RELIEF THERAPEUTICS Holding SA and its collaboration partner, Acer Therapeutics Inc. announced that the European Commission has granted orphan medicinal product designation in the EU to ACER-001 (sodium phenylbutyrate) for the potential treatment of patients with Maple Syrup Urine Disease (MSUD). ACER-001 was granted orphan drug designation by the U.S. Food and Drug Administration (FDA) in the U.S. for MSUD in 2014. Orphan drug designation is granted to medicines that treat or prevent a life-threatening or chronically debilitating rare disease, with a prevalence in the EU of not more than 5 in 10,000, and with either no currently approved method of prevention or treatment, or with significant benefit to those affected by the disease. The designation potentially provides certain benefits to ACER-001, including the potential for up to 10-year EU market exclusivity upon regulatory approval, if received, reductions in EMA application fees, and access to study protocol assistance. Multiple investigational trials evaluating sodium phenylbutyrate in urea cycle disorder (UCD) patients suggest treatment with sodium phenylbutyrate is associated with selective reduction in branched chain amino acids (BCAA) despite adequate restricted dietary protein intake.1,2,3,4 Analysis of data from a longitudinal multicenter study of 553 UCD patients treated with sodium phenylbutyrate demonstrated that sodium phenylbutyrate decreased plasma BCAA in patients with UCDs and could serve as a therapy in maple syrup urine disease and other common complex disorders with dysregulation of BCAA metabolism. Based on this clinical observation, investigators at Baylor College of Medicine explored the potential of sodium phenylbutyrate treatment to lower BCAA and corresponding branched-chain a-ketoacid (BCKA) levels in both healthy subjects and patients with MSUD. The investigators found that sodium phenylbutyrate, when dosed over three days, showed a statistically significant reduction of leucine in all three healthy subjects and in three out of the five MSUD patients who participated in the trial. In November 2020, study results evaluating the effect of sodium phenylbutyrate in the management of acute metabolic decompensation in pediatric MSUD patients (n=10) were published by investigators from Istanbul University-Cerrahpasa Medical Faculty in the peer-reviewed Journal of Pediatric Endocrinology and Metabolism showing a significant reduction in leucine levels in MSUD patients experiencing an acute attack.6 The results suggested that sodium phenylbutyrate could be safely administered in combination with emergency protocol using other active pharmaceuticals and supports additional investigation of potential clinical benefit beyond emergency protocol alone.