authority.

Acer is a pharmaceutical company focused on the acquisition, development, and commercialization of therapies for serious rare and life-threatening diseases with significant unmet medical needs. Acer’s pipeline includes four programs: ACER-001 (sodium phenylbutyrate) for treatment of various inborn errors of metabolism, including urea cycle disorders (UCDs) and Maple Syrup Urine Disease (MSUD); ACER-801 (osanetant) for treatment of induced Vasomotor Symptoms (iVMS); EDSIVO™ (celiprolol) for treatment of vascular Ehlers-Danlos syndrome (vEDS) in patients with a confirmed type III collagen (COL3A1) mutation; and ACER-2820 (emetine), a host-directed therapy against a variety of infectious diseases, including COVID-19. Each of Acer’s product candidates is believed to present a comparatively de-risked profile, having one or more of a favorable safety profile, clinical proof-of-concept data, mechanistic differentiation and/or accelerated paths for development through specific programs and procedures established by the FDA. In March 2021, Acer entered into a Collaboration and License Agreement with Relief for development and commercialization of ACER-001. For more information, visit

Relief Therapeutics focuses primarily on clinical-stage programs based on molecules with a history of clinical testing and use in human patients or a strong scientific rationale. Relief’s lead drug candidate RLF-100 (aviptadil), a synthetic form of Vasoactive Intestinal Peptide (VIP), is in late-stage clinical testing in the US for the treatment of respiratory deficiency due to COVID-19. As part of its pipeline diversification strategy, in March 2021, Relief entered into a Collaboration and License Agreement with Acer Therapeutics for development and commercialization of ACER-001. ACER-001 is a taste-masked and immediate release proprietary powder formulation of sodium phenylbutyrate (NaPB) for the treatment of Urea Cycle Disorders and Maple Syrup Urine Disease. In addition, Relief’s recently completed acquisitions of APR Applied Pharma Research SA and AdVita Lifescience GmbH, bring to Relief a diverse pipeline of marketed and development-stage programs, a commercial infrastructure in selected European countries and an internal, R&D capability, which Relief hopes to leverage for both internal pipeline products as well as for third party product development on a fee for service basis. For more information, visit