Ataluren for Nonsense Mutation Methylmalonic Acidemia

Major Inclusion Criteria: * Ability to provide written informed consent (parental/guardian consent if applicable)/assent (if applicable) * Age ≥2 years * Phenotypic evidence of methylmalonic acidemia (MMA) based on the presence of characteristic clinical symptoms or signs and an elevated plasma MMacid level (\>0.27 micromole/liter (umol/L) * Presence of a nonsense mutation in at least 1 allele of the mutase (mut), Cobalamin A (cblA), or Cobalamin B (cblB) gene * Glomerular filtration rate ≥30 milliliters (mL)/minutes/1.73 meters squared (m\^2), serum aminotransferase values ≤2.5\*the upper limit of normal, serum bilirubin ≤1.5\*the upper limit of normal, plasma adrenocorticotropic (ACTH) within normal limits * Willingness and ability to comply with scheduled visits, drug administration plan, study restrictions, and study procedures Major Exclusion Criteria: * Known hypersensitivity to any of the ingredients or excipients of the study drug * Any change in chronic treatment for MMA within 2 months prior to start of screening laboratory assessments * Episode of metabolic decompensation within 1 month prior to start of Screening laboratory assessments * History of organ transplantation * Ongoing dialysis for renal dysfunction