Mesenchymal stem cells
The US Food and Drug Administration (FDA) has granted fast track designation to a mesenchymal stem cell (MSC) product, MSC-100-IV, as a treatment for children with steroid-refractory acute graft-vs-host disease (aGVHD).
MSC-100-IV consists of human MSCs derived from donor bone marrow and expanded in culture.
Fast track designation has the potential to shorten the time to FDA approval for MSC-100-IV through priority review, which reduces the FDA review process from 10 months to 6 months.
The designation also allows for a rolling review process, whereby completed sections of the Biologics License Application can be submitted for FDA review as they become available, instead of waiting for all sections to be completed.
In addition, fast track designation provides product developers with opportunities for more frequent meetings and written communications with the FDA.
MSC-100-IV is being developed by Mesoblast Limited in partnership with Mallinckrodt Pharmaceuticals.
Trial results
The application for fast track designation for MSC-100-IV was supported by a trial of 241 pediatric patients with steroid-refractory aGVHD. Results from this trial were presented at the 2016 BMT Tandem Meetings.
Patients initially received 2 million MSCs/kg twice a week for 4 weeks, at least 3 days apart. If they achieved a partial or mixed response (improvement in one organ with deterioration in another) at the day-28 assessment, patients then received 2 million MSCs/kg once a week for 4 weeks.
The patients received a total of 2434 infusions—a median of 11 (range, 1-24)—and had a median treatment duration of 46 days (range, 1-186).
Fifty-seven percent of patients (n=138) had at least 1 serious adverse event. About 5% (n=11) were considered treatment-related, and 1.7% (n=4) led to study discontinuation. There was 1 infusion reaction.
The overall response rate at day 28 was 65%, and the complete response rate was 14%. Responses were observed for all aGVHD grades and did not differ by baseline organ involvement.
Day 100 survival was significantly better in children who achieved a response at day 28—82%, compared to 39% for non-responders (P<0.0001).
In November 2016, Mesoblast reported success in an ongoing, phase 3 registration trial of MSC-100-IV in 60 children with steroid-refractory aGVHD.
The company said the trial was successful in a pre-specified interim futility analysis using the primary endpoint of day-28 overall response. Enrollment in this trial is expected to be complete in mid-2017.
