Mesoblast receives coveted FDA designation for Revascor heart treatment

Cellular medicines developer Mesoblast (ASX: MSB) is celebrating the granting of new US Food and Drug Administration (FDA) approval for its Revascor heart disease treatment.

The FDA has granted its highly-sought rare pediatric disease (RPD) designation for Revascor following submission of results from a randomised, controlled trial in children with hypoplastic left heart syndrome (HLHS).

HLHS is a severe congenital and potentially life-threatening heart disease in which the left side of the heart does not fully develop and effective pumping of oxygenated blood by the left ventricle (LV) to the rest of the body is reduced.

The FDA only grants RPD designation to certain serious or life-threatening diseases which primarily affect children.

Its approval of a biologics licensing application for Revascor for the treatment of HLHS means Mesoblast may be eligible to receive the valuable priority review voucher that can be redeemed for any subsequent marketing application or may be sold or transferred to a third party.

HLHS trial success

The HLHS trial in 2023 was conducted in the US on 19 children with HLHS via a single intramyocardial administration of Revascor at the time of staged surgery.

The trial resulted in the desired outcome of significantly larger increases in LV end-systolic and end-diastolic volumes over 12 months.

The changes observed are considered indicative of clinically-important growth of the small LV, facilitating the ability to have a successful surgical correction known as full biventricular (BiV) conversion.

Without full BiV conversion, which allows for a normal two-ventricle circulation with the surgically repaired left ventricle taking over circulatory support to the body, the right heart chamber is under excessive strain with increased risk of heart failure and death.

Mesoblast chief executive Silviu Itescu said it had been assessed that 100% of Revascor-treated children – compared with 57% of the control group – had large enough LVs to accommodate the full BiV conversion.

This suggests that Mesoblast’s treatment may help increase the ability to ‘better grow’ the HLHS LV after LV-recruitment surgery.

Results from the blinded, randomised and placebo-controlled prospective trial were published in the December 2023 issue of the peer-reviewed Journal of Thoracic and Cardiovascular Surgery Open.

Life-saving surgery

“Given the impressive enlargement of the left chamber we have seen in these children treated with Revascor in the […] trial and the increased ability to successfully accomplish life-saving surgery, we plan to meet with [the] FDA to discuss the potential for this trial to support accelerated approval in this indication,” Mr Itescu said.

Without immediate surgery after birth, the prognosis is dismal with HLHS being responsible for 25% to 40% of all neonatal cardiac mortality.

In the longer term, surgery that creates a two-ventricle series circulation with the 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 an inability in most patients for the LV to grow sufficiently to support proper circulation to the body.