Rexlemestrocel-L for children with HLHS receives Orphan-Drug Designation


The Orphan Drug Designation follows the receipt of Rare Pediatric Disease Designation from the FDA in January 2024.

Rexlemestrocel-L for children with HLHS receives Orphan-Drug Designation| Image Credit: © Araki Illustrations - © Araki Illustrations -

Rexlemestrocel-L for children with HLHS receives Orphan-Drug Designation| Image Credit: © Araki Illustrations - © Araki Illustrations -

The FDA has granted an Orphan-Drug Designation (ODD) to rexlemestrocel-L (Revascor; Mesoblast Limted) after positive data from a randomized controlled trial in children with hypoplastic left heart syndrome (HLHS).

The Orphan designation follows the Rare Pediatric Disease Designation rexlemestrocel-L received in January 2024.

The potentially life-threatening HLHS is a severe congenital heart condition in which the left side of the heart does not fully develop, reducing effective pumping efforts by the left ventricle to deliver oxygenated blood to the rest of the body.

HLHS is responsible for 25% to 40% of neonatal cardiac mortality without immediate surgery after birth, according to a press release from Mesoblast Limited.

Rexlemestrocel-L 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," the company stated in the press release.

A trial published in a December 2023 edition of The The Journal of Thoracic and Cardiovascular Surgery Open (JTCVS Open) highlighted 19 children with HLHS.

A single intramyocardial administration of rexlemestrocel-L at the time of staged surgery resulted in significantly larger increases in the left ventricular (LV) end-systolic and end-diastolic volumes over 12 months compared to controls measured by 3D echocardiography (P = 0.009 and P = 0.020, respectively), stated Mesoblast.

The growth of the small ventricle facilitated the ability to have a successful surgical correction (full biventricular conversion), allowing for a normal 2 ventricle circulation, with the surgically repaired left ventricle taking over circulatory support to the body.

"The fact that 100% of [rexlemestrocel-L]-treated children compared with 57% of controls had large enough LVs to accommodate the full BiV conversion suggests that [rexlemestrocel-L] treatment may help increase the ability to ‘better grow’ the HLHS LV after LV recruitment surgery," the press release stated as noted in the published trial.

Orphan Drug Designation provides orphan status to drugs and biologics are defined as those intended for safe and effective treatment, diagnosis or prevention of rare disease/disorders that impact fewer than 200,000 people in the United States.


United States Food & Drug Administration (FDA) grants Mesoblast Orphan-Drug Designation for Revascor (rexlemestrocel-L) in children with congenital heart disease. Mesoblast Limited. Press release. February 14, 2024. Accessed February 15, 2024.

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