Mesoblast Limited (Nasdaq:MESO; ASX:MSB), global leader in allogeneic cellular medicines for inflammatory diseases, announced that it has filed for orphan drug designation (ODD) and rare pediatric disease designation (RPDD) with the United States Food and Drug Administration (FDA) for its allogeneic cell therapy Revascor^®(rexlemestrocel-L) in the treatment of the congenital heart disease hypoplastic left heart syndrome (HLHS)

HLHS is a severe congenital heart disease in which the left side of the heart does not fully develop and effective pumping of oxygenated blood by the left ventricle to the rest of the body is reduced. Without immediate surgery after birth, the prognosis is dismal with HLHS overall being responsible for 25% to 40% of all neonatal cardiac mortality.² In the longer term, surgery that creates a two-ventricle series circulation with the left ventricle (LV) pumping blood to the body and the right ventricle pumping blood to the lungs is the ideal anatomic repair. Unfortunately, achievement of this objective is limited by the inability in most patients for the left ventricle to grow sufficiently to support the circulation to the body.

REVASCOR is an allogeneic preparation of immunoselected and culture-expanded mesenchymal precursor cells which have been shown previously to have multiple mechanisms-of-action that may be beneficial to children with HLHS including neovascularization, anti-fibrosis, anti-apoptosis, immunomodulation, reduction in inflammation, and reversal of endothelial dysfunction. In the DREAM-HF randomized sham-placebo controlled prospective trial of REVASCOR in 565 adult patients with heart failure with low ejection fraction (HFrEF), a single intramyocardial administration of REVASCOR into the left ventricle resulted in significant improvement in LV ejection fraction at 12 months,³ indicative of strengthened overall LV systolic function.

In the HLHS trial a single intramyocardial administration of REVASCOR at the time of staged surgery resulted in significantly increased LV systolic and diastolic volumes over 12 months compared with control. These changes are indicative of clinically important growth of the small left ventricle that can help facilitate a subsequent surgical correction allowing for a normal two ventricle circulation. Improvement in left ventricular functional outcomes with REVASCOR may encourage more widespread use of surgical procedures to create a functioning left ventricle in children with HLHS resulting in reduction in long-term morbidity and mortality compared with other medical and/or surgical approaches.

The FDA has authority to grant orphan drug (OD) designation to a drug or biological product to prevent, diagnose or treat a rare disease or condition, defined as any disease or condition that affects less than 200,000 persons in the United States. An orphan drug designation (ODD) qualifies sponsors for incentives including tax credits for qualified clinical trials, exemption from user fees, and the potential for seven years of market exclusivity after approval. A rare pediatric disease designation (RPDD) demonstrates that the disease is serious or life-threatening and the manifestations primarily affect individuals aged from birth to 18 years, including age groups often called neonates, infants, children, and adolescents, and that the disease is a rare disease or condition.