A Basket Clinical Study to Assess Glycerol Tributyrate in Patients With Mitochondrial Encephalopathy, Lactic Acidosis, Stroke-like Episodes (MELAS) or Leber's Hereditary Optic Neuropathy-Plus (LHON-Plus)

Participants will be administered orally three times a day enteric hard capsules containing 500 mg of glycerol tributyrate with an 8-ounce glass of water on an empty stomach: morning, noon, and evening during the dose-escalation phase. Each MELAS participant will undergo a six-month dose escalation phase of glycerol tributyrate, starting at a dose of 1,000 mg (tid) per day during the first month followed by a monthly increase of 500 mg (tid) per dose of glycerol tributyrate with the maximal oral dose of glycerol tributyrate 3,500 mg (tid) per dose at the end of six-month-long dose escalation phase. Once the participant-specific fixed maximum tolerated dose (MTD) is determined, MELAS participants will take an oral administration of this MTD three times a day during the 12-month-long clinical phase.