Safety, pharmacokinetics and sialic acid production after oral administration of N-acetylmannosamine (ManNAc) to subjects with GNE myopathy

Mol Genet Metab. 2017 Sep;122(1-2):126-134. doi: 10.1016/j.ymgme.2017.04.010. Epub 2017 Apr 26.


GNE myopathy is a rare, autosomal recessive, inborn error of sialic acid metabolism, caused by mutations in GNE, the gene encoding UDP-N-acetyl-glucosamine-2-epimerase/N-acetylmannosamine kinase. The disease manifests as an adult-onset myopathy characterized by progressive skeletal muscle weakness and atrophy. There is no medical therapy available for this debilitating disease. Hyposialylation of muscle glycoproteins likely contributes to the pathophysiology of this disease. N-acetyl-D-mannosamine (ManNAc), an uncharged monosaccharide and the first committed precursor in the sialic acid biosynthetic pathway, is a therapeutic candidate that prevents muscle weakness in the mouse model of GNE myopathy. We conducted a first-in-human, randomized, placebo-controlled, double-blind, single-ascending dose study to evaluate safety and pharmacokinetics of ManNAc in GNE myopathy subjects. Single doses of 3 and 6g of oral ManNAc were safe and well tolerated; 10g was associated with diarrhea likely due to unabsorbed ManNAc. Oral ManNAc was absorbed rapidly and exhibited a short half-life (~2.4h). Following administration of a single dose of ManNAc, there was a significant and sustained increase in plasma unconjugated free sialic acid (Neu5Ac) (Tmax of 8-11h). Neu5Ac levels remained above baseline 48h post-dose in subjects who received a dose of 6 or 10g. Given that Neu5Ac is known to have a short half-life, the prolonged elevation of Neu5Ac after a single dose of ManNAc suggests that intracellular biosynthesis of sialic acid was restored in subjects with GNE myopathy, including those homozygous for mutations in the kinase domain. Simulated plasma concentration-time profiles support a dosing regimen of 6g twice daily for future clinical trials.

Keywords: First-in-human study; GNE; GlcNAc kinase; N-acetylneuraminic acid; Pharmacokinetics; Sialylation.

Publication types

  • Clinical Trial, Phase I
  • Randomized Controlled Trial
  • Research Support, N.I.H., Intramural

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Alleles
  • Animals
  • Distal Myopathies / drug therapy*
  • Distal Myopathies / genetics
  • Distal Myopathies / physiopathology
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Female
  • Hexosamines / administration & dosage
  • Hexosamines / adverse effects*
  • Hexosamines / pharmacokinetics*
  • Homozygote
  • Humans
  • Male
  • Middle Aged
  • Muscles / drug effects
  • Muscles / metabolism
  • Mutation
  • N-Acetylneuraminic Acid / biosynthesis
  • N-Acetylneuraminic Acid / blood*
  • Phosphotransferases (Alcohol Group Acceptor) / genetics


  • Hexosamines
  • Phosphotransferases (Alcohol Group Acceptor)
  • N-acylmannosamine kinase
  • N-Acetylneuraminic Acid
  • N-acetylmannosamine

Supplementary concepts

  • Distal myopathy, Nonaka type