Shares of Cerecor Inc. /zigman2/quotes/201368871/composite CERC -0.99% rallied 17.5% in premarket trade Wednesday, after the biotech said the U.S. Food and Drug Administration has awarded it an expedited review process for a treatment for Mannose-Phosphate Isomerase Deficiency, or MPI-CDG, a rare metabolic disorder. The FDA has granted Rockville, Md.-based Cerecor Fast Trace Designation for its CERC-802 treatment, an oral formulation of D-mannose. CERC-802 is an ultra-pure formulation of D-mannose, a naturally occurring monosaccharide that is found in animals, microorganisms, and plants, including edible fruits and herbs. "CDG patients are born with a genetic defect that hinders their ability to utilize certain monosaccharides in the production of glycoproteins," the company explained. Shares have gained 19% in 2019, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.77% has gained 16%.