FDA slams door to pivotal trial for bubble boy disease gene therapy as Mustang Bio runs into another hold
Mustang Bio is in familiar territory, but that isn’t a place it necessarily wants to be.
The FDA has placed a hold on Mustang Bio’s pivitol trial for its gene therapy to treat patients with bubble boy disease, citing issues surrounding chemistry, manufacturing and controls clearance. It’s the second hold due to CMC issues the company has received in roughly 18 months.
An investigational new drug application was submitted in December 2021. If granted an IND, a Phase II study will then assess safety, tolerability and efficacy of MB-207. If approved by the FDA, the therapy would one day be eligible for a rare pediatric disease voucher.
The therapy, known as MB-207, has been previously granted orphan drug and rare pediatric disease designations. The lentiviral therapy is for those patients who have already been treated with a hematopoietic stem cell transplantation, and need more treatment.
Bubble boy disease is officially known as X-linked severe combined immunodeficiency. It’s a rare genetic disorder that occurs in 1 per 225,000 births, and is characterized by the lack of function of key immune cells. That leaves children with a severely compromised immune system, and can lead to the early death of children. Many who are affected by the disease are unable to establish T cell immunity.
Mustang was previously issued a hold for MB-107, which is currently in Phase I/II trials at St Jude, UCSF Benioff Children’s Hospital in San Francisco and Seattle Children’s Hospital in newly diagnosed infants under the age of two. In June 2021, the progress of MB-107 was delayed, but about a year ago, the hold was cleared up, and regulators allowed the Phase II trial to proceed after receiving a comprehensive package on CMC that was submitted in December 2020.
That trial enrolled 10 patients, and combined them with another 15 already treated. Then, the 25 patients will be compared with another 25 patients who “matched historical control patients who have undergone hematopoietic stem cell transplantation.” Results are expected from that in the second half of this year.
In a statement, CEO Manuel Litchman said:
In light of our positive experience managing the prior MB-107 CMC hold, and our ability to secure FDA clearance to proceed with that program, we believe that our CMC team is well positioned to address the agency’s concerns around MB-207 once additional clarification of the hold becomes available. Furthermore, we remain fully committed to the success of the pivotal Phase II MB-207 clinical trial for children with XSCID who have previously received HSCT and require re-treatment.
The news comes a little more than a month after the company joined the NASDAQ. The stock hovered around the usual dollar-and-change mark Tuesday, as it sat around $1.17 per share around 11 a.m.