Long-Term Open-Label Extension Study of Oral Levosimendan

Inclusion Criteria: * Completed a TNX-103 parent study * Investigator confirmation that participant may derive clinical benefit from continued access to TNX-103 * Requirements related to childbearing potential, contraception, and egg/sperm donation Exclusion Criteria: * Investigator or Sponsor opinion that the participant is unsuitable due to safety, inability to comply, or factors that could compromise study integrity or participant well-being * Severe hepatic impairment or cirrhosis (Child-Pugh C) or active untreated hepatitis B or C with evidence of recent infection or viral replication * Estimated glomerular filtration rate (eGFR) \< 30 mL/min/1.73 m² * Pregnancy or breastfeeding in females