Mesoblast Ltd. said the U.S. Food and Drug Administration agreed to a rolling review of the company's biologics license application for stem cell therapy remestemcel-L.

The application was based on a late-stage study that evaluated remestemcel-L in treating acute graft versus host disease, or aGVHD, in 55 children who do not respond to standard steroid therapy. Mesoblast said 89% of these patients had grade C/D aGVHD, the most severe form of the disease.

AGVHD is a life-threatening complication of an allogeneic bone marrow transplant, or when the stem cells come from another person. In the more severe forms of the disease, Grades C/D or III/IV, six-month mortality rates are as high as 90%.

The study met its main goal at day 28, during which 69% of the patients enrolled in the study had survived, compared to the historical control rate of 45%. The survival rate at day 180 was 79%.

The rolling review of the company's application will enable individual components to be submitted and reviewed on an ongoing basis rather than waiting for all sections to be completed.

The Australian biotechnology company plans to seek priority review for remestemcel-L from the FDA, which granted the therapy fast-track status in 2017.