ACER-001 for Urea Cycle Disorders (UCDs)


ACER-001 is a fully taste-masked, immediate-release formulation of sodium phenylbutyrate (NaPB) developed using a microencapsulation process. NaPB has been found to help control blood ammonia levels in conjunction with a restricted diet for people with a urea cycle disorder (UCD).1,2 However, non-compliance with treatment is common. Reasons given for non-compliance include the unpleasant taste associated with available medications, the frequency with which medication must be taken and the high cost of the medication.

For the treatment of UCD, NaPB is a prodrug that metabolizes quickly to become phenylacetate. Phenylacetate then binds to glutamine via acetylation to become phenylacetylglutamine. Phenylacetylglutamine is similar to urea in that it contains two moles of nitrogen and is excreted by the kidneys. Through this process, NaPB is an alternate way to excrete excessive nitrogen created by ineffective processing of ammonia during the urea cycle.3

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We believe that if ACER-001 is approved, its taste-masked properties will make it a compelling alternative to existing NaPB-based treatments, as the unpleasant taste associated with NaPB is cited as a major impediment to patient compliance with those treatments.4  In February 2020, we reported the successful completion and final data from Part B of our pivotal trial evaluating the bioavailability and bioequivalence of ACER-001 to BUPHENYL® (sodium phenylbutyrate). Consistent with observations from Part A of the trial, data from Part B showed ACER-001 to be bioequivalent to BUPHENYL® and were within the parameters recommended by the FDA’s Guidance for Industry, “Statistical Approaches to Establishing Bioequivalence.” The ACER-001 trial design consisted of two parts. Part A was a single-center, single-blind, randomized, single-dose crossover trial designed to evaluate the relative bioavailability of three different oral suspension formulations of ACER-001 compared to BUPHENYL® in 20 healthy adult subjects. Results from Part A of the trial, along with results from a concurrent taste assessment trial evaluating palatability of the three formulations of ACER-001 compared to BUPHENYL®, informed Acer’s selection of the single, optimal formulation of ACER-001 that was evaluated in Part B. Part B of this trial was a single-center, single-blind, randomized, single-dose crossover study designed to show bioequivalence of ACER-001 compared to BUPHENYL® in 36 healthy adult subjects. As described above, results from Part B were announced in February 2020. Also, we expect to finalize the design and size of a taste study comparing the optimal formulation of ACER-001 to BUPHENYL® and begin enrollment in the second half of 2020. The design and size of the study will be determined following further discussions with the FDA. Results of this study are not required for NDA submission.

We intend to initially seek FDA approval to market ACER-001 in the U.S. using a regulatory pathway established under section 505(b)(2) of the Federal Food, Drug and Cosmetic Act that allows applicants to rely at least in part on third party data for approval, which may expedite the preparation, submission, and approval of a marketing application. We anticipate submitting to the FDA the 505(b)(2) NDA for ACER-001 for the treatment of UCD in early 2021, assuming successful completion of nonclinical work and 12-month stability data. NDA submission is subject to our ability to generate sufficient capital resources to fund this program.


  1. Ah Mew N, Lanpher BC, Gropman A, Chapman KA, al. e. Urea cycle disorders overview. Gene Reviews. Seattle, Washington: University of Washington, Seattle; 1993.
  2. Sirrs SM, et al. Barriers to Transplantation in Adults with Inborn Errors of Metabolism. JIMD Rep. 2013;8:139-144.
  3. Brusilow SW, Maestri NE. Urea cycle disorders: diagnosis, pathophysiology, and therapy. Adv Pediatr. 1996;43:127-170.
  4. Shchelochkov OA,et al. Barriers to drug adherence in the treatment of urea cycle disorders: Assessment of patient, caregiver and provider perspectives. Mol Genet Metab. 2016;8:43-47.