Phase 3 Randomized, Double-Blind, Placebo-Controlled Study to Evaluate Sialic Acid in Patients With Glucosamine (UDP-N-acetyl)-2-epimerase Myopathy (GNEM) or Hereditary Inclusion Body Myopathy (HIBM)

Inclusion Criteria: * Male or female, aged 18 to 55 years, inclusive * Willing and able to provide written, signed informed consent after the nature of the study has been explained, and before any research-related procedures are conducted * Have a documented diagnosis of GNEM, HIBM, distal myopathy with rimmed vacuoles (DMRV), or Nonaka disease due to previously demonstrated mutations in the gene encoding the GNE/N-acetylmannosamine kinase (MNK) enzyme (genotyping will not be conducted in this study) * Able to provide reproducible force in elbow flexors (i.e. two dynamometry force values with no more than 15% variability in the dominant arm) at Screening * Able to walk a minimum of 200 meters during the six-meter walk test (6MWT) at Screening without the use of assistive devices, including a cane, crutch(es), walker, wheelchair or scooter (ankle foot orthosis/orthoses are permitted) * Willing and able to comply with all study procedures * Participants of child-bearing potential or with partners of child-bearing potential who have not undergone a bilateral salpingo-oophorectomy and are sexually active must consent to use a highly effective method of contraception as determined by the site investigator (i.e. oral hormonal contraceptives, patch hormonal contraceptives, vaginal ring, intrauterine device, physical double-barrier methods, surgical hysterectomy, vasectomy, tubal ligation, or true abstinence \[when this is in line with the preferred and usual lifestyle of the subjec…